Electrokinetic manipulations of species (fluorescence dyes) in microfluidic continuous flow

Abstract

Many researchers in the biological and chemical field have been using microfluidic technologies in many applications over the last decade. Today, microfluidic technologies are still very relevant to conduct research in the biological and chemical related field due to ‘lab on a chip’ benefits. Miniaturization is very critical in the biological and chemical industries. It allows small amount of precious sample to be used for analysis and research and minimize the wastage and effort to collect and preserve samples. Electrokinetic phenomenon is commonly being studied and integrated onto microfluidic chip for various applications in the biological and chemical field. The easy and cheap integration into microfluidic devices allows many applications to use the electrokinetic phenomenon to help in cell manipulation and the development of drugs. Surface modification is widely used in the fabrication of microfluidic devices. The polydimethylsiloxane (PDMS) surface is being modified to increase its wettability a leyer-by-layer (LBL) deposition scheme using alternately charged polyelectrolyte solutions, namely, positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly(sodium 4-styrenesulfonte) (PSS). This surface modification scheme is being used inside the microchannel to observe the effect it can cause to the reaction inside the microchannel. In this work, flushing of the microchannels with polyelectrolytes is done initially to alter its surface properties. Thereafter, experiments have been done by flowing solution, which consists of fluorescein sodium salt, sodium bicarbonate buffer and DI water, through a microchannel in the presence of an electric field. The surface of the microchannel is being treated to observe the effect it induces on the electrokinetic separation and Faradaic reactions inside the microchannel. Conclusion are then being drawn, based on the recorded and analysed data on the effects of surface modification on the electrokinetic transport of dye inside the microchannel.