Bottom-Up Assembly of Nanowires for Chip-based Sensing

nanowire assembly
From top to bottom: Nanowires are functionalized off-chip, nanowires are aligned between electrodes, a clamp window is made using a mask, nanowires are clamped, and nanowires are tested with target molecules. Image credit: Penn State

In a paper appearing in the journal Science an interdisciplinary team of Penn State researchers from chemistry and electrical engineering report a novel method of bottom-up assembly of nanowires on standard electronic chips. Nanowires functionalized for a variety of purposes off-chip can be placed with precision in predefined wells or shallow depressions on an electronic chip by using electrical fields generated by carefully placed electrodes. A solution containing the functionalized nanowires is deposited on the chip and the electrodes are turned on, aligning the nanowires in the wells. Other groups of nanowires can then be laid down in succession by turning on other sets of electrodes.

The benefit of the bottom-up approach is that it allows for many types of materials with a variety of coatings to be connected to electronic circuitry without the damage caused by top-down approaches. The researchers expect they will be able to use nanowires as resonators and field effect transistors to act as tiny biological and chemical sensors for medical and environmental monitoring, among many other possible uses.

The team included Theresa Mayer, professor of electrical engineering and director of the Nanofabrication Laboratory in the Materials Research Institute; graduate student Jaekyun Kim and recent graduate student Mingwei Li in electrical engineering; associate professor of chemistry Christine Keating; and graduate student in chemistry Thomas J. Morrow. Their work was supported by the National Science Foundation and the National Institutes of Health. You can read more about nanowire research in the Fall 2008 issue of Focus on Materials.

This article was featured in Focus on Materials - Winter 2009.