A novel crosstalk-free piezoresistive/self-capacitive bimodal sensor for human-robot collaboration

In practical applications of collaborative robots, proximity and pressure sensing capabilities are crucial for ensuring the safety and effectiveness of interaction. This paper proposes a novel method of integrating a bimodal sensor that uses a piezoresistive membrane as a self-capacitive electrode, overcoming the current challenges in integration and signal independence. By optimizing the graphene dispersion concentration, the prepared piezoresistive membrane can meet the initial resistance requirements of the self-capacitive electrode and the high sensitivity requirements of piezoresistive sensing. Experimental trials conducted to characterize the sensor focus on its sensitivity (8.49 MPa⁻¹ /2.75% cm⁻¹), response time, and repeatability for both pressure and proximity sensing. Results indicate successful dual-mode detection with crosstalk-free between the two sensing modalities, achieved by evaluating proximity performance under different pressure conditions. Furthermore, a practical application of a 6-array e-skin mounted on a robotic arm is demonstrated, enabling proximity pause and pressure-based servo position control. This innovative approach enhances the robot's sensing ability and promotes safer and more efficient collaboration between humans and machines.