EP2506959B1 - Microfluidic element for analysing a fluid sample - Google Patents

Description

The present invention relates to a microfluidic element for determining an analyte in a fluid sample, preferably in a body fluid sample. The element comprises a substrate and a channel structure which is enclosed by the substrate and a cover layer.

Microfluidic elements for analyzing a fluid sample and mixing a fluid with a reagent are used in diagnostic tests (in vitro diagnostics). In these tests, body fluid samples are analyzed for an analyte for medical purposes. The term mixing comprises both the possibility that the reagent is in liquid form, that is, that two liquids are mixed together. In addition, the term includes the possibility that the reagent is present as a solid and dissolved in a liquid and homogenized. In many applications, the solid dry reagent is introduced into the fluidic element in liquid form and dried in a further step before the element is used for analysis.

An important part of the analysis are test carriers on which microfluidic elements with channel structures for receiving a liquid sample are present in order to enable the implementation of complex and multi-level test procedures ("test protocols"). A test carrier may comprise one or more fluidic elements.

Test carrier and fluidic elements consist of a carrier material, usually a substrate made of plastic material. Suitable materials are, for example, COC (cyclo-olefin copolymer) or plastics such as PMMA, polycarbonate or polystyrene. The test carriers have a sample analysis channel which is enclosed by the substrate and a lid or cover layer. The sample analysis channel often consists of a succession of multiple channel sections and intermediate chambers compared to the channel sections of extended chambers. The structures and dimensions of the sample analysis channel with its chambers and sections are defined by a patterning of plastic parts of the substrate, which are produced, for example, by injection molding techniques or other methods for producing suitable structures. It is also possible to introduce the structure by material-removing methods such as milling.

Fluidic test carriers are used, for example, in immunochemical analyzes with a multi-step test procedure in which a separation of bound and free reaction components takes place. For this purpose, a controlled liquid transport is necessary. The control of the process flow can take place with internal (within the fluidic element) or with external (outside the fluidic element) measures. The control can be based on the application of pressure differences or else the change of forces, for example resulting from the change in the effective direction of gravity. When centrifugal forces acting on a rotating test carrier, a control by changing the rotational speed or the direction of rotation or by the distance from the axis of rotation can be made.

• US 4,456,581
• US 4,580,896
• EP 1 077 771 B1
• EP 1 944 612 A1
• US 2005/0041525 A1

Analysis systems with such test carriers are known, for example, from the following publications:

• US 4,456,581
• US 4,580,896
• EP 1 077 771 B1
• EP 1 944 612 A1
• US 2005/0041525 A1

The US 2005/0041525 A1 describes microfluidic elements and methods for analyzing biological samples and mixing different liquids. The liquids to be mixed are first added from respective containers in a first chamber to combine the liquids. Subsequently, the combined liquids from the first chamber are emptied through at least one capillary connection channel into a second chamber to mix the liquids. In some embodiments, two or more parallel capillary connection paths are used. In a further embodiment, the second chamber is in flow relationship via at least one capillary connection path with at least one third mixing chamber. The transport of the liquids is effected by centrifugal forces and always takes place from the rotation axis closer chamber to the rotation axis remote chamber.

In general, to perform the analyzes, the sample analysis channel of the microfluidic elements contains at least one reagent which reacts with a liquid introduced into the channel. The liquid and the reagent are mixed in the test carrier with each other so that a reaction of the sample liquid with the reagent leads to a change in a measured variable that is characteristic of the analyte contained in the liquid. The measured variable is measured on the test carrier itself. Commonly used are optically evaluable measuring methods in which a color change or another optically measurable variable are detected.

For carrying out the analysis, it is crucial that the reagent present in dried form is dissolved from the sample liquid and mixed with it. In the prior art, some efforts are being made to optimize mixing. For example, in rotating test carriers, which are rotated in an analysis system about an axis of rotation, the mixing is promoted by rapid changes in the direction of rotation. This emerging "shaking mode" (shake mode) is in a special form, for example in Markus Grumann, "Readout of Diagnostic Assays on a Centrifugal Microfluidic Platform", (Dissertation University of Freiburg, 2005, URN (NBN): urn: nbn: de: pp: 25-opus-22723 ).

Other known methods for improving the mixing of sample liquid and reagent include the introduction of magnetic particles, which are caused by the action of an electric or permanent magnet in motion be offset. The integration of the particles increases the effort involved in the production of the test carriers. In addition, the analysis systems must have other components, namely the magnet, and therefore becomes expensive.

Other methods include z. B. elements, the capillary channels contain special flow obstacles. The production of such obstacles, such as ribs, must be formed in the microstructure and are therefore expensive and complicate the manufacturing process of the test carrier. In addition, such structures are not suitable for all mixing processes or not for all reagents and sample liquids.

Despite the many efforts to improve mixing operations in microfluidic elements, especially the mixing of dried solid reagents and sample liquids, there is a further need for a microfluidic element or test carrier in which the mixing of, in particular, small sample liquids is improved. Furthermore, the fluidic element should be suitable for simultaneously mixing different reagents, which are introduced separately and which, for. B. at different spatial locations, dissolve and to allow the sample liquid to react with different reagents.

The existing problem is solved by a microfluidic element having the features of claim 1.

In the following, the invention and its advantages will be described and explained with reference to a test carrier for analyzing a body fluid sample for an analyte contained therein without limiting the generality of a microfluidic element. In addition to body fluids, other sample fluids can also be analyzed.

In the context of the invention, a microfluidic element is understood to mean an element with a channel structure in which the smallest dimension of the channel structure is at least 1 μm and its largest dimension (for example Length of the channel) is at most 10 cm. Due to the small dimensions and the capillary channel structures prevail in the channels or channel sections predominantly laminar flow conditions. The resulting poor conditions for thorough mixing of liquid and solid in such capillary channels are significantly improved by the microfluidic element according to the invention.

The microfluidic element rotates about an axis of rotation. The axis of rotation preferably extends through the microfluidic element. It passes through a predetermined position, preferably z. B. by the center of gravity or the center of the element. In a preferred embodiment, the axis of rotation extends perpendicular to the surface of the fluidic element, which preferably has a flat, disk-like shape and z. B. may be a round disc. For this purpose, the microfluidic element is held for example in a holder of an analyzer, wherein the axis of rotation is formed by a rotary shaft of the device.

