An Ultra-Thin and Low-Power Wearable Bladder Volume Monitor Based on PMUT

Monitoring bladder volume is vital for global patients suffering from bladder dysfunction and related diseases. The Piezoelectric Micromachined Ultrasonic Transducer (PMUT) possesses advantages of miniature size (especially the < 1 mm small thickness) and low power consumption, favoring the comfortablity of wearable ultrasound bladder monitor. An effective strategy entails arranging four chips in a T-shaped configuration and simultaneously activating them to acquire position information. Ellipses are fitted in the XY and XZ planes using positional coordinates from 3 chips (middle, left, and right) and 2 chips (middle and top), respectively, combined with the distance between the bladder's anterior and posterior wall. These data form the basis for constructing an ellipsoid to estimate volume, followed by linearizing the output data. Experimental results indicate that the ellipsoid volume fitting is excellent, with very small errors. The system effectively measures bladder volume, showcasing promising application in long term wearable monitoring for bladder dysfunctioner.