Cotton for filtersCourtesy Martin Labar

Safe drinking water saves lives

Clean, safe drinking is desperately needed throughout the world. Usually filters "filter out" bacteria by having openings too small to get through. Trouble is, though, that the tiny holes get plugged up, stopping the flow of water. Stanford researchers have now developed a filter about 80,000 times faster than filters that trap bacteria.

Cheap and easy

The filter was made by dipping plain cotton cloth (from Walmart) in a mixture of silver nanowires and carbon nanotubes (for a few minutes). By charging the filter with 20 volts of electricity, over 98 percent of Escherichia coli bacteria were killed as they passed through. Even in remote or primitive areas, the electricity could be supplied by a small solar panel, or a couple 12-volt car batteries, or be generated from a stationary bicycle or by a hand-cranked device.

Cui said the next steps in the research are to try the filter on different types of bacteria and to run tests using several successive filters.
"With one filter, we can kill 98 percent of the bacteria," Cui said. "For drinking water, you don't want any live bacteria in the water, so we will have to use multiple filter stages."

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High-speed filter uses electrified nanostructures to purify water at low cost Stanford University News