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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.