Bubble raft

It demonstrates materials' microstructural and atomic length-scale behavior by modelling the {111} plane of a close-packed crystal.

A material's observable and measurable mechanical properties strongly depend on its atomic and microstructural configuration and characteristics.

This fact is intentionally ignored in continuum mechanics, which assumes a material to have no underlying microstructure and be uniform and semi-infinite throughout.

These assembled bubbles act like atoms, diffusing, slipping, ripening, straining, and otherwise deforming in a way that models the behavior of the {111} plane of a close-packed crystal.

The ideal (lowest energy) state of the assembly would undoubtedly be a perfectly regular single crystal, but just as in metals, the bubbles often form defects, grain boundaries, and multiple crystals.

The concept of bubble raft modelling was first presented in 1947 by Nobel Laureate Sir William Lawrence Bragg and John Nye of Cambridge University's Cavendish Laboratory in Proceedings of the Royal Society A.

[1] Legend claims that Bragg conceived of bubble raft models while pouring oil into his lawn mower.

He noticed that bubbles on the surface of the oil assembled into rafts resembling the {111} plane of close-packed crystals.

[2] Nye and Bragg later presented a method of generating and controlling bubbles on the surface of a glycerine-water-oleic acid-triethanolamine solution, in assemblies of 100,000 or more sub-millimeter sized bubbles.

In their paper, they go on at length about the microstructural phenomena observed in bubble rafts and hypothesized in metals.

[1] Bubble rafts exhibit complex dynamics, as illustrated in the video.

This is triggered by rupture of a first bubble, driven by thermal fluctuations[3] and a cascade of subsequent bursting bubbles, which can give rise to self-organized criticality, and a power-law distribution of avalanches.

The "atoms" in Bubble Rafts also exhibit such attractive and repulsive forces:[2]

[2] Bubble rafts can display numerous phenomena seen in the crystal lattice.

This includes such things as point defects (vacancies, substitutional impurities, interstitial atoms), edge dislocations and grains.

A screw dislocation can't be modeled in a 2D bubble raft because it extends outside the plane.

The annealing process is simulated by stirring the bubble raft.