The Casimir Force in Complex Topologies and its Utility in Nanomachines

量子理论预言，一个所有物理粒子和所有可探测的能量都被移除的完美真空远非空无一物，而是包含了一个出现和消失的虚拟粒子的“海洋”。这些促成了所谓的真空的“零点能量”（实际上是巨大的），我们所意识到的所有物理过程都发生在它的上面。我们没有办法直接探测零点能量，因为我们宇宙中所有可观测到的现象都涉及真空水平之上的“额外”能量。然而，零点能量以微妙的方式表现出来，其中之一，由亨德里克·卡西米尔在1948年预测，是两个完美的反射器放置在空间中，以这样一种方式干扰局部零点能量，从而在它们之间产生吸引力。在过去的十年里，卡西米尔力的测量相当精确，与理论的比较，包括实际材料的实际反射率，现在与实验一致，超过10%，这种奇怪的“无中生有的力”是一个实验现实。对于小于1微米的间隙，卡西米尔力变得相当显著，在这种尺寸和更小的间隙很常见的微型机器中，这是一个相当大的问题，并在所有组件中产生基本的“粘性”，没有逃逸。卡西米尔力取决于腔体的材料和拓扑结构，学习控制它变得非常重要。事实上，最新的研究试图从根本上解决这个问题，利用卡西米尔力作为一种有用的方法，通过真空在中性表面之间传递力，而不需要物理接触。在这方面，两个波纹表面之间报告的“横向”力特别有用，因为移动一个表面往往会将另一个表面向同一方向拖动。现在有更有趣的效应的预测，例如，通过在平行于两个机架的方向上振荡类似的机架，可以在一个方向上获得一个连续的横向力。预测还可以通过改变机架拓扑结构、分离和振荡频率来控制力的方向。它也应该是可能的，以获得一个连续的横向线性力对非对称齿条对（卡西米尔棘轮）通过振荡齿条在一个垂直的方向，并再次控制力的大小和方向。本提案中的联盟由直接在该领域工作的实验和理论小组组成，并设计了一台能够测量这些不同几何形状的横向卡西米尔力的微型机器。这个提议中最激进的想法是试图通过在其中一个表面涂上一层“超材料”来逆转卡西米尔力的符号，从而在表面之间产生排斥。这些薄膜具有人工制造的纳米结构，例如微小金属环阵列，其光学特性可以控制。利用联盟中可用的电子束光刻设备，我们估计我们将能够生产出一种超材料，它在板之间的分离处产生排斥，这是容易测量的。这种排斥力将彻底改变微/纳米机器的设计，并使完全无摩擦的轴承表面成为可能。在这个项目中所做的研究将产生一个可控力的“工具包”，所有这些力都是纯粹从真空中获得的，可以用于微/纳米机器的新设计。我们将通过设计一种基于排斥力的新型微加速度计来证明排斥力的效用。

Quantum theory predicts that a perfect vacuum from which all physical particles and all detectable energy have been removed is far from empty but contains a 'sea' of virtual particles that appear and disappear. These contribute to the so-called 'zero-point energy' of empty space (which is in fact collossal) on top of which all the physical processes that we are aware of take place. We have no way of detecting the zero-point energy directly since all the observable phenomena in our universe involve 'extra' energy on top of the vacuum level. The zero-point energy manifests itself in subtle ways however and one of them, predicted by Hendrik Casimir in 1948, is that two perfect reflectors placed in space disturb the local zero-point energy in such a way as to produce an attractive force between them. In the last decade the Casimir force has been measured quite accurately and comparisons with theory that include the actual reflectivity of real materials now agree with experiment to better than 10% and this strange 'force from nothing' is an experimental reality. The Casimir force becomes quite sginficant for gaps of less than 1micrometre and in micro-machines where gaps of this size and smaller are common it is quite a problem and generates a fundamental 'stickiness' in all components from which there is no escape. The Casimir force depends on the materials and topology of the cavity and learning to control it has become very important. In fact the latest research seeks to turn the problem on its head and use the Casimir force as a useful method to transmit force between neutral surfaces through vacuum without physical contact. In this respect a 'lateral' force reported between two corrugated surfaces is particularly useful since moving one surface tends to drag the other remote surface in the same direction. There are now predictions of even more interesting effects, for example it is possible to obtain a continuous lateral force in one direction on a symmetrical rack by oscillating a similar rack in a direction parallel to the two racks. It is predicted that it will also be possible to control the direction of the force by varying the rack topology, separation and oscilation frequency. It should also be possible to obtain a continuous lateral linear force on an asymmetric rack pair (Casimir ratchet) by oscillating the racks in a direction perpendicular to each and again control the magnitude and direction of the force. The consortium in this proposal consists of experimental and theory groups working directly in this field and a micro-machine capable of measuring the lateral Casimir force in these different geometries has been designed.The most radical idea in this proposal is to attempt to reverse the sign of the Casimir force to produce repulsion between the surfaces by coating one of the surfaces with a 'metamaterial'. These are films with an artificially produced nanostructure, for example arrays of tiny metal rings, whose optical properties can be controlled. Using the electron beam lithography facilities available in the consortium we estimate that we will be able to produce a metamaterial that generates repulsion at a separation between the plates where it is easily measurable. Such a repulsive force will revolutionise the design of micro/nano-machines and will enable the creeation of totally frictionless bearing surfaces. The research done in this project will produce a 'toolkit' of controllable forces, all obtained purely from vacuum, which can be utilised in new designs of micro/nano-machines. We will demonstrate the utility of the repulsive force by designing a new type of micro-accelerometer based on it.