近红外光响应液晶弹性体

Near-Infrared Light Responsive Liquid Crystal Elastomers

刺激-响应液晶弹性体是一类新兴的智能聚合物材料,其在外界刺激(热、光、电、磁场等)下会产生大尺寸的可逆形变,因此具有广阔的应用前景。由于单轴取向的液晶基元的微观顺序或分子结构的变化,整个液晶弹性体材料在液晶相向各向同性相转变过程中可以发生非常大的可逆宏观形变。其中,由于近红外光的强穿透力和对生物组织的低毒性,近红外光响应液晶弹性体受到了科学家们的广泛关注。近红外光响应液晶弹性的变形机制主要分为两大类。一种是通过掺杂无机或有机上转换材料将近红外光转化为低波长的光,激发偶氮苯发生顺反异构化。另一种近红外光响应液晶弹性体利用导热填料的光热效应将光转化为热,从而进一步诱导液晶相向各向同性相转变,从而使液晶弹性体材料发生形变。这些优点使近红外光响应液晶弹性体具有潜在的应用价值,如驱动器、人造器官、智能表面和微型机器人等。本文综述了近红外激光响应材料的研究进展,详细介绍了近红外光响应材料的主要变形机理及其应用,并对近红外光响应液晶弹性体和软驱动器的发展前景进行了展望。

As one booming category of smart polymeric materials,stimuli-responsive liquid crystal elastomers(LCEs)are very promising owing to the large and reversible shape deformations response to external stimuli(heat,light,electric or magnetic field,etc.).Due to the changes of microscopic orders or molecular structures of uniaxial-aligned mesogens,the whole LCE materials could execute very large and reversible macroscopic actuation during the LC-to-isotropic phase transition process.Among them,near-infrared light(NIR-light)responsive LCEs have attracted scientific attention because NIR-light has a strong penetration and low toxicity to biological tissues.The NIR-induced deformation mechanisms of LCEs can be divided into two main categories.One is relying on the trans-cis variations of azobenzene chromophores triggered by NIR-light which can be converted into low-wavelength lights by doping inorganic or organic up-conversion materials.The other type of light-responsive LCEs takes advantage of the photo-thermal effect of thermal conductive fillers to transform light into heat which further induces the LC-to-isotropic phase transition and thus make the LCE materials shrink/expand.These characteristics endow NIR-light responsive LCE materials with potential applications as mechanical actuators,artificial organs,smart surfaces,microrobots,etc.This article reviewes the developments of NIR-light responsive LCEs,and also introduces the main deformation mechanisms and applications of NIR-light responsive LCEs in detail.Besides,the article further provides a view of prospective development in future for NIR-light responsive LCEs and actuators.