Background: As a critical industrial gas, the global oxygen market is projected to reach $48 billion/year within this decade. Meanwhile, oxygen production is highly energy intensive due to the limited efficiency of the commercial cryogenic air separation technology. With a pressing demand for emission and energy reduction, there is an urgent need to intensify the air separation technology and to increase the separation efficiency. Chemical looping air separation (CLAS), a cyclic redox scheme that relies on a metal oxide for oxygen storage and release, offers a potentially promising route for oxygen production at a higher thermal efficiency [1-4]. In this method, a dual reactor system is considered, where a reduced metal oxide is placed in an oxidizing environment, such as air. Then, once oxidized, the material is transitioned to a reducer, where it is subjected to lower oxygen partial pressure under steam purge or vacuum for oxygen release. The PO2 and/or temperature swing between the reduction and oxidation step is what drives the separation.

Results: CLAS has high potential to produce oxygen at a lower energy penalty and competitive price, however further work needs to establish process parameters and develop advanced oxygen sorbent materials. Using ASPEN, a CLAS system design and a process model were established. The process model estimates a base case CLAS energy consumption of 0.66 MJ/kg O2. This represents a 15% decrease compared to cryogenic air separation (0.78 MJ/kg O2). This study also highlights the importance of developing advanced sorbents with suitable redox thermodynamics and fast redox kinetics for further improvements in efficiency and economic attractiveness. To do this, we used high throughput Density Functional Theory (DFT) simulation and Machine Learning (ML) to anticipate 1,270 perovskite oxides suitable for CLAS based on their Gibbs Free Energy change for oxygen release. Though many of these predicted materials proved to have superior redox performances, an interesting class of materials, known as high entropy oxides had the best performance. Characterization and testing of these materials has shown unique characteristics, including entropy driven stability of our main phase.

Conclusions: The CLAS process has significant potential to replace current state of the art systems. Thoroughly investigating process parameters associated with plant design leads to a need for more systematic design of oxygen sorbents tailored for this application. The systematic approach of combining ML and DFT calculations with experimental oxygen vacancy results from this study provides an effective strategy for developing improved sorbents for thermochemical air separation.

References:

1. Imtiaz, Q.; Hosseini, D.; Müller, C. R. Energy Technology 2013, 1 (11), 633–647.
2. Aoki, Y.; Kuroda, J. Am. Chem. Soc. 2017, 139 (32), 11197–11206. https://doi.org/10.1021/jacs.7b05429.
3. Motohashi, T.; Hirano, Y.; Masubuchi,. Chem. Mater. 2013, 25 (3), 372–377.
4. Bulfin, B.; Vieten, J.; Agrafiotis, C.; Roeb, M.; Sattler, C. Journal of Materials Chemistry A 2017, 5 (36),
   18951–18

Background: The perovskite-structured calcium manganite family (CaxA1-xMnyB1-yO3-δ) has been demonstrated as one of the promising materials in chemical looping applications, such as chemical looping air separation (CLAS) and chemical looping-oxidative dehydrogenation (CL-ODH) [1]-[3]. The complex redox behaviors of the CaMnO3 family offer significant versatility and thus understanding the effect of dopants on the redox thermodynamics and kinetics of CaMnO3 family oxygen carriers are important from both scientific and practical standpoints. In this work, the thermodynamic properties of an oxygen-deficient B-site ordered perovskite oxide, Ca2MnAlO5+δ, were investigated to improve oxides and optimize the redox processes.

Results: The thermodynamic properties of Ca2MnAlO5+δ were systematically investigated via thermal gravimetric analysis (TGA) for its potential application in CLAS. TPD results revealed that the initial oxygen releasing temperature is approximately 350 °C in an inert environment. The total oxygen releasing capacity is around 2.80 wt.% with most of the oxygen being released between 450-600 °C. The oxygen non-stoichiometry (δ) of Ca2MnAlO5+δ was determined in the range of 440-600 oC and oxygen partial pressures between 0.01-0.8 atm. The values of the partial molar enthalpy and entropy for the oxygen releasing reaction obtained from the van’t Hoff equation were relatively constant across the entire operating temperature and PO2 ranges, with average values of 146.5 ± 4.7 kJ/mol O2 and 162.7 ± 5.1 J/K mol O2 respectively. The experimentally measured non-stoichiometry (δ) was modeled as a function of temperature and oxygen partial pressure using a point defect model. Two fitting regions, determined by the predicted equilibrium P-T curve, were applied and both gave satisfactory fitting qualities. Equilibrium constants for selected defect reactions as well as the molar enthalpy and entropy for each reaction were derived. The selected model is sufficient to describe the defect structure of Ca2MnAlO5+δ, as evidenced by the comparable values of molar enthalpy and entropy calculated from the model and the van’t Hoff equation. The defect model also provides reasonable predictions under higher oxygen partial pressures ranging from 1.1-4 atm.

Conclusions: The combined studies on the oxygen non-stoichiometry and the defect structure of Ca2MnAlO5+δ offer insights for further design and development of the oxygen sorbent in the context of CLAS.

References:

1. Dudek, R. B., Gao, Y., Zhang, J., Li, F. (2018). Manganese-containing redox catalysts for selective hydrogen combustion under a cyclic redox scheme. AIChE Journal, 64(8), 3141–3150.
2. Motohashi, T., Hirano, Y., Masubuchi, Y., Oshima, K., Setoyama, T., Kikkawa, S. (2013). Oxygen Storage Capability of Brownmillerite-type Ca2AlMnO5+δ and Its Application to Oxygen Enrichment. Chemistry of Materials, 25(3), 372–377.
3. Tian, Y., Dudek, R. B., Westmoreland, P. R., Li, F. (2020). Effect of Sodium Tungstate Promoter on the Reduction Kinetics of CaMn0.9Fe0.1O3 for Chemical Looping – Oxidative Dehydrogenation of Ethane. Chemical Engineering Journal. 398(15), 125583.

Background: The study of crystal nucleation poses major challenges for both experimental and simulation studies. The stochastic nature of nucleation, combined with its uncanny ability to amplify the effect of minute molecular-level details, make it very difficult to achieve consistent experimental results even for simple systems. Molecular simulation studies are also challenging, as nucleation is a rare event with a free energy barrier that includes a substantial entropic contribution36. Additionally, some of the common assumptions in molecular simulations, such as periodic boundary conditions (which can result in serious finite size artifacts) and constant number of molecules, can greatly bias the results. Most simulation studies of crystal nucleation use order parameters to describe the structure of the crystal, while overlooking the structure of the solvent.

Results: We obtained order parameters for four different solvents (acetonitrile, ethanol, methanol and water) containing urea at five different concentrations. The behavior of each solvent in the nucleation process has a direct correlation with its nucleation mechanism (i.e. one- or two-step mechanism), showing that we could predict the behavior and/or pathway using the solvent physical and thermodynamic properties. Additionally, these results can be extended to other solutes in the drug discovery industry.

Conclusions: We show some of the first studies that uses solvent order parameters to predict the behavior of the nucleation of crystals in solution. Consequently, we could generalize this procedure to other liquid structures, which will enable us to generate order parameters for any solvent of interest.

Background: Ethane oxidative dehydrogenation and ethylene oligomerization (EO) in conjunction have the potential to convert ethane in remote natural gas wells to fungible liquid fuels[1]. Ni-Beta zeolites have been identified as efficient heterogeneous EO catalysts, and isolated Ni(II) ions in exchange positions are generally accepted to be active sites [2]. BrØnsted acid sites (BAS) may also play a role in the catalysis. To elucidate the impact of catalyst preparation and cation composition on EO performance, Ni-Beta catalysts were prepared by ion exchange of H-Beta, NH4-Beta, and Na-Beta zeolites with Ni(II) ions in aqueous solution followed by drying and calcination in air at 500-550oC. In addition, to suppress BAS formation from proton exchange, a second Ni-Na-Beta catalyst was prepared by co-exchange of Na-Beta with Ni(II) and a large excess of Na+. The resultant catalysts were characterized by H2 temperature-programmed reduction (TPR), NH3 temperature-programmed desorption (TPD) and CO diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and tested for EO activity and product selectivity at 225°C and 10 bar.

Results: Reversible hydrolysis of framework Al (FAL) sites in H-Beta reduces overall ion exchange capacity; thus, higher Ni loadings were achieved by exchange of NH4-Beta and Na-Beta zeolites. TPR profiles of all Ni-Beta catalysts contain peaks at 350 and 550 oC that are assigned to NiO and isolated Ni(II) ions in exchange positions, respectively. In addition, catalysts prepared by ion exchange of H-Beta exhibited sharp TPR peaks at 450 oC that we assign to [Ni(II)-OH]+ species. CO DRIFT spectra indicate that Ni(II) ions occupy the distinct β (FAL pair in the same six-membered ring) and γ (FAL pair in opposite six-membered rings) exchange sites. Typically, ~70% of the Ni(II) resides in the β position. NH3 TPD demonstrated the presence of strong BAS and highly electrophilic Ni(II) ions in the Ni-H-Beta catalysts. The Ni-Na-Beta catalyst prepared by simple ion exchange of Na-Beta contained BAS; however, Ni-Na-Beta prepared by co- exchange with Na+ had negligible BrØnsted acidity. Catalysts prepared by exchange of NH4-Beta and Na-Beta had greater EO conversion than the catalyst prepared by exchange of H-Beta, primarily because of their higher Ni loadings. DRIFT spectra in the v(OH) region confirm the presence of BAS in these catalysts. The Ni-Na-Beta catalyst prepared by co-exchange had a lower Ni loading and correspondingly lower EO conversion; however, this catalyst had no detectible BAS. This catalyst also gave very low yields of isobutene and odd carbon number oligomers consistent with the suppression of acid-catalyzed side reactions.

Conclusions: Ni-Beta catalysts prepared by Ni(II) exchange of NH4-Beta and Na-Beta exhibit higher EO conversion when compared Ni-H-Beta catalyst prepared by the literature standard procedure using H-Beta. An active Ni-Na-Beta catalyst was demonstrated evidencing, for the first time, that BAS are not required to form the EO active site.

References:

1. L. Neal, V. Haribal, J. Mccaig, H. H. Lamb, F. Li, J. Adv. Manuf. Process. 2019, 1, e10015.
2. A. Martinez, M. A. Arribas, P. Concepcion, S. Moussa, Appl. Catal. A. 2013, 467, 509.Li, Zheng, Tao Yu, Rajesh Paul et al. (2020). Agricultural Nanodiagnostics for Plant Diseases: Recent Advances and Challenges. Nanoscale Adv. 2, 3083-3094.

Background: Sweat is an important biofluid for monitoring individuals’ health as it contains a number of essential biomarkers. However, sampling sweat for analysis remains challenging as most of the commercially available sweat sensing devices are either invasive or operate only under active perspiration. These devices fail to function under low-sweating conditions and are incapable of deriving sweat measurements from subjects at rest. We demonstrate a new principle for the design of flexible and wearable devices, which are capable of extracting sweat under both sedentary and actively perspiring conditions using osmotic pressure difference for pumping, and evaporation for liquid disposal [1,2]. The device is constructed of silicone, polyacrylamide hydrogel patch, and paper microfluidic conduit with a site of evaporation at the end (evaporation pad). The hydrogel is equilibrated with glycerin, glucose, or NaCl solution to build up the desired osmotic strength.

Results: In-vitro testing with gelatin-based model skin platform has initially revealed that both glucose and glycerin treated hydrogels facilitate high dye (model biomarker in model skin) accumulation on the evaporation pad, with glucose being the highest. Human trials with devices fitted with glucose hydrogel have shown the potential of the prototype to extract sweat containing lactate under both resting and non-resting (during exercise) conditions within a period 2 hours. Results reveal the following two observations: (1) sweat lactate is a function of the physiological state of the body, which increases with exercise and (2) the correlation between blood and sweat lactate concentration also depends on the physiological state of the body. Further, we discovered that integration of a “glycerogel” (hydrogel treated with pure glycerin) hosted patch with microneedles have the potential to also sample model biomarker from model skin. Such an arrangement is essential for long-term interstitial fluid (ISF) sampling since ISF glucose levels correlate well with that in blood. A prototype of continuous sweat lactate sensing platform is also currently being developed by using enzymatic electrochemical sensors on a polyimide film, positioned in between the hydrogel and the paper microfluidic channel. Initial testing with this integrated platform has shown that this wearable prototype can detect the dynamic change in sweat lactate levels during both rest and exercising conditions.

Conclusions: We introduce a novel simple, low cost, continuous sweat sampling wearable platform with specific sensors that can analyze numerous biomarkers and reveal a throve of health information. We are presently expanding our prototype to a lateral flow assay (LFA) platform and working towards utilizing it for early disease diagnosis from sweat.

References:

1. Shay, T., Saha, T., Dickey, M. D. & Velev, O. D. Principles of long-term fluids handling in paper-based wearables with capillary-evaporative transport (2020). Biomicrofluidics 14(034112), 1-9.
2. Saha, T., Fang, J., Mukherjee, S., Dickey, M. D. & Velev, O. D. Wearable Osmotic-Capillary Patch for Prolonged Sweat Harvesting and Sensing (2021). ACS Appl. Mater. Interfaces, 13(7), 8071-8081.

Background: Origami, the Japanese art of paper folding, allows complex 3D systems to be produced from flat starting materials, such as robots [1]. Origami folding allows for compact storage [2] and can endow new functionality such as reconfigurability [3] or improved mechanical properties [4]. Despite these advantages, origami 3D electronics remain sparse owing to the manual folding steps required [5]. Self-folding methods have been developed [1] but these methods rely on responsive polymers that are poor electrical conductors. Metal self-folding techniques have been developed [6] but only laser forming works in ambient conditions at multiple length scales. Laser forming is the process of using photothermally produced stresses to generate plastic deformations in a substrate. To date, laser forming has not been demonstrated on metal/polymer bilayers such as flex PCBs.

Results: Successful laser cutting and self-folding of flexible printed circuit boards (PCBs) was demonstrated and the folding process was characterized. The high reflectivity of copper (~99%) was modulated by two methods: using the laser to first drive surface oxidation or using a nickel/gold coating as an absorbing layer. This allows low-power settings to be used when folding and prevents cutting through the thin copper traces. Further testing revealed the forces generated during laser forming are enough to lift surface mount electronic devices. A common timing circuit was then fabricated, populated with surface mount devices, cut, and laser self-folding while maintaining electrical connectivity.

Conclusions: Flex PCBs can be cut and self-folded using a single, low-cost (~$10k) laser system. Lasers are already used in PCB manufacturing and this work demonstrates another potential function—self-folding. Thus, this study paves the way for rapid prototyping of 3D electronics.

References:

1. Felton, Samuel, Michael Tolley, Erik Demaine, Daniela Rus, and Robert Wood (2014). A method for building self-folding machines, Science, 345: 644-646.
2. Zirbel, Shannon A., Robert J. Lang, Mark W. Thomson, Deborah A. Sigel, Phillip E. Walkemeyer, Brian P. Trease, Spencer P. Magleby, and Larry L. Howell (2013). Accommodating Thickness in Origami-Based Deployable Arrays. J. Mech. Des., 135: 111005.
3. Liu, Xueli, Sun Yao, Benjamin S. Cook, Manos M. Tentzeris, and Stravos V. Georgakopoulos (2015). An Origami Reconfigurable Axial-Mode Bifilar Helical Antenna, IEEE Trans. Antennas Propag., 63: 5897-5903.
4. Hubbard, Amber M., Jay Kalpesh Patel, Sigurd Wagner, Chih-Hao Chang, Jan Genzer, and Michael D. Dickey (2021). Stiff or Extensible in Seconds: Light-Induced Corregations in Thin Polymer Sheets, Adv. Mater. Technol., 6: 2000789.
5. Sterman, Yoav, Erik D. Demaine, and Neri Oxman (2013). PCB Origami: A Material-Based Design Approach to Computer-Aided Foldable Electronic Devices. J. Mech. Des., 135: 114502
6. Lazarus, Nathan, Gabriel L. Smith, and Michael D. Dickey (2019). Self-Folding Metal Origami, Adv. Intell. Syst., 1: 1900059

Background: Photolithography has been used for electronic manufacturing to obtain complex nanostructured circuits. As the feature size becomes stringent, i.e. less than 5-10 nm, extreme UV (EUV) lithography has been addressed. However, inherent stochastics leading to feature misalignment as well as extremely high cost seem to be problematic. Area-selective deposition (ASD) is regarded as a promising technique, where the target films can be grown up only in predetermined regions on a starting patterned surface. This bottom-up approach is generally proceeded by atomic layer deposition (ALD), molecular layer deposition (MLD), and chemical vapor deposition (CVD). In particular, ASD of polymers via MLD process plays a pivotal role in nucleation inhibitors, low-k deposition, and air-gap materials. This work describes a simple, rapid and effective method to achieve inherent ASD of poly(3,4-etheyelendioxythiophene) (PEDOT) on silicon coated with thermal silicon oxide (SiO2) vs hydrogen-terminated silicon (Si-H) via MLD and CVD processes.

