Photodeformable Azobenzene‐Containing Liquid Crystal Polymers and Soft Actuators

Abstract

Photodeformable liquid crystal polymers (LCPs) that adapt their shapes in response to light have aroused a dramatic growth of interest in the past decades, since light as a stimulus enables the remote control and diverse deformations of materials. This review focuses on the growing research on photodeformable LCPs, including their basic actuation mechanisms, the various deformation modes, the newly designed molecular structures, and the improvement of processing techniques. Special attention is devoted to the novel molecular structures of LCPs, which allow for easy processing and alignment. The soft actuators with various deformation modes such as bending, twisting, and rolling in response to light are also covered with the emphasis on their photo‐induced bionic functions. Potential applications in energy harvesting, self‐cleaning surfaces, sensors, and photo‐controlled microfluidics are further illustrated. The existing challenges and future directions are discussed at the end of this review.

Driving Smart Molecular Systems by Artificial Molecular Machines

“…Liquid crystals exhibit a highly ordered structure resulting from anisotropy in solution or molten state, which may provide a favorable work environment for molecular machines and therefore to achieve practical functions. Many liquid crystal–doped systems have been designed over the past few decades . In 2006, Feringa et al embedded light‐driven chiral molecular motors into a cholesteric liquid crystal film, forcing this film to adopt the helicity of molecular motors.…”

Pros and Cons: Magnetic versus Optical Microrobots

“…Two main mechanisms exist for creating deformation for such polymer networks. The first one is based on a configurational shape change of part of the molecule (e.g., an azobenzene group) upon light absorption, which disturbs the order of the liquid‐crystal network 14. The second one makes use of an intermediate heating step where light is absorbed and a shape change occurs through local heating 15…”

Liquid Crystal Networks on Thermoplastics: Reprogrammable Photo‐Responsive Actuators

“…The tuneable molecular architecture of LCNs prior to polymerization allows for programmed actuation such as bending, twisting or rolling. Multi‐modal shape morphing such as helical winding and unwinding within single liquid crystal (LC) actuators has been realized by employing different cutting directions, dual‐layer actuators with contrasting orientation directions, alignment control through directional printing or patterning . However, in these examples, the covalent crosslinked nature of the network prevents recyclable shape programming.…”