EP2321538B1 - Microfluid device - Google Patents

Description

The present invention relates to microfluidic devices for dispensing fluids or fluid mixtures.

Well-mixed fluid mixtures are useful in laminar flow systems, e.g. in microfluidic systems, difficult to produce, since - especially due to lack of turbulence, but also due to short path lengths - to a sufficient mixing of the supplied fluids, especially in the case of liquids can come. The mixing between different fluid streams flowing in a channel is thus almost exclusively limited to diffusion processes. In addition, in microfluidic applications, cable routing is problematic because of the difficult-to-use third dimension.

One approach to solving these problems is, for example, in DE 19604289 C2 discloses where, in a so-called micromixer, two fluid streams are introduced into a mixing chamber on either side of a dividing wall and are thereafter joined together to form an interface therebetween, at which diffusion can take place.

The problem of the wiring and the pressure loss in the supply lines and at the junction point of the same in the mixing channel are not addressed in this document.

In terms of balancing pressure losses revealed EP 1 187 671 B1 the introduction of several fluids via inlet channels with correspondingly different tapered cross-sections into a mixing chamber of a "micromixer". The taper of the channels extends longitudinally, ie towards the mixing chamber, and the surface of the inlet openings is normal to the longitudinal axis thereof. The channels cross each other without contact and form a common outlet cross section at the mixing chamber. This pressure losses are compensated in the supply lines. The problem that with lateral supply of fluids due to pressure losses in the transverse direction of a mixing channel different amounts of fluid in these are introduced does not occur in this embodiment of a microfluidic device and therefore remains unmentioned.

document US - A1 - 2005/133457 discloses a microfluidic device according to the preamble of claim 1.

DISCLOSURE OF THE INVENTION

According to the invention, this object is achieved by providing a microfluidic device for dispensing a fluid or fluid mixture, comprising: an output channel, at least one main fluid supply channel, each into at least one secondary supply channel substantially in the plane of the dispensing channel and laterally thereof passes, which in turn merges into an above or below the output channel lying inlet channel, the at least over an inlet opening opens from above or below into the dispensing channel, with the characteristic that the at least one inlet channel has a cross section with a cross-sectional shape that changes linearly or exponentially in its longitudinal direction. A further embodiment of the microfluidic device according to the invention may be distinguished by the fact that the at least one inlet opening has an opening width which changes in the transverse direction of the outlet channel.

Because of this longitudinally varying cross-sectional shape of the inlet channel and / or varying width of the inlet opening (s) in the transverse direction of the dispensing channel, varying amounts of fluid can be introduced from the latter into the dispensing channel at different locations of the inlet channel. Depending on the shape, locally variable pressure conditions are created, and thus the flow rate and consequently the amount of fluid across the width of the discharge channel are determined. For example, the unequal amount of fluid delivered into the dispensing channel due to the pressure difference between the two ends of the inlet channel (s) may be compensated for by widening the inlet channel to the farther end so that there is a larger interface between Inlet and outlet channel for fluid transfer is available. As a result, a uniformly thick fluid layer over the width of the discharge channel can be introduced into the latter. Depending on the application of the device in piping systems, smaller or larger amounts of fluid, e.g. a fluid gradient may be introduced into it, which may be useful not only for mixing but also, for example, for chemical reactions in that channel.

As for the above designations "up" and "down" and "above" and "below the level of the output channel", it should be noted that these are interchangeable and present due to the variable spatial location of the output channel, even after the microfluidic device has been powered up all for a more detailed explanation of the embodiments shown in the accompanying drawings.

