Viscous Thread Printing (VTP) for Production of Soft Robotic Fingers

Many soft robotic systems use foams in structures and end-effectors, but often incorporate a limited range of homogeneous or laminated foams. These prior foam structures require extensive post-processing or assembly steps for use in soft robotics. Improved control over the production of foam using digital manufacturing tools can produce variable mechanical properties to reduce these issues. Here we show rapidly fabricated, variable stiffness, soft robotic fingers and hands from thermoplastic polyurethane at low-cost using Viscous Thread Printing (VTP) on a material extrusion 3D printer. Demonstrations of variable stiffness fingers are presented with force to angular displacement plots and potential applications are proposed. Experimental results are validated against an FEA model. VTP is shown to produce task-specific, soft robotic structures for compliant applications and opens up new opportunities in accessible, collaborative soft robotics.