Vertical textile microfluidics: advancing on-garment sweat sampling for real-time biosensing

The identification of novel physiological biomarkers in sweat requires real-time sampling and analysis. Here, we present the microfabrication of epidermal microfluidics within textiles via stereolithography (SLA) 3D printing. Flexible SLA resin defines impermeable fluid-guiding microstructures in textile microfluidic modules. Their vertical stacking reduces device footprint and required sample volume, and facilitates on-body fluid collection, storage, and transport. Embedded internal modules act as a reservoir and injection valve, releasing a defined volume of sweat to the sensing unit. The pressure gradient across the modules provides a vertically distributed, capillary-driven sweat flow, guided by the wicking power of the textile structure. Their full integration into apparels offers non-cumulative flow through an extended air-liquid interface, ensuring continuous sweat transfer and evaporation. For real-time sweat analysis, we use a remotely screen-printed potassium (K+) ion detector. This modular approach provides fabric-integrated, mechanically ergonomic microfluidics with multi-parameter detection through rapid additive manufacturing for advanced point-of-care diagnostics.