Superhydrophobic surfaces were an instant hit in the scientific community when they were introduced over two decades ago. Since then thousands of publications have documented superhydrophobicity being achieved on various different substrates, from glass to fabrics.
The great potential of superhydrophobic surfaces was apparent early on. Applications ranging from self-cleaning windows to anti-acing surfaces and non-wetting fabrics appear commonly in the literature.However, it can be argued that superhydrophobic surfaces have not really delivered on their promise since not many commercial applications are currently available.
By far the biggest obstacle towards real life applications is the durability of the superhydrophobic surface. If we consider how superhydrophobicity is achieved, the reasons for poor durability are quite obvious. Essentially, superhydrophobicity requires two things:
Hydrophobic (non-polar) surface chemistry
Micro- or nanostructured surface texture
A primary approach for the fabrication of superhydrophobic surfaces is based on patterning roughness on a solid substrate. As the solid substrate is usually hydrophilic by nature, a hydrophobic coating is then applied to achieve superhydrophobicity. Coatings are however prone to degradation caused by mechanical wear, UV radiation or abrasive particles. Micro- and nanostructures are also affected by the mechanical wear. If the hydrophobic coating is deteriorated or the surface texture is lost, the superhydrophobic properties are diminished.
During the last decade or so, increasing attention has been given also to the durability of the superhydrophobic coatings. It has become evident that no matter how impressive the properties achieved, if these properties are not durable, they are of no use in long term applications. Also the need to be able to compare the durability of different coatings is recognized. This can only be achieved by standardized testing methods for both durability testing as well as evaluation of the wetting properties.
For more information on how the durability of the superhydrophobic surfaces can be evaluated please attend the webinar given by Robin Ras.