Smart ring continuously tracks multiple health biomarkers from finger sweat

Engineers at the University of California San Diego created a smart ring that simultaneously and continuously monitors up to four different chemical biomarkers from finger sweat. The complete array of biomarkers the smart ring can monitor in sweat consists of: glucose, ketones, vitamin C, uric acid, lactate and alcohol.

In a new paper published in Nature Communications, UC San Diego engineers in the lab of Joseph Wang, professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering, report results from what they believe is the first fully integrated smart ring for daily biochemical monitoring.

"Commercial rings only provide biophysical information, but they lack molecular information about biochemical markers that offers deeper insights about an individual's health status," said study first author Tamoghna Saha, a postdoctoral researcher in Wang's lab.

For the ring to detect biomarkers in sweat, exercise or other exertion is not required; sweat is passively drawn up through the surface of the skin via osmosis using a technique pioneered by Saha.

Tracking multiple biomarkers simultaneously has the potential to broaden the real-time health picture in many different scenarios, including diabetes management and nutrition tracking.

"A ring capturing dynamic molecular information in real time would be extremely useful for making informed decisions regarding health, diet and lifestyle," said Wang. "For example, the ring's ability to track both glucose and ketone continuously and simultaneously would greatly benefit optimal insulin dosing for the management of diabetes."

In trials with healthy volunteers and people with type‑1 diabetes, the biomarker smart ring's glucose readings closely tracked those from commercial continuous glucose monitors (CGMs), while the ketone readings closely tracked ketone readings from commercial blood meters.

The biomarker smart ring is a fully integrated prototype that includes all the necessary biomarker sensing technology, low-power electronics and a flexible battery. Biomarker information is sent wirelessly to a smartphone app. The ring draws sweat passively using an osmotic hydrogel, a soft polymer that creates a pressure gradient to pull fluid from the skin painlessly. It works similarly to how water travels from soil to the leaves in plants. The collected sweat is analyzed by an electrochemical sensor array within the ring. Through repeated measurements, subject-specific calibration factors are established to convert current responses into concentration values. These calibration factors enable more personalized insight into the biomarker trends.

The ring is powered by a flexible zinc-silver oxide rechargeable battery that supplies power for up to 12 hours of operation between charges. The electronic board dimension ranges smaller than a US quarter coin. The outer shell of the smart ring is made from a 3D‑printed polymer. "Such integration onto the small footprint of a ring form factor is amazing," Wang said.