Cuffless Wearable Sphygmomanometers using Dual Digital Optical Frequency Combs in Chalcogenide Chips

Abstract

Sphygmomanometers often inflate a rubber cuff wrapped around the upper arm to measure blood pressure. However, the cuff is uncomfortable and inconvenient, making it highly desirable to develop cuffless sphygmomanometers for continuous monitoring of blood pressure in emergencies and healthcare. Electrical and optical blood pressure sensors provide high sensitivity but often suffer from limited pressure range, temperature drift, slow response and poor wearability. To address the aforementioned limitations, we design and demonstrate a unique cuffless wearable blood pressure sensor (dimensions of 12 mm x 2 mm x 0.5 mm) equipped with two original components: a GeSbS/AsS chalcogenide dual-microring chip as the pressure sensing unit for high sensitivity and wide pressure range, and a dual digital optical frequency comb (DDOFC) system as the detection unit for fast response and low-cost detection. Our sensor is comparable to reported electrical and optical blood pressure sensors in its detection limit (23 Pa) but has a 10-times faster response rate (2 kHz), a 1,000-times longer stable operation (> 4.3x10^7 cycles) and a well-compensated temperature drift (< 0.012 pm/°C) that eliminates the need for temperature control. Our work holds great promise for wearable electronics, mobile healthcare, and human-computer interactions. Moreover, its 2-kHz fast response would enable the capture of previously inaccessible transient details of cardiovascular conditions for critical applications such as in-surgery blood pressure monitoring, orthostatic hypotension studies and unexplored early detection of potential myocardial ischemia and strokes.