Modeling and Characterization of Pulse-Width Modulation Driving of Electrostatic Actuators With Polar Dielectrics

The use of electrostatic actuation is widespread across all areas of MEMS due its speed, ease-of-integration and simplicity. However, its relatively low force density typically requires high driving voltages, especially in parallel-plate configurations. This work presents a modular, high-voltage pulse-width modulation (PWM) driver that can deliver an actuation signal with analogue-like control at voltages of up to 600V and frequencies of up to 10kHz. In comparison to conventional analogue amplifier arrays, this approach can be realized with less expensive components, while enabling using polar liquid dielectrics to boost the resulting force. A detailed analysis of the potential and requirements for liquid dielectrics in combination with PWM is provided as theoretical background. We evaluate the performance of the new driver using a transmissive optofluidic wavefront modulator (Deformable Phase Plate), demonstrating actuation with both non-polar and polar liquid dielectrics. Whereas non-polar liquids lead to a linear force–duty-cycle relationship, the behavior follows a quadratic curve for polar liquids with the maximum force at 50%, with successful operation requiring a minimum frequency depending on the employed liquid. We provide design recommendations for maximizing performance regarding force generation and possible actuation range, taking advantage of the possibility to use polar liquid in electrostatic MEMS actuation. [2025-0106]