Flexible pressure sensor for high-precision measurement of epidermal arterial pulse

The rapid development of flexible pressure sensors (FPSs) has driven pulse-based personalized health monitoring, which is extremely important for the diagnosis and prevention of cardiovascular diseases. However, developing a FPS with a convenient fabrication process to form a natural graded microstructure to capture high-quality physiological signals is still a challenge. In this study, by utilizing polytetrafluoroethylene and Cu powder with a conductive double-sided adhesive, a FPS was developed for high-precision measurement of epidermal arterial pulse based on the principle of triboelectric nanogenerators. By using a convenient coating operation, the Cu powder layer with a 500-nm-scale natural microstructure was formed on the conductive double-sided adhesive. This graded microstructure is composed of Cu powder that enables the FPS to respond sensitively to weak pressure signals, endowing the FPS with a sensitivity of 1.65 V/kPa, response time of 17 ms, and decent stability of up to 4500 cycles. Given its compelling performance, the FPS holds the capability to precisely detect epidermal pulse wave with rich details. The consistency between the pulse waveform at the same position measured by the FPS and a high-precision laser vibrometer (with a displacement resolution of 0.05 pm) is up to 0.9949. Furthermore, the FPS can be applied to acquire pulse wave on different human body parts and monitor arterial pulse changes in real time under different opening and closing behaviors of the arterial vessels. The graded microstructure formed by the Cu powder coating provides a convenient and highly efficient method for mass production of FPSs, which will provide new inspiration for the practical applications of flexible sensors to human health.