From Microscopic Dynamics to Material Design in Colloidal Active Matter

Colloidal active matter is a new class of synthetic material composed of microparticles that continuously convert chemical energy into directed motion. These nonequilibrium systems can behave like microscopic engines, propelling themselves through fluid in ways reminiscent of bacteria and other swimming microorganisms. Unlike passive colloids, active particles generate persistent motion and interactions that give rise to new forms of transport, collective behavior, and self-assembly at the microscale.

In this talk, I will highlight two directions from our recent work. First, I will discuss how active colloids respond to chemical gradients, drawing parallels with chemotaxis and illustrating how these gradients can be utilized to steer their trajectories. Second, I will demonstrate how sedimentation serves as a simple yet powerful probe of the equation of state in active suspensions, enabling the deduction of their phase behavior and collective dynamics. These insights point toward harnessing active colloids for controlled self-assembly and for designing new strategies to manipulate transport in microfluidic and biologically relevant environments.

Together, these studies demonstrate how colloidal active matter represents both a model system for nonequilibrium statistical mechanics and a prototype for a new class of materials with tunable, dynamic properties.
 

Bio: Stewart Mallory is an assistant professor in the Departments of Chemistry and Chemical Engineering at The Pennsylvania State University. His research group develops nonequilibrium theories for soft and complex materials, with a focus on colloidal active matter and approaches to control matter and program its self-assembly at the microscale. A central goal of this work is to establish new principles for manipulating transport and designing functional materials far from equilibrium.

Prior to joining Penn State, he was an Arnold O. Beckman Postdoctoral Fellow and AGEP California Alliance Postdoctoral Scholar in the Division of Chemistry and Chemical Engineering at Caltech. He earned his Ph.D. in chemical physics at Columbia University as an NSF Graduate Research Fellow. He holds B.S. and B.A. degrees in chemistry and mathematics, magna cum laude, from the University of Hawai‘i.