Practical Applications of Superhydrophobic Materials and Coatings: Problems and Perspectives.
Synthetic superhydrophobic (SH) surfaces were developed after 1990s and the number of publications in this field is around 13.500 at present. However, the industrial production of the SH coatings is very unsatisfying after the intensive research activity especially in the last two decades. The main reason is the loss of the water repellence properties when SH surfaces are exposed to outdoor conditions due to their weak mechanical properties and contamination from the medium which remove the initial SH properties. In this Feature Article, we focus on the scientific and technical reasons which prevent the application of the SH surfaces in our daily lives by highlighting some well known, but mostly overlooked problems in this area (the synthesis methods of SH surfaces is not the subject of this article since they were reviewed previously in very good articles) The basic contact angle science and the issue of the cancellation of the Wenzel and Cassie Baxter equations are reviewed in the first part. The issues of the expensive and small scale SH surface preparation problems, the difficulties to obtain a transparent SH surface, the troubles arising from the water vapor condensation on a SH surface, the lack of robustness and abrasion resistance of most of the SH surfaces, the drawbacks of the fabricated self healing SH surfaces, the short useful service life of self cleaning SH surfaces due to the surface contamination and the ineffective anti icing SH coatings are reviewed in the following parts. Some important problems affecting the unsuccessful industrial applications of the SH surfaces are discussed critically in the conclusions and outlook section. Finally, some proposals are presented for the future directions on the synthesis and application of SH surfaces.
Langmuir the ACS journal of surfaces and colloids