DNA makes nanotube transistors

Researchers from the Weizmann Institute of Science in Israel have harnessed the self-assembly abilities of DNA to construct field-effect transistors from carbon nanotubes.

Carbon nanotubes are rolled-up sheets of carbon atoms that can be narrower than one nanometer, which is the span of 10 hydrogen atoms. DNA is made of four types of bases -- adenine, cytosine, guanine and thymine -- connected to a sugar-phosphate backbone. Bases on single strands of DNA pair up to form the familiar double helix of biological DNA. Artificial stretches of DNA can be engineered so that stretches of DNA combine to form structures. DNA can also be engineered to connect to objects like carbon nanotubes.

The researchers attached DNA strands to carbon nanotubes and complementary strands to gold electrodes that were anchored to a silicon surface. The electrodes were prepared using standard chip-making techniques. They mixed a liquid containing the DNA-coated nanotubes with the silicon, and the complementary DNA strands combined, placing the nanotubes across pairs of electrodes.

The transistors could eventually be used in small, fast computer circuits. The researchers' method promises to scale up to suit mass-production requirements. The method could allow for real-time modifications of the electrical behavior of the devices by introducing biological molecules capable of interacting with the DNA, according to the researchers.

The method yields transistors for about 10 percent of the electrode pairs, according to the researchers. They are working on improving the yield by modifying the degree and location of DNA coverage of the carbon nanotubes.

Other researchers have recently use more complicated processes to coax DNA to assemble carbon nanotube transistors, but these are less suited to mass fabrication, according to the researchers.

The Weizmann method could be used to fabricate practical transistors in two to five years, according to the researchers. The work appeared in the November 22, 2004 issue of Applied Physics Letters.