Critical-like phenomenon in scraping of jamming systems

Abstract

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.