Robust design of gas and liquid micropumps

Due to the small stroke of micro actuators, the compression ratio of micropumps is frequently small. This means that serious constraints exist for most micropump designs concerning self-priming capability and bubble tolerance. To access this problem in this study, criteria for the minimum compression ratio of a micropump are derived depending on the medium transported. It turns out that under real operation and handling conditions (outgassing, incomplete priming) design rules applicable for gas pumps also have to be used for liquid pumps. Next, if the liquid pump is to be able to prime itself, a critical pressure has to be achieved, which leads to a further increase of the necessary compression ratio. To determine this critical pressure, the surface and interfacial energies of the liquid have to be taken into account.

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