2018 Schoenborn Graduate Research Symposium

January 22, 2018

Continental Breakfast 8:15 – 8:45 AM

Opening Remarks 8:45 AM


Oral Presentations 8:50-10:30 AM


 8:50 AM Adam Mischler
Background Specification of the inner cell mass (ICM) and the trophectoderm (TE) is the first major differentiation event in the developing human embryo. [1] The ICM ultimately forms the developing fetus while TE gives rise to the major trophoblast (TB) cell types of the placenta – the villous cytotrophoblasts (vCTBs); syncytiotrophoblast (STB); and the extravillous cytotrophoblasts (EVTs), which comprise the column cytotrophoblast (cCTB) and invasive cytotrophoblast (iCTBs). Our understanding of human TB differentiation and early placental development is limited due to ethical and regulatory constraints on research with human embryos, limited availability of primary tissue samples from early gestation, and lack of a suitable in vitro model system. In this context, TBs derived from human embryonic stem cells (hESCs) emerged as an attractive system for mechanistic studies on TB development.
Results:Previous studies in our group have shown that the activin/nodal signaling pathway plays an important role in the terminal fate specification of hESC-derived TB. [2] Here we expand upon this work to develop a completely defined and serum free culture system for generation of bona fide TB from hESCs. We show that the bioactive phospholipid Sphingosine-1-Phosphate (S1P) is required for generation of TB in hESCs in the absence of serum. Furthermore, we show that both Rho/ROCK signaling and activation of Yes-associated Protein (YAP) are required for establishment of bona fide TB from hESCs.
Conclusions:Significantly, this system elucidates the signaling pathways for determining TB fate and the role of lipid-mediated signaling in TB specification from hESCs. This media system provides an attractive new way of studying bona fide TB and deliver new insights to TB differentiation and development.
1. Lee CQE, Lucy Gardner, Margherita Turco, Nancy Zhao, Matthew Murray, Nicholas Coleman, Janet Rossant, Myriam Hemberger, and Ashley Moffett. (2016) What Is Trophoblast? A Combination of Criteria Define Human First-Trimester Trophoblast. Stem Cell Reports, 6(2):257-72.
2. Sarkar Prasenjit, Shan Randall, Timothy Collier, Anthony Nero, Teal Russel, David Muddiman, Balaji Rao. (2015) Activin/Nodal Signaling Switches the Terminal Fate of Human Embryonic Stem Cell-derived Trophoblasts. J Biol Chem, 290(14):8834-8848.
 9:10 AM Shah Md Toufiqur Rahman
Background: Differential activation of ERK, JNK, and p38 mitogen activated protein kinases (MAPKs) is central to cellular decisions ranging from cell cycle progression to apoptosis. In this study, we use an optogenetic and live-cell imaging approach to selectively and acutely activate individual kinases and dissect cross-regulation of MAPKs and its determination of cell responses.
Results:Focusing on the MAPK kinase, MKK6, photo-uncaging (Gautier, Deiters, & Chin, 2011) constitutively active MKK6 activates isoforms of the stress-activated MAPK p38 subfamily but not JNKs, consistent with prior literature (Raingeaud, Whitmarsh, Barrett, Derijard, & Davis, 1996). Uncaging MKK6 strongly inhibits basal and growth factor stimulated ERK activity, but surprisingly this negative crosstalk is not affected by pharmacological inhibition of p38 nor shRNA depletion of p38alpha, both of which ablate MKK6-mediated p38 kinase activity in our cells. We also show that photo-activation of MKK6 is sufficient to induce caspase-3 activity and release of cytochrome C from mitochondria, hallmarks of apoptosis. The course of MKK6-induced apoptosis is accelerated when type IA phosphoinositide 3-kinases are inhibited; notably, MKK6-induced apoptosis still occurs when p38 kinase activity is inhibited, but in a smaller fraction of cells.
Conclusions: The optical control over the catalytic activity of protein kinases serves as a general probing tools for studying cell-signaling networks and the results obtained in this study shed light on the crosstalk between MAPK signaling cascades and their role in cell fate decisions.
1. Gautier, A., Deiters, A., & Chin, J. W. (2011). Light-activated kinases enable temporal dissection of signaling networks in living cells. Journal of the American Chemical Society, 133(7), 2124-2127.
2. Raingeaud, J., Whitmarsh, A. J., Barrett, T., Derijard, B., & Davis, R. J. (1996). MKK3- and MKK6- regulated gene expression is mediated by the p38 mitogen-activated protein kinase signal transduction pathway. Molecular and Cellular Biology, 16(3), 1247 1255.
9:30 AM Laura L. Lee
Background: Extremely thermophilic microorganisms have a promising, but yet unrealized, role to play in the deconstruction of lignocellulose for the production of bio-based fuels and chemicals. The bacterial genus Caldicellulosiruptor contains unique species that are incredibly talented at breaking down untreated biomass: a key ability for prospective consolidated bioprocessing. The most strongly cellulolytic species of this genus possess novel proteins with synergistic catalytic and binding capabilities that allow them to precisely target cellulosic substrates. To further pursue these microbes’ potential for lignocellulose degradation, specific genes and proteins have been investigated in multiple species to further characterize ‘Caldi World’.
Results: Both individual species and environmental communities were used to re-assess genus- wide biodiversity for the extremely thermophilic Caldicellulosiruptor genus [1]. The overall genus’s protein inventory includes a variety of multi-domain carbohydrate active enzymes (CAZymes), some of which are co-located in a conserved genomic region in nearly all species and are specific determinants for crystalline cellulose utilization. Three recently sequenced Caldicellulosiruptor species, Rt8.B8, NA10, & Wai35.B1 [2], have increased our understanding of this enzymatic inventory, and added completely new CAZymes to those previously found in this genus. When tested on microcrystalline cellulose and complex biomass, Rt8.B8 exceeded the degradation abilities of previously-tested highly cellulolytic species and potentially represents a new ideal species for biomass bioprocessing and genetic modification. Additionally, analysis of cellulose-enriched environmental samples from Yellowstone National Park revealed new information for genus biodiversity, yielding genomic signatures closely related to known Caldicellulosiruptor but also evidence for other thermophilic fermentative anaerobes. One enrichment actually had the highest capacity for lignocellulose solubilization, comparable to the Rt8.B8 isolate. Finally novel proteins (tāpirins) [3] were identified via transcriptomics and proteomics to be highly expressed in cellulose-bound cell fractions. Structural homology to other classes of proteins could not be assigned, indicating that this is truly a new class of biomolecules and establishing a new paradigm for how cellulolytic bacteria adhere to cellulose.
Conclusions: Both environmental communities and isolates have highlighted the importance of specific catalytic domains and binding proteins for cellulose breakdown. These results further define the known biodiversity of the genus Caldicellulosiruptor and indicate that additional efforts to isolate new species could lead to more prolific lignocellulose-degrading bacteria.
1. Blumer-Schuette, SE, et al. (2012). Caldicellulosiruptor core and pan genomes reveal determinants for non- cellulosomal thermophilic deconstruction of plant biomass. J. Bacteriol. 194(15), 4015-4028.
2. Lee, LL, et al. (2017). “Genus-wide assessment of lignocellulose utilization in the extremely thermophilicCaldicellulosiruptor by genomic, pan-genomic and metagenomic analysis.”Appl. Environ. Microbiol. In revision.
3. Blumer-Schuette, SE, et al. (2015). Discrete and Structurally Unique Proteins (Tāpirins) Mediate Attachment ofExtremely Thermophilic Caldicellulosiruptor Species to Cellulose. J. Biol. Chem. 290: 10645.
9:50 AM David Chang
Background: Mammalian cells are commonly cultured in commercial 10,000 L bioreactors to produce therapeutic proteins for treatment of diseases such as arthritis, multiple sclerosis, and diabetes. As the biotechnology industry continues to push culture densities higher to maximize product yield, higher aeration levels are required. Additional aeration leads to harsher environments for cells, leading to the need for improved shear protection strategies to minimize cell damage. Nonionic surfactants are routinely used in mammalian cell culture to protect cells from the hydrodynamic conditions of sparged bioreactors. We investigate surfactant-cell interactions by characterizing interfacial tension and cell membrane fluidity at various surfactant concentrations. We also demonstrate the application of a novel concentric cylinder mixer (CCM) assay to quantify the relative shear sensitivity of a CHO cell line in a production bioreactor.
Results: Despite the widespread use of surfactants for shear protection in cell culture, the mechanism of protection is poorly understood. We show that membrane rigidity correlates with increasing surfactant concentration, eventually reaching a plateau at high concentrations. Membrane fluidity also correlates with shear sensitivity as measured by the CCM assay. This assay is based on release of lactase dehydrogenase (LDH), an enzyme marker for cellular damage. Compared with other methods
to characterize shear sensitivity, the CCM assay requires low sample volume and minimal processing time. Additionally, a time course study of cells in a production bioreactor indicates that cell shear sensitivity dramatically increases upon reaching peak viable cell density. This increased sensitivity may be a result of depletion of surfactant, accumulation of waste in the medium, or physiological changes in the cell. With a simple shift in shear protectant concentration, we demonstrate increased harvest viability resulting in decreased cellular debris, decreased foam stability, and a two-fold
reduction in LDH upon harvest.
Conclusions: Our results expand the fundamental understanding of surfactant-cell interactions to guide further optimization of shear protection in mammalian cell culture. The application of our shear assay can aid in optimizing process parameter set points, enhancing medium formulations for process robustness, and also for the selection of shear resistant cell lines for process development.
10:10 AM Benjamin Zeldes
Background: The archaeal order Sulfolobales exhibits a remarkable diversity of lithotrophic (lit: rock-eating) metabolisms, with various species able to extract energy from sources such as metal ores, sulfur, and hydrogen gas [1]. All Sulfolobales grow in hot acidic environments (~70°C, pH < 3), which may help to solubilize their lithotrophic energy sources. They also exhibit significant genetic similarities, with all sequenced species sharing genes of the 3-hydroxypropionate/4- hydroxybutyrate (3HP/4HB) carbon fixation cycle [2]. These metabolisms show great promise as a basis for bioprocessing from inexpensive inorganic feedstocks as an alternative to the current (costly) starches and sugars. Recombinant expression of 3HP/4HB cycle enzymes in a thermophilic host has already allowed for production of chemicals partially from CO2 [3]. Now, a genetic system in Sulfolobus acidocaldarius, a member of the Sulfolobales, has opened up the possibility of taking advantage of these unique metabolisms within their native context [4]Results: Expression of part of the 3HP/4HB cycle in the thermophilic host Pyrococcus furiosus resulted in high-temperature production of 3-hydroxypropoinic acid, but differences in the host’s maturation enzymes limited titers. This can be overcome by recombinant expression of the appropriate Sulfolobales maturation enzyme [3], but host differences remain potentially limiting. In contrast, recombinant expression of sulfur-oxidation genes from other Sulfolobales in S. acidocaldarius, which does not natively grow on sulfur, led to a clear sulfur-oxidizing phenotype. This indicates that, even though the enzymes involved are complex (a heterodimer that is membrane-associated and a 24-subunit cytoplasmic protein) they can be functionally expressed within their native Sulfolobales context.
Conclusions: The use of a genetic host from within the Sulfolobales greatly simplifies the task of co-opting their lithotrophic metabolisms for biotechnological use. Extracting energy from sulfur oxidation to power carbon fixation would allow for carbon-based chemicals to be produced alongside a biologically-generated sulfuric acid stream. Meanwhile, new sequencing data has allowed for comparative genomics analysis among Sulfolobales species with various lithotrophic metabolisms, identifying new gene candidates for future expression in Saci to further
expand its repertoire of inorganic energy sources.
1. S.-V. Albers and B. Siebers, “The Family Sulfolobaceae,” in The Prokaryotes, E. Rosenberg, E. F. DeLong, S. Lory, E. Stackebrandt, and F. Thompson, Eds. Springer Berlin Heidelberg, 2014, pp. 323–346.
2. Leyn, S.A., Rodionova, I.A., Li, X., and Rodionov, D.A. (2015). Novel Transcriptional Regulons for Autotrophic Cycle Genes in Crenarchaeota. J. Bacteriol. 197, 2383–2391.
3. Lian, H., Zeldes, B. M., Lipscomb, G. L., Hawkins, A. B., Han, Y., Loder, A. J., … Kelly, R. M. (2016). Ancillary contributions of heterologous biotin protein ligase and carbonic anhydrase for CO2 incorporation into 3- hydroxypropionate by metabolically engineered Pyrococcus furiosus. Biotechnology and Bioengineering, 113(12):2652-2660
4. Wagner, M., van Wolferen, M., Wagner, A., Lassak, K., Meyer, B. H., Reimann, J., & Albers, S.-V. (2012). Versatile genetic tool box for the crenarchaeote Sulfolobus acidocaldarius. Evolutionary and Genomic Microbiology, 3, 214.

