Piezoelectric micromachined ultrasonic transducer (PMUT), owing to the miniaturization, low power consumption, and ease of driving, have become a viable alternative to traditional piezoelectric ceramic transducers in air-coupled ultrasonic ranging applications. However, PMUT suffer from significantly degraded transmission performance due to residual stresses inherent in microelectromechanical systems (MEMS) fabrication processes, which substantially limits their detection range and accuracy in airborne applications. To address this issue, this work presents a novel cantilever-based PMUT design, which incorporates micro-slits along the diagonal of the diaphragm to form four triangular cantilever beams. Additionally, inspired by springs, a flexible spring-folded beam structure is designed at the tail end of the cantilever beams to achieve cooperative vibration of the cantilevers through low stiffness mechanical coupling. This design significantly reduces the diaphragm stiffness, fully releases the residual stress, and enhances the mechanical response of the PMUT. Experimental results confirm that, under a low drive voltage of 1 VPP (−5 V offset), the novel PMUT achieves a high resonant displacement of 16,752 nm at its resonant frequency of 73.67 kHz, representing an increase of 10,951 nm compared to the 4,823 nm displacement of the conventional PMUT. At a 10 cm air distance, the device generates a high sound pressure of 4.8 Pa, equivalent to 107.6 dB (Ref. 2 × 10−5 Pa), which is approximately 6.86 dB higher than conventional PMUT. The new PMUT exhibits a receiving sensitivity of 0.85 mV/Pa, which is an improvement of 0.63 mV/Pa over conventional PMUT. This design significantly enhances the transmission performance of PMUT, showing great potential in high-precision air ranging applications.
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