Scientists design water controlling surfaces, according to news@nature and New Scientist, 30 August 2005.
Scientists at the Massachusetts Institute of Technology (MIT), Boston have developed a spongy surface coating that reduces reflections and prevents glass from fogging. The coating consists of layers of glass nanoparticles, polymer fibres, and air bubbles. This combination attracts water but breaks up droplets so that the water spreads through the spaces in the sponge. This results in the water forming a continuous film that does not scatter light. The nanoparticles are 7 nanometres in diameter, much smaller than the wavelengths of visible light. This makes the coating transparent and it reflects only 0.2% of light hitting the surface – a lot less than the 2-3% in current anti-reflective coatings.
The coating’s anti-fog properties come from the combination of fibres, nanoparticles and air bubbles. The fibres have a strong negative charge which attracts water molecules. The nanoparticles and air bubbles absorb the water like a sponge so that the water forms a continuous transparent film, rather than light scattering droplets.
Michael Rubner, who led the research has also used similar technology to develop coatings with the opposite effect, repelling water so that it forms droplets which grow until they roll off the surface. This makes the surface self-cleaning because the droplets carry dust and dirt with them as they roll away. Lotus leaves use this method to keep their leaves free of dust. Rubner commented that combinations of these two types of surfaces could be useful.
A beetle named Stenccara that lives in the Namib desert has water attracting and water repelling regions on its carapace. This enables it to attract water from the air, concentrate it and direct it to its mouth to drink. Rubner and his colleagues are hoping that car manufacturers and other industries that need fog-free, reflection-free glass or self cleaning surfaces will want to use the nanocoatings his team has developed.
Editorial Comment: The MIT scientists admit that what they have achieved already exists in leaves and beetles, but leaves and beetles are considered by most naturalistic evolutionists, to be the result of mindless natural processes. The water absorbing and repelling surfaces described above are the result of clever scientists applying their knowledge of physics, chemistry and the properties of materials to a problem. Leaving it to chance naturalistic or random processes would not have achieved anything. Therefore it is foolish to claim the water controlling surfaces found in living things are the result of mindless natural processes, when man made water controlling surfaces are the result of mindful creative design.
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