A dual-phase annular array CMUT

This study presents the design and implementation of a dual-phase annular array capacitive micromachined ultrasonic transducer (CMUT) capable of operating in both focusing and squeezing modes by controlling phase delays in its channels. The CMUT cells are designed with a target center frequency of 5 MHz, a pressure sensitivity of 10 kPa/V, and a pull-in voltage of 166 V. Fabricated using double oxidation and silicon direct bonding, the device demonstrated a center frequency of 7 MHz in air and 4 MHz in oil, with a surface pressure sensitivity of 7.5 kPa/V. The focusing mode generates a single focal point, while the squeezing mode, with a phase shift of 180°, forms two distinct focal points. Although both modes exhibit similar pattern interference radiation force (PIRF) values, the differing tension and compression patterns suggest distinct potential applications. By dynamically controlling the phase delays in each channel, this CMUT broadens its applicability to various fields, including microparticle manipulation, near-field high intensity focused ultrasound (HIFU), and advanced tactile feedback systems.