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

Abstract

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.

Recent Advances of Capacitive Sensors: Materials, Microstructure Designs, Applications, and Opportunities

“…Skin-like sensing [72] Structural health monitoring [76] Biocompatible on-skin monitoring [77] Self-healing sensor [ 78,79] Wide-range force detection [80] Difficult to achieve high sensitivity merits and challenges for abovementioned three types of capacitive sensors.…”

Novel Linear, Piezoresistive, Auxetic Sensors Coated by AAA Battery Active Carbons with Supreme Sensitivity for Human Body Movement Detection

“…Piezoresistive strain sensors, [1][2][3][4][5][6][7] which transform mechanical stimulation into readable optical or electrical signals, have a significant effect on the emerging fields of soft robotics, [8][9][10][11][12][13][14][15][16][17][18] healthcare monitoring, [19][20][21][22][23][24][25][26][27][28] electrical skins, [29][30][31][32][33] and wearable devices. [24,[34][35][36][37][38][39][40][41] For example, stretchable piezoresistive sensors on muscles of the neck profit throat cancer, respiratory disturbance, and diagnosis of defective vocal cords, [18] while those on the wrist of humans help with vibration identification in Parkinson's illness and epilepsy.…”

Configurable direction sensitivity of skin-mounted microfluidic strain sensor with auxetic metamaterial

“…[1][2][3] Especially, the stretchable strain sensors that are able to monitor the deformation in conformal and imperceptible contact with target objects, have demonstrated vast applications in many areas such as wearable devices, [4][5][6][7][8][9][10][11][12][13] soft robotics, 14,15 electronic skin, 16 prosthetics, 17,18 and human-machine interactions. 19 Several mechanisms, including geometrical effect, [20][21][22][23][24][25][26] dilatometric effect, 27,28 piezoresistive effect, [29][30][31] capacitive effect, [32][33][34][35][36] piezoelectric effect [37][38][39][40][41] and triboelectric effect, 38,42,43 have been proposed to transduce the force-induced deformation into desired physical signals. For all these mechanisms, the transduction process is divided into two parts: 1) the mechanical deformation of the device by external force, 2) the variation of the electric signal with the device's deformation.…”