Collective Behavior of Self-Propelled Microcapsules

We design a system of synthetic microcapsules that can mimic the behavior of cells. The microcapsules can 'signal' to each other via nanoparticles, and they can undergo motion via a self-induced adhesion gradient on the substrate where they are localized. Hydrodynamic interaction amongst the capsules plays a crucial role in initiating motion. For a train of N capsules moving with velocity U in a straight line, we show that U is proportional to N^-1/2. We illustrate how triggering of the initial motion can be controlled using temperature-sensitive capsules. We also present studies on the collective behavior of these self-propelled capsules when they are allowed to move unconstrained on a surface.