Sweat the Small Stuff

Today’s wearable health monitors are packed with everything from accelerometers and gyroscopes to photoplethysmography and electrophysiological sensors to capture all sorts of health-related metrics. Sweat sensing is an emerging area in the field, yet it has not caught on to the same extent that other technologies have. Despite the fact that sweat contains valuable information about athletic performance and conditions like diabetes, sepsis, and organ failure, these sensors are not always entirely practical for every use case.

The problem is that, for consumer-grade equipment, few people want to work up a sweat to collect health data. And when it comes to seriously ill individuals using medical-grade devices, they may not be able to produce enough sweat to meet the thresholds required by the sensor. But now, a better sensing option may be on the way. A group of researchers at Penn State University has developed a compact, wearable sweat sensor that can do more with less. Its novel design allows it to make accurate measurements with minuscule amounts of sweat.

The device, about the size of a band-aid, uses a unique combination of materials and microfluidics to capture up to ten times more sweat under low-intensity conditions than previous designs. That means it can gather enough fluid to analyze even while a person is sitting at a desk, walking casually, or even just resting. By targeting lactate, a biomarker that indicates how the body breaks down sugars for energy, the sensor offers insights into both athletic performance and certain serious medical conditions. Elevated lactate levels, for example, can serve as an early warning sign of sepsis or organ failure.

To bring this system to life, the team replaced the standard hydrogel material that is typically used in sweat sensors with what they call a granular hydrogel scaffold. Unlike conventional gels that can lose liquid during collection, this scaffold is made of interlinked microscale particles, creating tiny void spaces that encourage capillary action. Much like how plants draw water from their roots to their stems, the system wicks up sweat efficiently, even at the extremely low rates produced at rest.

Once collected, the sweat moves into a spiral-shaped microfluidic channel patterned with laser-induced graphene. This design increases surface area, improves fluid transport, and minimizes sample loss. Within the chamber, the sweat interacts with a sensor modified to detect lactate with high accuracy. By integrating a pH sensor as well, the platform accounts for natural variations in sweat chemistry, improving reliability over time.

By swapping out the sensing element, the same platform could be used to monitor indicators for other conditions, like diabetes, dehydration, or stress. This adaptability, combined with its comfort and low cost, positions the technology as a candidate for everyday health monitoring in the future, not just in specialized athletic or clinical settings.