Pattern formation in active soft matter systems observed with rheo-optical microscopy

We investigate the rheological properties and pattern formation of a model active matter system consisting of living nematodes. Using a rheometer with an optical microscopy attachment, we study the viscous-fingering-like instabilities that form during lifting Hele-Shaw experiments. We find that the instabilities depend strongly on the concentration of nematodes and their activity. These and related experiments allow us to characterize how activity and external forces effect the rheological properties and fluid instabilities of active matter. We also review other rheo-optical experiments conducted in our lab on a variety of soft matter systems, using both our bulk rheometer with a microscopy attachment and an optical-tweezers-based microrheology setup.