CMOS-Compatible ZrO₂-Based Film for Photoplethysmography Sensors Enabling Accurate and Sensitive Health Monitoring

Photoplethysmography (PPG) is a simple noninvasive technique for the detection of multiple cardiovascular parameters, such as heart rate, blood oxygen saturation (SpO₂), systolic blood pressure, and diastolic blood pressure. However, the current commercial PPG technology is limited by several factors, including rigidity, bulkiness, high cost, high power consumption of ∼10's mW, poor operational stability under ambient conditions, and susceptibility to motion artifacts. In this work, we overcome many of these limitations using a novel self-powered, miniaturized, low-cost, stable PPG sensor based on a simple CMOS-compatible fluorite-type ferro/pyroelectric Hf_xZr_1-xO₂ thin-film photodetector device. Our novel self-powered photodetector shows 26% higher responsivity and 23% improved sensitivity (perfusion index of 3.7%) for sensing blood volume changes in microvascular tissues compared to conventional PPGs, and a very high accuracy (<2% error) in the estimation of SpO₂. The simple sensor has strong prospects for replacing current PPG sensors for health monitoring applications.