2-Bromoisobutyryl bromide was immobilized on poly(methyl methacrylate) (PMMA) substrates activated using an oxygen plasma. Atom-transfer radical polymerization was then performed to graft poly(ethylene glycol) (PEG) on the PMMA surface. PMMA micro capillary electrophoresis (µCE) devices made with the covalently modified surfaces exhibited substantially reduced electroosmotic flow and nonspecific adsorption of proteins. Both column efficiency and migration time reproducibility were one order of magnitude better with derivatized PMMA µCE devices compared to untreated versions. Fast, reproducible, and efficient separations of proteins and peptides were demonstrated using the PEG-grafted PMMA µCE chips. All analyses were completed in less than 60 seconds, and separation efficiencies as high as 53000 plates for a 3.5-cm long separation channel were obtained. A surface reactive acrylic polymer, poly(glycidyl methacrylate-co-methyl methacrylate) (PGMAMMA), was synthesized and evaluated for suitability as a substrate for fabrication of microfluidic devices for chemical analysis. This polymer has good thermal and optical properties, and is mechanically robust. A key advantage of this polymeric material is that the surface can be easily modified to control inertness and electroosmotic flow using a variety of chemical procedures. In this work, the procedures for aminolysis and photografting of linear polyacrylamide on microchannel surfaces in PGMAMMA substrates were developed, and the performance of the resultant µCE devices was demonstrated for the separation of amino acids, peptides, and proteins. Separation efficiencies as high as 46000 plates for a 3.5-cm long separation channel were obtained. Finally, a novel approach was developed to integrate a buffer ion permeable membrane in a PGMAMMA micro electric field gradient focusing (µEFGF) device. Using the µEFGF device, green fluorescent protein (GFP) was concentrated 4000-fold. Separation of GFP and R-phycoerythrin (R-PE), and selective elution of GFP from a protein mixture containing GFP, FITC-labeled casein, and FITC-labeled hemoglobin were also demonstrated. It was found that the volume and concentration of buffer and presence of carboxylic acid impurities in the membrane, which control the conductivity and ion transport properties of the membrane, strongly affected the behavior of the µEFGF device.



College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry



Date Submitted


Document Type





Microfluidic, polymer, surface, modification, separation, electrophoresis, protein, peptide