Demonstration of MHz Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) Array and the Potential Application in Biomedical Therapies

This paper reports the potential for treating dry eye disease using ScAlN-based piezoelectric micromachined ultrasonic transducers (PMUTs). PMUTs were fabricated on 8-inch cavity silicon-on-insulator wafers. The PMUTs contain 744 (24 × 31) square cells with the dimension of 1.5 × 2.0 mm
²
. The wafer-level electrical characterization showed excellent wafer level uniformity and yield. The resonant frequency variation across the wafer is less than 10%. At resonance (11.6 MHz), the PMUTs array obtained a transmit sensitivity of 18.4 kPa/V @ 10 mm in oil. Ultrasonic heating experiments were performed on a silicone block. A temperature rise of 4℃ was achievable in 48-52 seconds. The heating efficiency of the PMUTs is approximately 2.2 times greater than that of the bulk transducer. These results suggest that PMUTs could potentially replace conventional bulk transducers in the treatment of dry eye disease.