Nanotech News

October 17, 2005

Making Sense of High-Density Nanowire Circuits

As researchers develop methods for creating nanowire-based molecular sensors capable of detecting hundreds of biomarkers simultaneously, they will also need new techniques for analyzing the complex signals that such sensors will generate when they are testing complex biological samples. A team of investigators at the California Institute of Technology has now developed one possible method for making sense out of such data-rich signals and has verified that this approach works on an array that includes 150 nanowires.

Writing in the journal Science, James Heath, Ph.D., and his colleagues at Caltech describe their approach to "demultiplexing" the signals from ultrahigh-density nanowire circuits. Demultiplexing refers to the ability to electrically address, or get data from, large numbers of individual nanowires using many fewer electrical connectors. This is a particular challenge given that nanowire assemblies are often characterized by defects and some randomness in the way that the wires are organized in circuits.

To build their demultiplexer, Dr. Heath, who is a principal investigator of one of the NCI's Centers of Cancer Nanotechnology Excellence, and his collaborators used standard lithographic techniques to deposit pairs of conducting metal lines perpendicular to the nanowires, which all run parallel to each other like the strings in a piano. By passing an electrical current through the pairs, and varying which pairs are powered, the researchers are able to address an individual nanowire and determine its electrical status. For example, nanowires coated with a tumor biomarker detection reagent, such as an aptamer or antibody, display sharp changes in electrical behavior when those reagents bind to the biomarker they are designed to detect.

This work is detailed in a paper titled, "Bridging dimensions: demultiplexing ultrahigh-density nanowire circuits." This paper was published online in advance of print publication. An abstract is available through PubMed.
View abstract.