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.

What are carbon nanotubes and how are they related to the thickness of human hair?

Describe how the pencil made from carbon nanotubes can be used in electric circuits.

How can the sensors be modified to detect specific gases?

What is the mechanism by which gas molecules affect the current flow in the nanotubes?

List some practical applications of the sensors developed using carbon nanotubes.