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Take a little DNA; add a pinch of carbon nanotubes; sprinkle in a few grains of gold, all on a clean silicon surface, and whip up a batch of nanotransistors – that’s pretty much what the research group of Prof. Ron Naaman of the Chemical Physics Department of the Weizmann Institute did. Only, they began with even more basic ingredients: tiny spoonfuls of phosphates, sugars and nucleotides that were used to create unique strands of DNA programmed to form attachments with carbon nanotubes.
Next, they used the same method to create another set of DNA strands that would hook up to miniscule electrical contacts made of gold that were anchored on the silicon surface. Afterwards, they added the first group of ingredients to the second and mixed well. The DNA strands fastened to the carbon nanotubes latched on to the strands attached to the gold contacts. The end result was a sort of carbon nanotube “bridge” spanning the silicon surface between two gold contacts.
Similar nanobridges between electrical contacts made of conducting materials such as gold may one day form the basis of tiny nanotransistors that will be used to build tiny, fast and efficient electronic circuits. In addition, the use of DNA may allow other biological molecules to be integrated into the circuit design that would interact with the DNA strands, thus modulating the behavior of the device. In their experiment, the results of which were published in Applied Physics Letters, the team managed to create nanotransistors with 10 percent of the available gold contact pairs, a figure they are currently working to improve.
The simple composition of DNA has inspired many scientists around the world to engineer its component nucleotides into new structures. Double-stranded DNA is shaped like a twisted ladder, each “step” constructed of two separate nucleotides. These nucleotides link up in a pre-determined way: thymine always affixes to adenine and guanine always to cytosine. Not only have scientists been able to link bits of DNA together to form new structures, they can make them attach to metals and carbon nanotubes, those atom-thick sheets of carbon rolled up into extra-strong hollow tubes the width of a mere 10 hydrogen atoms.
Though the Weizmann team is not the first to try building nanotransistors using DNA, their method appears to be the most suitable to date for large scale production and the development of a variety of industrial applications.
Prof. Ron Naaman's research is supported by the Fritz Haber Center for Physical Chemistry; the Ilse Katz Institute for Material Sciences and Magnetic Resonance Research; The Philip M. Klutznick Fund for Research; Dr. Pamela Scholl, Northbrook, IL; and the Wolfson Advanced Research Center.
Prof. Naaman is the incumbent of the Aryeh and Mintze Katzman Professorial Chair.