Electrical-Mechanical Transduction

• For the generalized capacitor (potential energy):

•For a linear electrical capacitor:

ε – permitivityA – areaG – Gap

Comb Drive – Another version of the electrostatic actuator.•What is different?

•Before, C=A/g•Now, C=C0+C1x•Linear in x, the direction of motion.•Consequences?

•The Force is constant.

• Look at one finger, treat capacitance as that of a parallel plate capacitor: • Then C=A/g.• A=lt.• C=lt/g, but remember that g is a constant.• So, C=lt/g=C1l (or =C1x)