Physics and Applications of Active Complex Solids

综述液晶弹性体（LCE）联合收割机结合了纳米级的液晶和近晶液晶，以及橡胶的弱固体特性。因此，在交联形成这些特殊橡胶的液晶聚合物中存在取向和分层顺序。这种有序性来自于以化学方式结合到聚合物中的棒。橡胶和液晶一样，在分子水平上是流体状的。LCE与传统橡胶一样，只是它们的宏观形状反映了其底层聚合物的各向异性。当冷却通过热各向同性到相变时，它们可以延伸100 s %。它们在加热时再次收缩。这种变化同样可以通过将光照射到含有染料的LCE上来诱导，随后在黑暗中恢复。我们称这些光致材料为光弹性体。我们的目标是开发这些材料用于设备应用，例如通过光致动来制造新型微流体设备。我们设想可以通过光操作的微阀阻塞的通道，或者通过光驱动的蠕动泵沿着通道泵送流体。光栅和反射镜可以光学写入LCE薄膜，纳米级与力学性能的耦合也可以通过其旋转而不是通过其（暂时）破坏。垂直于有序方向施加的应变可以引起有序旋转，并发生形状变形。在人造橡胶中，折射率存在周期性的调制。人们得到一个光子带固体，类似于一个电子带固体，给一个半导体。在橡胶中，这些是可变形的光子带结构，其结果是获得机械移动的激光颜色。这项提议的目的是了解如何使这些带状固体更完美地用于可调谐激光器件。层状液晶（Smectics）产生具有更丰富行为的橡胶。它们的机械响应在其二维层中可以是橡胶状的，而在第三层中可以是固体状的。在倾斜的手性形式下，它们是软固体铁电体，也就是说它们具有自发极化方向。它们作为铁电体的独特之处在于它们在局部水平上是液体状的，而不是非常坚硬的陶瓷。它们的偏振方向可以被诱导以响应于特定剪切而旋转。相反，施加电场会使极化方向旋转，从而产生剪切。前者可以是传感器，后者可以是致动器。我们的目标是开发这些材料作为设备。我们已经写了液晶弹性体（牛津大学出版社，2003年），这已成为标准的研究专著在该领域。第一章（沿着内容和前言）可在网络上获得（http：//www.tcm.phy.cam.ac.uk/tummw141/），并为非专业观众总结了我们旨在探索其材料和器械潜力的影响。在同一页上有热致动薄膜和弯曲机（热光弹性体）的链接。

SummaryLiquid crystal elastomers (LCEs) combine the nano-scale order of nematic and smectic liquid crystals, with the weak solid character of rubber. Thus there is orientational and layering order in the liquid crystalline polymers that are crosslinked to form these special rubbers. The ordering arises from the rods that are incorporated chemically into the polymers. Rubber, like liquid crystals, is fluid-like at the molecular level. It is thus capable of huge extensions that are more like the flow of a liquid.LCEs are the same as classical rubber, except that they take a macroscopic shape that reflects the anisotropy of their underlying polymers. They can extend by 100s% when cooling through the thermal isotropic to nematic transition. They contract again on heating. Such changes can be equally induced by shining light onto dye-containing LCEs, with subsequent recovery in the dark. We called these light actuated materials photo-elastomers.We aim to develop these materials for device applications, for instance actuation by light to make new types of microfluidic devices. We envisage channels that can be blocked by a light-operated micro-valve, or fluid pumped along channels by a light-driven peristaltic pump. Gratings and reflectors could be optically written into LCE films.The coupling of nano-order to mechanical properties can also be from its rotation instead of by its (temporary) destruction. Strains applied perpendicular to the ordering direction can induce the order to rotate, with shape deformations occurring sympathetically. In cholesteric rubber there is a periodic modulation of the refractive index. One gets a photonic band solid, analogous to an electronic band solid that gives one semi-conductors. In rubber these are deformable photonic band structures, with the consequence one gets a mechanically shifting laser colour. An object of this proposal is to understand how to make these band solids more perfect for tunable laser devices.The layered liquid crystals (Smectics) yield rubbers with even richer behaviour. Their mechanical response can be rubbery in the 2-dimensions of their layers, and solid-like in the third. In their tilted, chiral form, they are soft solid ferro-electrics, that is they have a direction of spontaneous electric polarisation. They are unique as ferro-electrics in that they are liquid-like at the local level, rather than being very hard ceramics. Their polarisation direction can be induced to rotate in response to particular shears. Inversely, applying an electric field causes the polarisation direction to rotate and hence shears to develop. The former could be a sensor, the latter an actuator. We aim to exploit these materials as devices.We have written Liquid Crystal Elastomers (OUP, 2003) which has become the standard research monograph in the field. The first chapter (along with the contents and preface) is available on the web (http://www.tcm.phy.cam.ac.uk/~mw141/) and summarises for a non-specialist audience the effects we aim to explore for their materials and device potential. There are links on the same page to films of thermal actuation, and to benders (both thermo- photo-elastomeric).