Engineers at the University of California, San Diego, have developed a prototype smart ring that uses osmotic hydrogel to passively extract and analyze finger sweat, simultaneously tracking up to four biochemical markers, including glucose, ketones, and alcohol, without requiring physical exertion.
Beyond Biophysical Metrics: Monitoring Molecular Health Through Sweat
Wearable health technology has long relied on biophysical sensors, such as photoplethysmography light sensors, to capture surface metrics like heart rate and blood oxygen levels. While popular commercial rings focus on movement, sleep stages, and vital signs, they lack molecular insight into the body’s internal chemistry. To bridge that gap, researchers in the lab of Joseph Wang at the UC San Diego Jacobs School of Engineering designed a wearable device dedicated entirely to biochemical monitoring.
The prototype device is formally known as the Continuous Health Analyzing Ring Module, or CHARM. As medindia.net reported, the ring can detect six biomarkers in total—glucose, ketones, vitamin C, uric acid, lactate, and alcohol—while continuously measuring up to four of them simultaneously in real time. This capability gives researchers and wearers a direct window into metabolic changes that episodic blood tests often miss.
“Commercial rings only provide biophysical information, but they lack molecular information about biochemical markers that offers deeper insights about an individual’s health status.”
Tamoghna Saha, postdoctoral researcher in Wang’s lab at UC San Diego, via CNET
How Osmotic Extraction Pulls Sweat Without Exertion
Traditional sweat sensors typically require a rigorous workout or physical exertion to produce a usable biological sample. The CHARM prototype bypasses that limitation entirely through a specialized passive collection mechanism.
The system relies on an osmotic hydrogel, a soft polymer developed specifically by the research team to create a pain-free pressure gradient that draws fluid directly from the skin. According to earth.com, this osmotic extraction method gathers roughly five to six times more fluid than the skin naturally produces at that location on its own, operating smoothly while the wearer sits completely still.
Once the hydrogel collects the sample, an electrochemical sensor array inside the device analyzes the fluid. Through repeated measurements, the system establishes subject-specific calibration factors that convert raw electrical current readings into concentration values.
Clinical Validation and Diabetes Management Potential
To verify the accuracy of the ring, researchers conducted trials involving healthy volunteers and individuals managing type 1 diabetes. During these evaluations, the smart ring’s glucose readings closely matched data gathered from commercial continuous glucose monitors, while its ketone measurements tracked alongside commercial blood meters.
“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.”
Joseph Wang, professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering, via CNET
Hardware Architecture and Engineering Constraints
Packing biochemical sensing arrays, microfluidic channels, and wireless transmitters into a ring form factor required creative engineering. The outer shell consists of a 3D-printed polymer measuring an external diameter of about 3 centimeters (1.2 inches), with the internal electronic board engineered to be smaller than a US quarter coin, as outlined by UC San Diego Today.
The device is built in two connected halves: one housing the sweat extraction and sensor array, and the other containing a flexible zinc-silver oxide rechargeable battery linked by a connector pad. As noted by CNET, that custom battery currently delivers up to 12 hours of operation between charges—leaving substantial room for improvement when compared to commercial biometric rings that boast multi-day or multi-week battery life.
Next Steps for Molecular Wearables
The research paper detailing the technology was published in Nature Communications. The project received financial support from the UC San Diego Center of Wearable Sensors and the National Science Foundation – UC San Diego Materials Research Science and Engineering Center.
While the CHARM device remains a laboratory prototype, the underlying work demonstrates that continuous, non-invasive molecular tracking is technically feasible. As engineering teams continue to shrink electronics and extend battery performance, wearable health technology may soon expand from simple step counts and heart rates to comprehensive daily metabolic oversight.
