Researchers in the US have built the first logic circuit on a molecular scale (18 µm) according to this story on nanotechweb.  This seems to reinforce the idea that circuits will not always be etched out of existing material, but grown one molecule at a time.  Small Form Factor indeed!
Researchers at IBM, the University of Florida and Columbia University, all in the US, have created a logic circuit on a single-walled carbon nanotube. This is the first time that an integrated circuit has been made on a single molecule.

“Our successful integration demonstrates the compatibility of carbon nanotubes with conventional circuit architectures,” Joerg Appenzeller of IBM told nanotechweb.org. “Our circuit uses a conventional CMOS-type architecture that ensures, in principle, low power consumption. It emphasizes that the use of nanomaterials does not automatically imply that well established circuit concepts have to be abandoned.”

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