Silicone/epoxy hybrid resins with tunable mechanical and interfacial properties for additive manufacture of soft robots

The multi-material structures found in soft robot bodies, from stretchable elastomers to hard connectors, can display highly distinct physicochemical properties, challenging the engineering of robust interfaces required for long-term performance in real-world scenarios. Here, a novel family of hybrid resins combining platinum-catalyzed silicones with epoxy resins cured by acid anhydrides is reported to enable fabrication of functional multi-material bodies with strong interfaces. By adjusting the composition of the hybrid resins, the elastic modulus can be tuned over an unprecedent ratio of five orders of magnitude (from ~20 kPa to ~2 GPa) with outstanding interfacial toughness (from 1 to 3 kJ m−2). The excellent control of ink rheological behavior via nanoclay addition allows additive manufacturing by direct-ink-writing, enabling seamless control of topology and mechanical properties with sub-millimeter resolution in three dimensions. The significance of this new class of hybrid resins is demonstrated via the fabrication of various functional devices relevant to wearables, healthcare, and soft robotics. Overall, these hybrid resins open new frontiers for the fabrication of the next generation of robust soft robots using single continuous additive manufacturing processes.