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Posted 11/18/02, by Catharine Lamm and Susan Knapp
Victor Petrenko's research team is out to break the ice
The words 'ice manipulation'may conjure up images of creating elaborate ice sculptures at Dartmouth Winter Carnival. However, for those who work with Victor Petrenko, Professor of Engineering at Dartmouth's Thayer School, it's a year-round task to figure out how best to control this wintery substance. Petrenko has made a career out of controlling ice. First, his research team looked for an easy way to effectively de-ice a surface, such as the wing of a plane, a car's windshield or a power line. His team's de-icing invention delivers a thin, even coating of low-voltage, high-frequency or single-pulsed electricity over an icy surface. This breaks the connection between the ice and the surface almost instantly and the ice falls away. (Vox covered this technology in the Jan. 15, 2001, issue.)
"These inventions have many applications," says Petrenko. "No more scraping windshields in the winter; no more power outages due to downed icy power lines; no more worrying about driving across a slippery bridge during a snowstorm."
Next the team wanted more control over the slippery/sticky essence of ice to, say, add a cruise control mechanism to skis. This challenge involved the ability to manipulate the friction that exists between the snow and the skis.
"We were thinking that if we can de-ice a plane, why can't we get better traction on ice, too," says Petrenko.
This new technology also employs low-voltage electricity, but the method of delivery is different. When a normal ski slides on ice or snow, only a fraction of the ski base actually touches because of small bumps and irregularities on the ice/snow surface. A low-frequency electric field, generated by a small battery, melts the irregularities, causing water to spread beneath the ski base and then refreeze to the ski within milliseconds. It's like when a wet, warm tongue freezes and sticks instantly to a metal flagpole. The melting and refreezing increases the contact area and creates a strong "stick-and-slip" phenomenon that literally makes the ski stick to the snow. Since only one side of the interface needs the electric field, this system can also be adapted to car tires and shoe soles.
For those skiers who want to go faster, a high-frequency electric field has the opposite effect as it melts snow and ice just enough to create the same thin, lubricating layer of water without the refreezing and sticking.
- Catharine Lamm and Susan Knapp
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