Coffee Break 10:30 – 10:50 AM

Oral Presentations 10:50 – 12:30 PM


 10:50 AM Amit Mishra
Background: There is a demand for more energy efficient and environmentally friendly processes for oxidative conversion of carbonaceous fuels, which includes valorization and energy production. A chemical looping scheme is a potential route, which utilizes a metal oxide in a two-step redox process. The first step involves the reduction of the metal oxide through a carbonaceous fuel whereas the second step is the re-oxidation of the metal oxide. This is applied to combustion, where it effectively separates oxygen from air without the parasitic energy requirement of cryogenic separation, in a process known as chemical looping with oxygen uncoupling (CLOU). The reduction combusts the fuel to CO2 with the re-oxidation step producing energy. Secondly, this is used to reform methane to syngas (CO + H2) via chemical looping reforming (CLR). The design of the metal oxide is critical in selective conversion of the carbonaceous fuel during a chemical looping process. The first approach is tuning the metal oxide to have an appropriate thermodynamic supply of oxygen (i.e. equilibrium PO2). The second approach is using the metal oxide as a catalyst, through surface modification. In this study, Mn-containing perovskites are identified as promising candidates for these applications due to their tunable redox properties. CaMnO3, Ca0.75Sr0.25MnO3, CaMn0.75Fe0.25O3, and BaMnO3 are screened for potential oxygen sources through DFT calculations of oxygen vacancy creation to identify a perovskite promising for CLOU. Next, the CLOU ineffective material is tested for CLR, with typical reforming metals (Ni and Fe) doped to enhance selectivity.
Results: DFT calculations showed the energy of vacancy creation decreased as follows: BaMnO3 > CaMnO3 > Ca0.75Sr0.25MnO3 > CaMn0.75Fe0.25O3. Thermogravimetric analysis confirmed i) BaMnO3 to have the lowest supply of oxygen and ii) doping CaMnO3 increased the supply of oxygen. With the potential for combustion identified, CaMnO3, Ca0.75Sr0.25MnO3, and CaMn0.75Fe0.25O3 were tested in a fluidized bed reactor for coal char combustion confirming doping CaMnO3 results in increased conversions above 90% with CO2 yield exceeding 75%. With BaMnO3 showing inadequate oxygen supply for complete combustion, it was tested for CLR, along with Fe and Ni doping. Results showed BaMnO3 has a high selectivity to syngas (90%), with Fe and Ni dopants increasing selectivity.BaMn0.5Fe0.5O3 showed exceptional selectivity, exceeding 95%. H2 TPR showed the BaMnO3 class of materials possess more strongly bound oxygen leading to the higher selectivity.
Conclusions: Investigation of Mn-containing perovskites showed CaMnO3 and BaMnO3-based perovskites are suited for CLOU and CLR respectively. Sr and Fe doping of CaMnO3 increased the thermodynamic supply of oxygen leading to higher coal char conversion and CO2 yield. Similarly, the low supply of oxygen from BaMnO3 makes it selective for methane partial oxidation. The selectivity was enhanced by Ni and Fe dopants.
11:10 AM Ishan Joshipura
Background: This work utilizes alloys of gallium as soft and fluidic electronic conductors. Integrating liquid metals with soft polymers or gels enables electronic devices that can interface with living tissue, which is inherently soft and deformable. [1] In contrast, conventional electronic devices are made of rigid materials and exhibit pre-designed properties. Meanwhile, soft electronics can be deformed without major loss of function. Moreover, deforming these electronic devices can alter or reconfigure their electronic properties (i.e., resistance or resonant frequency). However, the surface oxide (~3 nm in air) of gallium and its alloys limits the use of these liquid metals for reconfigurable electronic systems. Specifically, this oxide ‘skin’ exhibits a yield-stress and adheres to virtually any surface. [1] As a result, reversibly flowing the metal through small voids, such as microfluidic devices, is difficult to achieve.
Results: This work aims enable reversible flow of liquid metals by preventing the adhesion of the oxide. One approach is to pre-inject water into capillaries prior to injecting a plug of liquid metal. The water forms a thin slip-layer between the interface of the capillary wall and surface of the metal. Thereafter, applying an AC voltage creates a surface tension gradient that allows the metal plug to move in an oscillatory fashion. [2] Alternatively, this work explores the use of surface coatings to prevent the adhesion of the oxide. [3] We utilize dynamic contact angle measurements to de-couple the influence of surface chemistry and surface roughness on the adhesion. Insights from both methods have been applied to demonstrate electronic components (filters and antennas for data communication) that tune their behavior in response to a mechanical or electrical stimuli. [4]
Conclusions: The oxide ‘skin’ of gallium alloys adheres to most surfaces, despite exhibiting a high advancing contact angle. Surface treatments, such as slip-layers of water and hierarchical coatings, may prevent the adhesion of the oxide. Thereafter, liquid metal may flow through capillaries and microfluidic networks reversibly using either low voltage, mechanical force, or pneumatics; doing so enables electronic devices (i.e., antennas) that exhibit tunable electromagnetic behaviors. On the contrary, selectively controlling the adhesion of the metal oxide enables patterning of liquid metals at room temperature, without the need for vacuum
systems, and in a rapid manner (~minutes). These patterned metals can be combined with soft polymers or gels to form electronic devices; such electronic devices can directly contact with living tissues or integrate into textiles to serve as wearable electronic platforms. [5]
1. Dickey, M. D. (2017) Stretchable and Soft Electronics using Liquid Metals. Adv. Mater.
2. Khan, M. R., Trlica, C., So, J.-H., Valeri, M. & Dickey, M. D. (2014) Influence of Water on the Interfacial Behavior of Gallium Liquid Metal Alloys. ACS Appl. Mater. Interfaces 6: 22467–22473
3. Joshipura, I.D., Ayers, H.R., Castillo G, Adams, J, Dickey, MD (2017) Patterning and Reversible Actuation of Liquid Gallium Alloys by Preventing Adhesion on Rough Surfaces, ACS Appl. Mater. Interfaces submitted
4. Reichel, K. S. et al. (2017). Liquid metals for active terahertz waveguides. 42nd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 1-2
5. Joshipura, I. D., (2015). Ayers, H. R., Majidi, C. & Dickey, M. D. Methods to pattern liquid metals. J. Mater. Chem. C 3: 3834–3841
11:30 AM Sangchul Roh
Background: Three-dimensional (3D) printing of polymers is accomplished easily with thermoplastics as the extruded hot melt solidifies rapidly during the printing process. 3D printing with crosslinkable polymer precursors, however, is more challenging due to their longer curing times. One crosslinkable polymer of specific interest is polydimethylsiloxane (PDMS).
Results: We present an efficient new colloidal approach for 3D-printing with PDMS by using a capillary suspension ink containing PDMS in the form of both pre-cured microbeads and uncured liquid precursor, dispersed in water as the continuous medium. Owing to strong capillary forces resulting from the PDMS liquid precursor, the suspensions behaved like thixotropic pastes, which are extrudable at high shear stress and possess the high storage moduli at low shear stress that are required for 3D-printing via direct ink writing. The resulting three-phase capillary ink could be 3D printed and cured both in air and under water. The liquid PDMS bridges were thermally crosslinked after printing, resulting in structures that were remarkably elastic and flexible. Their porosity and mechanical properties, such as tensile modulus, could be controlled by the fraction of liquid precursor in the original multiphasic dispersion. Self-standing elastic structures could also be made by directly printing and curing the ink under aqueous solutions.
Conclusions: As this ink is made of porous biocompatible silicone, it can be used in 3D printed biomedical products, or in applications such as direct printing of bio-scaffolds on live tissue. The high softness, elasticity, and resilience of these 3D printed structures may also open new opportunities in soft robotics and stimuli-responsive materials.
References: Roh, Sangchul, Dishit P. Parekh, Bhuvnesh Bharti, Simeon D. Stoyanov, and Orlin D. Velev (2017). 3D printing by multiphase silicone/water capillary inks. Advanced Materials, 29: 1701554
11:50 AM Dishit P. Parekh
Background:Soft electronics are devices that can be bent, folded, stretched, or conformed regardless of their material composition without losing their electronic functionality. These electronics are employed in healthcare for biomonitoring requiring them to be inexpensive and customizable according to an individuals’ body needs making 3D printing an ideal rapid prototyping technique for fabricating such electronic devices. Current methods for additive manufacturing of electronics using metals [1] tend to be prohibitively expensive, and use energy- intensive lasers at high sintering temperatures in excess of 800°C. Secondly, they need vacuum- like pressures to avoid oxidation while handling metal nanoparticles, leading to porosity in finished parts, low resolution and poor electrical conductivity, apart from having slow printing speeds. Finally, the operating procedures are impossible to integrate with various polymeric,
organic, soft and biological materials. Here, we present a simple approach that utilizes low melting point gallium-based alloys that offer the electrical and thermal benefits of various metals like gallium and indium, combined with the ease of printing due to its low viscosity.
Results: We have utilized these metals to build mechanically stable structures due to the formation of a thin oxide skin on the surface despite having high surface tension (~10x water). The oxide skin is passivating, forms spontaneously in presence of air or dissolved oxygen allowing us to direct-write planar and free-standing, out-of-plane conductive microstructures down to a resolution of ~10 μm [2], using an on-demand shear-driven flow occurring at relatively low pressures (~10s of kPa). We have exhibited the patterning of 3D multilayered microchannels with vasculature using liquid metals as a sacrificial template at room temperature that can be embedded in lab-on-a-chip devices to enable inexpensive fabrication of personalized healthcare sensors [3]. We have also demonstrated rapid prototyping of functional electronics such as flexible and stretchable radio-frequency antennas for defense communications and wearable thermoelectric generators (TEG) for energy-harvesting applications [4].
Conclusions:In summary, we show that a shear-driven flow dispensing approach for printing liquid metals can fabricate 2D & 3D microarchitectures. These mechanisms validate that skin forming liquids can be molded into several shapes earlier prohibited by the weakening effects of gravity and surface tension, in order to print soft conductive devices at room temperature.
1. Parekh, D. P., Cormier, D. & Dickey, M. Multifunctional Printing: Incorporating Electronics into 3D Parts Made by Additive Manufacturing. in Additive Manufacturing 215–258 (CRC Press, 2015).
2. Trlica, C., Parekh, D. P., Panich, L., Ladd, C. & Dickey, M. D. 3-D Printing of Liquid Metals for Stretchable and Flexible Conductors. in Proceedings of SPIE 9083, 90831D–90831D–10 (2014).
3. Parekh, D. P., Ladd, C., Panich, L., Moussa, K. & Dickey, M. D. 3D printing of liquid metals as fugitive inks for fabrication of 3D microfluidic channels. Lab. Chip 16, 1812–1820 (2016).
4. Suarez, F., Parekh D., Ladd, C., Vashaee, D., Dickey, M. D. & Öztürk, M. C., Flexible thermoelectric generator using bulk legs and liquid metal interconnects for wearable electronics. Appl. Energy 202, 736–745 (2017).
12:10 PM Koohee Han
Background: I will demonstrate how magnetically responsive patchy microcubes can be assembled into self-reconfiguring microclusters and employed as microbots and microswimmers [2]. The key feature of these assemblies is their storage of magnetic energy in the asymmetrically coated metallic patches in the form of residual magnetic dipoles. As a result, on-demand dynamic reconfiguration of the assemblies can be achieved by switching between directional field-dipole and dipole-dipole interactions via turning the magnetic field on and off, where the pattern of reconfiguration is encoded in the sequence of the orientation of the cubes. I provide examples of assemblies of specific sequences that can be actuated to perform microscale operations such as capturing and transporting live cells, acting as prototypes of microbots. I also demonstrate that these reconfigurable clusters can function as a new class of self-propelling microswimmers in non-Newtonian fluids when actuated by time-asymmetric magnetic fields.
Results: I will demonstrate how magnetically responsive patchy microcubes can be assembled into self-reconfiguring microclusters and employed as microbots and microswimmers [2]. The key feature of these assemblies is their storage of magnetic energy in the asymmetrically coated metallic patches in the form of residual magnetic dipoles. As a result, on-demand dynamic reconfiguration of the assemblies can be achieved by switching between directional field-dipole and dipole-dipole interactions via turning the magnetic field on and off, where the pattern of reconfiguration is encoded in the sequence of the orientation of the cubes. I provide examples of assemblies of specific sequences that can be actuated to perform microscale operations such as
capturing and transporting live cells, acting as prototypes of microbots. I also demonstrate that these reconfigurable clusters can function as a new class of self-propelling microswimmers in non-Newtonian fluids when actuated by time-asymmetric magnetic fields.
Conclusions: Field-directed active colloidal clusters with sequence-determined folding pattern and function may find applications in soft robotics, microsurgery, biological separations and bioinspired colloidal origami. The principles of this simple platform actuator can be extended to future advanced, hierarchical, structures by using more complex particle shapes, compositions, and field parameters to address a broad range of exciting applications, from robotics and micromanipulation to the next generation of responsive and self-healing materials.
1. Bharti, Bhuvnesh and Orlin D. Velev (2015). Assembly of Reconfigurable Colloidal Structures by Multidirectional Field-Induced Interactions. Langmuir, 31: 7897-7809.
2. Han, Koohee, C. Wyatt Shields IV, Nidhi D. Diwakar, Bhuvnesh Bharti, Gabriel P. López, and Orlin D. Velev (2017). Sequence-Encoded Colloidal Origami and Microbot Assemblies from Patchy Magnetic Cubes. Science Advances, 3: e1701108.


Lunch 12:30 – 2:20 PM

1:00 PM Announcement of Vivian T. Stannett Fellow Award
1:15 PM Announcement of Fall 2018 Praxair Exceptional Teaching Assistant Award
1:30 PM Keynote Address: Professor Arthi Jayaraman

Oral Presentations 2:20 – 4:20 PM

Materials and Computation

 2:20 PM Yiliang Lin
Background: Metals that are liquid at room temperature are attractive due to their unique combination of metallic and fluidic properties. Due to their negligible vapor pressure and low toxicity, gallium and its alloys are promising alternative to mercury. Various soft electronic devices, including, stretchable wires, flexible antenna and self-healing circuit, have demonstrated the unique features of gallium-based liquid metals. While metal nanoparticles have been well-known for sensors, therapeutics and electronics inks, here we demonstrate that the liquid metal nanoparticles are suitable for soft electronics and biomedical applications with unique responsivene characteristics.
Results: We report on a facile method to synthesize liquid metal nanoparticles in ethanol via sonochemistry. Casting the liquid metal nanoparticles between two elastomer pads results in non-conductive films. However, mechanical pressure sinters locally the liquid metal nanoparticles into conductive paths by simply using a writing stylus. This “mechanical sintering” method is attractive relative to conventional sintering techniques (i.e., light or heat) because it operates at ambient conditinos. Using this strategy, we fabricated soft circuit boards and flexible antennas with on demand frequency-shifting properties. We also demonstrate that it is possible to carry out surface modification on the liquid metal nanoparticles to turn them into drug delivery agents for transformable nanomedicine. The drug is loaded on the nanoparticles using thiol chemistry/guest-host reaction; systematic cell/animal studies have been carried out to demonstrate the ability for anticancer therapy, further proving the low-toxicity of EGaIn. We have also explored a way to synthesize stable liquid metal nanoparticles in aqueous solution and further transformed the liquid metal nanoparticles into nanorods through mild heating. The type of surfactant used plays an important role in the process. We further apply the shape transformation mechanism to create a novel nanomedicine system, in which – once triggered by remoted infrared radiation (IR) light – the shape-changing nanomedicine will not only effectively release the drugs in tumor region but also break the endosomal membrane to kill tumor cells. A systematic cell and animal study is performed to show the effective cancer treatment.
Conclusions: The soft nature of liquid metals endows their nanomaterials with unique mechanical properties, such as deformability, which make them compatible as nano-scale inks for soft, stretchable electronics and as promising materials for biomedicine, and as conductive components in microsystems.
 2:40 PM Stephen Barilovits
Abstract: The Biax Spunblown® process is a unique, multi-row variant of the meltblowing process. Molten polymer, often polypropylene, is extruded from an array of outlets, each of which is individually surrounded by a concentric high velocity air stream. To provide the first thorough understanding of this unique process, we have experimentally investigated the effects of critical processing parameters on the fiber and web formation process. Air temperature, air speed, and polymer throughput have been related to fiber diameter distribution and distance to solidification. Mean fiber diameters ranged from less than 1 μm to almost 14 μm. Air temperature effects were investigated using high-resolution infrared thermography and indicated that substantial heat transfer occurs between the air and molten polymer prior to spinning. A detailed three-dimensional air temperature and velocity profile is presented for an array of supplied temperatures and air cavity pressures. Ultra-high-speed videography indicated that, for some conditions, fiber-forming throughput oscillates with time for each spinneret. The fact that a single spinneret can produce both large and small fibers contradicts the prevailing intuition that the fiber diameter distribution can be explained entirely by the two dimensional thermal profile characteristic of an array of spinnerets. A similar phenomenon has been observed in melt spinning processes, where it has been termed “draw resonance”. We hypothesize that we are observing draw resonance in a meltblowing system and are experimentally and theoretically investigating the matter.
 3:00 PM Steven J. Zboray
Background: Environmental contamination by heavy metals is a serious issue in many industrial processes, but current remediation technologies are mainly based on low affinity adsorption onto expensive substrates like activated carbon [1]. Maleic anhydride can be easily polymerized with a many common electron donating comonomers [2]; these polymers can be chemically modified through facile reactions with a variety of moieties, particularly amines [3]. This combination of properties makes maleic anhydride-based copolymers well suited to impart desired chemical or physical surface properties to substrates. Of importance is the well-known affinity sulfur-containing moieties toward metals, which has been extensively investigated as a means of chelating toxic species [4].
Results: Maleic anhydride copolymers were deposited on a nonwoven substrate crosslinked. These coatings were further modified to present metal capturing groups over a large surface area with low materials cost. Static and flow tests demonstrated the ability of this system to remove multiple toxic heavy metals from water. It was found that this binding is irreversible and proceeds even in high ionic strength solutions. Differential capture capacities for different metals undergoing competitive adsorption are also presented.
Conclusions: Maleic anhydride can be copolymerized with hydrophobic monomers to easily bind to low-cost nonwovens made from commodity polymers, then chemically modified post-polymerization to purify water from heavy metal contamination. This chemistry can be generalized into a toolkit for modifying both hydrophilic and hydrophobic surfaces with arbitrary chemistries for high value-added applications.
1. Hashim, M. A., Mukhopadhyay, S., Sahu, J. N., & Sengupta, B. (2011). Remediation technologies for heavy metal contaminated groundwater. Journal of environmental management, 92(10), 2355-2388.
2. Trivedi, B. (2013). Maleic anhydride. Springer Science & Business Media.
3. Schmidt, U., Zschoche, S., & Werner, C. (2003). Modification of poly (octadecene‐alt‐maleic anhydride) films by reaction with functional amines. Journal of applied polymer science, 87(8), 1255-1266.
4. Matlock, M. M., Henke, K. R., & Atwood, D. A. (2002). Effectiveness of commercial reagents for heavy metal removal from water with new insights for future chelate designs. Journal of hazardous materials, 92(2), 129-142.


