The design and control of catalytic motors: Manipulating colloids and fluids with self-generated forces

Microfabrication was employed to pattern silver (Ag) on a gold (Au) surface. The two metals served as bimetallic heterogeneous catalysts for the heterogeneous decomposition of H₂O₂. Silver was the cathode, carrying out H₂O₂ reduction (to water) and gold the anode carrying out H₂O₂ oxidation (to oxygen). Both protons and electrons are created at the anode (as a part of the reaction) and migrate to the cathode (migration of ions is a current) where they are consumed. An electric field is thereby established (migration of ions obeys Ohm's law), which passively pumps fluids through electroosmosis. Electrophoresis is also present as either an additive component to the electroosmotic flow or results in pattern formation (occurs at point where electroosmosis is equal and opposite to that of electrophoresis). Herein, we describe the testing of the electrokinetic model, chemical methods to tune the tracer behavior (convection to pattern formation) and design of asymmetric patterns through microfabrication.