A Fingertip-Size Six-Axis Force Sensor via Origami Coil Arrays for Intrinsic Tactile Sensing

Force and tactile sensing play increasingly important roles in robotics hands to complete complex tasks safely and effectively, complementing the last piece of the puzzle of human-level dexterity. Despite the advances in flexible sensors and skins, tactile sensing at the fingertip of robotic hands remains an open question. Exploiting embedded six-axis force/torque (F/T) sensors for external stimuli estimation, namely, intrinsic tactile sensing, seems to be an effective solution. Here, we present OriCube, an origami-inspired, fingertip-size (14.5 × 14.5 × 12.5 mm³), lightweight (4 g), fully integrated, inductive six-axis F/T sensor. It utilizes an origami coil array to achieve self-decoupled six-axis F/T measurements by detecting the displacements and rotations of a metal shell via eddy–current coupling. A modular silicone spring-based elastomer design allows fine-tuning of the stiffness and performance of each axis independently. The calibrated OriCube exhibits a high resolution of 0.01% F.S. (23 N), low crosstalk (2%), high stability (<0.2% drift in 6 h), and insensitivity to strong magnetic field changes. It is capable of detecting light touch by a feather as well as high impact force when hammered. We demonstrate real-time tactile sensing (contact position and force vector) at the curved surface of a robotic fingertip via one embedded OriCube sensor.