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.

Anisotropic 1D contraction motion of polymeric actuating materials has drawn growing interests in fields ranging from soft robotics to biomimetic muscles. Although light‐driven liquid crystal polymers (LCPs) represent promising candidates to realize contraction (<20%) triggered remotely and spatially, there remain multitudes of challenges to develop an LCP system possessing ultralarge contraction rate. Here, a novel strategy combining shape memory effect and photochemical phase transition is presented to realize light‐driven contraction as large as 81% in a newly designed linear liquid crystal copolymer, where the eutectic mesogens of azobenzene and phenyl benzoate self‐organize into the smectic B phase. Importantly, this highly ordered structure as the switching segment firmly locks the stress‐induced strain energy, which is rapidly released by reversible trans–cis photoisomerization that destroys the lamellar liquid crystal phase, therefore leading to such ultralarge contraction. Fibers serve as light‐driven building blocks to achieve precise origami, to mimic the recovery of a “broken” spider web and to screen objects in different sizes, laying new ground for advanced applications of light‐driven LCPs from biomimetic robots to human assists.

a variety of practical applications and definitely merit further investigations. The incorporation of azobenzene chromophore into CLCPs gives rise to photoinduced deformations such as uniaxial contraction/expansion and high-speed bending. [13][14][15][16][17][18][19][20][21][22] The photo mechanical effect resulting from photo responsive CLCP is useful in the development of actuators.There has been growing interest in designing and studying photo responsive composite films by combining CLCPs with commercial polymers, which will reduce cost and enlarge the scopes of the applications of CLCPs. [23,24] Ikeda and co-workers reported various doublelayer films through the lamination of azobenzene-containing CLCP layers on the flexible polyethylene (PE) plastic sheets. As a result, the rotation of a light-driven plastic motor as well as 3D movements such as an inchworm walk and a flexible robotic arm motion was successfully achieved. [25,26] Additionally, a visible-light-driven plastic microrobot composed of CLCP/PE bilayer films could manipulate the object that is about ten times heavier than its own weight effectively. [27] However, these photoresponsive double-layer actuators with an adhesive layer generally suffer from delamination of the two layers after long-term exposure to light source, which results in a decreased lifetime.In fact, another useful method has also been proposed to prepare the photoresponsive composite films by dispersing liquid crystalline polymers (LCPs), LC molecules, or azo compounds in the amorphous polymers. Yu and co-workers achieved the photomechanical conversion in polymer-dispersed LCs (PDLCs) like hybrid films with LCP particles dispersed in polyvinyl alcohol (PVA), yet the responsive rate was very low because of the high glass transition temperature of LCP. [28,29] They prepared various photomobile composite films via doping LC molecules or azo compounds to the polymer. Owing to the immiscibility between the small molecule and the polymer, the poor dispersion inevitably occurred in the hybrid film, which further dramatically decreased the mechanical properties of the composite films and impeded their applications to some degree. [29][30][31] Undoubtedly, the improvement of the miscibility between a photoabsorbent and the polymer matrix will bring the promotion of mechanical properties and bending behaviors of the resulted blend films. Involvement of photoresponsive CLCP to polymer substrate by the dispersion method will provide Photoresponsive Actuators Photoresponsive blend films with post-crosslinked liquid crystalline polymer (CLCP) as a photosensitive component and flexible polyurethane (PU) as the matrix are successfully fabricated. After being uniaxially stretched, even at low concentration, the azobenzene-containing CLCP effectively transfers its photoresponsiveness to the photoinert PU matrix, resulting in the fast photo-induced bending behavior of whole blend film thanks to the effective dispersion of CLCP. Specifically, the blend film shows photo-induced deformations upon ex...

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