Highly sensitive and large-range strain sensor with a self-compensated two-order structure for human motion detection

Constructing flexible, high-sensitivity strain sensors with large working ranges is an urgent task in view of their widespread applications, including human health monitoring. Herein, we propose a self-compensated two-order structure strategy to significantly enhance the sensitivity and workable range of strain sensors. Three-dimensional printing was employed to construct highly stretchable, conductive polymer composite open meshes, in which the percolation network of graphene sheets constitutes a deformable conductive path. Meanwhile, the graphene layer coated on the open mesh provides an additional conductive path that can compensate spontaneously for the conductivity loss of the percolation network at large strains, through new conductive paths formed by the graphene sheets in the coating layer and the inner networks. At strains lower than 20%, the sliding and disconnection of graphene sheets coated on the mesh surface largely enhance the sensitivity of the sensor, a 20 times increase as opposed to that of the non-two-order structure sensor. The resulting sensor reveals high gauge factors (from 18.5 to 88 443) in a strain range of 0-350% and the exceptional capability to monitor a wide range of human motions, from the subtle pulse, acoustic vibration to breathing and arm bending.