MEMS and sensors

In a MEMS electrostatic actuator, if the voltage between two parallel electrodes is doubled, by roughly what factor does the electrostatic attraction between them change? (Assume the gap is unchanged.)

  1. A1/2
  2. B2 times
  3. C4 times
Show answer and explanation

Answer: C. 4 times

The electrostatic attraction between parallel-plate electrodes is F = εAV² / (2d²), proportional to the square of the voltage V. Doubling the voltage therefore quadruples the force. This is why electrostatic actuators need high voltages to produce large forces.

  • A. Raising the voltage increases the force.
  • B. The force is proportional to the square of the voltage, not the voltage itself.
  • C. Correct. 2² = 4 times.
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  2. In a parallel-plate electrostatic actuator, what is the phenomenon called in which, as the voltage rises, the movable electrode suddenly snaps to the fixed electrode once it passes a certain position?
  3. Which method is widely used to evaluate the bias stability (slow drift of the output) of MEMS gyroscopes?
  4. What is the damping called that arises when a MEMS movable plate moves toward a nearby fixed surface and squeezes out the gas between them?
  5. In very small MEMS accelerometers and gyroscopes, which noise, caused by the proof mass jiggling randomly through thermal interaction with surrounding gas molecules and the like, is one limit on resolution?