CN107427832B

CN107427832B - Fluid structure and micro-fluidic chip and system comprising same

Info

Publication number: CN107427832B
Application number: CN201680014413.2A
Authority: CN
Inventors: D·拉塔; T·舒克; M·巴斯勒; P·施庞; M·霍尔茨基; A·布赖特鲁克; R·贺默里奇
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2015-03-10
Filing date: 2016-03-10
Publication date: 2020-10-02
Anticipated expiration: 2036-03-10
Also published as: EP3268130A1; CN107427832A; WO2016142067A1; EP3268130B1; DE102015204235B4; DE102015204235A1

Abstract

The present invention relates to a fluidic structure for controlling one or more fluids. The fluid line (12, 32, 62, 82, 122) has a retaining section (20, 40, 70, 90) extending in the flow direction (13), in which the fluid line has a narrow region (24, 44, 74, 94, 134, 170) and a laterally adjoining broad region (26, 46, 76, 96, 136, 172), wherein the narrow region has a smaller side wall spacing h in at least one first direction perpendicular to the flow direction than the broad region_wSmaller sidewall spacing h_e. The invention also relates to a method for combining at least two liquid volumes, in which a first liquid (140) is conveyed by means of a fluid line into a narrow or wide region of a holding section, followed by a second liquid (150) which is separated from the first liquid beforehand by means of a buffer medium (146) being conveyed into the holding section, while the buffer medium is conveyed out of the holding section past the first liquid by means of the wide or narrow region.

Description

Fluid structure and micro-fluidic chip and system comprising same

Technical Field

The invention relates to a method for combining two liquid volumes and a fluidic, in particular microfluidic, structure for controlling one or more fluids according to the method, having a fluid line which defines a flow direction and a cross section perpendicular to the flow direction which is bounded on each side by a side wall. The invention also relates to a microfluidic Chip having a substrate, a cover for the substrate and such a fluidic structure in the substrate. Finally, the invention relates to a system consisting of a fluidic structure or microfluidic chip together with a first fluid and a second fluid, which are combined in the fluidic structure or microfluidic chip according to the method of the invention.

Background

Fluidic structures of this type, in particular microfluidic structures, are used for the treatment of partially very small amounts of liquid in the range of a few ml to in the μ l range. The fluid lines in such a structure have a lateral dimension in the range of a few mm or less. In such fluidic structures, the liquid is treated in the flow-through system, i.e. conveyed through the fluidic lines by generating a pressure difference (overpressure and/or underpressure). For this purpose, in addition to the microfluidic chip, technically very demanding control or operating devices are used, which are connected to the microfluidic chip or in which the microfluidic chip is inserted.

The applications for such fluid structures are varied. From document US 5972710 a, for example, a fluidic structure is known, which has a diffusion channel with a V-shaped profile, in which the sample and the detection liquid merge into parallel laminar flows in order to detect particles in the sample by means of a diffusion process.

Document US 2011/0100476a1 discloses a microfluidic structure with a valve formed by a meltable structure in a fluid channel. The meltable structure serves to permanently lock the fluid channel in the event of an external energy input.

In document DE 60007128T 2a valve for a microfluidic system is described, which comprises a fluid channel with an obstacle. The barrier is formed by a smart polymer that changes volume and thereby fluid flow through the channel upon external energy input.

Document US 2013/0167958a1 studies a microfluidic structure in a fluid logic circuit. The microfluidic structure comprises in particular a branch for controlling gas or liquid bubbles in the carrier medium.

A microfluidic valve for a fluid line is described in document US 2004/0195539a1, which is embodied in the form of a channel in a substrate and has a channel constriction at the location of the valve. The channel is closed with a self-adhesive cover film. The valve is open in the initial state and can be permanently closed in the region of the constriction by applying pressure to the film, which is self-adhesive. Furthermore, it is described how the valve can be opened again by deformation of the base material in the region of the channel constriction by means of a punch pressed in from the outside.

Document US 2012/0103103427a1 studies a microfluidic structure having a fluid channel formed with a wide section and a narrow section in succession in the flow direction. The two fluids flowing in parallel through the fluid channels are optionally concentrated, mixed or directed in separate paths in the structure.

Document US 2007/0286774a1 studies a microfluidic device with a fluid channel, which is constructed in a substrate and covered with a thin film. At least 2 sections are formed in the channel, into which the liquid flows due to capillary action. The two sections are spaced apart from each other so that the very thin flow is interrupted between them. By this construction, the very fine flow in the channel is better controlled overall.

