Date of Award

Summer 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Engineering Physics

First Advisor

Dentcho A. Genov

Abstract

The emergence of an attractive vacuum force (Casimir force) between two purely dielectric materials can lead to an increase in the friction and the stiction effects in nanoscale devices, resulting in degradation or decreased performance. Thus, it is of high practical importance that the conditions for the reversal of the Casimir force from attractive to repulsive are identified. Although the repulsive Casimir force has been considered for high dielectric materials as an intermediate (between the plates) medium, so far no realistic system has been proposed that can demonstrate quantum levitation with air/vacuum as a host medium. Since air is the natural environment for almost all nano- and microscopic devices, it is therefore imperative to seek a better understanding of the nature of the Casimir force under such ambient conditions. In this thesis, the conditions for achieving quantum levitation at an arbitrary temperature are investigated by considering a simple configuration consisting of two parallel plates separated by air. The proposed parallel-plate designs are based on artificial nano-engineered electromagnetic materials commonly referred to as the electromagnetic metamaterials.

In the case of an ideal system consisting of non-dispersive plates, we have uncovered the existence of six universal Casimir force types. We have also derived an explicit necessary condition for Casimir force reversal as a function of the non-retarded specular functions of the plates. By introducing a modification of the Lifshitz theory, we have performed an extensive investigation of the Casimir force for general dispersive magneto-dielectric plates. Simple necessary and sufficient conditions for force reversal have been derived that can serve as a useful tool in designing quantum levitation systems. Based on the sufficient condition, the complete parametric domain for the Casimir force repulsion has been identified. A strongly magnetic response for at least one of the plates is required to achieve quantum levitation with the air as an intermediate medium.

To achieve magnetism at high frequencies, we have considered three potential metamaterial designs based on the split ring resonators (SRRs), the parallel-wires, and the Ni-polystyrene nanocomposites. The SRRs and the parallel-wires composites are "diamagnetic", whereas the Ni-polystyrene nanocomposites are paramagnetic in nature. By combining the above para- and diamagnetic metamaterial plates, we have demonstrated practically feasible designs of a quantum levitation system. If successfully implemented, the proposed designs could find applications in the frictionless bio-fluid transport devices, the micro and nano-accelerators, and as the coatings for an ultra-clean room environment.

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