Physics Colloquium - "Electrifying active matter" Presented by Professor Petia Vlahovska - Northwestern University

Bird flocks and fish schools move around like fluid when viewed on a scale much larger than the individuals. Similar large-scale coherent motions have been observed with self-propelled micro-particles such as bacteria and motile colloids. In this talk, I will discuss the collective dynamics of particles activated by electric fields, e.g., the Quincke instability (spontaneous spinning of a dielectric particle in an applied uniform DC field) which makes the particles roll on a surface.  I will present our experiments showing how Quincke rollers can be designed to perform Run-and-Tumble-like locomotion mimicking bacteria such as E. coli. Populations of these Quincke random walkers self-organize and exhibit behaviors reminiscent of bacterial suspensions such as dynamic clustering and mesoscale turbulent-like flows, and new behaviors such as emergent multi-vortex states. When enclosed in a drop, the Quincke rollers drive strong shape fluctuations and drop motility resembling amoeba crawling. Finally, I will show how electrohydrodynamic flows can drive droplets to tandem-swim. Petia M. Vlahovska received a PhD in chemical engineering from Yale University (2003) and MS in chemistry from Sofia University, Bulgaria (1994). After a post-doc in the Membrane Biophysics Lab at the Max Planck Institute of Colloids and Interfaces (2005) and ten years on the faculty at Dartmouth College and Brown University, she joined the faculty at Northwestern University in 2017. Her research interests are in fluid dynamics, membrane biophysics, and soft matter. Dr. Vlahovska is a 2019 American Physical Society Fellow, and a recipient of the National Science Foundation CAREER Award, David Crighton Fellowship, and a Research Fellowship from the Alexander von Humboldt Foundation (Germany).