The 2019 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 2019 winners are:
|First Place (tie) – Vasudev Pralhad 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. This can be extended to CO production using CO2. A key challenge for these processes is the high temperature needed for thermal decomposition of the metal oxide (›1200 °C) . In addition, the need to balance the oxygen release and H2O/CO2 splitting properties of metal oxides often leads to low conversions. A hybrid solar-redox redox process for cogeneration of hydrogen/CO and liquid fuels using methane and solar energy operates at lower temperatures and higher H2O/CO2 conversions . In such a process, a reduced metal-oxide based redox catalyst is used to split water/CO2, producing concentrated hydrogen/CO. 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 . Further improvements in syngas yield and steam-to-hydrogen/CO2-to-CO conversion at reduced temperatures 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 (ΔEvacancy) 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 . Further, low temperature operation is possible using modified ceria, which allows for integration of the industrial waste heat. Efficient CO production is an attractive route to CO2-utilization and can boost sustainable downstream chemical production via carbonylation . ASPEN Plus® simulations indicate the potential to obtain higher efficiencies than the state-of-the-art hydrogen/CO 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/CO2 and syngas generation via a hybrid solar redox scheme.
|First Place (tie) – Christopher Straub
Background: The primary challenge of generating renewable fuels from plant based feedstocks is the ability of the microorganism to access the abundant carbohydrate content of the complex biomass. The other critical metrics, including low cost feedstock, high titer, high volumetric productivity, and low cost separations have largely been demonstrated economically at industrial scale, at least for ethanol. Even with thermal, chemical, and enzymatic treatments that can account for more than 25% of the process costs, carbohydrate conversion to product has remained at around only 50%.Results: This barrier has been overcome by pairing a transgenic line of poplar trees1 to a natural lignocellulose degrading extreme thermophile, Caldicellulosiruptor bescii (Topt = 78°C). The transgenic poplar trees have been engineered to not only contain lower lignin content but modifications to lignin structure and monomer ratio. With untreated poplar trees as the sole carbon source, C. bescii was able to improve carbohydrate conversion from 15% with the wild type poplar to 80% with the transgenic poplar lines. In addition to high conversion of these transgenic plants, C. bescii must be engineered to produce a valuable fermentation metabolite. Its native products, acetate and lactate, are of low value and difficult to separate from water. C. bescii has been previously engineered to produce ethanol at 60-65°C, a growth range which severely inhibits its biomass degrading capabilities.2 Here we develop a pathway to produce acetone3 at 70°C and an ethanol pathway with more thermally stable enzymes to allow ethanol production at 70°C. We further demonstrate a method to separate acetone (Tb = 56°C) and ethanol (Tb = 78°C) in situ during active fermentation via distillation at 70°C under moderate vacuum.
Conclusions: The ability to of a microorganism, C. bescii, to convert untreated lignocellulosic biomass to industrially useful biofuels and chemicals has been demonstrated at high conversion. Ongoing improvements in titer and product selectivity are pushing this promising technology toward viability on a commercial scale.
|Third Place – Amulya Pervaje
Background: Developing structure-property relationships is critical for the design of polymeric materials with properties optimized for relevant applications. We have developed molecular models for polymeric systems with the ability to predict several important properties. Our models are able to: (i) predict the glass transition of polymers based on monomer composition, (ii) model the kinetics and thermomechanical properties of specific thermosetting systems, and (iii) estimate the mechanical properties of polymer fibers. Predicting the glass transition temperature (Tg) is relevant for polymer processing, as material properties change dramatically from rigid and glassy below Tg to flexible and rubbery above Tg. The Tg value can be difficult to predict for polymers comprising of number of different monomers. We predict Tg using molecular dynamics simulations with a coarse-graining method that requires minimal thermodynamic data of the monomers . For thermosets, which are chemically cured, cross-linked materials, we model the kinetics of curing and thermomechanical properties based on formulation and reaction conditions using a modified molecular dynamics method. We also predict the mechanical properties of polymer fibers based on their underlying chemical and physical structure.Results: Our coarse-grained molecular dynamics simulations of polyester polyols resulted in good agreement for the density, Tg and specific heat capacity change across Tg as compared with experimental values . Further simulations using a design of experiments (DoE) approach resulted in a correlation for Tg based on monomer identities and polymer chemical compositions  that will be useful in designing new polyester polyols. In modeling thermosetting systems, we used similar coarse-grained simulations, including models for an isocyanate trifunctional crosslinker, and a solvent. Using experimental data of reaction kinetics characterized by FTIR, we created a kinetic model quantifying the effect of primary and secondary hydroxyl groups in polyols on the rate of the curing reaction with temperature. This kinetic model was incorporated into molecular dynamics simulations of the cross-linking process through the derivation of a factor that transforms the simulation times to times in the experimental curing range. Additionally, we modeled structure and Tg development during and after curing and probe thermomechanical property trends. When studying polymer fibers, we incorporated key physical and chemical structure factors in our model: (i) polymer chemistry, (ii) molecular weight distribution, (iii) crystallinity, and (iv) orientation. We used united atom models to model their mechanical properties and develop constitutive models for use in continuum-level models.
