Physics and applications of superhydrophobic and superhydrophilic surfaces and coatings

The terms superhydrophobicity and superhydrophilicity were introduced not very long ago, in 1996 and 2000, respectively. The former is used to describe exceptionally weak and the latter used to indicate strong interactions of materials and coatings with bulk water, controlled entirely by surface topography and material chemistry. An explosion of research on fabrication of superhydrophobic and superhydrophilic surfaces and coatings was noticed almost immediately after the concepts appeared in the technical literature, with hundreds of reports now published annually. The interest in this new class of surfaces/coatings is driven by an emerging market for water-repellant, snow- and ice-phobic products and formulations, water antifogging screens, windows and lenses, antifouling coatings, microfluidic devices, coatings for enhanced boiling heat transfer, foils for food packaging and many other products. The popularity of this emerging subdiscipline of surface chemistry can also be attributed to uncomplicated fabrication technologies that can produce superhydrophobic or superhydrophilic surfaces and coatings, in addition to the simplicity of the testing techniques used, such as contact angle measurements. In this article, the physics behind superhydrophobic and superhydrophilic effects are reviewed and several examples of applications of superhydrophobic and superhydrophilic surfaces and coatings are provided.