Near-Field High-Pressure for Tactile Stimulation Based on Under-Glass Capacitive Micromachined Ultrasonic Transducer (CMUT)

This work presents the design, fabrication, and characterization of a Capacitive Micromachined Ultrasonic Transducer (CMUT) for near-field high-pressure tactile stimulation under glass. The device was fabricated using a double oxidation process to achieve high pull-in voltage and stability. A 20-channel annular array was designed with FPGA-based phase control, enabling precise phase adjustments for focused high-pressure transmission. The designed sensitivity was 10.4 kPa/V at 5 MHz in simulation calculation and the measured surface pressure sensitivity was 4 kPa/V. Near-field compensation techniques were applied to match simulations. Implementing the FPGA pulser system, the measured location of the focal point was 2 mm, and the transmit sensitivity at the focal point was 56 kPa/V. Future developments aim to integrate thin glass for improved tactile feedback.