Fully Elastic and High-Sensitivity Liquid Metal Sensor Based on Concave–Convex Structured Microchannel for Human Activity Monitoring and Object Recognition Sensor Array

Due to the characteristics of liquid metal such as high conductivity, high fluidity, and good biocompatibility, liquid metal-based sensors have received extensive attention in wearable electronic devices, electronic skin, soft robots, and other fields. However, due to the buffering effect of the high elastic modulus of the flexible substrate, existing liquid metal-based pressure sensors still have shortcomings such as low sensitivity, poor stability, and long response time. This paper shows a method of introducing the concave–convex structure in the linear microchannel through 3D printing to prepare the liquid metal-filled microchannel sensor with high sensitivity, fast response, and high stability. The sensor produced by this method can be applied to human health monitoring, and the expanded sensor array can be applied to object recognition. The concave–convex structure enhances the sensitivity (2.17 kPa–1) of the pressure sensor by increasing the deformation of the microchannel through local pressure concentration, and the sensitivity of the sensor with a concave–convex structures is 10 times higher than that without a concave–convex structure. The sensor also exhibits a short response time of 0.27 s and high stability with no significant resistance changes after less than 10 000 loading–unloading cycles. Finally, the sensor is used for pulse monitoring and human joint motion monitoring as well as for the preparation of a flexible sensor array and its application for item identification.