Freeform Fabrication of Pneumatic Soft Robots via Multi-Material Jointed Direct Ink Writing

Pneumatically actuated soft robots have attracted significant attention in recent years due to their non-linear structures for performing biomimetic motions to enhance human-machine interactions. However, manufacturing soft robots, especially those featuring complex 3D structures, still faces significant challenges as traditional lithography-based micro/nanofabrication technologies have some limitations, such as limited material choices and layer-by-layer architectures. In this work, a facile multi-material jointed direct ink writing (MJDIW) printing method is introduced. In comparing with the traditional micro/nanofabrication and other additive manufacturing methods, the method enables truly freeform 3D printing to fabricate entirely soft actuators and robots with complex 3D structures, while integrating materials with different mechanical characteristics to expand the manufacturing capabilities of additive manufacturing methods. The material properties and printing parameters, and conducted finite element analysis (FEA) is systematically investigated to provide the general design guidelines through simulating actuator motions. Several actuators such as linear elongation and bending actuators are manufactured either by employing a single material or multiple materials with different mechanical properties. Finally, a multi-directional soft manipulator with complex internal channels is printed using different materials to illustrate the versatility of the printing methods.