The fluid (s) is / are not specifically limited. It may be any flowable materials or mixtures thereof. Preferably, the invention is used in connection with liquids or liquid / gas mixtures, since the advantages of the invention are particularly effective here. According to the present invention, one or more inlet openings may be provided in the discharge channel for each inlet channel. In the former case, the single inlet opening can be formed from the upper edges of the inlet channel, which is completely open towards the outlet channel, and thus occupies the entire interface between the inlet channel and the outlet channel. This simplifies the manufacture of such microfluidic devices, as will be described later. The shapes of the inlet channels and the respective inlet openings may be the same or different from each other in all embodiments of the invention, which enables a targeted adjustment of the amount of fluid entering the zone across the width of the outlet channel. For example, the inlet channel in the region of the junction, for example, wedge-shaped, taper or widen, while the inlet opening, for example, has a regular rectangular shape. As an alternative or in addition to this, a plurality of openings, for example slot-shaped or circular or even oval, can be provided per single-channel (which sometimes has a changing cross-section), etc.

The manner in which the cross-sectional shape of the at least one inlet channel or the shape of the at least one inlet opening changes is not particularly limited and can be adapted to the respective applications of the device. According to the invention, the cross-sectional shape changes linearly, since the pressure loss over the length of the channel can thus be well compensated and a uniform distribution of the fluids or fluid mixtures in the transverse direction of the discharge channel is ensured. The resulting fluid flow behavior can be well simulated and optimized by means of computer programs. Because the pressure drop in the channels is exponential, for purely physical considerations, a corresponding exponential change in cross-section would be an even better solution to this problem. Such courses are in practice - at least in the current production techniques - but only at much higher cost feasible and therefore currently not preferred. However, with the expected progress of manufacturing processes in the coming years, such cross-sectional shapes may soon be producible with reasonable effort. Preferably, the width of the at least one inlet channel increases in the transverse direction of the discharge channel, ie at the end there is a larger area for the fluid transfer from the respective inlet channel to the outlet channel, so as to compensate for the pressure drop. The width of the inlet channel can increase both at its upper and lower edges and at only one of them. That is, the inlet duct does not necessarily have to have side walls normal to the plane of the discharge duct, as will be explained later. Also, a variable depth of the channels affects the feed into the dispensing channel, but a depression of the inlet channels towards their end tends to increase the pressure drop due to the larger cross-sectional area, while the decreasing depth (and concomitant smaller cross-sectional area) again compensates for the pressure drop can be.

By the shape and nature of the cross section of the channels, for example in a round or angular shape, with a rough or smooth surface, by the length of the channels and by the shape of the channels -. forming round or square branches - the flow rate of the fluid to the inlet ports can be determined. These means according to the invention can be used both instead of and in combination with other, for example, mechanical control means, e.g. Micropumps, valves, etc. are used.

In further preferred embodiments of the invention, all inlet openings are arranged on the same side of the discharge channel, ie above or below it, as in the later discussed in more detail Fig. 3 and 5 is shown schematically, where all inlet channels are shown from below the discharge channel in this merging. This arrangement is easier to manufacture in the manufacture of microfluidic devices.

In preferred embodiments, the main supply channels merge into a plurality of sub-supply and associated intake ports, and also preferably, a plurality of main supply ports are provided. These preferably comprise one or more first main feed channels for introducing a first fluid and one or more a plurality of second main supply channels for introducing a second fluid. This makes it possible to introduce several layers of fluids, also in each case several layers of several fluids, one above the other into the discharge channel, which improves and accelerates the mixing of two or more fluids, since more than one interface between the fluids is available for the diffusion.

Again, especially adapted to the manufacturing conditions of microfluidic applications, the sub-feed and associated multiple-fluid inlet channels preferably lead from opposite sides to the dispensing channel because, due to the difficult-to-use third dimension, superposition of the channels in microfluidic devices is hardly possible. For introducing a plurality of layers of a plurality of fluids, preferably a plurality of first secondary supply and inlet channels and a plurality of second secondary supply and inlet channels are "comb-shaped" from opposite sides (as will be explained in more detail below), interlocking with and discharging into the dispensing channel.

