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Alcohol sensor tattoo alerts smartphone when user is over the limit

A flexible alcohol-detecting wearable sensor that accurately measures blood alcohol levels from sweat and transmits the data wirelessly to a smartphone app has been developed by California engineers.

The device can be worn on the skin and could be used by doctors and police officers for continuous, non-invasive and real-time monitoring of blood alcohol content.

The data transmitted can be received and processed by a laptop, smartphone or other mobile device to build up a picture of the wearer’s alcohol consumption.

The device consists of a temporary tattoo, which sticks to the skin, induces sweat and electrochemically detects the alcohol level. A portable and flexible electronic circuit board, which is connected to the tattoo by a magnet, can then communicate the information to a mobile device via Bluetooth.

The tattoo is equipped with screen-printed electrodes and a small hydrogel patch containing pilocarpine, a drug that passes through the skin to induce sweat.

The circuit board has a magnetic connector that attaches it to the tattoo to power it and it can wirelessly communicate the information received to a nearby mobile device.

The work was led by nano-engineering professor Joseph Wang at the University of California San Diego and electrical engineering professor Patrick Mercier.

"Lots of accidents on the road are caused by drunk driving. This technology provides an accurate, convenient and quick way to monitor alcohol consumption to help prevent people from driving while intoxicated," Wang said.

The device could be integrated with a car's alcohol ignition interlocks or friends could use it to check up on each other before handing over the car keys, he added.

"When you're out at a party or at a bar, this sensor could send alerts to your phone to let you know how much you've been drinking," said Jayoung Kim, one of the device’s developers.

Blood alcohol concentration is the most accurate indicator of a person's alcohol level, but measuring it requires pricking a finger.

Breathalyzers, which are the most commonly used devices to indirectly estimate blood alcohol concentration, are non-invasive, but they can give false readouts.

For example, the alcohol level detected in a person's breath right after taking a drink would typically appear higher than that person's actual blood alcohol concentration. A person could also fool a breathalyser into detecting a lower alcohol level by using mouthwash.

Recent research has shown that blood alcohol concentration can also be estimated by measuring alcohol levels in what's called insensible sweat, perspiration that happens before it's perceived as moisture on the skin.

This measurement can be up to two hours behind the actual blood alcohol reading. On the other hand, the alcohol level in sensible sweat, the sweat that's typically seen, is a better real-time indicator of the blood alcohol concentration, but so far the systems that can measure this are neither portable nor fit for wearing on the body.

This newly developed sensor is both portable and can accurately monitor alcohol level in sweat within 15 minutes.

"What's also innovative about this technology is that the wearer doesn't need to be exercising or sweating already. The user can put on the patch and within a few minutes get a reading that's well correlated to his or her blood alcohol concentration. Such a device hasn't been available until now," Mercier said.

Researchers tested the alcohol sensor on nine healthy volunteers who wore the tattoo on their arms before and after consuming an alcoholic beverage (either a bottle of beer or glass of red wine). The readouts accurately reflected the wearers' blood alcohol concentrations.

In May, an alcohol monitoring device that can be worn on the wrist won a US government-sponsored competition that awards wearable technologies that monitor and diagnose medical conditions. 

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