A conformal piezoelectric microsystem for demographic-adaptive and calibration-free cuffless blood pressure monitoring

Frequent recalibration poses a significant challenge to the accuracy and reliability of current cuffless blood pressure (BP) monitoring devices, especially in long-term use. Here, we introduce a conformal and stretchable piezoelectric microsystem (CSPM) combined with a demographic-adaptive BP estimation model, enabling calibration-free, continuous BP tracking with accuracy comparable to cuff-based medical devices. The CSPM integrates an ultrasound transducer array for vessel diameter waveform recording and two pulse waveform (PWF) sensors with cavity-enhanced piezoelectric thin films for precise pulse wave detection, enabling simultaneous measurement of pulse wave velocity (PWV) and vessel diameter in the same localized vascular area. Leveraging real-time PWV and vessel diameter inputs, our BP algorithm employs a demographic feature learning module for broad population applicability and a time decay compensation strategy to address minor slippage and measurement shifts, enabling the acquisition of individual BP values without calibration. This innovation effectively addresses key challenges in population recalibration and multimodal integration, enabling stable long-term continuous BP tracking, achieving mean absolute errors of 5.22 mmHg for systolic BP and 4.57 mmHg for diastolic BP.