In Book III, pg. 247, Kryon replied to a letter by stating that we need to look towards biological beings as the greatest computer ever, and we should being to merge the 2 together. In the March issue of Science (Vol.279, pg. 2043-2044) there was the following article about using our own DNA structure to "marry" different metals and oxides together to create information arrays:

OPTOELECTRONICS:
Double Helix Doubles as Engineer

Sunny Bains

A marriage of optics and electronics could produce a new generation of computers many times faster than today's. But like many unions, this one is threatened by some serious incompatibilities. Many of the best lasers, detectors, light modulators, and other optical devices are made from semiconductors such as gallium arsenide and indium phosphide, whereas conventional electronic devices are made of silicon. As a result, the two kinds of devices have to be made separately, then mated. Although integrating one or two devices is relatively easy, assembling hundreds, thousands, or millions into a single array would defeat conventional "pick-and-place" technology.

Now, a team of researchers at the University of California, San Diego (UCSD), and Nanotronics Inc., also in San Diego, has come up with a novel way to create these hybrid devices. Like so much of the mating game, it involves DNA, which in this case serves as a selective glue for sticking the devices to the surface of the chip. Described at a meeting of the International Society for Optical Engineering early this year in San Jose, California, the work has intrigued experts in the field.
Electrical engineer Joseph Talghader at the University of Minnesota, Minneapolis, for example, calls it "an exciting technique and one that merits a great deal of future work."

A strategy developed by Talghader and others was actually the starting point for the San Diego team, which is led by UCSD's Sadik Esener. In the earlier technique, known as fluidic self-assembly, the optical devices are fabricated as geometric shapes ("pegs") that can then slot into similarly shaped "holes" etched in the silicon substrate. The pegs are suspended in a liquid and spilled out over the substrate, with luck sliding into the right hole and sticking there thanks to weak van der Waals forces.

The San Diego researchers were looking for a way to help the right peg find its hole, and they settled on DNA. The chemical bases that make up DNA--cytosine, guanine, adenine, and thymine--will bind to each other only in particular pairings: C with G and A with T. Hence, a single strand made up of the bases ATTTGC will bind strongly with its complementary strand, TAAACG, and not with any other sequence. The researchers set out to exploit this selectivity by attaching short complementary strands of DNA to the pegs and substrate to help the devices find their correct positions.

In their first experiment, the team coated a substrate with a particular short strand of DNA. They then covered parts of the substrate with a mask and exposed it to ultraviolet light. The light chemically altered the DNA in exposed areas so that it could no longer bind to complementary strands. The researchers then coated some microbeads--which acted as dummy devices--with strands of DNA complementary to those on the substrate. When a fluid carrying the coated beads was splashed over the substrate, the beads successfully bound only to those areas that had not been
exposed to UV light. One drawback of the technique is that it worked only for small devices, several hundred micrometers across, that would flow easily and not block other devices.

In a second experiment, designed to show that several varying kinds of "devices" could be deposited at once, the group used masks to deposit four different types of DNA strands onto a substrate and then attached complementary strands to four different fluorescent molecules. When the labeled molecules were splashed onto the substrate, the pattern of fluorescence showed that they had bound only to the appropriate regions of complementary DNA. In a real system, this would mean that four completely different types of devices could be attached to many selected sites on a chip.

The researchers realize, however, that just providing the glue is not going to be enough. They are now looking for more active ways to guide the devices to their correct positions. One possibility is to add extra chemical groups to the DNA on the devices to give them an electric charge, then create electric fields on the substrate to attract the charged devices to "landing sites." The team is also investigating other techniques, such as creating currents in the fluid that would sweep the tiny devices
to the right places.

An even bigger challenge will be creating an electrical connection between the devices and their host semiconductor. The team is looking at the possibility of putting the DNA glue on the top of devices and bonding them, upside down, onto a dummy substrate. Once all the devices are in position, the dummy could be flipped over and pressed down on the real substrate. The substrate might be coated with molten solder, which would add an electrical bond to the mass marriage.
 

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Sunny Bains is a science writer based in the San Francisco Bay area.

Volume 279, Number 5359 Issue of 27 March 1998, pp. 2043 - 2044
©1998 by The American Association for the Advancement of Science.