Coffee Break 3:20 – 3:40 PM


 3:40 PM Yiming Wang
Background: Amyloid β (Aβ) is an intrinsically disordered and amyloidogenic protein associated with Alzheimer’s disease. Fundamental understanding of the aggregation and inhibition of Aβ and other amyloidogenic peptides [1] could pave the way for unravelling the pathology of various neurodegenerative diseases. In the present study, we focus on two key amyloidogenic fragments of full length Aβ protein, Aβ(16-22) and Aβ(17-36).
Results: Firstly, we applied discontinuous molecular dynamics (DMD) combined with the PRIME20 force field to construct a thermodynamic phase diagram [2] of Aβ(16-22) peptides in the temperature-concentration plane by measuring the equilibrium soluble peptide concentration at which the aggregate phase neither grows nor shrinks. We also showed that the kinetically-observed aggregates are structurally different from those predicted from the equilibrium phase diagram. The predicted solubility for macroscopic Aβ(16-22) fibril agrees with preliminary experiments. Comparison of the kinetic and thermodynamic “phase diagrams” explains why Aβ(16-22) aggregates go through a “one-step” nucleation at high temperature and a “two-step” nucleation at low temperature. Secondly, we perform DMD/PRIME20 simulations combined with a newly built inhibitor model to examine the effect of vanillin, resveratrol, curcumin, and epigallocatechin-3-gallate (EGCG) on the aggregation of Aβ(17-36) peptides. [3] We showed that the single-ring compound, vanillin, slightly slows down but cannot inhibit the formation of a U-shaped Aβ(17-36) protofilament. The multiple-ring compounds, EGCG, resveratrol, and curcumin, redirect Aβ(17-36) from a fibrillar aggregate to an unstructured oligomer. The rank order of inhibitory effectiveness of Aβ(17-36) aggregation is as follows: EGCG > resveratrol > curcumin > vanillin, consistent with experimental findings [4] on inhibiting full-length Aβ fibrillation.
Conclusions: (1) We applied a combination of coarse-grained molecular dynamic simulation and classical nucleation theory to study the thermodynamics and kinetics of Aβ(16-22) peptide aggregation. (2) We developed a coarse-grained inhibitor model compatible with the PRIME20 protein model that allows investigation of the inhibition mechanism of four naturally occurring polyphenols on Aβ(17-36) aggregation.
1. Wang, Y., Shao, Q., Hall, C. K., (2016) N-terminal Prion Protein Peptides PrP(120-144) Form Parallel Inregister β-sheets via Multiple Nucleation-dependent Pathway. J. Biol. Chem. 291(42), 22093-22105
2. Wang, Y., Auer, S., Hall, C. K., (2018) Thermodynamic Phase Diagram of Amyloid β(16-22) Peptide. (in preparation)
3. Wang, Y., Latshaw, D. C., Hall, C. K., (2017) Aggregation of Amyloid Beta (17-36) in the Presence of Naturally Occurring Phenolic Inhibitors Using Coarse-Grained Simulations. J. Mol. Biol. DOI: 10.1016/j.jmb.2017.10.006
4. Rajasekhar, K., Chakrabarti, M., Govindaraju, T., (2015) Function and toxicity of amyloid beta and recent therapeutic interventions targeting amyloid beta in Alzheimer’s disease. Chem. Comm. 51(70), 13434-13450.
 4:00 PM Chengxiang Liu
Background: Crystallization from solution is fundamental to drug production in the pharmaceutical industry where 90% of products contain one or more crystalline materials. However, measurements of crystallization kinetics are time consuming due to the stochastic nature of nucleation. While such molecular motions are possible to be observed via computational simulations, it remains a challenge for standard atomistic simulations with nucleation being a rare event. In this work, we first implemented the String Method in Collective Variables (SMCV) in combination with the construction of order parameters (OPs) [1] to sketch minimum free energy pathways (MFEP) [2] for the nucleation of small drug molecules in different solvents (water, methanol and acetonitrile). Then we performed detailed crystallization induction time measurements to obtain the nucleation kinetics and compared the results with simulations. Two molecules, sulfadiazine (SFD) and sulfamerazine (SFM), were chosen for our study due to their structural similarity but different nucleation behaviors.
Results: Force field parameters of SFD and SFM molecules were developed to accurately reproduce the crystal structures of both compounds in the simulations. Compared with using CHARMM general force field, the structural error of unit cell parameters for SFD decrease from 3-8% to 0.3-1.5%, and the error for SFM decreased from 7-12% to 0.1-1.8%. The constructed order parameters from a generalized pair distribution function were able to quantitatively distinguish liquid structure and solid structure of SFD and SFM, as well as different polymorphs of SFM. Nucleation energy barriers were obtained from the sketched minimum free energy pathways, and a lower nucleation barrier in one solvent was a prediction for a faster nucleation rate in the experiment. For SFD, the experimental results agreed with the calculations with the nucleation rates having the following order in different solvents: acetonitrile > water > methanol. The results of SFM were confounded by its polymorphism, but the results from the simulation and the experiment were still consistent once the correct nucleated form was determined.
Conclusions: Both simulations and experiments were implemented to study the nucleation kinetics of SFD and SFM in different solvents. The results from both approaches were consistent, and the methods implemented in our simulations could make correct predictions for nucleation rates of small drug molecules in different solvent systems.
1. E. E. Santiso and B. L. Trout (2011). A general set of order parameters for molecular crystals. J. Chem. Phys., 134: 064109.
2. Maragliano et al (2006). String method in collective variables: Minimum free energy paths and isocommittor surfaces. J. Chem. Phys., 125: 024106.

Poster Session 4:30 – 6:00 PM


Hadel Al Asafen

AbstractMorphogen-mediated patterning of developing tissues is a highly dynamic process.
However, there are only a handful of quantitative measurements of biophysical parameters associated with morphogen gradients. Here we report measurements of the mobility of Dorsal, a Drosophila homolog of NF-κB, in the early embryo using scanning fluorescence correlation spectroscopy techniques. We find that the diffusivity of Dorsal varies along the dorsal-ventral axis, with lowest diffusivities on the ventral side. Further analysis shows that it is only Dorsal in the nucleus that has a spatially-dependent diffusivity; the cytoplasmic pool of Dorsal has a constant diffusivity in the embryo. Furthermore, nuclear export rates appear to also be lower on the ventral side of the embryo. Analysis of mutants in which Dorsal nuclear levels are uniform has confirmed this DV asymmetry in diffusivity and nuclear export rates. These observations could be explained by a significant pool of DNA-bound Dorsal on the ventral side of the embryo. We propose that either Toll-mediated phosphorylation of Dorsal or Cactus binding to Dorsal explains the DV asymmetry in these two biophysical processes.

Kaitlyn Bacon

Background: The separation of biologics, like cells and organelles, is similar to traditional protein purification as both techniques aim to recover their target at a high purity and yield. However, there is an added complexity in the separation of biologics; the functionality and viability of the biologic must be maintained throughout the separation process. The avidity effect complicates the elution of biologics as multiple interactions occur between receptors on the biologic surface and ligands on the capture surface, thereby creating a strong binding force. This phenomenon is also compounded as antibodies, that inherently have high affinities for their target, are the most commonly used ligands for biologics separation. To break this strong interaction for elution, harsh solvents are typically used that are incompatible with the viability of the biologic. Synthetic peptides and protein scaffolds have been proposed as alternative ligands to maintain targeted affinity, while lowering binding strength to facilitate elution. Advances in library screening methods have afforded the identification of ligands for extracellular receptor targets. However, these screens are limited as the selections are typically completed against a soluble form of the receptor immobilized onto magnetic beads. The ligand binding epitope on the soluble protein may not be accessible when the receptor is displayed on the actual biologic surface. To overcome this limitation, we propose to screen ligand libraries against target proteins that are expressed on the surface of yeast.
Results: Through dual display of the target protein and SsoFe2, an iron oxide binding protein, on the yeast surface, the target cells can become magnetized after iron oxide incubation, allowing for easy isolation of ligand binders. Magnetic yeast expressing the Fc portion of human IgG (HFC) were able to significantly enrich mixed populations for cells expressing a binder protein specific to HFC, suggesting target proteins on yeast cells can still find their binding partner when there is significant competition from other yeast surface proteins. To validate the use of magnetized yeast in library screens, selections were carried out against c-Kit and TOM22, proteins expressed on the surface of hematopoietic stem cells and mitochondria respectively, using cyclic peptide libraries generated using mRNA display, as well as a Sso7d protein scaffold library. We have developed a method to chemically cyclize linear peptides displayed on the surface of yeast using a disuccinimidyl glutarate crosslinker that is being used to test if the identified peptides are actual binders for their target without the need to chemically synthesize the peptides.
Conclusions: Even without further affinity maturation, it is likely the ligands identified from both screens will be sufficient in isolating their biologic targets as the avidity effect can be evoked for capture through the immobilization of the ligands onto magnetic capture beads. In the future, the peptide libraries will be cyclized with a stimuli-responsive linker to promote gentle elution through a reversible change in binding affinity due to ligand conformational changes.

David Chang 
Background: Mammalian cells are commonly cultured in commercial 10,000 L bioreactors to produce therapeutic proteins for treatment of diseases such as arthritis, multiple sclerosis, and diabetes. As the biotechnology industry continues to push culture densities higher to maximize product yield, higher aeration levels are required. Additional aeration leads to harsher environments for cells, leading to the need for improved shear protection strategies to minimize cell damage. Nonionic surfactants are routinely used in mammalian cell culture to protect cells from the hydrodynamic conditions of sparged bioreactors. We investigate surfactant-cell interactions by characterizing interfacial tension and cell membrane fluidity at various surfactant concentrations. We also demonstrate the application of a novel concentric cylinder mixer (CCM) assay to quantify the relative shear sensitivity of a CHO cell line in a production bioreactor.
Results: Despite the widespread use of surfactants for shear protection in cell culture, the mechanism of protection is poorly understood. We show that membrane rigidity correlates with increasing surfactant concentration, eventually reaching a plateau at high concentrations. Membrane fluidity also correlates with shear sensitivity as measured by the CCM assay. This assay is based on release of lactase dehydrogenase (LDH), an enzyme marker for cellular damage. Compared with other methods to characterize shear sensitivity, the CCM assay requires low sample volume and minimal processing time. Additionally, a time course study of cells in a production bioreactor indicates that cell shear sensitivity dramatically increases upon reaching peak viable cell density. This increased sensitivity may be a result of depletion of surfactant, accumulation of waste in the medium, or physiological changes in the cell. With a simple shift in shear protectant concentration, we demonstrate increased harvest viability resulting in decreased cellular debris, decreased foam stability, and a two-fold reduction in LDH upon harvest.
Conclusions: Our results expand the fundamental understanding of surfactant-cell interactions to guide further optimization of shear protection in mammalian cell culture. The application of our shear assay can aid in optimizing process parameter set points, enhancing medium formulations for process robustness, and also for the selection of shear resistant cell lines for process development.

Daphne Collias
Background: DNA cleavage by RNA-guided CRISPR nucleases has been shown to be lethal in bacteria [1, 2, 3] and has given rise to the development of CRISPR as an antimicrobial agent. This technology is programmable by modifying the guide to target specific strains of bacteria [1, 2, 3]. This comes at an opportune time as antibiotic resistance in bacteria continues to increase. Since implementing CRISPR-Cas systems towards antimicrobial applications, the next challenge was broadly delivering the systems in diverse bacterial communities. We developed an engineered, broad host range P1 bacteriophage as a CRISPR antimicrobial delivery vehicle towards various strains of gammaproteobacteria. We were interested in determining if P1 would be able to package its genome while also encoding for a CRISPR nuclease and guide. As a result, the delivery efficiency based on packaged DNA lengths was determined and we were able to confirm that P1 can package and deliver its genome and DNA encoding for a CRISPR nuclease. Furthermore, we identified locations on the P1 genome to incorporate DNA without impacting particle production and subsequent infection into hosts of interest. We compared the infectivity of P1 encoding for a CRISPR system across several gammaproteobacteria.
Results: We identified regions on the P1 genome that can be used as sites to incorporate foreign DNA without impacting the ability to produce phage and infect cells. We determined the packaging limit of P1 encoding yeast genomic DNA and quantified the resulting delivery efficiencies. We determined the ability of P1 encoding a CRISPR nuclease to infect and survive in Escherichia coli, Shigella flexneri, Klebsiella pneumoniae, and Raoultella planticola.
Conclusions: Based on this work, we can conclude that the coi, sim, is1, and phd/doc sites can be used as landing sites for the CRISPR antimicrobial. The P1 particle can encapsulate a CRISPR antimicrobial encoded on the genome as a result of the packaging limit study. P1 can be used as a CRISPR antimicrobial delivery vehicle to its host range.
References: 1. Bikard D, Euler CW, Jiang W, Nussenzweig PM, Goldberg GW, Duportet X, Fischetti VA, Marraffini LA: Exploiting CRISPR-Cas nucleases to produce sequence-specific antimicrobials. Nat. Biotechnol. 2014, 32:1146–1150.
2. Citorik RJ, Mimee M, Lu TK: Sequence-specific antimicrobials using efficiently delivered RNA-guided nucleases. Nat. Biotechnol. 2014, 32:1141–1145.
3. Gomaa AA, Klumpe HE, Luo ML, Selle K, Barrangou R, Beisel CL: Programmable removal of bacterial strains by use of genome-targeting CRISPR-Cas systems. MBio 2014, 5:e00928–13.