By means of a corresponding structuring of a substrate of the element, a channel structure is formed which comprises a feed channel with a feed opening and a bleed channel with a bleed opening and at least two reagent chambers. At least one of the reagent chambers contains a reagent which is preferably in solid form as a dry reagent and which reacts with the liquid sample introduced into the channel structure. Each two adjacent reagent chambers are connected to one another via at least two connection channels such that a fluid exchange between the two reagent chambers is made possible. In this case, one of the reagent chambers has an inlet opening which is in fluid communication with the feed channel so that a liquid sample can flow from the feed channel into the reagent chambers. According to the invention, the liquid sample flows from the feed channel into the reagent chamber, which is further away from the (two) reagent chambers from the axis of rotation. The liquid thus flows into the spin axis remote reagent chamber.

The terms "rotational axis remote" and "rotational axis near" used in the context of the invention do not represent absolute range indications where a structure is located, but indicate how far apart a structure is from the axis of rotation. The axis of rotation is understood as the zero point of a distance scale, which extends radially outward from the axis of rotation. A structure remote from the axis of rotation is, in this sense, further away from the axis of rotation than a structure near the axis of rotation. Thus, a reagent chamber remote from the axis of rotation is the reagent chamber, which is further away from the axis of rotation in relation to another reagent chamber. In the case of two reagent chambers, the reaction chamber remote from the axis of rotation is the chamber which, compared to other chambers, is farthest from the axis of rotation, ie the remainder of the reagent chambers. In an analogous manner, the term "rotation axis" is to be understood. In this sense, a reagent chamber close to the axis of rotation is to be understood as meaning the reagent chamber which, in comparison to the other reagent chambers, is arranged closest to the axis of rotation.

In the context of the invention, it has been recognized that, in contrast to the microfluidic elements known in the prior art, multistage reaction paths are possible with the reagent chambers connected via at least two connecting channels, and the arrangement offers a wide range of control options. In particular, the arrangement makes it possible to dissolve different reagents, which have been introduced separately, without mixing on drying, in a single process step, wherein the dissolution is not impeded fluidically.

The at least two connection channels between the two reagent chambers allow unhindered and rapid fluid exchange. Within the scope of the invention it has been recognized that more than two connection channels are advantageous. Particularly preferred three connection channels are used, the z. B. can be arranged substantially parallel to each other. The reagent chambers are fluidly connected in series through the two connection channels in such a way that a fluid series connection is created.

The reagent chambers are geometrically independent component structures and have their own receiving volume. Fluidically, however, they are together a single fluid chamber. Thus, the positive properties of single reagent chambers are combined with the properties of a single fluid chamber. The solid dry reagents are introduced into the chambers in liquid form and then dried. This drying takes place either by heating or by freezing, which preferably takes place at temperatures of below -60 ° C., particularly preferably at about -70 ° C. Preferably, the test carrier to improve the drying of the liquid reagent, pre-cooled. Especially with "surfactant-containing" reagents, the "cold drying" by freezing is preferred.

Since the reagent chambers are geometrically separated from one another, different reagents can be introduced into each of the reagent chambers without the reagents being mixed before or during drying. This is supported by a corresponding geometric design of the reagent chambers. For example, the chambers may be separated by sharp boundaries such as ridges or edges to prevent crosstalk due to creep effects. The sharp-edged boundaries also form a barrier for transporting the fluid out of a reagent chamber. However, this can be easily overcome by the external forces (centrifugal force, hydrostatic force). By being able to fill each chamber with a different reagent, several (different) reagents can be dissolved and homogenized in just one process step.

The arrangement of the reagent chambers of the channel structure is designed in such a way that one of the chambers is arranged to be more remote from the axis of rotation than the other chamber, ie the distance of the one reagent chamber remote from the axis of rotation from the axis of rotation is greater than the distance of the other chamber. As a result of the rotation of the microfluidic element, the liquid introduced into the channel structure is first conducted into the chamber remote from the axis of rotation, so that this chamber is filled first and the chamber deposited in the chamber Reagent is dissolved. The liquid reacts with the reagent. The amount of liquid and the volume of the first reagent chamber are matched to one another.

Only when a larger amount of liquid is added to the channel structure or flows from the supply channel into the reagent chambers, the second (and possible other rotationsachsennähere) reagent chamber is filled. In this way, even reagents with small amounts of sample can be solved very well. Thus, first the reagent chamber is filled which is furthest away from the axis of rotation. The (closer to the farthest reagent chamber) arranged closer to the axis of rotation chambers are filled only in one or more further steps, the order of filling depends on the distance to the axis of rotation. The reagent chamber with the smallest distance to the rotation axis is filled last. In the context of the invention, it has been recognized that in completely filled reagent chambers, a release of the reagents is more reliable, more complete and faster than in only partly filled chambers. By arranging a plurality of reagent chambers with relatively small partial volume, z. B. 2, 3, 4, 5, 6, 8, 10, 12, 15 etc. chambers, a good mixing for a large number of different volumes can be achieved. For example, three or five of z. B. 12 reagent chambers are filled with the volume to be tested, with all (e.g., three or five) chambers completely filled. If all reagent chambers are filled with the same reagent or the same composition of reagents, a very good mixing with the reagents can be achieved in this way for different volumes of sample liquid.

In a preferred embodiment, the two (or more) connecting channels between two adjacent reagent chambers are arranged in parallel. The spaced (separate) connection channels are preferably formed by straight channel sections. Preferably, the length of at least one of the connection channels is smaller than the smallest dimension of the reagent chambers in the test carrier plane. The test carrier level is the level which extends perpendicular to the surface normal of the test carrier, for example, perpendicular to the axis of rotation.

Advantageously, one of the at least two connecting channels is arranged centrally between adjacent reagent chambers. He aligns with the centers of the two reagent chambers that he connects. Preferably, the (other) connecting channel is laterally connected to the reagent chambers such that it extends outside the central axis connecting the centers. It is particularly preferably arranged tangentially to the reagent chambers that its outer side (outer wall) is aligned with the outer walls of the reagent chambers. Preferably, the centric connection channel is wider (it has a larger cross-section at the same channel height) than the laterally arranged channel.

The connection channels between two adjacent reagent chambers are designed such that, when filling the reagent chamber arrangement, the liquid can flow through the connection channels from one chamber into the second. The liquid preferably flows through one of the connecting channels. At the same time, the air contained in the not yet filled chamber can escape through the other of the two channels, that is, the channel not wetted by the liquid, preferably through the central connecting channel.

Particularly preferred is an embodiment with three connecting channels between two adjacent reagent chambers. In this case, a connecting channel extends along the central axis, which connects the centers of two adjacent reagent chambers. The two other connection channels are preferably arranged tangentially to the reagent chambers. When filling the reagent chambers, the reaction chamber remote from the axis of rotation is first filled. For this purpose, liquid is passed through the (tangential) connecting channel, which is adjacent to the inlet opening, into the chamber remote from the axis of rotation. When filling the reaction chamber remote from the axis of rotation air escapes through the two other communication channels (the middle and the second tangential channel) until the reagent chamber is filled. At another Filling the air in the other two connecting channels is displaced by liquid, so that further filling of the rotational axis near the reagent chamber initially takes place through the two other connecting channels and finally via the first connecting channel which is adjacent to the inlet opening.

