Event

Biological systems are composed of soft deformable components that are mechanically actuated by active agents such as molecular motors that locally consume free energy to generate motion. Beyond their vital role in biology, interactions between soft and active materials raise a number of fundamental questions on the manner in which nonequilibrium forcing couples to the system of interest in order to maintain desired steady states. In this talk, I will discuss these questions in the specific context of colloidal suspensions, which form an important class of soft materials. I will first show how colloidal suspensions can exhibit various phases such as crystals and glasses at high densities in the absence of external drives. I will also illustrate how the ability to visualize the motion of individual colloids using light microscopy enables us to address broader questions in condensed matter physics associated with atomic and molecular solids and liquids. I will then show how dilute colloidal suspensions that exhibit no tendency towards ordering under thermal noise spontaneously form dynamic clusters when immersed in dense suspensions of motile bacteria. This clustering is caused by nonequilibrium effective attractions between colloids induced by collisions with bacteria, that are reminiscent of the well-known depletion interactions in colloid-polymer mixtures. Finally, I will touch upon how the study of interactions between soft and active matter can be extended to more complex biological systems such as microbial biofilms as well as mechanics and flows in the intestine of the worm Caenorhabditis elegans.