Hydrophilic skin-interfaced microfluidic devices for comprehensive sweat collection and analysis

Blood and interstitial fluids are standard biofluids for clinical assessments. Despite their rich analyte content, the adaptation of bioanalysis in wearable devices limits its use because their collection requires invasive procedures. In contrast, sweat contains many of the same biomarkers found in blood, offering a non-invasive alternative for health monitoring. However, the relationship between sweat composition, gland physiology, and their clinical relevance remains poorly understood. To evaluate the feasibility of sweat as a reliable biofluid for health monitoring, it is essential to examine the mechanisms of biomarker diffusion and their correlation between blood and sweat glands, employing rigorous analytical methodologies. Recent research has increasingly emphasized accurate and precise detection of metabolites, proteins, and disease-specific biomarkers in sweat for applications in clinical diagnostics, preventive healthcare, and early disease detection. Thus, soft skin-interfaced polydimethylsiloxane (PDMS)-based microfluidic devices have recently emerged as promising platforms for on-demand sweat biomarker analysis. However, the intrinsic hydrophobicity of PDMS poses a limitation by hindering efficient sweat transport through microfluidic channels, necessitating specific pressure thresholds for optimal collection, presenting a significant challenge for reliable sample collection and analysis in sweat-based health monitoring. This work introduces a hydrophilic, skin-interfaced microfluidic device fabricated using a composite material of block copolymer PDMS-polyethylene glycol (PDMS-PEG) and PDMS to address the intrinsic material challenges. The hydrophilic modification significantly enhances the ease of sweat harvesting, particularly during the initial sweating event, enabling more comprehensive capture of molecular information compared to traditional PDMS-based devices. Comprehensive characterization of the microfluidic devices demonstrates improved surface properties, mechanical strength, optical clarity, and microfluidic performance. Integrating hydrophilic block copolymers into wearable sweat microfluidic systems enhances the potential for non-invasive platforms for reliable and rigorous health monitoring and paves the way for future clinical and occupational health applications.