Flexible Photoelectric Pulse Detection Sensor and Image Processing of Detection Signal

Biomedical sensors can detect all kinds of human life information. The pulse signal is one of the most important physiological parameters of the human body. An ultra-thin and flexible photoelectric pulse detection sensor is built, a pulse detection system based on the sensor circuit is built, and the image processing of the detected pulse signal is carried out. Oleic acid is used to modify the organic semiconductor layer of the phototransistor. Silver nanoparticles (AgNCs) are also infiltrated into organic semiconductor materials to form nanocomposites. The hardware circuit includes signal amplification, baseline correction, 50 Hz notch filter, and band-pass filter. In the experiment, the prepared nanocomposites are analyzed for photoelectric properties. The results show that the transfer curve of the device is bipolar without illumination, and the hole transport characteristics are more obvious than the electron transport characteristics. The hole mobility is 0.06 mm²/V/S, and the electron mobility is 1.34×10⁻⁴ cm²/V/S. Hole mobility greater than electron mobility can effectively improve photoconductivity gain. The detection of different working voltages shows that the pulse wave detected by the prepared sensor has obvious P, T, and D waves. The image processing technology is used. After the output pulse signal image passes through the notch and low-pass filters, the pulse signal’s high-frequency interference is suppressed. After envelope filtering, the signal frequency amplitude of the pulse signal decreases (from 400 mV–700 mV to −150 mV~150 mV). Then, the baseline drift is effectively removed.