Purpose This study aims to develop a variable stiffness actuator to overcome the limitations of traditional rigid robots in flexibility and the insufficient load capacity of fully soft robots, enabling adaptive and stable grasping of geometrically diverse objects. Design/methodology/approach A dual-jaw three-finger gripper was fabricated using 3D-printed polylactic acid (PLA), which exhibits thermally tunable stiffness. An embedded Joule heating structure, composed of enameled copper wire wound around a steel needle, enables rapid local heating and dynamic stiffness modulation. Magnetic drive mechanisms provide non-contact actuation. Performance was evaluated through thermal response, load capacity, cyclic deformation and stiffness tests, supported by ANSYS thermo-structural simulations. Findings The actuator demonstrated a rigid-to-compliant transition upon heating, with optimal performance at 1.8 A, achieving a maximum joint bending angle of 33°. It supported over 300 g at room temperature and exhibited repeatable deformation over 40 cycles. Simulations closely matched experimental data, validating the thermal and mechanical models. Grasping tests confirmed effective execution of a “rigid approach–compliant wrapping–rigid holding” strategy. Originality/value The proposed PLA-based actuator offers a simple, energy-efficient and versatile solution for adaptive grasping, effectively balancing flexibility and load capacity. Future work will focus on thermal management and control system enhancements.
Fang et al. (Sat,) studied this question.