Electrical insulation of carbon nanotube separation columns for microchip electrochromatography

Carbon nanotubes (CNT) have been grown in microfluidic glass channels for chemical analysis based on electrokinetic separations. A limitation of CNTs for this type of application is their high conductivity, which prevent them from being used for electroosmotic pumping with electrical field strengths in the range of 0.5-1.0 kV/cm. This range of field strength is desirable for most electrokinetic separation systems in order not to have excess band broadening from diffusion due a too low mobile phase velocity. Here, we have approached this limitation by patterning the CNTs into micrometer sized regions in order to significantly lower the conductivity of the carbon nanotube layer. By this approach, the electrical field strength that can be sustained by the column is increased from around 100 V/cm to more than 2 kV/cm. This is more than one order of magnitude higher than previous reports.