In an arrangement of a fluidic element having three or more reagent chambers, the at least two connection channels (preferably three connection channels) are each arranged between two adjacent reagent chambers. Two reagent chambers are adjacent when no further reagent chamber is arranged between them and a fluid exchange between them takes place directly via the at least two connection channels, without further fluidic structures being interposed therebetween.

1. 1. Mit zwei miteinander verbundenen Reagenzkammern ist eine zweistufige Reaktionsführung möglich. In einem ersten Schritt wird dabei eine Flüssigkeitsmenge, die dem Volumen der ersten Reagenzkammer entspricht, in die erste, rotationsachsenferne Reagenzkammer geleitet. Das darin enthaltene Trockenreagenz wird aufgelöst, so dass die erste Reaktion stattfinden kann. In einem weiteren Schritt wird eine zweite Flüssigkeitsteilmenge in die Anordnung der Reagenzkammern gefüllt, wobei die zweite Teilmenge dem Volumen der zweiten Reagenzkammer entspricht. Diese zweite Teilmenge der Flüssigkeit kann beispielsweise ein Puffermedium sein. Der Füllvorgang findet dadurch statt, dass die zusätzliche zweite Teilmenge durch die Zentrifugalkraft zunächst in die erste Kammer gedrückt wird und sich mit dem dort vorhandenen Fluid vermischt und erst dann in die zweite Reagenzkammer strömt. Durch eine entsprechende Steuerung der Rotationsgeschwindigkeit und Rotationsrichtung beginnt ein Mischvorgang, bei dem das Reagenz in der zweiten Reagenzkammer aufgelöst wird und eine zweite Reaktion mit dem zweiten Reagenz stattfindet. Da bei dem Anlösen jeweils beide Reagenzkammern vollständig gefüllt sind, wird eine gute Homogenisierung und Durchmischung in den unterschiedlichen Phasen in jeweils beiden Kammern erzielt.
2. 2. Die Reagenzkammeranordnung bietet den Vorteil, dass ein optimiertes Anlösen eines Trockenreagenz in der rotationsachsenfernen ersten Kammer dadurch stattfindet, dass diese Kammer jeweils von dem gesamten Füllvolumen mehrfach, beim Vorhandensein von zwei Reagenzkammern zweifach durchströmt wird. Zunächst findet ein Durchströmen der ersten Reagenzkammer beim Füllen der Kammer statt. Das zweite Durchströmen findet beim Entleeren der Struktur statt. Auf diese Weise wird eine besonders gute Auflösung der Trockenreagenzien erzielt. Dies hat den weiteren Vorteil, dass auch die beim Eintrocknen von Reagenzien entstehenden Agglomerate, die durch die Zentrifugalkraft radial nach außen in die erste Kammer gedrückt werden, beim anschließenden Entleeren mit dem Fluid aus den radial innen liegenden Kammern "nachgespült" werden. Verluste an der Innenoberfläche der ersten Reagenzkammer werden vermieden.
3. 3. Mit der erfindungsgemäßen Anordnung lassen sich auf einfache Weise Verdünnungsreihen realisieren. Da die Anordnung der Reagenzkammern eine sehr kompakte Kanalstruktur ermöglicht, können auf einem Testträger mehrere Kanalstrukturen ausgebildet sein. Zur Durchführung einer Verdünnungsreihe wird in den parallel angeordneten Kanalstrukturen jeweils nur die rotationsachsenferne erste Reagenzkammer mit Reagenzien bestückt. Zur Durchführung einer Verdünnungsreihe werden die parallelen Strukturen mit unterschiedlichen Volumina gefüllt, so dass für eine definierte Reagenzmenge unterschiedliche Verdünnungen in nur einem Prozessschritt erzeugt werden können. Der Vorteil einer derartigen sequentiellen Mikroreaktorkaskade mit einer so genannten Perlenkettenstruktur (Reihenschaltung von mehreren Kammern) liegt darin, dass die komplette Reaktion mit variablen Volumina durchgeführt werden kann, ohne Änderungen in der Geometrie der Kanalstruktur vornehmen zu müssen. Dabei ist das geringste Volumen der Probenflüssigkeit so groß wie das Volumen der ersten Reagenzkammer. Bevorzugt sind die zu untersuchenden Volumina ein Vielfaches der vorzugsweise gleichen Volumina der einzelnen Reagenzkammern.
4. 4. Ein weiterer Vorteil der Reagenzkammerstruktur liegt darin, dass die einzelnen Reagenzkammern auf die zu untersuchenden Teilvolumina abgestimmt sein können. Im Rahmen der Erfindung wurde bei Untersuchungen zum Anlöse- und Mischverhalten erkannt, dass bei vollständig gefüllten Kammern die Mischvorgänge optimiert ablaufen. Steht beispielsweise in einem ersten Befüllungsschritt nur eine Teilmenge des Fluids zur Verfügung, beispielsweise ein Verdünnungspuffer, der erst später mit einer Probenflüssigkeit aufgefüllt wird, so würde in einem "Ein-Kammer-System" die Homogenisierung mit der ersten Teilmenge nur sehr schlecht ablaufen, da Lufteinschlüsse gebildet werden würden. In einer Reagenzkammeranordnung mit mehreren Reagenzkammern sind die Kammern jeweils auf das Teilvolumen der zu untersuchenden Flüssigkeit ausgelegt und ermöglichen so ein optimiertes Anlösen und Mischen, da die einzelne Reagenzkammer von dem Flüssigkeitsteilvolumen komplett gefüllt wird. Auch ein Schäumen der Lösung wird verhindert.

