DNA could soon help tiny electrical circuits to build themselves, Israeli
researchers predict. Using tiny strands of DNA as templates, they have 鈥済rown鈥�
silver wires that are just a few nanometres wide between two electrodes.
As electrical circuits become ever smaller, it will eventually become
impossible to build them using conventional techniques such as photolithography.
So Erez Braun and his colleagues at the Technion-Israel Institute of Technology
in Haifa turned to the remarkable properties of DNA for help. 鈥淪elf-assembly
with DNA is well developed in nature,鈥� says Braun鈥檚 colleague Uri Sivan. 鈥淭he
whole toolbox is already there.鈥�
First, the researchers chemically anchored short DNA strands 12 base pairs
long onto the surface of tiny gold electrodes. These acted as selective hooks
for a longer strand of DNA, forming a bridge between the electrodes. They then
added positively charged silver ions, which stuck to the negatively charged DNA.
Reducing the ions to silver metal particles with a solution of hydroquinone
created a silver wire bridge 12 micrometres long between the electrodes, they
say in this week鈥檚 Nature (vol 391, p 775).
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The beauty of the technique is its flexibility, Braun says. By changing the
anchor鈥檚 base pairs, Braun and his team can select where the DNA will bind. So
with a network of electrodes carrying different anchors, each targeting DNA
bridges of different lengths, it should be possible to make a nanocircuit to
order.
However, the technique has its drawbacks. The silver wires have unusually
high resistance, possibly due to poor electrical contact between the silver
grains. Braun鈥檚 team hopes to improve the connections, for instance by using
gold, which is a better conductor than silver. 鈥淭he next challenge is to
self-assemble a transistor using the same techniques,鈥� says Sivan.
Braun says their work confirms that using DNA and proteins as templates for
building nanoscale electronics is feasible. 鈥淭here are not many other ways,鈥� he
says. 鈥淏iology naturally solves many of the problems.鈥�
