Development of a wristwatch-type PPG array sensor module

In this work, we address a new photoplethysmography (PPG) signal sensing method using a wristwatch-type PPG array sensor. According to the development of the ubiquitous health care system, the many types of medical equipment and treatments have been improved. In conventional PPG signal sensing approaches, the finger-type PPG probe has been used. However, the finger-type PPG probe requires tight fitting that restricts movement, meaning that patients should endure dome discomfort while wearing it. To solve this problem, we propose a novel PPG array sensor module with a wristwatch-type design. The proposed module measures the PPG signal from the radial artery and the ulnar artery of the wrist, whereas previous methods obtained it from capillaries of the skin. Moreover, we placed photo transistors (ST-23G) and infrared emitting diodes (EL-23G) in an array form to improve the PPG signal sensitivity and level of accuracy. Various arrays are considered for optimization, and a conductive fiber wristband is employed to reduce external noise. In the experiments, the proposed module is assessed and compared with the commercial product TSD200 by Biopac, Ltd.