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A Few Nanoparticles Let You Boil Water Using Just The Sun

A solution to sterilizing water and medical devices in places where heating lots of water can be difficult, this new breakthrough in nanotechnology means that boiled water is available anywhere there is sunlight.

A watched pot never boils. If you add nano-particles and sunlight, however, you only have to wait a few seconds.

Researchers at Rice University have discovered a way to create steam by boiling water using just sunlight, even if the water is ice cold. The phenomenon works by mixing water with tiny carbon or metal particles, smaller than a wavelength of light, that absorb and radiate the sun’s energy as heat. Since the particles have such a tiny surface area, heat is concentrated on its surface, which creates a vapor bubble—and thus steam. Traditionally, all of the water in container would have to reach a high temperature before it started boiling. This new approach means just a tiny fraction of the water must be heated, so even sunlight can deliver enough energy. It’s a radically new way to think about boiling water.

"We’re going from heating water on the macro scale to heating it at the nanoscale," said Naomi Halas, the lead scientist on the project in a statement by Rice University. "This intense heating allows us to generate steam locally, right at the surface of the particle."

Solar steam’s unique properties means the concept could sterilize drinking water or surgical instruments in remote areas using sunshine and little else. Engineering undergraduates at Rice have already built their first solar-powered steam autoclave while Halas is working on an "ultra-small-scale system for treating human waste in areas without sewer systems or electricity," which was recently recognized by the Bill and Melinda Gates Foundation.

Further applications are still being explored. Steam generated power—the source of about 90% of the world’s electricity—is one contender (although the lower pressure steam from this process has less energy to spin turbines) as well as medical applications where tumors and other tissues treated with nanoparticles can be selectively "boiled" using focused light.

"Solar steam" is just one of the new advances courtesy of nanotechnology, science and engineering at the scale of 1 to 100 nanometers, or about 100,000 times smaller than the width of a sheet of paper. As tools to manipulate matter at the scale of atoms improves, a slew of new technologies should emerge as we learn to see the world from different perspective.

"We’re not changing any of the laws of thermodynamics," Halas says. "We’re just boiling water in a radically different way."