Surface-normal electrostatic/pneumatic actuator

An electrostatically driven, pneumatic actuator able to generate surface-normal deflections is described. Two sealed, air-filled, concentric chambers that share a membrane and are connected by channels make up the actuator. The portion of the membrane suspended over the outer chamber serves as the movable electrode plate while the conducting substrate acts as the fixed, opposing electrode plate of an electrostatic actuator. When a voltage is applied across the two plates, the outer-chamber membrane deflects towards the substrate, decreasing the volume in the outer chamber. The decreased volume produces a concomitant increase in the pressure in both the outer and inner chamber, causing the membrane over the inner chamber to deflect away from the substrate. The deflection of the membrane over the inner chamber is not only in the opposite direction to the outer membrane deflection, but is also amplified. Prototype surface-normal actuators have been fabricated with inner chamber radii ranging between 100 and 250 μm and outer chamber radii ranging between 200 and 750 μm