Highly sensitive wearable strain sensor with enhanced working range based on heterogeneous mechanical cracks

Abstract

Despite their extraordinary sensitivity, crack-based strain sensors suffer from narrow strain-sensing ranges. Here, we present a novel heterogeneous crack (HC) structure comprising channel- and network-shaped metal cracks to aid in developing a highly sensitive wearable strain sensor with a significantly enhanced working range. HC structures are obtained by controlling the surface strain of a base elastomer substrate via selective patterning of a conductive polymer composite with a roughened surface in a programmable manner. The rational design of a strain-dependent conduction path, where metal strips defined by channel-shaped cracks connect the patterned network cracked parts under strain, enables a significant enhancement in the working range (up to 100%) while simultaneously ensuring considerable sensitivity (gauge factor of ~79.3 at 0–2% strain), a fast response (~100.9 ms at 2% strain), negligible hysteresis, and highly robust strain-sensing performance under various temperature and humidity conditions. Moreover, the strain-sensing performance of the HC strain sensor can be readily controlled by modulating the physical parameters of the device, such as the overlapping length between adjacent composite patterns. Finally, the fabricated HC strain sensor is stably integrated into a human body and successfully monitored a broad range of real-time human activities, from subtle pulse-induced skin deformations to large-scale joint movements, confirming its potential as a high-performance wearable strain-sensing device.