A handheld, ultra-portable device that can recognize and immediately report on a wide variety of environmental or medical compounds may eventually be possible, using a method that incorporates a mixture of biologically tagged nanowires onto integrated circuit chips, according to Penn State researchers.
"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. "We need to control spatial placement on the chip with less than a micron of accuracy."
Using standard chip manufacturing, each type of nanowire would be placed on the board in a separate operation.
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.
While the researchers have not yet connected each individual device to the underlying circuitry, they did test their chip to ensure that the wires assembled in the proper locations. They immersed the chip in a solution containing DNA sequences complementary to the three virus-specific sequences on the nanowires. Because they tagged the complimentary DNA with three differently colored fluorescent dyes, the attached DNA showed that the wires were in the proper places.
The researchers believe that their assembly method is extremely flexible, capable of placing a variety of conducting and non-conducting wires with a wide array of coatings.
"The eventual idea would be to extend the method to more nanowire types, such as different DNA sequences or even proteins, and move from fluorescence to real-time electrical detection on the chip," says Keating. ###
Researchers working on this project include Mayer; Keating; Thomas J. Morrow, graduate student in chemistry; Jaekyun Kim, graduate student in electrical engineering; and Mingwei Li, recent graduate student in electrical engineering. The National Science Foundation and the National Institutes of Health supported this work.
Contact: A'ndrea Elyse Messer aem1@psu.edu 814-865-9481 Penn State
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