Biomedical Engineering Reference
In-Depth Information
The diffusion pumps principle has been known for decades and these pumps
were widely used till the 1970s. It relies on momentum transfer of a condensable
vaporized fluid to the molecules to be pumped. Macroscopic diffusion pumps can
generate vacuum down to 10
−6
Pa.
The transfer of this principle also benefits from the characteristic conditions that
count for microfluidic systems. By using MEMS technologies the geometry of the
steam nozzles can be reduced drastically without losing relative accuracy. Thus, the
overall dimensions of the pump and also the amount of steam that is necessary for
operation is reduced. Another advantage of a micro-diffusion pump is that the cap-
illary forces overbalance gravity forces, which are decisive in the macroworld.
Hence it is possible to construct a pump that can be operated orientation-
independent.
All the above-mentioned pumping principles have been proofed and are momen-
tarily adjusted for the operation to supply the necessary pressure and pump power
regimes for the PIMMS.
Acknowledgment
This work was funded and supported by several organizations and scientific as
well as industrial partners for more than a decade. A number of PhD students, and many Diploma
and Master students worked on this subject. It was funded by the City of Hamburg, the German
Research Council (DFG), the European Union as well as the German Ministry of Research and
Development; scientific partners were LETI and industrial partners Leda Mass, now part of MKS,
Bayer Technology Services, and Krohne Messtechnik. PhD students besides the coauthors were
Volker Relling, Ralph Siebert, Gerald Petzold, Jan-Peter Hauschild, and Eric Wapelhorst. Neither
the PhD students nor the funders ever lost their confidence that finally we would succeed in real-
izing such a complex and fully integrated mass spectrometer.
Finally we appreciate the critical reading of the text by Winfred Kuipers.
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