Casimir Forces in Dynamic Geometries for MEMS/NEMS Design

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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.