HOW do you get rid of energy-wasting burrs and crevices on microscopic cogs
and levers? In the everyday world, sandpaper smoothes things out, but
鈥渘anosandpaper鈥� doesn鈥檛 exist. Until now.
As with macroscale technology, friction caused by surface ridges or crevices
is the bane of the nanoengineer鈥檚 life. Until last week, any flaws in the
crystalline components of microelectromechanical systems (MEMS), such as tiny
pumps or motors, were impossible to remove. Now researchers at Washington State
University have come up with a way. Their nanosandpaper uses a combination of a
caustic solution such as sodium hydroxide and an atomic-force microscope tip to
level tiny regions of MEMS components.
鈥淲e call it a `one-two punch鈥� because we are getting smoothing from both the
AFM tip and a chemical solution,鈥� says team leader J. T. Dickinson, speaking at
the annual Vacuum Society meeting in San Francisco. While conventional sandpaper
simply mows down bumps on a surface, the caustic solution dissolves a hyperthin
surface layer, which the AFM tip smoothes so that it lies flat.
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By changing the composition, pH and concentration of the solution,
the Washington State team have got their method to work on different crystal
types. Their technique can even fill in pits because the AFM tip is able to drag
ions from ridges and terraces and deposit them in the cavities.