The 2018 Schoenborn Graduate Research Symposium was an outstanding success!
The Symposium is divided into two sections. During the first section, senior-level PhD candidates make formal presentations about their research and the associated results. During the second section, mid-level PhD students make informal poster presentations about their research. Faculty judges select first-, second-, and third-place winners of the formal presentations and graduate student voters select the poster presentation winners.
The 2018 winners are:
|First Place – 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.
|Second Place – Koohee Han
Background: I will demonstrate how magnetically responsive patchy microcubes can be assembled into self-reconfiguring microclusters and employed as microbots and microswimmers . 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 . 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.
|Third Place – 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  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 , 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 . 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 .
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.
|First Place – 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 . 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 . 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 . 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 330C and 250C 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 450C, 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.
|Second Place – 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.
|Third Place – 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 . 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 .
Dr. Arthi Jayaraman (Ph.D., 2006) delivered the Keynote talk, “Using Molecular Simulations and Theory to Design Macromolecular Soft Materials.” Dr. Jayaraman is an Associate Professor in the Departments of Chemical and Biomolecular Engineering and Materials Science and Engineering at the University of Delaware.
The Vivian T. Stannett Fellow Award is also presented at the Symposium. It’s named in memory of Professor Vivian T. Stannett, a CBE faculty member who was an internationally renowned polymer scientist, research leader, and member of the National Academy of Engineering. The Award recognizes research excellence, initiative, focus and tenacity during the early careers of Ph.D. candidates in the department. The 2018 award winners are Dennis Lee, Fellow, and Vasudev Haribal, the second-place awardee.
The Fall 2018 Praxair Exceptional Teaching Assistant Award was presented to Jenna Meanor. The Award recognizes instructional effectiveness and management skills of Ph.D. candidates who serve as exemplary teaching assistants in CHE courses. The Award recipient goes above and beyond the call of duty and provides students with tireless and selfless attention to high-quality instruction and professionalism.
Congratulations to the Schoenborn competition, Stannett and Praxair award winners and their advisers. Well done to all!
Be sure to mark your calendar for next year’s Symposium on January 21, 2019.