The device according to the invention also makes it possible to combine immiscible liquids, so that a solute can diffuse from one phase into the immiscible other phase. In this application, the device does not serve as a mixer, but as a micro-extractor.

By the device according to the invention a well controllable mixing by diffusion of two or more layers of miscible fluids is possible. This achieves a reproducible diffusion mixing time behavior whose behavior depends on the properties of the fluids used (inter alia the diffusion coefficient), the flow rate and the layer thicknesses. In this way, a higher mixing quality is achieved compared to the prior art.

In a second aspect, therefore, the invention relates to the use of a just described device for dispensing a plurality of fluids, which are preferably dispensed in the form of layers. The layers can be the same or different Have layer thicknesses, as this is determinable over the cross section of the inlet channels and / or the inlet openings. Preferably, the fluids are at least partially mixed during delivery due to diffusion at the interfaces between the layers.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 ist eine schematische Darstellung eines eingangs beschriebenen Mikromischers nach dem Stand der Technik.
• Fig. 2 ist eine schematische Darstellung einer Ausführungsform der erfindungsgemäßen Vorrichtung zur Einleitung eines Fluids über einen sich in zwei Nebenzufuhr- und Einlasskanäle verzweigenden Hauptzufuhrkanal in einen Ausgabekanal.
• Fig. 3 ist eine Längsschnittansicht der Ausführungsform aus Fig. 2 entlang der Linie A-A.
• Fig. 4 ist eine Querschnittansicht dreier möglicher Ausführungsformen der Vorrichtung aus Fig. 2 entlang der Linie B-B.
• Fig. 5 ist eine schematische Darstellung einer Ausführung der erfindungsgemäßen Vorrichtung zur Einleitung zweier Fluids über "kammförmig" ineinander greifende Einlasskanäle in einen Ausgabekanal.
• Fig. 6 ist eine Querschnittsansicht der Ausführungsform aus Fig. 5.
• Fig. 7 ist eine schematische Detailansicht verschiedener Ausführungsformen eines Einlasskanals mit sich änderndem Querschnitt.
• Fig. 8 ist eine schematische Detailansicht verschiedener Ausführungsformen von Einlassöffnungen in den Einlasskanälen.
• Fig. 9 ist eine Längsschnittansicht alternativer Ausführungsformen der Vorrichtung aus Fig. 2 entlang der Linie A-A.

The present invention will now be further described with reference to the accompanying drawings, in which:

• Fig. 1 is a schematic representation of an initially described micromixer according to the prior art.
• Fig. 2 is a schematic representation of an embodiment of the device according to the invention for introducing a fluid via a branched into two sub-supply and inlet channels main supply channel into an output channel.
• Fig. 3 is a longitudinal sectional view of the embodiment of Fig. 2 along the line AA.
• Fig. 4 Figure 4 is a cross-sectional view of three possible embodiments of the device Fig. 2 along the line BB.
• Fig. 5 is a schematic representation of an embodiment of the device according to the invention for introducing two fluids via "comb-shaped" intermeshing inlet channels in an output channel.
• Fig. 6 is a cross-sectional view of the embodiment of Fig. 5 ,
• Fig. 7 is a schematic detail view of various embodiments of an intake duct with changing cross-section.
• Fig. 8 is a schematic detail view of various embodiments of inlet openings in the inlet channels.
• Fig. 9 is a longitudinal sectional view of alternative embodiments of the device Fig. 2 along the line AA.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Fig. 1 As mentioned, a known embodiment of a microfluidic device according to the prior art. In this apparatus, three separate feed channels 2, 2 ', 2 "for liquids in a row in a, here horizontally extending mixing channel 5. In the accompanying, cited publication, a stream of a liquid sample is passed between each buffer stream in the channel, in order to mix them in. The feed of the three streams takes place from the same side of the mixing channel 5 - in Fig. 1 , seen in the direction of flow of the fluid in the mixing channel 5: from the left - via separate supply channels 2, 2 ', 2 ", which must be fed separately due to the impossibility to provide intersecting lines, Such a construction is common in the production of microfluidic devices and at the same time indispensable, since here the channels and other components are usually etched, fired, melted or cut into a carrier, because of this method of manufacture, the fluid conduits of such microfluidic devices are commonly referred to as channels, although they are replaced by the application of a cover plate after completion of the etching. or cutting operations of closed lines - in contrast to the term "channel", as it is used in other areas of technology, for example in construction technology.

