arXiv subjects

Masaya Endo

Publications and source records attributed to Masaya Endo.

3 recordsLinked to original sources

arXiv2026

Fluid-structure coupling governs a dynamic transition in foam scraping

Foam scraping exhibits a dynamic transition between a slip state, in which the foam moves beneath a plate, and a scraping state, in which the foam is expelled from the confined region. Although this transition has been associated with the propagation of local T1 rearrangements, the physical parameter controlling their propagation remains unclear. Here, we investigate the dependence of the critical scraping velocity on the liquid fraction, bulk viscosity, and surfactant system. For all examined conditions, the critical capillary number follows $\mathrm{Ca}_c\propto\phi^{-1}$, apart from a solution-dependent prefactor. We propose a local fluid--structure-coupling model in which viscous work transmitted through the Plateau-border network competes with the effective energetic cost required for one T1 event to trigger the next. The observed scaling implies an effective energetic cost governed by the Laplace pressure and is consistent with a small local compressive component of the bubble deformation. These results identify local coupling between interstitial flow and bubble deformation as a mechanism controlling the macroscopic slip--scraping transition.

cond-mat.soft↗

arXiv2025

Critical-like phenomenon in scraping of jamming systems

In jamming systems like colloids, emulsions, foams, and biological tissues, significant deformation is essential for processes such as material scraping or wound self-healing. To adequately spread a foam or cream over a surface, external force must be applied to artificially scrape it. The scraping of foam using a rigid plate has been observed to exhibit complex behavior distinct from that of simple liquids. In this study, we quantitatively analyzed the transition between partial and slender scraping regimes by examining changes in internal structure and partial spreading lengths. Our findings reveal that the sequential propagation of bubble rearrangement in the foam's internal structure leads to the partial scraping. Moreover, the scraping length in the partial scraping regime shows divergence near the transition point, characterized by a critical exponent of approximately 0.61. These results imply that foam scraping is governed by directional percolation theory, supported by the agreement between the experimentally observed critical exponent and theoretical predictions. This research significantly advances the understanding of macroscopic kinetics and rheological behavior in jamming systems, including foams, colloids, emulsions, and biological tissues.

cond-mat.soft↗

arXiv2023

Spreading of foam on a substrate

Foam is an industrially important form of matter, commonly deployed to clean objects and even our own skin, thanks to its ability to absorb oil and particles into its interior. To clean a large area, a foam is spread over a substrate, but the optimum conditions and mechanism have been unclear. Here, we study how a foam is spread by a rigid plate on a substrate as a function of spreading velocity, gap height, confinement length, amount of foam and wettability of the substrate. Three distinguishable spreading patterns were found: homogeneous spreading, non-spreading, and slender spreading. It is also found that the dynamics and the mechanism of the spreading can be explained by coupling among dewetting, anchoring, shear stress, viscous stress and yield stress. It is a unique feature of foams, which is not observed in simple liquids and then these findings are also critical for understanding the mechanical response of other soft jamming systems such as cells and emulsions.

cond-mat.soft↗