(588g) Tuning the Collective Behavior of Active Electrohydrodynamic Motors

As demonstrated in biological systems, breaking the symmetry of surrounding hydrodynamic flow is the key to achieve autonomous locomotion of microscopic motors. In recent years, a variety of synthetic motors have been developed based on different propulsion mechanisms. Although collective motion of those motors has been observed, fine control of the hydrodynamics of individual motors and the resulting assembly behavior is chanlleging. In this talk, we will report our recent observation of collective assembly of asymmetric colloidal motors under an applied aleternating current electric field. Although the motors experience strong dipolar repulsion from each other and are highly active, surprisingly, they assemble into a variety of close-packed and stable structures. We show that, through combined experimental and numerical investigations, it is the electrohydrodynamic interaction between specific parts of the asymmetric motors that drives the assembly. By changing both the interfacial and geometric properties of the colloidal motors via a chemical approach, we can fine-tune their assembly patterns resulting from collective motion of the motors.