MEMS Focused Ultrasonic Transducer with Air-Cavity Lens Based on Polydimethylsiloxane (PDMS) Membrane

We present a novel and easy fabrication method to manufacture Polydimethylsiloxane (PDMS) Fresnel air-cavity acoustic lens for focused ultrasonic transducers with long focal length. The process involves casting PDMS membrane with a silicon mold and bonding the PDMS membrane on a lead zirconate titanate (PZT) sheet with ultraviolet (UV)-curable adhesive. A 2.32-MHz focused ultrasonic transducer fabricated with the new method is capable of ejecting water droplets up to 1 mm in diameter (controlled by driving pulse width), from water surface 25 mm above the transducer.