We Can Figure This Out.org
Virtual Lab: Scanning Tunneling Microscope (STM)
University of Virginia
© 2003-Present, John C. Bean
The front end of the sample holder sits on two parallel rods. The back of the holder is held slightly above the rods by a the thin copper cradle. Piezoelectric crystals are glued to both sides of this cradle.

To move the sample holder out, a voltage is ramped up on the right piezo. As it expands, the cradle bends left. The voltage is then snapped off straightening the cradle. This is occurs so quickly that the cradle slips along the holder. As this ratcheting motion repeats, the sample holder is pulled leftward.

If instead, the voltage to the left piezo is gradually ramped up and then snapped off, the sample moves back toward the tip.

But for all of this to work, the cylinder and cradle must be kept free of any traces of oil or grease.
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