High-Yield Passive Plasma Extraction via Dimensionally-Confined Gravity Sedimentation for Ultrasensitive Pancreatic...

Carbon nanotube field-effect transistor (CNT-FET) biosensors are promising platforms for point-of-care testing (POCT) of biomarkers because they offer high sensitivity, miniaturization, and integration capability. Nevertheless, the analysis of whole blood using a CNT-FET biosensor is constrained by interference from blood cells and cellular metabolites. To address this challenge, we developed a pressure-driven microfluidic system that uses passive gravitational separation and integrates the separated plasma stream with a CNT-FET biosensor. The platform combines dimensional confinement with blood cell aggregation at low shear rates to separate plasma from whole blood, achieving a plasma yield of 84.9% and a blood cell removal efficiency of 99.9%. This plasma extraction step reduces blood-cell interference and enables CNT-FET detection of the pancreatic cancer biomarker CA19-9 directly from whole blood samples, with a limit of detection (LOD) of 0.80 mU/mL. This work provides a microfluidic strategy for applying CNT-FET biosensors to real biological samples and offers an integrated approach for blood biomarker analysis in POCT and resource-limited settings.