Out of Equilibriumness of Light-Activated Colloidal Particles

Center for Soft Matter Research

New York University

Self-propelled micro-particles are intrinsically out-of-equilibrium. This renders their physics far richer than that of passive colloids while relaxing some thermodynamical constraints and give rise to the emergence of complex phenomena e.g. collective behavior, swarming. I will present a new form of self-assembly originating from non-equilibrium driving forces. When activated by light, a set of new self-propelled particles spontaneously assemble into living crystals which form, break, explode and reform somewhere else. We will show that this complex dynamics originates in the competition between self-propulsion of the particles attractive interactions induced respectively by osmotic and phoretic effects. These particles constitute an experimental realization of an artificial bacterium with chemical sensing. We will show that they can also exhibit alternate advanced properties present in living systems, such as rheotaxis, migration in a shear flow. These self propelled particles open new perspectives in the design and the properties of smarter materials.