A Wireless and Passive Flexible Pressure Sensor with High Sensitivity and Wide Range for Rehabilitation Monitoring

This work introduces a wireless, passive, and flexible pressure sensor by combining a radio frequency (RF) sensor with a porous polymer. The porous Ecoflex with tunable porosity and interconnectivity is fabricated by the sacrificial template method, which exhibits superior mechanical compressibility and highly reversible deformation behavior. Then, this porous Ecoflex was sandwiched by flexible electrodes and leveraged electromagnetic coupling for wireless signal transmission to construct a passive pressure sensor. A remarkable sensitivity of 3.04 kPa/MHz across an ultrawide pressure range from 0 to 700 kPa was achieved when the mass ratio of Ecoflex to NaCl was 1:2. It also demonstrates a fast response, excellent cycling stability, and the ability to detect subtle pressure change. Practical applications demonstrate that the sensor can accurately capture motion characteristics during upper limb rehabilitation training, allowing real-time monitoring of multidimensional movements such as wrist flexion and extension and forearm rotation. Moreover, an intelligent recognition system based on this sensor is developed, which achieves 99% accuracy in handwritten digit recognition by integrating neural network models. This research presents a viable strategy for developing next-generation wearable medical devices and intelligent human–machine interfaces.