Researchers at the University of Oulu have come up with a wearable, noninvasive glucose sensor. It checks glucose levels from human sweat.
They built an optical watch prototype by integrating plasmonic silicon nanopillar sensors. The team coated these nanopillars with a thin layer of silver. The system uses red-light illumination and a photodiode, then sends data wirelessly over Bluetooth.
Let’s look at how this thing actually works.
Technology behind the wearable optical glucose-sensing system
The platform uses plasmonic silicon nanopillars, each covered with silver. On top of that, every nanopillar gets functionalized with 4-mercaptophenylboronic acid.
This molecule grabs onto glucose using its cis-diol structure. That binding changes the local optical environment around the pillar, which leads to measurable shifts in the reflected light intensity. There’s no need for enzymes or fluorescent labels here.
Silver, not gold, was chosen for the coating. The reason? Silver gives sharper localized surface plasmon resonance (LSPR), which bumps up sensitivity.
The detection limit lands at about 22 μmol/L. That’s right in the range you’d expect for glucose concentrations in sweat.
The team tweaked the sensing performance using Raman spectroscopy and plasmonic reflectance measurements. These adjustments helped keep the sensor sensitive and selective, even with other stuff mixed into sweat.
How the sensing mechanism translates to readouts
When the device runs, red-light illumination hits the plasmonic nanopillars. As glucose binds to the capture layer, the reflected light intensity shifts.
A compact photodiode keeps track of those changes. The device then sends the data by Bluetooth to a connected device for easy monitoring.
This optical watch is meant to be low-power and modular. It should feel comfortable for long-term wear and is less likely to irritate skin compared to subcutaneous sensors.
The researchers showed that this approach works without enzymes or fluorescent labels. That cuts out a lot of complexity and possible failure points.
The readout is set up for real-time data streaming. You could use it for continuous monitoring during daily activities, workouts, or exercise.
Performance, validation, and comfort
The system balances sensitivity, specificity, and user comfort. The optical design doesn’t use much power, so you can wear it for a long time.
Since it reads sweat instead of piercing the skin, it’s a lot more comfortable than traditional methods.
Real-world validation and readouts
The team tested the sensor with artificial sweat and with samples from volunteers during exercise. In both cases, the wearable tracked sweat glucose in real time.
Results matched up well with conventional enzymatic measurements. The sensor held up against common sweat interferences, which suggests it could work for daily use in real life.
Future directions and impact
This modular sensing strategy already shows real promise for tracking more than just glucose. There’s potential to expand into other sweat biomarkers like lactate, electrolytes, or even stress-related metabolites.
The researchers are looking to add automated sweat stimulation and microfluidics, aiming for a fully autonomous “lab-on-a-watch.” They’ll need more clinical validation to see how it holds up across different people and activities.
- Noninvasive, continuous glucose monitoring from sweat
- Enzyme-free detection using cis-diol binding to boronic acid
- Sharper LSPR achieved with silver-coated plasmonic nanostructures
- Low-power, wearable optical readout and wireless data transmission
- Platform can adapt to track multiple sweat biomarkers for broader health monitoring
Support for this work came from Tandem Industry Academia, DigiHealth, and the Academy of Finland. They published the findings in Microsystems & Nanoengineering (DOI: 10.1038/s41378-025-01152-6).
If this approach scales up, it might just change how we think about continuous, noninvasive glucose monitoring—and maybe even the whole field of sweat-based analytics in wearables.
Here is the source article for this story: From Sweat to Signal: A Wearable Optical System for Glucose Detection