Topology optimized design, fabrication and evaluation of a multimaterial soft gripper

In this paper, a systemic approach to design and fabricate a multimaterial soft gripper is proposed. Driven by pneumatic pressure, the soft material inside the gripper acts as integrated actuator and the relatively hard material provides support for its soft body. Because of a large design space, it's hardly to design a multimaterial structure by intuitive or biomimetic approaches. Herein, this structural design problem is tackled by topology optimization approach, where each gripper finger is modeled as a compliant mechanism to achieve its maximum bending deflection. Considering the fabrication process, the soft material structure is preserved unchangeable during the optimization process. Thereafter, the optimized hard material is fabricated through 3D printing and the soft material is created by molding. Characterization experiments show that each gripper finger can undergo 32° bending deformation and exert 0.54N grasping force under 0.05MPa actuation pressure. Moreover, the multimaterial soft gripper can sustain more than 1000 working cycles and grasping a variety of objects ranging from tiny regular skews to large and delicate sunglasses. The proposed design and fabrication approach is freely extendable to soft robots by forming the corresponding optimization model, and stands as a gateway toward high-performance multi-material soft robots.