Structuring Colloidal Gels via Micro-Bubble Oscillations

TL;DR

This study uses Brownian dynamics simulations to explore how oscillating microbubbles can locally restructure colloidal gels, revealing hexagonal packing changes but not capturing long-range effects observed experimentally.

Contribution

The paper introduces a simulation approach to understand microbubble-induced restructuring in colloidal gels, highlighting the need to incorporate fluid flow effects for comprehensive modeling.

Findings

Hexagonal-close-packed restructuring observed at certain amplitudes

Simulations did not reproduce long-range structural modifications seen experimentally

Fluid flow effects are suggested for future modeling improvements

Abstract

Locally (re)structuring colloidal gels $\unicode{x2013}$ micron-sized particles forming a connected network with arrested dynamics $\unicode{x2013}$ enables precise tuning of the micromechanical and -rheological properties of the system. A recent experimental study [B. Saint-Michel, G. Petekidis, and V. Garbin, Soft Matter $\boldsymbol{18}$, 2092 (2022)] showed that rapid restructuring can occur by acoustically modulating an embedded microbubble. Here, we perform Brownian dynamics simulations to understand the mechanical effect of an oscillating microbubble on the structure of the embedding colloidal gel. Our simulations reveal a hexagonal-close-packed restructuring in a range that is comparable to the amplitude of the oscillations. However, we were unable to reproduce the unexpectedly long-ranged modification of the gel structure $\unicode{x2013}$ dozens of amplitudes $\unicode{x2013}$ observed in experiment. This suggests including long-ranged effects, such as fluid flow, should be considered in future work.