Silicon is Slow

Williams and fellow HP researcher Phil Kuekes are on the threshold of marrying moletronics with silicon technology. Last July, they were awarded a patent for a method they devised that allows molecule-size circuits to communicate with traditional semiconductors; by 2005, they and a team of researchers at UCLA expect to produce a 16-kilobit memory circuit. In 10 to 15 years, Williams says, pure moletronic circuits will begin to replace traditional chips in devices like handheld computers. Perhaps the greatest impact will be in biomedical implants-tiny computers could be inserted into the human body to, for example, measure insulin levels or warn of a pending heart attack. Much research is being done on the mechanics of cells and on cellular information exchange at the DNA level, and at some point, tiny machines will know how to talk to cells in cell language.


Where it will all end is, however, conjecture: "We're quite a long way from being able to augment human physical or mental capabilities just by plugging something into our bodies," Williams says.


The Double Helix as Computer
Beyond silicon and moletronics lie redefinitions of computing that are much stranger and harder to conceive. One method utilizes DNA. There's logic to this: DNA is nature's extraordinarily efficient data storage and delivery mechanism for life processes, and the familiar four-base double helix structure encodes enormous amounts of information at the molecular level. DNA combines in consistently predictable ways, and 10 trillion strands can fit in a teaspoon. By turning each of these strands into a type of "processor," scientists foresee building a nanocomputer that performs trillions of calculations at the same time.


In 1994, University of Southern California professor Leonard Adleman set the stage by using DNA to solve the Hamiltonian Path, or traveling salesman problem. This problem seeks the shortest route between a number of cities, with no city being visited more than once. When only a few cities are involved, you can solve the problem with a pencil and paper. As the number of cities grows, the number of potential routes a conventional computer must try in sequential fashion increases exponentially. To get the answer quickly, you'd have to divvy up the question among a large number of computers working in parallel. Or you could, as Adleman did, solve the puzzle by letting a few teaspoons of DNA generate all possible solutions simultaneously.


Adleman illustrated the methodology for performing a massively parallel chemical reaction-with each possible answer provided in the form of a strand of DNA code-then spent a week sorting the incorrect strands from the correct answer. Computing with DNA may sound odd, but it's a logical product of the biochemical research that has enabled scientists to decode, manipulate, and synthesize the genetic material of plants and animals.