# Monitoring spatially heterogeneous dynamics in a drying colloidal thin film

## TL;DR

This paper introduces a novel experimental method to monitor spatially and temporally heterogeneous dynamics in drying colloidal thin films using near-field speckle analysis, enabling detailed insight into the drying process at micrometer scales.

## Contribution

The study presents a new technique for spatially resolved dynamic measurements in complex fluids, combining near-field speckle analysis with periodic modulation to analyze drying colloidal films.

## Key findings

- Successfully monitored heterogeneous dynamics during drying
- Achieved spatial resolution at ten micrometers
- Demonstrated full-field dynamic property mapping

## Abstract

We report on a new type of experiment that enables us to monitor spatially and temporally heterogeneous dynamic properties in complex fluids. Our approach is based on the analysis of near-field speckles produced by light diffusely reflected from the superficial volume of a strongly scattering medium. By periodic modulation of an incident speckle beam we obtain pixel-wise ensemble averages of the structure function coefficient, a measure of the dynamic activity. To illustrate the application of our approach we follow the different stages in the drying process of a colloidal thin film. We show that we can access ensemble averaged dynamic properties on length scales as small as ten micrometers over the full field of view.