These nanowires, tagged with DNA
are assembled, and have been
exposed to complementary DNA
that is tagged with fluorescent dyes;
© Penn State
The method eventually allows the production of a handheld, portable device that can recognize and immediately report on environmental or medical compounds.
"Probably one of the most important things for connecting to the circuit is to place the wires accurately," says Theresa S. Mayer, professor of electrical engineering and director of Penn State's Nanofabrication Laboratory.
Using standard chip manufacturing, each type of nanowire would be placed on the board in a separate operation. Using the researchers' bottom-up method, they can place three different types of DNA-coated wires where they wanted them, with an error rate of less than 1 percent.
"This approach can be used to simultaneously detect different pathogens or diseases based on their nucleic acid signatures," says Christine D. Keating, associate professor of chemistry.
"Device components such as nanowires can be synthesized from many different materials and even coated with biological molecules prior to assembling them onto a chip," the researchers explained. They add that positioning the nanowires accurately is still difficult using conventional methods.
Using their assembly method, the researchers can place specific nanowires in assigned areas. They begin with a chip with tiny rectangular depressions in the places they wish to place the nanowires. They then apply an electrical field between electrodes that define the area where they want the nanowires to assemble. The Penn State researchers inject a mixture of the tagged nanowires and a liquid over the top of the chip. The nanowires are attracted to the area with an electric field and they fall into the proper tiny wells.
The researchers then move the electric field and position the next tagged nanowires. In this proof-of-concept experiment, the different tagged wires were placed in rows, but the researchers say that they could be placed in a variety of configurations.
After all the wires are in place, they can be made into a variety of devices including resonators or field effect transistors that can be used to detect nucleic acid targets.
COMPAMED.de; Source: Pennsylvania State University