Results: PEDOT deposition was conducted by using 3,4-etheyelendioxythiophene (EDOT) as a reactive monomer and antimony pentachloride (SbCl5) as an oxidant using vapor phase oxidative polymerization at 100 oC. The growth was performed in the isothermal viscous-flow reactor and the chemical sources were delivered with N2 carrier gas. In order to investigate PEDOT selectivity, film thickness on blanket SiO2 and Si-H surfaces was measured by spectroscopic ellipsometry (SE) and x-ray photoelectron spectroscopy (XPS), indicating 15 nm of PEDOT growth was only grown on SiO2 relative to Si-H. Systematic studies were carried out to understand reactant doses and growth temperature effects on growth rate and film selectivity. Based on this understanding, ~10 nm of selective PEDOT deposition was demonstrated on SiO2/Si line/spacer patterned wafers and the results were compared with results on blanket substrates. To improve PEDOT ASD, CVD was employed and the nucleation model was used to quantify the selectivity between MLD and CVD. The mechanism of PEDOT growth delay on Si-H can be explained by the selective SbCl5 reaction on Si-H surfaces.

Conclusions: This work shows ASD of PEDOT polymerization on SiO2 vs Si-H surfaces by vacuum-based MLD and CVD. By understanding the chemical reaction on different surfaces (SiO2 and Si-H), preferential PEDOT growth can be achieved, and the selectivity was further enhanced by adjusting the growth condition. PEDOT ASD was demonstrated on SiO2/Si-H patterned wafers. The origin of selectivity was due to the selective SbCl5 reaction on Si-H. Overall, the results illustrate feasible ASD of PEDOT on nanoscaled patterned substrates, expanding the range of materials for bottom-up patterning.

Background: Fabrics have been functionalized with hydrogel microparticles (henceforth, “microgels”) for advanced filtration [1], wound dressing, sensing, and controlled delivery applications [2]. By tailoring the chemical makeup of these microgels, stimuli-responsiveness can be incorporated to fabricate “smart” fabrics that respond to external stimuli. In this work, we developed self-repairing and smart gating fabrics using dual-stimuli responsive microgel solutions.

Results: In the first study, we developed a dual-responsive colloidal microgel to repair nonwoven fabrics and recover their native morphological and functional properties. The proposed method of repair comprises (i) topical application of dual-responsive poly(N-isopropyl acrylamide) (PNIPAm) microgels via drop-casting onto the damaged membrane, (ii) magnetic congregation of the magnetic microgels at the pinhole tears, followed by (iii) cross-linking with UV light. The wound healing mechanism inspired this approach, wherein circulating platelets gather at the damaged site of a severed blood vessel and are glued by fibrin to form a plug. The formulation was employed to repair micron-sized damages in polypropylene (PP) and polybutylene terephthalate (PBT) membranes and recover their native morphological, functional, and mechanical properties [3]. We also developed fabrics with light-controlled permeability. The membrane fibers were coated with thermo-responsive PNIPAm-microgels impregnated with graphene oxide nanoparticles. The membranes’ permeability was controlled by local heating generated by the graphene oxide nanoparticles upon exposure to near-infrared light. The flux of salt solute across the membranes was controlled reversibly with (i) higher flux at temperatures higher than the lower critical solution temperature (LCST, where the hydrogel layer collapses and opens the pore space), (ii) reduced flux at temperatures lower than LCST (where the hydrogel layer expands and fills the pore space). The increasing content of graphene oxide on the membrane corresponded to pronounced local heating of the fabric.

Conclusions: The studies presented represent two multi-responsive microgel systems that can be utilized to fabricate (i) self-repairing and (ii) dynamic gating fabrics. The uniqueness of these microgel systems enables substrate-agnostic incorporations in nonwovens irrespective of their chemical composition. These microgel systems can provide a powerful tool to incorporate “smart” stimuli-responsive behavior in otherwise non-functional membranes.

References:

1. C. Cutright et al., (2021) J. Membr. Sci., 616, 118439.
2. C. Cutright et al., (2021) Adv. Funct. Mater., 2104164.
3. S. Ramesh et al., (2021) ACS Appl. Polym. Mater., 3, 1508.

Background: Wearable electronics have attracted great attention over the past decade due to their potential applications in health care and human-machine interfaces. Next generation wearable technology demands compatible energy sources that are soft, stretchable, and sustainable. Efforts have been made to develop energy harvesters that can convert human motion/ambient mechanical energy to electrical energy.[1-4] Triboelectric and piezoelectric harvesters are prominently used to convert mechanical energy to electrical energy.[1-4] Triboelectric harvesters have gained great popularity due to their relatively straightforward fabrication. They induce electrical current based on contact electrification (rubbing two surfaces) and electrostatic induction (oscillating the distance between charged surfaces).[1,3-5] Thus, they require moisture-free environments to enable contact electrification.[1,3-5] Piezoelectric harvesters, in contrast, require extensive fabrication techniques and loss in energy conversion when converted to flexible devices, as their fundamental materials are intrinsically hard and brittle.[1-3]

Results:

In this work, we use liquid metal and hydrogel to fabricate soft variable area electrical double layer (EDL) capacitors (~40 μF cm-2). When two EDL capacitors are connected by an electrolyte medium, varying one of the EDL capacitors’ area generates a driving force for charge movement through an external circuit. These devices generate a power density of ~2 mW m-2 per fractional change in area. We have characterized the behavior of these devices as a function of a variety of parameters including material properties and physical deformation. The devices behave as expected and the response of the devices to deformation match a physics-based model. This approach does not need an external power supply to generate charge and it can work under various modes of deformation such as pressing, stretching, bending, and twisting.

Conclusions: The liquid metal based soft device generates electrical signal when deformed, which may be useful for energy harvesting as well as self-powered sensors. These devices can be used to monitor human activities thereby find many applications in wearable electronics, and healthcare systems like rehabilitation and prosthetics. The ability of the harvester to operate underwater shows promising applications in underwater sensing, and blue energy harvesting.

References:

1. Zhou, M. et al. A review on heat and mechanical energy harvesting from human – Principles, prototypes and perspectives. Renewable and Sustainable Energy Reviews 82, 3582–3609 (2018).
2. Sim, H. J. et al. Stretchable and Weavable Piezoelectric. Advanced Engineering Materials 17, 1270–1275 (2015).
3. Yang, Y. et al. Liquid-Metal-Based Super-Stretchable and Structure-Designable Triboelectric Nanogenerator for Wearable Electronics. ACS Nano 12, 2027–2034 (2018).
4. Gao, S. et al. Wearable high-dielectric-constant polymers with core–shell liquid metal inclusions for biomechanical energy harvesting and a self-powered user interface. Journal of Materials Chemistry A 7, 7109–7117 (2019).
5. Wang, Z. L., Jiang, T. & Xu, L. Toward the blue energy dream by triboelectric nanogenerator networks. Nano Energy 39, 9–23 (2017).

Background: We will discuss the colloidal principles behind the development of new multiphasic 3D printing inks consisting of water, crosslinked polydimethyl siloxane (PDMS) microbeads and liquid PDMS phase. These thixotropic Homocomposite Capillary Pastes (HCPs) developed in our group can be directly extruded and shaped on a 3D printer [1,2]. The Homocomposite Capillary Pastes for 3D Printing (HCP-3DP) are physical gels made by bridging a colloidal dispersion of silicone microbeads in water with uncured liquid silicone precursor. The resulting paste is in a pendular state where the bridging material preferentially wets the microbeads.

Results: The PDMS microbeads in the dispersed phase are synthesized by a shear driven emulsification of liquid precursor in a secondary continuous phase. The size of these microbeads can be controlled by manipulating the emulsification shear rate. Additionally, we have been able to embed controlled volumes of neodymium-based magnetic microparticles into the microbeads during their synthesis, enabling their magnetic field-driven manipulation. By adding a small volume fraction of liquid polymer precursor to the microbead suspension, menisci form between the dispersed microparticles, binding the microbeads by a strong capillary force. The curing of the PDMS bridges after extrusion yields remarkably elastic and flexible structures. We will report how the volume of the bridging liquid can be controlled to result in a solid with programmable void fraction and controllable extensional modulus after curing. Our preliminary data show that the 3D- printed swimmers can be used as probes to quantify the interfacial rheology of liquids with adsorbed species along the liquid/air interface. By floating the magnetic swimmers on phosphate buffered saline solution of IgG protein and subjecting them to external magnetic field, their actuation pattern can be corelated to the interfacial viscosity of the adsorbed IgG layer.

Conclusions: The novel capillary force-mediated 3D printing method makes possible the fabrication of soft architectures that reconfigure in magnetic fields and could find a broad range of applications, including microtools for interfacial rheology studies. HCP-3DP inks described here are biocompatible and enable new opportunities for making of “active” and reconfigurable structures. We will show that with optimal magnetic material loading into the colloidal silicone microbeads, optimal volume of liquid polymer precursor used to bridge them and controlled level of polymer crosslinking, we can fabricate 3D printed structures which are very soft, yet strong enough to withstand repeated cycles of expansion and contraction when actuated by external magnetic fields. The cyclic actuation of these objects can be modulated to mimic the pumping mechanism like that seen in heart and lung muscles. This opens possibilities for future applications as bioscaffolds for heart or lung tissues with improved cell viability.

References:

1. Roh, S., Parekh, D.P., Bharti, B., Stoyanov, S.D. and Velev, O.D. (2017). 3D Printing by Multiphase Silicone/Water Capillary Inks. Adv. Mater., 29:1701554.
2. Roh, S., Okello, L.B., Golbasi, N., Hankwitz, J.P., Liu, J. A.-C., Tracy, J.B., Velev, O.D. (2019). 3D‐Printed Silicone Soft Architectures with Programmed Magneto‐Capillary Reconfiguration. Adv. Mater. Technol., 4:1800528.

Background: Atomic and molecular layer deposition are layer-by-layer thin film synthesis techniques used prevalently in microelectronics and energy storage due to their sub-nanometer thickness and conformality control. Recent research has focused on exploiting chemical differences on the starting surface to selectively deposit material on one desired region without affecting an adjacent region. This area-selective deposition (ASD) enables a bottom-up, self-aligning nanopattern, where higher selectivity indicates a better quality and higher resolution pattern. High selectivity processes are essential for reducing the burden on expensive and complex electronic manufacturing steps, such as lithography. [1] Consider titanium oxide (TiO2), which is useful in lithography and solar cells due to its high etch resistance and refractive index. [2] While several nanometers of selective TiO2 patterning is possible, further improvement towards commercial requirements is hindered by incomplete understanding on how pattern loss occurs. Herein we demonstrate how deepening this understanding enables improved TiO2 selectivity.

Results: Baseline selectivity is determined by comparing TiO2 growth on silicon oxide (SiO2) with and without a chemical passivation layer. In this standard process, the desired growth region (non-passivated SiO2) has 3.8 nm TiO2 while the non-desired growth region (passivated SiO2) is limited to <0.2 nm, corresponding to 90% selectivity. Undesired TiO2 particles on the passivated surface were analyzed with scanning electron microscopy (SEM) to gain insight on how and when these particles formed, e.g. via defect sites, adsorption, or diffusion of TiOx species. Particle size distributions reveal a broad range of particle sizes and a high concentration of small particles even after depositing relatively thick films, when larger particles would be expected. This indicates that undesired particle nucleation sites are generated during processing, which is further supported by kinetic modeling. To reduce the impact of nucleation site generation, we develop a defect mitigation strategy to periodically etch small particles and then re-passivate the surface. The resultant three-step [passivation + deposition + etch] supercycle process is evaluated on 90 nm wide 3D patterns of passivated pillars (no growth desired) and non-passivated trenches (growth is desired). This supercycle process results in significant reduction of undesired TiO2 content and pattern roughness on the passivated pillars, while still enabling substantial (7 nm) TiO2 deposition on the desired growth surface. These results correspond to a ~200% increase in selectivity compared to the baseline process.

Conclusions: We leverage insight from mechanistic analysis on TiO2 patterning to develop a strategy that significantly improves selectivity. This process is promising for enhancing lithography and other nanoelectronic material applications. Overall, this work demonstrates the importance of mechanistic understanding towards advancing thin film applications.

References:

1. Parsons, Gregory N., and Rob D. Clark (2020). Area-Selective Deposition: Fundamentals, Applications, and Future Outlook. Chem. Mater. 32: 4920–4953.
2. Soethoudt, Job, et. al. (2020). Insight into Selective Surface Reactions of Dimethylamino-trimethylsilane for Area-Selective Deposition of Metal, Nitride, and Oxide. J. Phys. Chem. C. 124: 7163–7173.

Background: In bacteria, complex phenotypes can be accessed via adaptive evolution5,9,10 or iterative genome-wide expression perturbation screens (e.g. asRNA[1], and CRISPRi/a[2]). One downside of adaptive evolution is the accumulation of genomic hitchhiker mutations, a feature that is particularly troublesome for biosensor-coupled screens and that makes learning from these experiments very time-consuming. For asRNA and CRISPRi/a, the researcher is limited to sampling changes to expression space, rather than the much larger space of protein bioactivity. For these reasons, directed evolution is useful because it directs mutations to defined DNA sequences and samples a much wider sequence space. However, due to the limited length of DNA that can be evolved using most methods, it has been difficult to apply directed evolution to complex phenotypes.

Results: To enable directed evolution of complex phenotypes encoded by multigene pathways, we require large library sizes for DNA sequences >5-10kb in length, elimination of genomic hitchhiker mutations, and decoupling of diversification and screening steps. To meet these challenges, we developed Inducible Directed Evolution (IDE), which uses a temperate bacteriophage to package large plasmids and transfer them to naive cells after intracellular mutagenesis. To demonstrate IDE, we evolved a 5-gene pathway from Bacillus licheniformis that accelerates tagatose catabolism in Escherichia coli, resulting in clones with 65% shorter lag times during growth on tagatose after only two rounds of evolution.

Conclusions:

As microbial engineering moves toward applications demanding ever-higher performance (e.g. green production of fuels and chemicals sensing and biosynthesis on host- associated sites[3]), the ability to engineer complex phenotypes is becoming increasingly important. Currently, optimizing the performance of multi-gene pathways is a challenging task. IDE offers the ability to perform directed evolution on long (at least up to 42 kbp) sequences of DNA with tunable error rates (up to 5.4*10−6 substitutions per bp per generation) and library sizes that scale trivially with culture volume (up to 4% of recipient cells contain mutants). We expect that the use of different mutagenesis methods (e.g. ultraviolet light and chemical mutagens) in place of a mutagenesis plasmid can add further mutational flexibility. Importantly, the use of temperate phages (such as P1) to passage variants to fresh hosts greatly reduces the impact of off-target mutations and decouples mutagenesis and screening steps, providing a large degree of flexibility when designing selections.