Scott Collins
Background: Applications of CRISPR-Cas systems have grown at a nearly unprecedented rate, with uses ranging from gene therapy to high-throughput genetic screening. This growth has fostered an intense demand for improved CRISPR-Cas tools. However, CRISPR-Cas toolkits are still largely dominated by some of the first characterized Cas nucleases. We show here that by leveraging cell-free transcription translation systems we can rapidly prototype engineered CRISPR-Cas technologies or characterize new CRISPR-Cas proteins.
Results: We were firstly able to show that CRISPR-Cas activity in cell-free transcription translation (TXTL) systems is tightly correlated to in-vivo activity. We then leveraged TXTL systems to design engineered single guide RNAs which could be inactivated by antisense RNAs. This Cas inactivation strategy was further improved through engineered guide RNA mimics, which efficiently sequestered Cas nucleases. In addition, a TXTL screen was able to rapidly assess the activity and targeting specificity of un-characterized anti-CRISPR proteins.
Conclusions: Cell-free transcription translation systems enabled rapid prototyping and characterization of new CRISPR-Cas technologies. This technology can support increasing demand for improved technologies as implementation of CRISPR-Cas systems grow in the lab, clinic, and natural environment.

Christopher Duran
Background: Our lab has developed a prototype falling film bioreactor (FFBR) for immobilized cell biocatalysis. A FFBR can be operated using very little water and with a low power input because the gas has only a thin layer of liquid to pass through to contact the cells. Because the cells are immobilized and unable to multiply, minimal waste biomass is generated and secreted products accumulate in the cell-free liquid phase. Our model organism is the methanotrophic bacterium Methylomicrobium alcaliphilum 20Z which is being engineered by collaborators at DOE NREL (Golden, CO) to convert CH4 into valuable organic acids. The goal of this project is to strongly adhere M. alcaliphilum 20Z to the hydrophilic paper substrate of the FFBR.
Results: Two small prototype FFBRs (~0.04 m2, ~0.004 m2) were built for efficient mass transfer and uniform falling liquid films over paper cylinders at low Reynolds numbers (Re 20-200). The mass transfer coefficient in the FFBR at low flow (Re=20) was determined to be > 7.0×10-5 m s-1 which compares favorably with predicted values.[1] A simple raceway channel assay was developed to study adhesion of cells to the paper substrate.[2] The target biocatalyst concentration for rapid CH4 uptake is 1014 CFU m-2. In a coating of 8×1012 CFU/m2 wild-type cells, about 90% of cells remain adhered under liquid flow of ~5 N/m2 shear stress. The apparent adhesion at low cell density is likely due to cells embedded in the paper pores. Non-toxic polymer binders were tested to more tightly adhere a higher density of cells after film formation by drying. Sugars added to the coating formulation protect the cells during drying and can increase porosity in the final polymer film.[3] Collaborators have engineered the cells to express carbohydrate binding domains (CBD) tethered to native S-layer or heterologous OmpA surface proteins to increase affinity to the paper. These CBDs are substrate-specific binding regions of cellulases, endoglucanases, and other enzymes from many donor organisms such as Clostridium thermocellum and Trichoderma reesei.
Conclusions: The prototype FFBR performs as a thin film mass transfer device as predicted and will enable CH4 conversion at low power/water input if M. alcaliphilum 20Z can be optimally immobilized. Polymer binders tightly adhere M. alcaliphilum 20Z, but analysis is needed to determine the effect of the added polymer barrier to mass transfer and desiccation resistance will need to be optimized. So far, strains engineered for enhanced cellulose affinity did not demonstrate increased adhesion but additional CBD surface expression and characterization is planned.
1. Yih, Siu-Ming and Kai-Yune Chen (1982). Gas Absorption into Wavy and Turbulent Falling Liquid Films in a Wetted-Wall Column. Chem. Engr. Comm., 17:123-136.
2. Flickinger, Michael C. et al. (2017). Biocoatings: Challenges to Expanding the Functionality of Waterborne Latex Coatings by Incorporation Concentrated Living Microorganisms. J. Coat. Technol. Res., 14:791-808
3. Lyngberg O. K. et al. (2001). Engineering the Microstructure and Permeability of Thin Multilayer Latex Biocatalytic Coatings Containing E. coli. Biotechnol. Prog. 17:1169-1179

Jessica B Lee
Background: Information in biological systems is stored and transmitted not just in genomic sequences, but in the dynamic expression of this genetic material. Crucial information affecting developmental, homeostatic, and disease processes can be contained in how quickly and to what extent genes turn on. Furthermore, the input-output properties of genes are well known to be more complex than simple first or second-order kinetic processes, especially in eukaryotic cells. This complexity can be attributed to the fact that the eukaryotic genome is bound to hundreds of different proteins and RNAs that together with the genome comprise chromatin. There is thus strong reason to believe that chromatin regulates and gives rise to the complexity of dynamic gene regulatory properties [1].
Results: Here, we propose to use time-lapse microscopy with an optogenetic tool that allows light-dependent recruitment of chromatin regulators (CR) to a synthetic reporter in Saccharomyces cerevisiae with high (~2 minute) temporal resolution. To gain greater mechanistic insights into the design principles of chromatin regulation and the types of information that may be stored in the dynamic properties of gene regulation, we will characterize the kinetic gene activation/repression parameters of over 100 CRs, including histone acetyltransferases, histone deacetylases, transcription regulators, and nucleosome remodelers.
Conclusions: Clustering these CRs by their dynamic transcriptional behaviors through gene ontology may provide useful mechanistic insights into basic eukaryotic gene regulation and into selecting CRs for engineering chromatin-based transcriptional regulation.
1. Struhl, K., Fundamentally different logic of gene regulation in eukaryotes and prokaryotes. Cell, 1999. 98(1): p. 1-4.

Daniel Midkiff
Background: While human aging is a process that affects everybody, the genetics and molecular mechanisms involved with natural aging largely remain a mystery [1]. The nematode Caenorhabditis elegans is commonly used as a model organism for fundamental biological processes [2]. The use of microfluidic technology to create “lab on a chip” devices has dramatically increased the feasible data size of studies performed on C. elegans [3]. We are designing a novel, multi-layer microfluidic platform to maintain individual worms throughout their lifespan, while allowing late-onset phenotypic data to be acquired for identifying mutants with an accelerated rate of aging.
Results: The platform consists of an array of chambers designed to each support a single worm throughout its lifetime [4]. The progeny from each chamber are filtered to a separate well in a plate located beneath the device [5]. To load the device, a population of age-synchronized mutant worms is injected to the device. To ensure that only one worm loads into each chamber, a 1 mm long loading channel with a narrowed stopper is used for the initial loading step. Following the loading step, food media is constantly perfused through the device so that the worms remain well nourished. The worms will then automatically be measured and analyzed for a phenotype of interest (e.g. locomotion).
Conclusions: By using this platform, we anticipate identifying genes related to the aging process through the screening of random mutagenesis. Our goal is to automatically acquire data on many aging characteristics for each individual worm in a chamber. By identifying mutants that deviate from the wild-type expression profile late in life, we aim to further construct a gene network related to aging. The insights gained from our studies can be used to understand both the natural aging process as well as the mechanisms of neurodegenerative diseases.
1. Chen, Chun-Hao, Yen-Chih Chen, Hao-Ching Jiang, Chung-Kuan Chen, and Chun-Liang Pan (2013). Neuronal Aging: Learning from C. elegans . J. Molec. Signal. , 8 : 14.
2. Corsi, Ann K., Bruce Wightman, and Martin Chalfie (2015). A Transparent window into biology: A primer on Caenorhabditis elegans . Wormbook , ed. The C. elegans Research Community, http://www.wormbook.org
3. Bakhtina, Natalia A. and Jan G. Korvink (2014). Microfluidic laboratories for C. elegans enhance fundamental studies in biology. RSC Adv. , 4: 4691.
4. Chung, Kwanghun, Mei Zhan, Jagan Srinivasan, Paul W. Sternberg, Emily gong, Frank C. Schroeder, and Hang Lu (2011). Microfluidic chamber arrays for whole-organism behavior-based chemical screening. Lab Chip , 11 : 3689.
5. Xian, Bo, Jie Shen, Weiyang Chen, Na Sun, Nan Qiao, Dongqing Jiang, Tao Yu, Yongfan Men, Zhijun Han, Yuhong Pang, Matt Kaeberlein, Yanyi Huang, and Jing-Dong J. Han (2013). WormFarm: a quantitative control and measurement device toward automated Caenorhabditis elegans aging analysis. Aging Cell , 12 : 398

Jamie Nosbisch
Background: In fibroblasts responding to gradients of platelet-derived growth factor (PDGF), an important chemoattractant in development and wound healing, signaling through the phospholipase C (PLC)/protein kinase C (PKC) pathway proved necessary for chemotaxis [1]. PKC is activated through its binding to the lipid second messenger diacylglycerol (DAG), which is formed from hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP2) by PLC. Strikingly, in fibroblasts exposed to a shallow PDGF gradient, the density of DAG in the plasma membrane is focally enriched at the up-gradient leading edge [1], suggesting an internal amplification mechanism that has yet to be explored.
Results: We have developed and analyzed multiple mechanistic, reaction-diffusion models of the PLC/PKC signaling pathway activated in a PDGF gradient. The models include the major proteins (PDGF receptor, PLC, and PKC) and lipids (PIP2 and DAG) in the canonical pathway, as well as other signaling molecules that we implicate in various positive feedback loops. Model simulations suggest that the synergy of at least two of the putative feedback loops is needed to drive order-of-magnitude enrichment in a shallow PDGF gradient [2].
Conclusions: Experiments will need to be performed, in concert with refinement of our modeling framework, to elucidate the source(s) of nonlinearity in the signaling pathway. Current work involves improving the robustness of the gradient-sensing circuit and exploring the effects of the cell’s geometry on the polarization of the signaling network. In the future, this model will be linked to models describing the organization of the actin cytoskeleton and directionality of cell migration for a more comprehensive understanding of how fibroblast chemotaxis proceeds during physiological processes such as wound healing.
1. Asokan SB, Johnson HE, Rahman A, King SJ, Rotty JD, Lebedeva IP, Haugh JM, Bear JE (2014). Mesenchymal chemotaxis requires selective inactivation of myosin II at the leading edge via a noncanonical PLCγ/PKCα pathway. Developmental Cell, 31(6): 747-60.
2. Mohan K, Nosbisch JL, Elston TC, Bear JE, Haugh JM (2017). A reaction diffusion model explains amplification of the PLC/PKC pathway in fibroblast chemotaxis. Biophysical Journal, 113: 185-194.

Sahand Saberi

Abstract: Conducting life-long experiments to monitor the phenotypes occurring within a specie’s life-span can be challenging. Having a fully sequenced genome, mapped neurons, transparent body, and rapid life-cycle (~ 2 weeks) are some advantages that have made C. elegans an important model organism to study aging [1]. Various microfluidic devices have been fabricated so far to study C. elegans. However, none have been applied to conduct high-resolution high-throughput microscopy throughout the nematode’s life-span. This novel device enables life-long experiments in high-throughput and high-resolution manner [2-3]. Tracking an age-synchronized population over time allows us to identify subtle changes in aging cellular and subcellular morphologies, which couldn’t be identified by tracking different populations at each time point. Our innovative device eliminates the need for drugs to age-synchronize and immobilize the population, which are known to significantly affect animals’ physiology and life-span.
To perform life-long high-resolution experiments, the device should possess designated sections for culturing nematodes and microscopy. The device is comprised of two main sections: a main chamber and an imaging section. A population of worms is maintained in the main chamber where fresh E. coli is continuously perfused to. The bacteria perfusion is used to feed the nematodes as well as to evacuate their eggs. Even though eggs have almost the same width as worms, special geometric features of the device (shallower and tapered channels) allows separation of worms from eggs. These geometries act like a barrier for a moving C. elegans and decrease its tendency to pass through the obstacle while the eggs get evacuated properly.
Nematodes will be transferred to the imaging section for high-resolution microscopy once a day. Periodic imaging is performed to study neurodegeneration, synaptic plasticity, and more generally aging in neuronal circuits. Various parameters were considered in designing the imaging section to trap single worms within each imaging channel using pressure-driven flow as well as unifying nematode’s orientation. By optimizing design parameters, a loading efficiency (channels with worm/all channel) of 95% was accomplished. After trapping, nematodes are immobilized as a result of a decrease in temperature. Temperature reduction is accomplished by controlling the flowrate in the imaging channels, to balance the heat removal rate from the dry ice heat sink. High-resolution fluorescence microscopy is performed to monitor cellular and sub-cellular morphology (such as neurons and synapses). High-resolution imaging of features as small as synaptic sites (which are about 1 micron wide), as well as sensory neurons has been performed in this device without introducing any chemical stimuli that may lead to irreversible side effects.
This device thus enables performing high-resolution tracking of the morphological changes occurring within the nervous system of these nematodes throughput their life. Moreover, we will track populations of strains that serve as models for neurodegenerative diseases (such as Alzheimer’s or Parkinson’s). Comparing these results with those obtained for natural aging strains, should shed light on the mechanisms responsible for these aging-associated diseases, and provide a new platform to identify interacting environmental or genetic perturbations.
1. Corsi, Ann K., Bruce Wightman, and Martin Chalfie. “A transparent window into biology: a primer on Caenorhabditis elegans.” Genetics 200.2 (2015): 387-407.
2. Lee, Hyewon, et al. “A multi-channel device for high-density target-selective stimulation and long-term monitoring of cells and subcellular features in C. elegans.” Lab on a Chip 14.23 (2014): 4513-4522.
3. Xian, Bo, et al. “WormFarm: a quantitative control and measurement device toward automated Caenorhabditis elegans aging analysis.” Aging cell 12.3 (2013): 398-409.

