Hidden Structural Control of Solvent Transport under Soft Jamming

TL;DR

This study reveals that solvent transport in soft jammed materials like foams is governed by the mechanical response of the structure, challenging the traditional capillary-driven models especially in different boundary conditions.

Contribution

It demonstrates the influence of structural mechanics on solvent transport in jammed systems, highlighting boundary-dependent effects overlooked by classical capillary theories.

Findings

Transport slows down in closed systems due to structural resistance.

In open systems, collective bubble motion accelerates solvent invasion.

Transport behavior is controlled by boundary conditions and structural coupling.

Abstract

Transport in soft jammed materials is often described as fluid motion through a fixed structure, leading naturally to capillary based descriptions. This picture appears particularly appropriate in strongly jammed systems, where structural rearrangements are suppressed and little visible motion is observed. Here we investigate solvent transport in foam and show that this intuition fails to capture key aspects of the transport process. By directly observing both liquid penetration and bubble motion under controlled boundary conditions, we demonstrate that solvent transport is strongly influenced by the mechanical response of the foam structure, even though the intrinsic imbibition relative to the foam matrix remains purely capillary-driven. In closed systems, the jammed structure resists penetration and leads to a pronounced slowdown that cannot be accounted for by purely capillary descriptions. In contrast, in open systems, collective bubble motion accompanies solvent invasion, resulting in an apparent acceleration of transport. These results indicate that the lack of structural motion does not guarantee a purely capillary description of transport. Our findings reveal a boundary controlled coupling between flow and structure, and highlight the need to reconsider transport processes in soft jammed systems, including foams, dense colloids, and biological tissues.