Physics News

Silver Nanowires A microscope image shows the silver nanowires in which the cotton cloth is dipped. Courtesy of Yi Cui, Stanford University Water, water everywhere, but in the developing world or in areas ravaged by natural disasters - like the ongoing flooding in Pakistan, for instance - there's often not a clean, purified drop to be found. Water is usually made potable in such places via filters that physically trap bacteria as water flows through, but researchers at Stanford have shown devised a high-speed filter composed of nothing but plain cotton cloth and nanotubes that can quickly filter nearly all bacteria from dirty water using less power than slower conventional water purifiers. Most water filters simply trap living bacteria as it passes through a series of tiny pores, a method that is effective but prone to a variety of problems. For one, they are painfully slow, and in disaster situations that can lead to critical shortages as thirsty populations wait for the water to trickle through. Further, t

"This really provides a new water treatment method to kill pathogens," said Yi Cui, an associate professor of materials science and engineering. "It can easily be used in remote areas where people don't have access to chemical treatments such as chlorine."
"Our filter is about 80,000 times faster than filters that trap bacteria," Cui said.
"In the days before pasteurization and refrigeration, people would sometimes drop silver dollars into milk bottles to combat bacteria, or even swallow it," Heilshorn said.
"This approach really takes silver out of the folk remedy realm and into a high-tech setting, where it is much more effective," Heilshorn said.
"With a continuous structure along the length, you can move the electrons very efficiently and really make the filter very conducting," he said. "That means the filter requires less voltage."