Fabrication and characterization of a fritless microfabricated electroosmotic pump with reduced pH dependence.
ABSTRACT A fritless electroosmotic pump with reduced pH dependence has been fabricated on a glass microchip and its performance characterized. The chip design consists of two 500-microm channels, one packed with anion exchange beads and the other packed with cation exchange beads, which produce convergent electroosmotic flow streams. The electroosmotically pumped solution flows away from the intersection of the two pumping channels through a field-free channel. This simple design allows for the production of a fritless electroosmotic pump and easy replacement of the ion exchange beads whose charged surfaces generate the flow. The pump was found to produce volumetric flow rates of up to 2 microL/min for an applied voltage of 3 kV at a pH of 6.8. Moreover, the electroosmotic pump can generate high flow rates over an extended pH range of at least 2-12, a significant advantage over previously fabricated electroosmotic pumps, which typically have a more limited range in which they can achieve high flow rates.
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ABSTRACT: Recent years have seen considerable progress in the development of microfabricated systems for use in the chemical and biological sciences. The term micro total analytical system (µTAS) is now a well-accepted concept. Much development has been driven by a need to perform effective manipulation of chemical and biological liquids with small volumes at micro and/or nano flowrate level in these systems. In this review, the focus will be on the pumping techniques used for delivery and control of liquids, especially those physical-chemical 'continuous dynamic flow micropumps'. The principles of these pumping techniques are mainly based on one or several well-known phenomena such as electrical, light, magnetic, thermal and other actuated mechanisms. Electrokinetically-driven continuous flow pumps such as the electrophoretic pump and electroosmotic pump, surface chemistry based continuous flow micropumps such as the opto-electrowetting-based pump, optically-driven pump, electrochemical pump and constant gravity-driven pump, and combination-driven techniques such as hydrodynamic flow and electrokinetic/gravity/magnetophoretic pumping will be summarized. The focus will be on the research highlights, trends and future of these pump techniques. Finally, mixing techniques on the microscale are briefly reviewed.Journal of Micromechanics and Microengineering 12/2007; 18(1):013001. · 1.79 Impact Factor
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ABSTRACT: Microchannel plate (MCP), a porous glass membrane commonly used as an electron multiplier in particle detectors, has been experimentally investigated here for electro-osmotic pumping characteristics. MCP consists of millions of high-aspect ratio precision identical glass microcapillary tubes fused together. Uniform and straight microchannels in a relatively thick membrane can achieve a maximum flow rate per unit area and voltage ~0.2 mL min−1 cm−2 V−1 and a maximum pressure per unit voltage ~80 Pa V−1. MCP also shows a unique characteristic of directional preference in pumping with net flow consistently induced toward the nearest electrode regardless of polarity of the voltage potential applied.Microfluidics and Nanofluidics 13(2). · 3.22 Impact Factor
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ABSTRACT: Here, we report on a micropump that generates hydraulic pressure owing to a mismatch in EOF rates of microchannels and submicrometer cylindrical glass capillaries integrated on silicon. The electrical conductance of such capillaries in the dilute limit departs from bulk linear behavior as well as from the surface-charge-governed saturation in nanoslits that is well described by the assumption of a constant surface charge density. The capillaries show rather a gradual decrease in conduction at low salt concentrations, which can be explained more aptly by a variable surface charge density that accounts for chemical equilibrium of the surface. The micropump uses a traditional cross-junction structure with 10 identical capillaries integrated in parallel on a side arm and each with a 750 nm diameter and 3 mm length. For an applied voltage of 700 V, a hydraulic pressure up to 5 kPa is generated with a corresponding flow velocity nearly 3 mm/s in a straight field-free branch 20 μm wide, 10 μm deep, and 10 mm long. The micropump utility has been demonstrated in an open tubular liquid chromatography of three fluorescently labeled amino acids in just less than 20 s with minimal plate height values between 3 and 7 μm. The submicrometer capillaries are self-enclosed and produced through a unique process that does not require high-resolution advanced lithography or wafer bonding techniques to define their highly controlled precise structures. This article is protected by copyright. All rights reserved.Electrophoresis 06/2014; · 3.26 Impact Factor