Ultrasonic electrostatic actuators on a flexible substrate

We present a MEMS-based electrostatic actuator on a flexible substrate, made of Polyethylene Naphthalate (PEN), which emits acoustic waves at ultrasonic frequencies, aiming for an ultrasound microdevice for equipment inspection. The actuator has a suspended diaphragm, made of parylene, of 2–6 mm diameter and a 6 μm gap between the diaphragm and substrate. A single actuator emits ultrasonic waves at 25 kHz, and pressure of 27 dB SPL (sound pressure level) and a 1 × 2 array emits up to 34.6 dB SPL at 1 cm distance.