Self-Powered Inhomogeneous Strain Sensor Enabled Joint Motion and Three-Dimensional Muscle Sensing

Wearable electronics containing different functional sensors with abilities to meet people's daily needs are highly desirable. Here, a stretchable triboelectric nanogenerator (TENG) for wearable electronics is demonstrated. By stacking two layers of silicone rubbers embedded with silver nanowires (AgNWs) and a Ni foam as electrodes, respectively, the fabricated TENG can serve as a new type of sensor that is wearable, stretchable, skin-friendly, noninvasive, and durable. It can convert mechanical deformation into electric signals. Deformation like stretching and extruding of the TENG results in interlayer rubbing because of inhomogeneous strain, producing triboelectric charges that can induce voltage signals in the electrodes in response to the deformation. On the basis of the principle, a joint sensor based on the TENG is demonstrated, which can generate different output voltages according to the bending degrees of the joint. Furthermore, a three-dimensional sensor integrating three TENGs is fabricated to depict the deformations of different muscle areas. The output voltages of the three TENGs can be simultaneously monitored to reflect the deformation degrees of different muscle areas.