Research Interest
Our work is primarily in the field of “Active Matter” which is an exciting interdisciplinary research area at the intersection of chemistry, soft matter physics, and material science.
The goal is to understand the remarkable behavior of microscopic systems whose constituents convert internal or environmental energy to undergo directed motion or self-propulsion.
From the swarming of bacterial suspensions to the ATP-driven processes that guide the spatial localization of cellular organelles, active matter systems exhibit a range of incredibly complex and choreographed behaviors. Interestingly, there exists a vast experimental library of highly-engineered biological and synthetic microswimmers now exist, which are broadly referred to as active particles. A few representative examples and their unique behavior are highlighted below.
Examples of biological and synthetic active matter. Volvox algae are capable of generating complex hydrodynamic flow fields. Microtubules and light-activatable motor proteins that self-organize upon illumination. Xenobots are synthetic organisms constructed from frog embryo stem cells that can be programmed to perform a desired microscopic task. Platinum-coated Janus swimmers can self-propel in a dilute hydrogen peroxide solution to power microscopic machines.
An active particle’s ability to autonomously navigate complex microfluidic environments suggests many useful applications, including targeted drug delivery, the clean-up and neutralization of environmental pollutants, and the self-assembly of microscopic structures. Due to their unique self-driven nature, and ability to sense at a scale comparable to their size, active particles are potentially the ideal tool to manipulate matter at the colloidal scale.
To design the next generation of soft functional materials and tunable complex liquids, we need a theoretical and computational framework capable of systematically quantifying the individual and collective dynamics of synthetic and biological active matter systems.
Our mission is to understand the interplay between active, thermal, hydrodynamic, and dispersive forces that drive collective behavior. By generalizing concepts in classical statistical mechanics and liquid state theory to active systems, we can reach the stage where reliable, robust predictions useful for material or biological engineering are possible.
The theoretical tools we develop will be used in concert with computer simulation to systematically characterize the phase behavior and critical phenomena of complex active colloidal systems, especially related to the self-assembly of new colloidal materials.
Current Projects
-
Self-propulsion mechanisms and their role in tuning the behavior of active suspensions
By leveraging numerical techniques that consider both the colloidal particle and the surrounding fluid, this project provides insight into the validity of minimal models to describe active systems. In addition, an understanding of the propulsion mechanism offers a new handle for tuning the behavior of active suspensions to possess a desired set of mechanical properties. Additionally, as most cellular machinery operates on the colloidal scale, these results will help understand critical biological processes that rely on similar physical mechanisms.
-
Rare events in soft active matter
An important class of problems that, for the most part, have been neglected in active microscopic systems is the study and characterization of rare events. Rare events are a ubiquitous feature of complex stochastic systems. As we have learned from stock market crashes to earthquakes, these infrequent events often have a drastic effect on the system in which they take place. This project focuses on developing theoretical methods to calculate the transition rate constants for a range of technologically and biologically relevant rare events in active systems. Such studies are crucial for a deeper understanding of the generalized free energy landscape of active systems. A theoretical framework for computing rare events would be the first step in developing a computational toolkit for active matter systems that rivals that used to study equilibrium systems.
-
From photonic crystals to stealth materials: data-driven approaches to colloidal self-assembly
Colloidal self-assembly is a robust approach for the design of the next generation of smart, functional materials. This autonomous construction process leverages fluctuations from the environment to generate microstructures at practically no external cost. Many self-assembled materials are prized for their proposed applications in photonics, catalysis, and novel structural properties. It would be highly beneficial to devise a suite of techniques that select for the exclusive formation of the desired structure. This project aims to leverage the unique nonequilibrium conditions generated by active systems to find alternative and more efficient self-assembly pathways for colloidal materials. The ultimate goal is a complete and detailed mechanistic understanding of the self-assembly pathway, such that conditions can be dynamically modulated to maximize the yield of different technologically relevant materials.