Design and implementation of electrostatic micro-actuators in ultrasonic frequency on a flexible substrate, PEN (polyethylene naphthalate)

We present an electrostatic actuator fabricated on a flexible polyethylene naphthalate (PEN) substrate, which emits acoustic waves at ultrasonic frequencies. The MEMS actuator has a suspended parylene diaphragm which consists of 2–6 mm diameter and 6 μm gap between the diaphragm and substrate. Driving circuitry consists of voltage controlled oscillator (VCO) and output buffer chain, and was fabricated by Arizona State University's Flexible Display Center-IC process. The fabricated actuator emits ultrasonic waves at 25 kHz, and acoustic sound pressure of 27 dB SPL (sound pressure level) driven by the hydrogenated amorphous silicon (a-Si:H) circuitry.