Casimir Forces in Dynamic Geometries for MEMS/NEMS Design

该项目的目标是利用Casimir力计算方面的理论物理学的最新进展，以便为纳米技术工程师提供适合于设计优化的计算工具，以及为实验人员制作和提供教材，这些教材将为有效利用此类计算工具提供足够的背景。这本教材将使工程师能够接触到量子场论中与Casimir力计算相关的那些方面。量子噪声现象在量子光学(激光物理学)中是众所周知的：正如海森堡测不准原理使粒子不可能同时具有明确的位置和速度一样，它也防止电磁振荡具有精确的零(均方根)振幅。在激光中，量子噪声扮演着重要的角色，因为它最初可以在启动时进行放大过程。从电磁的角度来看，任何设备都由反射或吸收光的部件组成，因此带有一组特征的高次谐波，类似于乐器。同样，与乐器一样，可能的振荡的频率结构很大程度上取决于设备的几何形状(例如，声学情况下的鼓)。即使没有任何振荡被激发(仪器不发出声音)，所有的谐波仍然单独受到量子波动的影响，随着几何设置(调整仪器)的任何变化改变振荡频率，量子噪声能量的变化产生一种可测量的力：卡西米尔效应。虽然这些量子力对大型天体并不重要，但对于典型间隙尺寸在数十纳米范围内的系统来说，它们变得相当强大。特别是，它们是纳米机器中粘着的主要原因--即机器的一个部分接触并粘住另一个部分导致的设备故障。不幸的是，他们的行为往往违背了天真的直觉：虽然人们会认为表面相互远离会导致向更低的振荡频率转变，从而减少能量，但详细的研究表明，卡西米尔力通常是有吸引力的。然而，在非常特殊的条件下，可以在一些巧妙设计的系统中表现出斥力，这些系统涉及某些浸泡液体。此外，由于这些力以不寻常的方式强烈依赖于几何和光学吸收特性，可靠的定量计算因非常困难而臭名昭著--或者更确切地说，如果不求助于相当新颖和冒险的计算方法，基本上是不可行的。

The objective of this project is to utilise recent advances in theoretical physics on Casimir force computations in order to provide computational tools suitable for design optimisation to nanotechnology engineers, as well as to produce and provide teaching material for experimentalists that will give sufficient background to effectively make use of such computational tools. This teaching material will make those aspects of quantum field theory that are relevant for Casimir force calculations accessible to engineers.The phenomenon of quantum noise is well-known in quantum optics (laser physics): Just as Heisenberg's Uncertainty Principle makes it impossible for a particle to have at the same time a well-defined position and velocity, it also prevents electromagnetic oscillations from having a precisely zero (root-mean-square) amplitude. In lasers, this quantum noise plays an important role as it can initially seed the amplification process at start-up.From the electromagnetic perspective, any device consists of components that reflect or absorb light, and hence comes with a characteristic set of higher harmonics , analogous to a musical instrument. Again, as with a musical instrument, the frequency structure of possible oscillations strongly depends on the geometry of the device (e.g. a drum in the acoustic case). Even if no oscillation is excited (the instrument produces no sound), all the harmonics nevertheless are individually subject to quantum fluctuations, and as any change of the geometric set-up ( tuning the instrument ) shifts the oscillation frequencies, the changes in quantum noise energies give rise to a measurable force: the Casimir effect .While these quantum forces are unimportant for large bodies, they become quite strong for systems where typical gap dimensions are in the range of tens of nanometres. In particular, they are a major cause of stiction in nanomachines - i.e. device failure by one part of the machine coming in contact with and sticking to another. Their behaviour unfortunately often defies naive intuition: while one would expect that surfaces moving away from one another would induce a shift to lower oscillation frequencies, hence less energy, a detailed investigation shows that Casimir forces normally are attractive. Nevertheless, under very specific conditions, repulsion could be demonstrated in some cleverly designed systems involving certain immersion liquids. Also, as these forces strongly depend on the geometry and on optical absorption properties in unusual ways, reliable quantitative computations are infamous for being very difficult - or rather, essentially infeasible without resorting to rather novel and adventurous computational approaches.