A particular problem when handling fluids is the accumulation of liquid. For this purpose, fluid line arrangements are known which have at least two fluid supply lines and a discharge, which converge toward one another in the region of a T-shaped intersection. The difficulty here is to ensure that a limited volume of liquid column (also referred to as a "liquid plug") from the two feed lines also reaches the T-junction simultaneously for merging. This requires a large-scale fluid control, for example by means of complex valve switching and precise position monitoring of the liquid column, by means of which the delivery pressure and thus the position of the liquid column are controlled. The position monitoring is for example realized by means of a grating which measures exactly where the beginning and the end of the two liquid columns are present. Without such regulation, a gas cushion can be enclosed between the liquid columns, which keeps the liquid columns in the fluid line separated from each other at all times. In the case of a separation of the liquid columns due to air inclusions, for example, a thorough mixing of the liquids is prevented or the functionality of the sensor device is disturbed.

The basic goal is to limit the control or regulation to the minimum necessary. In particular, complicated precautions, such as movable valve parts, on the microfluidic chip should be avoided, since here too care should be taken to keep the production costs as low as possible.

Thus, document DE 102009048378B 3 describes another approach for combining two liquids. The microfluidic structure described therein comprises a fluid conduit which widens into a fluid chamber at a location transverse to the flow direction. The widening and the surface of the fluid chamber are obtained in that the volume of the first liquid guided through the fluid chamber is distributed over the entire cross-section of the fluid chamber. Furthermore, a further supply line opens into the holding position in the fluid chamber, which is designed in such a way that the second fluid volume supplied here is held in the region of the holding position until it is taken up by the first fluid volume passing through, and the two fluid volumes are discharged from the fluid chamber in a combined manner. This configuration provides an alternative passive fluid control with a defined fluid precondition (wetting behavior), which can dispense with complex valve switching and/or other active fluid controls.

A completely similar fluidic structure is known from the document "Droplet-based microfluidic sensing System for sampled fresh determination" (published in Sensors and Actuators B171-172(2012), p. 619-626) by D.Itoh et al. The microfluidic structures described herein include only one input line and one output line for handling two or more separately delivered liquid slugs (plugs). The liquid columns (plugs) are likewise fed via feed lines and separated from one another by gas bubbles to laterally widened fluid chambers, the volume of which is in any case greater than the volume of the first liquid column reached. The fluid chamber is configured such that the fluid wets only one of the oppositely disposed side wall portions. Thereby releasing a bypass through which gas from the gas buffer between the liquid columns may escape. Thus, under the effect of the continued delivery pressure, the second liquid column catches up with the first liquid continuing to adhere to the side wall portion and is output from the fluid chamber in a merged manner therewith. However, another condition required for this is that the total volume of the two liquids is sufficient to wet both wall portions of the widened merging chamber.

The two last-mentioned fluid structures do not require complex valve switching and fluid control and are therefore simpler in design, but they have the disadvantage that they do not guarantee a process-reliable process in all cases, in particular for wetting liquids and liquids with high surface tension, since liquids tend to pull forward or backward into narrow fluid lines due to capillary forces.

Disclosure of Invention

It is therefore an object of the present invention to provide a simple fluidic structure which is suitable for a process-reliable combination of fluids which are conveyed at a distance from one another by a buffer medium and which optionally wet the side walls of the fluid lines more or less strongly than the buffer medium.

This object is achieved by a method having the features of claim 1, a fluidic structure having the features of claim 3, a microfluidic chip having the features of claim 16 and a system having the features of claim 21.

According to the invention, the fluid line of the fluid structure mentioned at the beginning has a holding section which extends in the flow direction and is free of further supply lines and discharge lines, the fluid line having a narrow region and a wide region adjoining in the flow direction in the holding section, the narrow region having a smaller side wall spacing h in at least one first direction (first transverse direction) perpendicular to the flow direction than the wide region_wSmaller sidewall spacing h_e。

Accordingly, the object is also achieved by a microfluidic chip of the type mentioned at the outset, in which the fluid lines are formed in the substrate in the form of channels and are closed by a cover, wherein the channels in the holding section are divided into narrow and wide regions. Particularly preferably, the wide regions have a greater channel depth than the narrow regions. This embodiment can be produced particularly simply and therefore cost-effectively. Furthermore, it is preferred that the first transverse direction is perpendicular to the channel bottom opposite the cover, i.e. the side wall spacing h of the narrow region_eDetermined by the channel depth.

