Bioinspired Tunable Helical Fiber-Shaped Strain Sensor with Sensing Controllability for the Rehabilitation of Hemiplegic Patients

Fiber-based strain sensors, as wearable integrated devices, have shown substantial promise in health monitoring. However, current sensors suffer from limited tunability in sensing performance, constraining their adaptability to diverse human motions. Drawing inspiration from the structure of the spiranthes sinensis, this study introduces a unique textile wrapping technique to coil flexible silver (Ag) yarn around the surface of multifilament elastic polyurethane (PU), thereby constructing a helical structure fiber-based strain sensor. The synergistic interaction between the elastic PU core and the outer helical Ag yarn enhances the mechanical strength and stretchability of the sensor, while the external helical Ag yarn offers high conductivity. By adjusting the spacing of Ag yarn coils on the surface of the fiber-based sensor, we achieve precise control over both sensing sensitivity and strain range. Specifically, experimental results show that with a pitch of 1.25 mm, the strain range reaches up to 150%, and the gauge factor (GF) is 2.6; when the pitch is adjusted to 5 mm, within a 60% strain range, the GF value significantly increases to 9.3. Based on these excellent performance metrics, we further apply the sensor as a conductor in ECG monitoring garments, successfully verifying its practicality in cardiac monitoring. Additionally, we developed a smart glove for hand function rehabilitation training, utilizing wireless signal transmission to promote hand function recovery in hemiplegic patients. The sensor is also capable of effectively monitoring respiratory rate and pulse, showing broad prospects in the fields of rehabilitation medicine and smart healthcare.