A Magnetic Film-Hydrogel Dual-Modal Tactile Sensor for Object Shape and Temperature Perception

Inspired by the ability of human skin to perceive various external stimuli, a dual-modal tactile sensor based on neodymium iron boron (NdFeB) magnetic particles and hydrogel has been developed, which can simultaneously detect changes in pressure and temperature. This sensor utilizes magnetic thin films as the pressure receiving layer, hydrogels as the temperature receiving layer and elastic substrates. At the bottom is a flexible printed circuit board (FPC) with tunnel magnetoresistance components (TMR) soldered. The output characteristics of pressure and temperature were tested. The pressure detection range was $0.05\sim 9$ N, with a sensitivity of 26.72 mV/N. It can detect temperatures ranging from $10~^{\circ }$ C to $80~^{\circ }$ C, and the maximum sensitivity was 10.07%/°C. Coupling tests show that the magnetic loss caused by temperature is relatively low, and pressure will increase the heating rate of the hydrogel and reduce its electrical conductivity. The signal output of this dual-modal sensor is stable and the response recovery speed is fast. A $3\times 3$ array was fabricated and integrated onto a robotic manipulator to grasp and recognize objects. The voltage and conductance signals were converted into feature matrices, achieving dual recognition of the object’s shape and temperature. The tactile perception of human skin was simulated, further enhancing the detection capability of magnetic tactile sensors and providing a broader application prospect for robots in the field of environmental interaction.