Inside the Star Lab for sensor development at the University of Pittsburgh, professor Alexander Star holds a black box, about the size of a remote control. It's a breathalyzer developed to measure tetrahydrocannabinol, or THC, the psychoactive component in marijuana.
The 3-D printed device has a mouthpiece for breathing into. Inside the box is a small sensor chip made up of carbon nanotubes: little tubes of carbon 1/100,000 the size of a human hair. These nanotubes detect the presence of THC and alcohol at extremely low levels. If the device picks up THC, "THC Detected!" appears on the embedded screen.
"What we're trying to accomplish is the quantitative measure of ... THC, which will show some number [on the device]," Star said. "And then down the road this number can be correlated to levels of intoxication."
This breathalyzer is one of a handful in development across the country, meant to eventually be a tool for law enforcement like an alcohol breathalyzer. Star said there's been more pressure to develop a portable way to measure THC in recent years.
"As many states are legalizing marijuana, there's a danger of people driving intoxicated," Star said.
However, a major roadblock exists: there's no research directly linking intoxication with the amount of THC in someone's breath. The chemical compound can stay in a person's system for days after using marijuana, far past the window when someone is actually stoned.
"The real challenge is not knowing whether or not somebody has used cannabis, but whether or not they're impaired from it," said Ryan Vandrey, a professor at Johns Hopkins University who studies how cannabis affects behavior.
Despite legalization in some states, marijuana is still a Schedule I substance at the federal level, which means researchers who want to study the drug have to jump through many regulatory hoops. Star's lab at Pitt has been testing their prototype with simulated breath, by mixing air, carbon dioxide and low levels of other components. They have approval from the U.S. Drug Enforcement Agency to mix THC into the simulated breath, but they're not allowed to do human studies.
"We're trying to find collaborators who actually have those human studies going on," Star said. "And trying to provide them with our breathalyzer so they can use them for their studies."
The hope, Star said, is that human studies with the prototype will shed more light on the correlation between impairment and THC levels in breath.