Nuts and bolts that redefine 'tiny'

Machinery that drove an industrial revolution a couple of centuries ago was often as large as a locomotive. You couldn't miss it when a new development made the scene. Mechanisms underlying this century's industrial progress are as small as molecules. Few of us note their arrival.

Take Hicham Fenniri's "microtruss," for example. The Purdue University chemist and his colleagues have developed a molecule-size analogue of the nuts, bolts, and universal parts of the old technology. These can be assembled into tiny linear structures to which other substances can be attached.

Depending on what these substances are and exactly how the structure is put together, the assembly could perform a variety of functions.

It might become an element in an electronic device. It could form part of a biosensor or other biomedical device inserted into a plant or animal body.

It could be a conduit taking in solar energy photons at one end and delivering them somewhere else. That would be useful in photoelectric devices or in systems that mimic photosynthesis. Future computers, for instance, are expected to rely on light instead of electric current.

The point, Professor Fenniri says, is that his microtruss is "amenable to engineering." He expects it to become a standard element in the parts inventory on which engineers will draw to design and fabricate useful devices.

That, in turn, makes it what Fenniri calls "a very nice example" of the nanotechnology that is likely to drive much industrial development from now on.

It's called "nano" because the basic machinery is measured in terms of nanometers (billionths of a meter). While some researchers have developed microscopic tweezers and pushers, it's hard to build this stuff by hand. Instead, many laboratories – including Fenniri's lab in West Lafayette, Ind. – are learning to make the machinery assemble itself.

"This is essentially what nature has been doing forever [in biology]," Fenniri says. In his case, he took a clue from DNA, the molecule that carries the genetic code. Using the same kind of chemical bonding that holds DNA together, his group designed a new molecule that automatically forms a six-member rosette. You can think of it as a little doughnut.

These "doughnuts" assemble themselves into a tube. Electric charges on the doughnuts line up to produce an electrostatic belt that wraps around the tube and stabilizes it. It also provides a structure to which other molecules or metal atoms can attach.

A computer simulation looking down into such a tube shows a central channel formed by the stacked rosettes. Molecules attached to the individual rosettes form 12 additional outer channels.

The channels could conduct various kinds of electrically charged atoms or molecules. The whole structure is less than 100 atoms across.

It may take decades for nanotechnology to have a major impact. But the emergence of foundational technology like the microtruss is as prophetic as was the emergence of the first experimental steam engine. What we're seeing, Fenniri says, "is basically the industrial revolution of the 21st century."

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