Origami-Inspired Soft Actuator Utilizing a Low-Melting-Point Alloy for Multi-Modal Motion and Shape Locking

Origami-inspired soft actuators are increasingly explored in soft robotics for their lightweight design, large deformation range, and ease of fabrication. However, achieving multiple motion modes typically requires several actuators or pressure lines, increasing system complexity and limiting practical deployment. This work presents a compact origamiinspired actuator integrating switchable strain-limiting structures (SSLS) based on a low-melting-point alloy (LMPA) to enable multi-modal motion and shape locking within a single unit. When locally heated, the LMPA melts, allowing the actuator to bend, extend, or contract. Upon cooling, it solidifies and directs the motion of the actuator or locks the configuration without additional energy input. Experimental results demonstrate axial extension of 18%, contraction of 39%, and bending angles of up to 24.6°. By solidifying all LMPA channels in the final configuration, the actuator can achieve stiffening by a factor of 11.6 and the configurations can be locked, so pressure supply is only required during reconfiguration. The proposed approach reduces the number of required pneumatic inputs, enhances structural reconfigurability, and enables energy-efficient, shapelockable designs.