Superhydrophobic gradient wrinkle strain sensor with ultra-high sensitivity and broad strain range for motion monitoring†

Flexible strain sensors have potential applications in electronic skin, healthcare monitoring, human-machine interface, and other fields. The key challenge in the use of the strain sensor for human motion monitoring is that both broad strain range and full-range high sensitivity have to be achieved simultaneously. Herein, we report a gradient wrinkle strain sensor based on reduced graphene oxide (rGO) and polydimethylsiloxane (PDMS) by a simple pre-stretching method, which includes two wrinkle regions. One region contributes to high sensitivity through wrinkle cracks during stretching, and the other region maintains good contact to provide a broad strain range. The sensitivity can be easily adjusted according to the gradient wrinkle structure. The sensor exhibits a broad strain range (up to 300%), ultra-high sensitivity (a maximum gauge factor (GF) of 167 665.6), good stability (10 000 cycles), and a low detection limit (0.1% strain). It can be used to detect full-range human body motions, including subtle physiological signals and large motions. Besides, the sensor has good super-hydrophobicity and anti-corrosion property, which can be used in humidity, underwater, acid, alkali, and other harsh environments. This new structure and sensing mechanism of the strain sensor provides a new idea for achieving high sensitivity in the full range.