This IRG-1 collaboration, is focused on the mechanics of disordered solid granular matter and is led by Arratia, Ma (post-doc, Yodh lab) and Jerolmack (MRSEC collaborator). This work discovered that stable particle aggregates can be formed by a continuous wetting and evaporation process via formation of solid bridges: particle strands that connect larger aggregates. These strands can increase the strength (bonding) of particle aggregates by an order of magnitude or more. AFM measurements revealed that monodisperse aggregates are weaker than polydisperse ones. Interestingly, particles segregate by size during the evaporation process due to capillary forces to form self-similar, fractal structures (bottom panel) across three orders of magnitude in length scale. The results elucidate novel origins of cohesion in granular matter and improve our understanding of the mechanics of particulate materials with applications ranging from landslides to pharmaceuticals.
Figure top: Evaporation of a bidisperse suspension, figure bottom: monodisperse aggregates are weaker than polydisperse ones, highlighting the effects of particle size dispersivity. Interestingly, particles segregate by size during the evaporation process due to capillary forces to form remarkable self-similar, fractal structures
1Seiphoori, A., Ma, X-G, Arratia, P.E., Jerolmack, D., Formation of stable aggregates by fluid-assembled solid bridges, Proceedings of the National Academy of Sciences (PNAS), 117, 3375-3381(2020