Compact wearable skin lab continuously monitors glucose, alcohol and lactate

Imagine being able to measure your blood sugar levels, know if you’ve been drinking too much alcohol, and track your muscle fatigue during a workout, all in one small device that wears on your skin. Engineers at the University of California, San Diego (UCSD) have developed a prototype of such a wearable device that can continuously monitor several health statistics – glucose, alcohol and lactate levels – simultaneously in real time.

The multitasking device is only the size of a pile of six quarters. It is applied to the skin using a velcro-like patch of microscopic needles or microneedles, each about one-fifth the width of a human hair. Wearing the device is not painful – microneedles barely penetrate the surface of the skin to sense biomolecules in the interstitial fluid, which is the fluid that surrounds the cells under the skin. The device can be worn on the upper arm and send data wirelessly to a personalized smartphone app.

Researchers from UC San Diego Center for wearable sensors describe their device in an article published today (May 9, 2022) in the journal Natural biomedical engineering.

The device can be worn on the upper arm and send data wirelessly to a personalized smartphone app. Credit: Nanobioelectronics Laboratory / UC San Diego

“It’s like a complete laboratory on the skin,” said center director Joseph Wang, a professor of nanoengineering at the University of California, San Diego and co-author of the article. “It is able to continuously measure multiple biomarkers simultaneously, allowing consumers to monitor their health and well-being as they go about their daily activities.

Most commercial health monitors, such as continuous glucose monitors for diabetics, measure only one signal. The problem with this, the researchers said, is that it misses information that could help people with diabetes, for example, manage their disease more effectively. Monitoring alcohol levels is helpful, as drinking alcohol can lower glucose levels. Knowing both levels can help people with diabetes prevent their blood sugar from falling too low after drinking. Combining lactate information that can be observed during exercise as a biomarker of muscle fatigue is also helpful, as physical activity affects the body’s ability to regulate glucose.

“With our wearable device, people can see the interaction between their jumps or falls in glucose with diet, exercise and drinking alcohol. It can also improve their quality of life, “said Farshad Tehrani, a doctor of nanoengineering. a student in Wang’s laboratory and one of the co-authors of the study.

Microneedles merged with electronics

The carrying device consists of a patch with a microneedle connected to an electronics box. Various enzymes on the tips of the microneedles react with glucose, alcohol and lactate in the interstitial fluid. These reactions generate small electrical currents that are analyzed by electronic sensors and communicated wirelessly to an application that researchers have developed. The results are displayed in real time on a smartphone.

The disposable microneedle patch is detached from the reusable electronic case. Credit: Nanobioelectronics Laboratory / UC San Diego

The advantage of using microneedles is that they take samples directly from the interstitial fluid, and research shows that the biochemical levels measured in this fluid correlate well with the levels in the blood.

“We’re starting in a really good place with this technology in terms of clinical validity and relevance,” said Patrick Mercier, a professor of electrical and computer engineering at UC San Diego and co-author of the article. “This lowers the barriers to clinical translation.”

The disposable microneedle patch can be detached from the electronic case for easy replacement. The reusable electronic case contains the battery, electronic sensors, wireless transmitter and other electronic components. The device can be recharged on any wireless charging pad used for phones and smart watches.

The device can be charged on a ready-made wireless charging pad. Credit: Nanobioelectronics Laboratory / UC San Diego

Integrating all of these components together into one small, wireless carrying device was one of the team’s biggest challenges. It also required clever design and engineering to combine reusable electronics that need to stay dry with a microneedle patch that is exposed to a biological fluid.

“The beauty of this is that it’s a fully integrated system that one can wear without being connected to desktop equipment,” said Mercier, who is also co-director of the UC San Diego Wearable Sensor Center.

Testing

The carrying device was tested on five volunteers who carried the device on their upper arm while training, eating food and drinking a glass of wine. The device is used to continuously monitor the glucose levels of volunteers at the same time as their alcohol or lactate levels. The measurements of glucose, alcohol and lactate made by the device largely coincide with the measurements made by the commercial blood sugar monitor, breathalyzer and blood lactate measurements performed in the laboratory, respectively.

next steps

Farshad Tehrani and his co-author Hajir Teymurian, a former postdoctoral fellow at Wang’s laboratory, co-founded a startup called AquilX to further develop commercialization technology. The next steps include testing and improving how long the microneedle patch can last before it is replaced. The company is also excited about the possibility of adding more sensors to the device to monitor patient drug levels and other health signals.

Reference: “Integrated carrier array of microneedles for continuous monitoring of multiple biomarkers in interstitial fluid” May 9, 2022, Natural biomedical engineering.
DOI: 10.1038 / s41551-022-00887-1

Funding: NIH / National Institute of Neurological Disorders and Stroke