Dielectric charging effects on Parylene electrostatic actuators

We report here the first characterization of dielectric charging effects on Parylene electrostatic actuators. High-resistivity Parylene in-between air gaps can cause undesirable charging effects due to air ionization when operating as electrostatic sensors/actuators at voltages as low as tens of volts. This undesirable effect can either lower the sensitivity of the sensor or increase the pull-in voltage of the actuator. It is further observed that Parylene actuators operating at high voltage could even show "bounce-back" and "pull-in voltage drift" problems. It is concluded that even for MEMS, attention must be paid to the operating voltages and the resistivity of the dielectrics.