Gecko-inspired contact-sensible and self-adaptive soft gripping of curved flexible surfaces

Soft grippers are key manipulation tools for robotics and end effectors for securely grasping of objects with various shapes, sizes on demand. However, there still present critical challenges, including self-adaptive grasping to curved surfaces, and monitoring contact state. Here, a gecko-inspired adhesive gripper for adaptive grasping and critical-contact of curved surface is proposed (CSAG), which consists of a variable-bending pneumatic actuator, a triboelectric sensor(T-sensor), and gecko-inspired microwedge adhesive. The contact-sensible triboelectric sensor can sense the critical-contact state of objects to trigger the variable-bending pneumatic actuator with sufficient shear loading for the gecko-inspired microwedge adhesive. A set of experiments are implemented to verify that the proposed soft gripper can adaptive grasp diverse curved objects, including quail eggs, cans, shuttlecocks, expanding objects with varying volume (like balloons, range of diameter variation is 20-115mm), and spherical acrylic cylinders (20-40 mm) at low pressures (20-25 kPa) with a maximum weight of 37 g, etc. Additionally, the tracking and grasping of a moving ball is demonstrated via mean-shift algorithm based on image recognition coupled with a coordination tracking of a robotic arm. The soft gripper provides a new paradigm to achieve switchable grasping of curved flexible surfaces, which broadens the future applications for versatile unstructured human-robot-environment interactions, such as adaptive robots, and medical devices.