ABSTRACT:
Strategies to mimic biology’s ability to generate complex, adaptive, hierarchical structures via emergent interactions are transforming materials science. Active colloids in nematic liquid crystals (NLCs) are exciting vehicles for such bio-inspired materials manipulation. Isotropic spherical colloids with rotational motion controlled by external magnetic fields swim effectively. The complex rheology of NLCs propels the colloids, generating translation from rotation. Hybrid colloids generate companion topological defects that form far-from-equilibrium topological flagella that power colloidal swimming. Non-equilibrium disclination lines serve as topological filaments that interact with nematic swimmers, providing reconfigurable sites for assembly in the domain. Swimming spheres trapped on these filaments act like molecular motors to reconfigure these structures. We are developing fundamental understanding of these transient, far-from-equilibrium interactions to exploit them as a new class of functional structures that generate new modalities of motion and interaction. Progress in understanding nematic colloid swimming, topological flagellar propulsion, swimmer-filament interactions, and in harnessing these effects to entrain, transport, release and deliver diverse colloidal building blocks is described.

SPEAKER BIO:
Kathleen J. Stebe is the Goodwin Professor in the School Engineering and Applied Sciences at the University of Pennsylvania. Educated at the City College of New York, she received a B.A. in Economics and a Ph.D. in Chemical Engineering at the Levich Institute advised by Charles Maldarelli. After a post-doctoral year in Compiegne, France under the guidance of Dominique Barthes-Biesel, she joined the Department of Chemical Engineering at Johns Hopkins University, where she became Professor and served as the department chair. Thereafter, she joined the University of Pennsylvania, where she has served in various administrative capacities including department chair and Deputy Dean. She has been recognized by the National Academy of Engineering, the American Academy of Arts and Sciences, the Johns Hopkins Society of Scholars, and as a Fellow of the American Physical Society and of the Radcliffe Institute. Kathleen is active in APS Division of Soft Matter Physics, and the ACS Division of Colloids and Surfaces, as well as the AIChE. Her research focuses on directed assembly in soft matter and at fluid interfaces, with an emphasis on confinement, geometry, and emergent structures in far from equilibrium settings for novel functional materials.