Electrical Impedance Matching to Curved PMUTs Enabling 1V Low Voltage Ultrasound Radial Artery Monitoring

This work presents a curved piezoelectric micromachined ultrasonic transducer (PMUT) array with an electrical impedance matching network (IMN) for low-voltage vascular monitoring. The curved PMUT, fabricated with an AlN-based diaphragm, achieves efficient electromechanical conversion without additional structural layers. To address the impedance mismatch caused by full-electrode coverage, an IMN was designed and optimized at 7.5 MHz, significantly enhancing power transfer efficiency. Pulse-echo measurements demonstrated a 1.7× improvement in sensitivity after matching. Encapsulated with a biocompatible silicone layer, the array enabled direct attachment to human skin for radial artery measurement. With a driving voltage as low as 1 V, the system successfully tracked radial artery diameter changes continuously, offering a safe, power-efficient, and wearable solution for real-time blood pressure monitoring.