People arrested for DUIs or other alcohol-related offenses are sometimes ordered to wear so-called SCRAM (secure continuous remote alcohol monitoring) bracelets. The device, usually worn on the ankle, can detect alcohol consumption through the skin, alerting authorities if the user has broken his or her probation by drinking. Patients in rehabilitation programs often submit to alcohol monitoring as well, often through regular Breathalyzers or blood tests. But SCRAM bracelets are clunky and sometimes embarrassing, and tests require regular visits.
A team of scientists from the University of California, San Diego, has come up with a potential alternative: a tiny implantable chip. The one cubic millimeter biosensor is injected beneath the skin and powered by a wearable device like a smartwatch.
“Right now this chip could be useful for alcohol monitoring during treatment or diversion programs,” says Drew Hall, an electrical engineering professor at UC San Diego's Jacobs School of Engineering who led the project. “However, this is a platform technology that we feel can be expanded to many other areas of substance abuse treatment and monitoring, and ultimately other disease monitoring.”
Hall’s team presented their research at the 2018 IEEE Custom Integrated Circuits Conference in San Diego earlier this month.
The chip contains a sensor coated in alcohol oxidase, an enzyme that, when it encounters alcohol, generates a byproduct. When the sensor detects the byproduct, it transmits a wireless signal to the wearable that powers the chip. This can then transmit to doctors, rehabilitation programs, law enforcement officials or others. Other sensors on the chip measure background signals and pH levels to make the blood alcohol level readings more accurate.
The chip consumes only a tiny amount of power—970 nanowatts, about a million times less than the power a smartphone uses to make a phone call. This reduces the risk of heat generation inside the body, which is potentially harmful. The researchers tested the chip in vitro, mimicking the planned environment by using alcohol in diluted human serum beneath layers of pig skin.
The team says the chip has a number of advantages over traditional alcohol monitoring systems. Unlike SCRAM bracelets, it’s totally unobtrusive. It’s potentially more accurate than a Breathalyzer, and it doesn’t require the user to visit a clinic like a blood test. There are also some new temporary tattoo-based alcohol sensors, but these are only single-use, and can easily be removed.
One of the most challenging parts of the development process was simply the size of the chip, Hall says.
“This chip is really small and it is hard to work with,” he says. “Despite having a lab full of equipment for my other research projects, we had to buy several pieces of highly specialized equipment for this project simply due to the size and handling constraints.”
The next step will be to improve the lifetime of the sensor. There are some types of sensors, like continuous glucose monitors, that can last about two years, and the team hopes to achieve a similar lifespan. Over the next few years, the team will carry out animal studies, and then hopefully move on to human trials.
According to the National Institute on Alcohol Abuse and Alcoholism at the National Institutes of Health, about 15.1 million American adults ages 18 and older have alcohol use disorder. This includes about 8.4 percent of men and 4.2 percent of women. About 88,000 Americans die from alcohol-related causes each year, including nearly 10,000 killed in drunk driving accidents.
"I believe that alcohol monitoring systems only have a use if they are a small part of a support plan for people trying to recover from alcohol addiction," says Mike Delaney, an addiction counselor who has worked with rehabilitation programs in the UK and elsewhere.
Delaney thinks the systems are best used as part of a rehabilitation program, not as punishment.
"My concern about the implantable device is that it becomes a legal deterrent against people who have committed alcohol or drug related crimes and is used as part of a sentence thereby becoming punishment rather than treatment," he says. "Addiction needs to be treated as a health issue and not a criminal issue."