Liquid Crystal Elastomers: from new material, via new mechanics to new machines

机械机器的核心是一种移动和改变形状的装置。例如，照相机装有按快门、伸展透镜和扩大光圈的机器，汽车装有在转向时转动车轮的机器。然而，传统的工程材料，如钢和塑料，是刚性的，所以机器必须通过将许多刚性元件组合成一个复杂的机构来建造，该机构需要滑动接头（铰链，轴，枢轴等）来允许形状变化。相比之下，生物学用肌肉制造机器，肌肉是一种活跃的工作材料，不仅可以变形，而且本身可以主动改变形状。例如，心脏完全由肌肉构成，通过挤压和扩张心室来泵血。这种方法消除了复杂的机制，并导致简单可靠的机器，往往只有一个单一的部分：肌肉是整个机器。这个项目是关于建立机器与人造肌肉，复制生物学的方法在人体工程学。这项工作是通过发现一类新的人造肌肉，液晶弹性体（LCE）。这些是柔软的橡胶带状固体，但在分子水平上，它们是由微小的刚性杆组成的，所有这些杆都指向同一个方向。如果LCE被加热或照射，它会沿着沿着这个“对齐”方向收缩，就像肌肉沿着沿着它的纤维方向收缩一样。收缩是非常大的，可逆的，并且可以用来施加很大的拉力。如此大而简单的收缩已经令人印象深刻。更好的是，LCE现在可以用编程的空间排列模式来制作。当这些被加热/照明时，这编码了一种收缩模式，将材料变形为一种新的，潜在的复杂形状。例如，具有同心收缩环的LCE圆盘将变形为圆锥体，并且，当它变形时，它可以举起很大的重量，或者做其他机械功。因此，LCE是可编程的机械机器。本项目从如何编程LCE以产生所需形状变化的基本问题开始。我们首先要问的是，一个被编程为给定收缩模式的LCE实际上是如何改变形状的。然后，我们转向更困难的问题，即设计使LCE变形为所需形状所需的收缩模式。我们将在三种不同的LCE系统中解决这些问题：变形为弯曲外壳的平板，变形为在平面上创建浮雕/地形的智能涂层，以及变形为不同3D形状的3D打印形状。我们的方法将理论和计算结合在一起，设计图案并预测形状变化，以及实际的LCE制造，以测试和验证我们的设计。以这种方式将预测和测试结合在一起将创建一个独特的集成LCE工程团队，使快速进展成为可能，并使我们能够制作真实的机器原型。事实上，从最早的阶段开始，我们将设计进行机械工作的图案化LCE，并制造LCE机器。首先是举重：我们将研究如何对平板进行编程，以便在加热/照明时，它变形为具有最大提升能力的三维锥形壳体。下一步将是一个智能涂层的盲文像素变形从平面到疙瘩照明。从这里，它是一个小的一步，以充分盲文显示。更雄心勃勃的是，我们将设计智能表面，在加热/照明方面获得设计师的救济，目标是一个标志出现的安全贴纸。我们的最终目标（与Knowles集团和流体分析合作）是商业LCE微流体-使用LCE构建微小的管道系统，以微小的规模复制实验室的全部功能。我们将设计由光控制/供电的LCE阀门和泵，并将其纳入微流体系统，克服微流体回路复杂性的关键瓶颈。

A mechanical machine, at its heart, is a device that moves and changes shape. E.g. a camera contains machines to click the shutter, extend the lens and dilate the aperture, and a car contains a machine to turn the wheels when steering. However, traditional engineering materials, such a steel and plastic, are rigid, so machines have to be constructed by combining many rigid elements into a complex mechanism with sliding joints (hinges,axels,pivots etc) needed to allow shape change at all. In contrast, biology builds machines out of muscle, an active working material that can not only be deformed, but can itself actively change shape. For example, a heart is built entirely out of muscle, and pumps blood by squeezing and dilating its chambers. This approach eliminates complex mechanisms, and leads to simple reliable machines, often with just a single part: the muscle is the entire machine.This project is about building machines with artificial muscles, reproducing biology's approach in human engineering. The work is enabled by the discovery of a new class of artificial muscle, liquid crystal elastomers (LCEs). These are soft rubber-band like solids, but at a molecular level they are built out of tiny rigid rods, and all these rods point in the same direction. If the LCE is heated or illuminated, it contracts along this "alignment" direction, just like a muscle contracts along its fiber direction. The contraction is dramatically large, reversible, and can be used to exert a large pulling force. Such large-but-simple contractions are already impressive. Even better, LCEs can now be made with a spatial pattern of alignment programmed into them. When these are heated/illuminated, this encodes a pattern of contraction, which morphs the material into a new, potentially complex, shape. For example, an LCE disk with concentric rings of contraction will morph into a cone, and, as it morphs, it can lift a large weight, or do other mechanical work. LCEs are thus programmable mechanical machines.This project starts with fundamental questions about how to program LCEs to produce desired shape changes. We start by asking how an LCE programmed with a given pattern of contraction will actually change shape. We then move to the more difficult problem of designing the pattern of contraction required to make an LCE morph into a desired shape. We will solve these problems in three different LCE systems: flat sheets that morph into curved shells, smart coatings that morph to create relief/topography on a flat surface, and 3-D printed shapes that morph into different 3-D shapes. Our approach draws together theory and computations, to design patterns and predict shape changes, with actual LCE fabrication, to test and validate our designs. Bringing prediction and testing together in this way will create a unique integrated LCE engineering group, enable rapid progress, and allow us to prototype real machines.Indeed, from the earliest stages, we will be designing patterned LCEs that do mechanical work, and making LCE machines. First will be lifters: we will work out how to program a flat sheet so that, on heating/illumination, it morphs into a 3-D cone type shell with maximum lifting ability. Next will be a smart-coating of braille pixels which morph from flat to pimple on illumination. From here, it is a small step to a full braille display. More ambitiously, we will design smart surfaces which acquire designer relief on heating/illumination, targeting a security sticker on which a logo appears. Our ultimate target, (collaborating with the Knowles group and fluidic analytics) is commercial LCE microfluidics - using LCEs to build tiny plumbing systems, that replicate the full functionality of a laboratory at a tiny scale. We will design LCE valves and pumps which are controlled/powered by a light, and incorporate them into microfluidic systems, overcoming a key bottleneck in the complexity of microfluidic circuits.