The channel structure according to the invention with at least two reagent chambers, which are directly connected to one another by at least two connecting channels, offers high flexibility, a space-saving and compact arrangement and a number of functional advantages:

1. 1. With two interconnected reagent chambers a two-stage reaction is possible. In a first step, an amount of liquid corresponding to the volume of the first reagent chamber is guided into the first reagent chamber remote from the axis of rotation. The dry reagent contained therein is dissolved so that the first reaction can take place. In a further step, a second liquid subset is filled into the arrangement of the reagent chambers, wherein the second subset corresponds to the volume of the second reagent chamber. This second subset of the liquid may be, for example, a buffer medium. The filling process takes place in that the additional second subset is first pressed by the centrifugal force in the first chamber and mixed with the existing fluid there and then flows into the second reagent chamber. By an appropriate control of the rotational speed and direction of rotation begins Mixing process in which the reagent in the second reagent chamber is dissolved and a second reaction takes place with the second reagent. Since both reagent chambers are completely filled when they are dissolved, good homogenization and thorough mixing in the different phases in each of the two chambers is achieved.
2. 2. The reagent chamber arrangement has the advantage that an optimized dissolution of a dry reagent takes place in the first chamber remote from the axis of rotation, in that this chamber is perfused twice in each case by the entire filling volume twice in the presence of two reagent chambers. First, a flow through the first reagent chamber takes place during filling of the chamber. The second flow occurs when the structure is emptied. In this way, a particularly good resolution of the dry reagents is achieved. This has the further advantage that even the agglomerates formed during the drying of reagents, which are pressed radially outwards into the first chamber by the centrifugal force, are "rinsed" with the fluid from the radially inner chambers during the subsequent emptying. Losses on the inner surface of the first reagent chamber are avoided.
3. 3. With the arrangement according to the invention can be realized in a simple way dilution series. Since the arrangement of the reagent chambers enables a very compact channel structure, a plurality of channel structures can be formed on a test carrier. In order to carry out a dilution series, only the first reagent chamber remote from the axis of rotation is filled with reagents in the parallel channel structures. To carry out a dilution series, the parallel structures are filled with different volumes, so that different dilutions can be produced in just one process step for a defined amount of reagent. The advantage of such a sequential microreactor cascade with a so-called bead-chain structure (series connection of several chambers) is that the complete reaction can be carried out with variable volumes, without changes in to make the geometry of the channel structure. In this case, the smallest volume of the sample liquid is as large as the volume of the first reagent chamber. The volumes to be examined are preferably a multiple of the preferably equal volumes of the individual reagent chambers.
4. 4. Another advantage of the reagent chamber structure is that the individual reagent chambers can be matched to the partial volumes to be examined. In the context of the invention, it was recognized in investigations of the dissolving and mixing behavior that, when the chambers are completely filled, the mixing processes take place in an optimized manner. If, for example, only a subset of the fluid is available in a first filling step, for example a dilution buffer which is filled up later with a sample liquid, homogenization with the first subset would be very poor in a "one-chamber system" Air pockets would be formed. In a reagent chamber arrangement with a plurality of reagent chambers, the chambers are each designed for the partial volume of the liquid to be examined and thus enable optimized dissolution and mixing, since the individual reagent chamber is completely filled by the liquid partial volume. Foaming of the solution is also prevented.

In order to further enhance the mixing operations in the reagent chamber assembly, in a preferred embodiment, the channel structure comprises a mixing chamber in which the reagent chambers and the connection channels are integrated between the reagent chambers. In this way, the properties of the individual reagent chambers are better combined with the properties of a fluidic single chamber. Preferably, the reagent chambers in the mixing chamber are arranged in series in the radial direction in such a way that the row of chambers encloses an angle of at most 80 ° to the radial direction, particularly preferably of a maximum of 60 °. Radial direction is to be understood as meaning a straight line that extends outward from the axis of rotation of the microfluidic element or of the test carrier. The Thus, reagent chambers need not be directly directed radially outward, but may include an angle to the radial direction that is different than 90 °.

The reagent chambers are designed to be filled with a liquid and to dissolve a solid dry reagent contained in the reagent chamber without the liquid flowing into the adjacent reagent chamber. As long as the amount of liquid does not exceed the volume of the reagent chamber, the liquid remains in the reagent chamber into which it flows. This is always the first time you fill the rotating axis remote reagent chamber. As a rule, therefore, it has the inlet opening, which is in fluid communication with the feed channel such that a liquid sample can flow into the rotation axis remote reagent chamber.

Preferably, the reagent chambers have a round configuration. Their base is circular. The bottom of the individual chambers is rounded, so that the floor merges steadily into the chamber walls, ie without an edge. The reagent chambers are preferably designed in the form of a hemisphere or a hemisphere segment. Between two adjacent chambers, a web is formed, which separates the two chambers. At the upper end of the chamber, an edge is provided so that a capillary stop is formed, which prevents leakage of liquid from one of the reagent chambers. This web-like barrier is referred to in professional circles as a plate. Of course, the edge in the transition does not have to be sharp-edged. It can also have a small radius. However, the radius should be chosen so small that the barrier function is maintained.

The reagent chambers, which are each connected to one another by at least two connecting channels, are preferably integrated in a mixing chamber. The mixing chamber consists of the reagent chambers, the connection channels, a feed opening through which liquid can enter from a feed channel into the mixing chamber, and a vent opening at the end a vent channel, which is in air exchange communication with the mixing chamber, is arranged. In addition, the mixing chamber may also comprise a transport channel which is guided laterally along the reagent chambers.

Reagent chambers having a rounded bottom or a rounded depression as a structure are also suitable for use in rotating test carriers and Zentrifugaldevices to introduce two or more reagents individually in the structure and to mix together only when dissolved with a liquid at a later date. This applies in particular to reagents which react with one another but may only be mixed at an analysis time (for example when dissolving with plasma), but not before. Only in the analysis should they dissolve together. The statements made in the figure description with respect to rotating test carrier can therefore be transferred to non-rotating test carrier in which the reagent chambers have a rounded bottom and preferably have a hemispherical shape.

Hemispherical reagent chambers, which are preferably combined in a mixing chamber, also have a great advantage in the introduction and drying of reagents. The reagents are introduced into the reagent chambers in liquid form and dried there. During the drying process, the surface tension acts, so that the metered liquid reagent wets the environment of the application point and spreads slowly. If it strikes edges or similar places, which have a higher capillarity, it dries concentrated there. The rounded bottom prevents such concentration. Since only one reagent is applied per reagent chamber, also a confluence and mixing is prevented. This is supported by the sharp-edged upper edges of the chambers. Even when the reagents are dissolved, the round bottom reagent chambers prove to be particularly advantageous.

