Design of a compact and cost-effective blood plasma separation device utilizing biophysical effects from whole blood with simultaneous colorimetric detection of creatinine and urea

This work presents the development and validation of a compact, efficient, CO2 laser-fabricated passive microfluidic device for plasma separation from undiluted high hematocrit whole blood. The device dimensions were chosen to reduce clogging risk and enable simplified, scalable fabrication. It leverages key biophysical and geometrical effects through bifurcation and constriction regions to exploit Fahraeus and Zweifach–Fung bifurcation effects, migrating RBCs to the channel center. Lift and drag forces further aid in forming a stable cell-free layer for efficient plasma extraction. The device also detects biomarkers such as creatinine (using polyvinylpyrrolidone capped-silver nanoparticles) and urea (using 4-dimethylaminobenzaldehyde) via image-based analysis and has been biologically validated. Specifically, 99.97% separation efficiency at 54.8% hematocrit and 93.5% at 73.4% hematocrit (flow rate 0.6 μl/s) were achieved. Additionally, it integrates a dried reagent-coated μ-pad for on-chip detection of creatinine and urea with limits of detection of 0.05 μM (0–50 μM) and 0.04 mM (0–16 mM), respectively. These results validate plasma purity, making the device suitable for continuous-flow clinical applications. The development is based on comprehensive research into fluid dynamics and separation mechanisms in microchannels, highlighting its compactness, high efficiency, and integration potential for on-chip detection. These advancements significantly improve blood processing technology, enhancing performance and applicability in diagnostic platforms.