Fabrication Of Hybrid PDMS-PCTE Chip And Interfacing Of Electrokinetic Stacking To Microchip Electrophoresis

Chip fabrication is the basis of the micro-nanofluidic analytical technology.Introduction of a micro-nanofluidic interface into a chip system is especially challenging.Detection of low concentration solute with a chip system is difficult due to the limited sample introduction volume in a micro-nanofluidic system.Because of this,online enrichment of the sample in order to increase the detection sensitivity is an important issue.On chip sample stacking based on ion concentration polarization effect occurred at a micro-nanofluidic interface has been drawn particular attention due to its fast speed and high concentration rate.An efficient online sample stacking mechanism combined with chip electrophoresis plays important role in improving the performance of micro-nanofluidic chip.In the first chapter,the micro-nanofluidic chip preparation,sample introduction and online sample enrichment methods are introduced,with emphasis of the ion concentration polarization effect and interfacing of online stacking with chip electrophoresis.In the second chapter,for interfacing ion concentration polarization based electrokinetic stacking to microchip electrophoresis separation,a hybrid PDMS-PCTE chip system was designed and prepared by casting molding.The chip was used in the sample introduction-separation,sample introduction-online concentration and introduction-online concentration-separation operation modes investigations.Firstly,the microchannels of the PDMS was modified by dynamic coating,then the injection time and injection voltage in the sample introduction-separation operation mode was investigated.It was found that after the coating treatment,sample was well introduced in the 1 × TBE buffer system with the 150 V injection voltage and 10 s injection time.The DNA marker was successfully separated and detected with the hybrid chip system.Secondly,the micro-nano interface was characterized by resistance measurement method,and the influence of concentration voltage and time in the injection-concentration operation mode was investigated.Experimental results showed that with the interface of 2 nanopores in the continuous concentration mode,the optimum concentration voltage is 250 V.The fluorescence signal intensity of 1×TBE/10-5 mol/L fluorescein sodium reached to that of the 1×TBE/10-2 mol/L fluorescein sodium,indicating a concentration factor of 1000 times with 180 s continuous concentration.Finally,in the continuous injection-concentration-separation operation mode,online concentration and separation of fluorescein sodium and DNA marker was demonstrated with the interfaced chip system.Experiment results indicated that the electrokinetic stacking and microchip electrophoresis were effectively interfaced,and the DNA marker was successfully concentrated and separated.With 180 s continuous concentration,an enrichment factor close to 10 times was achieved compare to that of direct injection of 10 s under the same stacking voltage condition of 300 V.The hybrid PDMS-PCTE chip prepared in this paper is sample and with which the interfacing of ion concentration polarization based electrokinetic stacking to microchip electrophoresis is well demonstrated.This is significant for improving the concentration of analyte thus to increase the detection sensitivity,and realize the analysis of low concentration solute from real sample with chip system.