# Differential Variance Analysis of soft glassy materials: a direct method to quantify and visualize dynamic heterogeneities

## TL;DR

This paper introduces Differential Variance Analysis (DVA), a simple and validated method to quantify and visualize dynamic heterogeneities in amorphous materials using video microscopy, facilitating broader characterization of complex soft matter.

## Contribution

The paper presents a new straightforward method, DVA, for analyzing dynamic heterogeneities in soft glassy materials, validated on colloidal glasses, enabling easier and more accessible measurements.

## Key findings

- DVA effectively quantifies dynamic heterogeneities.
- Differential frames visualize heterogeneities at optimal lag-times.
- Method applicable to various soft materials.

## Abstract

Many amorphous materials show spatially heterogenous dynamics, as different regions of the same system relax at different rates. Such a signature, known as Dynamic Heterogeneity, has been crucial to understand the jamming transition in simple model systems and, currently, is considered very promising to characterize more complex fluids of industrial and biological relevance. Unfortunately, measurements of dynamic heterogeneities typically require sophysticated experimental set-ups and are performed by few specialized groups. It is now possible to quantitatively characterize the relaxation process and the emergence of dynamic heterogeneities using a straightforward method, here validated on video microscopy data of hard-sphere colloidal glasses. We call this method Differential Variance Analysis (DVA), since it focuses on the variance of the differential frames, obtained subtracting images at different lag-times. Moreover, direct visualization of dynamic heterogeneities naturally appears in the differential frames, when the lag-time is set to the one corresponding to the maximum dynamic susceptibility. This approach opens the way to effectively characterize and tailor a wide variety of soft materials, from complex formulated products to biological tissues.