Electrokinetic micropumps

A zwitterionic additive has been tested to improve the performance of electrokinetic micropumps, which use the voltage applied across a porous matrix to generate an electroosmotic pressure and flow in microfluidic systems (9). 

The improvements result in a reduction in voltage and power requirements and will facilitate the miniaturization of such systems, e.g., microfluidically driven actuators (9). 

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Olesen LH, Bruus H, Ajdari A (2006) AC electrokinetic micropumps the effect of geometrical confinement, Faradaic current injection, and nonlinear surface capacitance. Phys Rev E 73 056313... 

Reichmuth DS, Chirica GS, Kirby BJ (2003) Increasing the performance of high-pressure, high-efflciency electrokinetic micropumps using zwitterionic solute additives. Sens Actuators B 92(l-2) 37-43... 

Modeling of electrokinetic micropump systems has predicted that the additive, i.e., trimethylammoniopropane sulfonate, cf. Figure 2.2, will result in up to a 3.3-fold increase in the pumping efficiency and up to a 2.5-fold increase in the generated pressure. The predicted values agreed well with the experimental results for flow, pressure and efficiency. Using this additive, pressures up to 156 kPa V and an efficiency up to 5.6% could be reached. 

Flow control systems are critical components of most of the energy systems involving fluid flow and heat transfer. These systems are essential for performance optimization of both macroscale and microscale devices. Micropumps, microvalves, microshear stress sensors, and microflow sensors are integral components of flow control systems. Capillary micropump, MHD micropump, thermocapillary micropump, and electrokinetic micropump have been presented in earlier chapters. The present chapter reports various microactuators and shear stress sensors for flow control systems. More details on microvalves and microflow sensors can be found in other references (Nguyen and Wereley, 2006). 

The microchip used was similar to the chip shown in Figure 2, which has three main channels, five reservoirs and a detection cell. As model analytes, dopamine and catechol were separated and detected using the permanganate CL system on the microchip. The samples were electrokinetically injected into the double-T cross section and separated in the separation channel, and then oxidized by CL reagent which was delivered by a home-made micropump to produce light in the detection cell. The EOF can be coupled with the micropump flow. The detection limits for... 

Nonmechanical pumping. Micropumps in this class are usually continuous and include the use of effects such as electrochemical displacement (bubble generation), thermal expansion, electrohydrodynamics, capillarity, and evaporation forces. The most commonly used nonmechanical pumping method is based on electrokinetic flow. In comparison with mechanical micropumps, field-induced flow is advantageous as it acts as both a valve and a pump, enabling both the direction and the magnitude of the flow to be controlled. 

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