Plasma and Blood Cells Separation with Digital Microfluidics
We demonstrated the separation of plasma and blood cells from a whole blood droplet with dielectrophoresis (DEP) and electrowetting-on-dielectric (EWOD). Recently, separation of plasma and blood cells using microchannels has been widely developed. Here, instead of microchannels, the separation of plasma from whole blood was performed in droplets using digital microfluidics (DMF). As shown in Fig. 1(a), when high frequency voltage (VHF) was applied on the middle electrode, the electrical field is built up in the gap space as indicated in the side view; the liquid DEP force drove the plasma onto the energized electrode while the blood cells were expelled by the negative DEP and concentrated on the right side. The droplet with uneven blood cell distributions was subsequently split into two droplets by turning on the left electrode to exert the EWOD force (Fig. 1(b)); one contained mainly plasma and the other held most blood cells. The experimental process is shown in the video, and the extracted plasma cell concentration is 4×106 cell/mL as opposed to the cell concentration 5×109 cell/mL in the whole blood.
Figure 1 Procedure of blood cell separation. (a) Driving plasma and expelling blood cells with positive and negative DEP, respectively. (b) Splitting the droplet with EWOD to create a plasma droplet.
The microscopic images of plasma separation using DEP force (top) and the droplet splitting using EWOD (bottom).