DNA Motors Could Make Test Tube ICs Possible
Peter Singer, Editor-in-Chief -- Semiconductor International, 9/1/2000
 |
"This technology has the potential to replace existing manufacturing methods for integrated circuits, which may reach their practical limits within the next decade when Moore's Law eventually hits a brick wall," said physicist Bernard Yurke of Bell Labs.
DNA, which provides the molecular blueprints for all living cells, is an ideal tool for making nanoscale devices. "We took advantage of how pieces of DNA — with its billions of possible variations — lock together in only one particular way, like pieces of a jigsaw puzzle," Yurke said.
The researchers designed pieces of synthetic DNA that would recognize each other during each step of making the DNA motors. As a result, the only necessary ingredient in a laboratory test tube was DNA itself. "Because DNA acts as the fuel' for these motors, they are completely self-sufficient and do not require other chemicals to operate," Yurke said.
The self-assembling aspect of the DNA motors also is crucial for manufacturing nanodevices. "Given the size scale, no other approach appears to be practical," Yurke said. "This may lead to a test-tube-based nanofabrication technology that assembles complex structures, such as electronic circuits, through the orderly addition of molecules."
While DNA typically exists in a double-stranded form — similar to a twisted ladder — the researchers began with three single strands, each resembling a ladder sliced down the middle. Strand A has the correct DNA sequence to latch onto half of strand B and half of strand C, and so joins them all together. Strand A also has a hinge section between the parts that bind to B and C, so the two "arms" — AB and AC— can move freely.
On its own, the DNA structure floats with its arms wide open (Fig. a). The arms are pulled shut by adding a DNA fuel strand, which is designed to attach to the dangling, unpaired sections of strands B and C (Fig. b). To re-open the tweezers, the fuel strand is removed by adding another strand with the right DNA sequence to pair up with it (Fig. c).
"The entire population of 30 trillion DNA tweezers in a few drops of solution can be repeatedly closed and opened by successively adding fuel and removal strands," said Andrew Turberfield, a physicist at the University of Oxford who spent a recent sabbatical year at Bell Labs. Other scientists participating in the research were physicist Allen Mills and post-doctoral fellow Friedrich Simmel of Bell Labs, and Jennifer Neumann, a graduate student at Rutgers University.
Yurke said he was inspired to devise DNA motors when he realized molecular-scale protein motors in living organisms are responsible for muscular contraction and moving substances around in cells.
The Bell Labs scientists already are working to attach DNA to electrically conducting molecules to assemble rudimentary molecular-scale electronic circuits. •