References:

1. Georg, J. & Hess, W. R. cis-antisense RNA, another level of gene regulation in bacteria. Microbiol. Mol. Biol. Rev. 75, 286–300 (2011).
2. Bikard, D., Hatoum-Aslan, A., Mucida, D. & Marraffini, L. A. CRISPR interference can prevent natural transformation and virulence acquisition during in vivo bacterial infection. Cell Host Microbe 12, 177– 186 (2012).
3. Beller, H. R., Lee, T. S. & Katz, L. Natural products as biofuels and bio-based chemicals: fatty acids and isoprenoids. Nat. Prod. Rep. 32, 1508–1526 (2015)

Background: The genus Caldicellulosiruptor consists of extremely thermophilic, Gram-positive, fermentative anaerobic bacteria (Topt > 70oC), typically isolated from terrestrial thermal features. All species with available genome sequence information to date degrade hemicellulose, whereas only a subset degrades microcrystalline cellulose. Caldicellulosiruptor species physically associate with the substrate during growth on the plant biomass. One mechanism for this association is through multi-domain hemicellulases, which are anchored to the cell surface through S-layer homology (SLH) domains. Engineered strain of C. bescii in which an SLH-domain hemicellulase from C. kronotskyensis was inserted bound more tightly to certain xylan substrates [1]. These bacteria also deploy novel carbohydrate binding proteins called tāpirins [2], which are encoded in proximity to the region of the genome referred to the Glucan Degradation Locus (GDL), which contains up to six multi-domain cellulases. Tāpirins specifically interact with microcrystalline cellulose to various extents [3].

Results: Six hemicellulase-encoding genes from all Caldicellulosiruptor species were produced recombinantly, biochemically characterized, and engineered strains of C. bescii in which each gene was inserted were created. Previously, engineered strains of C. bescii in which a Calkro_0402 from C. kronotskyensis was inserted bound more tightly to certain xylans [1]. The results shown here explored four uncharacterized enzymes in Caldicellulosiruptor species which could help improve plant biomass solubilization. Tāpirins were first discovered in our lab, however their plant carbohydrate binding mechanism remains unclear. The tāpirin (Calkro_0844) from C. kronotskyensis has a cellulose binding affinity comparable to family 3 carbohydrate binding modules (CBM3). The tāpirins from C. hydrothermalis (Calhy_0908) and C. kristjianssonii (Calkr_0826) bind to cellulose more than other tāpirins, although these species are not cellulose degraders. Furthermore, C. bescii mutants lacking the tāpirin genes did not bind to the cellulose.

Conclusions: Discussed here are current efforts to engineer the surface of C. bescii to improve its capacity for biomass degradation. This includes inserting genes for non-native SLH-domain hemicellulases from other Caldicellulosiruptor species into the C. bescii genome. Furthermore, we are investigating the tāpirin cellulose binding mechanism through site-directed mutations in Calhy_0908, Calkr_0826, and Calkro_0844 in which cysteine residues are being inserted to strategically enable disulfide bridges within the protein to form. Our goal is to assess the significance of flexibility in hydrophobic binding pocket in the tāpirins as this relates to cellulose binding affinity.

References:

1. Conway, J.M.; et al (2016), Multidomain, surface layer-associated glycoside hydrolases contribute to plant polysaccharide degradation by Caldicellulosiruptor species. J of Biol Chem, 291(13): p. 6732-6747.
2. Blumer-Schuette, S.E.; et al. (2015), Discrete and structurally unique proteins (tāpirins) mediate attachment of extremely thermophilic Caldicellulosiruptor species to cellulose. J of Biol Chem, 290(17): p. 10645-10656.
3. Lee, L.L.; et al (2019), Comparative Biochemical and Structural Analysis of Novel Cellulose Binding Proteins (Tāpirins) from Extremely Thermophilic Caldicellulosiruptor Species. J Appl Environ Microbiol, 85(3): p. 01983-18.

Background: Dynamic molecular changes in medium spiny neurons (MSN) of the striatum underlie brain diseases including drug addiction. Many of these molecular mechanisms have been well established in rodent brains. Studies of human embryonic stem cell derived (hESC) models of MSNs have also been performed [1]. However, the focus of these studies has been on obtaining appropriate cellular markers of MSN of the striatum. Few investigations have explored the molecular dynamics of human MSNs in response to perturbations of interest due to ethical limitations and experimental tractability. We propose a hESC-derived model of MSNs that can be perturbed and analyzed with molecular precision. The work presented here highlights the early potential for developing a reductionist approach to complement rodent work in dissecting human molecular mechanisms related to the striatum and addiction.

Results: Transcriptional responses of hESC-derived MSNs after dopamine exposure resemble rodent transcriptional responses to dopamine, specifically the upregulation of immediate early genes (e.g., FOS, JUNB, ARC, NR4A1, EGR1), and others (e.g., GADD45B) [2,3]. cAMP- related pathways (i.e., Dopamine-DARPP32 feedback in cAMP signaling, cAMP-mediated signaling) are downregulated after an acute dopamine dose potentially showcasing diminished cAMP response normally seen after D1 agonist stimulation. Differentially expressed genes (DEG) of acute dopamine dosed hESC-derived MSN overlap more with DEG of acute dopamine dosed rodent MSN (49%) than they do with acute cocaine dosed rodent MSN (19%) [3]. This may be indicative of a partial recapitulation of in vivo responses to drugs of abuse in hESC- derived MSNs. This is also evident from the differential activation of pathways not specific to MSN responses to dopamine (stress response pathways and cholesterol biosynthesis pathways) after chronic dopamine dosage. However, gene desensitization, a molecular phenotype typically seen after chronic drugs of abuse, is seen in chronic dopamine dosed samples.

Conclusions: hESC-derived MSN responses to dopamine mimic transcriptional responses seen in rodent model systems. Ingenuity pathway analysis highlights functional annotations reminiscent of appropriate dopamine receptor pathway activation and dopamine-induced toxic effects. Future studies will focus on highlighting additional phenotypic responses to dopamine in hESC-derived MSN systems. Our work shows the potential for a hESC model to further investigations of human mechanisms of MSN dysfunction in response to external perturbations with applications in understanding addiction and other neurological disorders.

References:

1. Arber, C. et al. Activin A directs striatal projection neuron differentiation of human pluripotent stem cells. Development 142, 1375–1386 (2015).
2. Berke, J. D. & Hyman, S. E. Addiction, Dopamine, and the Molecular Mechanisms of Memory. Neuron 25, 515–532 (2000).
3. Savell, K. E. et al. A dopamine-induced gene expression signature regulates neuronal function and cocaine response. Sci. Adv. 6, eaba4221 (2020).

Background: Commericalization of lignocellulosic biofuels and chemicals has been limited by the inability of current industrial microbial hosts to access and utilize all fermentable sugars without expensive pretreatment. Although conversion of the cellulose portion of plant biomass by pretreatment and engineering has been successful in many hosts, the pentose-rich and often cross-linked hemicellulose fraction remains both a barrier to cellulose access and the major portion of unconverted carbohydrates. The extremely thermophilic bacterium Caldicellulosiruptor bescii (Topt = 78 °C) can potentially overcome these barriers since it is capable of deconstructing lignocellulose without pretreatment and simultaneously fermenting hexose and pentose sugars [1]. While the cellulolytic capabilities have been thoroughly examined, few studies have comprehensively investigate hemicellulose deconstruction and metabolism in C. bescii.

Results: A comprehensive analysis of hemicellulose deconstruction and metabolism was conducted for C. bescii. Genomic and regulatory reconstruction of C. bescii reveals 65 genes responsible for hemicellulose metabolism, controlled by 9 separate regulators. A single transcriptional regulator, XynR, controls 28 of these genes 11 of which are hemicellulolytic glycoside hydrolases (GHs). To assess the role of the GHs in xylan metabolism, full length proteins were recombinantly expressed and biochemically characterized. Of the 11 GHs, 5 were found to have endo-β-xylanase activity, although branched substrates were more difficult to hydrolyse. The remaining 6 enzymes are debranching enzymes or exo-β-xylanases, which improve access and activity of the endo-xylanases. However, only one of the debranching enzymes is predicted to be extracellular, suggesting that C. bescii primarily uptakes oligosaccharides and hemicellulose crosslinking may remain a barrier for C. bescii. To supplement the biochemical activity, continuous cultures and transcriptomics were employed to study xylose metabolism in C. bescii. At a growth rate of 0.2 hr-1, xylose consumption was approximately 1.5-fold lower than glucose consumption, despite similar growth and fermentation yields. This suggests that xylose may be used in an assimilatory role, moreso than glucose. Transcriptional comparisons on glucose versus xylose show differential regulation of only 22 genes, which includes monosaccharide transporters and xylose isomerase, the first step in xylose metabolism. Interestingly, the rate limiting step of xylose metabolism, xylulose kinase, is not upregulated on xylose, but is up-regulated on xylooligosaccharides. Overall, this suggests that C. bescii maintains a broad inventory of enzymatic activity and tightly controls pentose metabolism.

Conclusions: The combination of enzymatic studies and continuous culture elucidate the mechanisms for hemicellulose hydrolysis and conversion in C. bescii. Improving hemicellulose decrosslinking and sugar turnover rate are two ongoing efforts to modify xylose metabolic regulation to further develop C. bescii as a biofuel platform organism.

References:

1. Crosby, J.R., L. T. Laemthong, A.M. Lewis, C.T. Straub, M.W.W. Adams, and R.M. Kelly. Extreme thermophiles as emerging metabolic engineering platforms. 2019. Curr. Opin. Biotechnol. 59:55-64.
2. Rodionov, D.A., I.A. Rodionova, V.A. Rodionov, A.A. Arzamasov, K. Zhang, G.M. Rubinstein,T.N.N. Tanwee, R.G. Bing, J.R. Crosby, I. Nookaew, M. Basen, S.D. Brown, C.M. Wilson, D.M. Klingeman, F.L. Poole, II, Y.Zhang, R.M. Kelly, and M.W. W. Adams. 2021. Transcriptional regulation of plant biomass degradation and carbohydrate utilization genes in the extreme thermophile Caldicellulosiruptor bescii. mSystems (in press)

Background: Many pregnancy complications are often the result of improper placental development. Specifically, impaired differentiation of trophoblast cells (TBs) of the placenta can result in complications like preeclampsia, miscarriage, and placenta accreta [1]. Due to a lack of appropriate models to study placental development, mechanisms involved in trophoblast differentiation remain poorly understood. Current in vitro trophoblast models exploit artificial signaling activation or inhibition to induce differentiation which prevent mechanistic studies and insights into extracellular cues that regulate trophoblast differentiation [2]. Here, we develop novel, chemically defined in vitro culture systems for the maintenance of human trophoblast stem cells (hTSCs) and for terminal trophoblast differentiation to extravillous trophoblast (EVT) and syncytiotrophoblast (STB). We then use these models to uncover mechanisms involved in trophoblast development.

Results: hTSCs derived from primary placenta or from human pluripotent stem cells (hPSCs) were cultured in the previously published trophoblast stem cell medium (TSCM) [1,2]. Upon passaging cells into a defined trophoblast differentiation medium (TDM), multinucleate STB formed that gained expression of appropriate STB markers and lost expression of TB markers. When TDM was supplemented with laminin-1, however, EVTs formed that expressed appropriate EVT markers and were able to spontaneously transition from an epithelial to mesenchymal cell type, similar to EVTs in vivo. Interestingly, when we differentiate to STB and EVT in the presence of the protein kinase C inhibitor, STB form but EVT differentiation is impaired. hTSCs cultured in TSCM were compared to hTSCs cultured in a chemically defined trophoblast stem cell medium (DTM). hTSCs cultured in DTM could be maintained for multiple passages and expressed similar TB markers as hTSCs cultured in TSCM. Interestingly, however, hTSCs cultured in DTM gained expression of a more primitive TB marker, CDX2. These cells also retained the ability to differentiate to EVT and STB under similar defined differentiation conditions.

Conclusions: We have developed a chemically defined trophoblast differentiation medium (TDM) where the addition of a single factor, laminin-1, switches the terminal trophoblast differentiation fate from STB to EVT. Using this model, we were able to determine that PKC signaling plays an important role in the formation of EVT. We have also developed a chemically defined trophoblast stem cell medium (DTM) where cells gain expression of a more primitive TB marker. This signifies that TBs of a later developmental stage can revert to an earlier developmental stage cell type.

References:

1. Mischler, A., Karakis, V., Mahinthakumar, J., Carberry, C., San Miguel, A., Rager, J., … & Rao, B. M. (2021). Two distinct trophectoderm lineage stem cells from human pluripotent stem cells. J. of Biol. Chem., 296.
2. Okae, H., Toh, H., Sato, T., Hiura, H., Takahashi, S., Shirane, K., … & Arima, T. (2018). Derivation of human trophoblast stem cells. Cell stem cell, 22(1), 50-63.

Background: As the predominant form of biomass on Earth, lignocellulose is a prime feedstock candidate to replace petroleum if it can be converted into useful products. The extremely thermophilic bacterium, Caldicellulosiruptor bescii (Topt=78oC), natively has the ability to metabolize the cellulose and hemicellulose contained in lignocellulose [1]. C. bescii can be genetically engineered to produce valuable chemicals such as ethanol and acetone [2,3]. Additionally, C. bescii can solubilize recalcitrant biomass, including switchgrass and poplar [1,4]. Populus trichocarpa provides a potential lignocellulose feedstock [4]. The Forest Biotechnology program at NCSU has the ability to genetically alter the monolignol synthesis pathway in the trees, allowing for feedstock improvements [5]. C. bescii grown on transgenic poplar biomass had improved fermentation characteristics and the microbe-feedstock pair showed potential for further optimization [6]. C. bescii also demonstrated an ability to ferment poplar stem sections nearly as well as milled poplar, potentially eliminating the need for pretreatment milling [1]. Both volatile production by C. bescii and the feedstock properties of P. trichocarpa need to be improved for potential industrial impact.

Results: Efforts using CRIPSPR-Cas9 to create an optimal transgenic poplar line with good growth and fermentation characteristics is underway. C. bescii fermentations are used to quantify the recalcitrance of poplar lines. Highlights from these results are presented. Additional efforts are underway to produce acetone and ethanol at industrially relevant productivity, selectivity, and titer through targeted protein and metabolic engineering. Progress toward this goal is presented.

Conclusions: The available genetic tools for both P. trichocarpa and C. bescii provide potential to optimize this microbe-feedstock pairing to become industrially relevant. Here we aim to produce high amounts of acetone and ethanol from the fermentation of transgenic poplar biomass.

References:

1. C.T. Straub, et al., Quantitative Fermentation of Unpretreated Transgenic Poplar by Caldicellulosiruptor bescii. Nat. Commun. 10 (2019)
2. A.M. Williams-Rhaesa, et al., Engineering redox-balanced ethanol production in the cellulolytic and extremely thermophilic bacterium, Caldicellulosiruptor bescii, Metab. Eng. Commun. 7 (2018) 1–9.
3. C.T. Straub, et al., Metabolically engineered Caldicellulosiruptor bescii as a platform for producing acetone and hydrogen from lignocellulose, Biotechnol. Bioeng. (2020).
4. P. Sannigrahi, A.J. Ragauskas, G.A. Tuskan, Poplar as a feedstock for biofuels : A review of compositional characteristics, Biofuels, Bioprod. Biorefining. 4 (2010) 209–226.
5. J.P. Wang, et al., Improving wood properties for wood utilization through multi-omics integration in lignin biosynthesis, Nat. Commun. 9 (2018).
6. C.T. Straub, et al., Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar. Biotechnol. Biofuels. 13, 43 (2020)

Background: The Sulfolobales are an order of thermoacidophilic Archaea (Topt > 65°C, pHopt < 4) which exhibit a broad range of metabolisms, including growth on novel substrates like sulfur and iron [1]. These metabolic pathways present an opportunity to leverage alternative energy sources for biosynthetic chemicals and have application in bioleaching processes [2]. Within this order, the obligate heterotroph Sulfolobus acidocaldarius (Saci) is one of the few species with a genetic system for metabolic engineering [3] and must be engineered to use the pathways of interest found in other Sulfolobales. Recent genome sequencing of Sulfolobales members has enable comparative genomics to shed light on the mechanism of sulfur oxidation, which is complicated by extensive abiotic interactions between reduced inorganic sulfur species (RISCs)[4-5].

