Electrorotation in graded colloidal suspensions

TL;DR

This paper investigates the dielectric properties of graded colloidal suspensions through electrorotation spectra, using a generalized differential effective dipole approximation, and applies the theory to experimental yeast cell data.

Contribution

It extends the differential effective dipole approximation to non-spherical particles and analyzes how graded profiles affect electrorotation spectra.

Findings

Conductivity profile variations cause red-shift in characteristic frequency.

Dielectric profile variations enhance rotation peaks without affecting frequency.

The model fits experimental yeast cell data well.

Abstract

Biological cells can be treated as composites of graded material inclusions. In addition to biomaterials, graded composites are important in more traditional materials science. In this article, we investigate the electrorotation (ER) spectrum of a graded colloidal suspension in an attempt to discuss its dielectric properties. For that, we use the recently obtained differential effective dipole approximation (DEDA) and generalize it for non-spherical particles. We find that variations in the conductivity profile may make the characteristic frequency red-shifted and have also an effect on the rotation peak. On the other hand, variations in the dielectric profile may enhance the rotation peak, but do not have any significant effect on the characteristic frequency. In the end, we apply our theory to fit experimental data obtained for yeast cells and find good agreement.