Non-Invasive Glucose Monitoring Watch

Non-Invasive Glucose Monitoring Watch

A multidisciplinary Chinese team just published the results of an exciting small trial involving a

new smartwatch used for non-invasive blood glucose monitoring in the prestigious journal Nature.

The watch resulted from a collaboration between the Beijing Advanced Innovation Center for

Biomedical Engineering and the Department of Biomedical Engineering, City University of Hong Kong.

Thirteen diabetic patients between the ages of 40 and 60 were recruited from the China-Japan

Friendship Hospital, while ten non-diabetic students between the ages of 20 and 40 from the Beihang

University's campus served as control.

According to the Clarke error grid study (zones A and B), the watch achieved clinical accuracy of

84.34 percent. These results are still far from acceptable to justify commercial use, but they

somehow demonstrate that blood-glucose monitoring without the hassle of finger pricking is gaining

traction.

We recently highlighted the two Japan-made technologies presented during CES-2022 that also are on

the search for continuous and non-invasive blood glucose monitoring.

What is the technology being the Chinese Blood Glucose Monitoring Watch?

In the recent decade, significant research efforts have been directed toward developing non-

invasive technologies to monitor glucose levels and other biomarkers continuously. For example,

biofluids such as sweat, saliva, tear, or cellular interstitial fluid (ISF) contain various

substances (e.g., lactate, uric acid, sodium, and potassium) that can be used to assess glucose

levels.

Sweat analysis proved impractical to sample and analyze despite being readily available, especially

in elderly or sick patients.

On the other hand, Skin ISF is a consistently and abundantly present biofluid independent of

environmental circumstances. It diffuses from the blood capillaries and delivers nutrients,

including glucose, to the surrounding cells, establishing a solid association between blood and ISF

glucose levels. As a result, it is increasingly being used as a source of biomarkers in medical

diagnostics and treatment.

The watch includes an LED screen for result display, a printed circuit board (PCB) for signal

processing and transmission, a rechargeable battery for power supply, and a flexible glucose sensor

patch that is fixed to the watchband and is used to detect glucose in the ISF obtained through

transdermal extraction. In addition, a calibration technique was introduced to the data processing

of the watch to improve the accuracy of glucose measurement.

Principles of the sensors used for blood-glucose

MEMS technology was used to build the flexible glucose sensor patch attached to the watchband and

adheres to the wearer’s skin. The patch is made of a 100-micron-thick polyimide (PI) film, is

Nafion-coated, and is waterproof.

Specifically, there are two glucose sensors in the patch, with each sensor consisting of an active

electrode, a reference electrode, and a counter electrode.

Furthermore, each sensor is enclosed by a pair of extraction electrodes used to collect ISF from

the skin in a non-invasive way. Transdermal biomarkers are acquired via reverse iontophoresis, and

the nearby sensors detect blood glucose levels. The extraction and analysis process takes 17

minutes on average, meaning the potential to acquire 4 data points per hour. This fast processing

method is especially interesting in measuring postprandial glucose levels.

Results and next steps

During the initial testing phases, the watch was considered non-intrusive and comfortable to use by

the volunteers who tested it. Even though an 84% accuracy compared to standard finger-pricking

methods is not enough to replace standard blood glucose measurement methods, the results and

technology are exciting.

Using a Nafion-coated flexible electrochemical sensor patch fixed on the watchband to obtain

interstitial fluid (ISF) transdermally proved a promising technology.

With 463 million adults worldwide suffering from diabetes, according to the 2019 report from the

International Diabetes Federation, non-invasive blood glucose measurements technology developments

are in the spotlight.

We suspect that wearable devices will soon be clinically validated and be readily available to

change the way people with diabetes manage the disease daily. This study is just one of many that

proved that technology is now close to being reliable enough to offer a non-painful, non-intrusive

alternative for measuring blood glucose continuously.