Drawing with carbon nanotubes? (via MIT & Jan Schnorr)
Development surround Carbon Nanotubes continue to surprise and amaze. The electrically conductive material makes for an acute sensor. In particular, it can detect the presence of gases as a drastic change of their conductivity occurs when certain gasses stick to the nanotubes. Coating them with polymers of different substances can change which gases they interact with. Copper coatings, for example, are used to detect ethylene gas that is released during the ripening of fruit and could be used for better food management.
A problem with these sensors is that they imply the use of nanotube solvents, like dichlorobenzene, that are toxic, harmful and not entirely reliable, to deposit the nanotubes onto gas-detecting circuits. MIT postdoctoral Katherine Mirica and her team have developed a new method that facilitates their application and does not require these harmful chemicals.
Mirica was able to compress commercially available single-walled carbon nanotube (SWCNT) powders to resemble a more common form of carbon, pencil lead. The compression is just enough to hold the nanotubes to a solid form but layers of them can be deposited on paper much like regular pencil lead. Handling and application of SWCNT in this compressed form is incredibly safe and stable. Sensors made using this nanotube lead work better on smoother papers and the team found that the marks do not have to be uniform for functionality. The team drew an SWCNT layer to connect gold electrodes and created a sensor that detects ammonia.
These hand-drawn sensors can detect gases in concentrations of 0.5 parts per million. This research has scientists hopeful towards mass producing sensors, cheaply and in a safe manner, that detect all sorts of volatile gases like sulfur compounds, natural gas etc. The team was lead by Timothy Swager, a John D. MacArthur Professor of Chemistry and the research was funded by the Army Research Office through MIT’s Institute for Soldier Nanotechnologies and a National Institutes of Health fellowship.
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