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Many Challenges--But Many Paths To Follow

The challenges in scaling another factor of 1000 shouldn't be minimised. Developing millimetre scale electronics and micrometre scale integrated circuits wasn't easy, either, but after we overcame the initial obstacles, both progressed much faster and further than anybody initially expected.

The remarkable thing about molecular engineering is that it looks like there are many different ways to get there and, at the moment, rapid progress is being made along every path--all at the same time.

  In 1988, a group at duPont led by William deGrado designed a new protein, called alpha 4 from scratch, and manufactured it in their laboratory. This protein, which never existed in nature, is more stable than natural proteins its size. Researchers around the world are now looking at proteins as molecular structures they can design and build, just as an IC designer lays out a chip.

Chemists are making progress in designing and synthesising molecules that bind to other molecules at specific sites, facilitating the kind of self-assembly that occurs in biology. The 1987 Nobel Prize in chemistry was awarded for just such work.

I've already alluded to the feats accomplished so far with scanning probe microscopes. We now have a tool that lets us see and move individual atoms. STMs have also been used to pin molecules to a substrate and break molecular bonds. John Foster of IBM and Eric Drexler have suggested in a recent paper in Nature that attaching custom molecules to the tip of a scanning microscope may allow assembling objects with up to 10,000 molecular pieces, with atomic precision.

The ability to model and simulate complex molecular systems has been growing rapidly in recent years, driven both by advances in raw computing power, but also by the development of better simulation techniques that now permit modeling of proteins composed of thousands of atoms.

Physicists and electrical engineers are making rapid progress in fabricating electron devices that work at the molecular level. In the past two years, Texas Instruments and Bell Labs have reported molecular-scale quantum transistors and have fabricated quantum wires with X-ray lithography. These quantum wires are on the order of 30 nanometres wide.

Materials scientists and mechanical engineers are fabricating new materials called ``nanocomposites,'' made up of individual particles ranging from 100 to 1000 atoms. These appear to have electrical and mechanical properties unlike any other engineering materials and may prove useful in the near future.

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Editor: John Walker