The holding section is therefore usually divided in the longitudinal direction into two adjacent and fluidically connected regions transverse to the flow direction (transverse direction), wherein one region is narrower in at least one spatial direction perpendicular to the flow direction (i.e. the first transverse direction) than the other region in the spatial direction. This arrangement ensures that the first liquid, which wets the side walls of the fluid lines more weakly or strongly than the buffer medium surrounding the liquid and reaches the holding section, is reliably fixed in both cases due to capillary forces. The term "in the transverse direction" is also used herein to describe "transverse to the flow direction" or "perpendicular to the flow direction". The statement "in the flow direction" is also to be interpreted as "in the longitudinal direction" or "in the longitudinal direction".

The holding section has only one inlet line and one outlet line in the form of the fluid line itself as sections of the fluid line. The two or more liquid columns are fed separately by one or more buffer media through the same feed line successively to the holding section and, after being combined in the holding section, are removed together from the holding section through the same discharge line.

Correspondingly, exactly like the fluid chamber in the above-mentioned document, the second condition is that the holding area is sufficient to completely accommodate the desired volume V of the first fluid reaching there_Fl1. In other words, a volume V of the first fluid is required_Fl1Less than the volume of the holding area. Alternatively, what is referred to as a "holding area" is simply a narrow area of the holding sectionOr broad area, depending on where the fluid stays based on its wetting characteristics. Thus, the volume of the holding region may be the volume V of the narrow region of the holding section_eIf the first fluid wets the side walls of the fluid line more strongly than the surrounding buffer medium. What must be applied at this time is: v_Fl1<V_e. The volume of the holding area can also be the volume V of the wide area of the holding section_wIf the first fluid wets the side walls of the fluid line more weakly than the surrounding buffer medium. Therefore, it must be applied that: v_Fl1<V_w. Only in this condition, the first fluid releases the beginning and the end of the laterally adjoining regions of the holding section, so that a bypass line for the buffer medium enclosed between the first fluid and the immediately following second fluid is released therethrough.

The third condition is again completely similar to the known solutions: expected total volume V of two or more combined liquids_Fl1+V_Fl2It is sufficient to close the ends of the retaining section with liquid. In other words, a combined liquid V is required_Fl1+V_Fl2Is greater than the volume of the holding area. In the case of a more wetting liquid, i.e. the volume V of the narrow region of the retaining section_e：V_Fl1+V_Fl2>V_e. In the case of less wetting liquids, i.e. the volume V of the broad area of the retaining section_w：V_Fl1+V_Fl2>V_w. Volume "V_Fl2"here correspondingly denotes the volume of the second liquid or of the further second liquids. In this way, two, three or other liquids separated by the buffer medium can be combined in the holding region, and the combined liquid volume can then be automatically discharged from the holding region of the fluid line under the effect of the continuous delivery pressure.

These conditions are reflected in the method according to the invention for combining two liquid volumes. The method provides that, in a fluidic structure having fluid lines, the fluid lines define a flow direction and a cross-section perpendicular to the flow direction that is bounded on each side by a side wall and have a cross-section extending in the flow direction without further supply lines and discharge linesIn which the fluid line comprises a volume V_eAnd a volume V adjoining transversely with respect to the flow direction_wWherein the narrow region has a smaller sidewall spacing h in at least one first direction perpendicular to the flow direction than the wide region_wSmaller sidewall spacing h_eOptionally, depending on the wetting properties, in step a) will have a volume V_Fl1Is conveyed into the holding section by the fluid line and is conveyed into the narrow region by capillary forces, and then in step b) at least one liquid which has been separated from the first liquid by a buffer medium and has a volume V is conveyed into the narrow region_Fl2Is fed into the holding section by the same fluid line, while the buffer medium is fed out of the holding section by the first liquid by-passing the wide area until at least one second liquid reaches the first liquid and both/all liquids are fed out of the holding section in a combined manner, wherein the conditions apply: v_Fl1<V_eAnd V is_Fl1+V_Fl2>V_e(ii) a Or in step c), will have a volume V_Fl1Is transported by means of a fluid line to a holding section and is transported in this case to a wide area due to capillary forces, and then in step d) at least one first liquid is separated from the first liquid by a buffer medium and has a volume V_Fl2Is fed into the holding section via the same fluid line, while the buffer medium is fed out of the holding section via the first liquid by-passing the narrow region until at least one second liquid reaches the first liquid and both/all liquids are fed out of the holding section in a combined manner, wherein the conditions apply: v_Fl1<V_wAnd V is_Fl1+V_Fl2>V_w。

