Fingerprint-inspired surface texture for the enhanced tip pinch performance of a soft robotic hand in lubricated conditions

Abstract

The core capabilities of soft grippers/soft robotic hands are grasping and manipulation. At present, most related research often improves the grasping and manipulation performance by structural design. When soft grippers rely on compressive force and friction to achieve grasping, the influence of the surface microstructure is also significant. Three types of fingerprint-inspired textures with relatively regular patterns were prepared on a silicone rubber surface via mold casting by imitating the three basic shapes of fingerprint patterns (i.e., whorls, loops, and arches). Tribological experiments and tip pinch tests were performed using fingerprint-like silicone rubber films rubbing against glass in dry and lubricated conditions to examine their performance. In addition to the textured surface, a smooth silicone rubber surface was used as a control. The results indicated that the coefficient of friction (COF) of the smooth surface was much higher than that of films with fingerprint-like textures in dry and water-lubricated conditions. The surface with fingerprint-inspired textures achieved a higher COF in oil-lubricated conditions. Adding the fingerprint-like films to the soft robotic fingers improved the tip pinch gripping performance of the soft robotic hand in lubricated conditions. This study demonstrated that the surface texture design provided an effective method for regulating the grasping capability of humanoid robotic hands.