Blood plasma separation microfluidic chip with gradual filtration

Blood is one of the most crucial biological materials that can be used to diagnose diseases. In order to avoid the effects of blood cells for cell free plasma detection, the first step toward a blood test is the blood separation. We developed a microfluidic chip for blood plasma separation with gradual filtration, which consisted of front-end cell capture structures and back-end filters. Two types of filters were proposed: straight line filters and square wave filters. The cell capture structures and filters, fabricated on PDMS (polydimethylsiloxane), included two structural layers. The first layer consisted of pillars to create small gaps between the second layer and glass, which enabled the flow of the plasma through the capture structures while trapping the cells in the structures. The second layer was an array of U-shaped structures. The results showed that the separation efficiency of plasma enhanced with increased dilution factor and decreased height of the gap created by the pillar layer. The separation efficiency was only 20% under 2@mm gap and dilution factor 10 and increased to 91% under the gap of 1@mm height and dilution factor 50 in the chip with the straight line filters. The separation efficiency was close to 100% under the gap of 1@mm height and dilution factor 20 in the chip with the square wave filters.