Ultra-Thin Multi-Modal Soft Sensor Using Liquid-Metal Thin-Film Deposition for Enhanced Human-Robot Interaction

Soft sensors, known for physical compliance and robustness against repeated large deformations, have made significant contributions to the field of human-robot interaction. Many of soft sensors incorporate multiple sensing mechanisms combined for multi-modal sensing, and are capable of decoupling different types of deformation modes. However, integrating more than one sensing element into a soft sensor typically results in an inevitable increase in form factor and design complexity, potentially limiting seamless interactions between the host system with the sensor and the environments. In this study, we introduce an ultra-thin multi-modal soft sensor with a thickness of sub-100 μm. The proposed sensor comprises two resistive sensing elements and a capacitive sensing element, all composed of highly stretchable liquid-metal thin-films fabricated by a thermal evaporation process. The proposed sensor is capable of decoupling three different deformation modes: in-plane strains in two orthogonal axes, and out-of-plane contact pressures. To demonstrate its capabilities within the realm of human-robot interaction, the sensor was placed on a wrist as a sensing skin for teleoperating a robotic arm. The proposed approach highlights the potential of our ultra-thin multi-modal soft sensor in the field of human-robot interaction, providing improved compliance and sensing capabilities while maintaining an extremely slim profile.