Fall 2025 ChBE Seminar: Schroeder

Vesicles are membrane-bound compartments that play a central role in biology. Despite recent progress, the dynamics of single- and multi-component lipid vesicles are not fully understood, particularly far from equilibrium where complex nonspherical shapes undergo large deformations in flow. In this talk, I will present recent work from our group on the non-equilibrium dynamics of lipid vesicles in precisely defined flows using the Stokes trap – a new method that enables full 3D control of position and orientation of molecules or particles using active feedback control, without the need for external optical, magnetic, or electric fields. After characterizing equilibrium properties including bending modulus and membrane tension, we study vesicle deformation as a function of dimensionless flow strength (capillary number, Ca) and vesicle deflation (reduced volume). Our results show that vesicles are remarkably deformable, exhibiting reversible shape changes with aspect ratios exceeding 20 in repeated stretch-relax cycles in the bending-dominated regime. Single-component vesicles show a rich variety of shapes and conformations, including asymmetric and symmetric dumbbells, in addition to pearling, wrinkling, and buckling instabilities, depending on membrane properties. Based on these observations, we construct a detailed flow-phase diagram for vesicles in extensional flow, and we further analyze transient stretching and relaxation dynamics. Two distinct relaxation processes emerge for deformed vesicles, including a fast relaxation process corresponding to bending modes and a slow process governed by membrane tension relaxation. Finally, we study vesicle shape dynamics in time-dependent large-amplitude oscillatory flows, revealing three distinct dynamical regimes – pulsating, reorienting, and symmetrical deformations – arising from the competition between flow and membrane deformation timescales. Together, these results provide new insight into flow-driven shape instabilities for lipid vesicles using new methods in flow automation.

Charles Schroeder is a Professor of Chemical and Biological Engineering at Princeton University and Associated Faculty in Princeton Materials Institute. Dr. Schroeder received his B.S. in Chemical Engineering from Carnegie Mellon University, followed by an M.S. and Ph.D. in Chemical Engineering from Stanford University under the supervision of Professor Eric Shaqfeh and Professor Steven Chu. Dr. Schroeder was an NIH K99/R00 Postdoctoral Fellow and Jane Coffin Childs Postdoctoral Fellow in the Department of Chemistry and Chemical Biology at Harvard University. Prior to moving to Princeton in 2025, he was the James Economy Professor of Materials Science and Engineering and Professor of Chemical and Biomolecular Engineering at the University of Illinois at Urbana-Champaign, where he led the AI for Materials (AIM) Group in the Beckman Institute for Advanced Science and Technology. Dr. Schroeder has been recognized by several awards, including a Packard Fellowship for Science and Engineering, a Camille Dreyfus Teacher-Scholar Award, an NSF CAREER Award, the Arthur B. Metzner Award from the Society of Rheology, the Dean’s Award for Excellence in Research at Illinois, and an NIH Pathway to Independence Award (K99/R00). Dr. Schroeder is a Fellow of the American Association for the Advancement of Science (AAAS), the Society of Rheology (SOR), and the American Physical Society (APS).