Theoretical Foundation for Design of Friction-Tunable Soft Finger With Wrinkle's Morphology

Abstract

We present a theoretical model for the design of a soft-fingered robotic hand/gripper with a friction-tunable function based on the idea of active wrinkles on its surface. Inspired by the formation of wrinkles on the human finger in a wet environment, our robotic finger is integrated with a pneumatic actuator inside a multilayer soft substrate. Under pressurization, wrinkles are formed on the finger's surface, changing the contact tribology between the finger and the grasped object. In this letter, the morphology of wrinkles (both geometrical and mechanical characteristics) is predicted by the radius basic function network with data collected from an analytical model and experiments. We also investigated the change of the friction coefficient under different wrinkle morphologies using our predicted model. Furthermore, based on our previously proposed beam bundle model, we present a dynamic contact model between a wrinkle and an object to investigate the effect of wrinkle morphological changes on friction's behavior during sliding motions. The theoretical model was validated by experiments. We expect this letter to pave the way for the design of a new type of soft-fingered hand that can actively change its surface morphology for different grasping tasks with tunable friction.