Fig. 1

ein als Testträger ausgebildetes mikrofluidisches Element mit drei identischen Kanalstrukturen;

Fig. 2a, b, c

Schnittbilder durch eine Kanalstruktur aus Fig. 1;

Fig. 3

einen alternativen Testträger;

Fig. 4

eine Detailzeichnung einer Kanalstruktur mit drei Reagenzkammern;

Fig. 5

Detailzeichnungen einer Kanalstruktur mit drei Reagenzkammern beim Befüllen;

Fig. 6

eine Ausführungsform mit zwei Reagenzkammern;

Fig. 7

eine Ausführungsform mit drei Reagenzkammern;

Fig. 8

eine perspektivische Ansichten der Anordnung aus Fig. 7;

Fig. 9

eine Anordnung mit sechs Reagenzkammern;

Fig. 10a, b, c

eine Anordnung mit zwei Reagenzkammern beim Eintrocknen von flüssigen Reagenzien

The invention will be explained in more detail with reference to specific embodiments shown in the figures. For this purpose, the invention is described by way of example on a rotating test carrier. The features illustrated therein may be used alone or in combination to provide preferred embodiments of the invention, for example, a channel structure of a microfluidic element that does not rotate. To clarify details, the proportions of the individual components shown do not match in part. The described embodiments do not limit the invention defined by the claims in their generality. It shows:

Fig. 1

a trained as a test carrier microfluidic element with three identical channel structures;

Fig. 2a, b, c

Sectional images through a channel structure Fig. 1 ;

Fig. 3

an alternative test carrier;

Fig. 4

a detailed drawing of a channel structure with three reagent chambers;

Fig. 5

Detailed drawings of a channel structure with three reagent chambers during filling;

Fig. 6

an embodiment with two reagent chambers;

Fig. 7

an embodiment with three reagent chambers;

Fig. 8

a perspective views of the arrangement Fig. 7 ;

Fig. 9

an arrangement with six reagent chambers;

Fig. 10a, b, c

an arrangement with two reagent chambers during the drying of liquid reagents

FIG. 1 shows a microfluidic element 1 with three identically constructed channel structures 2, which extend substantially radially outward. Preferably, the smallest dimension of the channel structure 2 is at least 0.1 mm, more preferably at least 0.2 mm in size. The microfluidic element 1 is a test carrier 3, which is designed as a round disc and through which a rotation axis 4 extends centrally around which the disc-shaped test carrier 3 rotates. The channel structure 2 is formed by a substrate 5 and a Enclosed cover layer not shown, which covers the test carrier 3 from above.

The microfluidic element 1 is suitable for use in an analyzer or similar device having a support for receiving and rotating the microfluidic element. The device is preferably designed such that the microfluidic element is rotated about a rotary shaft of the device, wherein the axis of the rotary shaft is aligned with the axis of rotation 4 of the microfluidic element 1. For this purpose, the rotary shaft of the device can extend through a bore 4a of the test carrier 3. The axis of rotation 4 preferably extends through the center or the center of gravity of the element 1.

The channel structure 2 of the microfluidic element 1 includes a feed channel 6, which comprises a U-shaped channel section 7 and a straight channel section 8. At the end of the two U-legs of the U-shaped channel portion 7, a feed opening 9 is provided, through which a liquid sample, preferably, for example, a body fluid such as blood, can be entered into the feed channel 6. For example, a sample liquid can be metered by an operator manually (with a pipette) into a feed opening 9. Alternatively, the feed channel can also be equipped with a liquid by means of a dosing station of an analytical device. When dosing a liquid in the feed channel 6 is inserted into the liquid through one of the two feed openings 9, while the air contained in the channel can escape through the second supply port.

The channel structure 2 further comprises a vent channel 10 with a vent opening 11 and two reagent chambers 13, which are connected to each other via three connecting channels 14 so that a fluid exchange between the two reagent chambers 13 takes place. The channel structure 2 is in a preferred embodiment according to FIG. 1 formed as analysis function channel 15, which comprises a measuring chamber 16, a measuring channel 17 between the measuring chamber 16 and the reagent chambers 13 and a waste chamber 18, which is connected via a disposal channel 19 with the measuring chamber 16. The measuring chamber 16 is vented via its own venting channel. Trained as a reservoir 20 Waste chamber 18 has a vent passage 21 with an outlet valve at the end, can escape through the air from the channel structure 2.

In a preferred embodiment, such. In FIG. 1 shown, the channel structure 2 includes a mixing chamber 22, in which the two reagent chambers 13 and the three connecting channels 14 are integrated. The mixing chamber 22 has an inlet opening 23 which is in fluid communication with the feed channel 6, so that a liquid sample can flow into the rotation axis remote reagent chamber 13 a. The rotation axis remote reagent chamber 13a has a greater distance to the rotation axis 4 than the other reagent chamber 13b. The near-axis reagent chamber 13b (closer to the rotation axis 4 than the reagent chamber 13a) is in fluid contact with the vent passage 10 via an air outlet 33, so that air escapes from the reagent chamber assembly and the mixing chamber 22.

When a liquid is placed in the U-shaped channel section 7 and its test carrier 3 is then rotated about the rotation axis 4, the centrifugal force pushes the liquid through the straight channel section 8 of the feed channel 6 until the liquid reaches the mixing chamber 22 through the inlet opening 23. The liquid is then collected in the off-axis reagent chamber 13a until it has filled. In this case, a dry reagent dried in the reagent chamber 13a is dissolved. If further liquid is admitted into the mixing chamber 22, the liquid now flows through the three connecting channels 14 into the rotational axis-closer reagent chamber 13b, wherein the radially outermost connecting channel 14 is first filled with liquid. The air contained in the mixing chamber 22 escapes through an air inlet 33 in the vent passage 10 to the outside.

By suitable control of the rotational speed, the direction of rotation and the acceleration can be an optimized solubilization of the reagents in the Reagent chambers 13 take place, which is supported by the rounded reagent chambers 13.

FIG. 2a shows a section along the line IIA FIG. 1 through the two reagent chambers 13a, 13b. The reagent chambers 13a, 13b are preferably hemispherical in shape, wherein the open opening surface of the hemispheres 24 is closed by the cover layer. The reagent chambers 13 are rounded at their bottom so that no sharp edges occur. The rounded bottom of the chamber thus ensures a uniform distribution of both the reagent and a uniform solubilization and a uniform flow rate. The transitions to the connecting channels are preferably not rounded but sharp-edged, ie at the upper edge of the hemispheres 24 a sharp edge 25 is formed, wherein the edge 25 preferably includes an angle of 90 °. This creates a kind of geometric valve that provides overflow protection because the edge provides a physical barrier to the further transport of the liquid.

In order to bring the reagents into the chamber, the reagents present in liquid form are introduced into the open test carrier 3 without cover layer, for example by pipetting. The sharp edges then serve as boundaries that prevent creeping of the liquid reagents during drying. The structure thus becomes more independent of disturbing effects during automatic processing during drying. An overflow protection 26 adjoins the reagent chambers 13 at the upper edge, which prevents reagents from escaping from the mixing chamber 22. The surface enlargement by the overflow protection 26 can also have an elongating effect on the mixing time during mixing or dissolution of the dry reagents.

