A Tattoo That Knows When You’re Drunk (Additional Coverage)

Source: wsj.com

Daniel Akst

Aug. 11, 2016

Sometimes, after a few drinks, people get a tattoo. Now there’s a tattoo that can tell if you’ve had a few drinks. Best of all, it’s temporary.

Researchers at the Center for Wearable Sensors at the University of California, San Diego, have come up with a removable electronic tattoo that can sense your blood-alcohol level from the sweat on your skin and then send this information via Bluetooth to a smartphone or car computer.

The UCSD device is part of a boom in wearable sensors of all kinds-a surge enabled by the rise of smartphones, which can keep track of the data these sensors produce.

Scientists have been particularly interested in alcohol monitoring. Breathalyzer devices don’t offer continual monitoring, and their results can be skewed by mouthwash, for example, or alcohol residue in saliva. Wearable devices that passively detect alcohol in sweat from the user’s skin-which are sometimes mandated by judges and have been known to crop up in embarrassing photos of celebrities-can offer continuous monitoring, but the gadgets tend to be bulky and expensive.

In May, the National Institute on Alcohol Abuse and Alcoholism (part of the National Institutes of Health) announced the winner of its Wearable Alcohol Biosensor Challenge, which it launched in 2015 to promote innovation. The first prize, of $200,000, was awarded to a bracelet-type device made by San Francisco-based firm called BACtrack, a pioneer of consumer-oriented breathalyzers, some of which already work with smartphones.

BACtrack’s founder and chief executive officer, Keith Nothacker, says that the firm is working on algorithms to derive accurate blood-alcohol results from ethanol detected on the skin. But for many users, he noted, the main question will be whether there is any sign of alcohol use at all. A positive result could be communicated to a spouse, sobriety mentor or probation officer, for example, since the device can relay its findings to a smartphone via Bluetooth. Mr. Nothacker says that he hopes to distribute prototypes of the BACtrack Skyn-the prize-winning sensor-in the months ahead and then bring it to market for around $99, eventually offering a version that serves as a band for the Apple Watch.

The Skyn relies on “insensible” sweat, or trace amounts that you don’t even know you have. In an effort to get fast, accurate results with a one-time test while avoiding the pitfalls of breathalyzers, the UCSD device goes another route: It contains a small amount of pilocarpine, a medication normally used to treat dry mouth and other health problems. Applied topically, the drug induces a little sweat where the device’s electrodes can use it, letting the sensor get results in about 15 minutes.

The UCSD tattoo is attached to a flexible, inch-long circuit board for processing and relaying data. But Joseph Wang, one of the project scientists, says that the reusable board could probably be made much smaller with some additional engineering. He adds that the disposable tattoos cost just pennies to produce, and his lab is working on a version that works all day.

Cheap, reliable alcohol monitoring through the skin could have a variety of applications. Computers in cars could lock the ignition if they detected a reading above a worrisome threshold, especially if a motorist has had a drunken-driving conviction. Bartenders could use the sensors to tell when it’s time to cut off a customer. Or for people concerned about their own drinking, wearing the monitoring device could offer passive intake recording that is probably more accurate than memory-and not subject to fudging.

“Noninvasive Alcohol Monitoring Using a Wearable Tattoo-based Iontophoretic-Biosensing System,” Jayoung Kim, Itthipon Jeerapan, Somayeh Imani, Thomas N. Cho, Amay Jairaj Bandodkar, Stefano Cinti, Patrick P. Mercier and Joseph Wang, ACS Sensors (July 12)