Carbon nanotube-based sensors are good at sniffing out all kinds of things, but applying the cylindrical molecules to a substrate has traditionally been a dangerous and unreliable process. Now, researchers at MIT have found a way to avoid the hazardous solvents that are currently used, by compressing commercially available nanotube powders into a pencil lead-shaped material. That allowed them to sketch the material directly onto paper imprinted with gold electrodes (as shown above), then measure the current flowing through the resisting carbon nanotubes -- allowing detection of any gases that stick to the material. It works even if the marks aren't uniform, according to the team, and the tech would open up new avenues to cheaper sensors that would be particularly adroit at detecting rotten fruit or natural gas leaks. For more info, sniff out the video after the break.