Manipulation of inherent deformation traits: research progress in liquid crystal elastomers inspired by mechanical metamaterials

Liquid crystal elastomers are materials that combine the anisotropic properties of liquid crystals and the mechanical properties of polymers, enabling programmable shape changes. Consequently, they have potential applications in various arenas such as flexible electronics, optical devices, and biomedicine. The advanced functional attributes of liquid crystal elastomers primarily derive from the methodologies used in the treatment methods and the fabrication of geometric structures during the preparation process. The different ways to combine the orientation strategies with the structures can endow the materials with complex deformation modes and functions. In recent years, it has been discovered that integrating mechanical metamaterials with liquid crystal elastomers can actualize functionalities and properties that are unattainable with conventional material design, such as biaxial actuation, thermally induced expansion, and omnidirectional motion, which can be applied in arenas including biomedical engineering, electronicfree sensing, and precise vibration management. This paper provides a comprehensive review of the design methods that employ metamaterial concepts for the concurrent structural and orientational construction of liquid crystal elastomers, and their applications, with an introduction on the applications of 3D printing technology in the fabrication of artificial ordered structures and the impact on material performances.