Engineers at the University of California San Diego have developed a miniature, ultra-low power injectable biosensor that could continuously monitor alcohol levels for patients suffering from alcohol addiction.
The chip, which is small enough to be implanted in the body just beneath the surface of the skin, is powered wirelessly by a wearable device such as a smart watch or patch.
“The ultimate goal of this work is to develop a routine, unobtrusive alcohol and drug monitoring device for patients in substance abuse treatment programmes,” said UC San Diego School of Engineering professor Drew Hall, who led the project.
Hall, who presented the work at the 2018 IEEE Custom Integrated Circuits Conference (CICC) in San Diego, believes that it would offer benefits for patients in treatment programmes over the traditional ‘clunky’ breathalysers, which are not always accurate and require patient initiation.
While some commercial sensors use a wearable device and a smartphone app to track alcohol levels, taking readings from the surface of the skin is not as accurate as a blood test and the device could be removed by patients.
“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 Hall.
Measuring around one cubic millimetre, the biosensor can be injected under the skin into the fluid that surrounds the body’s cells, known as interstitial fluid. When the sensor, which is coated with alcohol oxidase, detects alcohol, it generates a by-product that can be electrochemically detected.
These electrochemical signals are transmitted wirelessly to a nearby wearable device, such as a smart watch. The wearable device also wirelessly powers the sensor, which consumes just 970 nanowatts—roughly one million times less power than a smartphone consumes during a phone call.
“We don’t want the chip to have a significant impact on the battery life of the wearable device. And since we’re implanting this, we don’t want a lot of heat being locally generated inside the body or a battery that is potentially toxic,” said Hall.
The chip is yet to be tried on humans and has only been tested in vitro. The researchers are planning to test the chip in live animals and are working with start-up CARI
Therapeutics and addiction psychiatrist at UC San Dr Carla Marienfield to optimise the chip for next-generation rehab monitoring.
Hall and his team are also developing versions of the chip that could monitor other drugs in the body.
“This is a proof-of-concept platform technology. We’ve shown that this chip can work for alcohol, but we envision creating others that can detect different substances of abuse and injecting a customised cocktail of them into a patient to provide long-term, personalised medical monitoring,” said Hall.