Highly stretchable and self-healing strain sensors for motion detection in wireless human-machine interface

The highly stretchable, flexible and self-healing strain sensor is considered as a promising wearable device for motion detection in fields such as robotics and human-machine interface. Herein, a strain sensor with high stretchability and sensitivity is designed and fabricated based on the poly(acrylamide) (PAAm) hydrogel. The ionic conductive PAAm hydrogel shows an excellent self-healing property with fast electrical self-healing speed (within 1.8 s) and high self-healing efficiency (99%). The PAAm hydrogel based strain sensor exhibits excellent performance with large stretchability (>900%), high sensitivity (with maximum gauge factor of 6.44), fast response time (similar to 150 ms), and good cycling durability (>3000 cycles). As the wearable device, the strain sensor can detect various human motions and is able to transmit the data to the smart phone combined with a readout and wireless system. Furthermore, a smart glove was fabricated by coupling multiple strain sensors and the corresponding circuit. The smart glove is capable of expressing and recognizing American Sign Language and can be used to control a robotic hand wirelessly through the hand gestures. Thus, the highly stretchable, self-healing hydrogel-based strain sensor shows a potential application for the human-machine interface, personal healthcare and sports training.