Quantifying instability patterns and rheological properites of active nematode suspensions 

We look at suspensions of Turbatrix aceti nematodes as a model active matter system. This active matter system exhibits rheological properties influence by the collective swimming motion of the nematodes. Prior studies have addressed phenomena like synchronized motion and time-dependent viscosity under low shear rates for these active fluids. Our studies aim to build upon the current understanding of such an active fluid by examining these rheological as well as exploring pattern formations in Hele-Shaw lifting flows. We achieve this using a rheo-optical setup to probe non-linear flow dynamics and pattern formation in nematode suspensions. We quantify and compare the resulting viscous fingering instabilities in active versus passive control samples by tracking the evolving fluid interface perimeter. We report that the pattern formations and instability growth rates are more pronounced in the active suspension compared to the passive control. Notably, the observed rheological behavior and pattern formation are affected by nematode concentration. These findings suggest new avenues for understanding active matter and collective motion under external forces.