As the weather turns spring-like, winter's ice build-up on power lines, windshields, and airplane wings becomes a fading memory. Professor Victor Petrenko, of Thayer School of Engineering at Dartmouth College (Dartmouth, NH), hopes to keep it that way. The physicist discovered that applying a small electric voltage across an ice-metal interface can break the bond between ice and metal surfaces. Technically, Petrenko says, ice is a semiconductor--included in a small class of substances in which protons, rather than electrons, carry an electrical current. When an electrically-charged surface comes into contact with any other surface, the charged surface induces an opposite charge in the facing surface and, because opposites attract, the two surfaces are drawn together. "This simple attraction accounts for most of ice adhesion," says Petrenko. Breaking the bond between ice and metal, he reasoned, should be as simple as neutralizing the surface charge with an equal amount of its opposite. He tested his theory using a sheet of ice, a globule of mercury--which stays liquid until temperatures dip below -40F--and a small battery with two wires attached. He touched one wire to the ice, the other to the mercury. The mercury drew itself up and away from the ice. Petrenko repeated the experiment using steel and other solid metals. In each case, the electricity caused the ice to lose adhesion. The effect could also be reversed, causing a surface to stick more firmly to the ice. "It may be possible to prevent or significantly reduce icing on the wings of an airplane using a battery no bigger than the one in your car," Petrenko theorizes. Surface-to-surface interactions are also important in manufacturing and machinery. Call: (603) 646-2117.
During a teardown of the iPad Air and Microsoft Surface Pro 3 at the Medical Design & Manufacturing Show in Schaumburg, Ill., an engineer showed this "inflammatory" video about the dangers of maliciously mishandling lithium-ion batteries.
Science fiction author Isaac Asimov may have the best rules for effective brainstorming and creativity. His never-before-published essay, "On Creativity," recently made it to the Web pages of MIT Technology Review.
Much has been made over the potentially dangerous flammability of lithium-ion batteries after major companies like Boeing, Sony, and Tesla have grappled with well-publicized battery fires. Researchers at Stanford University may have come up with a solution to this problem with a smart sensor for lithium-ion batteries that provides a warning if the battery is about to overheat or catch fire.
In this new Design News feature, "How it Works," we’re starting off by examining the inner workings of the electronic cigarette. While e-cigarettes seemed like a gimmick just two or three years ago, they’re catching fire -- so to speak. Sales topped $1 billion last year and are set to hit $10 billion by 2017. Cigarette companies are fighting back by buying up e-cigarette manufacturers.
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