Helical Morphing of Liquid Crystal Elastomer Fibers for Tendril-like Actuation

Three-dimensional deformation endows organisms with the capacity to autonomously process environmental stimuli. The transformation of plant tendrils from linear to spiral shapes has garnered considerable interest. Although many artificial soft actuators have been developed, fabricating a responsive spiral fiber resembling tendrils still remains a challenge. Here, we develop liquid crystal elastomer spiral fibers (LCESFs) using a simplified and low-cost approach. Upon heating, the straight LCESFs contract and exhibit tendril-like shape-morphing behaviors such as spiral coiling and winding. Once the heat is withdrawn, the fibers recover their original linear shape. The contraction ratio can reach 73%. Furthermore, we advance the photoresponsiveness of our LCESFs by coating a polydopamine (PDA) layer on the fiber surface. Moreover, we applied LCESFs as a soft gripper to pick up and release objects. The maximum weight lifted by the fiber is 76 times its own weight. These LCESFs are capable of stable and repeatable actuation without noticeable fatigue under cyclic loading. We envision that these thermally and photoresponsive LCESFs combine large contraction with helical morphing, enabling diverse applications in micromachines and soft robotics.