Jul 26, 2016 10:48 AM
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The first is an ultrasmall gas chromatograph, an instrument commonly used in chemical analysis to separate mixtures of gases. To make a micro version of the instrument, the researchers etch a zigzagging, 35-centimeter-long channel on a silicon chip that is 800 micrometers on each side. As in conventional gas chromatography, different chemicals pass through the column at different rates, depending on their physical and chemical properties, so they exit the column at different times.
The output of the chromatograph feeds into the nanotube sensor. The sensor contains carbon nanotubes spanning the space between tiny gold electrodes. When various gases adsorb on the carbon nanotubes, the nanotubes’ electrical conductivity changes by a different amount. By measuring the change in conductivity after the gas binds to the nanotubes, the researchers can identify the gas.
