Friction Enhancement Through Fingerprint-like Soft Surface Textures in Soft Robotic Grippers for Grasping Abilities

Abstract

Flexible surface textures are often utilized in the design of robots that need to manipulate objects requiring a strong frictional force. In this study, we designed and prepared flexible silicone rubber films with surface textures inspired by groove patterns found at the tips of human fingers. These designs included loop, whorl, and arch patterns, as well as horizontal and vertical stripe textures as a control group. On the basis of surface morphology analysis, we established a relative sliding test platform to collect coefficient of friction (COF) through relative sliding tests of soft surface textures and rigid plane contact pairs. The friction coefficient guides the characterization of the contact properties in the finite element simulation process. According to the results of friction testing, the loop, whorl, and horizontal stripe exhibit a higher friction coefficient under variable contact stress, while the arch and vertical stripe display a lower coefficient. The variation patterns of the contact surfaces between a rigid surface and five distinct types of soft surface textures were analyzed by simulating the friction process using Abaqus explicit dynamic analysis. The deformation of the soft surface textures under different contact stresses is subsequently described in terms of elastic strain energy. Compared to the vertical stripe texture, loop, whorl, and arch exhibit greater recoverable strain energy during the relative sliding stage, which means a larger average elastic displacement. Subsequently, different soft surface textures are integrated onto the fingertip of a soft robotic hand, and the grasping ability is evaluated within lubrication-related medical scenarios. The texture perpendicular to the movement direction exhibits a higher friction-producing capability compared to the texture aligned parallel to it. Due to the intricate surface texture patterns, it demonstrates greater adaptability for relative motion in all directions. This research proposes a soft robotic hand incorporating a surface texture resembling fingerprint-like surface texture. By employing experimentation and finite element simulation, this study utilizes surface engineering design to comprehend the contact characteristics involved in the grasping process of a soft robotic hand.

Graphical abstract