(2en) Non-Equilibrium Dissipation As an Organizing Principle in Driven Soft Materials: From Polymers to Active Drops

I aim to assemble and mentor a research group that solves fundamental problems at the intersection of soft condensed matter physics, rheology, and stochastic thermodynamics. Specifically, my group would undertake theoretical and computational research on dissipation quantification in soft condensed matter driven away from equilibrium. Characterizing the various sources of friction at the molecular level would help predict the folding pathway adopted by protein molecules. Understanding the connection between energy dissipation at the microscale and the dynamic response of materials at the macroscale is crucial for understanding how processing conditions could affect the performance and properties of soft materials. Over the course of my PhD, I developed code to simulate coarse-grained polymer models subjected to nonequilibrium driving and estimate dissipation at the single-molecule level. In my postdoctoral research, I customize open-source software to investigate the dynamics of self-propelled, or active, droplets. My research group will build theoretical and computational tools that uncover how energy dissipation at the microscale connects to the dynamic response of the materials at the macroscale. The resulting insights will be used for the design of polymeric material with novel dissipative properties and fine-tune the motility of active matter swarms for therapeutic and environmental remediation applications.

Research Interests:

Soft matter systems like polymer solutions and colloidal suspensions routinely undergo flow processes that drive them out equilibrium during industrial processing. During these processes, the polymer chains undergo configurational changes, overcoming the effects of external friction from the solvent molecules and internal friction arising from intramolecular interactions. Self-propelled colloidal particles are inherently out-of-equilibrium as they harness chemical energy from their environment to overcome dissipation from the surrounding fluid.

I have identified the following three areas for my group to work on during the first few years of my independent career:

1. Quantifying the dissipative effects of internal friction in polymers: Protein molecules such as hormones and antibodies are commonly subjected to a variety of flow profiles during bioprocessing, and the internal friction of these molecules dictate the energy dissipated in these operations. Ciliary and flagellar oscillations in micro-organisms are driven by the hydrolysis of ATP molecules, and the contribution from internal friction in these far-from-equilibrium processes outweighs hydrodynamic drag by nearly an order of magnitude. My group will develop analytical theory and perform Brownian dynamics simulations to quantify the dissipation incurred in polymer chains with internal friction driven between equilibrium and nonequilibrium steady states. A fundamental understanding of the energy dissipation due to internal friction in these driven processes could unveil significant insights into the dynamic response of single polymer chains to various types of mechanical forcing.

2. Identifying rheological signatures of molecular-level dissipation: The high-frequency response of polymer molecules to an applied strain holds industrial and biological relevance: e.g., the performance of inkjet printing fluids is crucially governed by its linear viscoelastic properties in the high frequency regime, while benign and malign cancer cells can be distinguished based on differences in their shear moduli at high frequencies.

Internal friction affects not only the conformational kinetics of the polymer at the single-molecule level, but also modulates the short-time-scale rheological response of a solution of polymeric chains, manifesting as a plateau in the dynamic viscosity at high frequencies of the applied strain. I recently developed a numerical algorithm for the simulation of an isolated polymer chain with internal friction in an unbounded fluid. My group will work to develop an open-source HOOMD-based computational tool for the simulation of a solution of such chains at finite concentrations that leverages an O(N) algorithm for the modeling of hydrodynamic interactions. The software package would then be used to characterize the linear viscoelastic and rheological response of polymer solutions at finite concentrations.

The development of a robust computational model for the dynamics of polymeric solutions at large frequencies would therefore enable high-throughput predictions for use in practical applications.

3. Optimal swimming strategies for active colloid suspensions: Active entities could either harness chemical energy from their surroundings or be manipulated by an external magnetic or electric field to navigate the environment around them. Examples of their usage for therapeutic purposes include targeted drug delivery into cancerous tumors, removal of plaques from blood vessels and in vitro fertilization. Swarms of self-propelled particles have been used for environmental remediation activities such as removal of heavy metal contaminants, oil, and microplastics from water. It is important to precisely control the dynamics of these particles, lest they should become sources of pollution themselves.

Tuning the dissipation associated with the motion of these particles could help tailor the material properties and emergent dynamics of a collection of such entities. My group will use continuum theories describing the collective dynamics of active particles to derive the dissipation associated with their motion. These results will be validated against coarse-grained simulations to devise optimal swimming strategies for various self-propulsion protocols.

Teaching Interests:

I have been taught by world-class faculty throughout my academic training, and I view teaching as a way of paying forward the good fortune I have received. Over the course of my academic training, I have lived and worked in India, Australia, and the USA. Through my stints as a teaching assistant for a physical chemistry course in IIT Bombay (India), and the transport phenomena and numerical methods course in Monash University (Australia), I gained valuable perspectives about pedagogical techniques to be adopted while interacting with students from diverse backgrounds. Given my multidisciplinary training in physical chemistry and chemical engineering, I am open to any teaching commitment at the undergraduate level, and particularly interested in teaching thermodynamics, heat and mass transfer, engineering mathematics and numerical methods to undergraduates. At the graduate level, I am keen on delivering a course on statistical mechanics, as well as designing electives on polymer kinetic theory and an introduction to active matter.