Graded Microstructured Flexible Pressure Sensors with High Sensitivity and an Ultrabroad Pressure Range for Epidermal Pulse Monitoring

Precisely detecting epidermal pulse waves with pressure sensors is crucial for pulse-based personalized health-monitoring technologies. However, developing a pressure sensor that simultaneously demonstrates high sensitivity and an ultrabroad pressure range and a convenient fabrication process for large-scale production is a considerable challenge. Herein, by utilizing a commercial conductive fabric (CF) and a silica gel film, we develop a high-performance pressure sensor (HPPS) for the monitoring of human physiological signals. Based on convenient turnover formwork technology, the silica gel film was fabricated by replicating the microstructure of the sandpaper surface. This microstructure and the plain weave structure on the CF surface together provide a sharp increase in the contact-separation area and structural compressibility, which are beneficial for the enhancement of output performance. Made of these two materials, the graded microstructured HPPS holds high sensitivity (4.5 mV/Pa), an ultrabroad pressure range (0-30 kPa), a wide working frequency bandwidth (up to 35 Hz), decent stability (>50,000 cycles), and a simple fabrication process that is suitable for large-scale production. Given these noticeable features, the developed HPPS not only succeeds in precisely detecting subtle pulse waves on various positions of different people but can also objectively capture changes in cardiovascular parameters caused by exercise training at different intensities in real time. These findings exhibit the enormous potential application of HPPS in tracking an individual's health status and comprehensively evaluating exercise intensity.