FOR anyone (and that is almost everyone) who has shaken and thumped a bottle of ketchup to squeeze the last dollop out of it, or flattened and then rolled up a tube of toothpaste to eject one final squirt onto their brush, help may soon be at hand. For more than a decade Kripa Varanasi and his colleagues at the Massachusetts Institute of Technology (MIT) have been creating and studying slippery surfaces for use in industrial equipment such as steam turbines and desalination plants.
More recently, they have found ways to apply their ideas to create internal coatings for containers so that their contents will flow out easily and completely, with no shaking, thumping or squeezing. And now they think they have discovered a way to adapt these super-slippery coatings to steer liquids across flat surfaces, opening up the possibility of pumping fluids around without the need for pipes.
The lotus position
Dr Varanasi’s work started with what are known as super-hydrophobic water-shedding surfaces, a classic natural example of which is a lotus leaf. It repels water so effectively that droplets simply tumble off. The reason is that the leaf’s surface is covered with microscopic structures which contain air pockets. This reduces the surface tension that would otherwise cause a water droplet to cling on. By coating the condensing areas used in…Continue reading
Source: New feed