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This work uses supervised learning to optimize the package design with validated experimental results for piezoelectric micromachined ultrasonic transducers (PMUTs) to increase and alter the sound pressure level (SPL). Advancements as compared to the state-of-art include: (1) a neural network model to achieve a mean squared error of less than 0.65 dB2 post 100 epochs; (2) increased vibration amplitude by 17.9 dBV at the first-mode resonance frequency of 33.5 kHz; and (3) SPL enhancements below the 20 kHz frequency range such as the magnitude increases of more than 60 dBV at 5 kHz. As such, the package design shifts the emitting acoustic energy from the ultrasound to audio range in favor of various applications, including audio speakers.

This work presents a continuous volumetric indoor air temperature measurement scheme using PMUTs (piezoelectric micromachined ultrasonic transducers). Advancements as compared to state-of-art works include: (1) 'volumetric' temperature monitoring instead traditional 'pointwise' temperature information; (2) accurate temperature readings spanning an operational distance of 5 m as validated by a commercial thermometer for 3 days; and (3) capable of detecting global average temperature and local temperature events by installing networked/grid PMUT pairs. This innovative sensing technique could be applicable for the precision control of future building/living environments.

This paper reports a 9-meter-long ultrasonic 3D detector based on a packaged lithium niobate PMUTs (piezoelectric micromachined ultrasonic transducers). Compared with the state-of-the-art reports, three distinctive achievements have been demonstrated: (1) high uniformity and wide bandwidth PMUTs by optimized package designs for highly efficient ultrasonic energy transfer; (2) a long-range receiving beamforming detection scheme on a 4×4 PMUT array for up to 9 m detection rang - comparable to the longest reported range via PMUTs; and (3) 3D detection of multiple static/moving objects with the field of view exceeding 50°. As such, this device is valuable for various applications such as obstacle avoidance when both low power consumption and small form factor are desirable, including aerial drones.

This work presents an air-coupled piezoelectric micromachined ultrasonic transducer (pMUT) with high transmitting acoustic pressure by using sputtered potassium sodium niobate (K,Na)NbO3 (KNN) thin film with a high piezoelectric coefficient (e31 ∼ 8-10 C/m2) and low dielectric constant (ϵr ∼ 260-300) for the first time. The fabricated KNN pMUT with a resonant frequency at 104.5 kHz has been tested to exhibit unprecedented results: (1) high sound pressure level (SPL) of 109 dB/V at a distance of 10 cm, which is 8 times higher than that of AlN-based pMUTs at a similar frequency; (2) low-voltage operation of only 4 volts peak-to-peak amplitude (Vp-p); and (3) good receiving sensitivity. As such, this work presents a new class of high-SPL and low-driving-voltage pMUTs for potential applications in various fields, including consumer electronics, such as but not limited to haptic feedback, loudspeaker, and AR/VR systems.