Silicon-photonics optoacoustic sensor for fully wearable blood pressure monitoring.

Cuffless blood pressure monitoring is essential for continuous cardiovascular assessment. Current wearable approaches rely on pulse-echo ultrasound patches that track pulsating arterial diameters. However, multi-element designs and precise alignment complicate their applicability as a fully wearable solution. We overcome these challenges by using a highly miniaturized silicon-photonics acoustic detector and optoacoustic excitation to generate ultrasound waves inside the artery. The superior contrast in these optoacoustic signals and the detector's semi-isotropic sensitivity enable robust artery diameter monitoring with a single detection element, achieving high tolerance to translation and rotation. The detector's high sensitivity, achieved despite its small size, enables measuring optoacoustic signals from the radial artery with a high contrast at 100 Hz, capturing the features of the blood pressure waveform. Here, we show that the device's agreement with a reference cuff-based blood pressure monitor highlights the potential of silicon-photonics optoacoustic sensing as a practical solution for continuous, cuffless monitoring in daily life.