Stable suspension and dispersion-induced transitions from repulsive Casimir forces between fluid-separated eccentric cylinders

TL;DR

This paper demonstrates stable suspension of a silica cylinder inside a metallic cylinder separated by ethanol, driven by repulsive Casimir forces, and reveals a unique orientation transition influenced by material dispersion.

Contribution

It introduces an exact numerical method for analyzing Casimir forces and torques on finite nonplanar objects, revealing novel stable configurations and orientation transitions.

Findings

Stable suspension of silica within metallic cylinders via repulsive Casimir forces.

Square cylinders exhibit stable orientation and position, with a 45-degree transition.

Orientation transition explained by material dispersion effects.

Abstract

Using an exact numerical method for finite nonplanar objects, we demonstrate a stable mechanical suspension of a silica cylinder within a metallic cylinder separated by ethanol, via a repulsive Casimir force between the silica and the metal. We investigate cylinders with both circular and square cross sections, and show that the latter exhibit a stable orientation as well as a stable position, via a method to compute Casimir torques for finite objects. Furthermore, the stable orientation of the square cylinder is shown to undergo an unusual 45 degrees transition as a function of the separation lengthscale, which is explained as a consequence of material dispersion.