Seminar - SCM

Microorganisms swimming through viscous fluids imprint their propulsion mechanisms in the flow fields they generate. Extreme confinement of these swimmers between rigid boundaries often arises in natural and technological contexts, yet measurements of their mechanics in this regime are absent. In this talk, I will show that strongly confining the microalga Chlamydomonas between two parallel plates not only inhibits its motility through contact friction with the walls but also leads, for purely mechanical reasons, to inversion of the surrounding vortex flows. Insights from the experiment lead to a simplified theoretical description of flow fields based on a quasi-2D Brinkman approximation to the Stokes equation rather than the usual method of images. This vortex flow inversion also provides the advantage of enhanced fluid mixing despite higher friction. Overall, our results offer a comprehensive framework for analyzing the collective flows of strongly confined microswimmers. In addition, I will briefly discuss my postdoctoral work on the spatiotemporal control of microtubule-based active fluids through cell-free gene expression. Here, I will show preliminary results of driving a passive microtubule sheet out of equilibrium into an active state through spatially controlled propagation of bending instabilities. Finally, I will outline prospective research directions that I intend to pursue at RRI.