Interactions and pattern formation in a macroscopic magnetocapillary SALR system of mermaid cereal
Résumé
When particles are deposited at a fluid interface they tend to aggregate by capillary attraction to minimize the overall potential energy of the system. In this work, we embed floating millimetric disks with permanent magnets to introduce a competing repulsion effect and study their pattern formation in equilibrium. The pairwise energy landscape of two disks is described by a short-range attraction and long-range repulsion (SALR) interaction potential, previously documented in a number of microscopic condensed matter systems. Such competing interactions enable a variety of pairwise equilibrium states, including the possibility of a local minimum energy corresponding to a finite disk spacing. Two-dimensional (2D) experiments and simulations in confined geometries demonstrate that as the areal packing fraction is increased, the dilute repulsion-dominated lattice state becomes unstable to the spontaneous formation of localized clusters, which eventually merge into a system-spanning striped pattern. Finally, we demonstrate that the equilibrium pattern can be externally manipulated by the application of a supplemental vertical magnetic force that remotely enhances the effective capillary attraction. Particles at fluid interfaces aggregate due to capillary attraction, but introducing magnets creates a competing repulsion effect, influencing pattern formation. Authors report how short-range attraction and long-range repulsion interactions govern the transition from repulsive lattices to clustered and striped patterns as particle density increases.
Domaines
Physique [physics]Origine | Fichiers éditeurs autorisés sur une archive ouverte |
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