Nanorod Pair Complexes Manipulated via Magnetic Casimir Forces

TL;DR

This paper demonstrates how magnetic fluids can be used to control Casimir-Lifshitz interactions between anisotropic nanoparticles, enabling reversible tuning of quantum electromagnetic forces for nanoscale assembly.

Contribution

It introduces a novel method to modulate Casimir interactions using magnetic permeability variations in magnetic fluids, with theoretical predictions for tunable nanoparticle traps.

Findings

Magnetic permeability controls attraction and repulsion between nanoparticles.

Magnetic Casimir traps can be thermally unstable and measurable.

Equilibrium positions of nanoparticles can be modulated by nanoparticle size.

Abstract

Controlling nanoscale interactions to suppress aggregation from short-range attractive forces is a key problem in nanoengineering. Here, we demonstrate a route to modulate Casmir-Lifshitz interactions between anisotropic nanoparticles with the magnetic fluids. By semi-classical quantum electrodynamics, we study ground state dispersion forces for cylindrical dielectric nanorods made of polystyrene (PS), and zinc oxide (ZnO) embedded in toluene-based host media with gold-coated magnetite nanoparticles and also predict magnetic contributions to the non-retarded excited state interaction. The variation in magnetic permeability enables tuning between repulsive and attractive interaction and a thermally unstable and measurable magnetic Casimir traps are predicted between a pair of ZnO-PS nanoparticles whose equilibrium position can be modulated over an order of magnitude with a small variation in the size of the magnetite nanoparticle. This provides an alternative magnetic Casimir-effect pathway to reversibly tune quantum electromagnetic forces at the nanoscale for assembly and enhancement of colloidal stability.