Results: Thermodynamic calculations of free energy were used to evaluate the change in equilibrium of numerous abiotic sulfur reactions between the near-neutral cytoplasm and acid extracellular environment of the Sulfolobales. These calculations were also linked to energy conservation within the cell to determine the efficiency of sulfur oxidation. Comparative genomics was used to evaluate the presence of key genes for chemolithoautotrophy in Saci and provided targets for metabolic engineering. The resulting Saci mutants were evaluated for improved growth in the presence of elemental sulfur.

Conclusions: Changes in equilibrium behavior of several abiotic reactions has implications for multiple mechanisms of substrate accessibility and membrane transport of RISCs. Key energy-conserving enzymatic reactions were identified in Saci by evaluating reduction potential couples. A strain of Saci engineered for sulfur oxidation demonstrates some growth advantage in batch cultures with elemental sulfur.

References:

1. Lewis, AM, et al. (2021). The biology of thermoacidophilic archaea from the order Sulfolobales. FEMS Microbiol. Rev. 45(4): 1-60.
2. Auernik, KS, et al. (2008). Life in hot acid: Pathway analyses in extremely thermoacidophilic archaea. Curr. Opin. Biotechnol. 19(5): 445-453.
3. Wagner, M, et al. (2012). Versatile genetic tool box for the Crenarchaeote Sulfolobus acidocaldarius. Front. Microbiol. 3: e214.
4. Counts, JA, et al. (2021). Life in hot acid: a genome-based reassessment of the archaeal order Sulfolobales. Environ. Microbiol. 23(7): 3568-3584.
5. Willard, DJ and RM Kelly. (2021). Intersection of biotic and abiotic sulfur chemistry supporting extreme microbial life in hot acid. J. Phys. Chem. B. 125(20): 2543-5257.

Background: The main disadvantage of traditional methods of metal mining is environmental impacts, including the resulting wastewater containing toxic chemicals. Novel technologies are needed to decrease environmental side effects of metal extraction from ores. Bio-hydrometallurgical methods have shown promising potential to do so. In this case, bioleaching, the process of extracting metals using microorganisms, has been explored as one of the better alternatives to traditional metal ore extractions. Specifically, for copper bearing ores, such as pyrite and chalcopyrite, successful copper extraction has been reported. Application of thermoacidophiles have been explored recently. These microbes can grow in hot acid, which takes advantage of enhanced metal solubility. To improve bioleaching, engineered strains are needed to overcome the limitations of wildtype counterparts. Among thermoacidophiles, the order Sulfolobales, the genera Sulfolobus and Metallosphaera have attracted the most attention. Within the genus Sulfolobus, S. acidocaldarius has available genetic tools for metabolic engineering via a uracil-auxotrophy [1] but is not capable of bioleaching in its natural state. Metallosphaera sedula carries out iron oxidation and plays a role in leaching other metals. Ideally, the organism should be able to oxidize iron for better metal extraction, as well as oxidize sulfur to reduce passivation. In this study, the molecular machines of iron oxidation in M. sedula will be identified and the corresponding genes inserted into S. acidocaldarius to create a prolific bioleaching microorganism.

Results: A cluster of genes, dubbed the fox cluster, are known to be vital to iron biooxidation. Numerous genes, involving hypothetical proteins and cytochrome oxidase-like subunits, are believed to be present in this locus. Currently, the models of iron oxidation for Metallosphaera species are based on iron oxidation by the Fox cluster. The following model is proposed for iron oxidation by M. sedula: FoxCD takes the electrons from Fe(II), which are shuttled either through the downhill or the uphill electron transport chain. FoxA1, FoxA2, and FoxB form a complex, which is involved in the downhill pathway. FoxG and FoxCD may form a complex to carry out the uphill electron transport pathway which may involve CbsAB-SoxLN. FoxH is believed to be a Fe(II) sensor with a regulatory role. Other components are currently annotated as hypothetical, with their precise role to be determined.

Conclusions: As outlined above, recent findings highlight the importance of the fox cluster in iron oxidation of multiple Sulfolobales strains. Several components of this cluster remain unidentified, and still do not have any proven role in iron oxidation. By using genetic tools of S. acidocaldarius into which this cluster will be inserted, not only one can achieve an improved bioleaching strain, but further information on the fox cluster can also be harvested.

References:

1. Albers, S.-V. and Driessen, A.J.M. 2008. Conditions for gene disruption by homologous recombination of exogenous DNA into the Sulfolobus solfataricus genome. Archaea (Vancouver, B.C.). 2, 3 (Dec. 2008), 145–149. DOI:https://doi.org/10.1155/2008/948014.

Background: Human cerebral organoids are readily generated from human embryonic stem cells and human induced pluripotent stem cells and a useful model for studying human neurodevelopment. These cerebral organoids have numerous advantages including three-dimensional architecture, multiple cell types, and their ability to recapitulate early fetal development [1-3]. There is a need to continue developing and improving them for reproducibility, and complexity, as well as better mimic in vivo tissues. Matrigel is a gelatinous, heterogenous mixture of extracellular matrix proteins and growth factors secreted by Engelbreth-Holm-Swarm mouse sarcoma cells and is integral to cerebral organoid generation. Previous work has examined and quantified Matrigel components [4], but due to the complexity of Matrigel creating a synthetic replacement has been difficult. It plays a critical role in cerebral organoid development as it supports organoid buds and promotes neural progenitor polarization. However, the effects of Matrigel delivery method and dosage have not been reported. In human whole brain cerebral organoids (hCOs) protocols, organoids are embedded in Matrigel after neuroepithelial induction, so the effects of solubilized Matrigel are unknown.

Results: To better understand how the delivery of Matrigel affects human whole brain cerebral organoids we varied the delivery method and amount of Matrigel along with exposure time. Organoids were generated using solubilized Matrigel as an alternative to established Matrigel embedding. To assess the effect of solubilized Matrigel, we analyzed organoid size, morphology, and cell differentiation. Increased Matrigel exposure time and concentration correlated with larger organoid growth. Moreover, radially organized structures developed independent of Matrigel exposure. High and low Matrigel exposure resulted in distinct morphological phenotypes, suggesting an optimal amount of Matrigel in between the two extremes.

Conclusions: Our findings suggest while hCOs form radially organized structures independent of Matrigel exposure, the fundamental growth and development of hCOs is significantly affected by Matrigel dosage and delivery method. Excess or sparse Matrigel exposure significantly affects gross hCO morphology and size, and Matrigel delivery method affects hCO cell differentiation.

References:

1. M.A. Lancaster, M. Renner, C.A. Martin, D. Wenzel, L.S. Bicknell, M.E. Hurles, T. Homfray, J.M. Penninger, A.P. Jackson, J.A. Knoblich, Cerebral organoids model human brain development and microcephaly, Nature. 501 (2013) 373–379. https://doi.org/10.1038/nature12517.
2. J.G. Camp, F. Badsha, M. Florio, S. Kanton, T. Gerber, M. Wilsch-Bräuninger, E. Lewitus, A. Sykes, W. Hevers, M. Lancaster, J.A. Knoblich, R. Lachmann, S. Pääbo, W.B. Huttner, B. Treutlein, Human cerebral organoids recapitulate gene expression programs of fetal neocortex development, Proc. Natl. Acad. Sci. U. S. A. 112 (2015) 15672–15677. https://doi.org/10.1073/pnas.1520760112.
3. G. Quadrato, T. Nguyen, E.Z. Macosko, J.L. Sherwood, S.M. Yang, D.R. Berger, N. Maria, J. Scholvin, M. Goldman, J.P. Kinney, E.S. Boyden, J.W. Lichtman, Z.M. Williams, S.A. McCarroll, P. Arlotta, Cell diversity and network dynamics in photosensitive human brain organoids, Nature. (2017). https://doi.org/10.1038/nature22047.
4. N.T. Kohen, L.E. Little, K.E. Healy, Characterization of Matrigel interfaces during defined human embryonic stem cell culture, Biointerphases. (2009). https://doi.org/10.1116/1.3274061.

Background: Rapid, sensitive serological antibody test plays an important role in diagnosis of COVID-19. Here, we developed a single-nanoparticle, digital immunoassay for ultrasensitive COVID-19 serological test. In this assay, the scattering signal is generated based on the spectral change upon the formation of immunocomplex, due to the plasmonic coupling effect between gold and silver nanoparticles. Darkfield imaging and counting at single nanoparticle level were performed to significantly enhance the assay sensitivity compared to the conventional lateral flow assay.

Results: In the preliminary experiments, we used streptavidin-biotin interaction to mimic antibody-antigen interaction and functionalized the nanoparticles accordingly. A relationship was established between different species of nanoparticle and streptavidin concentration. From particle counting, we found the percentage of plasmonic-coupled nanoparticle is related to the amount of added streptavidin-conjugated nanoparticle.

Conclusions: Out data demonstrates the feasibility of a new immunoassay based on plasmonic coupling and single-nanoparticle counting. The assay can be further engineered to be made compatible with our smartphone readout system to adapt for COVID-19 diagnosis requirements in the point-of-care setting

References:

1. Poon, C. Y., Wei, L., Xu, Y., Chen, B., Xiao, L., & Li, H. W. (2016). Quantification of cancer biomarkers in serum using scattering-based quantitative single particle intensity measurement with a dark-field microscope. Analytical chemistry, 88(17), 8849-8856.
2. Zhang, Y., Malekjahani, A., Udugama, B. N., Kadhiresan, P., Chen, H., Osborne, M., … & Chan, W. C. (2021). Surveilling and Tracking COVID-19 Patients Using a Portable Quantum Dot Smartphone Device. Nano letters.

Background: Directed cell motility is critical for biological processes such as cancer metastasis, embryonic development, and wound repair. Wound healing, for example, requires the migration and proliferation of fibroblasts to remodel the extracellular matrix in the dermis. Fibroblasts, which exhibit a mesenchymal migration phenotype, crawl toward higher concentrations of soluble growth factors (chemotaxis) or immobilized proteins in the extracellular matrix (haptotaxis). Elucidating how fibroblasts haptotax on gradients of surface-bound fibronectin, an extracellular matrix protein, is the goal of this project. In mesenchymal cell migration, the direction of migration is determined by the “winner” of multiple competing protrusions. Protrusion dynamics are regulated by dendritic F-actin networks termed lamellipodia that impose forces on the cell membrane. The membrane protrudes outward when the F-actin network is growing and engaged with adhesions at the leading edge. In contrast, myosin II contractility pulls the F-actin network and often promotes membrane retraction. The directional compass for fibroblast chemotaxis is the local inhibition of myosin II in the up-gradient protrusions that allows them to persist [1]. However, the mechanism of fibroblast haptotaxis is far less understood. In this project, the optimal surface-bound fibronectin gradient for haptotaxis will be determined by generating a broad landscape of gradient conditions and measuring the haptotactic response. After the optimal gradient condition is determined, the mechanism of fibroblast haptotaxis will be explored by analyzing the dynamics of focal adhesions and myosin II, key players in fibroblast migration, at the optimal gradient condition. In addition, the role of fascin, an actin bundling protein that has been previously implicated in fibroblast haptotaxis will also be investigated [2].

Results: To generate surface-bound fibronectin gradients, Y-junction microfluidic devices were utilized. These devices have been used to generate a landscape of soluble growth factor gradients (e.g. platelet-derived growth factor) via diffusion to study chemotaxis [3]. For surface-bound fibronectin gradients, however, the kinetics of fibronectin adsorption are much faster than diffusion. Therefore, surface-bound fibronectin gradients were instead formed by tightly controlling the contact time between the bulk solution with the glass substrate using syringe pumps or paper wicking methods. Initial live-cell imaging experiments of NIH/3T3 fibroblasts migrating on gradients of fibronectin have indicated that the process could depend on both the underlying fibronectin density and gradient steepness. Future research efforts will be aimed toward generating surface-bound fibronectin gradients reproducibly.

References:

1. Asokan, S.B., Johnson, H.E., Rahman, A., King, S.J., Rotty, J.D., Lebedeva, I.P., Haugh, J.M., and Bear, J.E. (2014) Mesenchymal Chemotaxis Requires Selective Inactivation of Myosin II at the Leading Edge via a Noncanonical PLCγ/PKCα Pathway. Dev. Cell, 31: 747-760.
2. Johnson, H.E., King, S.J., Asokan, S.B., Rotty, J.D., Bear, J.E, and Haugh, J.M. (2015) F-actin bundles direct the initiation and orientation of lamellipodia through adhesion-based signaling. J. Cell Biol., 208(4): 443-455.
3. Baldwin, S.A., Van Bruggen, S.M., Koelbl, J.M., Appalabhotla, R., Bear, J.E., and Haugh, J.M. (2021) Microfluidic devices fitted with “flowver” paper pumps generate steady, tunable gradients for extended observation of chemotactic cell migration. Biomicrofluidics, 15(4): 1-12.

Background: Directed migration of fibroblasts is an essential part of the wound healing process as fibroblasts play a key role in wound closure and insufficient migration is associated with chronic wounds [1]. In the context of wound healing, spatial sensing of platelet-derived growth factor (PDGF) is of particular interest because it is a chemoattractant secreted by wound ‘first responders’ (e.g., platelets, macrophages) [2]. It has experimentally been shown that the Phospholipase C (PLC)/Protein Kinase C (PKC) pathway is indispensable for fibroblast chemotaxis [3] and a computational model has identified a mechanistic basis for sensing shallow PDGF gradients [4]. To test these model predictions, however, we require an experimental system capable of linking graded PDGF inputs to asymmetric intracellular signaling.

Results: Herein, we highlight a building block of such an experimental system. PLC is activated by PDGF receptors and produces the lipid diacylglycerol (DAG). We demonstrate that we can track the PLC/PKC pathway response to PDGF via live-cell total internal reflection fluorescence (TIRF) microscopy using a stably expressed translocation DAG biosensor. Importantly, we show kinetics of the DAG response qualitatively resemble the model prediction.

Conclusions: Measuring intracellular signaling in live cells is an important first towards experimentally interrogating PDGF spatial sensing mediated by the PLC/PKC pathway. Additionally, our cell lines stably expressing the DAG biosensor can be combined with chemotactic gradient assays to fully explore the mechanisms mediating PDGF gradient sensing.

References:

1. Eming, S. A., Martin, P. & Tomic-Canic, M (2014). Wound repair and regeneration: Mechanisms, signaling, and translation. Sci. Transl. Med., 6: 265sr6.
2. Bear, J. E. & Haugh, J. M. (2014). Directed migration of mesenchymal cells: where signaling and the cytoskeleton meet. Curr. Opin. Cell Biol., 30: 74–82
3. Asokan, S.B., Heath Johnson, Anisur Rahman, Samantha J. King, Jeremy D. Rotty, Irina P. Lebedeva, Jason M. Haugh, & James E. Bear (2014). Mesenchymal Chemotaxis Requires Selective Inactivation of Myosin II at the Leading Edge via a Noncanonical PLCγ/PKCα Pathway. Dev. Cell, 31: 747-760.
4. Nosbisch, J.L., Anisur Rahman, Krithika Mohan, Timothy C. Elston, James E. Bear, and Jason M. Haugh (2020). Mechanistic models of PLC/PKC signaling implicate phosphatidic acid as a key amplifier of chemotactic gradient sensing. PLoS Comput. Biol. 4: e1007708

Background: Guiding the formation, development, and tissue integration of vascular networks is a key component of the regenerative medicine toolbox, as it plays a crucial role in the manufacturing of engineered tissue constructs and ensuring their grafting success. Such development can be guided by biochemical patterning of the substrates, that is, the spatial distribution and display of peptides and growth factors that guide the adhesion, differentiation, and proliferation of stem and progenitor cells.

