Boat made from a sieve

15 March 2009
Posted by Chris Smith.

Edward Lear famously wrote about sending the Jumblies to sea in a sieve and many warned they would drown, but perhaps not if they were aboard a miniature boat made by Chinese scientists Qinmin Pan and Min Wang.

This is a sieve (also known as a strainer).The two scientists based at Herbin Institute of Technology describe in the current edition of the ACS journal Applied Materials and Interfaces, how they have produced a water-repelling surface so powerful that a fine copper meshwork bent into a simple boat-shape will float on a bath of water, even when laden with sand "cargo".

The trick relies on chemically cleaning the copper surface and then "functionalising it" by dunking it in a silver solution and then a solution of dodecanoate, a fatty acid.  Studying the treated copper meshwork under an electron microscope reveals that the silver form a system of very fine dendrites (branches) like the leaves of a miniature fern.  The ends of these silver branches become decorated with the dodecanoate, which repels water and traps a layer of air against the mesh,rendering it water-tight.

The researchers admit that scaling the technique up to full-sized boats is probably not practical, but they suggest that this trick could be used for purposes such as underwater robots and underwater surveillance.  The air-film trapped against the mesh, they say, can also dramatically reduce the drag on the hull of their "boat" and so could be used in drag-cutting devices (and that's drag as in resistance, rather than Edna Everage...).

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