Carbon nanotube sensors are a new must-have in contaminated areas, providing the ability to detect harmful gases and warn of danger. But the volatile nature of the sensors makes large-scale production a difficult task. Scientists at MIT however, have developed a new solution—a carbon nanotube mechanical pencil which with just a stroke of the point transfers a nanotube sensor onto a sheet of paper.

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MIT postdoc Katherine Mirica took on the challenge of creating a safe way to install carbon nanotube sensors, in a way that could increase production for bigger projects. Her answer was back to the basics, by taking inspiration from her desk instead of the lab. Rather than using graphite in a pencil, Mirica compressed carbon nanotube powder and made her own pencil lead. The solid material could then be controlled, as output through the tip of a mechanical pencil.

By creating marks on a paper surface, Mirica’s pencil is actually inscribing carbon nanotube sensors. These tiny paper sensors can then be used to detect toxins like ammonia and other harmful gasses. The ease of using a pencil to apply the sensors expands the possibilities of creating a multitude of them for multiple volatile materials.

The carbon nanotube pencil lead is drawn in lines on gold electrode-printed sheets of paper, then an electrical current is applied. If the current is disrupted, then gas is present—it is as simple as that. Mirica’s invention could make the ease of toxin detection be as simple as jotting lines on a piece of paper.


Photo by Jan Schnorr, MIT