Nanowires Bend to Implant Pressures

R&D DIGEST

Electronic devices made from bent nanowires could be suitable for implants that monitor blood pressure. The devices are very sensitive and could be used to measure even the smallest pressure changes. A team from Georgia Institute of Technology in Atlanta created the components.

The team chose zinc as the foundation of the components because of the material's coupled semiconducting and piezoelectric properties. Bending the structures of the nanowires creates a charge separation. Such separation of negative and positive ions produces a measurable electric current. The current flow is controlled by changing the conductance of a nanostructure by bending it between the source and drain electrodes. The bending produces a gate potential across the nanowire, and the resulting conductance is directly related to the degree of bending applied.

“These devices could provide the fundamental building blocks that would allow us to create a new area of electronics,” says Zhong Lin Wang, a regents professor in the school of materials science and engineering at Georgia Tech. The bending of the wire, she says, picks up changes in forces as small as a few nanonewtons (10^–12 N).

The team used zinc as the basis of the devices for several reasons. For one, zinc can tolerate deformation without being damaged. That means it can be used in folded power sources. Also, zinc is biocompatible and can conform to odd or moving conditions, such as body implants.

One of the many applications that Wang sees the nanowires being used for is to create an implantable sensor in the arm. Such a sensor would be biocompatible, flexible, and durable. Once in place, even minute changes in pressure from pulsing blood vessels would bend the wires, creating a current so blood pressure could be continuously measured. The sensor could then wirelessly transmit the pressure reading to an external receiver device, perhaps worn on the wrist, which would then display the data.

So far, the researchers have created field-effect transistors, diodes, and sensors from nanowires.

An online report of the team's work appears in the February 13 issue of the journal Advanced Materials. The research has been sponsored by the National Science Foundation, Defense Advanced Research Projects Agency, the National Institutes of Health, and NASA.

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