An electrokinetic cell model for analysis and optimization of electroosmotic microfluidic pumps

A simple bead packed electroosmotic microfluidic pump has been designed and fabricated. Such pumps can generate pressure of over 10 atm and are amenable to integration with other microfluidic components, thus making these pumps highly attractive for lab-on-a chip devices. An analytical theoretical description for such packed beads micropumps is presented. It is based on the cell models for hydrodynamic and electrokinetic transport in complex porous media. The theoretical analysis yields useful relationships between the parameters of the pump (bead size, capillary size, electrokinetic ζ-potential) and its performance (pressure and flow) rate and hence, provides guidelines for optimal design for desired properties. We found that the generated pressure strongly depends on the bead size. It also increases with the bead ζ-potential, volume fraction and capillary length. The flow rate on the other hand is not an explicit function of the bead size, but depends on the overall capillary cross-sectional area. This allows for independently varying of these two essential properties. The theory was tested against model experiments, thus proving its validity, range of applicability and limitations.