Simulation and experimental characterization of plug distortion in hybrid microchannels

Abstract

The plug distortion for on-chip capillary zone electrophoresis systems with rectangular separation channels, manufactured in a hybrid layer system with different material properties of the vertical and the horizontal walls has been examined. Experimental data and simulation results indicate that plug widening caused by different values of the f-potential of the walls in contact with the fluid depends strongly on the aspect ratio of the channel cross section. If the height to width ratio is much greater or much smaller than 1, as is often the case for commonly used labchip architectures, plug widening may be negligible. The difference of the f-potentials between the vertical and the horizontal sidewalls has been determined from the shape of the plug edges. For an architecture using glass for the top and bottom walls, but SU-8 for the sidewalls, the difference of the f-potentials was measured to be on the order of only 2.4 mV for a pH of 9.2, suggesting that such device architectures may be used for on-chip electrophoresis analysis without uniform coating of the channel inside for less-demanding applications.