Imagine being able, with a small device on your skin, to monitor your blood sugar levels and detect if you have had too much alcohol. Engineers at the University of California San Diego (UCSD) have developed a prototype of such a wearable that can continuously monitor several health stats–glucose, alcohol, and lactate levels–simultaneously in real-time. This multi-tasking device measures only six quarters in size. The microneedles are applied to the skin using a Velcro-like strip of microscopic needles. Each one-fifth of the width of a human’s hair is used. The device is comfortable to wear. The microneedles penetrate only the skin’s surface to detect biomolecules in the interstitial fluid. This is the fluid that surrounds the skin cells. The device can be worn on one’s upper arm. It sends data wirelessly through a smartphone app. It’s like a lab on the skin,” explained Joseph Wang, center director and professor of nanoengineering from UC San Diego. He is also co-author of the paper. It can continuously measure multiple biomarkers simultaneously, which allows users to monitor their health and wellbeing as they go about their day.

Commercial health monitors such as continuous glucose monitors to monitor patients with diabetes only measure one signal. Researchers said that this leaves out important information that could help patients with diabetes manage their disease better. Because alcohol consumption can lead to lower glucose levels, it is important to monitor alcohol levels. People with diabetes can monitor both levels to prevent blood sugar levels from dropping too low after drinking. Because exercise can affect the body’s ability regulate glucose, it is useful to combine information about lactate.

“With our wearable people can see the interplay of their glucose spikes and dips with diet, exercise, or drinking of alcohol. This could increase their quality of living,” Farshad Tehrani (a Ph.D. candidate in nanoengineering at Wang’s lab, and one of the cofirst authors of this study), said.

Electronics and microneedles fused

The wearable is made up of a microneedle-patch connected to an electronic case. The microneedle tips react with interstitial fluid to produce different enzymes. These reactions produce small electric currents that can be analyzed using electronic sensors. The results are then transmitted wirelessly to the app developed by the researchers. The results can be viewed on a smartphone in real-time.

Microneedles have the advantage of directly sampling interstitial fluid. Research has also shown that levels in this fluid are closely related to levels in blood.

Patrick Mercier, a professor at UC San Diego of electrical and computer engineering and co-author of the paper, said that “we’re starting from a really good position with this technology in terms clinical validity and relevant.” This lowers the barriers for clinical translation.

For easy replacement, the disposable microneedle patches can be removed from the electronic case. The electronic case is reusable and houses the battery, electronic sensor, wireless transmitter and other electronic components. You can recharge the device using any wireless charging pad for smartwatches and phones.

The team faced the greatest challenge in combining all of these components into a small wireless wearable. The combination of the reusable electronics that must remain dry with the microneedle patches, which are exposed to biological fluid, required clever engineering and design.

Mercier, who also serves as codirector of the UC San Diego Center of Wearable Sensors, said that “the beauty of this system is that it is a fully-integrated system that anyone can wear without being tethered or tethered”

Test

Five volunteers tested the wearable while they exercised, ate a meal and drank a glass of wine. The device was used continuously to monitor volunteers’ glucose levels and their alcohol and lactate levels. The device’s glucose, alcohol, and lactate measurements closely matched those taken by Breathalyzer (a commercial blood glucose monitor) and lab blood lactate tests.

Next steps

Farshad Tehrani, a co-first author, and Hazhir Teymourian (a former postdoctoral researcher at Wang’s lab), co-founded AquilX, a startup to further develop the technology for sale. Next steps will include improving the durability of the microneedle patches before they are replaced. The possibility of adding additional sensors to the device to monitor patient medication levels and other health signals is exciting to the company.