John Schneible
Background: Currently, multiple (combination) drug chemotherapy is the prescribed treatment for cancer in the clinic. It affords a much higher therapeutic outcome as compared to single-drug chemotherapy. To manipulate multi-drug pharmacokinetics in a favorable manner, nanotechnology has been employed for developing advanced combination-drug delivery strategies [1-3], and has unveiled many important phenomena, namely drug synergism and scheduled delivery, both of which are crucial towards success in anti-cancer therapy. Currently, we have developed two novel hydrogel platforms comprised of FDA-approved polymers, (i) modified-chitosan hydrogels and (ii) modified-graphene oxide (GO) imbedded poly(vinyl alcohol) hydrogels. Through chemical modification of chitosan/GO, we have been able to tune the electrostatic and hydrophobic interactions that govern drug loading and release, insofar that scheduled delivery of our combination chemotherapy choice is delivered in a synergistic dose.
Results: Single drug release studies using modified-chitosan gels demonstrated the ability to release doxorubicin (DOX) and gemcitabine (GEM) with markedly different kinetics, dependent on both modification type and quantity. Dual drug release studies on modified-chitosan gels demonstrated the capability of releasing a varied dose of DOX and GEM, again dependent on modification type and quantity. Both the kinetics and the release dose observed in modifiedchitosan gels modified with acetyl groups is conducive towards scheduled and synergistic [4]. For work on GO-hydrogels, GO was modified with TREN, a group displaying two primary amines, to variable degrees. Both loading and release of DOX from modified-GO was tuned, as a function of surface density of TREN groups. Sustained release of DOX from both free and embedded GO particles demonstrated over the week(s) timescale.
Conclusions: Thus far, we have developed two systems made from FDA-approved polymers that showed favorable release characteristics embracing the current drug delivery paradigm of scheduled synergistic delivery. Current work illustrates the use of chemical handles present in both systems to tune both delivery kinetics and dosing. Future work on these systems seeks to develop microfluidic models, like 2D and 3D tissue-on-a-chip devices, to circumvent in vivo animal work as they afford better reproducibility as compared to traditional mouse models [5].
1. Hu, Q., Sun, W., Wang, C. & Gu, Z. Recent advances of cocktail chemotherapy by combination drug delivery systems. Adv. Drug Deliv. Rev. 98, 19–34 (2016).
2. Park, K. Drug delivery of the future: Chasing the invisible gorilla. J. Control. Release 240, 2–8 (2016).
3. Bhattacharjee, S. Nanomedicine literature: the vicious cycle of reproducing the irreproducible. Int. J. Pharmacokinet. 2, 15–19 (2016).
4. Vogus, D. R. et al. A hyaluronic acid conjugate engineered to synergistically and sequentially deliver gemcitabine and doxorubicin to treat triple negative breast cancer. J. Control. Release (2017).
5. Prabhakarpandian, B. et al. Synthetic tumor networks for screening drug delivery systems. J. Control. Release 201, 49–55 (2015).

Dilara Sen
Background: Epigenetic mechanisms play essential roles in mammalian neurodevelopment. Genomic imprinting is a process causing the mono-allelic expression of a gene in a parental origin specific manner, and it is controlled by a hierarchy of epigenetic events. Although their total numbers are small, a large percentage of imprinted genes are expressed monoallelicly in the human brain and hold important roles in development and disease. As a key example, the imprinted gene UBE3A is an important nexus in neurodevelopment and complex brain disorders. Deletion of the maternal or paternal alleles of UBE3A differentially leads to Angelman Syndrome or Prader-Willi Syndrome, respectively. In addition, duplication of maternal UBE3A occurs in some forms of Autism Spectrum Disorder [1]. These three diseases share some common neurological comorbidities strongly suggesting UBE3A’s role in neural function; yet, it is still unclear when, where, and how UBE3A is regulating or disrupting normal neurodevelopment. Therefore, mapping the allelic specificity and subcellular localization of UBE3A expression in neurons and other cell types in the brain could provide key insights into the underlying mechanisms of UBE3A-related disorders and suggest key cell types and brain regions for further study. However, due to technical and ethical limitations, such maps have yet to be generated in humans. Here we aim to map maternal and paternal allele-specific UBE3A expression throughout early prenatal brain development by engineering human cerebral organoids with allele-specific fluorescent reporters. Human cerebral organoids are model systems that exhibit most cell types of the human brain as well as polarized tissue structures [2]. Through this human system, we aim to connect molecular epigenetic processes to tissue-level properties by spatiotemporally mapping UBE3A. This map will suggest specific brain regions, cell types, developmental time windows, and mechanistic hypotheses to pursue in understanding UBE3A’s role in the human brain and in neurodevelopmental disorders.
Results: Our preliminary spatiotemporal map shows that the subcellular distribution of UBE3A is relatively uniform in early embryoid bodies. Although cytoplasmic labeling surpasses nuclear labeling right before neural induction, levels become uniform again by day 9. UBE3A appears to occupy same neuronal compartments during organoid development until neural maturation where levels in the cytoplasm appear to decline and the labeling becomes strictly nuclear
Conclusions: We have found that UBE3A in human cerebral organoids has a temporally and cell-type dependent subcellular distribution which could be a reflection of its predicted roles in proteosome targeting and transcriptional regulation.References:
1. A. Hogart, D. Wu, J.M. LaSalle, N.C. Schanen, The comorbidity of autism with the genomic disorders of chromosome 15q11.2-q13, Neurobiol. Dis. 38 (2010) 181–191. doi:10.1016/j.nbd.2008.08.011.
2. 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). doi:10.1038/nature12517.

Justin Vento
Background: Lactobacillus bacteria are gram positive, lactic acid producing bacteria that are widely studied due to their use in fermented foods and yogurts as probiotic agents. Within this genus, Lactobacillus plantarum is a gut-residing species that has been used to combat human gut infections. Recently, certain strains of L. plantarum have been shown to provide a distinct growth phenotype in infant mice, an observation that has elicited further research into this beneficial microbe-host interaction. In order to explore probiotic behavior of L. plantarum strains using in-vivo gut studies, these strains need to first be characterized and manipulated in-vitro. This requires advanced genetic tools such as genome editing in order to study inherent genetic behavior of these strains and select for a desired phenotype such as improved probiotic efficacy. Successful genomic mutations have been made to L. plantarum strains using integration cassettes and oligonucleotide recombination. However, the industrial use of these tools has been hindered by species-dependent behavior and low recombination efficiencies. In order to improve efficiency, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated) systems have been used with oligo-based genome editing in Lactobacillus reuteri to select against wild-type, non-mutated genomes. These adaptive prokaryotic immune systems have been engineered as genome editing tools in a variety of organisms. In L. reuteri, a Cas9 based system was designed to target and cleave wild-type strains, causing cell death, and allowing for survival of only desired mutant strains. However, relevant L. plantarum strains have suffered from low transformation efficiencies and too few recombination events occurring. Taken together, this oligonucleotide-based recombination method of genome editing in L. plantarum has proven difficult to implement, and advanced genetic tools are required to characterize and modulate these Lactobacilli strains in-vitro.
Results: In this study, a method was developed to advance genome editing in L. plantarum strains that could be directly used for in-vivo gut studies. Instead of relying on recombination to occur, a repair template was designed to incorporate the desired mutation upon Cas9 cleavage of wild-type strains. By relying on homology directed repair in L. plantarum, every cell is given the chance to incorporate the desired mutation, compared to roughly 1 in 60,000 cells found to achieve recombination in the relevant L. plantarum NIZO21. This method is implemented in several different strains of L. plantarum to generate and select for specific genetic mutations that improve growth. The resulting mutated strains are then analyzed in-vivo using Drosophila melanogaster larvae as models to assess this growth phenotype in the host’s gut.
Conclusions: We present several tools that can be used for biological experiments in intractable strains of Lactobacillus. Such in-vitro experiments can be used to explore how minute genomic mutations in Lactobacilli strains can lead to different phenotypic changes in-vivo. The pipeline presented here can also be adapted to improve genome editing tools in other microbes that exhibit significant strain-specific behavior.

Adam Wallace
Background: Immobilizing green algae in non-growing, thin multi-layer coatings on flexible, inexpensive substrates as novel biocomposite materials will improve their CO2-trapping and solar energy harvesting efficiency. To absorb CO2, coatings will be engineered to contain intracellular nanopores and microchannels to allow multiple layers of cells to absorb nutrients and CO2, and to remove secreted products – similar to the function of natural leaves. The goal is to understand the fundamentals of colloid + living cell assembly and create devices from algae that function as artificial leaves exceeding the CO2 uptake of Arabidopsis leaves (18 mmol/(m2 h) at 100 μmol photons/(m2 s)) [1]. We also plan on engineering the algae and coatings for dry stabilization, allowing extended dry-storage of highly concentrated algae as biocomposite photobiocatalysts. Long-term, algae will be engineered to recycle carbon as secreted products. The biomimetic leaf will enable an advanced bio-solar materials approach to improve the energy efficiency for CO2 capture and carbon recycling compared to existing photobioreactors.
Results: We have demonstrated photoreactive coatings of Chlorella vulgaris and Chlamydomonas reinhardtii, coated by thin film drawn down colloid deposition methods with a bimodal blend of high Tg latex particles, and a low Tg adhesive latex binder on surface-modified flexible polyester (PE). Coating film thickness is a critical parameter for deposition of multiple cell sizes. We have measured CO2 uptake of 5.0±0.9 and 1.5±0.2 mmol/(m2 h), cell densities of 2.5±0.8×1011 and 1.5±0.19×1010 cells/m2, thicknesses of 15±2 and 12±3 μm , and void space of 5.4±5.7 and 5.4±4.0 % for multi-layer C. vulgaris and monolayer C. reinhardti coatings respectively. From algae monolayer data, we predict that stacking ~10 layers of cells can exceed the CO2 uptake rate of leaves. Additionally, we are developing a multi-component colloid coating model using Mathematica to describe convective sedimentation assembly and Landau-Levich deposition processes based on the single-component model by Jerrim and Velev [2].
Conclusions: Photoreactive flexible coatings of green algae, high Tg latex particles, and low Tg latex binder generated using thin film draw out methods on flexible PE absorb CO2 when illuminated. This is the first step in developing deposition methods for multi-layer biomimetic leaves. By combining the proper ratios of latex binder, latex particles, and algae, and control of drying conditions, a nanoporous microstructure can be formed, allowing for reactivity in multiple cell layers and increased solar energy harvesting. These coatings will be combined with microchannels and engineered for dry stabilization to create a biocomposite device that can be stored for extended periods without refrigeration.
1. Eckardt, N.A., Snyder, G.W., Portis, A.R., and Ogren, W.L. (1997). Growth and Photosynthesis under High and Low Irradiance of Arabidopsis thaliana Antisense Mutants with Reduced Ribulose-l,5 -Bisphosphate Carboxylase/Oxygenase Activase Content. Plant Physiol. 113, no.2: 575-586
2. Jerrim, L.B. and Velev, O.D. (2008). Deposition of Coatings from Live Yeast Cells and Large Particles by “Convective-Sedimentation” Assembly. Langmuir 25, no.10: 5692-5702.


Ryan Maloney

Background: Colloidal self-assembly is a powerful tool that can be used to create new materials for a wide range of applications. Anisotropic particles, in particular, offer a way to precisely control the structure that forms during the self-assembly process. Binary mixtures that contain anisotropic, interacting particles have been proposed as a way to introduce multiple functionalities into the self-assembled structure. We simulate binary mixtures of dipolar rods and dipolar discs in two-dimensions using discontinuous molecular dynamics to determine how the assembled structures of these mixtures differs from those seen in single component systems [1-3]. Two different binary mixtures are investigated: a mixture of an equal number of dipolar rods and dipolar discs (“equal number”), and a mixture where the area fraction of dipolar rods is equal to the area fraction of dipolar discs (“equal area”).
Results: Phase boundaries between fluid, string-fluid, and “gel” phases are calculated and compared to the phase boundaries of the pure components. The equal number mixture displays phase changes from a fluid to a string-fluid and from a string-fluid to a “gel” at a slightly lower temperature than occur for single component dipolar rods. The equal area mixture shows these phase changes occurring at approximately the same temperature as single component dipolar discs. Looking deeper at the underlying structure of the mixture reveals complex interplay between the rods and discs and the formation of states where the two components are in different phases. The mixtures exhibit phases where both rods and discs are in the fluid phase, where rods form a string fluid while discs remain in the fluid phase, a rod string-fluid coexisting with a disc string-fluid, a “gel” that consists primarily of rods while the discs form either a fluid or string fluid phase, and a “gel” that contains both rods and discs.
Conclusions: Our results give insight into how binary mixtures can be utilized to create complex aggregates by varying the relative composition of the two components. By manipulating the properties of one of the components it should be possible to fabricate bifunctional, thermally responsive self-assembled materials. References:
1. Goyal, A., Hall, C. K., Velev, O. D. (2008). Phase diagram for stimulus-responsive materials containing dipolar colloidal particles. Physical Review E, 77: 031401-031401.
2. Schmidle, H., Hall, C. K., Velev, O. D., Klapp, S. H. L. (2012). Phase diagram of two-dimensional systems of dipole-like colloids. Soft Matter, 8: 1521-1531.
3. Rutkowski, D. M., Velev, O. D., Klapp, S. H. L., Hall, C. K. (2016). The effect of charge separation on the phase behavior of dipolar colloidal rods. Soft Matter, 12: 4932-4943.

Kaihang Shi
Background: In this work, we present a new two-dimensional Lennard-Jones equation of state (2D LJ-EOS) for the dense adsorbed layers for reduced density larger than 0.9. The new 2D LJ-EOS has a pure theoretical basis and there are no fitting parameters in it. The comparisons between the 2D LJ-EOS with Monte Carlo simulation show that the new 2D LJ-EOS is very accurate over a wide range of temperature in the high-density region. A criterion is also worked out to find the applicable temperature range for the new 2D LJ-EOS at a certain density. We also demonstrate one of the applications of this 2D LJ-EOS by using it to predict the effective tangential pressure of the contact layer near the wall in the slit pore system. The predicted value by the new 2D LJ-EOS agrees well with the reported peak value by the mechanical Irving-Kirkwood method for small pore-width systems.
Results: The two-dimensional Monte Carlo simulation (2D MC) results show a very good agreement with the 2D LJ-EOS calculations over a wide range of temperature in the high-density region. The effective tangential value predicted by the new 2D LJ-EOS agrees well with the reported peak tangential pressure value by mechanical Irving-Kirkwood route1.
Conclusions: The new 2D LJ-EOS proposed in this work is very accurate at high densities and it can be used as an alternative way to calculate the effective tangential pressure in the slit pore system.
1. Srivastava, D., Santiso, E. E., & Gubbins, K. E. (2017). Pressure Enhancement in Confined Fluids: Effect of Molecular Shape and Fluid–Wall Interactions. Langmuir, 33(42), 11231-11245.

