MultiGrainGripper: Enhancing FinRay Soft Grippers to Grasp Granular Material

FinRay grippers are among the most common soft grippers. Their structure allows them to adapt to the shape of the objects they come into contact with. However, due to its design, FinRay grippers have not been able to grasp granular materials. This paper presents a modified FinRay gripper called MultiGrainGripper that can perform the same grasping tasks as any other FinRay but also grasp granular material (from sugar to flour). This enhanced functionality was realised with by adding a small cavity to the end of each fin. When the MultiGrainGripper is closed, two haves of the cavity come together to form a closed chamber, wrapping around granular material and small items that otherwise would not be grippable. The soft MultiGrainGripper was modelled in finite elements to explore the effect of different designs on the properties of the finger compared to a standard FinRay of the same dimension. Experiments were conducted, grasping a wide range of objects and granular materials. Results show that the MultiGrainGripper can grasp a wider range of objects, from large structures (~10 cm) to a pinch of salt (granules ~100 μm).