(153e) Paper Microfluidic Based Wearable Patches for Biomarker Sensing in Sweat

Our group has introduced a simple and efficient platform for sweat sampling and handling based on osmotic-capillary principles and paper microfluidics. This innovative platform can harvest sweat noninvasively, even without active perspiration, through a combination of osmosis, capillary wicking, and evaporation. The hydrogel disk containing concentrated solute interfaces with the skin to enable osmotic sweat withdrawal, which is then transported via a paper strip using capillary wicking and disposed of on an evaporation pad. We have applied these principles to develop a range of simple and cost-effective wearable skin patches for analyzing potassium, lactate, and cortisol levels, based on lateral flow assays (LFAs). Potassium is a crucial intracellular electrolyte, and small variations in its range can cause serious health issues such as cardiac arrest. Our LFA platform uses a silicone and paper microfluidic conduit attached to a commercial K+ strip, and a polyacrylamide hydrogel with a higher osmotic strength than sweat. In-vitro testing on gelatin-based model skin allowed us to calibrate the platform with model sweat, and human trials have shown that it can detect K+ levels from human skin with very low sweat volumes (~2-3 µL) under moderate exercise and rest conditions. We have also demonstrated that our patch can efficiently sample sweat lactate, an essential biomarker for monitoring anaerobic metabolism, oxidative stress levels, muscle health, and tissue hypoxia in individuals. On-skin testing of the platform on both resting and exercising human subjects confirms that the patch can extract sweat and analyze changing lactate levels, which increase with exercise and muscle activity. Additionally, we are working on interfacing the paper platform with electrochemical sweat lactate sensors, allowing for long-term continuous electronic readout of results from the wearable interface. We are also developing wearable skin LFAs for detection of cortisol as a key stress biomarker in individuals, soldiers, athletes, and emergency personnel. The non-invasive wearable patches that we have developed can enhance affordable advanced healthcare, by eliminating the need to visit medical centers for biomarker-based diagnostics. These simple, facile, and inexpensive patches could allow numerous opportunities for at-home or in-field POC diagnostics.