Kinetics & Catalysis

Arnab Bose

Background: Xylan pyrolysis plays a crucial role in the pre-treatment of biomass. It falls under the class of hemicellulose copolymers, which are the least thermally stable components of lignocellulosic biomass. Different lumped models are available to understand xylan’s decomposition kinetics, but little insight into various reaction pathways can be obtained from those models [1]. To obtain a detailed view of its pyrolysis kinetics, extracted xylan from beech wood and D-xylose are flash-pyrolyzed (Pyroprobe, CDS Analytical) at 200 ̊C – 400 ̊C and gas-phase products are analyzed with GC x GC/TOFMS (Pegasus 4D, Leco).
Results: After the pyrolysis, various C/H/O compounds having zero carbon atoms (water) to eight carbon atoms were identified with at least 80 % confidence. In general, their chemical structures contain alcohol, carbonyl, ether and ester groups. Different saturated and unsaturated cyclopropanyl, cyclopentanyl, furyl, and pyranyl rings were also observed. The number of identified products was higher from xylan pyrolysis than from D-xylose pyrolysis. A higher number of linear compounds was identified in xylan pyrolysis. In order to understand the furfural yield, furfural from GC x GC/TOFMS was calibrated via the direct injection of methanol-
furfural solution. A much lower g/g % furfural yield was observed in xylan pyrolysis above 300°C than that of D-xylose.
Conclusions: The lower furfural yield in xylan pyrolysis above 300°C than that of D-xylose suggests that the xylopyranosyl backbone goes through end-chain scission, like cellulose [2].
1. E. Ranzi, A. Cuoci, T. Faravelli, A. Frassoldati, G. Migliavacca, S. Pierucci, S. Sommariva, “Chemical kinetics of biomass pyrolysis,” Energy & Fuels, 2008, 4292–4300.
2. C. Krumm, J. Pfaendter, P.J. Dauenhauer, “Millisecond pulsed films unify the mechanisms of cellulose fragmentation,” Chem. Mater., 2016, 28, 3108−3114.

Yunfei Gao

Background: Chemical looping oxidative dehydrogenation (CL-ODH) of ethane utilizes a transition metal oxide based oxygen carrier, also known as redox catalyst, to convert ethane into ethylene under an autothermal cyclic redox scheme. Unlike conventional ODH, CL-ODH eliminates the needs for gaseous oxygen, rendering a potentially more efficient process. We reported Li-promoted La0.6Sr1.4FeO4 (LaSrFe) as an effective redox catalyst for CL-ODH. However, its oxygen capacity is relatively low (<0.3 wt%) [1]. Results: The current study investigates Na or K as a promoter and finds similar promotional effects: alkali promoter notably increases the selectivity of the pristine LaSrFe but suppresses its oxygen carrying capacity. The K-promoted LaSrFe was further characterized with Low Energy Ion Scattering (LEIS) and 18O2-exchange experiments. LEIS analysis indicates that the surface layer contained exclusively of K2O whereas 18O2-exchange experiments confirm that the oxygen surface exchange and incorporation rates are significantly lower for K-promoted LaSrFe. Meanwhile, co-promotion of Li and K achieved up to 86% ethylene selectivity and 60% ethane conversion while maintaining an oxygen capacity of 0.65 wt%. This enhanced performance was ascribed to the higher oxygen capacity of K substituted LaSrFe and the higher selectivity induced with Li promotion. In addition to LaSrFe, other oxide substrates within the same Ruddlesden-Popper structure family were also investigated to determine the general effects of A-site and B- site compositions of the oxide substrate on the ODH performance of the alkali promoted redox catalysts.
Conclusions: Li and K co-promoted LaSrFe resulted in 86% ethylene selectivity and 60% ethane conversion while maintaining an oxygen capacity of ca. 0.65 wt%. These findings not only offer mechanistic insights on alkali metal promoted LaSrFe for CL-ODH of ethane but also resulted in promising redox catalysts for this novel process scheme.
1. Yunfei Gao, Luke M. Neal and Fanxing Li (2009). Li-Promoted LaxSr2–xFeO4−δ Core–Shell Redox Catalysts for Oxidative Dehydrogenation of Ethane under a Cyclic Redox Scheme. ACS Catalysis. 6, 7293–7302.

Vasudev Haribal

Background: Among the various processes for sustainable hydrogen generation, solar thermochemical water-splitting based on redox cycles of metal oxides represents an attractive approach. A key challenge for this process is the high temperatures needed for thermal decomposition of the metal oxide (>1200 °C) [1]. In addition, the need to balance the oxygen release and water-splitting properties of metal oxides often leads to low steam conversion. A hybrid solar-redox redox process for cogeneration of hydrogen and liquid fuels using methane and solar energy operates at lower temperatures and higher steam conversions [2]. In such a process, a reduced metal-oxide based redox catalyst is used to split water, producing concentrated hydrogen. The resulting (oxidized) redox catalyst is subsequently used to partially oxidize methane (POx step), forming syngas for Fischer-Tropsch synthesis. Over 58% syngas yield in the POx step and 77% steam to hydrogen conversion in the water-splitting step are achieved in a layered reverse-flow reactor configuration using La0.8Sr0.2FeO3-δ (LSF) supported Fe3O4 as the redox catalyst [2], [3]. Further improvements in syngas yield and steam-to- hydrogen conversion are desirable to improve the overall process efficiency.
Results: Density Functional Theory (DFT) calculations reveal that the equilibrium oxygen partial pressure (PO2) and oxygen vacancy formation energy (∆Evacancy) of perovskite-structured BaMnxFe1-xO3-δ are significantly different from those of FeO and MnO, and can be manipulated by varying the Fe:Mn ratios in the B-sites. These studies indicate that BaMn0.5Fe0.5O3-δ possesses desirable properties for the hybrid solar-redox scheme. Fluidized bed experiments demonstrate over 90% steam conversion in the water-splitting step and higher than 90% syngas yield in the methane POx step. In-situ XRD experiments show the activity and regenerative capability of BaMn0.5Fe0.5O3-δ under redox conditions. ASPEN Plus® simulations indicate the potential to obtain higher efficiencies than the state-of-the-art hydrogen and liquid fuel production processes with lower CO2 emissions.
Conclusions: We proposed and validated a rational strategy to optimize transition metal oxide based redox catalysts for water-splitting and syngas generation via a hybrid solar redox scheme.
1. W. C. Chueh et al. (2010), High-Flux Solar-Driven Thermochemical Dissociation of CO2 and H2O Using Nonstoichiometric Ceria, Science, 330:1797–1801.
2. F. He, J. Trainham, G. Parsons, J. S. Newman, and F. Li (2014), A hybrid solar-redox scheme for liquid fuel and hydrogen coproduction, Energy Env. Sci, 7:2033–2042.
3. F. He and F. Li (2015), Perovskite promoted iron oxide for hybrid water-splitting and syngas generation with exceptional conversion, Energy Env. Sci, 8:535–539.

Charles McGill

Background: Isomerization and decomposition kinetics of xylose and related model compounds are studied with computational quantum chemistry in this work as a window into elementary reactions of hemicellulose pyrolysis. Xylose and acetylated units of xylose are major monomer components in many varieties of the biopolymer hemicellulose. Conversion of plant biomass into biofuels is often carried out through the thermal process of pyrolysis. Chemical mechanisms for the decomposition of biomass and its constituent monomers have been widely studied but are generally presented as lumped models where the individual elementary reaction steps are not known. It is the goal of this work to develop a mechanism of elementary steps for xylose degradation. As one of the major constituents of hemicellulose in biomass, the development of thermal degradation mechanisms for xylose is important to the development of mechanisms for hemicellulose and biomass as a whole.
Results: Reactions were considered proceeding from the five major isomer structures of xylose. Reactions were also investigated in 2-acetylxylose and xylobiose, a dimer of xylose, as model molecules for the reactions of the acetyl groups in xylan and the breaking of the xylan glycosidic bonds. Both four- and six-centered pericyclic transition states were investigated. Quantum-
chemistry modeling was carried out using the Gaussian 09 software package. Initial structure exploration and optimization were carried out using DFT methods at a B3LYP/6-31 G(d,p) level of theory. Additional refinement of stable species and transition states was then carried out using the compound method CBS-QB3. Reaction rate constants were calculated for significant reactions using Mesmer master equation code.
Conclusions: The simulations revealed a variety of reaction pathways that apply in model molecules for xylan. Calculated rate constants show that acetyl groups can be eliminated from a xylan structure in the form of acetic acid with relative ease but that decarboxylation into methane and carbon dioxide does not proceed readily at normal pyrolysis temperatures. We also see a variety of mechanisms for the breaking of the xylan glycosidic bond, some of which require the inversion of a ring structure which implies a requirement for mobility in the xylan to proceed. These simulated reactions demonstrate the types of decomposition transitions which are at play in xylan pyrolysis and lead us to greater understanding of the system.

Seif Yusuf

Background: Oxidative dehydrogenation (ODH) of ethane represents a promising alternative to steam cracking for the production of ethylene that can result in a higher ethane conversion, lower energy consumption and lower CO2/NOx emissions. Conventional ODH, however, suffers from challenges in process safety, controllability, and high capital cost due to the needs to co-feed gaseous oxygen with ethane. In chemical looping ODH (CL-ODH), ethane is partially oxidized by active lattice oxygen in a redox catalyst, producing ethylene and water. The reduced redox catalyst is subsequently re-oxidized with air in a separate reactor prior to the initiation of another redox cycle. Such a cyclic redox scheme eliminates the needs for cryogenic air separation as well as O2 co-feeding. In this process, it is crucial to suppress deep oxidation without sacrificing ethane conversion. This study focuses on testing and characterization of Mg6MnO8 based redox catalysts for the CL-ODH of ethane.
Results: Mg6MnO8 based redox catalysts were able to improve single pass ethane conversion compared to thermal cracking. When promoted with sodium tungstate, the redox catalyst was able to increase the ethylene single pass yield by 38.9% when compared to thermal cracking. Ethane TPR suggests that the reaction pathway for the sodium tungstate promoted redox catalyst is parallel thermal cracking and selective combustion of hydrogen. X-ray Photoelectron Spectroscopy (XPS) and Low Energy Ion Scattering (LEIS) analyses indicate that the sodium tungstate promoter suppresses the amount of surface manganese and reduces the average manganese oxidation state. These results indicate that the sodium tungstate promoter suppresses the amount of surface Mn4+ which is responsible for the unselective electrophilic oxygen species.
Conclusions: Our study indicates that CL-ODH can reduce the CO2 and NOx emissions for ethylene production by as high as 87%[2]. Design and optimization of effective redox catalysts are crucial for successful development of such a promising process. The current study not only reports a highly effective redox catalyst, but also reveal the underlying mechanism for such a redox catalyst. The findings can be significant for further improvements of redox catalyst performances in CL-ODH.
1. Neal, L. M.; Yusuf, S.; Sofranko, J. A.; Li, F. Energy Technol. 2016, 4 (10), 1200–1208.
2. Haribal, V. P.; Neal, L. M.; Li, F. Energy 2017, 119, 1024–1035.


Jeffrey A. Bennett

Background: Metal-mediated cross-coupling reactions are valuable tools to organic chemists and play a critical role in synthesizing numerous complex chemical compounds in the pharmaceutical industry. [1] Flow chemistry has recently emerged as an effective strategy for continuous manufacturing of pharmaceutical targets. [2,3] However, the current limitations of continuous flow chemistry approaches, including challenging catalyst recovery in the case of homogenous catalysis, complex immobilization chemistry in the case of heterogenous catalysis in combination with the extensive utilization of volatile and toxic organic solvents, and relatively high operation pressures associated with packed-bed reactors (PBRs) necessitate the development of more efficient and environmentally friendly continuous flow technologies for organic synthesis. Recently, it has been demonstrated that Pd-loaded silicone-based elastomers can be utilized as the catalyst for heterogenous carbon-carbon cross-coupling reactions in batch. [4]
Results: Pd-loaded polyhydromethylsiloxane (PHMS) microparticles of tunable size and elasticity are prepared in a capillary-based coaxial flow-focusing microfluidic device constructed using off-the-shelf components. Simultaneous droplet formation and chemical cross-linking processes are performed by tuning the dilution of the cross-linking catalyst in the annular flow of the microreactor, resulting in PHMS microparticles synthesized in a single step. The size of the elastomeric microparticles can be tuned by adjusting the flow rate ratio of the polymer and cross-linker mixture to water, while the elasticity can be tuned by the polymer to cross-linker ratio as well as the flow rate ratio of the polymer mixture to cross-linking catalyst mixture. Microparticle elasticity is characterized by the degree of solvent uptake. Application of the synthesized PHMS microparticles in organic synthesis is demonstrated by producing monodispersed Pd-loaded microparticles and utilizing them as microreaction vessels for continuous Suzuki-Miyaura cross-coupling in a Pd-loaded microparticle-packed bed reactor (μ-PBR).
Conclusions: The prepared catalytic Pd-loaded PHMS microparticles demonstrated the application of the developed method for producing chemically cross-linked polymer microparticles, as well as in continuous organic synthesis by performing Suzuki-Miyaura cross-coupling reactions in flow under mild conditions. Additional work must be done to optimize reaction conditions for maximum yield, but these results show promise as a proof of concept for the production of novel polymer microparticles with a wide range of applications.
1. P. Ruiz-Castillo and S. L. Buchwald, Chem. Rev., 2016, 116, 12564–12649.
2. A. Adamo, R. L. Beingessner, M. Behnam, J. Chen, T. F. Jamison, K. F. Jensen, J.-C. M. Monbaliu, A. S. Myerson, E. M. Revalor, D. R. Snead, T. Stelzer, N. Weeranoppanant, S. Y. Wong and P. Zhang, Science, 2016, 352, 61 LP-67.
3. K. F. Jensen, AIChE J., 2017, 63, 858–869.
4. I. Stibingerova, S. Voltrova, S. Kocova, M. Lindale and J. Srogl, Org. Lett., 2016, 18, 312–315.

E. Daniel Cárdenas-Vásquez


Cathryn Conner

Background: We are developing a new generation of functionalized environmentally benign nanoparticles (EbNPs) for biotechnology. Unlike traditional nanoparticles, environmentally benign nanoparticles made of lignin can degrade after they have been used, so there is no toxic impact on the environment or humans, which may result from inorganic nanoparticles. Similar types of EbNPs were developed in the Velev group and have been investigated as a type of highly efficient antimicrobials [1]. Silver ions were infused into the lignin core and coated with polyelectrolyte for use as an antibacterial; this was done to reduce the usage of silver nanoparticles, which remain in the environment causing damage by continuously releasing more silver ions. Our goal is to use EbNPs as delivery vehicles for agrochemicals with reduced costs and waste. Our first efforts were directed to the development of a semi-continuous flash precipitation process. We then used chitosan, a biopolymer with established anti-microbial activity, to change the surface charge of EbNPs samples from negative to positive in order to help them adhere to the negativelycharged surfaces of leaves. After characterizing the drying patterns on a model surface, we applied both uncoated and coated nanoparticles to geranium leaves as a possible means of preventing damage from the fungus Botrytis.
Results: The semi-continuous system we created is very easily used for flash precipitation formation of lignin nanoparticles in a controlled way. These nanoparticles have a very uniform size distribution thanks to the non-LaMerian precipitation mechanism. Our experiments with model surfaces demonstrate pronounced differences in the adhesive properties and spreading patterns between non-functionalized nanoparticles and EbNPs coated with chitosan. In our spreading on geranium leaf experiments, however, the non-coated nanoparticles performed best, providing a surprisingly simple and efficient means of leaf protection.
Conclusions: We have introduced a facile process for rapid engineered nanoparticle formation and found that coating EbNPs with chitosan successfully changes surface charge and spreading pattern on glass slides. Further experiments are needed to explain the underlying mechanism that leads to the high efficiency of the uncoated nanoparticles. In the future, we aim to develop EbNPs that target specific features on leaf surfaces, such as trichomes and stomata, based on customized nanoparticle-leaf component interactions.
1. A. P. Richter, J. S. Brown, B. Bharti, A. Wang, S. Gangwal, K. Houck, E. A. C. Hubal, V. N. Paunov, S. D. Stoyanov and O. D. Velev, Nature Nanotech., 10, 817-823 (2015). Nanoengineered antimicrobial nanoparticles with environmentally benign cores infused by silver ions.

