Researchers develop new breathalyzer that can detect marijuana

The breathalyzer was developed using carbon nanotubes, tiny tubes of carbon 100,000 times smaller than a human hair. The THC molecule, along with other molecules in the breath, binds to the surface of the nanotubes and change their electrical properties. The speed at which the electrical currents recover then signals whether THC is present. Nanotechnology sensors can detect THC at levels comparable to or better than mass spectrometry, which is considered the gold standard for THC detection.

"The semiconductor carbon nanotubes that we are using weren't available even a few years ago," says Sean Hwang, lead author on the paper and a doctoral candidate in chemistry at Pitt. "We used machine learning to 'teach' the breathalyzer to recognize the presence of THC based on the electrical currents recovery time, even when there are other substances, like alcohol, present in the breath."

Hwang works in the Star Lab, led by Alexander Star, Ph.D., professor of chemistry with a secondary appointment in bioengineering. The group partnered with Ervin Sejdic, Ph.D., associate professor of electrical and computer engineering at the Swanson School of Engineering, to develop the prototype.

"Creating a prototype that would work in the field was a crucial step in making this technology applicable," says Dr. Sejdic. "It took a cross-disciplinary team to turn this idea into a usable device that's vital for keeping the roads safe."

The prototype looks similar to a breathalyzer for alcohol, with a plastic casing, protruding mouthpiece, and digital display. It was tested in the lab and was shown to be able to detect the THC in a breath sample that also contained components like carbon dioxide, water, ethanol, methanol, and acetone. The researchers will continue to test the prototype but hope it will soon move to manufacture and be available for use.

"In legal states, you'll see road signs that say "Drive High, Get a DUI,' but there has not been a reliable and practical way to enforce that," says Dr. Star. "There are debates in the legal community about what levels of THC would amount to a DUI, but creating such a device is an important first step toward making sure people don't partake and drive."