Novel Flexible Organic Photoplethysmogram Sensor for Continuous Cardiovascular Monitoring

A flexible organic photodetector (OPD) has been developed for a flexible organic photoplethysmography sensor (FOPS) designed to monitor vital cardiovascular parameters such as pulse rate, respiratory rate, blood pressure, and pulse rate variability. This device is fabricated on a flexible substrate, utilizing a blend of PCDTBT and PC71BM as the active layer. The FOPS demonstrates excellent absorption properties across the visible spectrum, which is essential for capturing high-quality arterial pulse signals, known as photoplethysmogram (PPG). Optoelectronic characterization revealed a high response time and an impressive on/off current ratio, enabling the accurate detection of microfeatures within the PPG signal. We successfully utilized the device to monitor PPG signals in both reflection and transmission modes, employing green (530 nm) and red (630 nm) light sources, respectively. The recorded PPG signals were further analyzed to measure cardiovascular parameters. The device also demonstrates the ability to measure blood pressure using two techniques: a cuff-based method in conjunction with the oscillometric waveform (OMW) and a cuff-less technique utilizing an artificial neural network approach. These results highlight the FOPS's potential for integration into wearable medical technology, offering continuous, real-time cardiovascular monitoring in a user-friendly and noninvasive manner.