Wearable optical sensor arrays for cardiovascular health monitoring and biomarker mapping

Abstract

Photoplethysmography (PPG) is an optical technique to study light absorption variations by blood pulsation. We have developed a flexible thin-film photodiode array combined with flexible LED light sources, both integrated into a wearable form factor, to measure PPG signals at various wavelengths and at any location on the human body in reflection. The array contains 256 photodiodes over an area of approximately 4 cm², which can be read out at high frequencies up to 5.4 kHz. The large number of photodiodes operated at high speeds enables spatiotemporal PPG information with a high signal quality. Furthermore, applying independent component analysis to the data array allows for signal quality mapping and enhancement of the PPG signals over the full array. These wearable sensor arrays allow for new types of cardiovascular health related analysis, such as local biomarker mapping and in-situ probing of blood pulsation at different depths underneath the skin.