Direct loading of blood for plasma separation and diagnostic assays on a digital microfluidic device

Finger-stick blood sampling is convenient for point of care diagnostics, but whole blood samples are problematic for many assays because of severe matrix effects associated with blood cells and cell debris. We introduce a new digital microfluidic (DMF) diagnostic platform with integrated porous membranes for blood-plasma separation from finger-stick blood volumes, capable of performing complex, multi-step, diagnostic assays. Importantly, the samples can be directly loaded onto the device by a finger "dab" for user-friendly operation. We characterize the platform by comparison to plasma generated via the "gold standard" centrifugation technique, and demonstrate a 21-step rubella virus (RV) IgG immunoassay yielding a detection limit of 1.9 IU mL −1 , below the diagnostic cut-off. We propose that this work represents a critical next step in DMF based portable diagnostic assays-allowing the analysis of whole blood samples without pre-processing. The integration of 3D porous membranes in a digital microfluidic device enables the generation of cell-free plasma from finger-stick volumes of blood with in-line, on-chip analysis.