Results: We have developed a technique to enable the spatiotemporal distribution of growth factors to cells using peptide ligands which bind vascular endothelial growth factor (VEGF); this enables the controlled release of VEGF, ultimately enhancing the formation of a vascular network. Currently, we develop engineered tissues constructs (ETCs) out of GelMA, which is an ideal substrate for tailored stiffness and bio-functionality, and covalently pattern them with a VEGF binding peptide. The peptide is synthesized by Fmoc solid-phase synthesis, as derivatized with a cysteine on the C-terminus to enable conjugation onto the GelMA substrates via thiol-ene coupling. The conjugated peptides allow for the non-covalent binding of VEGF to the scaffold, enabling facile uptake by cells. We demonstrated that in absence of cells, growth factors did not show a bolus release and remained conjugated to the peptide for up to 72 hours. Along with this, we developed microscale VEGF patterns providing spatially-tuned delivery of growth factors to human umbilical vein endothelial cells (HUVECs). The ability to organize growth factors in an ETC with easy uptake by cells provides a new functionality for promoting vascularization.

Conclusions: Our results demonstrate a method to incorporate bio-chemical cues into scaffolds that may mimic in vivo growth factor patterning. Future efforts will investigate the use of multiple growth factors and/or cell types to control the development of ETCs spatially and temporally.

Background: Polymer melt extrusion of high aspect ratio fiber, such as segmented hollow fiber, is important in creating insulating fibers, high surface area fibers, and membranes. This process is hard to characterize experimentally due to an expansive list of parameters and phenomena that dictate optimal fiber formation [1]. A polymer melt’s viscoelastic fluid properties cause a melt to behave with varying characteristics of both a fluid and solid, depending on processing conditions. Examples of processing conditions include shear rate, fluid temperature, and cooling rate. For example, viscosity, a bulk fluid property, changes as a function of temperature and shear rate in polymer melts. External forces, such as fiber line tension and cooling air flow, affects final fiber geometry through deflection of fluid flow [2]. To elucidate the optimal parameters needed to maintain a stable flow regime, we utilize computational fluid dynamics to isolate the effect of each parameter and determine defining phenomena in our system. This research utilizes rheoTool [3], a viscoelastic software package incorporated into OpenFOAM, an open source CFD platform. In rheoTool, we utilize a two-phase solver, using the Giesekus and Newtonian models of stress for the polymer and air phases, respectively.

Results: We optimized the two-phase solver of rheoInterFoam, a solver from rheoTool, allowing for stable 2-phase simulation with minimal surface instability at the polymer-air interface. This was done through separately calculating the stresses for the two phases, then combining the stresses into one unified stress field in accordance with volume fraction, which is used in CFD calculations for fluid flow. By utilizing a viscoelastic equation, the Giesekus equation, for the polymer phase, we can observe die swell, a consequence of a polymer melt’s viscoelastic properties. In addition, we have introduced a method for simulating fiber line tension, a critical processing technique, by setting a boundary condition on the component of stress tensor equal to the fiber line tension. This results in a thinner fiber, comparable to what is seen in industrial fiber processes.

Conclusions: We have developed a fiber spinning simulation for polymer melts with accurate physics for tension, die swell, and polymer-air interface. In future work, we will add physics for temperature and modify properties that are dependent on it, such as viscosity and crystallization. With a comprehensive simulation, we hope to ascertain optimal fiber processing regimes, which will aid fiber design decisions.

References:

1. McKinley, Gareth H. (2005). Dimensionless Groups for Understanding Free Surface Flows of Complex Fluids. SOR Rheology Bulletin, 74.
2. Rwei, Syang-Peng. (2001). Formation of Hollow Fibers in the Melt-Spinning Process. Journal of Applied Polymer Science, 82: 2894-2902.
3. Pimenta, F., Alves M.A. (2017). Stabilization of an Open-Source Finite-Volume Solvers for Viscoelastic Fluid Flows. Journal of Non-Newtonian Fluid Mechanics, 239: 85-104.

Background: The aggregation of human α-synuclein (αSyn) is associated with many neurodegenerative diseases called “synucleinopathies” such as Parkinson’s disease, dementia with Lewy bodies and multiple system atrophy. Both the non-amyloid component (NAC) region of αSyn (residues 61-95) and the preNAC region (residues 1-60) are thought to play important roles in αSyn fibrillation, the latter of which contains seven familial mutations. Of the sixty residues in the αSyn preNAC region, the P1 (residues 36-42) and P2 (residues 45-57) segments have been shown experimentally to be controllers of the aggregation of the full length αSyn [1]. Eliminating P1 resulted in inhibition of αSyn aggregation in neutral pH environments. Inhibition was observed when removing combined P1 and P2 in both neutral and acidic environments. We have been investigating the aggregation mechanisms of motifs that contain both P1 and P2, searching for the key factors in the aggregation of full length αSyn. Discontinuous molecular dynamics simulation with the PRIME20 force field was used to study self-assembly of P3 (residues 36-57), P3Plus (residues 32-61) and P3NExtend (residues 27-57). Each segment was examined at a simulation condition that supports fibril formation – a 24-peptide system at 10mM and temperature 330.5K.

Results: Our computational results predict high β-structure propensity for all three motifs, as expected based on their secondary structure propensity scores according to Kang et al. [2]. The fibrillar structures that form in our simulations contain a preponderance of aligned β-hairpins. These findings are consistent with those of Salveson et al. [3] who reported experiments showing that peptides of residues 36-55 adopt β-hairpin structures during oligomerization. Mirecka et al. [4] successfully inhibited full length αSyn aggregation by inducing β-hairpin formation in the P3 region with a β-wrapin. These experiments suggest that the β-hairpin structures formed by P3 region play an essential role in determining whether full length αSyn aggregates or not.

Conclusions: Our simulations of the wildtype P3, P3Plus and P3NExtend as well as their point mutations (currently L38A, L38M, Y39A, V40A and S42A) have allowed us to study the aggregation mechanisms and nucleation processes, and identify which residues are aggregation prone. From this understanding, we aim to design inhibitor peptides targeted to certain regions on the full-length αSyn to prevent elongation of αSyn aggregates using a highly efficient computational peptide binding design algorithm, PepBD.

References:

1. Doherty et al. (2020). A short motif in the N-terminal region of α-synuclein is critical for both aggregation and function. Nat. Struct. Mol. Biol., 27(3): 249-259.
2. Kang et al. (2012). N-terminal acetylation of α-synuclein induces increased transient helical propensity and decreased aggregation rates in the intrinsically disordered monomer. Protein Science., 21(7): 911-917.
3. Salveson et al. (2016). X-ray Crystallographic Structure of Oligomers Formed by a Toxic β-Hairpin Derived from α-Synuclein: Trimers and Higher-Order Oligomers. J. Am. Chem. Soc., 138(13): 4458-4467.
4. Mirecka et al. (2014). Sequestration of a β-Hairpin for Control of α-Synuclein Aggregation. Angew. Chem. Int. Ed., 53(16): 4227-4230.

Background: Ethylene is an extremely important chemical for several industries, especially petrochemical, and is produced in large quantity across the globe. It is used in the manufacturing processes of useful products including polyethylene – the most widely used plastic. [1] Steam cracking, the petrochemical process of breaking down hydrocarbons, is currently the most used method of ethylene production. The string of procedures involved in completing the steam-cracking process has energy requirements in the range of 15-25 GJ/tonne of ethylene produced when using ethane as a feedstock, with corresponding ethylene yields of 80-84 wt.%, and emissions of 1.0-1.2 tonne CO2/tonne ethylene. [2] A leading contender to replace steam cracking is oxidative dehydrogenation (ODH). This process is exothermic, as opposed to the endothermic steam-cracking case, with a heat of reaction ΔHrxn = -105.5 kJmol-1. [3] The ODH reaction requires ethane to be exposed to oxygen, which has potential to result in complete combustion and reactor runaway. However, combining ODH with the chemical looping (CL) method allows for indirect contact using a metal-oxide carrier solid. The CL-ODH system allows for repeated use of the solid through a regeneration cycle. Preliminary experiments and simulations report that CL-ODH of ethane results in 80% less energy consumption, as well as 80% less CO2 emissions when compared to steam cracking.[4] More modeling is required to assess the validity of the CL-ODH of ethane on an industrial scale. This can be achieved using MATLAB coding techniques to solve a system of partial differential equations to model the composition and temperature profiles in the reactor.

Results: The current MATLAB code produces reasonable surfaces for composition and temperature when varying location and time within the reactor. The model predicts 71.9% conversion of the ethane for the end of the reactor at time t = 100s, somewhat higher than the experimentally observed ~55% at starting temperature T = 1013K. A hotspot is predicted as well, which is reported in the experimental results. The predicted active oxygen depletion of the solid metal-oxide is an average of 6.2% across the length of the reactor at time t = 100s.

Conclusions: Based on the current results, further changes must be made to the MATLAB model. The low active oxygen depletion of the solid is a good sign that the current kinetic model neglecting changes in the solid is sufficient for further modeling. However, more reactions need to be added to increase the accuracy of the model. Completing this model will allow for its generalization in the future for use with other non-catalytic solid packed beds.

References:

1. The Editors of Encyclopaedia Britannica (2019). Polyethylene. Britannica. Retrieved from https://www.britannica.com/science/polyethylene
2. Ren, Tao, Martin Patel, and Kornelis Blok (2006). Olefins from Conventional and Heavy Feedstocks: Energy Use in Steam Cracking and Alternative Processes. Energy, 31: 425-451.
3. Gärtner, Christian A., André C. van Veen, and Johannes A. Lercher (2013). Oxidative Dehydrogenation of Ethane: Common Principles and Mechanistic Aspects. ChemCatChem, 5: 3196-3217.
4. Haribal, Vasudev P., Luke M. Neal, and Fanxing Li (2017). Oxidative Dehydrogenation of Ethane Under a Cyclic Redox Scheme – Process Simulations and Analysis. Energy, 119: 1024-1035.

Background: When invading a wound, skin cells called fibroblasts are presented with an array of different directional cues. These directional cues include soluble chemical cues, immobilized ligands, and differences in tissue stiffness among others. Among the directional cues mentioned, gradients of immobilized ligands found in the extracellular matrix are understudied yet thought to be critical for invasion. Recent publications show an importance of lamellipodia and integrin-actin machinery in migration toward these surface bound ligands, called haptotaxis [1]. Considering the initial literature on the haptotactic response of fibroblasts, a 2-D haptotactic migration model was developed to mimic fibroblast migration with integrin signaling.

Results: A semideterministic phase field model was used to simulate adhesion based signaling and migration. Adhesions stochastically appear biased by a gradient signal, and cells, modeled according to the phase field formalism, are superimposed on the gradient of adhesions. Any adhesions that are underneath the cell in the deterministic COMSOL solver can cause an autocatalytic signaling response that locally influences membrane protrusion. Upon analysis, cells that lie in higher steepness regions at low relative stimulus concentrations tend to migrate the most directionally. If the cell is in a highly dense matrix region, the cell tends to migrate without a constant direction or stall out.

Conclusions: Preliminary results of the model show highly directional migration in high gradient regions, less directional migration in shallower gradients, and stalling in denser gradient regions. These results line up with initial observations that 3T3 fibroblast cells on haptotactic gradients. These results are promising as the initial model is a toy model that at its basic level still grasp some biological relevance. In later model iterations, it would be desired to find a signaling network that mimics cells in vitro where cells are able to integrate lower signaling gradients less readily than steeper ones. Additionally, adding actin dynamics and replacing the current protrusive actin like variable should lead to more fibroblast like cell shapes, such as competing lamellipodia and convex membrane curves.

References:

1. King SJ, Asokan SB, Haynes EM, et al. Lamellipodia are crucial for haptotactic sensing and response. J Cell Sci. 2016;129(12):2329-2342. doi:10.1242/jcs.184507

Background: Developing efficient and sustainable hydrogen and syngas production technologies that utilize superfluous feedstocks, such as crude glycerol, is a necessary step in the transition away from fossil fuels. State-of-the-art techniques for glycerol conversion are energetically inefficient and exhibit poor H2:CO ratios, thereby necessitating costly and energy-intensive downstream syngas conditioning. Sorption enhancement improves H2 concentrations, but the commonly used CaO-based sorbents are prone to sintering during the high temperature decarbonation steps – leading to a rapid loss in CO2 sorption capacity over ~10 cycles. Here, we report the first usage of perovskite-based phase transition sorbents (PTSs) capable of avoiding sintering and retaining both catalytic activity and sorption capacity over repeated cycles.

Results:  In a sorption-enhanced reforming scheme using a PTS, the material absorbs CO2 produced from the water-gas shift (WGS) reaction during the reforming step and forms stable carbonates as well as reduced metals. This in-situ carbonation drives the WGS reaction to produce more H2, thereby improving the H2 composition of the syngas product. In a subsequent high temperature regeneration step, the CO2 is released, and the PTS reverts back to its original phase without undergoing sintering or permanent phase change. In this study, Ca A-and Ni B-site doped SrFeO3-δ (SrxCa1-xFeyNi1-yO3-δ or SCFN) was evaluated as a PTS for the sorption enhanced – steam reforming of glycerol (SESRG). SCFN is a tri-functional material capable of (i) catalyzing the reforming of glycerol; (ii) absorbing CO2 in-situ; and (iii) releasing oxygen from lattice sites for increased H2 yields. Bench-scale packed bed reactor experiments using a liquid injection platform were conducted to screen five compositions of SCFN on the basis of their reforming activity, sorption capacity, syngas conditioning, and longevity over multiple cycles. Redox and phase characterizations of the PTS were conducted via thermogravimetric analysis (TGA), as well as ex-situ and in-situ x-ray diffraction (XRD) in order to elucidate the dynamic phase behavior of the PTS throughout the reaction cycles. All five compositions of SCFN tested yielded syngas H2:CO > 3 throughout the entire 20-min reduction period and maintained their activity and sorption capacity for 15+ cycles (with SCFN-5591 lasting as many as 50 cycles). Ex-situ XRD revealed the reliable recyclability of the SCFN phases and in-situ XRD confirmed sequential decarbonation and re-oxidation steps of the PTS during the regeneration step. TGA results indicated that the extent of B-site reduction, and thus oxygen donation, is highly sensitive to the reducing environment and the presence of water. X-ray photoelectron spectroscopy (XPS) confirmed the presence of carbonates and reduced Fe species on the PTS surface after the reforming step, but the absence of detected Ni necessitates further characterization and chemisorption experiments.

Conclusions: The A-and B-site doped SrFeO3-δ perovskite demonstrated excellent PTS properties including high glycerol conversions, reliable recyclability within cycles, and stable sorption capacity over many cycles. The high degree of freedom of cation doping in perovskite materials opens the door to practically infinite unique materials suitable for PTS applications. Future work will involve screening of additional perovskites, further solid-state chemistry characterization, and experimental validation in a fluidized bed reactor configuration using genuine biomass feeds.

Background: Ethylene is an essential building block of various important chemical intermediates and products1. State-of-the-art for ethylene production is based on steam cracking of ethane and other hydrocarbon feedstocks, which has energy demand as high as 16 GJ/ton C2H4 produced2,3 Chemical looping-oxidative dehydrogenation (CL-ODH) represents such an exothermic, non- equilibrium limited approach for ethylene production since H2 would be oxidized to H2O in the process3. Previous studies have achieved ~75% H2 conversion and 74% C2+ yield using molten salt promoted Mg6MnO8 (MGM) as the core-shell structured redox catalyst for CL-ODH4

Results: In this present paper, we demonstrate the molten salt promoted redox catalysts CL-ODH as a general strategy ethylene production. Various combinations of molten salt promoters (Mo, V and W containing alkali molten salt and their mixtures) and selected redox catalysts, CuMn2O4 (CMO) and MGM are screened. Molten salt (or eutectics) promoted redox catalysts lead to a maximum single pass ethylene yield of ~63% with up to 85% H2 conversion. Catalyst testing results from promoted CMOs with various Cu:Mn ratio show that decrease of PPOO2,eeee of the redox catalysts would decrease H2 conversion but increase COx selectivity. Further optimization of PPOO2,eeee by varying Cu:Mn ratio leads to <15% COx selectivity, >90% H2 conversion and ~60% ethylene yield; Catalyst testing with various molten salt promoter on MGM shows both better results from eutectic promoted catalysts than unary molten salt promoted catalysts, which results in ~74% C2+ yield and <5% COx selectivity. This indicates that eutectics mixtures promoters could have synergistic effect for optimizing both H2 conversion and COx selectivity. X-ray diffraction and X-ray photoelectron spectroscopy both indicate that all of the samples formed stable promoter shell and redox core phases. These results demonstrate that the core-shell catalyst strategy can be used as a general catalyst design strategy, redox oxide@molten promoter for CL-ODH.

