Abstract
Electrically-mediated actuation schemes offer great promise beyond popular pneumatic and suction based ones in soft robotics. However, they often rely on bespoke materials and manufacturing approaches that constrain design flexibility and widespread adoption. Following the recent introduction of a class of architected materials called handed shearing auxetics (HSAs), we present a 3D printing method for rapidly fabricating HSAs and HSA-based soft robots that can be directly driven by servo motors. To date, HSA fabrication has been limited to the laser cutting of extruded teflon tubes. Our work expands the HSA materials palette to include flexible and elastomeric polyurethanes. Herein, we investigate the influence of material composition and geometry on printed HSAs’ mechanical behavior. In addition to individual HSA performance, we evaluate printed HSAs in two soft robotic systems - four degree-of-freedom (DoF) platforms and soft grippers - to confirm that printed HSAs perform similarly to the original teflon HSA designs. Finally, we demonstrate new soft robotic capabilities with 3D printed HSAs, including fully 3D printed HSA fingers, higher force generation in multi-DoF devices, and demonstrations of soft grippers with internal HSA endoskeletons. We anticipate our methods will expedite the design and integration of novel HSAs in electrically-driven soft robots and facilitate broader adoption of HSAs in the field.
Highlights
O NE of the current pressing challenges of soft robotics is identifying methods for actuating soft materials in a way that complements the compliance of soft robots’ bodies
Unlike previous handed shearing auxetics (HSAs), which could only be created from stock PTFE cylinders, we are able to readily 3D print HSAs from RPU, FPU, and elastomeric polyurethane (EPU) resins (Fig. 2(b))
Our 3D printing method makes custom HSA designs possible, ranging from concentric HSAs of varying φ (Fig. 2(c)) and hybrid HSAs assembled by inserting a FPU HSA endoskeleton (φ3) within an EPU HSA (φ1, Fig. 2(d))
Summary
O NE of the current pressing challenges of soft robotics is identifying methods for actuating soft materials in a way that complements the compliance of soft robots’ bodies. Despite the popularity of pneumatic- and vacuum-based actuation techniques, these strategies typically rely on pumps and other bulky, rigid hardware components to achieve complex motions. These auxiliary components consistently complicate the systems-level design of integrated soft robots, limiting their deployment in Manuscript received October 22, 2020; accepted December 21, 2020. Truby and Lillian Chin contributed to this work.)
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