Bubble-propelled trimetallic microcaps as functional catalytic micromotors

We report on the preparation of trimetallic (Pt/Ni/Au) microcaps using silica particles as templates. Capping of silica particles was performed by simple sputter deposition of metal layers, followed by dissolution of templates to obtain a suspension of microcaps. The microcaps were bubble-propelled to very high speeds (up to similar to 500 mm s(-1) on average) in the presence of 6% hydrogen peroxide as fuel. While the Ni layer provides a directional control of microcaps in an external magnetic field, the Au layer allows surface modification for further applications. We also demonstrate capture and cargo transport of oil droplets by microcap motors.