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

Abstract

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 2–6mm diameter and 6μm 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 25kHz, and acoustic sound pressure of 27dB SPL (sound pressure level) driven by the hydrogenated amorphous silicon (a-Si:H) circuitry.