While the field of microfluidics is defined differently in the literature, for purposes of the present invention, it is meant to include devices having such dimensions that the cross-sectional area of the channels is on the order of square millimeters or less.

One of the problems of such and similar devices solved by the invention is that the amount of fluid entering the mixing channel at both ends of the respective inlet channel is different due to the pressure drop from one end to the other.

In Fig. 2 a simple embodiment of a microfluidic device according to the invention is shown, which serves mainly to illustrate the principle of the invention. In practice, such a device could not serve as a micromixer but, for example, as a connector between two (micro) lines extending in different spatial directions or as a simple channel for fluid (especially liquid) delivery, eg in inkjet printers.

Anyway, in the in Fig. 2 shown device a fluid are directed into an output channel 5, as indicated by the arrows. The fluid is branched via a main supply channel 1, which branches off into two secondary supply channels 2, 2 ', which in turn pass into two inlet channels 3, 3' to the output channel 5 and through inlet ports 4, 4 ', which are shown in dotted lines in the figures ,

The cross-sections of both the inlet channels 3, 3 'and the inlet openings 4, 4' extend linearly in the mouth region, whereby although the pressure loss in the longitudinal direction of the inlet channels increases, but an increasingly larger cross-section for the fluid transition into the output channel 5 is available, whereby this pressure loss - depending on the angle of the extension - can be compensated.

Thus, the present invention makes it possible to compensate for the pressure losses occurring in the case of elongated line junctions and the different quantities of fluid delivered in connection therewith, wherein the cross-sectional shapes of the inlet channels or inlet openings can be adapted precisely to the respective conditions.

In addition to the cross-sectional shape of the channels in the longitudinal direction, those in the transverse direction, where, for example, round, oval or polygonal cross-sections can be used, are essential, so that not necessarily parallel vertical side walls of the channels must be present. This also affects the pressure ratios in the respective sections of the channels. Two exemplary embodiments of inlet channels with non-parallel sidewalls are shown in FIG Fig. 9 and will be described later. However, the main and sub-feed channels may also have such non-parallel walls.

According to the present invention, the cross-section of the respective inlet channel, that of the associated inlet opening (s) or even both may change. In all figures, by way of example, a "wedge-shaped", i. linear variation of the cross sections shown, the course of which is also the same at the inlet channel and opening, as indicated by the parallelism of the lines. In practice, however, any combination of different cross-sectional shapes can be used, as long as characterized the flow behavior of the fluid or in the device according to the invention is influenced in an advantageous manner. In addition to linear changes, any other shapes, with curves, waves, corners, edges, teeth and the like, are possible, all of which are intended to be within the scope of the present invention.

As already mentioned, in the practice of microfluidic devices, there is often no explicit "inlet opening" in the channel 5. Rather, the inlet channels in the mouth region are simply open towards the channel 5, so to speak a single, the entire top of the channel 3 in the mouth region engaging opening 4 present.

By suitable design, especially with slightly larger dimensions near the millimeter range, but quite a number of inlet ports per inlet channel may well be provided, which in turn may have any desired shapes. Thus, for example, a sequence of slot or circular openings - in the longitudinal and / or transverse direction - thinkable and feasible, through which fed in the inlet channel Fluid enters the dispense channel at multiple, discrete locations.

