Gripping performance of soft grippers with fingerprint-like surface texture for objects with slippery surfaces

Abstract

Soft robots face challenges when gripping and manipulating objects in lubricated environments, and one of the key issues in medical lubrication conditions in particular. In this study, soft actuators with independent pneumatic driven DIP and PIP joints are designed and prepared based on the anatomy of human fingers. The soft actuators are used to mimic the tip pinch action of the index finger and thumb, achieving dexterous grasping postures adapted to daily life, primarily for fine operation tasks. The bending capability, thrusting force, and fatigue life of the soft actuators are tested. Furthermore, by mimicking the three common fingerprint patterns (i.e., whorls, loops, and arches), three macroscopic surface textures were designed and prepared on the surface of silicone rubber materials. Tribological properties of the surface textures are studied under medical lubrication conditions with hyaluronic acid solution as lubricant. Based on this, tip pinch gripping experiments are conducted on standard shape objects, common medical devices, and biological materials with surface mucus layer. The results showed that the surface of the soft actuators can fit well with the surface of the gripped objects, thereby achieving a larger contact area and enabling the gripping of standard items and common medical devices. Moreover, for biological materials with mucous layer of significant differences in physiological function, the weight that can be gripped is significantly higher than that of the gripper without surface texture.