A smart ring can continuously track up to four biomarkers in sweat at once, offering a possible way to monitor health in real time.
Developed by engineers at the University of California San Diego, the prototype can monitor combinations of glucose, ketones, vitamin C, uric acid, lactate and alcohol without the wearer having to exercise to produce sweat.
It sends biomarker data wirelessly to a smartphone app, allowing changes in the wearer’s levels to be followed throughout the day.
The San Diego team said they believe it is the first fully integrated smart ring developed 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 Tamoghna Saha, the study’s first author and a postdoctoral researcher in Joseph Wang’s laboratory.
Rather than relying on sweat produced during exercise, the ring passively draws fluid through the surface of the skin using osmosis, a process involving the movement of water through a barrier.
Researchers said tracking several biomarkers at the same time could provide a broader real-time picture of a person’s health, including for diabetes management and nutrition monitoring.
“A ring capturing dynamic molecular information in real time would be extremely useful for making informed decisions regarding health, diet and lifestyle,” said Joseph Wang, professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering.
“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 involving healthy volunteers and people with type 1 diabetes, glucose readings from the ring closely followed those from commercial continuous glucose monitors.
Continuous glucose monitors, known as CGMs, are wearable devices that repeatedly measure glucose levels.
The ring’s ketone readings also closely followed measurements from commercial blood meters.
The fully integrated prototype contains the biomarker sensors, low-power electronics and flexible rechargeable battery needed to operate as a single wearable device.
An osmotic hydrogel, a soft polymer, creates a pressure difference that draws sweat painlessly from the skin. The process is similar to water moving from soil to the leaves of a plant.
An electrochemical sensor array then analyses the collected sweat by measuring electrical responses associated with different chemicals.
Repeated measurements are used to establish calibration factors for each wearer. These convert the electrical responses into biomarker concentrations and provide more personalised information about changes over time.
The flexible zinc-silver oxide battery provides up to 12 hours of operation between charges.
Its electronic board is smaller than a US quarter, while the ring’s outer shell is made from a 3D-printed polymer.
“Such integration onto the small footprint of a ring form factor is amazing,” Wang said.
Image: David Baillot/UC San Diego Jacobs School of Engineering
