Sweat, a readily available resource rich in biomarkers, is increasingly recognized as a valuable medium for health monitoring by researchers at Penn State. However, many individuals, particularly critically ill patients, struggle to produce enough sweat for conventional analysis techniques.
This challenge may be overcome thanks to a new wearable sensor developed by the Penn State team. The device continuously measures low rates of perspiration for lactate—a molecule crucial for energy production in the body. Elevated lactate levels can signal tissue oxygen deprivation, significant for both athletes and those with severe conditions like sepsis or organ failure.
Published in the journal Small, the researchers have patented this device that resembles a bandage, capable of collecting up to 10 times more sweat during low-intensity activities compared to existing wearable sensors. This innovation offers promising solutions for non-invasive, real-time health monitoring.
Small"Sweat provides accessible biomarkers that allow us to monitor the body's performance and manage various health conditions with minimal discomfort," said co-first author Farnaz Lorestani, assistant research professor of engineering science and mechanics at Penn State.
"Our solution involves a novel platform using granular hydrogels developed by Professor Amir Sheikhi’s lab, capable of collecting sweat even during low-intensity activities like emailing or resting."
Professor Sheikhi is the co-corresponding author on this study, serving as the Dorothy Foehr Huck and J. Lloyd Huck Early Career Chair in Biomaterials and Regenerative Engineering at Penn State.
Under ordinary conditions with minimal activity, Lorestani explained that most people sweat from 10 to 100 nanoliters per minute per square centimeter of skin—a volume even smaller than a tear drop. Traditional devices use hydrogels combined with laser-induced graphene (LIG) sensors to uptake and analyze samples.
While LIG is highly sensitive, it encounters issues with very small sweat quantities due to liquid loss during the absorption process.
The researchers introduced two crucial adaptations: replacing typical hydrogels with a granular hydrogel scaffold of interlinked microgel particles, building on Sheikhi's prior work in regenerative biomaterials. Secondly, they integrated this scaffold into a compact spiral microfluidic chamber made from patterned LIG, enhancing fluid transport and minimizing loss.
This device collects sweat via an adhesive applied directly to the skin. The absorbed sweat is then transported through the granular hydrogel to the sensor that detects lactate presence specifically.
"We proposed that the pores within this granular scaffold increase absorption over previous hydrogel materials due to capillary action," explained Lorestani, likening it to water transport in plants' roots and stems.
Additionally, she noted, "The compact spiral design boosts accuracy and sensitivity."
The team designed the wearable device to be as comfortable as a standard bandage. Tests on individuals engaged in various activities from office work to cycling confirmed its ability to collect sufficient sweat for accurate lactate detection within two hours.
"Our proof-of-concept establishes a cost-effective, sensitive, and adaptable flexible sensor able to detect early biomarkers even with minimal sweat production," Lorestani emphasized, suggesting the technology could adapt for various biomarkers beyond lactate by modifying sensors accordingly.
The team aims to make non-invasive, continuous personalized health monitoring more widely accessible—a significant step towards building healthier societies.