Surface modification of polymer-based microfluidic devices Original Research Article

We report the chemical modification of poly(methyl methacrylate) (PMMA), and poly(carbonate) (PC) surfaces for applications in microfluidic systems. For PMMA, a reaction of the surface methyl ester groups with a monoanion of α,ω-diaminoalkanes (aminolysis reaction) to yield amine-terminated PMMA surfaces will be described. Furthermore, it was found that the amine functionalities were tethered to the PMMA backbone through an alkane bridge to amide bonds formed during the aminolysis of the surface ester functionalities. The electro-osmotic flow (EOF) in aminated-PMMA microchannels was reversed when compared to that in unmodified channels. Finally, the availability of the surface amine groups was further demonstrated by their reaction with n-octadecane–1-isocyanate to form PMMA surfaces terminated with well ordered and highly crystalline octadecane chains, appropriate for performing reverse-phase separations. Examples of reverse-phase separations of ion-paired double-stranded DNAs in electric fields (capillary electrochromatography (CEC)) will be demonstrated using a PMMA-based fluidic chip. For PC, sulfonation of the surface with SO3 will be described; this sulfonation makes the surface very hydrophilic. EOF studies of the sulfonated-PC surfaces indicated changes in the pH-dependent profile when compared to unmodified PC.