Critical-like behavior in foam dynamics: Transition from slip to scraping

Jamming systems, including colloids, emulsions, foams, and biological tissues, undergo significant deformation during processes like 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. Notably, the transition from slip to scraping when foam is manipulated using a rigid plate remains poorly understood. Systematic observations of the internal foam structure during scraping were conducted, and the scraping length was qualitatively analyzed by varying the scraping velocity. Our study reveals that the transition from slip to scraping is driven by the sequential propagation of bubble rearrangements. Furthermore, the scraping length diverges towards the transition point, with a critical exponent of approximately 0.61. These findings align with directional percolation theory, underscoring the robustness of the theoretical framework. This study offers a comprehensive understanding of the macroscopic kinetics and rheological behaviors in jamming systems, with implications for applications in materials science, food processing, and biological systems.