Preparation And Characterization Of Micro-nanofluidic Interface On Fused Silica Capillary By Partial Etching And Ultrasonic

With the development of microfluidic, nanofluidic as an analogue of the field of microfluidics, has become a new filed of study. Nanofluidics is defined as the study and application of fluid flow in and around nanometer-sized objects with at least one characteristic dimension below100nm. As the dimension of a nanochannel decreases to that of electric double layer (DEL)、DNA and proteins, the nanochannel shows a unique ion transport properties-ion concentration polarization (ICP). A new type of electrokinetic pre-concentration can be implemented with a nanofluidic interface based on ICP effect.In the first chapter of this paper, theory of ICP at the micro-nano interface, rectification effect, nanofluidic chip fabrication methods and the applications of nanofluidic interface were reviewed in the background of preconcentration of small amount of sample.In the second chapter, the nanofluidic interface was prepared by partial etching of the fused silica capillary. The resulted thickness of the capillary wall (40-50μm) was about10times greater than that by whole etching, thus the robustness of the interface was greatly enhanced. The interfaces exhibited close resistance in the same electrolyte, indicating that the preparation is reproducible. No obvious rectification effect was observed with this interface, which is the character of a symmetrical interface. However, the interface showed stable ICP as visualized by Fluorescein sodium. Concentration factor as high as100for green fluorescent protein was achieved. The surface charge of the interface can be flexibly tailored by layer-by-layer modification with polyelectrolytes (PDDA and PSS), as can be verified by the ICP effects of Fluorescein sodium and Rhodamine6GIn the third chapter, ultrasonic was used for the preparation of nanofracture on the fused silica capillary. The width of nanofracture is estimated by resistance measurement with a theoretical model, and the results was confirmed by scanning electron microscopy. The width of nanofracture falled in20-300nm. Fluorescein sodium and λ DNA can be well concentrated on the interface, and a concentration factor of105was demonstrated for λ DNA.This study showed that the charged species such as fluorescein sodium, GFP and λ DNA can be effectively concentrated inside the capillary, and more applications can be found with these established capillary nanofluidic interfaces...