An interdisciplinary research team from the University of Pittsburgh has developed a breathalyzer device which measures the amount of the primary psychoactive compound found in cannabis (tetrahydrocannabinol, or THC) in the test user’s breath. The team of researchers, led by Drs. Alexander Star and Ervin Sejdic, had begun the development of the device in 2016.

“Creating a prototype that would work in the field was a crucial step in making this technology applicable. It took a cross-disciplinary team to turn this idea into a usable device that’s vital for keeping the roads safe.”

Dr. Sejdic, Professor of Electrical and Computer Engineering, University of Pittsburgh

The prototype of the new device looks similar to a breathalyzer test for alcohol; it contains plastic casing, a mouthpiece to breathe into, as well as a digital display. When the device prototype was tested in the lab, it was shown to be able to detect THC contained in a breath sample which also contained other components, including ethanol, carbon dioxide, water, acetone and methanol.

According to the researchers, the device was developed using carbon nanotubes, which are 100,000 times smaller than the size of a human hair. During the test, THC molecules in the breath attach to the surface of the nanotubes and change their electrical properties, changing the signal speed of electrical currents, indicating that THC is present. The news release from the University of Pittsburgh Swanson School of Engineering said that the nanotechnology sensors used in the device can detect THC similarly to or better than mass spectrometry, which, until recently, was considered to be the most sensitive technology for the detection of THC.

Sean Hwang, the principal author of the academic publication on the device and its properties told ScienceDaily that the semiconductor nanotubules used in the device were not available until recently. “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.”

The researchers are currently still testing the prototype and according to the researchers, the new device is nearly ready to be mass produced. In his interview with Here & Now, Dr. Star said, “If we have a suitable industrial partner, then the device by itself would be quite ready in a few months.” According to the researcher, the remaining steps include testing the device prototype and correlating the output provided by the device with the driver’s level of impairment.

However, according to the researchers, without an in depth understanding of the correlation between that amount of cannabis detected and the driver’s level of impairment, the device may not be useful to police. “I think there will be some push even for the [U.S.] federal government to actually allow researchers to look and correlate these levels of smoking and impairment,” Dr. Sejdic told ScienceDaily.