Fabrication and Characterization of a Fritless Microfabricated Electroosmotic Pump with Reduced pH Dependence

Department of Chemistry, West Virginia University, MGW, West Virginia, United States
Analytical Chemistry (Impact Factor: 5.64). 04/2004; 76(5):1336-41. DOI: 10.1021/ac034956e
Source: PubMed


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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    • "The beads were held in place by a microfabricated weir structure. To reduce the effect of the pH change of a pump solution on the rate of an EOP, Razunguzwa and Timperman (2004) built an EOP consisting of two 500 μm channels with one packed with anion and the other packed with cation exchange beads. As the EOF rate from one channel increase due to the pH variations of the pump solution, the EOF rate from the other channel will decrease, and vice versa. "
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    ABSTRACT: Electroosmotic pumping is receiving increasing attention in recent years owing to the rapid development in micro total analytical systems. Compared with other micropumps, electroosmotic pumps (EOPs) offer a number of advantages such as creation of constant pulse-free flows and elimination of moving parts. The flow rates and pumping pressures of EOPs matches well with micro analysis systems. The common materials and fabrication technologies make it readily integrateable with lab-on-a-chip devices. This paper reviews the recent progress on EOP fabrications and applications in order to promote the awareness of EOPs to researchers interested in using micro- and nano-fluidic devices. The pros and cons of EOPs are also discussed, which helps these researchers in designing and constructing their micro platforms.
    Preview · Article · Feb 2009 · Microfluidics and Nanofluidics
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    • "Despite the success observed with regards to the utilization of packed beds in capillaries for generating high pressure, their use on a microchip platform for generating pressure greater than 5 atm, to date, has not been achieved. Some lower pressure designs have been presented based upon ion exchange membranes (4.4 atm) [18] and anion/cation exchange beads (characterized under an unspecified low backpressure condition for maximal flow) [19]. Our experience in the application of packed bed microbeads and monoliths on the microchip platform for performing capillary electrochromatography [20], solid phase extractions [21], and immunoassays [22], was applied in this work to the construction and characterization of a microfabricated planar EOF pump based upon a single microchannel, uniformly packed with 3.38 ␮m silica microspheres that were held in place by a microfabricated weir structure. "
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    ABSTRACT: A high pressure electroosmotic flow (EOF) pump was fabricated within a glass substrate and tested to characterize its fluid dynamic performance. The EOF pump was constructed on a compact, planar microchip platform with (L × W × D) dimensions of 10 cm × 3.6 cm × 0.3 cm. The pumping region itself consisted of a straight channel (3 cm × 160 μm × 62 μm) uniformly packed with 3.38 μm silica microspheres held in place by a microfabricated weir structure. Characterization of the microchip EOF pump included pressure and flow rate measurements as a function of voltage and system backpressure for a buffered aqueous fluid containing 10 mM cyclohexylamino alkyl sulfonate CHES. Measurements indicate a maximum pressure of 25 atm and a maximum measured flow rate of 85 nL/min. Linear relationships of pressure and flow rate with voltage were confirmed. Current measurements show linear profiles with voltage for flow rate and maximum pressure measurements, indicating minimal effects due to Joule heating under either test condition. Design and performance considerations relating to fluid dynamic considerations are discussed. The large pressures generated electrokinetically by the microchip EOF pump show the potential for a compact motive source that allows for easy integration with applications requiring high pressures.
    Preview · Article · Apr 2008 · Sensors and Actuators B Chemical
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    • "Zeng et al. used silicate [13] and polymer [14] frits to improve the thermodynamic efficiency of EOF pumping. Razunguzwa et al. packed anion and cation exchange beads into glass microchannels to reduce the pH dependence of an EOF pump [15]. In terms of capillary electrophoretic separation, a polyelectrolyte multilayer coating technique [16] was explored to control the charge and composition of the capillary wall [12]. "
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    ABSTRACT: A rapid field-free electroosmotic micropump (RFEP) was constructed incorporating separate anionic and cationic glass microchannel surface modifications and its performance was investigated. Two of the arms of the devised Y-shaped RFEP were coated with anionic and cationic polymers, respectively. Different charges localized on these interior surfaces produced electroosmotic flow in opposite directions when an electric field was applied along the two coated arms. The hydrodynamic pressure developed at the common junction of the three arms generated field-free flow, which responded rapidly and reversibly to the applied electric field. The flow rate of the devised RFEP was 262.4 nL min−1 when 1.0 kV cm−1 was applied in 10 mM phosphate buffer at pH 7.0. Field-free flow in the vertical channel was quickly and precisely controlled by an external voltage program, as previously demonstrated by field-free gated injection and microbead sorting experiments. Gated field-free injection was achieved by combining two RFEPs at a simple cross. The devised RFEP was found to produce rapid short hydrodynamic pulses, which allowed the sorting of microbeads at up to 120 objects per minute in a biocompatible manner.
    Full-text · Article · May 2007 · Sensors and Actuators B Chemical
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