SMARTER STRATEGIES

Nanoprocessor Harnesses Bottom-Up Manufacturing

R. Colin Johnson | Date: 02-22-11 | Comments

Over five decades ago, visionaries predicted that nanotechnology would enable the building of microscopic computers from the "bottom up" by assembling molecules one at a time. Finally, the first arithmetic-logic unit (ALU) using a bottom-up approach has been demonstrated.

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Nanoprocessor Harnesses Bottom-Up Manufacturing
In 1959, U.S. physicist Richard Feynman gave a now-famous talk on top-down nanotechnology called "There's Plenty of Room at the Bottom," which proposed building computer circuitry using molecule-by-molecule additive synthesis rather than lithographic subtractive synthesis (which is still in use today). Until now, no one has been able to realize Feynman's seminal vision.

Today, computer circuitry is made with lithographic masks that photographically define regions to be etched away from the top down. Called subtractive synthesis, the method cuts away unneeded silicon the way a sculptor removes unneeded stone to reveal the latent statue inside. The problem with the top-down approach is that any nanoscale variations in the bulk material being etched away are exacerbated as microchips shrink to smaller and smaller sizes. Such impurities eventually cause microchips to fail when their size is shrunk to the same scale as these bulk-material variations.

Feynman's vision was to use self-assembling molecules to construct computers from the bottom up, thereby sidestepping the material-variation problem and enabling circuitry to be constructed from individual molecules�the ultimate in micro-miniaturization.

Unfortunately, the bottom-up approach has proved much more difficult to engineer into a commercial process than anyone envisioned. In 1986, nanotechnologist K. Eric Drexler extended Feynman's concept to envisioning tiny nano-machines that would build these perfect circuits from individual molecules in his book "Engines of Creation: The Coming Era of Nanotechnology." Despite bold attempts to craft molecular nanotechnology by forward-thinkers like Nobel Prize winner Richard Smalley, microchips today are still built using subtractive synthesis.

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