Active particles are colloids performing autonomous non-thermal motion in fluids. One such class of active particles are metallodielectric Janus spheres. In presence of an external electric field, a breakdown in the fluid-flow symmetry around the metallodielectric Janus particles drive their active motion. The motion of Janus particles in electric field remains linear and steering such particles along non-linear 3D trajectories remains a challenge. Here we will present experimental design principles of programming swimming force distribution on the surface of a colloidal particle and thus steering the particles along non-linear complex trajectories. The approach is based on designing the surface patch and particle shape that allows for coupling of force and torque components. We find that such coupling results into 3D helical motion of the active colloids, where the handedness is governed by the patch orientation in applied field. We will present the effect of patch size, shape and applied electric field on the active helical motion of the particles. We will also show that additional dipolar interactions between such particles can drive their assembly into rotating clusters and complex crystals, where individual particle retain their rotational activity. Our approach introduces a new method of programming dynamics of active colloids, which could lead to the development of advanced micromotors, miniature robots and non-equilibrium crystals with unusual response to external stresses.

Programming non-linear active motion of colloids by designing surface force distribution

255th National Meeting (2018)

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