Electronic Tattoo Measures Blood Alcohol Level

Blood-alcohol measurement patch (University of California, San Diego)

3 August 2016. A flexible electronic device worn on the skin like a tattoo can assess blood alcohol level and transmit the results to a nearby mobile phone. Engineers from the labs of Joseph Wang and Patrick Mercier at University of California in San Diego describe their device in a recent issue of the journal ACS Sensors (paid subscription required). Wang and Mercier are director and co-director respectively of the university’s Center for Wearable Sensors.

The UC-San Diego team is seeking more reliable and fool-proof methods for monitoring the level of alcohol in the blood, an issue with implications for public health and safety. Today’s standard testing technology is the breathalyzer, which can return false results if administered immediately after taking a drink or using mouthwash to mask the exhaled alcohol.  A pinprick drop of blood provides more accurate measurements, but is medically invasive and difficult to administer for police officers at a traffic stop.

Researchers from Wang’s nanobioelectronics lab and Mercier’s  microsystems group took a different approach to the problem, focusing on indicators of alcohol content in perspiration, which can provide real-time measurement. Up to now, devices for measuring blood alcohol levels in perspiration were not portable or easy to wear. In addition, the device needs to work even if the person wearing it is not perspiring from exercise or other reasons.

To meet these requirements, the UC-San Diego team devised a wearable patch with both the ability to induce perspiration where worn on the skin and the electronics to measure the blood alcohol levels, as well as transmit the data to a receiver nearby.  The patch has a thin layer of hydrogel, a water-based polymer material, containing pilocarpine, a drug given to treat dry mouth, a condition caused by an autoimmune disorder or a result of X-ray treatments for head and neck cancer. In this case, the moisture-generating properties of the drug are directed into the skin by a mild electric current to induce sweat.

The patch contains electrodes coated with an enzyme, which in the presence of ethanol — the chemical name for alcohol in drinks — reacts to form hydrogen peroxide. Electrodes with a compound called Prussian Blue detect the hydrogen peroxide, and send electric signals through circuitry in the patch, then transmitted to an external device via Bluetooth links. A smartphone app, written in Mercier’s lab, analyzes and displays the results.

The researchers evaluated a prototype of the patch in a proof-of-concept test with 9 healthy volunteers, taking measurements of blood alcohol content before and after consuming 1 beer or a glass of wine. The before-and-after measurements show the device can record differences in blood alcohol content, even when the the device was bent or shaken, which suggests it could be used in practical day-to-day situations.

“Lots of accidents on the road are caused by drunk driving,” says Wang in a university statement. “This technology provides an accurate, convenient, and quick way to monitor alcohol consumption to help prevent people from driving while intoxicated.”He adds that the device could be integrated into a car’s ignition interlock, or even just alert friends that a person is too drunk to drive.

The team plans to increase its alcohol-monitoring capability to 24 hours, as well as expand the platform to measure other types of biochemical reactions.

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