Conclusions: The redox oxide@molten salt strategy is demonstrated to be a viable and flexible strategy. It potentially opens up new opportunities to further optimize and intensify the C2H4 production process from two aspects: 1) The core redox catalyst could be optimize to minimize COx selectivity and maximize H2 conversion by tailoring PPOO2 . 2) The shell molten salt promoter could be improved by screening molten salts and their eutectic mixtures to optimize C2+ selectivity and COx selectivity and H2 conversion.

References:

1. Perry, R. Ethane Storage and Distribution Hub in the United States. Department of Energy November 2018.
2. Ren, T.; Patel, M.; Blok, K. Olefins from Conventional and Heavy Feedstocks: Energy Use in Steam Cracking and Alternative Processes. Energy 2006, 31 (4), 425–451. https://doi.org/10.1016/j.energy.2005.04.001.
3. Gärtner, C. A.; van Veen, A. C.; Lercher, J. A. Oxidative Dehydrogenation of Ethane: Common Principles and Mechanistic Aspects. ChemCatChem 2013, 5 (11), 3196–3217.
4. Neal, L. M.; Yusuf, S.; Sofranko, J. A.; Li, F. Oxidative Dehydrogenation of Ethane: A Chemical Looping Approach. Energy Technol. 2016, 4 (10), 1200–1208. https://doi.org/10.1002/ente.201600074.

Background: In response to rising atmospheric CO2 concentrations, the scientific community has become increasingly interested in the development of economically viable emissions reduction solutions. Consequently, many research efforts now seek ways to significantly lessen the carbon footprints of essential petrochemical processes like olefin synthesis. Although olefins are conventionally produced via energy-intensive steam cracking, chemical looping oxidative dehydrogenation (CL-ODH) represents an energetically efficient alternative to this method, one which minimizes downstream gaseous separation by using reactive intermediates to shuttle oxygen from oxidizing to reducing environments. With an appropriate oxygen carrier, the highly customizable CL-ODH reaction scheme can capture CO2 from flue gas and use it to enhance alkene product yield. Molten-salt-mediated CL-ODH (MM-ODH) seeks to do exactly this, combining the carbon capture capability of molten salts with the ODH activity of perovskite oxides to sustainably produce value-added olefins.

Results: Data collected thus far reflect the MM-ODH performance of two distinct reactor configurations: a packed bed and a molten salt-metal oxide slurry. The packed bed reactor employs a novel core-shell catalyst with a eutectic Li-Na-K (LNK) outer layer that melts at moderate temperatures (~450oC) to fully envelope a La0.8Sr0.2FeO3 (LSF) metal oxide center, whereas our LNK-LSF molten slurry relies on suspended LSF nanoparticles to enhance the already-promising MM-ODH activity of pure molten salt baths [1]. Under the packed bed arrangement, we identified several sets of reaction conditions where ethane conversion and ethylene yield surpassed 60% and 50%, respectively, while achieving ethylene selectivities greater than 80%. The slurry configuration performed even better, reaching ethylene yields of ~65% and ethylene selectivities >90% at 800oC. Furthermore, when re-oxidized with a premixed flue gas simulant (~15% CO2), the slurry captured 80% of CO2 (>90% in the initial stages) and converted ~90% of it into olefin products. Lastly, both set-ups significantly suppressed methane production and COx selectivity relative to the standalone LSF catalyst, demonstrating an additional advantage of the added molten salt.

Conclusions: Preliminary analyses of olefin synthesis using chemical looping ODH, the basis of MM-ODH, have indicated up to 90% energy savings and emissions reduction when compared to conventional methods of olefin synthesis[2]. By supplementing this proven scheme with the CO2 capture capacity of molten salts, we aim to develop an economically practical method of olefin synthesis with a net negative impact on global CO2 emissions.

References:

1. Liu, J., Gao, Y., Wang, X. & Li, F. Molten-salt-mediated carbon dioxide capture and superequilibrium utilization with ethane oxidative dehydrogenation. Cell Reports Physical Science 2, 100503 (2021).
2. Neal, L. M., Haribal, V. P. & Li, F. Intensified Ethylene Production via Chemical Looping through an Exergetically Efficient Redox Scheme. iScience 19, 894–904 (2019).

Background: The world’s population, industrialization, and resource consumption is growing rapidly, and with it the demand for ethylene. In 2016, the global demand for ethylene reached approximately 162 million metric tons [1] and is projected to grow to 376 million metric tons by 2050 [2]. Steam cracking is conventionally used to produce ethylene, but is highly endothermic and CO2- intensive. In contrast, Oxidative Dehydrogenation (ODH), another technique for ethylene production, is a net exothermic reaction, boasts higher single-pass conversion, and generates less coke, putting it at the forefront of current research. Its limitations, namely requirement of costly pure oxygen and feed safety concerns, have the potential to be avoided via Chemical Looping ODH (CLODH). This process avoids potential safety hazards with oxygen co-feed and can result in the reduction of 82% of energy usage and CO2 emissions by minimizing unwanted combustion [3]. In addition to this, selective combustion of hydrogen can be obtained, further increasing the chemical route’s viability. To probe the kinetics of this reaction, Molecular Beam Mass Spectrometry (MBMS) can be employed.

Results: In the MBMS system, choked flow of the gas passing through the reactor’s orifice is induced with the significant difference between the reactor pressure (760 Torr) and the reaction chamber pressure (1~5 Torr) it resides in. The residence time in the reaction zone is set by the critical orifice (0.2mm) at a given reactor temperature and pressure which was experimentally determined. Precise alignment of the critical orifice and the sampling probe was obtained using pressure in the skimmer chamber downstream from the reactor as an indicator. Dynamic changes in the reactor’s temperature and flowrate were systematically tested for spatial and temporal dependence, respectively.

Conclusions: Small movement of the critical orifice within 1mm of the sampling probe’s position produced significant pressure drops and subsequent drop of MS signal. This indicates the high sensitivity of the system’s alignment with the ability to detect low-concentration species. The isothermal operation of the reaction zone demonstrated simplifies the dynamics captured later in kinetic modelling steps. Step changes in carrier gas flowrate exhibited first-order decay responses of the system. Overall, MBMS exhibits robust dynamic response and can be used for the mechanism study of selected chemical looping processes.

References:

1. S. Lewandowski, Ethylene – Global, Asia Chemical Conference, 2016.
2. Technology Roadmap- Energy and GHG Reductions in the Chemical Industry via Catalytic Processes, International Energy Agency, 2013.
3. V.P. Haribal et al. Energy. 119, 1024. 2017.

Background: The exponential increase in plastic utilization and the lack of proper disposal or conversion into reusable resources, has created the global problem of microplastic accumulation in freshwater and marine environments [1, 2]. The current methods for the removal of these highly undesirable colloidal dispersions through filtration or centrifugation may be resource-heavy, time-consuming, and cost-prohibitive [3, 4]. As an alternative, we will present a novel solution of using soft dendritic colloids (SDCs), or dendricolloids, as a physical means to remove microplastics from aquatic environments. These particles represent a new class of soft material which has a unique polymeric morphology with a hyperbranched, nanofibrous corona and large excluded volume [5]. SDCs possess adhesive and gelation properties which enable capabilities of highly efficient capture of large amounts of microplastics in polluted water [5].

Results: Water sources vary in environments and testing our system in diverse conditions helps observe the difference of behavior. With a focus on microplastic capture, we investigate how the interfacial properties of the dendricolloids and microplastics affect their heterocoagulation in various ionic strength and pH conditions. We found the highest capture efficiency around 0.6 and 0.8 M NaCl, which turns out to be close to the salinity of the ocean. For the pH range of 4.5 to 8.5, it was noted that the highest capture efficiency was found around pH 7 an 8. Different size sulfonated polystyrene beads were tested and compared to each other as well as amidine polystyrene and polyethylene. The different polymer beads enabled the investigation of interfacial properties of a range of potential aquifer pollutants.

Conclusions: This project helps with the understanding of the interactions between SDCs and microplastics as we theorize that both van der Waals and electrostatic interactions play a role in microplastics adsorption. We also gain a better comprehension of the unique morphology of the particles and how it affects the capturing of these microplastics. This will enable the forthcoming development of highly efficient microcleaners for environmental remediation.

References:

1. Eerkes-Medrano, D., Thompson, R.C., Aldridge, D.C. “Microplastics in freshwater systems: A review of the emerging threats, identification of knowledge gaps and prioritization of research needs,” Water Research, 75, 63-82 (2015).
2. Derraik, J.G.B. “The pollution of the marine environment by plastic debris: a review,” Marine Pollut. Bulletin, 44, 842-852 (2002).
3. P. Cherukupally et al. “Surface-engineered sponges for recovery of crude oil microdroplets from wastewater,” Nat. Sustain., 3, 136-143 (2020).
4. R.L. Coppock et al. “A small-scale, portable method for extracting microplastics from marine sediments,” Environ. Pollut., 230, 829-837 (2017).
5. Roh, S., Williams, A.H., Bang, R.S., Stoyanov, S.D., Velev, O.D. “Soft dendritic microparticles with unusual adhesion and structuring properties,” Nat. Mater., 18, 1315- 1320 (2019).

Background: Currently, hot-injection colloidal synthetic routes using batch reactors are used to prepare and study metal cation-doped perovskite quantum dots (PQDs). The high-temperature synthetic methods using batch reactors suffer from high overall energy costs, non-uniform heat distribution, and self-annealing of lead (Pb) halide PQDs.[1] Moreover, the manual flask-based colloidal synthesis technique results in high reagent consumption, high waste generation, and batch-to-batch inconsistency of products between syntheses, users, and different reactors.[1,2] In contrast, room-temperature post-synthetic metal cation doping is an effective synthetic strategy which prevents self-annealing phenomena and provides a higher level of process control, and thus facile synthesis of cation-doped Pb halide PQDs. Compared to batch reactors, droplet-based microfluidic synthesis strategies have been considered as reliable and precise tools for accelerated formulation discovery, fundamental studies, and large-scale manufacturing of high-quality colloidal PQDs.[1,2] Specifically, the reduced characteristic length scale of microfluidic reactors enables intensified and tunable mass and heat transfer rates that are challenging or in some cases impossible to achieve in batch reactors.[1]

Results: A modular flow chemistry platform was developed and utilized for accelerated in-flow studies of metal cation doping of a model all-inorganic PQDs, cesium lead chloride (CsPbCl3). The dynamics of doping the Mn2+ ions into the host CsPbCl3 QDs was monitored through a temporal in-situ spectral characterization enabled by a fully automated modular microfluidic platform. The Mn2+ doping level (Mn-to-exciton peak area ratio) and the emission color were tuned in-flow through a continuous flow dilution strategy. Different inflow-adjusted concentrations of Mn precursor justified different doping contents, and therefore provided controlled color tunability. Furthermore, we systematically studied the effect of dopant concentration (i.e., manganese chloride, MnCl2) and ligand composition on the extent and kinetics of the in-flow cation doping process.[3]

Conclusions: The developed modular microfluidic platform provides access to early-stage reaction time of colloidal PQDs to unravel the fundamental mechanism of an ultrafast cation doping process. The results of this study open new opportunities for on-demand continuous nanomanufacturing of high-quality cation-doped Pb halide PQDs for direct applications in next- generation photonic devices.

References:

1. K. Abdel-Latif, F. Bateni, S. Crouse, M. Abolhasani, “Flow Synthesis of Metal Halide Perovskite Quantum Dots: From Rapid Parameter Space Mapping to AI-Guided Modular Manufacturing”, Matter 2020, 3 (4), 1053– 1086.
2. Z. S. Campbell, F. Bateni, A. A. Volk, K. Abdel‐Latif, M. Abolhasani, “Microfluidic Synthesis of Semiconductor Materials: Toward Accelerated Materials Development in Flow”, Part. Part. Syst. Charact. 2020, 37
   (12), 2000256.
3. F. Bateni, R. W. Epps, K. Abdel-latif, R. Dargis, S. Han, A. A. Volk, M. Ramezani, T. Cai, O. Chen, M. Abolhasani, “Ultrafast Cation Doping of Perovskite Quantum Dots in Flow”, Matter. 2021, 4 (7), 2429-2447.

Background: Hydrogels are porous three-dimensional structures composed of polymeric cross-linked networks that has the provision for sufficient water and nutrient flow for cell proliferation to stimulate the regeneration of defective tissues. Compared to surgical scaffold implantation, injectable hydrogels can be easily applied by minimal invasive techniques to form a self-standing hydrogel. Naturally derived polymer, collagen, has been widely employed as injectable hydrogel since it inherits the structural and functional cursors to accelerate tissue formation, however it shows poor rheological properties. The use of biodegradable tannic acid particles provides a useful approach to improve the rheology of these systems while its inherent antibacterial and anticarcinogenic nature adds to gel functionality. Polyphenolic tannic acid particles could potentially interact with collagen through their hydroxyl and carboxyl groups allowing us to modulate the rheology.
Results: In this study, we examined how liquid as well as particulate tannic acids impact the rheological properties of collagen-based hydrogels. Liquid and tannic acid particles of different shapes are synthesized and incorporated into collagen in this regard. While samples exhibit solution-like features at storage conditions (4°C), they transform into gels under physiological temperatures (37°C). The sol-gel transition in terms of temperature and time is monitored as a function of tannic acid concentration and morphology. Interestingly, particulate tannic acid incorporation exhibits the largest increase in elastic modulus with shape playing a secondary factor. Measurement of yield stress using the elastic stress method also reveals a similar trend. These results are interpreted in terms of the underlying interactions of tannic acid with collagen, as examined using other analytic approaches.
Conclusions: The use of morphology-controlled tannic acid particles provides a facile approach to control the rheological characteristics of collagen hydrogel. In particular, changes in microstructure and cross-linking kinetics leads to hydrogels with enhanced modulus and yield stress while still preserving injectability. Results from this work could lead to the development of a new functional hybrid hydrogel system for use as injectables in tissue regeneration technology.

Background: DNA could enable a colossal technological leap for future digital data storage due to its high storage density, longevity [1], and energy efficiency [2]. A generic DNA-based information storage system includes database synthesizing, information accessing and reading. While previous research has focused on improving the efficiency of database synthesis and information reading, a key challenge remained as how to efficiently access a specific set of information from a large complex system. One must find solutions to how file-encoded DNA strands are copied, separated, and purified in the batch processes. Here, we propose to immobilize the DNA database on a very high surface area, high accessibility, 3-dimensional soft dendritic scaffold in a continuous packed-bed reactor. The new design would allow information to be copied and accessed by flowing reagents through the immobilized file-encoded strands.

Results: Soft dendritic colloids (SDCs) are formed through precipitating dissolved polymer in a turbulent flow of nonsolvent. Shear stress from the turbulence pull the precipitated microdroplets into a highly branched morphology with ultra-high surface area [3]. Magnetic nanoparticles are added to the dissolved polymer solution to make magnetic-responsive SDCs, which allows their remote manipulation and easy separation of SDCs from the liquid. Multiple chemical washes are performed to alter the surface of SDCs into binding sites for DNA strands. We observe both physical and chemical binding between SDCs and DNA strands. To quantify bound DNA strands, we use reverse transcription followed by real-time polymerase chain reaction.
Conclusions: In this research, we aimed to understand and control the efficiency of binding the file-encode DNA to the soft dendritic colloids (SDCs). This can be achieved by 1) incorporating magnetic nanoparticles into SDCs, 2) separating colloidal particles using a generic magnetic stand and 3) dispersing the SDCs in aqueous solutions and activating their surface with chemicals to allow binding of fluorescently labeled DNA. This work lays the foundation of developing a colloidal DNA-based storage system which has the potential to provide a cost-effective, energy-efficient, and long-lasting alternative at a time of rising concerns in global digital information storage.

