Low-cost sensors and other flexible electronics can be made by spraying thin films of carbon nanotube onto flexible plastic substrates, according researchers at TUM (Technische Universität München) in Germany. To prove the concept, a TUM research team recently fabricated gas detectors on a flexible polymer substrate.


The TUM researchers showed that carbon nanotube thin films can work as gas detectors in the form of a resistor network whose impedance changes when it comes in contact with molecules of a certain kind of gas. Such gas detectors fabricated on flexible plastic substrates were demonstrated for ammonia, carbon dioxide and nitrogen oxide.


Carbon nanotube thin-film gas sensors could be useful in a variety of applications, according to the researchers. For instance, inexpensive sensors could be integrated into compact air quality monitors or into food packaging that displays a freshness indicator, instead of depending on “best before” dates. The team is also working on other applications for their carbon nanotube thin films, including pressure and temperature sensors and a new type of solar cell.


The TUM researchers demonstrated two deposition processes. The first fabricates the carbon-nanotube films on glass, then uses transfer printing to move the carbon nanotube films onto a flexible substrate. The second deposits the carbon nanotube films directly onto a flexible substrate using an robotic nozzle spraying process.


For the future, the team suggested various applications for sensors sprayed onto large sheets of flexible plastic or other surfaces, such as the skins of robots to provide them with a sense of touch.