Blood plasma separation and extraction from a minute amount of blood using dielectrophoretic and capillary forces

This paper presents a microfluidic device that can separate and extract blood plasma from several microliters of blood without external mechanical driving sources such as a centrifugal machine and a syringe pump. This device consists of a main-channel, many side-channels, a reservoir, and two electrodes. After blood was automatically injected into the main-channel by capillary force, blood cells blocked the side-channel entrances and prevented blood plasma from entering them. Next, when AC voltage application between the two electrodes separated blood into cells and plasma by dielectrophoresis (DEP), cells were removed from the side-channel entrances. This permitted plasma to be injected into the side-channels connecting to the reservoir. Experiments using diluted blood samples (dilution 1:9) showed that blood cell removal and blood plasma extraction were affected by channel geometry and magnitude/frequency of applied AC voltage. In case of applied AC voltage of 10 V and 1 MHz, blood cells were removed by about 97%, and blood plasma of about 300 nL was extracted from 5 μL blood. Moreover, we found that optimal dimension of the side-channels for blood plasma extraction is 5 μm wide and 2 μm deep.