Ria D. Corder

Background: Uterine fibroids are benign tumors composed of disordered collagens which occur in 70-80% of women before age 50, and can interfere considerably with daily life by causing bleeding and pain. Fibroids are the leading cause for hysterectomy, and $9.4 billion is spent annually in the US for treatment [1]. Fertility-preserving treatment options, such as hormone or drug therapies, are currently limited in effectiveness. Highly purified collagenase Clostridium histolyticum (CCH) has received FDA approval for two medical indications involving digestion of interstitial collagens to reduce tissue stiffness. However, repeat CCH injections are usually required to achieve efficacy [2], so the delivery system needs to be improved. To do so, we are co-injecting LiquogelTM (LQG), a thermoresponsive polymer that transitions upon heating from an injectable solution to a gel. Our hypothesis is that LQG will enhance enzymatic degradation of uterine fibroids by CCH in-vivo by entrapping CCH within fibroids. We used rheology to quantify the degree of in-vivo degradation of uterine fibroid tissue. Rheology is a measurement technique that characterizes the viscoelastic behavior of materials, though it is not commonly used on biological samples. Fibroids were obtained from human women undergoing hysterectomies, surgically implanted into mice, and injected with one of four treatments: phosphate buffered saline at pH 7.4 (PBS), PBS+CCH, LQG (in PBS), and LQG+CCH. At set day intervals, fibroids were removed and saved for rheology. Fibroids were measured while under immersion in PBS at 37 ºC on a DHR-3 rheometer.
Results: All fibroids showed gel-like behavior, including those treated with CCH. We compared the average tissue moduli of the 3-4 samples in each treatment group. After 7 days, PBS+CCH reduced the tissue modulus relative to PBS, and LQG+CCH reduced the modulus relative to LQG. It was inconclusive whether LQG+CCH degraded fibroids more than PBS+CCH as the differences were not statistically significant.
Conclusions: We performed an in-vivo study of uterine fibroid digestion by CCH and tested the hypothesis that LQG would enhance fibroid digestion by CCH. Preliminary data comparing LQG+CCH to PBS+CCH is inconclusive, so more in-vivo studies are needed. Our results indicate that rheology is a useful tool for characterizing the modulus of biological tissues. Future work includes histological staining and enzyme release studies, which will help us better evaluate the efficacy of our novel treatment for uterine fibroids.
1. Cardozo, E. R. et al. (2012). The Estimated Annual Cost of Uterine Leiomyomata in the United States. Am. J. Obstet. Gynecol., 206: 211.e1-211.e9.
2. Jayes, F. L. et al. (2016). Loss of stiffness in collagen-rich uterine fibroids after digestion with purified collagenase Clostridium histolyticum. Am. J. Obstet. Gynecol., 215: 596.e1-596.e8.

Camden Cutright

Background: Nonwoven fabrics are a flexible, porous, inexpensive substrate for high performance membranes [1]. Despite their mechanical benefits, however, these fabrics lack the innate chemical complexity required to differentiate species from one another [2]. Thus, we seek to incorporate “smart” hydrogels [3] within the nonwoven void space to create a novel separation system. Endowed fabric will monitor the local environment and reversibly alter its permeation kinetics in accordance with the measured stimuli.
Results: We have successfully synthesized hydrogels of 300-3000 nm in size comprising varying amounts of NIPAM, Acrylic Acid, and Bis-acrylamide [4]. Using Fourier Transform Infrared Spectroscopy in combination with elemental analysis, we have determined the effective incorporation percentage of each monomer within the polymer network. Finally, we have implemented dynamic light scattering to analyze the gel’s swelling response with respect to changes in temperature, pH, and salinity. We show that by altering only the chemical composition of the hydrogels, we can control the relative response to each environmental stimulus.
Conclusions: We have developed smart hydrogels with reversible multi-stimuli responsive nature. Following rheological characterization of the viscoelastic nature of these gels, we will begin incorporation into nonwoven fabric to test the resulting efficacy of the proposed membranes.
1. Gibson, P., Schreuder-Gisbson, H., Rivin D. (2001) Transport properties of porous nonwovens based on electrospun nanofibers, Colloids and Surfaces A, 187: 469-481.
2. Singh, A. V., Rahman, A., Kumar S., Aditi, A., Galluzzi. M., Bovio. S., Barozzi S. Mantani, E., Parazzoli, D., (2012) “Bio-inspired approaches to design smart fabrics,” Mater. Des., 36: 829–839
3. Creton, C., (2017) 50th Anniversary Perspective: Networks and Gels: Soft but Dynamic and Tough, Macromolecules, 50: 8297-8316.
4. Brown, A.C., Stabenfeldt, S.E., Ahn, B., Hannan, R., Dhada, K., Herman, E., Stefanelli, V., Guzzetta, N., Alexeev, A., Lam, W.A., Lyon, L.A., Barker, T.H. (2014) Ultrasoft microgels displaying emergent platelet-like behaviours. Nature Materials, 12: 1108-14.

Ryan Dudek

Background: As an alternative to endothermic cracking and dehydrogenation processes, oxidative dehydrogenation (ODH) offers excellent potential to reduce primary energy consumption and pollutant emissions (CO2 and NOx) from olefin production. Chemical looping-oxidative dehydrogenation (CL-ODH) is a process scheme for ODH consisting of an ODH step and a regeneration step in a cyclic reduction-oxidation mode. The ODH step can proceed either by catalytic ODH or by dehydrogenation coupled with selective hydrogen combustion (SHC).
Results: Selective hydrogen combustion (SHC) in the presence of light hydrocarbons was demonstrated with a series of Mn-containing mixed oxide redox catalysts in the context of a chemical looping-oxidative dehydrogenation (CL-ODH) scheme. Unpromoted and 20 wt.% Na2WO4-promoted Mg6MnO8, SrMnO3, and CaMnO3 exhibited varying SHC capabilities at temperatures between 550°C–850°C. Reduction temperature of unpromoted redox catalysts increased in the order Mg6MnO8 < SrMnO3 < CaMnO3. Promotion with 20 wt.% Na2WO4 resulted in more selective redox catalysts capable of high-temperature SHC. XPS analysis revealed a correlation between suppression of near-surface Mn and SHC selectivity. Na2WO4/CaMnO3 showed steady SHC performance (89% H2 conversion, 88% selectivity) at 850°C over 50 redox cycles. In series with a Cr2O3/Al2O3 ethane dehydrogenation catalyst, Na2WO4/CaMnO3 combusted 84% of H2 produced while limiting COx yield below 2%.
Conclusions: The redox catalysts reported can be suitable for SHC in a cyclic redox scheme for the production of light olefins from alkanes.
1. Stark, Tony L., Pepper Potts, and Nicholas Fury (2009). The Avengers Initiative. J. Marvel Cinemat. Univ., 5: 101-112.
2. Skywalker, Anakin and Padmé Amidala (2006). Creating the Next Generation of Jedi. J. Lucasfilm Arts, 38: 421- 424.

Robert W. Epps

Background: Over the past decade, colloidal semiconductor nanocrystals have rapidly grown in prominence as potential low-cost replacements for the materials used in photovoltaics (PVs) and light emitting diodes. More recently, perovskites, due to their favorable charge carrier mobilities and lifetimes, have emerged from this material class as a promising candidate for third-generation, high-efficiency PVs. However, research in colloidal perovskite synthesis routes has yet to develop a fundamental and comprehensive understanding of their nucleation and growth processes, thereby inhibiting development of commercial manufacturing methods. Traditional flask-based characterization approaches are both high in labor and chemical costs and present significant variability in mass transfer properties. As a result, microfluidic platforms have been explored as a more favorable alternative towards efficient and comprehensive reaction screening. Herein, we present a high-throughput microfluidic screening device, which is applied towards the systematic characterization of a case study, room temperature perovskite synthesis. [1]
Results: The continuous flow syntheses occur within an off-the-shelf tubular microreactor, which feeds into either a T-junction for single- or a customized cross-junction for multi-phase flow analyses. The platform features a novel translating flow cell, which enables inline fluorescence and absorption characterization along an adjustable reactor length. The system is comprised of modular components, which may be replaced and rearranged with customized units, such as reactor extensions that allow for the tubular reactor length to vary from 3 cm to 2 m all within the 30-cm platform. This highly adjustable reactor design, paired with the inherent advantages of microfluidic devices have allowed the platform to reach a sampling rate of up to 30,000 unique spectra per day, access residence times spanning 100 ms to 17 min (four orders of magnitude), and perform its characterization with a chemical consumption as low as 2 μL per spectra. Furthermore, the adjustable sampling point has allowed us to decouple velocity dependent mass transfer – primarily attributed to the recirculation pattern in gas-liquid segmented flow – from residence time. As a result, we have for the first time effectively and systematically detailed kinetically tunable nanocrystal growth pathways within the case-study synthesis. Emission wavelengths varied as much as 25 nm at equivalent residence times due exclusively to variations in mass transfer rates.
Conclusions: Through the development and application of this high-throughput characterization platform, we have begun to access the massive parameter space associated with perovskite nanocrystal formation. Additionally, through the highly flexible system design we have effectively demonstrated a novel feature of perovskite syntheses, which will likely direct future characterization efforts towards greater mass transfer controls. Further applications of this system will expand access in the parameter space towards enhanced understanding and control of nanocrystal synthesis in continuous nanomanufacturing processes.
1. Epps, Robert W., Kobi C. Felton, Connor W. Coley, and Milad Abolhasani (2017). Lab Chip (Advance Article).

Sabina Islam

Background: Aromatic polyesters are one of the most important classes of polymers in textile and packaging industries due to their superior mechanical, optical, and processing properties. Such specialty polyesters were rendered water-dispersible by functionalizing the polymer backbone with ionic monomers in order to comply with the low-VOC movement. As a result of being partially water-soluble, these polyesters form self-assembled nanoscale particles in water without the requirement of any additional stabilizer(s). These extremely small sized (e.g., 20 ~ 50 nm) nanoparticles are composed of hundreds of polymer molecules and offer various colloidal and morphological properties that are significantly different from conventional emulsion polymerized latex particles. For instance, their nanometer dimensions can be useful for developing nanocoatings with interesting optical properties such as structural colors.
Results: We fabricated nanofilms of brilliant structural colors using these waterborne polyester dispersions via facile convective deposition method. We correlated the microscale thickness of these thin films to their macroscale optical properties via the thin film interference theory. Additionally, we observed evaporation induced coffee-ring effect as the addition of water droplets on such thin-films redispersed the nanoparticles spontaneously. Driven by the capillary flow, water evaporation redistributed the polymer particles, creating multiple colorful ring patterns which correspond to the different thickness of the films. As expected, this phenomenon was suppressedin presence of electrolytes. Such redistribution of polymer films indicates possible damage to an uncross-linked film by an aqueous environment. Using structural color as a means to understand this polymer redistribution in detail, we further explored the coffee-ring patterns as a function of the polymer composition and concentration and electrolyte concentration.
Conclusions: This research is important in understanding the fundamental mechanism of film formation by these waterborne polymer nanoparticles. Moreover, the findings of our study open a new possibility and application of such environmentally-friendly waterborne dispersions in paintings, photonic paper, and optical displays

Salvatore Luiso

Background: While significant research efforts have focused on the negative and positive electrode materials in rechargeable Lithium-ion (Li-ion) batteries, battery separators have only recently received more consideration from the scientific community. The separator plays a critical role in Li-ion batteries by preventing physical contact between the positive and negative electrodes while permitting efficient ionic transport across the separator. There are four major types of separators: microporous polymeric membranes, nonwoven polymeric mats, gel-polymer electrolytes and composite membranes. Relative to the more conventional microporous membrane separators, nonwovens have the advantage of low cost, low mass and high porosity; in addition, the fibrous mat provides good structural cohesion due to its intertwined fibers. Although most polymers used to make nonwoven battery separators have resulted in lower cell performance (lower ionic conductivity and higher resistance) than conventional microporous separators, polyvinylidene difluoride (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. The best manner to produce nonwoven PVDF would employ a melt-blowing process, which is a well-developed, high-volume production technology. To be melt-blowable, polymer resins must have high melt-flow rates but commercial PVDF resins did not possess this property until recently. Nevertheless, researchers have successfully electrospun PVDF from a solution with the goal of exploring this promising polymer as a nonwoven battery separator.
Results: We are investigating the fundamental properties and characteristics of a novel melt-blowable PVDF grade (Kynar® RC 10,287 from Arkema) with the objective of elucidating its structure-property-process relationships and studying their performance as separators in Li-ion batteries. We produced meltblown PVDF with Kynar RC 10,287 and consolidated the mats with thermal bonding. We studied thickness, air permeability, fiber diameter, SEM, impedance. Fibers with smaller AFD show a smaller mean flow pore diameter and have a higher porosity.
Conclusions: By changing DCD, throughput, and air pressure while melt-blowing, fibers with diameters <400 nm were produced. Average fiber diameter was found to be as low as 2 μm_._ _A_i_r_ _permeability, porosimetry and electrolyte uptake measurements showed that a lower fiber diameter is desirable. This leads to a higher electrolyte uptake, which enables the battery to store more Li-ions and have a higher performance. Higher surface area and capillary effect of nanofibers might also contribute. A small mean flow pore diameter enables a more efficient ion transport by decreasing the chances of dendrite formation and increasing the tortuosity. References:
1. H. Lee, M. Yanilmaz, O. Toprakci, K. Fu, X. Zhang, (2014) A review of recent developments in membrane separators for rechargeable lithium-ion batteries, Energy Environ. Sci., 2014, 7, 3857–3886

Jason Miles

Background: Many chemical and biological processes rely strongly on surface interactions, such as wettability and adhesion. The use of chemical and surface energy gradients allows for a wide range of parameters to be evaluated on a single substrate. This high-throughput approach allows for faster screening and discovery of materials and surface phenomena. Gradients on surfaces can be used to direct dynamic phenomena on surfaces, such as the motion of water droplets [1] and cells [2]. These gradient surfaces are most commonly formed through the use of self-assembled monolayers (SAMs) or polymer brushes [3]. A successful method for this application must result in a gradient, which is easy to prepare, should provide sufficient control over the profile of the gradient, and should allow for specific chemistries to be placed on the surface to be used for the appropriate application [4].
Results: We have fabricated wettability gradients on hard substrates by a simple, two-step procedure. This process involves the deposition of homogeneous silane SAMs from followed by the formation of a surface coverage gradient through the selective removal of silanes from the substrate. Removal of silanes was achieved using a tetrabutyl ammonium fluoride (TBAF) solution to cleave the Si-O bond at the surface. The kinetic of degrafting have been modeled by using a series of first order rate equations, based on the number of attachment points broken to remove a silane from the surface. Degrafting of mono-functional silanes exhibits a single exponential decay in surface coverage; however, there is a delay in degrafting of tri-functional silanes due to the presence of multiple attachment points.
Conclusions: Wettability and chemical gradients can be achieved by selectively degrafting homogeneous silane SAMs. The gradient profile can be tuned by varying the degrafting temperature and time. We observe a relatively homogenous coverage of silane throughout the process, when compared to additive approaches of gradient formation. We design and form linear gradients in silane coverage to demonstrate the reproducibility and tuneability of this approach.
1. Chaudhury, M. K. & Whitesides, G. M. How to make water run uphill. Science 20, 38–59 (2013).
2. Lee, E.-J., Chan, E. W. L., Luo, W. & Yousaf, M. N. Ligand slope, density and affinity direct cell polarity and migration on molecular gradient surfaces. Rsc Adv. 4, 31581–31588 (2014).
3. Genzer, J. & Bhat, R. R. Surface-bound soft matter gradients. Langmuir 24, 2294–2317 (2008).
4. Bhat, R. R., Fischer, D. a. & Genzer, J. Fabricating planar nanoparticle assemblies with number density gradients. Langmuir 18, 5640–5643 (2002).

