Active Tip Trajectory Control in Zig-Zag Soft Actuators using Modular Strain-Limiting Layers with Phase-Changing Inclusions

Soft actuators are increasingly employed as an alternative to rigid actuators for delicate applications that demand high flexibility and adaptability. Typically fabricated from compliant materials, soft actuators exhibit significant flexibility. However, when alternative movements beyond their primary motion are required, these actuators often need to be redesigned or re-fabricated, which limits their versatility. This research introduces an innovative design for variable stiffness soft pneumatic actuators (SPAs) by incorporating a modular strain-limiting layer (SLL) embedded with phase-changing inclusions, enabling active control of the tip trajectory in 3D-printed zig-zag SPAs. The modular SLLs are fabricated using phase-changing inclusions composed of 40% high aspect ratio Field’s Metal particles in EcoFlex. The results demonstrate that employing three modular SLLs on a single side of the SPA allows active switching between eight distinct stiffness configurations, thereby achieving eight unique tip trajectories. This capability significantly enhances the working envelope and range of tip trajectories compared to conventional SPAs, providing greater adaptability and functionality for a broader range of applications.