Jul 5, 2002
Molecular lithography builds up electronics
Scientists from the Technion-Israel Institute of Technology have demonstrated a new molecular lithography technique for growing molecular-scale electronic devices. The sequence-specific technique, which uses RecA protein, can deposit metal coatings at chosen locations on strands of DNA.
"Conventional microelectronics relies on optical lithography as an enabling technology for turning a virgin silicon wafer into the 100 million transistor circuit in a modern computer chip," Erez Braun of the Technion-Israel Institute of Technology told nanotechweb.org. "We have demonstrated an analogous concept on the molecular scale."
According to Braun, the sequence-specific molecular lithography technique is based on genetic recombination, in which the information encoded in DNA molecules replaces the masks that are used to imprint tiny features in silicon substrates in conventional optical lithography. "The DNA molecules interact with RecA, a major protein responsible for genetic recombination in bacteria, that functions as a molecular assembler and at the same time as a protecting resist," he added.
There are basically four stages to the Technion team's lithography process. First, monomers of the protein RecA polymerize on a single-stranded DNA molecule to form a nucleoprotein filament. Then the nucleoprotein filament binds to an aldehyde-derivatized double-stranded DNA substrate molecule at a specific site where there is a homologous sequence. Treatment with a silver nitrate solution causes silver aggregates to form along the DNA substrate, everywhere apart from at sites protected by nucleoprotein filaments. Finally the silver aggregates act as catalysts for wet-chemical gold deposition, thus converting the unprotected regions of the substrate to conductive gold wires.
In addition the scientists were able to grow metal islands at specific sites along the DNA substrate and to create three-way DNA junctions. They say that the realization of sequence-specific molecular lithography is an important step towards integrated DNA-templated electronics. The technique can operate on a broad range of lengthscales and has "essentially nanometre resolution".
The team reported its work in the 5 July issue of Science. Now Braun says that the plan is to develop a molecular switching device and possibly a logic circuit.
About the author
Liz Kalaugher is editor of nanotechweb.org.