A Stretchable Capacitive Strain Sensor Having Adjustable Elastic Modulus Capability for Wide-Range Force Detection

Stretchable strain sensors are important components of soft robotics, rehabilitation assistance, and human health monitoring systems. However, strain sensors capable of wide-range force detection with adjustable modulus facilities are highly desirable to obtain mechanical feedback in various scenarios. Herein, a stretchable capacitive strain sensor capable of adjustable modulus and wide-range force detection is reported. The sensor consists of two liquid metals (LMs) filled thermoplastic elastomer (TPE) tubes encapsulated in flexible silicone. The adjustable modulus capability of the sensor is attained by mounting the sensor with springs of different elastic coefficients. During electromechanical tests, the elastic coefficient-dependent adjustable modulus is obtained in the range of 0.78-10.3 MPa. After optimizing the performance, a sensor capable of wide force-sensing range (0.07-74 N), high cyclic stability (>3500 cycles), with low hysteresis, good linearity, and fast response time (<50 ms) is achieved. Finally, a digital display system is developed to display the amount of detected force during the loading of the sensor, which confirms the great capability of the sensor to be applied in joint rehabilitation and soft robotic fields.