摘要
液晶弹性体(liquid crystal elastomers,LCEs)是一类优异的软物质形变材料,对热、光、电、磁等外源刺激能够产生驱动响应,具有强刺激响应性、快速和大幅度的形变量以及可逆形变功能.液晶弹性体材料广泛应用于软体机器人、人工肌肉、智能器件和光学防伪等领域,是功能高分子与智能材料的前沿研究方向,具有重要的科学意义和应用价值.近些年,随着结构在软形变材料领域的蓬勃发展,结构功能一体化成为先进形变材料研究的新范畴,通过对驱动器形态的精准设计,将几何结构的物理和机械特征引入主动驱动系统,赋予液晶弹性体材料多重形状变化和驱动功能,提升了材料的灵敏性、响应性、轻质性和功能集成性.本文综述了液晶弹性体的结构功能一体化研究进展,探讨了在形变材料体系的结构功能一体化构建策略和驱动机制,即液晶弹性体取向调控技术与几何结构机械特性的耦合效应.依据形态和功能特点,将结构功能一体化分为常规结构功能一体化(薄膜状、纤维状和管状结构)、智能结构功能一体化(折纸剪纸、机械超材料、双稳态结构、拓扑结构和表面微结构)和组装结构功能一体化.其中,常规结构功能一体化实现了多种复杂形变和自主化运动功能;智能结构一体化强调了新奇和非常规的驱动能力,如折叠展开和精细微结构变化.组装结构功能一体化聚焦模块化组装和集成化控制,满足了软体机器人的功能和应用需求.最后,本文展望了液晶弹性体的结构功能一体化未来发展和研究挑战.
Liquid crystal elastomers(LCEs)are soft matter-based active materials that can generate mechanical responses to external stimuli,such as heat,light,electric fields,and magnetic fields.The mechanical response and actuation mechanism of LCEs are based on the disruption of the ordered LC phases retained in the LCEs upon exposure to stimuli(heat or light).Owing to their strong response to stimuli,fast and large-amplitude deformation,and reversible shape-morphing capability,LCEs are cutting-edge research topics in functional polymers and soft materials.They are of particular interest in the growing areas of soft robots,artificial muscles,and intelligent and optical devices.The major advantages of LCEs for soft robotics and smart devices are programmable shape morphing and functionalities that are derived from the interplay between LC alignment and structural morphology.In recent years,the intelligence of LCEs has increasingly relied on the smartness and properties of the structures,such as the developable deformation of structural folding origami and sustainable rotation derived from the mechanical properties of Möbius strips(i.e.,the torsional strain redistributed away from the twist region).Consequently,structure-function integration has become a new category of research in advanced shape-morphing materials.Owing to the precise structural design of LCEs,the physical and mechanical characteristics of the structures can be used to construct complex deformations and actuating functions in soft actuators.Recent advances in the structure-function integration of liquid crystal elastomers are discussed in this review.The structure-function integration of LCEs relies on the synergistic effect of liquid-crystal alignments with geometric structural characteristics,which enhances the sensitivity,responsiveness,lightness,and integrated functionality of LCE materials.Intrinsic liquid-crystal mesogenic alignment-control technologies can program the magnitude or direction of the local actuation strain.Alignment arises from the application of an external force and includes mechanical alignment,surface alignment,field-assisted alignment,and shear alignment.Many types of geometric structures exist in the field of liquid crystal elastomer materials and actuators,and they exhibit rich functions and deformation methods.This review divides these materials into three major categories,based on their geometric properties and structural morphologies.First,conventional structural forms in biological systems are classified into common structures,including films,fibers,and tubules.Common structure-function integration is used to develop complex shape transformations,various locomotions,and self-sustainable autonomous concepts of LCEs.Second,novel artificially designed structural forms are classified as smart structures,consisting of origami,mechanical metamaterials,topology,bi-stable structures,and topography microstructures.Smart structure-function integration is applied to construct new and unconventional actuation,such as the auxeticity of metamaterials.Third,in integrated structures,the LCEs are regarded as actuation components.This integration emphasizes the modular assembly of multiple functional components and the design of soft robotics.Structurefunction integration realizes in-situ deformation,locomotion in diverse media,snapping-through movements,multimodal motions,autonomous controls,and self-regulation.Despite these recent efforts,several challenges remain.Smart,bistable/multistable,and tensegrity structures embedded in soft robotics have emerged as promising research fields.Numerous geometric structures have not yet been studied,and an in-depth understanding of their novel physical and mechanical properties is required.Unlocking inconvenient functions through the regulation of the spatial form and alignment of LCEs is a crucial challenge in soft actuation fields,the resolution of which will expand the scope of LCE-based structure-function integration.We expect that various disciplines(e.g.,theoretical calculation,chemistry,material,engineering,machinery,and biomedicine)will undertake further collaborations to enrich the concepts,functions,and applications of liquid crystal elastomers.
作者
聂振洲
王猛
杨洪
Zhen-Zhou Nie;Meng Wang;Hong Yang(State Key Laboratory of Digital Medical Engineering,School of Chemistry and Chemical Engineering,Southeast University,Nanjing 211189,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2024年第27期4038-4055,共18页
Chinese Science Bulletin
基金
国家自然科学基金(22325501)
国家重点研发计划(2022YFA1405000)资助。
关键词
液晶弹性体
结构功能一体化
取向调控
软体驱动器
刺激响应材料
liquid crystal elastomer
structure-function integration
alignment
soft actuator
stimulus-responsive material
