Engineering reconfigurable flow patterns via surface-driven light-controlled active matter

Authors: Xingting Gong, Arnold Mathijssen, Zev Bryant, Manu Prakash

Link: Phys. Rev. Fluids 6, 123104 - 30 Dec 2021

DOI: https://doi.org/10.1103/PhysRevFluids.6.123104

Abstract: Surface-driven flows are ubiquitous in nature, from subcellular cytoplasmic streaming to organ-scale ciliary arrays. Here we model how confined geometries can be used to engineer complex hydrodynamic patterns driven by activity prescribed solely on the boundary. Specifically, we simulate light-controlled surface-driven active matter, probing the emergent properties of a suspension of active colloids that can bind and unbind from surfaces of a closed microchamber, together creating an active carpet. The attached colloids generate large-scale flows that in turn can advect detached particles toward the walls. Switching the particle velocities with light, we program the active suspension and demonstrate a rich design space of flow patterns characterized by topological defects. We derive the possible mode structures and use this theory to optimize different microfluidic functions including hydrodynamic compartmentalization and chaotic mixing. Our results pave the way toward designing and controlling surface-driven active fluids.