An Inductive Multimodal Tactile Sensor With a Warm Touch for Human-Like Perception

The human sense of touch is essential for performing skilled tasks, and it underpins our interaction with the physical world. Despite remarkable progress, developments in robotic senses of touch have been far behind compared to computer vision. In this article, we present an inductive multimodal tactile sensor (IMTS) that explores the eddy-current effect for simultaneous force and temperature sensing. Benefiting from the ac magnetic field coupling mechanism, the force and temperature of top surface can be obtained by monitoring the inductance and resistance of the planar coil. The IMTS achieved a sensing resolution of 1.46 mN for force and $0.51~^{\circ }$ C for temperature with fast response, low hysteresis, and good repeatability. Further tests verified that the IMTS is durable and robust to operate at a force up to 20 N and at temperatures greater than $50~^{\circ }$ C. By mimicking the touch sense of human fingertips, a thermostatic warm-IMTS is able to detect the thermal conductivity of an object accurately. By mounting a warm-IMTS on a soft pneumatic finger, human finger-like multimodal perceptions of subsurface materials, wetness, and wind velocities are demonstrated. In summary, the IMTS shows promising features for applications in robotic tactile sensing and intelligent biomedical tools.