Tiny injectable sensor for long-term alcohol monitoring

Scientists have developed a miniature, ultra-low power injectable biosensor that could be used for continuous, long-term alcohol monitoring.

The chip developed by engineers at the University of California San Diego in the US is small enough to be implanted in the body just beneath the surface of the skin.

It is powered wirelessly by a wearable device, such as a smartwatch or patch.

"A tiny injectable sensor - that can be administered in a clinic without surgery - could make it easier for patients to follow a prescribed course of monitoring for extended periods of time," said Drew Hall, a professor at the UC San Diego.

Breathalysers, currently the most common way to estimate blood alcohol levels, are clunky devices that require patient initiation and are not that accurate, Hall noted.

A blood test is the most accurate method, but it needs to be performed by a trained technician.

The new biosensor chip measures roughly one cubic millimetre in size and can be injected under the skin in interstitial fluid - the fluid that surrounds the body's cells.

It contains a sensor that is coated with alcohol oxidase, an enzyme that selectively interacts with alcohol to generate a byproduct that can be electrochemically detected.

The electrical signals are transmitted wirelessly to a nearby wearable device such as a smartwatch, which also wirelessly powers the chip.

Two additional sensors on the chip measure background signals and pH levels. These get cancelled out to make the alcohol reading more accurate.

The researchers designed the chip to consume as little power as possible - 970 nanowatts total, which is roughly one million times less power than a smartphone consumes when making a phone call.

"The ultimate goal of this work is to develop a routine, unobtrusive alcohol and drug monitoring device for patients in substance abuse treatment programs," said Hall.