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Tuesday, October 9, 2012

Splitting water

Ever wish you could split a drop of water cleanly in two? Well, thanks to the advances of Ryan Yanashima and his colleagues from Arizona State University, that dream may now be a reality.

Ordinarily, if you try to cut a water droplet precisely in half, the original drop shatters into multiple, and often unusable, droplets. However, if you make your knife ‘superhydrophobic’, meaning that water can’t stand to touch it, the droplet will slice cleanly in two. To create these water-hating knives, the researchers began with polyethylene knives and then attached hydrophobic solvents in a several step procedure. You can see the result below.

This just leaves one question: why would you need to chop a water drop in half? There are actually a lot of medical and industrial uses. The important difference between this method and shattering a drop is that by slicing the droplet in half you don’t lose any volume. Remember, anything in the droplet (dissolved medicines, solvents, proteins, etc) will also be divided. Not only the water, but also your valuable ingredients are lost in the satellite droplets you create by fragmenting a drop of your favorite solution. In contrast, you save every bit of material by slicing your water.

Ryan Yanashima, Antonio A. GarcĂ­a, James Aldridge, Noah Weiss, Mark A. Hayes, & James H. Andrews (2012). Cutting a Drop of Water Pinned by Wire Loops Using a Superhydrophobic Surface and Knife PLoS ONE : doi:10.1371/journal.pone.0045893