Electrokinetic Stacking At Nafion Junction And Interfacing To Microchip Electrophoresis System Of PDMS Substrate

Microfluidic systems have experienced rapid growth in the past two decades due to advantages in miniaturization, integration, and automation. However, poor detection sensitivities due to miniaturization greatly hinder microchip’s practical applications, particularly in bio-sample analyses. In order to maintain the advantages of the microchip analysis system and make full use of detection sensitivity of the existing detection means, various online sample preconcentration techniques have been proposed. Among them, ion concentration polarization (ICP) occurred at a micro-nanofuidic interface exhibits great potential in online sample preconcentration.In the first chapter of this paper, theory of ion concentration polarization on micro-nano interface was introduced, the electric injection technology and microfabrication method of microfluidic chip were reviewed in the background of online sample preconcentration for microchip electrophoresis.In the second chapter, a novel mcirochip electrophoresis system was fabricated by polydimetholsiloxane (PDMS) casting method. Nafion membrane was easily integrated into the chip to create the micro-nano interface due to high elasticity of PDMS. On the chip, concentrating of sodium fluorescein probe molecules was demonstrated, and the effect of the voltage and the concentration of buffer solution on sample concentration were investigated. 103 times concentration of 10-5 mol/L fluorescein sodium was achieved within 10 min with the chip.In the third chapter, sample introduction, concentration and interfacing to electrophoresis separation were studied with the chip system by using sodium fluorescein probe molecules. Due to small size of the contact point of the two cross channels, flooding effect was effectively suppressed, and the electrokinetic injection program was much simplified with improved reproducibility. Testing 5 times, the relative standard deviations of peak height, peak area and half-width were 0.058,0.092,0.103, respectively. The signals were improved, when concentration was interfacing to electrophoresis separation. Separation of the 11 fragments of the φx174 DNA marker was implemented by non-gel electrophoresis with the sample introduction method.The chip system presented in this work is simple, cheap and reusable. Though interfacing of stacking and electrophoresis is yet to be demosntrated, the performance of the chip electrophoresis could be enhanced by further optimization of the injection, stacking and separation processes.