Scientists at the University of Rochester have used lasers to transform metals into extremely water repellent, or super-hydrophobic, materials without the need for temporary coatings.

University of Rochester’s Institute of Optics Professor Chunlei Guo has developed a technique that uses lasers to render materials hydrophobic, illustrated in this image of a water droplet bouncing off a treated sample. Credit: J. Adam Fenster/University of Rochester

Super-hydrophobic materials are desirable for a number of applications such as rust prevention, anti-icing, or even in sanitation uses. However, as Rochester’s Chunlei Guo explains, most current hydrophobic materials rely on chemical coatings.

In a paper published today in the Journal of Applied Physics, Guo and his colleague at the University’s Institute of Optics, Anatoliy Vorobyev, describe a powerful and precise laser-patterning technique that creates an intricate pattern of micro- and nanoscale structures to give the metals their new properties. This work builds on earlier research by the team in which they used a similar laser-patterning technique that turned metals black. Guo states that using this technique they can create multifunctional surfaces that are not only super-hydrophobic but also highly-absorbent optically. Read more

In June the state of Florida made an unusual announcement: it would sue the U.S. Army Corps of Engineers over the corps’s plan to reduce water flow from reservoirs in Georgia into the Apalachicola River, which runs through Florida from the Georgia-Alabama border.

Water is needed to generate energy. Energy is needed to deliver water. Both resources are limiting the other—and both may be running short. Is there a way out?

Florida was concerned that the restricted flow would threaten certain endangered species. Alabama also objected, worried about another species: nuclear power plants, which use enormous quantities of water, usually drawn from rivers and lakes, to cool their big reactors. The reduced flow raised the specter that the Farley Nuclear Plant near Dothan, Ala., would need to shut down.

Georgia wanted to keep its water for good reason: a year earlier various rivers dropped so low that the drought-stricken state was within a few weeks of shutting down its own nuclear plants. Conditions had become so dire that by this past January one of the state’s legislators suggested that Georgia move its upper border a mile farther north to annex freshwater resources in Tennessee, pointing to an allegedly faulty border survey from 1818. Read more

Chuck Wight, a chemistry professor at the University of Utah, provides the following explanation:A typical water-softening system removes calcium and magnesium ions from hard water and replaces them with sodium ions. Calcium and magnesium ions interfere with the action of household soaps and detergents, but sodium does not.

The water-softening process thus helps detergents to more effectively remove dirt and oils from clothing and dishes. It also helps soaps to give a “slippery” feel to your skin when you wash. Most manufacturers of water softeners recommend that you reduce the amount of soap and detergents you use after installing a water softener. Read more

We hear every day about the need to conserve freshwater. That goal seems sensible—although knowing if humankind is making any progress could be impossible without a reliable way to quantify how much water nations use.

To find out, engineers Arjen Hoekstra and Mesfin Mekonnen at the University of Twente in the Netherlands calculated the water footprint of the world’s countries as well as per capita water consumption in those nations.

Overall, the world is using 9,087 billion cubic meters of water per year. China, India and the U.S. consumed the highest annual totals: 1,207 billion, 1,182 billion and 1,053 billion cubic meters, respectively, followed by Brazil at 482 billion. But the water consumed per person in these and other countries varies considerably, due primarily to higher living standards or widespread waste among consumers. The U.S. had the world’s highest per capita water footprint, at 2,842 cubic meters per annum. Read more