Micro Sensors and Actuators Laboratory

Development of Large Stroke Out-of-plane

Micro Actuators with Applications

§ Micro actuators

Micro actuators are important building blocks for many MEMS devices, which generate forces or displacements to realize scanning, tuning, manipulating or delivering function. Micro electrostatic actuators are more popular than others due to their high compatibility with mature microfabrication processes, low power consumption, simple structure and quick response.

MEMS actuators

§ Conventional attractive force micro electrostatic actuators

Conventional out-of-plane micro electrostatic actuator works under an attractive force between a moving electrode plate and a fixed electrode plate. It has a limited stroke, i.e., <1/3 of the initial gap due to the “pull-in” effect. The initial gap is normally less than 2~3 micrometers by surface-micromachining technology. Another limitation is the low reliability since the moving electrode can easily stick to the fixed electrode.

Conventional attractive force parallel-plate out-of-plane micro electrostatic actuator.

§ Novel repulsive force micro electrostatic actuators

A novel repulsive force electrostatic micro actuator has been developed, which generates a repulsive force to push two electrodes away from each other, such that the displacement is not limited by the initial gap distance and a large stroke can be achieved.

Novel repulsive force out-of-plane micro electrostatic actuator.

(a) (b)

Prototypes of repulsive force translation micro electrostatic actuator. (a) SEM image (b) Confocal images.

§ Performance of repulsive force micro electrostatic actuators

Repulsive force micro actuators output a stroke of one order of magnitude higher than that of conventional attractive force based parallel-plate actuators. The repulsive force actuator is highly compatible with surface-micromachining technology.

§ Applications (optical communication): optical switches and variable optical attenuators

§ Applications (wireless communication): RF MEMS tunable capacitors

§ Other applications: micro assembly and manipulation