Compact Wearable “Lab on the Skin” Continuously Monitors Glucose, Alcohol and Lactate

Imagine being able to check your muscular tiredness during an exercise while also monitoring your blood sugar levels. Engineers from the University of California, San Diego (UCSD) have created a prototype of such a wearable that can monitor many health data in real time, including glucose, alcohol, and lactate levels.

The multi-tasking gadget is roughly the size of six quarters stacked together. It's applied to the skin with a Velcro-like patch of minuscule needles, or microneedles, each approximately the width of a human hair. The gadget is not uncomfortable to use since the microneedles only pierce the skin's surface to detect biomolecules in the interstitial fluid, which is the fluid that surrounds the cells underneath the skin. The gadget is worn on the upper arm and delivers data to a special smartphone app via Bluetooth.

Researchers at the UC San Diego Center for Wearable Sensors describe their technology in a paper published on May 9 in the journal Nature Biomedical Engineering.

“This is like a complete lab on the skin,” said center director Joseph Wang, a professor of nanoengineering at UC San Diego and co-corresponding author of the paper. “It is capable of continuously measuring multiple biomarkers at the same time, allowing users to monitor their health and wellness as they perform their daily activities.”

Most commercial health monitors just measure one signal, such as continuous glucose monitors for diabetic patients. The problem, according to the researchers, is that it leaves out information that may help patients manage their diseases more successfully, such as diabetes. Because drinking alcohol lowers glucose levels, monitoring alcohol levels is beneficial. Knowing both levels can help diabetics avoid dangerously low blood sugar levels after consuming alcohol. Because physical activity affects the body's capacity to control glucose, combining information regarding lactate, which can be assessed during exercise as a biomarker for muscle tiredness, is also relevant.

“With our wearable, people can see the interplay between their glucose spikes or dips with their diet, exercise, and drinking of alcoholic beverages. That could add to their quality of life as well,” says Farshad Tehrani, a nanoengineering Ph.D. student in Wang’s lab and one of the co-first authors of the study.

Microneedles merged with electronics

The wearable consists of a microneedle patch connected to a case of electronics. Glucose, alcohol, and lactate react with different enzymes on the tips of the microneedles in the interstitial fluid. Small electric currents are generated by these reactions, which are examined by electronic sensors and remotely transmitted to an app built by the researchers. On a smartphone, the findings appear in real time.

The disposable microneedle patch detaches from the reusable electronic case.

Microneedles have the benefit of sampling the interstitial fluid directly, and studies have demonstrated that biochemical levels measured in that fluid correspond well with blood levels.
“We’re starting at 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-corresponding author of the paper. “That lowers the barriers to clinical translation.”

The disposable microneedle patch may be easily replaced by separating it from the electronic enclosure. The battery, electronic sensors, wireless transmitter, and other electronic components are all housed in the electronic casing, which is reusable. Any wireless charging station for phones and smartwatches may be used to charge the gadget.

The device can be recharged on an off-the-shelf wireless charging pad.

One of the team's main problems was combining all of these components into a compact, wireless wearable. Combining the reusable electronics, which must keep dry, with the microneedle patch, which is exposed to biological fluid, requires some innovative design and engineering.
“The beauty of this is that it is a fully integrated system that someone can wear without being tethered to benchtop equipment,” UC San Diego Center for Wearable Sensors co-director Mercier remarked.


The wearable was put to the test on five volunteers who wore it on their upper arm while exercising, eating, and drinking wine. The subjects' glucose levels, as well as their alcohol and lactate levels, were continually monitored using the gadget. The device's glucose, alcohol, and lactate measures were very close to those obtained in the lab using a commercial blood glucose monitor, a Breathalyzer, and blood lactate tests.

Next steps

Farshad Tehrani and Hazhir Teymourian, another co-first author and a former postdoctoral researcher in Wang's group, co-founded AquilX to further develop the technology for commercialization. The next stage is to see how long the microneedle patch can endure before needing to be replaced. The idea of adding more sensors to the gadget to monitor medicine levels in patients and other health signals excites the firm.
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