Liquid crystal based programmable active materials

Abstract Active materials are of great interest to a broad spectrum of scientists, including those in physics, biology, materials science, engineering, and biomedical engineering. Learning how to control active materials in a programmable manner could open opportunities for designing smart materials and micromachines. This review presents advances to program out‐of‐equilibrium active materials, including living bacteria, inanimate colloids, and soft active materials such as stimuli‐responsive liquid crystal (LC) polymer networks. The collective dynamics of microscopic bacteria can be controlled to form vortices and polar jets by using topological defects and patterns in LC. Similarly, the collective transport and programmable reconfigurations of microscopic colloids are achieved through the manipulation of LC defect structures. Additionally, the nanoscale orientational order in topological patterns can be incorporated into LC polymer networks to control the complex patterning of nanofiber structures. Furthermore, when the molecular orientations of topological defects are combined with the geometrical shapes of liquid crystal elastomer kirigami, macroscopic morphing behaviors can be programmed by manipulating the interplay between topological profiles and kirigami shapes. Hence, the programmable active materials discussed in this review encompass topics ranging from the collective dynamics of microscopically inanimate and living objects to the macroscopic shape morphing of polymeric constructs. Finally, this review provides perspectives on future opportunities and will inspire advancements in fields such as responsive materials, soft robotics, and tissue engineering.