Investigating the Influence of Printing Parameters on the Helical Deformation of 4D-printed Liquid Crystal Elastomer Fiber-actuators

Liquid crystal elastomers (LCEs) exhibit exceptional reversible deformation and unique physical properties owing to their order-disorder phase transition under external stimuli. Among these deformations, helical structures have attracted attention owing to their distinctive configurations and promising applications in biomimetics and microelectronics. However, the helical deformation behavior of fiber actuators is critically influenced by their morphologies and alignments; yet, the underlying mechanisms are not fully understood. Through a two-step aza-Michael addition reaction and direct ink writing (DIW) 4D printing technology, fiber-based LCE actuators with a core-sheath alignment structure were fabricated and exhibited reversible helical deformation upon heating. By adjusting the printing parameters, the filament number, width, thickness, and core-sheath structure of the fiber actuators can be precisely controlled, resulting in deformation behaviors, such as contraction, bending, and helical twisting. Finite element simulations were performed to investigate the deformation behaviors of the fiber actuators, providing insights into the variations in stress and strain during the shape-changing process, which can be used to explain the shape-morphing mechanism. These findings demonstrate that the precise tuning of printing parameters enables the controllable construction of LCE actuator morphology and customization of their functional properties, paving the way for advanced applications in smart fabrics, biomedical engineering, and flexible electronics.