The Study Of Key Components Used For Capillary Monolithic Electroomotic Pump System

Electroosmotic pump as a non-mechanical micropumps is based on electroosmotic flow as a driving force to drive fluid with the features of continuous infusion, no moving parts, no pulse, no mechanical wear and avoid the microleakage caused by the one-way valve and dynamic sealing, etc. Electroosmotic pump can accurately transport microliter and nanoliter fluid, which is the power system of the microfluidic system. By switching of the positive and negative voltage, the flowing direction of the electroosmotic flow in the micro-channel can be easily controlled, to realize the function of the pump; Optimization the geometry of the microchannels can produce different flow rates in the micro-channel; micromachining process is simple, the reliability of the device is high, and it can easily integrated with other microfluidic devices. Thus, it has good prospects for development. However, the long working often lead to the electrolytic of electrolyte, which will generate bubbles into the channel of electro-osmotic pump. Ultimately, electroosmotic pump can not work. By adding the ion bridge which also called electric field decoupler as a key component in the electroosmotic pump system, it can guarantee electrical conduction of electroosmotic pump system. Simultaneously, It can realize the isolation of the working carrier liquid and a platinum electrode, eliminating the bubbles produced by electrolysis and interfere with the system caused by electrolysis products, ensuring that the electroosmotic pump can stablely operate for a long time. This paper aims to address the development and improvement of the key components in the electroosmotic pump system, such as the polyacrylamide gel microelectrode, combine with a positive overall column to construct the electroosmotic pump systems, and test and study the working performance and electrode characteristics of the electro-osmotic pump.In chapter 1, firstly we summarize the development of the electroosmotic pump, introduce the electroosmotic pump’s working principle and its classification, and discuss the electroosmotic pump’s performance and impact factors. Secondly we classified the electroosmotic pump key components-ion bridge or called electric field isolator, also classified the polyacrylamide gel ion bridge classified, summarized the existing preparation technology of polyacrylamide gel column, did a simple summary on its application.In chapter 2, we optimized the technique of fabricating poly-acrylamide gel micro electrodes, mainly focusing on the technology of non-void gel. In literatures reported, the techniques of fabricating poly-acrylamide gel columns were complex, difficult to avoid voids in gel columns and low yield. We use acylamide polymerization solutions of 9%T+3%C and 15%T+2%C to take free radical in-situ polymerization in ice bath for preparing capillary gel columns in one step via continually introducing polymerization solutions through pre-treated fused-silica capillaries. Some parameters like temperature, pressure, etc., were investigated to optimize polymerization conditions. When introduction flow rate was more than 0.4mL/min, the yield of non-void gel columns reach up to 100%. We also studied the characters of gel electrodes through the abilities to withstand organic modifiers, of electric conductivities and of mechanical pressure resistance. It was observed that gel electrodes prepared have no any shrinkage in 0-60% v/v acetonitrile in aqueous solution in 24 hours no matter whether potential was applied; and both keep fine in 80% v/v acetonitrile in aqueous solution in 20 hours, or same buffer condition but potential applied in 5hr; and when 100% v/v acetonitrile in aqueous solution, 13hr and lhr, respectively. Moreover, the capability of conductivity for gel micro electrodes reduced with the increasing concentration of organic modifiers in buffer solutions, and good conductivity can be reach in pH2.0-12.0 with low variation for conductivity values. In the range allowed by experimental conditions (up to 34.5MPa), gel electrodes had no any damage under high pressure for total 6hr.In chapter 3, we introduced positively monomer, [2-(methacryloxy)ethyl] trimethyl ammonium chloride (META), and negatively monomer, 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPS) or 3-Sulfopropyl methacrylate potassium salt (SPMA), respectively to prepare positively and negatively gel electrodes so that optimized polymerization conditions and new characteristic could be obtained. We investigated new fabrication technique through polymerization time and status and found that polymerization time became longer and preparing non-void gel electrodes easier after functional monomers (META/AMPS/SPMA) were introduced into polymerization solution. For novel gel electrodes, stronger abilities to withstand organic modifiers and better conductivity than before, and high pressure resistance (up to 34.5MPa) also could be obtained. Finally, we selected novel gel electrodes with 20% META and 20% AMPS monomer as optimized positively and negatively micro electrodes, respectively.In chapter 4, we integrated monolithic eletroosmotic columns with gel micro electrodes prepared to investigate their real characteristic under real work status of electroosmotic pump (EOP). The result shows that novel gel micro electrodes have low electric resistance, good conductivity and EOP system built has better effectively even if use same monolithic eletroosmotic column than that using old gel electrodes, and can work stably for at least 8hr for buffer system of 0-100% v/v acetonitrile in 0.1% Trifluoroacetic acid (TFA) aqueous solution.In chapter 5, we summarized innovative points in this thesis:1. Process improvement, namely, we combined continuous flow to refresh reactive solution with ice bath for reaction control. A or more poly-acrylamide gel micro electrodes were fabricated by this novel method of continually introducing polymerization solution in ice bath; 2. Performance improvements, using the designs of introducing positive and negative monomers into reactive solution for novel functional poly-arylamide gel micro electrodes. Finally, We described some existing problems in this project and introduced some developments in future.