3D-Printable Crease-Free Origami Vacuum Bending Actuators for Soft Robots

While vacuum-based bending actuation offers benefits such as safety and compactness in soft robotics, it is often overlooked due to its limited actuation pressure, which restricts both bending angle and force output. This study presents a crease-free, origami-inspired vacuum bending actuator that advances both state-of-the-art vacuum bending actuators and traditional origami deformation principles by introducing orderly self-folding through optimized stiffness distribution. Achieved through finite element method (FEM), this design provides several advantages: (i) Self-folding allows for high bending angles (up to 138<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>) in a compact form. (ii) The crease-free design facilitates 3D printing from a single soft material using a consumer-level fused filament fabrication (FFF) printer, specifically thermoplastic polyurethane (TPU) with a Shore hardness of 60A, potentially higher flexibility and durability. (iii) The compact configuration enables modular design, supporting reconfiguration as demonstrated in adaptable locomotion soft robots. (iv) The large bending angles allow the actuator to wrap around objects, offering extensive contact compared to other designs. This capability, combined with its vacuum-driven mechanism, enables synergy with self-closing suction cups in an octopus-like vacuum gripper, providing large versatility and grasping force for handling a wide range of objects, from small, irregular shapes to larger, flat items.