Invented water-repellent (superhydrophobic) glass

Water droplets on the surface of the new material

The eye of the moth and the lotus leaf became prototypes for the invention of American chemists - the antireflection, water repellent (i.e., superhydrophobic) glass coating. Such glass never mists up and remains crystal clear even in fog. And the moisture that flows and flies away takes all the trash and dust particles with it.

The discovery has the potential for a huge number of applications: windows, solar panels, sensors, weapon systems, glasses, lenses and many other products.

The material was invented by chemists from the Oak Ridge National Laboratory, and details are provided by the scientific article "Monolithic Graded-Refractive-Index Glass-Based Antireflective Coatings: Broadband / Omnidirectional Light Harvesting and Self-Cleaning Characteristics" in the Journal of Materials Chemistry C, 2015. ( copy ).
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The material is a mechanically stable nanostructured layer of porous glass film. In fact, it combines the water-repellent properties of the lotus leaf and the anti-glare properties of the moth's eye. In both cases, the properties are explained by the tiny irregularities of the surface of the nanoscale.

In order to repel water, the wetting angle (contact angle) must exceed 150 °. In a new coating, the wetting angle ranges from 155 ° to 165 °, so that water droplets literally bounce off of it, taking dirt and dust with it.


Schematic representation of the new coverage and its applications

In the scientific work describes the process of making film coating of the base material. As a base material, a special type of glass coating is also used, which has high strength. This is different from other similar materials, say the authors of the scientific work. Strength is maintained after heat treatment. The new coating is very resistant to abrasion and can withstand temperatures up to 500 ° C.

Actually, the entire manufacturing process consists of three stages: depositing a thin layer of glass material on a glass substrate, heat treatment and selective removal of material using etching. The result is a porous three-dimensional structure resembling microscopic coral.



Such a coating can be made on existing production facilities, using standard methods, without much difficulty and quite cheaply, the authors say.

By the way, the anti-reflective coating strongly suppresses Fresnel reflections, immediately increasing the efficiency of solar panels by 3-6%. Automatic dusting will also add to their efficiency.