Also possible is a combination of an inlet channel with linear, e.g. wedge-shaped or conical, or curved tapered cross-section and extending in the longitudinal direction of the inlet channel, slot-shaped inlet opening with a regular rectangular cross-section. The tapering cross-section of the channel then equalizes the pressure drop toward the farther end of the opening so that in turn equal amounts of fluid can enter the discharge channel at both ends of the opening.

In addition to the changing cross-sectional shape in the mouth region, the cross-section of the inlet or inlet channel upstream of the junction can also change in order to influence pressure differences in the supply lines. This can be done in a known manner, ie as in the aforementioned EP 118,767 B1 , Made by tapering design of the channels 1 and / or 2 or 2 'to the output channel 5 out. In this way, it can be ensured that the same amount of fluid is delivered to all inlet channels in the case of a main feed channel branching into a plurality of secondary feed and corresponding inlet channels, which results in equal layer thicknesses of the fluid in the output channel. On the other hand, it is also possible to selectively deliver different amounts and thus to produce different layer thicknesses of several layers of the same fluid, if this is advantageous for the respective application. How strong the pressure drop within the supply or inlet channels is, of course, depends on their length and thus also on the distance of the junctions of the inlet channels in the output channel. The cross-sectional changes must be adjusted accordingly in the respective individual case.

Fig. 3 shows a schematic longitudinal sectional view of the embodiment Fig. 2 along the line AA, from which it can be seen that both inlet channels 3 and 3 'open into the outlet channel 5 from the same side, namely from below. This is contrary to the manufacturing technology of microfluidic devices. In addition, the side walls of the inlet channels 3 and 3 'are formed in parallel. Alternatives will be discussed later Fig. 9 described.

Fig. 4 schematically shows three possible cross-sectional views of the embodiment Fig. 2 along the line BB. It can be seen that the cross-section of the inlet channel 3 'not only - as in Fig. 2 shown - may increase in the plane of the output channel 5, so that it widened in the flow direction of the fluid, but can also increase or decrease perpendicular thereto. In Fig. 4a the inlet channel 3 'deepens over the width of the output channel 5, and in Fig. 4b its depth decreases. The latter case causes an increase in the pressure toward the end of the inlet channel 3 ', whereby the pressure drop in the longitudinal direction of the inlet channel 3' can be compensated - or even a targeted in this direction increasingly larger amount of fluid in the output channel 5 can be initiated. At a recess of the inlet channel, as in Fig. 4a In contrast, the pressure drop is increased by the enlargement of the channel cross-section, so that at the end of the inlet channel 3 'specifically smaller amounts of fluid can be introduced into the output channel 5. Fig. 4c shows an embodiment with a constant depth of the inlet channel 3 ', which represents a presently preferred embodiment due to the simpler manufacturing.

Fig. 5 shows an embodiment of the device according to the invention, in which two fluids are supplied from opposite sides of the discharge channel 5 to this. A first fluid is analogous to the embodiment Fig. 2 via a main supply channel 1, which branches into two secondary supply channels 2 and 2 'and in the sequence in two inlet channels 3 and 3', introduced; a second fluid via the analog components 10, 20/20 'and 30/30'. The changing in the mouth region cross-sectional shapes can be combined again as desired. For clarity, wedge-shaped cross sections are again shown. For reasons of saving space in the production of such microfluidic devices, in practice, the wedge-shaped extensions of the inlet channel pairs would be 3/30 and 3 '/ 30' facing each other, ie the channels 30 and 30 'in the drawing would not be right up but extend to the top left.

Furthermore, it will be appreciated that in this embodiment, no explicit inlet openings are provided, since the inlet channels 3/3 'and 30/30' are open towards the top of the dispensing channel 5, so that in each case the entire, formed by the upper edges of the inlet channels with the output channel 5 represents the respective inlet opening.

