Development of a low flow-resistive charged nanoporous membrane in a microchip for fast electropreconcentration.

A nanoporous poly-(styrene sulfonate) (poly-SS) membrane was developed for fast and selective ion transport in a microfluidic chip. The poly-SS membrane can be photopolymerized in-situ at arbitrary location of a microchannel, enabling integrated fluidics design in the microfluidic chip. The membrane is characterized by a low hydraulic resistance and a high surface charge to maximize the electroosmotic flow and charge selectivity. The membrane characteristics were investigated by charge-selective electropreconcentration method. Experimental results show membranes with various percentages of poly-SS are able to concentrate anions (fluorescein and TRITC-labeled BSA). The anion-selective electropreconcentration process is stable and 26-times faster than previously reported poly-AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid) based system. The electropreconcentration was also demonstrated to depend on the sample valency and buffer concentration.