Monolithic 3D Printing of Origami-Inspired Soft Robotics from Sustainable Bio-Based Resin

Soft robotics has gained significant attention for its potential to deliver safe, adaptable, and biocompatible machines, by embracing the mechanical compliance of soft materials. However, the manufacture of soft robotic devices and machines still largely relies on petroleum-based polymers. Furthermore, in light-induced 3D printing, a key technology for fabricating complex 3D monolithic soft robots, non-sustainable resins remain predominant. This work addresses this issue by developing a photocurable bio-based resin to monolithically fabricate soft robots. We formulate a resin using soybean oil as a renewable precursor and shape it via Digital Light Processing into an origami-inspired vacuum-actuated actuator. The bio-based material has a Young's modulus of 18.9 MPa and an elongation at break of 19.6%. The origami deformation, based on folding rather than stretching, enables actuator operation, despite the lower elongation range of our material compared to silicone elastomers. We report on the characterization of the bulk material properties and the mechanical performance of the actuator, which performs 2000 cycles without failure before testing ceased. Finally, we design and fabricate a monolithic soft robotic gripper with integrated origami actuation using our bio-based material. We show the functional operation of the gripper in grasping different objects, as well as in underwater settings.