Highly Sensitive and Flexible Tactile Sensor Based on Porous Graphene Sponges for Distributed Tactile Sensing in Monitoring Human Motions

This paper presents a highly sensitive and flexible tactile sensor based on 3D microstructure graphene sponges. The graphene sponges are fabricated in a dip-coating process that stacks the graphene layers onto the polyimide scaffolds in a homogeneous graphene solution with graphene oxide serving as the dispersant. The tactile sensor has 3 x 3 sensing units and is fabricated through photoetching, magnetron sputtering, and screen-printing processes. The graphene sponge has relatively low Young's modulus of 16 kPa and is capable of enduring large strains over 60%. Furthermore, the sensor unit with the graphene sponge has a high sensitivity of 0.046 kPa(-1) at 0.3 similar to 10 kPa, a lower sensitivity of 0.007 kPa(-1) at 10 similar to 40 kPa, and shows good reproducibility and dynamic response. The increase in the contact areas of the graphene cell walls inside the graphene sponge and the overlapping areas in the laminated graphene flakes synergistically contribute to the high piezoresistive sensitivity. Body wearing experiments to detect wrist bending and muscle vibration demonstrate that the tactile sensor has potential for monitoring body motion and other biomedical applications.