Agitating – Having specified feed means – Plural related feeders having separate outlets to mixing...
Reexamination Certificate
1998-07-15
2001-06-05
Cooley, Charles E. (Department: 1723)
Agitating
Having specified feed means
Plural related feeders having separate outlets to mixing...
C366S337000
Reexamination Certificate
active
06241379
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a micromixer having a mixing chamber that is connected to a first inlet channel arrangement, into the wall of which mixing chamber a second inlet channel arrangement opens by way of at least one opening.
Micromixers of that type are becoming increasingly important in the field of chemical analyses. They have the advantage that only very small amounts of liquids or gases that are to be studied and correspondingly small amounts of reagents are required in order to carry out an adequate analysis. The fluid to be studied and the reagent must be mixed with one another in order to obtain a desired reaction. The desired analysis results can then be determined quantitatively or qualitatively by reference to the reaction product. It is also possible in that manner to mix cells, for example blood cells, or granules with fluids or reagents.
Micromixers can also be used as microreactors. For example, two gases can be mixed that are in themselves non-toxic but that become highly toxic in a mixing process. If that is limited to a small volume, slightly reduced safety measures will suffice in comparison with a larger mixer in which a correspondingly greater volume of toxic gas is produced.
In the case of the small volumes that are supplied to the mixing chamber it is, however, relatively difficult to obtain adequate intermixing of the fluids by turbulence. If the intermixing is limited to processes dominated by diffusion, it is important that the diffusion can be influenced specifically by the appropriate introduction of the different fluids into the mixing chamber.
SUMMARY OF THE INVENTION
The problem underlying the invention is therefore to facilitate rapid and predeterminable mixing of fluids.
That problem is solved in a micromixer of the type mentioned at the outset by the fact that there is arranged on the wall adjacent to the opening at least one projection that extends transversely to the direction of flow, the extent of which is greater than the extent of the opening transverse to the direction of flow.
The flow is disrupted by the projection. The fluid from the first inlet channel arrangement, which may, of course, have a plurality of inlet channels, must flow around the projection. When the fluid from the second inlet channel arrangement is then fed into the mixing chamber in precisely that region, it can spread out perpendicularly to the wall into the depth of the mixing chamber significantly better than without disruption caused by the projection. This can be seen clearly when the projection lies in front of the opening in the direction of flow. The opening then lies as it were in the lee of the projection. A fluid that enters the mixing chamber from the second inlet channel arrangement through the opening in the wall can then, protected by the projection, first spread out a little in the mixing chamber before coming into contact with the fluid that is supplied from the first inlet channel arrangement in the direction of flow. That enables the two fluids to be applied to one another advantageously. Diffusion can then take place along the resulting interface, as a result of which the two fluids, for example, a sample and a reagent, are mixed. Surprisingly, however, results that are still usable are obtained when the projection is arranged behind the opening in the direction of flow.
Preferably the projection is located substantially perpendicularly on the wall. That facilitates manufacture. No undercuts or other shapes that are difficult to manufacture need to be formed. The term “perpendicular” is, of course, intended in this case to mean only that which is technically feasible. In some etching processes it is nearly impossible to produce truly perpendicular walls.
It is also advantageous for the projection to extend as far as a covering wall that is opposite to the wall. That provides very good sheltering of the opening so that the entry of the fluid from the second inlet channel arrangement into the mixing chamber is protected. It also provides specific formation of the interface between the two fluids substantially perpendicular to the wall that has the opening. That gives rise to specific layering of the fluids in the mixing chamber combined with mixing by diffusion that can be controlled correspondingly well.
Advantageously the projection is arranged so that at least a portion of its extent is in a region in front of the opening in the direction of flow. As a result, already in a region in front of the opening, defined flow relationships are obtained for the fluid from the first inlet channel arrangement or for the fluid from the second inlet channel arrangement, depending on whether the projection covers the opening so as to shelter it or not.
It is especially preferred for the projection to be of U-shaped construction having two legs, the opening being arranged in the region of a connection between the two legs. As a result, the fluid can flow through the opening into the mixing chamber and can first spread out between both legs of the U before coming into contact with the fluid from the first inlet channel arrangement. As a result, a layer-like flow of the fluid from the second inlet channel arrangement is obtained, onto which is added or laminated from both sides the fluid from the first inlet channel arrangement. That layered structure is obtained without having to undertake complicated canalization in the third dimension. In general, it is sufficient for the fluids to be channelled in one plane, apart from the fact that the opening, of course, requires a step into a different plane.
It is especially preferred for the length of the legs to be a multiple of the distance between the legs or of the height of the projection. In that case, at the outlet of the U a high-quality laminar flat flow of fluid from the second inlet channel arrangement is obtained, onto which there can be adjoined a similarly laminar flow of the fluid from the first inlet channel arrangement. Excellent layering of the fluids can be obtained as a result; when fluid flows around both sides of the projection, the first fluid, that is to say the fluid from the first channel arrangement, is added to the second fluid, that is to say the fluid from the second channel arrangement, from both sides. Thus, two interfaces and, accordingly, double the diffusion surface are obtained. In addition, the diffusion lengths are shortened because the individual molecules must cover only half the distance in order to penetrate the other fluid, with the result that very rapid mixing of the two fluids can be obtained even when the mixing process is based solely or mainly on diffusion.
Preferably the legs are of flat, especially planar, construction and run parallel with one another. As a result, already shortly after being fed through the opening into the mixing chamber, a flow layer having a laminar structure is produced, onto which layers of the other fluid can be laminated from both sides once it has left the intermediate area between the two legs of the U. The formation of such a layer is also improved when the width of the opening corresponds approximately to the distance between the legs. The intermediate area between the two legs can then be filled across its width uniformly and almost without turbulence. The legs are preferably planar. They may alternatively be bent if the fluid from the first inlet channel arrangement is channelled in a correspondingly bent flow path.
In an alternative construction the projection may be of V-shaped construction. Such a construction also renders it possible for the fluid from the second inlet channel arrangement that enters the mixing chamber through the opening to be able first to spread out in the mixing chamber before coming into contact with the fluid from the first inlet channel arrangement. In that manner also, the two fluids can be applied to one another excellently.
Advantageously the mixing chamber has an outlet, the width of which is reduced in size in a direction parallel with the wall. In order to obtain as rapid int
Cooley Charles E.
Danfoss A/S
Lee Mann Smith McWilliams Sweeney & Ohlson
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