3D-Printed Epidermal Wearable Microfluidic Platforms for Accurate Spectroscopic and Fluorometric Sweat Analysis

Wearable technologies for sweat capture and biochemical analysis offer a non-invasive, real-time window into physiological health, enabling the continuous monitoring of hydration levels, electrolyte balance, metabolic function, and exposure to harmful environmental agents or illicit substances. These devices are particularly valuable for preventive health, fitness monitoring, and early-stage disease diagnostics. Despite recent advancements in skin-compatible, flexible microfluidic systems, current platforms face limitations in achieving reliable, artifact-free measurements during on-body testing due to mechanical deformation and inaccuracies inherent to digital imaging in colorimetric assays.<br/><br/>In this study, we introduce a novel 3D-printed microfluidic platform featuring integrated microscale optical cuvettes and valves, fabricated from hard/soft hybrid materials. This innovative system enables highly accurate and sensitive spectroscopic and fluorometric assays of sweat biomarkers, overcoming the limitations of conventional wearable sensors. By utilizing 3D printing techniques, we achieve precise control over microfluidic architectures, allowing for optimized fluid handling, enhanced mechanical stability, and improved analyte isolation. The hybrid material design combines rigid structural components for stability with soft, skin-compatible elements, ensuring both robustness and user comfort during continuous wear.<br/><br/>Comprehensive experimental evaluations demonstrate the platform’s capability to accurately quantify concentrations of copper, chloride, and glucose in sweat, as well as monitor pH levels, with laboratory-grade precision under diverse physiological and environmental conditions. The system is designed to mitigate common sources of error in on-body sweat analysis, such as evaporation and contamination, thus ensuring high data fidelity in real-time monitoring scenarios. Furthermore, the platform offers dual functionality: in situ analysis for immediate feedback and compatibility with benchtop spectrometers for high-resolution data acquisition in laboratory settings.<br/><br/>This work also explores a range of polymeric materials for the fabrication of the platform’s hard and soft components. Quantitative investigations of their optical, chemical, and mechanical properties, coupled with computational modeling, inform the design of microfluidic networks and cuvette geometries optimized for efficient fluid management and minimized cross-contamination. Field studies conducted in a variety of settings further validate the system’s robustness and accuracy during physical activity, underscoring its potential for wide-ranging applications in health diagnostics, fitness monitoring, and environmental assessment.<br/><br/>The integration of 3D-printed microscale optical cuvettes within a hard/soft hybrid material system represents a significant advancement in wearable sweat sensing technology. This approach not only enhances the precision and sensitivity of biomarker detection but also addresses critical challenges associated with mechanical deformation and imaging artifacts in on-body measurements. As a result, this platform establishes a new standard for reliable, field-deployable biochemical sensing systems, with broad implications for clinical diagnostics and health monitoring in everyday life.