Fabrication of PMMA micro- and nanofluidic channels by proton beam writing: electrokinetic and morphological characterization

The fabrication of microfluidic channels in poly(methylmethacrylate) (PMMA) by proton beam writing and the characterization of their electrokinetic behavior are reported. Microchannels down to 200 nm width have been fabricated in high-molecular-weight, thick PMMA sheets and a surface smoothness of 2.45 nm for the sidewalls of the channels was measured using atomic force microscopy. The polymeric channels were sealed using thermal bonding. The methods of digital video microscopy and current monitoring were used for characterization of the electrokinetic phenomena. The electrokinetic properties of the PMMA rectangular microchannels were measured in 20 mM buffered solutions of phosphate (pH 7.20), tris (pH 8.00) and borate (pH 9.05) at different voltages. In addition, particle image velocimetry was used to determine the electroosmotic flow profile and the electrophoretic mobility of 600 nm polystyrene microspheres. A theoretical model was developed to predict the bulk electroosmotic flow of phosphate buffer solution in the PMMA microchannels and this model showed good agreement with the measured electroosmotic mobilities.