A team of chemists from the Massachusetts Institute of Technology (MIT) is rethinking the design and construction of carbon nanotubes so that they can be used in manufacturing without harmful health and environmental impact.
In their simplest form, carbon nanotubes are very small hollow cylinders of carbon atoms, roughly 50,000 times thinner than human hair. But for MIT chemists what makes carbon nanotubes interesting isn’t their size, but rather their unique ability to conduct electricity, which makes them effective components in harmful-gas detectors.
The unhindered flow of electrons through nanotubes creates a sensitivity that sets them apart from lesser alternatives, but up until now, the wide-scale use of carbon nanotubes in gas detectors has been constrained by the hazardous chemicals used in the methods of production. Simply put, carbon nanotubes aren’t safe to make.
This was priority number one for the team at MIT; develop new nanotube manufacturing processes that produce fewer toxins.
The chemists found that by compressing carbon nanotubes into a material that looks and acts like the flat sheets of carbon in graphite, they can create an infinitely more stable product without the use of harmful chemicals.
Further, by simply pressing a powder of carbon nanotubes into graphite form the team has created a substance that works like the lead in a pencil. By applying pressure, the new material can deposit entire nanotubes onto a paper sensor, effectively “drawing” circuitry between gold electrodes.
The result: a highly customizable hazardous gas sensor no more harmful than drawing with pencil and paper.
“The ability to fabricate sensors from carbon nanotubes by drawing on paper with a mechanical pencil can be a very cost-effective manufacturing method for CNT-based gas sensors,” said research team member, Katherine Mirica.
But for commercial success, Mirica says, several challenges remain and further development is needed.
“One of the steps for further development is adapting our technology towards the design of selective gas sensors for specific applications. Another step is comprehensive characterization of sensors for selectivity, stability, and ability to operate at a variety of environmental conditions such as heat and humidity.”
The MIT team hopes that this new gas sensor technology will be useful in healthcare and food industries in detecting harmful ammonia gases.
Photo courtesy of MIT