Sweat is an appealing medium for health monitoring because it is readily available and contains multiple biomarkers. However, most existing devices fail when perspiration is minimal, which limits their use in critically ill patients or individuals at rest. This makes it difficult to track key biomarkers such as lactate, which can indicate oxygen deprivation in tissues, a warning sign for conditions like sepsis, organ failure, or poor athletic performance. Now, a novel wearable sensor can continuously monitor low rates of perspiration for the presence of lactate, a molecule used by the body to break down sugars for energy.

The new wearable sensor has been developed by researchers at Penn State (University Park, PA, USA) to work under low-sweat conditions. The device, about the size of a band-aid, uses granular hydrogels combined with laser-induced graphene (LIG) patterned into a compact spiral microfluidic chamber. This design increases absorption capacity, minimizes liquid loss, and ensures lactate molecules reach the sensor even when sweat production is extremely low.

Unlike conventional hydrogels, the granular hydrogel scaffold features porous microscale particles with void spaces that enhance capillary-driven absorption. This allows the device to collect up to 10 times more sweat during low-intensity activities such as walking, working at a desk, or even lying down. Attached comfortably with skin-safe adhesive, it mimics a “skin-like” feel and enables continuous, non-invasive monitoring.

In trials, the flexible sensor was applied to participants during daily activities, sedentary office work, and exercise. The results, published in the journal Small, showed the device could consistently capture enough sweat to measure lactate within two hours. This proof-of-concept confirmed the accuracy, sensitivity, and practicality of the design, setting it apart from earlier sweat sensors that required more perspiration to function effectively.

The platform offers significant potential for early biomarker detection in both clinical and fitness settings. Its versatility means the sensor could be adapted to detect other biomarkers beyond lactate, providing broader applications in personalized health monitoring. Future research aims to refine the device and expand its use for continuous, real-time, and cost-effective health tracking across diverse populations.

“The proof-of-concept demonstration features a cost-effective, sensitive and versatile flexible sensing platform for early biomarker detection, where sweat production is minimal or sporadic, such as at rest or during mild physical activities,” said Farnaz Lorestani, co-first author of the study. “Overall, our goal is to build a healthier society by making non-invasive, continuous, personalized health monitoring more accessible to everyone — and this work is a step in that direction.”

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