Visuo‐Tactile Sensor Enabled by Cholesteric Liquid Crystal Elastomer for Soft Robotics

ABSTRACT The widespread adoption of automation to work alongside humans has opened opportunities to integrate soft robotic grippers with a sense of touch for executing a wide variety of tasks. In this work, we demonstrate a visuo‐tactile sensor for soft grippers, which is based on cholesteric liquid crystal elastomers (CLCE) that uses an embedded camera‐vision system to convert the force distribution on the contact surface into an RGB map, to detect and distinguish the applied force without complex transmission and processing of electrical signals. A new method was developed for rapid and cost‐effective fabrication of wafer‐scale CLCE sensing layers with high sensitivity and excellent mechanochromic performance. By integrating the CLCE sensing layer with a 3D‐printed array of microtips, mili‐Newton forces can be detected by color changes with a resolution of ∼2 mN. Through an optimization algorithm, the computational load of color image processing is minimized, and real‐time fast processing of color signals and high‐precision tactile force prediction are performed using a low‐cost Raspberry Pi 4 camera. The processed signal guides a soft robotic gripper to complete grasping actions through a closed‐loop force control. The integration of such mechanochromic films with suitable mechanical actuators could lead to miniaturized and untethered tactile sensors.