Squaring the spheres

Hexagonal packing is common as it represents the bottom of the energy curve when packing spheres together, so to speak, but researchers at Wageningen University in The Netherlands have shown how square packing can occur when colloidal spheres are spread on an anisotopric curved oil-water interface because of capillary actions that would on a larger scale cause clumping, akin to that seen with pieces of breakfast cereal forming clumps on the surface of milk in the bowl. The discovery has implications, not for the breakfast table, but for controlling the self-assembly of microscopic and sub-microscopic structures.