Feb 18, 2009
CNTs line up inside lab-on-a-chip layout
Researchers at the Technical University of Denmark and the University of Cambridge, UK, have integrated vertically aligned carbon nanotubes in microfluidic glass channels as a step towards making miniaturized separation systems.
Because glass is non-conducting, contrary to silicon, it is possible to move liquids inside the channels by means of electrical fields, denoted as electro-osmotic flow. From a design perspective, this makes it possible to exchange bulky external pumps for a computer controlled power supply and appropriately positioned electrodes.
By applying high voltages across the liquid, the team was able to pump its sample through a high-density carbon nanotube forest embedded in a microfluidic channel. This will make it possible to use the carbon nanotube devices in the future for miniaturized chemical analysis systems.
The high surface-to-volume ratio of the carbon nanotubes and their hydrophobic surface makes the material ideal for the analysis of many organic compounds such as proteins. Different types of proteins are hydrophobic to varying degrees and will therefore interact with the carbon nanotubes in the fluidic channels differently. The high surface-to-volume ratio of the structure means that the chemicals will always be close to a surface as they pass through the device.
When a small plug of an organic sample, for example proteins, is pumped through the carbon nanotube channel, some of the proteins will not interact with the tubes and will therefore just be pumped through with maximum speed, while other interact with the tubes and will be retained and flow much more slowly. The net effect is a physical separation of the sample components (called chromatography) and by placing a detector at the end of the carbon nanotube channel it will ideally be possible to find the number of components in the sample and their concentration.
The researchers presented their work in Nanotechnology .
About the author
Klaus Mogensen is an associate professor at the department of Micro and Nanotechnology at the Technical University of Denmark (DTU) and is working on nanostructures in microfluidic devices for miniaturized chemical analysis systems.