“Keep cool to reduce friction” might be the advice given to designers of nanoscale machinery by researchers who have just completed a study of factors influencing the formation of “water bridges” – capillary connections that can glue surfaces together, giving rise to friction forces.
When surfaces touch in a humid environment, moisture forms water bridges, or capillaries, between them. On familiar size scales, this process – known as nucleation – helps hold sand castles and wet concrete together, and is critical to the formation of clouds. But sometimes these structures can be less helpful, causing friction sufficient to slow or even stop nanoscale machinery – or in food processing, creating large clusters of sugar, salt, baby cereals or coffee.
By studying the frictional forces acting on an atomic force microscope (AFM) tip drawn across a glass surface, researchers at the Georgia Institute of Technology have demonstrated for the first time that the formation of these capillaries is thermally activated. Their study suggests that it may be possible to reduce the adhesion between surfaces by reducing temperatures and putting nanoscale surfaces into motion before the water bridges have time to form.
John Toon | EurekAlert!
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