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Electroosmotic flow is caused by the Coulomb force induced by an electric field on net mobile electric charge in a solution. Because the chemical equilibrium between a solid surface and an electrolyte solution typically leads to the interface acquiring a net fixed electrical charge, a layer of mobile ions, known as an electrical double layer or Debye layer, forms in the region near the interface.
Continuous flow microfluidics rely on the control of a steady state liquid flow through narrow channels or porous media predominantly by accelerating or hindering fluid flow in capillary elements. [28] In paper based microfluidics, capillary elements can be achieved through the simple variation of section geometry.
This is electrocapillary flow, an example of electrocapillarity. Electrocapillary phenomena are phenomena related to changes in the surface free energy (or interfacial tension ) of charged fluid interfaces, for example that of the dropping mercury electrode (DME), or in principle, any electrode, as the electrode potential changes or the ...
Capillary electrophoresis aims to separate analytes on the basis of their mass-to-charge ratio by passing a high voltage across ends of a capillary tube, which is filled with the analyte. High-performance liquid chromatography separates analytes by passing them, under high pressure, through a column filled with stationary phase .
Drug delivery application does not require high flow rates, however, the micropumps are supposed to be precise in delivering small doses and demonstrate back pressure independent flow. [16] Due to biocompatibility and miniature size, silicon piezoelectric micropump can be implanted on the eyeball to treat glaucoma or phthisis .
The anionic character of the sulfate groups of SDS causes the surfactant and micelles to have electrophoretic mobility that is counter to the direction of the strong electroosmotic flow. As a result, the surfactant monomers and micelles migrate quite slowly, though their net movement is still toward the cathode. [3]
Electroosmotic pumps are fabricated from silica nanospheres [6] [7] or hydrophilic porous glass, the pumping mechanism is generated by an external electric field applied on an electric double layer (EDL), generates high pressures (e.g., more than 340 atm (34 MPa) at 12 kV applied potentials) and high flow rates (e.g., 40 ml/min at 100 V in a pumping structure less than 1 cm 3 in volume).
The surface potential of the cell wall produces electro-osmotic flow. Since the electrophoresis chamber is a closed system, backward flow is produced at the center of the cell. Then the observed mobility or velocity from Eq. (7) is a result of the combination of osmotic flow and electrophoretic movement.