Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
1999-12-21
2001-04-10
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Electric or magnetic motor
Reexamination Certificate
active
06213735
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a micromechanical ejection pump for separating small fluid volumes from a flowing sample fluid, by means of which sample fractions can be physically separated from a continuous sample flow with very small dead volumes occurring during this process.
BACKGROUND
The separation of small fluid volumes from a fluid flow poses relevant problems in many areas of chemical, biological and pharmaceutical analytics. It is frequently desirable to feed macromolecules, which have already been high-dissolution separated by a chromatographic process and are available as a fluid sample, directly to an analysis system, such as a gel electrophoresis. Devices have been described which allow such fluid dosing. According to Nilsson et al. (Journal of Biochemical and Biophysical Methods 27, 181-190 (1993)) such a device comprises a water-filled pumping chamber with attached piezoceramics. Upstream of the pumping chamber discharge a brass block is arranged through which a steel cannula is guided. This steel cannula carrying the sample flow possesses two openings arranged at right angles to the flow axis, one of which serves as connection for the pumping chamber and the other one for ejection of the microdroplets to be selected. To avoid mixing effects the fluid flow and the pumping chamber fluid are separated by a Teflon membrane of small thickness via which the pressure wave required for droplet formation can propagate. Coupling of the sample chamber to the pumping chamber is effected here by means of four bolts. The volume of the sample chamber proper is 5 &mgr;l. The overall volume of the device is indicated as 34 &mgr;l. This device is disadvantageous because of the complicated manufacturing technology and the relatively large volume.
Wallman et al. (Proc. Transducer 95, 303-304) describe a device in which the sample chamber is of sandwich configuration. Here two silicon wafers, into which 2 mm×15 mm×350 &mgr;l large cavities have been etched, are interconnected thus building a flow duct. The upper wafer presents a hole at each end of the sample chamber, which allows inflow and outflow of the sample fluid. Between the holes a piezoceramics is arranged which allows sample ejection through an oppositely arranged 60 &mgr;m diameter hole in the lower wafer. The dead volume of this device amounts to approximately 1 &mgr;l.
The microfluid manipulator described in EP 0 672 834 is a device with two functional units, a microdroplet emitter and a microfluid diode. Dosing fluid droplets are injected by means of a microdroplet emitter into a droplet chamber where they wet the input surface of the microfluid diode which allows feeding the fluid medium into a target fluid. The overall volume of the microdroplet emitter and the supply duct amounts to approximately 1 &mgr;l. Another disadvantage presented by this device is that thorough mixing of the fluid to be dosed in may occur in the microdroplet emitter.
SUMMARY
The object underlying the present invention is to reduce the volume of the dosing device and to allow dosing of a very small sample fraction without any mixing effects. The manufacturing process for such miniaturized device should involve very small manufacturing efforts.
The micromechanical ejection pump according to the invention is in particular integrated in a substrate and is in particular manufactured by injection molding or micromechanical treatment (e.g. etching in an etchable substrate material). In the substrate a sample fluid duct is formed which is intersected by a second duct. The sample fluid flows through the sample fluid duct while the working fluid passes through the working fluid duct with the working fluid preferably being inert to the sample fluid. The second duct comprises a first section connected with the first pressure/suction pump and joining the sample fluid duct in transverse direction. At the sample fluid duct side opposite this junction the second section (so-called ejection duct) of the second duct starts. Via this ejection duct that fraction of the sample fluid, which is just present between the two junctions where the working fluid duct and the ejection duct join the sample fluid duct, is ejected together with the working fluid which flows under pressure through the working fluid duct with the aim of ejecting the sample fraction.
Preferably the cross-sectional areas of the working fluid duct and the ejection duct are essentially identical and range in particular between 0.01 mm
2
and 0.12 mm
2
. The ratio of the cross-sectional area of the sample fluid duct to the cross-sectional area of the working fluid duct and the ejection duct respectively ranges in particular between 0.2 and 0.5, in particular between 0.3 and 0.4 and is preferably 0.35.
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Nilsson et al.,J. Biochemical and Biophysical Methods,27 (1993), pp. 181-190.
Wallman et al.,Transducers 95. Eurosensors IX,Jun. 25-29, 1995, Stockholm.
Guenther Rolf
Henco Karsten
Howitz Steffen
Wegener Thomas
Evotec Biosystem AG
Fastovsky Leonid
Fish & Richardson P.C. P.A.
Walberg Teresa
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