FIG. 2b shows the section through the channel structure 2 FIG. 2a However, with shown dry reagents 35 and cover layer 34. The reagent chambers 13 and the mixing chamber 22 is here designed so that the depth t of the overflow protection 26 is about one third of the depth T of the mixing channel 22. The Depth t of the overflow protection 26 is about 400 microns. Two-thirds of the depth T of the mixing channel 22 is formed by the reagent chambers 13. The dried reagent 35 covers the bottom and the inner surfaces of the hemispheres 24, wherein the filling height h of the dry reagent 35 at the bottom corresponds approximately to half the height H of the hemisphere 24. At the edges, the reagent 35 continues to flow up during the drying; However, it is prevented by the physical barrier and the edge 25 from crawling over the web 27 formed between the two chambers 13a, 13b. The web 27 preferably extends between two adjacent reagent chambers 13 in the direction of the cover layer 34 and thus separates the two reagent chambers 13a, 13b of the mixing chamber 22.

Figure 2c shows a three-dimensional view in the area of the line IIc FIG. 1 through the connecting channels 14 of the channel structure 2. The feed channel 6 has a backstop 28, which is designed as a microfluidic valve 29. The depth of the feed channel 6 from the surface 30 of the microfluidic element 1 is of the same order of magnitude as the depth of the connecting channels 14. However, it is significantly larger than the depth of the rotation axis remote reagent chamber 13a. The depth of the feed channel 6 is therefore also about 400 microns. A liquid flowing into the overflow protection 26 of the mixing chamber 22 by rotational force from the feed channel 6 flows via the edge 25 into the hemispherical reagent chamber 13a. By rotation of the test carrier 3, the liquid that has flowed in is moved in the reagent chamber 13a and thus dissolves the dry reagent (not shown here).

When another liquid flows in, it is also conducted through the connection channels 14a, 14b and 14c into the further reagent chambers 13 (not shown). In the context of the invention, it has been found that the transitions into the capillary connection channels 14a, 14b, 14c, which are formed by the hemisphere 24, are preferably not smaller than 0.4 × 0.4 mm in cross section (or their diameter is not smaller than 0.4 mm) and may later taper gradually. For connection channels 14 with a smaller cross section, the applied capillary force is so great that an overflow ("crosstalk"), in particular the liquid reagents before drying, is formed.

The channel structure 2 with bottomed reagent chambers 13 can also be used in non-rotating test carriers. A fluid driven by an (external) force first flows in a non-rotating microfluidic element 1 into the first reagent chamber 13a, fills it completely and dissolves the contained reagent. The rounded bottom of the chamber not only ensures even distribution of the reagent. The dissolution of the reagent is also optimized. Only the influx of additional (force-driven) liquid allows it to overcome the edge 25, so that it can flow through the connection channels 14 in the adjacent reagent chamber. Consequently, the reagent contained here is first dissolved in a second step.

FIG. 3 shows by way of example a further embodiment of a test carrier 3, with five identical channel structures 2. The feed channel 6 also has a U-shaped channel section 7 and a straight channel section 8. The mixing chamber 22 also has a venting channel 10 with a vent 11 at its end close to the axis of rotation. Also in this arrangement, the channel structure 2 is designed as an analysis function channel 15 and comprises a measuring chamber 16.

FIG. 4 shows a detailed drawing of the mixing chamber 22 from FIG. 3 with the three series-connected reagent chambers 13a, b, c and in each case two connecting channels 14, namely in each case a central connecting channel 14a and a lateral (near the axis of rotation) connecting channel 14b. The mixing chamber 22 preferably has a rotational axis-near inlet opening 23, through which liquid from the feed channel 6 enters the mixing chamber 22. A capillary transport channel 31 is preferably arranged on the long axis 36 of the mixing chamber 22 remote from the axis of rotation. The transport channel 31 extends laterally and radially outward on the series-arranged reagent chambers 13. Its depth (viewed from the surface 30 of the test carrier 3) is about 150 to 2000 microns less than the depth of the connecting channels. The incoming liquid is passed through the transport channel 31 into the reagent chamber 13a.

The venting channel 10 is wider than the feed channel 8 and as the connecting channels 14 between the reagent chambers 13. In this way, a smaller capillary force is generated by the venting channel 10, so that no liquid penetrates into the venting channel 10. In addition, the venting channel 10 is always arranged close to the axis of rotation so that the liquid can not pass from the reagent chambers 13 into the venting channel 10 during rotation. As soon as the reagent chamber 13a is filled, the air contained therein escapes through the connection channels 14a and 14b into the next reagent chamber 13c. As soon as the reagent chamber 13a is completely filled, liquid flows through the two connection channels 14a and 14b into the reagent chamber 13c. The filling of the second reagent chamber 13c thus initially also takes place at least partially through the connection channels 14a, 1-4b and through the transport channel 31.

The air contained in the second reagent chamber 13c escapes through the connection capillaries 14a and 14b which form the connection to the rotational axis-nominal reagent chamber 13b. In this way it is ensured that no air is trapped in the reagent chambers 13a, 13b and 13c. From the reagent chamber 13b, the air escapes through the vent passage 110. In this way, a preferred filling of the reagent chambers 13 from radially outside to radially inside is made possible.

The arrangement according to the invention allows the liquids to be mixed even when the reagents are being dissolved, in particular when the reagents in the second and further reagent chambers 13 are dissolved. The degree of solubilization is therefore particularly high and effective.

The filling of the reagent chambers 13a, b, c of the mixing chamber 22 is based on or FIGS. 5a to 5c explained in more detail. Entering the mixing chamber 22 Liquid is conducted past the capillary-active transport channel 31, which is adjacent to the inlet opening 23, past the two reagent chamber 13b, 13c near the axis of rotation and flows into the reagent chamber 13a remote from the axis of rotation (arrow direction F). The inflowing liquid is held by capillary action in the transport channel 31. During the rotation of the test carrier 3 (in the direction of arrow R, here in a clockwise direction), the liquid is then pressed at the end of the mixing chamber 22 remote from the axis of rotation into the reagent chamber 13a and dissolves the dry reagent contained therein. When Befüllern escapes air from the reagent chamber 13a via the connecting channels 14a, 14b and the chambers 13c, 13b and the vent passage 10. As further liquid nachfließt, this is passed through the transport channel 31 into the reagent chamber 13a and from there first at least partially through the central Connecting passage 14 a and the tangential connection channel 14 b led into the middle reagent chamber 13 c. The further filling takes place directly via the transport channel 31 until the reagent chamber 13c is filled. Upon further inflow of liquid from the feed channel 6, finally, the rotational axis near reagent chamber 13b is filled by the liquid first flows through the central and tangential connection channels 14a, b and also through the transport channel 31 and later directly into the chamber 13b. The air contained in the reagent chambers 13 finally escapes through the air outlet 33 and the venting channel 10.

