Ultra-sensitive and linear flexible pressure sensors with tri-scale graded microstructures for advanced health monitoring and robotic perception

Abstract

Flexible piezoresistive sensors, which combine high sensitivity and a wide linear detection range, are ideal choices for human health monitoring and robotic perception. However, sensors often exhibit a trade-off between sensitivity and linearity, with challenges caused by the incompressibility of soft materials and the stiffening of microstructures. In this study, a flexible pressure sensor with a 3D ordered tri-scale graded microstructure, fabricated by laser processing, is proposed. The sensor achieves an ultra-high sensitivity of 138.6 kPa−1 and a linear range up to 400 kPa (R2 = 0.99). The compensation behavior derived from the tri-scale graded microstructure's compression deformation counteracts contact hardening and delays sensitivity saturation. Furthermore, the sensor demonstrates a minimum detectable limit as low as 3 Pa, with response and recovery times of 34/39 ms, showing excellent stability after over 24 000 repeated loading cycles. Physiological monitoring confirms that the sensor can accurately capture a wide range of pressure-variations, including those from the carotid artery, jugular vein, respiration, throat vibrations, and foot pressure. Additionally, the sensor can be used for remote operation of robotic hands. This work provides a strategy for manufacturing flexible pressure sensors with a combination of high sensitivity, high linearity, and a wide pressure response range.