Ultrasensitive Flexible Strain Sensor based on Two-Dimensional InSe for Human Motion Surveillance

We demonstrate for the first time a flexible strain sensor based on two-dimensional Indium Selenide (InSe) material for human motion surveillance. The InSe exhibits a highly strain-tunable bandgap property, which enables an effective modulation of electrical conductivity and piezoresistivity. A large gauge factor (GF) of 32 and 36 is achieved even when subject to a low tensile and compressive strain down to ±0.25 %, respectively, manifesting its superior strain sensitivity. Moreover, the GF and piezoresistance coefficient can be significantly enhanced by 8 and 9 folds, respectively, through electrostatic gating. Our work reveals a highly tunable piezoresistive effect and low Young's modulus in InSe that is promising for realizing ultrasensitive human motion sensors, in which the performance can be further enhanced via gating effect using a three-terminal device configuration.