Translation. Region: Russian Federal
Source: Novosibirsk State University – Novosibirsk State University –
Superlyophobicity of laser-textured surfaces in rarefied atmosphere conditions was studied by a 4th-year student Faculty of Physics Novosibirsk State University Nikita Smirnov under the scientific supervision of Doctor of Physical and Mathematical Sciences, Senior Lecturer of the Department of General Physics of the Physics Faculty of NSU, Leading Researcher, Acting Head of Laboratory 10.1 of the S.S. Kutateladze Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences Sergey Starinsky. As part of his scientific work, the young researcher compared the indicators of the wetting properties of such surfaces with the data that were obtained under normal atmospheric conditions, and found that the differences between them are insignificant and in both cases the wettability of the surface under study is affected by the temperature factor.
Superlyophobicity is the property of a surface to repel liquid, forming almost spherical drops that do not spread but roll off it. This state of the surface is determined by such an indicator as the contact angle of wetting – the angle between the solid surface and the tangent to the liquid drop at the point of contact. In superlyophobic surfaces in a normal state without tilting, it exceeds 150°. Superlyophobicity can be achieved by creating structures on the surface that minimize the contact of liquid with the surface. This property of the surface can be useful in various applications where it is necessary to minimize its contact with liquids.
— It was important for us to study the superlyophobicity of laser-textured materials in a vacuum to test the classical Cassie-Baxter wetting theory, according to which these properties are achieved due to the air retained in the surface texture. And we had a question: what will happen if it is completely removed? Will the liquid flow into the structures or will the surface retain its water-repellent properties. The study of this problem is important and relevant, since the use of superlyophobic surfaces in airless space will solve a number of problems, for example, with icing, protection from condensation and corrosion of various space and suborbital vehicles. Such materials with a “water-repellent” structure have many areas of application. They can also be used in combustion physics. They can be in demand in the space industry – provided that they retain superlyophobicity in vacuum conditions. This is what we had to find out, — said Nikita Smirnov.
The young researcher turned to the literature on such studies of laser-textured surfaces in vacuum conditions and found only a few published scientific articles on this topic. The authors of only one of them managed to achieve water-repellent properties that would be fully preserved in vacuum conditions. At the same time, the reasons for this phenomenon were not studied in detail, and it was unknown what makes the main contribution to the preservation of these properties in a rarefied atmosphere. In his work, Nikita Smirnov proposed using superlyophobic surfaces with a developed structure, created using pulsed laser exposure and covered with a repellent fluoropolymer layer. This approach is easy to implement, since it is quite easy to reproduce the results obtained under known conditions and no special conditions are required for texturing. Another important advantage is the low cost of the technology, achieved due to the fact that in recent decades lasers have become more widespread and effective, and their use is widely used in various areas of production. It was proposed to spray the fluoropolymer coating in a thin layer so that the texture obtained by the laser would not change at the micron level, but would only be covered with a repellent layer. Nikita Smirnov decided to study the hydrodynamics of liquid droplets on superlyophobic surfaces inclined at a small angle (