Sheets of large superhydrophobic metal particles self assembled on water by the Cheerios effect

Abstract

Surface tension in water gives rise to a variety of phenomena some of which, such as the rise of water inside hydrophilic tubes under capillary action or the ability of pond skaters to walk on the surface of water, are so familiar that they seldom excite comment. However, there is still potential for new insights and discoveries to be made in this area. Two recent examples are the discovery that liquid marbles can be prepared by coating solvent droplets with powder and the elucidation of a general mechanism for the attraction of buoyant objects in liquids, the Cheerios effect . Here we report a method for preparing large (up to 0.4 mm diameter) superhydrophobic copper particles and show that these particles, which have extraordinarily large contact angles but are much denser than water, give rise to a range of striking effects, including the ability to self assemble into sheets which can support objects that normally sink in water.