A soft tactile sensor based on contact-electrification difference for simultaneous stiffness discrimination and material identification

Tactile perception has become essential to enable robotic manipulation in unstructured environments. Current tactile sensors face fundamental limitations in achieving multimodal perception by a unified sensing principle and compact structure. This work proposes a soft tactile sensor (STS) capable of simultaneously measuring contact force, discriminating stiffness, and identifying materials. The multimodal tactile perception is achieved by contact-electrification difference, which is based on the structure and material design of the STS. Through the contact-electrification difference caused by the structure with different elastic modulus, the STS can effectively separate the contact force and deformation signals for precise stiffness discrimination across 0.06–2 MPa. In addition, by leveraging the contact-electrification properties of three distinct polymer composites, combined with deep learning algorithms, the sensor can classify 12 material types with a high accuracy of 96.4 %. Owing to the compact and soft structure, the STS can be readily integrated into robotic grippers for simultaneous stiffness discrimination and material identification, which not only allows the robots to adjust their grasping force, but guides the operational strategies for interacting with different objects.