Electro-Orientation and Electro-Rotation of Metallodielectric Janus Particles

TL;DR

This paper develops analytical models for the electro-rotation and electro-orientation of metallodielectric Janus particles, validated by experiments, advancing understanding of their frequency-dependent behavior in electric fields.

Contribution

It provides the first frequency-dependent analytical expressions for JP dipoles, verified experimentally, improving upon previous heuristic or numerical models.

Findings

Analytical expressions match experimental data well.

EROT and EOR spectra are explicitly determined.

Good qualitative agreement between theory and experiments.

Abstract

The electro-rotation (EROT) and electro-orientation (EOR) behavior of metallodielectric (MD) spherical Janus particles (JP) are studied analytically and verified experimentally. This stands in contrast to previous either heuristic or numerically computed models of JP dipoles. First, we obtain frequency-dependent analytic expressions for the corresponding dipole terms for a JP composed of a dielectric and metallic hemispheres, by applying the standard (weak-field) electrokinetic model and using a Fourier-Legendre collocation method for solving two sets of linear equations. EROT and EOR spectra, describing the variation of the JP angular velocity on the forcing frequency of a rotating and non-rotating spatially uniform electric field, respectively, are explicitly determined and compared against experiments (different JP size and solution conductivity). A favorably good qualitative agreement between theory and experimental measurements was found.