Shock waves in capillary collapse of colloids: a model system for two--dimensional screened Newtonian gravity

TL;DR

This study models the collapse of colloidal particles driven by capillary attraction, revealing a ringlike density peak and shock wave behavior, with implications for understanding two-dimensional screened Newtonian gravity analogs.

Contribution

It introduces a combined simulation, theoretical, and analytical approach to study capillary-driven collapse, highlighting the formation of shock waves and density peaks in a colloidal system.

Findings

Ringlike density peak at the patch rim

Inbound shock wave propagating inward

Theoretical predictions match simulation results

Abstract

Using Brownian dynamics simulations, density functional theory, and analytical perturbation theory we study the collapse of a patch of interfacially trapped, micrometer-sized colloidal particles, driven by long-ranged capillary attraction. This attraction {is formally analogous} to two--dimensional (2D) screened Newtonian gravity with the capillary length \hat{\lambda} as the screening length. Whereas the limit \hat{\lambda} \to \infty corresponds to the global collapse of a self--gravitating fluid, for finite \hat{\lambda} we predict theoretically and observe in simulations a ringlike density peak at the outer rim of a disclike patch, moving as an inbound shock wave. Possible experimental realizations are discussed.