Investigation Of Ion Concentration Polarization Behavior At The Micro-Nanofluidic Interface On Fused Silica Capillary

With the development of microfluidic, nanofluidic has become a new filed of study. The concentration polarization effect at the micro-nano interface is drawing more and more concerns due to its potential applications in on-line and high efficient preconcentration of charged species from small amount of samples. Recent works have shown that charged molecules can be effectively concentrated on the micro-nanofluidic interface. Better understanding on the concentration polarization is significant to the use of concentration polarization in pre-concentration.In the first chapter of this paper, nanofluidic chip fabrication methods, theory of ICP at the micro-nano interface, sample injection and applications were reviewed in the light of capillary chip electrophoresis.In the second chapter, a micro-nano interface was established based on partial etching of the fused silica capillary. The resistance of the HF etched nanopore on fused silica capillary was measured with electrochemical workstation. The pore resistance is about 56.5-110.5 KΩ. Depletion region was investigated under different electric field by fluorescent microscope imaging. Concentration zone under different concentration time and volage was investigated by laser induced fluorescent detection. It was noted that the concentration time and volage had an impact on the profile of the concentration zone.In the third chapter, a capillary chip integrating with a fracture inlet and an HF etched nanofluidic interface was prepared. The reproducibilities of injection and electrokinetic stacking were investigated. Concentration polarization based stacking was performed with tangential electric field. The behavior of mix fluorescent probe molecules was tested, and it is noted that the positivley charged rhodamine 6G was concentrationed, while the neutral rhodamine B exhibited no stacking effect.This study showed that the charged species can be electrokinetically stacked in various forms inside the capillary. More applications could be developed for online concentration of charged molecules and sepration based on the polarization effect.