Petr Novotny

Background: Ethylene is a basic building block in the petrochemical industry; annual production of ethylene exceeds 150 million tonnes—more than any other organic compound [1]. Oxidative dehydrogenation (ODH) of ethane offers large potential reductions in energy consumption and associated greenhouse gas emissions when compared to conventional steam cracking for ethylene production [2]; however, catalytic ODH of ethane using co-fed O2 requires expensive air separation. As an alternative, we are investigating novel core-shell catalysts that utilize lattice oxygen (O2-) as the sole oxidant and operate in a cyclic redox mode.
Results: In this work, redox catalysts having 1, 3 and 6 monolayer (ML) equivalents of MoO3 on α-Fe2O3 and a stoichiometric ferric molybdate, Fe2(MoO4)3, were prepared, characterized by powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and temperature-programmed reduction (TPR) and evaluated for ethane ODH in a cyclic redox mode at 600°C. The characterization data are consistent with a core-shell structure for the calcined MoO3/Fe2O3 catalysts with a mixed iron-molybdenum oxide surface layer. H2 and ethane TPR evidence that the shell inhibits Fe2O3 reduction and decreases the ethane combustion activity of the fully oxidized catalyst. Covering the Fe2O3 core with MoO3 also increases ODH activity and ethylene selectivity. In cyclic redox mode at 600°C, ethylene selectivity was 57–62 % for catalysts with 3 and 6 ML equivalents of MoO3.
Conclusions:After calcination at 500-600°C, prepared core-shell catalysts have MoOx-rich surface layers comprised of Fe2(MoO4)3 and MoO3 species—the latter more prominent at higher loadings. α-Fe2O3 is reduced by H2 at low temperatures (~350°C) and tends to produce deep oxidation products from ethane. By covering the Fe2O3 core with MoOx-rich layers, catalyst reducibility is suppressed, and ethylene selectivity increases significantly up to 57–62 % for catalysts with 3 and 6 ML equivalents of MoO3. Ethane ODH activity also was higher for MoO3/Fe2O3 catalysts than for α-Fe2O3 suggesting that a mixed Mo-Fe oxide surface provides nadditional benefits beyond suppressing ethane combustion.
1. H. Zimmermann, R. Walzl, in:, Ullmann’s Encycl. Ind. Chem., Wiley-VCH Verlag GmbH & Co. KGaA, 2000.
2. C.A. Gärtner, A.C. van Veen, J.A. Lercher, ChemCatChem 5 (2013) 3196–3217.

Yunhu Peng

Background: Natural cartilage is durable and elastic, providing a low friction coefficient to moving joints under frequent applications of heavy loads1-3. However, the physical mechanisms contributing to this low friction coefficient is not well understood. We hypothesize that the nonideal surface geometry of cartilage gives rise to its low friction coefficient in certain directions of motion. We design soft poly(dimethyl siloxane) (PDMS) substrates with lithography to study the influence of surface geometry on their frictional and lubrication properties. The PDMS surfaces consist of stripes with controlled dimensions and spacings between each other.
Results: Tribological tests performed with a thin layer of aqueous glycerol solution at different concentrations between the PDMS substrates show that the friction coefficient is a function of the sliding speed. However, we find that the tribological behavior does not follow the type of Stribeck curve that is typically observed in soft materials with flat surfaces.
Conclusions: The hysteresis from the surface geometry could be one of the reasons for this deviation4. To test this hypothesis, we develop a spring-dashpot model that represents viscoelastic contributions from the multiple surface length scales. Another reason for this deviation could be a small scale elastohydrodynamic lubrication5. By incorporating scaling analysis, we proved that the second explanation might be valid too.
1. Sophia Fox, A. J., Bedi, A. & Rodeo, S. A. The basic science of articular cartilage: structure, composition, and function. Sports Health 1, 461–8 (2009).
2. Katta, J., Jin, Z., Ingham, E. & Fisher, J. Biotribology of articular cartilage-A review of the recent advances. Med. Eng. Phys. 30, 1349–1363 (2008).
3. Murakami, T. & Suzuki, A. Superior Tribological Behaviors Of Articular Cartilage And Artificial. Encycl. Biocolloid Biointerface Sci. 2V Set 1, 278–291 (2016).
4. Persson, B. N. J. Theory of rubber friction and contact mechanics. J. Chem. Phys. 115, 3840–3861 (2001).
5. Scaraggi, M., Carbone, G. & Dini, D. Experimental evidence of micro-EHL lubrication in rough soft contacts. Tribol. Lett. 43, 169–174 (2011).

Shravan Pradeep
Background: There has been a growing interest in ‘smart materials’ that undergo macroscopic changes in properties upon application of external stimuli. Nano and micron-sized particles, known as colloids, are ideal candidates to study how matter organizes themselves because of their perfectly controlled shapes and interactions. Colloids modified with light-activated azobenzene (AB) groups are hypothesized to switch between different types of phases, which can lead to macroscopic changes in material properties on demand. In this work, we would like to present two colloidal systems that we are working on: PMMA based hard-spheres and PDMS based o/w nanoemulsions.
Results: PMMA colloids are synthesized by dispersion polymerization technique and is stabilized using polymer brushes, such as PDMS and PHSA. The particles and stabilizers are characterized using NMR (chemical structure), GPC (molecular weight and stabilizer brush length), end group acid number analysis (for optimizing extent of reaction) and SEM (particle size and morphology). The PDMS based o/w nanoemulsions are synthesized using ultrasonication by varying the SDS concentration (50-250 mM), volume fraction of oil phase (φ _=0.05 to 0.4) and sonication time (4-20 min). The synthesis parameters are optimized by characterizing the particle size (using Dynamic Light Scattering) for the abovementioned parametric space.
Conclusions: In the next step, we would like to introduce light-responsive Azobenzene groups to these colloidal particles. Since photoresponsiveness can be localized in time and space, the proposed AB based photo-rheological fluids can be incorporated in micro/nanoscale devices such as smart textiles, responsive body armor, patternable materials, drug delivery systems, soft robots, tissue engineering and lab-on-chip devices.
1. P. N. Pusey and W. van Megan (1986), Phase behavior of concentrated suspensions of nearly hard-sphere colloids, Nature 320: 340-342.
2. Rafal Klajn, Kyle J. M. Bishop, and Bartosz A. Grzybowski (2007), Light-controlled self-assembly of reversible and irreversible nanoparticles suprastructures, Proc Natl Acad Sci USA. 104: 10305-10309.
3. Matthew E. Helgeson, Shannon E. Moran, Harry Z. An and Patrick S. Doyle (2012), Mesoporous organohydrogels from thermogelling photocrosslinkable nanoemulsions, Nat. Mater. 11: 344-352.

Minyung Song
Background: Compared to other liquids (e.g. water, ionic liquids, organic liquids), liquid metals have outstanding thermal and electrical conductivity, as well as distinct optical properties (i.e. reflectivity). Liquid metals generally have low viscosity (similar to water), yet many form surface oxides that alter the rheological properties in a manner that enables them to be patterned into non-spherical shapes. The resulting shapes maintain metallic electrical conductivity while being deformed significantly and can therefore be used as stretchable wires, interconnects, and antennas. Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales. Here, we focused on electrochemical control of surface oxidation because the formation of the surface oxide significantly lowers the interfacial tension [1]-[3]. This method requires minimal energy, and provides rapid and reversible control of interfacial tension over an enormous range compared to conventional molecular surfactants.
Results: Electrocapillarity is the change of interfacial tension of a fluid (e.g., Hg in water) caused by charges across the metal / electrolyte interface (i.e. electrical double layer). This capacitive effect lowers interfacial tension proportionally to the square of the potential across the interface and allows us to observe 6 different configuration of liquid metal jet. EGaIn jet forms large spherical shape (large drops) to minimize the surface area at low electric potential. The droplet size diminishes with an increase of potential, indicative of a decrease in interfacial tension [1]. Drops smoothly transitions to a new steady state (wire) through connected drops as interfacial tension drops significantly. At larger value of electric potential (>0.8V), the wire eventually deforms and turn into blobs as oxide layer gets thicker. So-called “tree-form wires” form only at the low flow rate after the “Wire Regime”. We successfully analyze each distinct regime of EGaIn jet as a function of flow rate and electric potential.
Conclusions: The ability to deposit or remove the oxide electrochemically enables unprecedented control over interfacial activity, which provides a means to reconfigure and manipulate the shape and position of liquid metal. Our results indicate configuration of EgaIn jet can be controlled by adjusting the not only electrical potential but also flow rate. Because liquid metal can maintain conductivity during deformation, they offer the possibility to create soft and stretchable analogues of rigid conductors.
1. Eaker, Collin B., mohammad R. Khan, and Michael D. Dickey (2016). A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction. J. Vis. Exp., 107
2. Eaker, Collin B., David C. Hight, John D. O’Regan, Michael D. Dickey, and Karen E. Daniels (2017). Oxidation-Mediated Fingering in Liquid Metals. Phys. Rev. Lett. 119: 174502-174505.
3. Khan, Mohammad R., collin B. Eaker, Edmond F. Bowden, and Michael D. Dickey (2014). Giant and switchable surface activity of liquid metal via surface oxidation. Proc. Natl. Acad. Sci., 111: 14047–14051.

Bharadwaja Srimat Tirumala Peddinti
Background: Increase of antibiotic resistance in pathogens has directly impacted healthcare industry. With only a few novel discoveries in the field of antibiotics since last two decades, often referred to as the discovery void, drug-resistance in pathogens has increased. Previously, infections that were easily treatable have now become fatal. Infections caused by antibiotic-resistant pathogens can occur anywhere, but, it is observed to take maximum effect in healthcare settings such as hospitals and nursing homes. Adherence and proliferation of microbes on surfaces such as counter tops, drapes, linens, door handles, monitory and sanitation equipment in health-care settings contribute to increase in HAIs [1]. As increase in microbial drug resistance causes conventional methods of treatment to fail, researchers are looking at alternative routes to tackle the infections. Photodynamic therapy (PDT) is such a technique that uses a photosensitizer (PS) and a light source, to treat medical conditions such as acne, wet-age macular degeneration and initial stages of skin cancer. Initially, the PS is applied on a target area of cancer cells. Subsequently, the target area is illuminated by visible light (typically of red color), thus, activating the PS [2]. The activated PS, through interactions with ground state triplet oxygen diffusing through the cells, converts it into singlet state oxygen. Being very reactive, singlet oxygen can oxidize various components in the cancerous cells leading to its death [3]. Rather than a cure by intracellular absorption, we intend to incorporate the PS on surfaces that will result in inactivation of microbes by continuous surface disinfection and serve as a preventive measure.
Results: In this study, we have incorporated a PS, Zinc tetra(4-N-methylpyridyl)porphine (ZnTMPyP4+), in an olefin block copolymer (OBC), INFUSE 9107. Melt pressed PS/polymer films were prepared. Thermal gravimetric analysis (TGA) revealed that OBC and ZnTMPyP4+ were thermally stable up to 330C and 250C respectively. Scanning electron microscopy (SEM) and Energy-dispersive x-ray spectroscopy (EDX) analysis showed dispersion of ZnTMPyP4+ on the surface of the films. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis revealed higher concentration of ZnTMPyP4+ on surface relative to the bulk concentration. Five bacterial and two viral strains were tested and all showed at least 99.9% inactivation after 60 min exposure to non-coherent visible light.
Conclusions: OBC, typically manufactured for nonwoven applications and ZnTMPyP4+ being thermally stable up to 450C, are potential materials to produce melt spun fibers. Higher concentration of PS leads to increased antimicrobial efficacy. Hence, surface migration of ZnTMPyP4+is beneficial to the antimicrobial efficacy of films. The films showed excellent antimicrobial properties at ~1% w/w ZnTMPyP4+ concentration.
1. Kramer, A., Schwebke, I., Kampf, G. (2006) How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect. Dis., 6: 130.
2. Nicolas Solban, I. R. T. H. (2006) Targeted photodynamic therapy. Lasers Surg. Med., 38: 522-531.
3. Jori, G., Coppellotti, O. (2007) Inactivation of Pathogenic Microorganisms by Photodynamic Techniques: Mechanistic Aspects and Perspective Applications. Anti-Infect. Agents Med. Chem., 6: 119−131.

Wenyi Xie

Abstract: The semiconductor industry is facing the challenge of manufacturing transistor devices with sub-10 nm high aspect ratio features. Understanding and developing self-limiting etching processes that allow precise control over the thickness of materials removed is essential for enabling the manufacturing complex transistor structures. In this work, we investigated chemical vapor etching of tungsten films using oxygen (O2) as the oxidant source and tungsten hexafluoride (WF6) as the etchant.
We propose that etching of tungsten proceeds in two steps: 1) oxidation of the tungsten film to form WOx surface species and 2) formation and removal of volatile metal fluoride species upon reaction with WF6. Using quartz crystal microbalance (QCM), we found that the oxidation step with O2 is required for etching to occur during WF6 exposure. In addition, etching of O2 treated tungsten films showed saturation towards WF6 exposure. This indicates that etching of tungsten using oxygen and WF6 is a self-limiting process, making it promising as an atomic layer etching process. QCM results also showed that the rate of etching depends on the temperature. Minimal amount of etching was measured at temperatures less than 275 °C. Ex-situ characterization techniques were applied to analyze the etching of tungsten films deposited on SiO2 substrates. Scanning electron microscopy (SEM) results revealed the change in morphology of tungsten films after different number of O2-WF6 ALE cycles. The tungsten film on SiO2 started out as a coalesced film, which transformed into disjointed nuclei, and the nuclei appeared completely removed as the number ALE cycle increased. Lastly, X-ray photoelectron spectroscopy (XPS) analyses further confirmed etching of tungsten film and showed a minimal amount of fluorine remained on the surface after the O2-WF6 ALE process.