The total of four secondary supply channels 2, 2 ', 20, 20' with their inlet channels 3, 3 ', 30', 30 engage "comb-like" in one another, meaning that they alternately open into the output channel 5 from opposite sides. In this way, two layers of the two fluids are alternately introduced into the output channel, whereby a total of three interfaces for the diffusion between the two fluids are available. With an even higher number of branches, this effect can be further enhanced. This significantly speeds up mass transfer between the fluids such that such devices are excellent micromixers or, for immiscible liquids, microextractors.

One application is about the production of micro-fluid mixtures with a high mixing quality. For the development of new drugs, the optical detection of chemical properties and reactions is becoming increasingly important. To obtain satisfactory results, the rapid and high quality mixing of fluids is particularly important here.

For the preparation of such fluid mixtures, it makes sense to use more than two layers of fluids in order to minimize the diffusion paths. At the same time, any flows occurring in a direction other than in the direction of flow must be distributed as homogeneously as possible over the cross section of the discharge channel.

In order to achieve this, a profile of the device according to the invention with an aspect ratio of 1:10 for the inlet channels and / or the inlet opening is used for many-in particular aqueous-fluids. Under an aspect ratio (width difference: length) of 1:10, an expansion of the (eg wedge-shaped) Channel of, for example, 10.0 microns at the beginning of the inlet channel to 20.0 microns at its end over a length of the inlet channel of 100.0 microns understood. As a result, a readily reproducible time behavior of the mixing is achieved by diffusion of two or more fluids, the quality of the mixing also being decisively influenced by the mixing behavior (diffusion coefficients) of the fluids and the flow velocities.

In the Fig. 5 Accordingly, the embodiment shown, as well as the previously discussed embodiment of FIG Fig. 2 to 4 the problem of pressure differences in the junction area in the outlet channel. At the same time, however, the supply of two different fluids from opposite sides is a new and advantageous solution to the problem of routing in microfluidic devices. Namely, because of the difficult-to-use third dimension, intersecting lines are hard to manufacture, so that multiple supply passages - and not just inlet passages - were required for alternately supplying multiple streams of the same fluid Fig. 1 was explained.

Fig. 6 shows a longitudinal sectional view of the embodiment Fig. 5 along the line AA Fig. 5 , From this it follows that all inlet channels 3, 3 ', 30 and 30' from the same side - again from below - open into the outlet channel 5. This again counteracts the fabrication technique of microfluidic devices where the channels are etched into an existing substrate, cut, etc. Because the line AA in Fig. 5 is not halfway across the discharge channel 5, the thickness of the inlet channel pairs 3/3 'and 30/30' is also different due to the different degree of broadening at that location. Again, the walls of the inlet ducts need not necessarily be perpendicular, that is, they should be normal to the plane of the discharge duct, as in FIG Fig. 6 is shown. By the inlet channels becoming wider or narrower towards the bottom, the amount of fluid passing from the respective inlet channel into the outlet channel and thus the layer thickness of the fluid at that point of the outlet channel can also be controlled. Such a change in cross section of the inlet channels is also within the scope of the present invention.

Fig. 7 shows by way of example schematically different embodiments of the cross-sectional changes of the inlet channels in the plane of the discharge channel. As can be clearly seen, widening as well as narrowing shapes over the width of the dispensing channel 5 as well as arbitrary combinations thereof, as well as combinations of a straight and an oblique or curved longitudinal wall of the inlet channel 3, are possible. Widening shapes are preferred in order to compensate for the smaller amount of fluid due to the pressure drop over the length of the inlet channel 3, which at its end passes into the discharge channel 5. Such and similar, but also any other cross-sectional changes are also possible for the depth of the inlet channels, as already stated above. This means that even the depth of an inlet channel need not necessarily increase or decrease linearly in order to ensure optimum, desired flow conditions for the fluid (s) in the device according to the invention.

Fig. 8 shows various embodiments of the shapes of the inlet openings, for the sake of clarity, the inlet channels are plotted without changing cross-section. In fact, however, any combinations of the in the Fig. 7 and 8th shown embodiments and any other embodiments possible, since the invention is not limited to the embodiments shown or discussed herein.

