2023 AIChE Annual Meeting

(2fb) Engineering Hierarchical Materials for Structural Composites and Advanced Textiles

Research Interests:

Many inherent functionalities of natural materials arise from their hierarchical structures. Bamboo is made of aligned fibers in a matrix to provide structural integrity, nacreous mollusk shells have interlocked platelets to provide toughness, and wool possesses a fractal structure that provides thermal insulation. A hierarchical material uses self-assembly at the atomic, molecular, or macromolecular scale to create higher order building blocks that organize into increasingly complex materials. Each length scale of organization imparts unique physical, chemical, and mechanical properties that collectively influence bulk material functionality. My research aims to understand the dependencies between molecular, mesoscale, and macroscale properties in hierarchical polymeric materials. We will then leverage these findings to engineer materials with desired characteristics, such as lightweight, polymer composites with exceptional strength, soft textiles that respond to stimuli, and structural materials with a low environmental footprint. This interdisciplinary research will bridge engineering, chemistry, material science, and physics to develop both fundamental and applied advancements in high performance materials. In particular, my research program will focus on three areas:

1) Understanding microscopic and macroscopic polymer/fiber interactions for high-performance, fully recyclable fiber-reinforced composites.

2) Engineering advanced textiles with reduced CO2 footprint, robotic actuation, and sensing capabilities.

3) Developing processing-structure-property relationships of dynamic polymers and polymer nanocomposites for advanced manufacturing.

Previous Research Experience:

My research as a Princeton Center for Complex Materials postdoctoral fellow (Advisors: Prof. Richard Register and Prof. Rodney Priestley, Princeton University) has explored how macromolecular structure influences solution phase behavior and bulk thermal properties. I synthesized styrene/isoprene copolymers by anionic polymerization with similar molecular weight and overall composition but small changes in monomer sequence by placing small homopolymer blocks (5-10 kg/mol) of polyisoprene (PI) or polystyrene (PS) at the end or in the middle of a styrene-isoprene random copolymer chain. I found that in selective solvents, careful selection of block size and block placement could result in microphase separation prior to macrophase separation. This results in a decrease in solution critical temperature. Conversely, if one or both chain ends are enriched in a solvophobic block and microphase separation is avoided, the critical temperature increases. These insights can be used to engineer new thermoresponsive systems that have improved control over micro- and macrophase separation for development of new smart materials for enhanced drug delivery or water purification.

I am currently exploring how changes in sequence affect chain dynamics near the glass transition temperature (Tg). Polymers with a PS or PI homopolymer block at the end of the chain show a small (~2 K) decrease in Tg compared to random copolymers of the same composition. I explored this counterintuitive result through cooperative movement and self-concentration dynamics between rubbery and glassy domains. The presence of a rubbery block decreases the length of cooperative movement whereas the presence of a glassy block does not significantly impact bulk dynamics. Instead, the random segment dominants Tg behavior. This work constitutes a significant progress towards control and modification of chain dynamics for better engineering of polymeric materials.

During my PhD at Rice University (Advisor: Prof. Matteo Pasquali), I studied processing-structure-property relationships of carbon nanotube (CNT) fibers and application of CNT fibers for wearable electrocardiogram (EKG) electrodes. I systematically studied how CNT purity, solution rheology, coagulation, and spinneret design influence the microstructure of solution spun CNT fibers and the ultimate fiber properties. Through these insights, I significantly improved key CNT fiber properties such as electrical conductivity and tensile strength. I also developed a method to sew CNT threads into textiles with a standard sewing machine. I used this method to make textile-based EKG electrodes that obtained signals comparable to traditional wet electrodes without the need for conductive gel or adhesive. I also demonstrated the same CNT threads could be used as transmission wires to carry the EKG signals to Bluetooth-enabled transmitters. This work represented a major step forward in wearable electronics as the CNT thread material showed a unique combination of flexibility, washability, performance, and ease of integration into existing fabrication methods.

Teaching Interests:

Both my bachelor’s degree and PhD are in Chemical Engineering, and I am excited to teach core undergraduate and graduate classes such as transport phenomena, fluid dynamics, reactor design, and separation processes. I am particularly interested in teaching the introductory chemical engineering course. As students enter the chemical engineering curriculum for the first time, they can feel anxious due to their academic background or identity. Diversity, equity, and inclusion are extremely important to me, and I strive to create a classroom where everyone feels welcome and has the tools to succeed. To achieve this goal, I plan to structure courses to have low-stakes homework assignments and quizzes before exams to address knowledge gaps early in the curriculum. I intend to offer a variety of office hour formats such as structured in-person, virtual help sessions, and informal lunch discussions to accommodate diverse schedules and varying learning styles. Finally, I will show diverse representation in my lectures; I will include relevant recent work by diverse scientists to complement traditional chemical engineering concepts.

In addition to teaching core courses, I am interested in developing an undergraduate or graduate level course on materials characterization. At the undergraduate level, the course would center around the question of “how do we select materials for engineering applications?” Students would learn how spectroscopy, microscopy, thermal analysis, and mechanical testing can answer important questions about the surface structure, internal structure, and bulk properties of materials. Small groups of students would work together to use a few of these instruments to explore structure-property relationships of materials they use every day. They would then explore these materials in terms of cost and environmental impact. At the graduate level, the course would delve deeper into instrumentation and emerging trends in materials characterization. The course would emphasize areas of interest of students by taking a survey at the start of the semester. I would also be interested in teaching additional elective courses on topics such as carbon nanomaterials and current topics in polymer physics.