Flexible and Soft Inductive Tri-axis Tactile Sensor Using Liquid Metal as Sensing Target

Inductive sensing is a promising approach for flexible and soft tactile sensors; however, magnetic materials used in previously proposed inductive tactile sensors have a trade-off between sensitivity and softness. This paper proposes a flexible and soft inductive tri-axis tactile sensor using liquid metal as the sensing target to overcome this trade-off. We investigated the sensor responses and also compared them with a sensor fabricated using a magnetorheological elastomer (MRE). We demonstrated that a small pool of liquid metal covered with silicone rubber is an effective material for soft inductive sensors. The applied tri-axis force can be obtained through calibration. The results showed that the signal-to-noise ratio was approximately 1.7 times higher and the sensitivities in terms of the shear and normal forces were approximately 6.6 and 4.2 times higher than that observed in the MRE-based inductive sensor, respectively. The proposed sensor offers both high sensitivity and a soft and stretchable surface.