Vertical textile epifluidics for integrated real-time electrochemical sweat analysis

Abstract The non-invasive discovery of novel physiological biomarkers in sweat relies on its precise sampling and analysis. Here, we present a scalable fabrication approach of a wearable microfluidic system within fabric structures for an accurate and ergonomic sweat handling and sensing. Digital 3D printing of a flexible resin precisely defines impermeable microstructures in wicking textiles, only achievable by SLA technique. Regulated fluid collection, storage and transport, avoiding the complexity of traditional valves, is obtained by assembling 3D-printed textile-based modules in an origami-inspired vertical stack offering reduced device footprint, seamless and adhesive-free on-body sensing. The generation of pressure gradient across these microfluidic modules enables vertically distributed, capillary-driven and pre-programmed sweat flow. The tortuous flow characteristics of woven textile conduits based on the numerical fluid-dynamics simulation demonstrate the technological versatility to reproduce this controlled flow in different textile structures. The monolithic integration of textile microfluidics on garments provides unlimited, non-accumulative fluid flow through the extended air-liquid interface for its continuous flow and concomitant evaporation from the fabric surface. In-situ and in real-time sweat analysis with a remotely screen-printed flexible organic electrochemical transistor provides the possibility of various sensor integration and multi-parameter detections. The transistor successfully detects K+ ion concentrations using ion-selective membrane within the sweat physiological ionic range. This mechanically ergonomic, fabric-integrated microfluidic sensing platform, based on rapid additive manufacturing of polyhedral device configurations, offers unique strategies for device design and novel sensing perspectives for advancing wearable point-of-care diagnostics with personalized health monitoring capabilities.