Liquid Metal-Based Sensor With Nonuniform Strain Distribution for Wearable Applications

Microchannel-type flexible strain sensors have aroused great interest in the fields of medical devices, artificial skin, and soft robotics due to their high stretchability, low hysteresis, and excellent durability. However, they are often limited in practical applications because of low sensitivity. In this article, a novel liquid metal-based sensor with nonuniform strain distribution was developed, aimed at enhancing the sensor sensitivity. The sensor was designed with localized changes in cross-sectional area using 3-D printed molds. Compared with the traditional microchannel-type flexible strain sensors with uniform strain distribution, the sensitivity of our developed sensor increased by 18%, demonstrating a good improvement. In addition, the sensor exhibits low hysteresis (0.59%), fast response and recovery time (184 ms), long durability (1000 cycles of stretching/releasing at 100% strain), and excellent dynamic and static performance. Finally, the sensor was applied to a robotic joint and human body joints, such as the neck, elbow, knee, and wrist to capture various activities. The results indicate that the developed flexible strain sensor exhibits outstanding performance, making it a promising candidate for wearable devices.