The push-pull principle: an electrostatic actuator concept for low distortion acoustic transducers

Area of Science:

• Microelectromechanical Systems (MEMS)
• Solid-state physics
• Acoustic engineering

Background:

• Electrostatic actuators are crucial for MEMS, especially audio transducers in true wireless devices.
• CMOS-compatible materials and low capacitance make them attractive for miniaturization.
• Achieving high audio performance, particularly low total harmonic distortion (THD), is a key challenge.

Purpose of the Study:

• To demonstrate a novel balanced bending electrostatic actuator implementing the push-pull principle.
• To achieve low operating voltages and low harmonic distortion for advanced audio applications.
• To report the theory, fabrication, and performance of this new actuator design.

Main Methods:

• Design and fabrication of a three-electrode balanced bending actuator on a beam.
• Implementation of the push-pull principle for enhanced audio performance.
• Acoustic measurement setup to evaluate harmonic distortion and performance metrics.

Main Results:

• The novel actuator operates effectively at low voltages (6 Vp signal, ±10 Vdc constant).
• Achieved a low harmonic distortion of 1.2% at 79 dB in a standard acoustic setup.
• Demonstrated superior performance compared to previous electrostatic actuator approaches.

Conclusions:

• The balanced bending electrostatic actuator successfully embodies the push-pull principle for MEMS audio transducers.
• This design offers significant improvements in key performance indicators, including low THD and low voltage operation.
• The novel electrode configurations are expected to drive innovation in electrostatic actuator development for diverse applications.