Soft Pneumatic Gripper With Interchangeable Fingertips by Using Reversible Polymers: The GraspBerry, a Raspberry Picking Case Study

Abstract

Fingerprints primarily enhance grasping by modulating friction, as the surface pattern affects the friction needed for effective grasping and manipulation. A versatile gripper was developed with a more realistic distal phalange inspired by the human index finger for improved berry gripping performance. The soft pneumatic gripper was fabricated out of a Diels-Alder–based self-healing polymer, leveraging its thermally reversible nature for introducing interchangeable fingertips. Various fingertips were developed with different patterns for optimized grasping of fruits of different shape, size, and stiffness, depending on the type of fruit, level of ripeness, and variations in weather and climate conditions of each harvest season. The fingertips can be mounted and removed easily from the distal phalange of the pneumatic finger by welding and manual disassembly. The gripper was optimized for picking raspberries, exploiting the innovative interchangeable fingertips. The same gripper could successfully harvest berries of different levels of ripeness thanks to three types of interchangeable fingertips with different patterns. The performance of the different fingertips was evaluated in the lab on a physical twin of a raspberry and a 67% success rate was obtained in the field by switching them on the spot to optimize the grasp to the different ripeness level of the berries. The GraspBerry paves the way for the design of versatile grippers with adaptable grasping performance by switching the fingertips for accurate and reliable grasp on different types of crops throughout the various harvesting seasons all year round.