Graphene does not affect the wetting behaviour of several substrates, reports a study published online in Nature Materials this week. The ability to tune the electronic properties of surfaces without disrupting their wetting response should lead to superior conducting and superhydrophobic surface coatings. Graphene's two-dimensional chicken-wire atomic structure is known to be transparent to electrons and visible light. Now Nikhil Koratkar and colleagues show that the extreme thinness of graphene also makes it transparent to the intrinsic wetting behaviour of surfaces for which the wettability is dominated by the long-range van der Waals forces between atoms. The researchers measured the contact angle of water droplets on graphene-coated copper, gold and silicon surfaces, and found that the angle hardly changed from that for the respective bare surfaces. This was not the case for graphene-coated glass, for which the wettability is dominated by the relatively short-range chemical bonds. The authors also found that the contact angle shifted towards that for graphite when the surfaces were coated with an increasing number of graphene layers. The wetting transparency of conformal graphene coatings may enable novel applications in which electronic and wetting properties can be independently controlled.
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