Bidirectional electrowetting actuation with voltage polarity dependence

This work presents an electrowetting system in which the actuation direction depends on the polarity of the applied voltage. Since electrowetting response depends on the voltage squared, it is typically independent of voltage sign to first order. However, the introduction of an electrochemical diode into the equivalent electrical circuit permits polarity-dependent behavior. Electrochemical diodes were created by making holes in the dielectric. The aluminum electrodes passivate and prevent current flow in one direction, creating diodelike electrical behavior with high breakdown voltage. The resulting actuation forces were directly measured and are of comparable magnitude for both actuation directions.