Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
Nat Mater. 2012 Jan 22;11(3):217-22. doi: 10.1038/nmat3228.
We report that graphene coatings do not significantly disrupt the intrinsic wetting behaviour of surfaces for which surface-water interactions are dominated by van der Waals forces. Our contact angle measurements indicate that a graphene monolayer is wetting-transparent to copper, gold or silicon, but not glass, for which the wettability is dominated by short-range chemical bonding. With increasing number of graphene layers, the contact angle of water on copper gradually transitions towards the bulk graphite value, which is reached for ~6 graphene layers. Molecular dynamics simulations and theoretical predictions confirm our measurements and indicate that graphene's wetting transparency is related to its extreme thinness. We also show a 30-40% increase in condensation heat transfer on copper, as a result of the ability of the graphene coating to suppress copper oxidation without disrupting the intrinsic wettability of the surface. Such an ability to independently tune the properties of surfaces without disrupting their wetting response could have important implications in the design of conducting, conformal and impermeable surface coatings.
我们报告称，在表面-水相互作用主要由范德华力主导的情况下，石墨烯涂层不会显著改变表面的固有润湿性。我们的接触角测量表明，对于铜、金或硅等表面，单层石墨烯是润湿透明的，但对于玻璃则不是，因为玻璃的润湿性主要由短程化学键决定。随着石墨烯层数的增加，水在铜上的接触角逐渐向块状石墨的数值过渡，当达到约 6 层石墨烯时就会达到这个数值。分子动力学模拟和理论预测证实了我们的测量结果，并表明石墨烯的润湿性透明与其极度的薄度有关。我们还发现，由于石墨烯涂层能够抑制铜氧化而不破坏表面的固有润湿性，铜的冷凝传热增加了 30-40%。这种能够在不改变润湿性的情况下独立调节表面性能的能力，可能会对设计导电、共形和不可渗透的表面涂层产生重要影响。
