Flexible Strain Sensor Based on Copper/Graphene Composite Films

This study analyzed a flexible strain sensor with torsional low interference, waterproofing, and self-adhesive properties using a copper/graphene microcrack composite film as a strain-sensitive layer and a self-adhesive silica gel as a waterproofing and self-adhesive layer. The sensor exhibits a wide response range (with a strain capability of up to 110%), high sensitivity (with a gauge factor of 847.87 (92% < ε < 110%)), and satisfactory sensing durability (with response cycles of 10000 under 25% strain) and can detect ultrasmall strains (0.2% strain). In addition, the sensor exhibits similar real-time dynamic responses at different strain levels (0%–40%) and states (untwisted, twisted by 90°, and twisted by 180°), indicating its characteristic of torsional low interference. Moreover, the self-adhesive silica gel allows the sensor to directly adhere to the skin surface, reducing motion artifacts and improving the accuracy of monitoring complex strain states during underwater activities. Therefore, the flexible strain sensor holds potential as a next-generation flexible strain sensor for underwater use.