Capillary interactions between nearby interfacial objects Europhys. Lett. 102, 38001 (2013) PDF
by He, Nguyen and MandreFluid Mechanics Capillary Cheerios Effect
We develop a general method to study the capillary interactions between objects of arbitrary shape which float close to each other on an interface, a regime in which multipole expansion is not useful. The force is represented as a power series in the small distance between the objects, of which the leading order is finite. For objects with size a much larger than the capillary length lc, the force scales as (a/lc)1/2 and the prefactor depends on the mean radius of curvature R at the closest points. After contact the objects roll and/or slide with respect to each other to locally maximize R and therefore the force. For smaller objects (a < < lc), the force scales as (a/lc)-1/log(a/lc)2, and the prefactor depends only weakly on the shape and relative orientation of the objects.