Conclusions: Our computational modeling of polymer glass transition, thermosets, and fibers led to the development of predictive correlations, insights into kinetics and modeling of thermophysical properties of complex polymeric systems.
|First Place – Jiaqi Yan
Background: Most polymer pairs tend to be inherently immiscible and macrophase-separate due to their low entropy of mixing and endothermic mixing, thereby resulting in poor interfacial adhesion and thus limiting the use of such materials in engineered systems [1-3]. The large domains of phase separation provide relatively little interfacial area, leading to poor entanglements between polymer chains. In often cases, the domain reduction is achieved through emulsification, this is the very same concept underlying the development of oil/water emulsions commonly encountered in food products. At its core, compatibilization is often required to improve the adhesion of highly incompatible commercial polymer pairs in blends. Hence, the mechanical properties and fracture resistance will be enhanced . A more common methodology is to generate compatibilized polymer blends composed of two or more homopolymers with a block copolymer to yield desirable property combinations.
Results: The modified SIS has been successfully synthesized by grafting the ester group on parent SIS using thiol-ene click chemistry. The thermal properties were investigated by DSC studies, modified SIS dramatically decreased the glass transition temperatures due to a better compatibility between polymers. The similarity of pendant ester group of esterified SIS (eSIS) with poly(lactic acid) significantly increased the compatibility between PLA and eSIS blends. The successful compatibilization was evidenced by a measured improvement in reduction of size scale of phase separation domains between compatibilized neat PLA and eSIS. It was also evidenced by the enhanced mechanical properties. With 1 wt% incorporation of eSIS, toughness and modulus was increased to 62 MJ/m3 (~16 times than that of neat PLA) and 380 MPa, respectively. It was also found that 1 wt% of eSIS was the optimum amount addition, since higher content was not necessarily beneficial for the rubber toughening effect.
Conclusions:The study provides a novel, simple, and effective method to synthesize and incorporate thermoplastic elastomers into poly(lactic acid) for the purposes of compatibilization and rubber toughening, with significant toughness improvement over previously reported toughened materials.
|Second Place – Sabina Islam
Background: “Coffee rings” have captured the attention of scientists for several decades, as they represent a beautiful example of colloidal self-assembly. A multitude of liquids, surfactants, and chemical modifiers have been pursued in order to guide the patterns of such coffee ring assembly. Even whiskey is not outside the realm of study; previous work has shown that uniform films are deposited in drying droplets from whiskey and correlate to its inherent chemical properties1. This poster introduces an interesting self-assembly mechanism that occurs when a drop of bourbon whiskey is evaporated on a hydrophobic surface. Evaporation of a dilute drop of bourbon at a particular range of proofs leaves a unique web formation where each web pattern is unique to a specific brand of bourbon. The fundamental mechanism of self-assembly of these bourbon webs were investigated here. Despite being so popular, to date, there is no quantitative study on whiskey colloids. Using dynamic light scattering technique, fundamental investigation on colloid occurrence as a function of (i) aging, (ii) proof, and (iii) temperature was also performed in this study.
