Carbon nanotube pencil used to draw sensor circuits

Chemists have developed a method to use carbon nanotubes, which are 50,000 times thinner than human hair, to form pencil lead. This pencil lead is used to complete electric circuits in gas sensors printed on paper with gold electrodes. The sensors can be modified to detect specific gases, as gas molecules bind to the nanotubes, disrupting the current flow and breaking the circuit. Practical applications include detecting sulfur compounds in natural gas leaks and ethylene released by ripening fruit.

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