# gst: attraction-enhanced emergence of friction (in colloidal matter)

<< How frictional effects emerge at the microscopic level in particulate materials remains a challenging question, particularly in systems subject to thermal fluctuations due to the transient nature of interparticle contacts. >>

Here, AA << directly relate particle-level frictional arrest to local coordination in an attractive colloidal model system. (They) reveal that the orientational dynamics of particles slows down exponentially with increasing coordination number due to the emergence of frictional interactions, the strength of which can be tuned simply by varying the attraction strength. Using a simple computer simulation model, (they) uncover how the interparticle interactions govern the formation of frictional contacts between particles. >>

AA << results establish quantitative relations between friction, coordination, and interparticle interactions. This is a key step toward using interparticle friction to tune the mechanical properties of particulate materials. >>️

<< Importantly, almost all theoretical and simulation studies on such systems do not account for interparticle friction. Incorporating frictional constraints to rolling and sliding between particles will likely have a pronounced effect on a variety of phenomena studied in attractive colloidal matter such as gel formation, coarsening and failure. >>

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Berend van der Meer, Taiki Yanagishima, Roel P. A. Dullens. Attraction-Enhanced Emergence of Friction in Colloidal Matter. Phys. Rev. Lett. 134, 078202. Feb 21, 2025. 

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.078202

Also: particle, colloids, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, particles, colloids, friction, coordination,  interparticle friction, interparticle interactions

# gst: friction-induced bubble edge curvature in flowing 2D confined foams

AA << investigate the flow of quasi-2D liquid foams, composed of a single monolayer of bubbles in close contact and confined between two glass plates in a Hele-Shaw cell, with a specific emphasis on understanding how bubble shapes evolve in response to varying flow speeds. Utilizing an experimental setup capable of displacing a substantial number of bubbles in the spanwise direction, while the bubble shapes remain stationary as the bubbles themselves are advected in a plug flow, (They) reveal an average bubble anisotropy characterized by elongated bubbles in the streamwise direction and curved bubble edges in a preferential orientation. >>

<< Notably, these effects intensify with increasing flow speeds. While the bubble anisotropy is created at the entrance of the cell, (AA) study establishes a clear connection between bubble edge curvature and orientation, confinement thickness, frictional forces with the plates, and the inherent anisotropy of the bubbles. >>

Christophe Raufaste, Lauren Rose, et al. Friction-induced bubble edge curvature in flowing two-dimensional confined foams. Phys. Rev. Fluids 10, 023301. Feb 5, 2025. 

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.10.023301 

Also: bubble, foam, in https://www.inkgmr.net/kwrds.html 

Keywords: gst, bubble, foam, friction, surface tension

# gst: substrate friction and geometric confinement could act as transitional control parms (in active nematics).

<< Using a minimal continuum model, (AA) investigate the interplay between circular confinement and substrate friction in active nematics. Upon increasing the friction from low to high, (They) observe a dynamical phase transition from a circulating flow phase to an anisotropic flow phase in which the flow tends to align perpendicular to the nematic director at the boundary. (AA) demonstrate that both the flow structure and dynamic correlations in the latter phase differ from those of an unconfined, active turbulent system and may be controlled by the prescribed nematic boundary conditions. (AA) results show that substrate friction and geometric confinement act as valuable control parameters in active nematics. >> 

Cody D. Schimming, C. J. O. Reichhardt, C. Reichhardt. Friction-mediated phase transition in confined active nematics. Phys. Rev. E 108, L012602. Jul 27, 2023. 

https://journals.aps.org/pre/abstract/10.1103/PhysRevE.108.L012602 

https://twitter.com/PhysRevE/status/1684921441651691520

Also: transition, in https://www.inkgmr.net/kwrds.html

Keywords: gst, transition, friction, friction-mediated phase transition, confinement, nematics