Nanowire synthesis “breakthrough” targets sensors, diagnostics

February 2, 2007 – A new approach to synthesizing nanowires using CMOS-compatible technology could result in revolutionary highly sensitive biomolecule detectors for biological diagnostic applications, according to scientists at Yale U.

Bottom-up nanowires or similarly configured carbon nanotubes “require hybrid fabrication schemes which result in severe integration issues,” and ‘top-down’ fabrication methods of nanowire-like devices result in process-induced material and device degradation, according to an excerpt from their research, described in the Feb. 1 issue of the journal Nature. Instead, they say utilizing complementary metal oxide semiconductor (CMOS) field effect transistor compatible technology “eliminates the need for hybrid methods and enables system-scale integration of these sensors with signal processing and information systems.”

The researchers from Yale’s Institute for Nanoscience and Quantum Engineering used wet-etch lithography on commercial SOI wafers to build nanowires that are structurally stable, and with “unprecedented” sensitivity (down to 1000 individual molecules/mm3) for detecting antibodies and other biological molecules (see photo, court. Reed/Yale). The basis for the nanowire sensors is detecting hydrogen ions or acidity, within physiological range of reactions in the body. For example, within approximately 10sec the wires can register T-cell activation as the release acid to the device.

The real strength of the approach lies in its integration with CMOS technology, and use of “old fashioned” lithography that provides manufacturing uniformity, noted co-author Tarek Fahmy, assistant professor of biomedical engineering. Previous approaches utilized “the equivalent of a hacksaw,” he said, but now they are able to get high-quality smooth surfaces — and the nanowires also are also smaller than they were originally defined. “The sensor is essentially on the size scale of the molecules it is designed to sense,” added lead author and grad student Eric Stern.

The study focuses on device and sensor performance, but the approach “appears to have potential for extension to a fully integrated system, with wide use as sensors in molecular and cellular arrays,” the authors said.


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