Results: Commercial whiskey is available at alcohol-by-volumes of 40% or greater and do not inherently contain a large concentration of colloids as its components are mostly solubilized. However, we demonstrated that sub-micrometer colloidal micelles form when whiskey is diluted with water or the temperature is lowered. These colloids are electrostatically stabilized, and the particle size remained stable at low alcohol concentrations. Additionally, these whiskey colloids increased in concentration with higher barrel aging. During droplet evaporation, as alcohol evaporates at a rate much faster than water, these water-insoluble colloidal species precipitated. This results in a dynamic and complex evaporation process whose initial conditions govern the resultant pattern of assembled colloids. At low alcohol content (< 15% ABV) the pattern resembled a coffee ring and at high alcohol content (> 35% ABV) the colloids formed a thin film. However, at intermediate proofs rich variety of web-like microstructures formed. Moreover, we found that, only bourbon whiskeys formed these highly visual patterns (sample size of ten brands) whereas others did not (one Cognac, one Irish whisky, one Scotch, and one Canadian whiskey tested).
Conclusions: The web-like patterns were qualitatively different between commercial brands. Various aged samples (12 months to 71 months) were acquired from a local distillery and, for this brand, the web’s density increased with age; webs did not form with unaged whiskey (a.k.a. “white dog”). This facile technique could be used for maturation analysis or counterfeit detection based on a new class of evaporation-deposition phenomena. Additionally, the colloidal findings of this study will impact industrial filtration and tasting practices of bourbon whiskeys.
H. Kim, et al. PRL 116, 124501, 2016.
|Third Place – Javier Huayta
Background: Several environmental factors affect longevity in C. elegans, and most of these stressors function through the DAF-16/FOXO transcription factor, which regulates expression of genes involved in aging and stress response. In turn, spatiotemporal activity of these genes alters lifespan and healthspan of C. elegans . Tracking longitudinal activity of these aging-related genes is challenging due to the destructive nature of most quantitative gene expression assays. Moreover, microfluidic platforms allow for easy animal handling and immobilization without need of anesthetics and time-consuming manual manipulation . By this means, longitudinal in vivo tracking of gene activity in response to environmental perturbations can be achieved through quantitative analysis of gene expression by fluorescence imaging. The data sets thus acquired can be used to relate environmental perturbations, longitudinal gene activity, and healthspan and lifespan. Quantitative mathematical models derived with these data will enable elucidating how this lifelong background determines lifespan and healthspan in C. elegans.
Results: We developed a microfluidics platform for lifespan and healthspan characterization for age-synchronized C. elegans populations. This device was fabricated through standard PDMS molding, and designed with chambers and adjacent channels for feeding, immobilization, and imaging. We applied differential pressure to the chamber containing C. elegans, with a fluorescent-tagged gene, to force the animals into the imaging channels. After imaging was completed, the animals were taken back to their original chamber by applying pressure in the opposing direction. A synchronized MAH97 C. elegans population expressing GFP-tagged DAF-16 under dietary restriction exhibited an increased migration of DAF-16 to the nuclei of the cells with an increasing trend from the time 0 hours until 6 hours. In repeated experiments, this trend was observed at days 3, 6, and 9; but with a maximum nuclear to cytoplasmic DAF-16 ratio after 6 hours showing a decreasing trend.
Conclusions: The microfluidic platform enables the immobilization and imaging of C. elegans under controlled environmental stimuli. These stimuli affect the localization of DAF-16 in a spatiotemporal basis that can be measured through our MATLAB algorithm. In further studies, we will explore the effects of other lifespan-altering environmental conditions, and additional key aging pathways affecting C. elegans.
Dr. David Sehgal (Ph.D., 2002) delivered the Keynote talk, “Experience is What You Get the Day After You Needed It – My Time in Industry.” Dr. Sehgal is Vice President of FujiFilm Diosynth Biotechnologies.
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 2019 award winners are Sahand Bosari, Fellow, and Ryan Dudek, the second-place awardee.
The Fall 2019 Praxair Exceptional Teaching Assistant Award was presented to Ria Corder. Amelia Chen is the Spring 2018 Praxair Award winner. 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 27, 2020.