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Motor Made From Liquid Film 241

KentuckyFC writes "Last year, a group of Iranian physicists made a puzzling discovery. They placed a thin film of water in a small cell and bathed it in two perpendicular electric fields. To their surprise this caused the water to rotate. They called their device a liquid film motor and posted on the web a cool set of movies showing the phenomenon. The puzzle is this: the electric fields are static, so what's driving the motor? Now another group of physicists has the answer: a complex interaction between the electric field, the cell container and the liquid causes water to move along the cell wall. Crucially, it moves in opposite directions on opposite sides of the cell and so sets up a circular flow. The phenomenon works only when friction and surface tension are significant forces so the effect is entirely scale dependent. That's probably why we haven't seen it before and also why it could have important implications for microfluidic devices such as lab-on-a-chip."

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