Microrheological Characterisation of Anisotropic Materials

TL;DR

This paper introduces a method to measure anisotropic viscoelastic properties of complex soft materials like biopolymer gels using video particle tracking microrheology, with improvements in accuracy and analysis of aligned DNA gels.

Contribution

It presents a novel approach employing a correlation tensor to identify anisotropy axes and enhances measurement resolution through frequency space filtering.

Findings

Successfully measured anisotropic moduli of DNA gels

Identified the mechanical director in aligned biopolymer gels

Improved displacement resolution in high modulus materials

Abstract

We describe the measurement of anisotropic viscoelastic moduli in complex soft materials, such as biopolymer gels, via video particle tracking microrheology of colloid tracer particles. The use of a correlation tensor to find the axes of maximum anisotropy, and hence the mechanical director, is described. The moduli of an aligned DNA gel are reported, as a test of the technique; this may have implications for high DNA concentrations in vivo. We also discuss the errors in microrheological measurement, and describe the use of frequency space filtering to improve displacement resolution, and hence probe these typically high modulus materials.