Various surface modification methods of a microfluidic chip with plasma treatment and hydrophilic polymers were presented. A normal microfluidic chip prepared using polydimethylsiloxane (PDMS) or plastic materials including polycarbonate have hydrophobic surface of a microchannel of a microfluidic chip. In this study, surface of a microchip was modified by treating plasma for 3 min. Then the hydrophilic surface of the microchip was obtained. To prepare more durable hydrophilic surface of a microchip, various hydrophilic polymers including polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), and poly(ethylene glycol) methyl ether acrylate (PEGMEA) were coated on the surface of the microchip. Then hydrophilic surface of the microchip was characterized by the contact angle measurement. Therefore the PVP or PEO coated microchip showed the most hydrophilic surface.Surface modification procedures of a microchannel of a polycarbonate (PC) chip with hydrophilic polymers were shown in. An untreated microfluidic chip have hydrophobic surface of a microchannel. And the surface of the microchannel can be changed to hydrophilic by applying plasma treatment. However the prepared hydrophilic surface of the microchannel may change again to hydrophobic because of polymer chain’s reorientation. Thus, hydrophilic polymers needed to coat on the hydrophilic surface of the microchannel to preserve the hydrophilic surface. A plasma treatment device from Harrick Plasma was used to treat plasma on a microchip surface. And a contact angle measurement device from LMS Technologies was used to measure contact angle of a water drop on the treated PC surfaces.PDMS have hydrophobic surface. However the hydrophobic surface can be changed to hydrophilic surface by applying plasma treatment as shown in. A PDMS chip was treated plasma using a plasma device for 3 min) and measured contact angle of a water drop on the surface of the PDMS chip using a contact angle device. As shown in, untreated PDMS surface showed hydrophobic surface. However the treated PDMS surface showed hydrophilic surface as shown in Fig. 3d. Then various hydrophilic polymers including PVA, PEO, PVP, PEGMEA were coated on the surface of PC chips as shown in Fig. 4. The hydrophilic polymer coated PC chips had hydrophilic surface as shown in. Then the prepared PC chips were investigated by contact angle measurement with a water drop as shown in.
