Skin‐Inspired, High‐Sensitive, Nanocrack‐Based Flexible Three‐Directional Force Sensor for Soft Robots’ Sensing

Abstract Three‐directional flexible force sensors capable of distinguishing and detecting normal and shear forces are crucial for object perception in soft robotics. Inspired by the spinosum and mechanoreceptors in human skin for three‐directional force sensing, a three‐directional flexible force sensor is proposed by using a pillar as the spinosum and employing circumferentially arranged nanocrack‐based strain sensing units as ultra‐sensitive mechanoreceptors. The sensor can discern normal and shear forces by analyzing deformations of four sensing units. Sensitivity for normal and shear forces of the sensor is 12.23/N and 0.21/N, respectively, within ranges of 0–0.41 N and 0–0.75 N. By integrating the sensor into a soft gripper, a smart soft gripper is constructed. The smart soft gripper can perceive not only the contact and separation between the object and gripper through normal force detection, but also the sliding and landing of the gripped object through shear force detection.