Graphene-Based Hydrogel Strain Sensors with Excellent Breathability for Motion Detection and Communication

Hydrogels are considered as promising materials in developing next-generation wearable sensors due to their intrinsic biocompatibility and low Young's modulus. However, there are few reports on their breathability which is very important for wear comfortability of wearable sensors. Here graphene-based hydrogel is presented with regular pores using microneedles as templates endowing them with excellent breathability (water vapor transmitting rate 2.8 kg d^–1 m^–2), which is near ten times that of human skin (water vapor transmitting rate less than 0.3 kg d^–1 m^–2). A high-performance strain sensor based on this breathable hydrogel is developed. This sensor not only possesses high sensitivity but also has an excellent linearity with strain ranging from 0% to 110%. Based on these performances, this sensor can be applied in monitoring various joint movements and muscle movements. Moreover, it can achieve barrier-free communication through Morse code.