"Driving Superparamagnetic Colloids Out of Equilibrium with TimeVarying Magnetic Fields"

This event is sponsored by FAMU-FSU Engineering Department of Chemical & Biomedical Engineering.

Abstract: Colloidal suspensions driven out of equilibrium exhibit rich and unexpected behaviors, from dynamic clustering to self-organized phase coexistence. These nonequilibrium systems challenge conventional thermodynamic intuition, yet their dynamics often resemble equilibrium phase transitions such as crystallization, condensation, and phase separation. By leveraging time-varying magnetic fields, we explore new avenues for controlling soft matter systems and uncover emergent material properties.

I will first introduce a magnetically tunable colloidal model for semiflexible filaments, composed of DNA-linked paramagnetic beads. These engineered chains exhibit persistence lengths spanning five orders of magnitude, allowing us to probe the intricate balance between external forces, viscous dissipation, and filament elasticity. In dynamic magnetic fields, these filaments undergo buckling, coiling, and other emergent motions that provide design principles for microbots and rheological probes.

In a second example, we examine the collective behavior of superparamagnetic colloids under rotating magnetic fields. These driven particles self-organize into a steady-state vapor-liquid coexistence, reminiscent of equilibrium phase transitions. Using Kelvin’s equation, we extract an “effective vapor pressure” for this nonequilibrium system, offering a new statistical mechanics framework to describe active matter.

Dr. Lisa Biswal
William M. McCardell
Professor and Chair Department of Chemical and Biomolecular Engineering
Rice University

Speaker Bio: Dr. Lisa Biswal is the William M. McCardell Professor and Chair of the Department of Chemical and Biomolecular Engineering at Rice University in Houston, Texas. She has a B.S in chemical engineering from Caltech and a Ph.D. in chemical engineering from Stanford University. She leads the Soft Matter Engineering Laboratory, where she focuses on establishing connections between the rheological behaviour of particulate and multiphase systems and the underlying physics governing colloidal assemblies, surfactant stabilization related to foams and emulsions, and the development of polymer composites for batteries. Her research aims to uncover new insights and ideas that can be used to engineer innovative solutions for a diverse range of technological challenges in the fields of materials and energy. She has been elected Fellow of the American Physical Society (APS) and the American Institute of Chemical Engineers (AICHE). She has received the Provost’s Award for Outstanding Doctoral Mentor and the George R. Brown superior teaching award.