Design and characterization of a self-powered microneedle microfluidic system for interstitial fluid sampling

Dermal interstitial fluid (ISF) is a promising source of biomarkers for point-of-care (PoC) diagnostics, yet noninvasive and reliable extraction remains a significant challenge. In this study, we present a fully passive microneedle (MN) platform that integrates hydrogel-forming MNs, a hydrogel-based osmotic pump, and paper microfluidics to enable zero-power ISF extraction and analyte transport from skin models. The system's performance was evaluated using paper microfluidic designs optimized for both bulk fluid uptake and lateral flow-based detection. Osmotic pumping with glycerol and glucose showed comparable extraction efficiencies. Cortisol, a representative stress biomarker, was successfully recovered following 15-minute, 45-minute, and 24-hour sampling durations, demonstrating the platform's suitability for both short-term and extended ISF monitoring. These results highlight the potential of this integrated MN system as a simple, cost-effective, and minimally invasive solution for passive ISF sampling and subsequent biochemical analysis.