In the example, according to the FIGS. 4 and 5 the reagent chambers 13 a single volume of 3 ul, so that the three reagent chambers together have a volume of about 9 ul. The volumes of the individual reagent chambers 13 are preferably between 3 μl and 10 μl. Reagent chambers with a volume of 2 μl or only 1 μl are also conceivable, as well as reagent chambers 13 with a volume of 20 μl, 50 μl, 100 μl or 500 μl.

FIG. 6 shows a further preferred embodiment with a mixing chamber 22, in which two reagent chambers 13a, 13b are integrated. Again, a capillary transport channel 31 is provided through which into the mixing chamber 22 entering liquid is guided to the rotation axis remote reagent chamber 13a, which is the two reagent chambers 13a, 13b the farthest from the axis of rotation reagent chamber. The rounded reagent chambers 13, with the rounded bottoms, which are preferably formed as a hemisphere 24, not only provide for a homogeneous reagent application of the still liquid reagent. They also prove to be extremely suitable when the test carrier 3 is operated in a shake mode in which the rotational speed and direction of rotation are changed according to a preferably sawtooth-shaped control curve. In this process, known as "Euler mixing", which guarantees good homogenization and dissolution of the dry reagents, mixing can be further increased by the rounded geometry. Within the scope of the invention it has been recognized that the most effective exchange and the most effective mixing takes place at the edges and walls of the reagent chambers 13. Preferably, therefore, in at least one of the two adjacent reagent chambers 13, the connecting channels 14 edge-layered, z. B. tangential to the reagent chambers 13, arranged. It has proven to be advantageous to form the connecting channels 14 without edge transitions to the reagent chambers 13.

Moreover, within the scope of the invention, it has been recognized that multiple reagent chambers with communication channels during "Euler mixing" transport the fluid through the communication channels 14 from chamber 13 to chamber 13 and, in combination with the rounded surfaces, provide a diffused exchange and mixing efficiency can.

Since the reagent chambers 13 are preferably arranged adjacent to one another such that their distance is smaller than the smallest dimension of the reagent chambers 13 in the test carrier plane, rapid fluid transport from one chamber 13 to the other is also possible. The smallest distance is defined in the context of the invention as the smallest distance between the reagent chambers 13 and between the Reagenzkammeraußenwänden. At least the centrally located connecting channel 14a between two reagent chambers 13 is therefore shorter than the smallest dimension of the reagent chambers 13. In the in Fig. 6 As shown, the central connecting channel 14a is about 0.2 mm long. Its width and depth are each 0.4 mm. The reagent chambers, 13 have a height of 1.4 mm. The diameter of the reagent chambers is 1.95 mm. By this geometric arrangement, a fluid transport between two adjacent reagent chambers 13 is possible without hindrance. Through the short connection channels 14, the fluid can be quickly transported from one chamber to another. The transport takes place directly without intervening valve structures, siphon arrangements or siphon-like channel structures whose length is a multiple of the reagent chambers. As a result, the process sequence with the reagent chambers according to the invention is very fast and saves time. In addition, a controlled and defined dissolution of different dry reagents contained in individual reagent chambers 13 can be carried out.

Due to the modular design with small reagent chambers 13, it is possible to provide test carrier 3, which are based on this principle arbitrarily expandable. So not only two or three, but also several chambers can be connected in series.

In addition to the round hemispherical reagent chambers, other forms of the reagent chambers are possible, for example, drop-shaped reagent chamber forms or when using two reagent chambers, which are integrated in a mixing chamber 22 z. B. so-called "yin-yang formations". Preferably, these reagent chambers are rounded at the bottom. Above all, oval and round chamber shapes prove advantageous.

FIG. 7 shows a star-shaped arrangement of three reagent chambers 13 in a mixing chamber 22. Also in this arrangement, the rotation axis remote mixing chamber 13a is filled via the transport channel 31 first. If further liquid flows in, then the two reagent chambers 13b, 13c closer to the axis of rotation are filled together. Between the reagent chambers 13a and 13b, only a central connection channel 14a is provided, since the capillary transport channel 31 as a second connection channel see, since the capillary transport channel 31 serves as a second connection channel 14b.

In the FIGS. 8a and 8b Three-dimensional views of such a star-shaped reagent chamber arrangement are shown. Clearly visible are the rounded connection channels 14 between the reagent chambers 13 and the rounded hemispherical reagent chambers 13 themselves. In this embodiment, it can be seen that the transport channel 31 also functions fluidically as a connection channel 14.

FIG. 9 shows that even a star-shaped or circular arrangement of reagent chambers 13 can be extended. Thus, as shown here, six reagent chambers 13 can be interconnected fluidically, whereby the principle is maintained that the rotor axis furthest reagent chamber 13a is filled first. A filling of the other chambers then starts from the rotation axis remote chamber 13 a, which is farthest from the axis of rotation 4.

During rotation of the test carrier, the fluid is moved through all the reagent chambers, in the star-shaped arrangement as well as in the row-shaped arrangement. In this way, a very efficient dissolving and mixing as well as a targeted control of the liquid quantities can be achieved. The very compact and small arrangement obtained has the advantage that a plurality of cascaded channel structures 2 can be arranged on a test carrier 3.

Based on FIGS. 10a to 10c the drying process of two reagents in a microfluidic element 1 is explained at different times, wherein in each figure both a top view and a section is shown.

Starting from two reagent chambers 13, which are separated from each other and in fluid communication with each other via connection channels 14, is the drying of the initially liquid reagents explained. The two reagent chambers 13a, 13b are integrated in a mixing chamber 22. Between the two reagent chambers 13a, 13b, a web 27 is arranged, so that the two chambers 13 are spatially spaced from each other. In the web 27, the connecting channels 14 are embedded. The embodiment shown here has three connection channels 14a, 14b and 14c, wherein the connection channel 14a is a central channel and the two further connection channels 14b and 14c are each arranged laterally.

FIG. 10a shows that a liquid reagent is introduced into the hemispherical reagent chambers 13a, 13b. For each reagent, a reagent chamber 13 is used, which is referred to as "pearl" due to their shape. Overall, therefore, a "pearl chain structure" is present in the mixing chamber 22. The reagent is in each case applied to the middle of the reagent chamber 13a, 13b. During the following drying process, the reagent wets the environment of the dosing point, forming a uniform film. Since the reagent chambers are free of edges or corners where the reagent might concentrate, a very even distribution occurs. When the liquid reagent reaches the connection channels 14, it enters it. However, due to the flow resistance of the connection channels 14, it is slowed down and does not flow until it has passed into the adjacent reagent chamber 13. If the liquid reagent reaches the upper edge of the reagent chamber 13, which forms the end to the surface of the microfluidic element 1, the reagent stops at the Edge and does not continue to flow. The resulting cross-sectional increase thus has a capillary stop effect.