Fig. 9 shows, as already mentioned, alternative embodiments of the inlet channels 3 and 3 'from Fig. 3 with non-parallel sidewalls, which can also be combined with any of the previously described channel cross-section changes and aperture shapes. Channel 3 is shown here by way of example with an oval cross-section, ie with bulged side walls; Channel 3 ', however, with a downwardly tapered cross-section. As already mentioned, additional measures can also be taken on the channel sidewalls, such as grooves, grooves, grooves, corrugations and the like, to influence and optimize the flow behavior of the fluids in the channels.

In summary, it should be noted that the present invention is a valuable extension In the field of microfluidics, the prior art solves existing problems in a relatively simple manner by providing devices which are inexpensive and can be produced by known methods. Accordingly, there is no doubt about the industrial applicability of the invention.

Claims (12)

1. A microfluidic device for dispensing a fluid or a fluid mixture, comprising an outlet channel (5), at least one main fluid supply channel (1, 10) which merges into at least one secondary supply channel (2, 2', 20, 20') which is essentially arranged in the same plane as said outlet channel (5) and laterally leads into it, said secondary supply channel (2, 2', 20, 20') merging into an inlet channel (3, 3', 30, 30') located above or below said outlet channel (5), said inlet channel (3, 3', 30, 30') leading upwards or downwards into said outlet channel (5) via at least one inlet opening (4, 4'),
   characterized in that the cross-sectional shape of said at least one inlet channel (3, 3', 30, 30') changes linearly or exponentially along the inlet channel's longitudinal direction.
2. The microfluidic device according to claim 1, characterized in that the opening width of said at least one inlet opening (4, 4') changes along the transverse direction of said outlet channel (5).
3. The microfluidic device according to claim 1 or claim 2, characterized in that one inlet opening (4, 4') is provided for each inlet channel (3, 3', 30, 30').
4. The microfluidic device according to claim 3, characterized in that said inlet opening (4, 4') is formed by the upper edges of the respective inlet channel (3, 3', 30, 30') which is entirely open towards the above outlet channel (5).
5. The microfluidic device according to claim 1 or claim 2, characterized in that several inlet openings (4, 4') are provided for each inlet channel (3, 3', 30, 30').
6. The microfluidic device according to any one of the claims 1 to 5, characterized in that the width of said at least one inlet channel (3, 3', 30, 30') is increasing.
7. The microfluidic device according to any one of the claims 1 to 6, characterized in that the depth of said at least one inlet channel (3, 3', 30, 30') is increasing.
8. The microfluidic device according to any one of the claims 1 to 7, characterized in that all the inlet openings (4, 4') are arranged at the same side of the outlet channel (5), i.e. above or below it.
9. The microfluidic device according to any one of the claims 1 to 8, characterized in that said at least one main supply channel (1, 10) merges into several inlet channels (3, 3', 30, 30') via several secondary supply channels (2, 2', 20, 20').
10. The microfluidic device according to any one of the claims 1 to 9, characterized in that several main supply channels (1, 10) are provided, comprising at least one first main supply channel (1) for supplying a first fluid and at least one second main supply channel (10) for supplying a second fluid.
11. The microfluidic device according to claim 10, characterized in that said at least one main supply channel (1) merges into at least one first inlet channel (3, 3') via at least one first secondary supply channel (2, 2') and in that said at least one second main supply channel (10) merges into at least one second inlet channel (30, 30') via at least one second secondary supply channel (20, 20'), said first and second secondary supply channels leading into the outlet channel (5) from opposite sides.
12. The microfluidic device according to claim 11, characterized in that several first secondary supply channels (2, 2') and inlet channels 3, 3') and several second secondary supply channels (20, 20') and inlet channels (30, 30') are provided, being provided in an intermeshing, comb-like arrangement to lead to or into the outlet channel (5) from opposite sides.

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