Nanotechnology paper for switchable surfaces
Generally, a surface either loves a liquid drop (then it’s called solvophilic - wetting) or hates it (called solvophobic - repulsion) when it lands, depending on several parameters of both the surface - like geometric roughness asperities or ups and downs and chemical composition - and the liquid - like surface tension or tendency of solvation. When water is the liquid the terms hydrophilic and hydrophobic are used respectively for this and for oil similar terms like oleophilic and oleophobic. Advanced material engineering techniques can structure surfaces that allow dynamic tuning of their wettability all the way from superhydrophobic behavior to almost complete wetting - but these surfaces so far only work with high-surface-tension liquids. Just recently, researchers in India have developed a superhydrophobic (where the contact angle between the droplet and the surface is approaching 180 degrees) carbon nanotube (CNT) ‘bucky paper’ that shows fascinating wetting behavior as a result of an applied electric field, which could be remarkably tuned by changing key solution variables like ionic strength, nature of electrolyte, and pH of the droplet.
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This post was written by admin on August 19, 2008