The connecting channels 14 preferably have such a cross section that the liquid in the connecting channels 14 is braked and is not transported into the adjacent reagent chamber 13 due to capillary forces. Consequently, on the one hand, the cross-section must be large enough so that the resulting capillary forces are small enough so that the connection channels are not completely filled with the reagent and the reagents in the connection channels mix. On the other hand, the must Cross-section of the connecting channels should be small enough so that the flow resistance is sufficient to decelerate inflowing reagent in the connecting channels 14.

The proper choice of the cross section of the connection channels 14 not only affects the drying process when only capillary forces act. The cross sections also have an influence on the mixing efficiency and the exchange of liquids between two reagent chambers 13. In order to achieve sufficiently high flow velocities which allow a fluid exchange between the chambers 13, the cross section of the connection channels is at least 0.1 mm ² , preferably 0.4 x 0.4 mm ² large. Cross sections of less than 0.05 mm ² have proved to be unsuitable.

The hemispherical or bottom-rounded reagent chambers 13 show that when filled with a liquid reagent with a maximum volume of 70% of the chamber volume, a trouble-free drying of the reagents is possible. A mixing of two reagents in two adjacent chambers 13 is reliably prevented. The volume of the liquid reagent to be applied is preferably less than 60% of the chamber volume, particularly preferably less than 55%.

FIG. 10c shows the two reagent chambers 13, after the liquid reagent is spread. The connecting channels 14 are wetted with liquid only at their beginning. The largest distance of the respective connection channels 14 is free of liquid, so that a mixing of the two reagents is reliably prevented.

In the context of the invention, it has been found that the reagent chambers 13 with a rounded bottom, in particular if they are preferably integrated in a mixing chamber 22, are not only particularly suitable for drying two different reagents, but that such reagent chambers 13 are in non-rotating microfluidic Elements 1 can be used. For controlling the liquids and for dissolving the Reactants required force is generated by an external force. As an alternative to the centrifugal force or rotational force, pressure forces can be generated, which are caused for example by an external pump. Also, this force can be based on a hydrostatic pressure. The statements made in the context of this invention for rotating test carriers therefore also apply to non-rotating microfluidic elements. The basis of the FIGS. 2 to 9 corresponding features can also be used accordingly in non-rotating arrangements and channel structures.

Claims (15)

1. Microfluidic element for analysing a liquid sample
   having a substrate (5) and a channel structure (2) enclosed by the substrate (5) and a cover layer,
   wherein
   the microfluidic element (1) is rotatable around a rotational axis (4);
   the channel structure (2) includes a feed channel (6) having a feed opening (9), a ventilation channel (10) having a ventilation opening (11), and at least two reagent chambers (13);
   the reagent chambers (13) are connected to one another via two connection channels (14) in such a manner that a fluid exchange is possible between the reagent chambers (13),
   one of the reagent chambers (13) is a rolational-axis-distal reagent chamber (13a), which, of the two reagent chambers (13), is positioned furthest away from the rotational axis,
   the rotational-axis-distal reagent chamber (13a) contains a reagent (35), which reacts with the liquid sample,
   one of the reagent chambers (13) has an inlet opening (23), which is in fluid connection with the feed channel (6), so that by rotation of the microfluidic element the liquid sample inserted into the channel structure (2) is first channelled into the rotational-axis-distal reagent chamber (13a) so that this rotational-axis-distal reagent chamber (13a) is filled first and the reagent adsorbed in this rotational-axis-distal reagent chamber (13a) is dissolved.
2. Microfluidic element according to claim 1, characterised in that the microfluidic element (1) is a test carrier (3), through which the rotational axis (4) extends.
3. Microfluidic element according to claim 1 or 2, characterised in that the channel structure (2) is an analysis function channel (15), which comprises a measuring chamber (16).
4. Microfluidic element according to any one of the preceding claims, characterised in that the rotational-axis-distal reagent chamber (13a) has the inlet opening (23).
5. Microfluidic element according to any one of the preceding claims, characterised in that the channel structure (2) comprises a mixing chamber (22), in which the reagent chambers (13) and the connection channels (14) between the reagent chambers (13) are integrated.
6. Microfluidic element according to claim 5, characterised in that

   - the mixing chamber (22) has a rotational-axis-proximal inlet opening (23), and

   - a capillary transport channel (31) is implemented laterally and radially externally on the reagent chambers (13) in the mixing chamber (22), whose cross section is smaller than the cross section of the connection channels (14), so that liquid flows through the transport channel (31) from the rotational-axis-proximal inlet opening (23) to the rotational-axis-distal reagent chamber (13a), which is opposite to the inlet opening (23).
7. Microfluidic element according to claim 5 or 6, characterised in that webs (27) are implemented between two adjacent reagent chambers (13) in the mixing chamber (22), wherein the webs (27), by which the reagent chambers (13) in the mixing chamber (22) are separated, extend perpendicular to the cover layer (34).
8. Microfluidic element according to any one of the preceding claims, characterised in that the reagent chambers (13) are positioned in series in radial direction in such a manner that the series of the reagent chambers (13) encloses an angle of at most 80° to the radial direction.
9. Microfluidic element according to any one of the preceding claims, characterised in that the reagent chambers (13) are essentially hemispherical, the opening surface of the hemisphere (24) being terminated by the cover layer (34) of the microfluidic element (1).
10. Microfluidic element according to any one of the preceding claims, characterised in that the reagent chamber (13) adjacent to the rotational axis (4) has the inlet opening (23) and an air inlet (33), which connects the reagent chamber (13) to a ventilation channel (10).
11. Microfluidic element according to any one of the preceding claims, characterised in that one connection channel (14a) is positioned between two adjacent reagent chambers (13) in such a manner that it aligns with the centres of the two reagent chambers (13).
12. Microfluidic element according to claim 11, characterised in that the second connection channel (14b) is connected laterally to the two reagent chambers (13) in such a manner that it extends outside a central axis connecting the centres of two adjacent reagent chambers (13).
13. Microfluidic element according to any one of the preceding claims, characterised in that two adjacent reagent chambers (13) are positioned in such a manner that their spacing is less than the smallest dimension of the reagent chambers (13) in test carrier plane.
14. Microfluidic element according to any one of the preceding claims, characterised in that the reagent chambers (13) are implemented so that filling the reagent chamber (13) with a liquid and dissolving of a reagent (35) contained in the reagent chamber (13) occurs without liquid flowing into the adjacent reagent chamber (13).
15. Microfluidic element according to any one of the preceding claims, characterised in that the connection channel (14) has a cross section, in which the smallest cross-sectional dimension is at least 150 µm.

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