(379i) Shape-Directed Motion of Homogeneous Catalytic Micromotors

The purpose of this work is to demonstrate the ability to direct the motion of catalytic nanomotors purely by shape. Since their discovery over a decade ago, catalytic nanomotors have shown promise in a variety of applications. While the dynamics of these motors have been controlled at the ensemble level by a number of external stimuli (e.g. chemical gradients and magnetic fields), a greater degree of control at the individual motor level is desirable. One potential avenue to “program” motor dynamics at the individual particle level is through geometric control. Thus far, the study of purely shape-directed catalytic motors is limited to theory. We use projection photolithography and physical vapor deposition to design homogeneous platinum micromotors with a great degree of control over their shape. Our motors have a “twisted star geometry” (C_nh) that leads them to rotate in hydrogen peroxide solutions at rates proportional to their degree of asymmetry. We propose a self-electrophoretic mechanism where rates of the oxidation and reduction of hydrogen peroxide vary across the surface of the motor. Our results demonstrate that tuning shape is a viable method of encoding micromotor dynamics at the individual particle level. As existing techniques to create colloids with arbitrary geometries become more common, shape-control appears to be a powerful avenue toward programming the dynamics of functional motors and colloidal machines.