References:

1. Bancroft C., Bowler T., Bloom B., and Clelland C. T. (2001). Long-term Storage of Information in DNA. Science 296(5536).
2. Zhirnov, V., Zadegan, R. M., Sandhu, G. S., Church, G. M. & Hughes, W. L. (2016). Nucleic acid memory.Nat. Mater. 15, 366–370.
3. Roh, S., Williams, A. H., Bang, R. S., Stoyanov, S. D. & Velev, O. D. (2019). Soft dendritic microparticles with unusual adhesion and structuring properties. Nat. Mater. 18, 1315–1320.

Background: Active particles can “self-propel” on the microscale, by drawing energy from their environment to power their motion. These particles offer innovative solutions to many current challenges in the biomedical field, such as targeted drug delivery and selective micro-scale surgeries, as well as environmental remediation and nanofabrication. Their main feature enabling self-motion is the principle of breaking symmetry to create a localized gradient, whether it be physical or chemical. A variety of methods to induce this self-propulsion have been explored, including stimulation by magnetic,[1-3] electric, acoustic, optical, biological, and chemical[4] means. Despite these strides, the field of active particles faces the ongoing challenge of using new principles and functionalities. Here we present two new concepts: (1) asymmetric alternating current (AC) field propulsion that would grant multiple new degrees of freedom and (2) creating novel osmotically-driven ultra-simple superdiffusive paste made from salt particles.
Results: First, we present the findings for an asymmetric AC field-driven active system by characterizing particle velocity as a function of frequency, voltage, and size. Through our results, we reveal a new AC electrohydrodynamic effect in which spatially homogenous, temporally non-uniform signals drive colinear particle motion with respect to the electric field. By modifying the asymmetry of the AC signal, latex particles can multimodally change their direction of motion on demand. In the second project, we reveal a superdiffusive paste that demonstrates collective dispersal of rapidly dissolving particles. We found that the radial dispersion is driven by osmotic propulsion, created by the solute concentration gradients formed by the dissolution of salt particles. Thus far, we have observed dissolving particles of NH5CO3, NaCl, and NaHCO3 actively propelling radially to the respective dispensed paste bolus when released in acidic solution. The rate of particle dispersion is tunable by moderating the pH of the surrounding medium. These active ionic salt particles are able to move up to astonishingly rapid speeds of 2.2 mm/sec.
Conclusions: Both of these projects could have a transformative impact on the field of active particles by answering fundamental questions on the role of AC-EHD effects, collective gradient-driven phenomena, and the rational design of active particle systems. Our fundamental work on the superdiffusive paste has potential to be transplanted to novel biomedical disinfection products for efficient in-vivo treatment of microbes in teeth and wounds. Through our interdisciplinary research, we aim to expand the knowledge boundaries in this rapidly developing research field.

References:

1. S. Gangwal, O. J. Cayre, M. Z. Bazant and O. D. Velev, Phys. Rev. Lett., 100, 058302 (2008). Induced-Charge Electrophoresis of Metallodielectric Particles.
2. C. W. Shields, K. Han, F. Ma, T. Miloh, G. Yossifon and O. D. Velev, Adv. Funct. Mater., 28, 1803465 (2018). Supercolloidal Spinners: Complex Active Particles for Electrically Powered and Switchable Rotation.
3. R. Sharma and O. D. Velev, Adv. Funct. Mater. 25, 5512–5519 (2015). Remote Steering of Self-Propelling Microcircuits by Modulated Electric Field.
4. W. F. Paxton, A. Sen and T. E. Mallouk, Chem.–Eur. J., 11, 6462–6470 (2005). Motility of Catalytic Nanoparticles through Self-Generated Forces.

Background: The monitoring of human health and well-being with the use of wearables is the core of the next generation of biomedical devices. Sweat provides a facile source for the continuous and non-invasive measurements of biomarkers. Despite its advantages, sweat biomarker analysis is still challenging because most of the commercially available health-monitoring devices are either semi-invasive in nature (iontophoresis) or operate only during active sweating [1]. Microfluidic platforms integrated with colorimetric sensors have been used for collection, capture, storage, and analysis of sweat. The designs are simple, versatile, and cost-effective, which opens a broad range of their applications in point of care (POC) diagnostics. Lateral flow assay (LFA) based POC diagnostics have gained increased attention in quantitative and qualitative analysis due to their prompt and rapid results. We have developed simple, wearable, inexpensive, non-invasive, and zero-power paper microfluidic based skin patch LFAs for detection of potassium (K+) and cortisol in sweat. Our patch consists of a hydrogel which is equilibrated with a highly concentrated solution and is responsible for pumping sweat from skin due to osmotic pressure difference [2]. This allows the patch to function under sedentary as well as active sweating conditions.

Results: In-vitro trials using gelatin-based model skin indicate that 4M glucose hydrogels were most efficient in sampling maximal sweat volume with higher precision. Benchtop experiments revealed that we could successfully sample and enable colorimetric detection of K+ in 90 mins. Human trial results reveal that average concentration of potassium measured by the patch on multiple subjects matched well with literature data. The potassium concentration was independent of the sweat rate and possessed a possible positive correlation with the blood potassium levels. The patch was further modified for on-body testing at rest, to enable colorimetric detection at low sweat volume (during rest). The major advantage of this patch is that it can operate on extremely low volumes of sweat (~2-3 μL). That is at least 10× less than what other potassium sensors have reported previously. Preliminary results show that the integration of a cortisol LFA with osmotic platform can sample and detect cortisol, but it needs more calibration and optimization.
Conclusions: The non-invasive wearable patches that we have developed can eliminate the need to rush to medical centers for biomarker-based diagnostics. Such simple and inexpensive patches could allow numerous opportunities for at-home or in-field POC diagnostics.

References:

1. Legner, C.; Kalwa, U.; Patel, V.; Chesmore, A.; Pandey, S. Sweat Sensing in the Smart Wearables Era: Towards Integrative, Multifunctional and Body-Compliant Perspiration Analysis. Sens. Actuators Phys. 2019, 296, 200–221.
2. Saha, T.; Fang, J.; Mukherjee, S.; Dickey, M. D.; Velev, O. D. Wearable Osmotic-Capillary Patch for Prolonged Sweat Harvesting and Sensing. ACS Appl. Mater. Interfaces 2021, 13, 8071–8081.

Background: Plastic waste has been posing an alarming threat to the environment and human health with most of it being discarded in the ocean and accumulating within the food chain. The design of an eco-friendly, biodegradable plastic replacement is becoming more urgent than ever. Using natural biomass resources to develop alternatives to petrochemical plastic films represents an attractive opportunity due to their abundance, low cost, and favorable biodegradability. However, the use of sustainable substitutes of synthetic polymer is still limited by the inferior mechanical strength and low stability against water [1]. Here, we report a facile and sustainable strategy to reinforce polysaccharide films using a new class of dendritic colloidal particles [2]. These particles offer a nano- and microscale hierarchy to the films, as well as a network of hydrogen bonds, resulting in a remarkable increase in the mechanical properties and the wet film stability.
Results: Due to the high interfacial area, the large excluded volume, and strong van der Waals interactions, the soft dendritic colloids (SDC) have excellent structure building properties. We developed agarose biopolymer films reinforced with SDC made from chitosan (CS), which is the second most abundant biopolymer in nature. The composite films showed synergistic functional properties due to the inclusion of CS SDC, where the film’s toughness showed a 4-fold increase compared to the pure agarose film. Due to intermolecular interactions between the biopolymers as well as nanoscale fibrous entanglement between the SDC, the films acquired a hydrophobic nature and an increased water stability. Other important film functional properties such as water vapor permeability, hydrophobicity, and rheological properties have also been characterized.

Conclusions: We have developed a new class of all-natural, biodegradable films made from biopolymers that have superior or comparable properties to petroleum-based plastic films. The reinforcing strategy based on SDC inclusion represents an innovative design strategy for fully biodegradable and robust films that have integrated strength and toughness. The biopolymer film showed synergistic properties upon SDC addition in the matrix. We are currently investigating the fundamentals governing the intermolecular interactions between the film’s components and the exact reinforcing mechanism.

References:

1. X. Zhang, W. Liu, D. Yang, X. Qiu, Biomimetic Supertough and Strong Biodegradable Polymeric Materials with Improved Thermal Properties and Excellent UV-Blocking Performance, Adv. Funct. Mater. 29 (2019). https://doi.org/10.1002/adfm.201806912.
2. S. Roh, A.H. Williams, R.S. Bang, S.D. Stoyanov, O.D. Velev, Soft dendritic microparticles with unusual adhesion and structuring properties, Nat. Mater. (2019). https://doi.org/10.1038/s41563-019-0508-z.

Background: Surface-anchored polymer coatings with controllable surface properties have drawn attention due to its broad applicability in various fields, including soft electronics, drug delivery, microfluidics, and biotechnology. UV- or thermally-active cross-linkable groups are incorporated into the precursor polymer to trigger the crosslinking and surface attachment reaction.[1] However, the conventional method has some limitations, which require specific functional groups inside the polymers and multiple fabrication steps to generate surface-anchored polymer networks. Here we use a versatile and straightforward one-pot synthesis method to make surface-anchored polymer networks by using thermally active functional small molecular gelators (FSMGs).[2] The sulfonyl azide (SAz) tail group and triethoxysilane headgroup group in 6-azidosulfonylhexyltriethoxysilane (6-ASHTES) generate a simultaneous crosslinking and a surface attachment of the polymer network to the substrate.
Results: We studied the formation of surface-anchored polymer network by using poly(vinyl pyrrolidone) (PVP) with various molecular weights and 6-ASHTES amounts. We deposited thin films (thickness d) of PVP/6-ASHTES mixture onto a silicon substrate by dip-coating and annealed them at 120, 130, and 140°C for the desired time. The films were extracted in methanol, and ellipsometry measured the film thickness d0. The gel fraction (Pgel), which is the insoluble fraction of polymer in the network, was determined as Pgel=d/d0. Pgel increased with increasing the concentration of 6-ASHTES (x), annealing temperature (T), and annealing time (t). We have demonstrated that Pgel can be controlled independently by varying x, T, and t. We have produced master plots for Pgel that confirm the x-T-t superposition. Also, we studied the swelling behavior of polymer gel with various molecular weights of PVP and concentrations of 6-ASHTES. The swelling ratio increased with an increased average molecular weight between crosslinks (i.e., decreased crosslink density).
Conclusions: In this study, we investigated a one-pot synthesis to generate the surface-anchored polymer network using 6-ASHTES gelator. We studied gel fraction and swelling ratio to determine the effects of the molecular weight of PVP, annealing time, and temperature on the reaction kinetics of the surface-anchored polymer network. Further development on the surface-anchored polymer network would result in successful adaptation in the biomedical industry.

References:

1. Pandiyarajan, C. K.; Rubinstein, M.; Genzer, J. (2016). Surface-Anchored Poly(N -Isopropylacrylamide) Orthogonal Gradient Networks. Macromolecules, 49: 5076−5083.
2. Pandiyarajan, C. K., & Genzer, J. (2019). Thermally Activated One-Pot, Simultaneous Radical and Condensation Reactions Generate Surface-Anchored Network Layers from Common Polymers. Macromolecules, 52(2): 700-707.

Background: Increased awareness of the long-term impacts of agrochemicals has resulted in the hunt for efficient and sustainable delivery platforms. In order to meet the food demands of an exponentially increasing global population, there is a dire need to establish sustainable technologies for targeted and slow release of agrochemicals with minimal environmental footprints. Furthermore, rising concerns of the global community about the accumulation and environmental effects of microplastics have accelerated the search for alternate delivery vehicles developed from biodegradable polymers [1, 2, 3]. We present a sustainable approach to synthesize aqueous dispersions of biodegradable cellulose derivatives via anti-solvent precipitation. We propose utilization of these dispersions as controlled and targeted release foliar spray formulations for a pesticide as a model active ingredient (AI). While biodegradable nature of our polymer particles and use of water as the dispersant medium justify sustainable nature of these formulations, the adaptability of the dispersions to cater to a range of crops and AI is exhibited through modulation of the particle shape and size through using three types of cellulose derivatives. Additionally, we have used Isothermal Titration Calorimetry (ITC) to investigate the nature of polymer interactions with the AI to provide a comprehensive picture of the performance and tenability of the formulations.
Results: Results of the study demonstrate the efficacy of the formulations for foliar AI applications. Enhanced adhesion of the dispersions on model leaf substrates under a simulated rain test signify the superior rain fastness of the formulation, while in-vitro fungal assays show the increased bio-availability of the AI due to loading on the cellulose derivative particles. The effect of particle size and morphology on AI bonding strength and release is corroborated through Isothermal Titration Calorimetry (ITC) analysis and release assays.
Conclusions: The simplicity and sustainability of the approach combined with the potential to significantly lower AI application rates for achieving the desired pest protection shows the promise of the technique to significantly impact global food security while mitigating environmental concerns related to pesticide overuse.

References:

1. Pirzada T, de Farias B V., Mathew R, et al (2020). Recent advances in biodegradable matrices for active ingredient release in crop protection: Towards attaining sustainability in agriculture. Curr Opin Colloid Interface Sci., 48:121-136.
2. Colin T, Monchanin C, Lihoreau M, Barron AB (2020). Pesticide dosing must be guided by ecological principles. Nat Ecol Evol., 4:1575–1577.
3. Zhao X, Cui H, Wang Y, Sun C, Cui B, Zeng Z (2018). Development Strategies and Prospects of Nano-based Smart Pesticide Formulation. J Agric Food Chem., 66(26):6504-6512.

Background: From the first introduction of silica aerogel in 1930 to the most recent aerogels constructed from several organic and inorganic materials, design and fabrication of aerogels have been improved.[1,2] Conventional aerogels are fabricated via solvent removal from a gelatinous network which is typically an expensive and time-consuming process involving multiple solvent exchanges. Additionally, conventional aerogels contain weak interconnected networks within their structure resulting in lack of mechanical flexibility and strength that inhibit their functionality.[3] Recently, nanofibrous aerogels (NFAs) have started getting attention because of their straightforward and robust method of preparation. NFAs are prepared by freeze drying a dispersion of short nanofibers in a non-solvent.[4,5] Synthesis of NFAs provide a flexible platform for creating nanofiber-based functional materials from vast variety of organic and inorganic materials. We present a sustainable approach to fabricate a mechanically robust and photo-responsive aerogel from sol-gel electrospun Polyvinylpyrrolidone (PVP)-Titania (TiO2) nanofibers.
Results: Ultralight (⁓ 10 mg cm-1) and hierarchically porous (> 99%) NFA constructed from electrospun PVP-TiO2 nanofibers. Morphology of the aerogel analyzed using Scanning Electron Microscopy (SEM) and confocal laser scanning microscope while Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS) studies demonstrate a homogeneous distribution of TiO2 in the structure of the aerogel. Furthermore, Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of typical Ti-O-Ti, Ti-OH functional groups to confirm presence of TiO2 while appearance of bands showing Ti-O-C indicate chemical interactions between TiO2 and PVP that arise during sol-gel processing. Owing to the photocatalytic activity of TiO2, the aerogel exhibits antibacterial properties for gram-negative bacteria (i.e., E-coli and Salmonella). The aerogel also exhibits very low thermal conductivity and high mechanical flexibility which are advantageous for a host of applications.
Conclusions: In this work, we have successfully developed a robust methodology to construct ultralight, hierarchically porous, mechanically strong, and multifunctional aerogels designed from sol-gel electrospun PVP-TiO2 nanofibers. As expected, TiO2 played an essential role in improving both the mechanical and functional properties of the aerogel. Crosslinking between TiO2 and PVP is verified via appearances of Ti-O-C bands in the FTIR spectra of the hybrid fibers. PVP-TiO2 NFA exhibit antibacterial properties, low thermal conductivity and high mechanical properties that makes it a promising candidate for a wide range of applications.

