Dynamics of colloidal aggregation in microgravity by critical Casimir forces

TL;DR

This study investigates how critical Casimir forces influence colloidal aggregation in microgravity, revealing how aggregate structure varies with interaction strength through combined static and dynamic scattering measurements.

Contribution

It introduces a method to analyze aggregate internal structure in microgravity by measuring static and dynamic structure factors simultaneously.

Findings

Mass distribution is uniform across aggregates.

Fractal dimension decreases with increasing interaction strength.

Internal structure varies systematically with potential depth.

Abstract

Using the critical Casimir force, we study the attractive-strength dependence of diffusion-limited colloidal aggregation in microgravity. By means of near field scattering we measure both the static and dynamic structure factor of the aggregates as the aggregation process evolves. The simultaneous measurement of both the static and dynamic structure factor under ideal microgravity conditions allows us to uniquely determine the ratio of the hydrodynamic and gyration radius as a function of the fractal dimension of the aggregate, enabling us to elucidate the internal structure of the aggregates as a function of the interaction potential. We find that the mass is evenly distributed in all objects with fractal dimension ranging from 2.55 for a shallow to 1.75 for the deepest potential.