A 3D printed Two DoF Soft Robotic Finger With Variable Stiffness

Grippers based on fluid elastomer actuators have shown their ability to manipulate fragile and delicate objects. However, they cannot resist large external force due to their soft material and compliant structure, leading to an unstable or even failed grasp. Low stiffness has limited their applicability. In this paper, we propose a soft robotic finger based on multi-material 3D printing and layer jamming to achieve varied finger bending motion and variable stiffness. The proposed finger has two DoF, including two pneumatic actuators (top actuator and bottom actuator) and each with an integrated layer jamming unit. A prototype of the proposed finger is directly printed out by an Object350Connex 3D printer without requiring an additional casting process. The finger's bending angle and stiffness can be controlled due to the novel actuator design. Experiments were carried out to exam the finger's bending angles. Four finger motion can be achieved and the stiffness of the finger is increased with the aid of the layer jamming mechanism. Multi-material 3D printing technique can provide flexibility to the design of soft robotics, shorten the fabrication process and offer a range of materials to achieve desired mechanical properties.