References:

1. S. S. Kistler, J. Phys. Chem. 1932, 36, 52.
2. Y. Si, J. Yu, X. Tang, J. Ge, B. Ding, Nat. Commun. 2014, 5, 5802.
3. A. Soleimani Dorcheh, M. H. Abbasi, J. Mater. Process. Technol. 2008, 199, 10.
4. T. Pirzada, Z. Ashrafi, W. Xie, S. A. Khan, Adv. Funct. Mater. 2020, 30, 1907359.
5. F. Deuber, S. Mousavi, L. Federer, C. Adlhart, Adv. Mater. Interfaces 2017, 4, 1700065.

Background: Bisphenol A (BPA)-based epoxies constitute over 95% of the food and beverage can coatings owing to their high corrosion resistance and strong adhesion to the metal oxide substrates [1]. However, legal pressures and health concerns over BPA have prompted the industry to target alternative coatings that have often struggled to replicate the strong adhesion offered by the epoxies [2]. An understanding of the molecular origins of adhesion in terms of the epoxy resin structure and the surface chemistry of the metal oxide substrate is critical for rational design of alternative coating formulations. Experimentally probing the thermodynamics of the epoxy resin-metal oxide adsorption process, especially the energetic contributions from specific interactions such as H-bonding, electrostatic or van der Waals forces (enthalpic, ∆H<0) and those arising due to dynamic confirmational changes upon binding (entropic), can help identify the structural determinants to optimize polymer-metal oxide adhesion.
Results: Using isothermal titration calorimetry (ITC), we explore the adsorption mechanism and associated thermodynamic profile (ΔG, ΔH, TΔS) of a homologous series of BPA-based epoxy resins with increasing number of pendant -OH groups in its backbone in a DMF-ethanol solvent media with three metal oxide particles – SnO2, Al2O3 and Cr2O3, with decreasing concentration of surface -OH groups (sOH) in that order. Epoxy resin-metal oxide interfacial interactions were found to be entropically-dominant, likely due to re-organization of the solvent molecules upon binding (|T∆S|>|∆H|), and favorable across all combinations with ΔGavg= -19 ± 0.3 kJ/mol. In the absence of pendant -OH groups on the resin and low sOH concentration, the adsorption was enthalpically unfavorable and purely entropy-driven, possibly through the dispersive sOH-π interactions between the hydrophobic benzene rings of the resin and the sOH groups [3]. With increasing sOH concentration and number of pendant -OH groups, adsorption was also enthalpically favorable, likely via H-bonding between sOH and the pendant -OH groups [4].
Conclusions: Investigation of the binding mechanism reveal that the dispersive OH-π interactions through the hydrophobic portion of the epoxy resin structure may play a dominant role in dictating the overall entropy-driven adsorption in comparison to the enthalpically favorable specific H-bonding through the pendant -OH groups. ITC can, thus, provide key mechanistic insights critical for the rational design of BPA-free can coating formulations.

References:

1. LaKind, J. S. (2013) Can Coatings for Foods and Beverages: Issues and Options. Int. J. Technol. Policy Manag. 13: 80-95.
2. Soto, A. M.; Schaeberle, C.; Maier, M. S.; Sonnenschein, C. and Maffini, M.V. (2017) Evidence of Absence: Estrogenicity Assessment of a New Food-Contact Coating and the Bisphenol Used in Its Synthesis. Environ. Sci. Technol. 51:1718–1726.
3. Nakamura, S.; Tsuji, Y. and Yoshizawa, K. (2020) Role of Hydrogen-Bonding and OH−π Interactions in the Adhesion of Epoxy Resin on Hydrophilic Surfaces. ACS Omega. 5:26211–26219.
4. Semoto, T.; Tsuji, Y. and Yoshizawa, K. (2011) Molecular Understanding of the Adhesive Force between a Metal Oxide Surface and an Epoxy Resin. J. Phys. Chem. C. 115: 11701–11708.

Background: Soft nanomaterials make up many products in modern society and find application in rheological modifiers, structural enhancers, nonwovens, and health care products [1]. Thus, the development of an efficient and scalable nanomaterial fabrication technique is a hot topic in both fundamental and applied science. While there are conventional techniques that can produce certain morphologies, they may be inefficient and may not be capable of fabricating a wide range of structures or finer details. Our group has developed a versatile liquid shear-based nanofabrication technique which combines key concepts from nonsolvent-induced phase separation with interfacial polymer precipitation. In this process, polymer solution is injected into a sheared bulk medium. There is ultralow miscibility between the polymer solution and the nonsolvent medium, allowing for extreme interfacial deformation by the fluid streamlines as the polymer precipitates [2]. Previously, we have shown this method is capable of producing rods and fibers in laminar flow and more complex dendritic structures and sheets in turbulent flows [2, 3]. Here, we present a systematic approach in determining the fabrication outcomes by developing a simple three-stage model.
Results: The three-stage model that can effectively describe all feasible operational conditions and their outcomes consists of three stages: 1. Hydrodynamic shear, 2. Capillary stability and mechanical instability, and 3. Precipitation rate. When we divide the stages into two or three subcategories, we get twelve combinations of operational conditions which each produce a unique colloidal morphology. Typically, laminar flows produce simple “one-dimensional” structures such as rods, fibers and ribbons whereas turbulent flows can produce hierarchical structures similar to their multiscale vortices. The capillary stability primarily determines the jetting to dripping transition of the injected polymer solution within laminar flows which drastically changes the outcome from fibers to spherical particles. The degree of mechanical entanglement in the precipitated polymer determines whether the polymer will undergo secondary fragmentation which can reduce their aspect ratios. The final stage concerns the precipitation rate which changes the timescale at which the polymer can be manipulated by shear.
Conclusions: The systematic investigation into the liquid shear-based nanofabrication technique revealed a plethora of colloidal morphologies. By simply varying the process conditions of the three operational stages, we have demonstrated that twelve unique structures can be made out of a single polymer. This technique is versatile, capable of being applied to a variety of other polymer systems. This investigation may help introduce a new family of liquid manufacturing technologies.

References:

1. Phillips, K. R. et al. A colloidoscope of colloid-based porous materials and their uses. Chem. Soc. Rev. 45, 281–322 (2016).
2. Roh, S., Williams, A.H., Bang, R.S., Stoyanov, S.D., Velev, O.D. “Soft dendritic microparticles with unusual adhesion and structuring properties,” Nat. Mater., 18, 1315-1320 (2019).
3. Smoukov, S. K. et al. Scalable liquid shear-driven fabrication of polymer nanofibers. Adv. Mater. 27, 2642–2647 (2015).

Background:Microfibers are an essential, everyday material. Most products that people use daily, such as filters, chairs, and clothes, are made from microfibers. Microfibers are often produced by using bicomponent polymer systems. The materials of choice in these bicomponent systems are poly(ethylene terephthalate) (PET) and Nylon 6 (PA6). This combination of PET and PA6 is preferable because of its beneficial attributes (i.e., thermal stability, mechanical strength, etc.). However, PET and PA6 exhibit high mutual adhesion at elevated temperatures due to chemical bonds formation by aminolysis of the ester group in PET with a secondary amine in PA6. It is desirable to have adhesion between the materials that is not too strong to separate the PET and PA6 materials at a relatively low energy cost. Concurrently, the adhesion must be strong enough for good mechanical properties of the final product. Therefore, we are developing methods for tailoring the adhesion at the PET/PA6 interface by adding modifiers that react preferentially with the PA6 component. We study the reactivity of ester groups in PET with secondary amines using a series of small molecules (i.e., caprolactam, diallyamine, diethylamine, and diisopropylamine). Afterward, the feasibility of modifying secondary amines is examined by reacting the two modifiers poly(styrene-alt-maleic anhydride) (PSMA) and poly(octadecene-alt-maleic anhydride) (POMA) with series of small molecules containing secondary amine groups. Next, the modification of PA6 with the PSMA and POMA is investigated. Lastly, the adhesion strength between PA6 and PET and modified PA6 and PET is assessed.

Results: The reaction between PET and a series of small molecules containing secondary amine groups shows a bond between the ester and secondary amine groups. Additionally, the series of small molecules containing secondary amine groups react with PSMA and POMA, and similarly, PA6 also reacts with the two modifiers. PA6 and PET display high fracture toughness (i.e., adhesion strength) at elevated temperatures and longer annealing times. Lastly, both modifiers result in reduced interfacial adhesion strength between PET and PA6.
Conclusions: Overall, we established strong adhesion between PET and PA6 because of the possible strong interactions between the ester group and amine group in PET and PA6, respectively. PA6 modified with POMA had a greater reduction in adhesion strength in a PA6/PET system than PA6 modified with PSMA. The “C18 motif” present in the POMA may block ester (in PET) and/or secondary amines (in PA6), thereby decreasing adhesion strength. Therefore, based on our studies, it is feasible to tailor adhesion at the PET/PA6 interface, which could prove to be useful in the microfibers production.

Background: Due to their toughness and extensibility, thermoplastic elastomers (TPEs) are beneficial for a number of applications such as medical devices, automotive parts, and consumer goods. Poly[styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) is a TPE consisting of rigid S endblocks and a soft EB midblock. Because of the thermodynamic incompatibility between the covalently-linked blocks, these copolymers are capable of spontaneously self-organizing into a variety of nanoscale morphologies such as spheres, cylinders and lamellae, as well as more complex ones, that regulate copolymer properties [1]. One approach by which to control the mechanical properties of TPEs is through the physical incorporation of a low-volatility midblock-selective oil. Such materials, collectively known as TPE gels (TPEGs), display highly adjustable properties that make them attractive in a plethora of applications. Most of the TPEs employed for this purpose derive from styrenic TPEs with a polyolefin midblock that can be selectively swollen with an aliphatic oil. In most instances, TPEGs are processed as cast films or extrudates [2]. Here, we consider the preparation of highly tunable TPEG microfibers via electrospinning. Electrospun nano/microfibers can be used to fabricate nonwovens and are appealing because they can be easily generated at ambient temperature. As highly porous mats, these materials are suitable for filtration and medical products. In the specific case of electrospinning TPEGs, process parameters and the oil loading level affect morphology and, in turn, the properties of the microfibers. Our goal here is to produce highly stretchable nonwovens from styrenic TPEGs.
Results: A series of commercial SEBS copolymers possessing different molecular weights and S content have been first used to establish their structure-property-processing relationships during electrospinning. Prior to electrospinning TPEGs, we first discern the electrospinning solution concentration at which TPE fibers can be formed. These observations are quantitatively related to the critical chain overlap concentration, c*, which was experimentally ascertained for each copolymer examined here. A plot of specific viscosity versus concentration (c) normalized relative to c* clearly differentiates three solution regimes: dilute (c/c*<1), semidilute unentangled (1<c/c*<3) and semidilute entangled (c/c*>3). Uniform copolymer fibers are acquired at c/c*~4 for all the copolymers varying in molecular weight. The effect of chain length on electrospinning is effectively eliminated once the concentration is normalized with respect to c*, and the fiber diameter is found to universally scale as (c/c*) 2.5.

Conclusions: This work is anticipated to enable fabrication of highly stretchable nonwovens that can improve comfort in current products and introduce potentially new applications in the not-too-distant future.

References:

1. Matsen, M. W. Effect of Architecture on the Phase Behavior of AB-Type Block Copolymer Melts. Macromolecules (2012), 45, 2161–2165.
2. Armstrong DP, Mineart KP, Lee B, Spontak RJ. Olefinic Thermoplastic Elastomer Gels: Combining Polymer Crystallization and Microphase Separation in a Selective Solvent. ACS Macro Lett. (2016) Nov 15;5(11):1273–7.

Background: Contact electrification or triboelectricity is a charging phenomenon when two materials are brought into contact and pulled apart. Contact electrification was first discovered in ~360 BC by Plato, yet it remains poorly understood due to charges having a stochastic nature, which makes it hard to interpret [1]. One of the unsolved issues in contact electrification is to understand charge dissipation after the charging. Charge on insulator decays naturally due to the breakdown caused by air and moisture, but the control of charge dissipation remains puzzled [2]. Understanding charge dissipation is important for improving air filtration efficiency because the charge on a filter media could capture the micro-sized particles. A recent study employed vibration from a vehicle to generate contact electrification to filter exhaust gas, but it mainly focused on charge generation, not charge longevity [3]. Here, we characterize charge decay on a needle- punched nonwoven fabric after charging and compare this with air filtration efficiency.

Results: Charge decay was characterized by measuring charges on pre-charged nonwoven with periodic contact to an electrode. This method demonstrated reproducible charge decay with the same condition. The charge on nonwovens decayed two-step process: fast decay in first ~2 h and slow decay in the rest of the time, which might be due to two different types of charge generated on the surface [4]. After charging on the needle-punched nonwovens by rubbing with aluminum foil, filtration efficiency increased by ~13% without any change in pressure drop and this was maintained at least 210 min. To simulate the charge distribution inside the fabric, we used Kelvin Probe Force Microscopy (KPFM) to map the surface potential. KPFM was validated by measuring surface potential on different silane layers on Si wafers, which shows clear surface potential change after the surface modification. With KPFM, we confirmed different signs of charges generate inside the needle-punched nonwovens, indicating that the filtration efficiency of the nonwovens is maintained even if the surface charge decays.
Conclusions: Contact electrification improved the filtration efficiency of micro-sized (0.3 μm) particles due to electrostatic interaction. We will try to understand the correlation between charge decay on the filter media and filtration efficiency.

References:

1. Lacks, Daniel, and Troy Shinbrot (2019). Long-standing and unresolved issues in triboelectric charging. Nat. Rev. Chem., 3: 465–476.
2. McCarty, Logan, and George M. Whitesides (2008). Electrostatic charging due to separation of ions at interfaces: contact electrification of ionic electrets. Angew. Chem. Int. Ed., 47: 2188–2207.
3. Han, Chang Bao, Tao Jiang, Chi Zhang, Xiaohui Li, Chaoying Zhang, Xia Cao, and Zhong Lin Wang (2015). Removal of particulate matter emissions from a vehicle using a self-powered triboelectric filter. ACS Nano, 9: 12552–12561.
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Background: The Li-ion battery has dominated the energy storage industry since its commercialization in the early 1990’s. The high energy density and low self-discharge rate of Li-ion cells has enabled their capture of the portable power market. However, the components within Li-ion batteries remain largely unchanged over the last 30 years. To keep up with evolving quantity and performance demands of the market, Li-ion battery technology and manufacturing techniques must evolve. A novel morphology of polymer particles known as soft dendritic colloids (SDCs) was discovered by the Velev group at North Carolina State University [1]. These high- aspect ratio particles are manufactured by a facile shear-driven solvent/non-solvent induced phase separation method. The high surface area and entanglement make these structures an ideal candidate for electrochemical systems, which rely on efficient surface phenomena. Herein we report applications of these structures in both Li-ion battery separators and electrodes.
Results: Three different morphologies of SDCs were formed by varying the concentration of the injected polymer, poly(vinylidene difluoride) (PVDF). Each of these three unique morphologies were vacuum filtered to form fibrous and highly porous battery separators. The SDC non-woven separators showed far superior electrolyte uptake and ionic conductivity compared to their commercial analogues as well as comparable cycling stability in Li-ion half cells.

SDCs were also formed out of redox active polymers (e.g. poly(2,2,6,6-tetramethyl- piperidenyloxyl-4-yl methacrylate) (PTMA)) to form composite electrodes with carbon material. Optical and electron micrographs confirm the branched morphology of the electrodes. Charge- discharge and impedance experiments are carried out in Li-ion half cells with results presented in the poster.
Conclusions: This project illustrates how SDCs can be used to fabricate improved electrochemical device components, including but not limited to the electrodes and the separators. Shear-driven solvent/non-solvent induced phase separation is also demonstrated as an all-in-one manufacturing platform for Li-ion battery components.

References:

1. Roh, S., Williams, A.H., Bang, R.S., Stoyanov, S.D., Velev, O.D. “Soft dendritic microparticles with unusual adhesion and structuring properties,” Nat. Mater., 18, 1315- 1320 (2019).
2. Luiso, S.; Williams, A. H.; Petrecca, M. J.; Roh, S.; Velev, O. D.; Fedkiw, P. S.. Journal of The Electrochemical Society 2021, 168 (2), 020517.