Similarly, these conditions are also reflected in a system according to the invention comprising a fluidic structure or microfluidic chip of the type described above, having a defined volume V_Fl1Of a first liquid having a defined volume V_Fl2And a buffer medium arranged at the inlet of the holding areaBetween the first liquid and the second liquid and transportable therewith through the fluid line, wherein optionally the first liquid and the second liquid wets the side walls of the fluidic structure more strongly than the buffer medium, and wherein applicable conditions are: v_Fl1<V_eAnd V is_Fl1+V_Fl2>V_eOr wherein the first liquid and the second liquid wet the side walls of the fluidic structure more weakly than the buffer medium, and wherein the applicable conditions are: v_Fl1<V_wAnd V is_Fl1+V_Fl2>V_w。

By "the liquid is a more wetting liquid" is meant that the surface of the liquid forms a contact angle with the surface of the channel of <90 °, preferably <75 °, and particularly preferably <45 °. Conversely, if the contact angle formed by the surface of the liquid with the surface of the channel is >90 °, preferably >105 ° and particularly preferably >105 °

>135 deg., the liquid is referred to as a less wetting liquid. What is referred to as the "liquid surface" is the interface of the first liquid and the second liquid with the adjoining buffer medium. In the case of an interface with a gaseous buffer medium, the first and second liquids, which are wetting or non-wetting, are illustrated in a simplified manner. Generally, what is referred to as a buffer medium is a medium that is insoluble in the first liquid and the second liquid. The medium may likewise be a gas (e.g., air) or a liquid (e.g., an oil-based liquid, if the first and second liquids are present in an aqueous base, or vice versa, if the first and second liquids are based on an oil base, an aqueous base liquid).

As an application example, mention may be made of a reaction mixture for molecular biological reactions in which nucleic acids as a first liquid and enzymes as a second liquid are fed to a fluidic structure according to the invention in a liquid volume containing water and are combined therein according to the above-described method in order to effect the reaction. As possible buffer media, mineral oils, silicone oils, fluorinated oils or organic polymers (for example "Novec 7500" (hydrofluoroethers (C7F150C2H5)) are considered.

Preferably, a transverse transition in the form of a shoulder extending in the flow direction between the narrow region and the wide region is configured.

One or more such shoulders may project from the side walls of one or more restrictive fluid conduits. The narrow region is preferably formed between a plateau of the shoulder and the opposite side wall section, wherein the first transverse direction is perpendicular to the plateau. The shoulder may have a sharp or rounded or chamfered edge.

A preferred embodiment of the invention provides that the fluid line has an inlet section (Einlassabschnitt) upstream of the holding section in the flow direction and a discharge section (ausslassabscnittt) downstream of the holding section in the flow direction, wherein the inlet section and the discharge section in the first transverse direction merge steplessly into a narrow region of the holding section or into a wide region of the holding section.

In microfluidic chips, for example, the channel bottoms in the inlet and outlet sections transition steplessly to narrow-area channel bottoms or wide-area channel bottoms. The channel bottom of the narrow region here preferably forms the plateau described above.

"steplessly" includes on the one hand a transition from the entry section to the narrow or wide region of the holding section and from there to the discharge section without a change in cross section in the first transverse direction. In one embodiment, this is achieved, for example, in that the inlet section and the outlet section each have a side wall spacing h in a first direction perpendicular to the flow direction_inAnd h_outEqual to the minimum sidewall spacing h of the narrow region_e。

In this case, the dimension of the fluid line in the first lateral direction does not change when flowing through the narrow region in the holding section. In this embodiment, the broad region of the retaining section forms a widening of the cross section of the fluid line in the first transverse direction.

"steplessly" on the other hand also includes stable transitions between individual sections. In this context, "stable (continuous)" means a continuous, non-abrupt change in the cross section. Thus, in an alternative embodiment, the entry section has a sidewall spacing h in the first transverse direction_in>h_eWherein the fluid line has a first transition section downstream of the entry section and upstream of the holding section in the flow direction, in which a transverse sidewall spacing follows h in the flow direction_inSteadily decrease to h_e。

Similarly, the discharge section has a sidewall spacing h in the first transverse direction_out>h_eWherein the fluid line has a second transition section downstream of the holding section and upstream of the discharge section in the flow direction, in which a transverse sidewall spacing follows h in the flow direction_eSteadily widen to h_out。

In this embodiment, the passage cross section of the fluid line in the first transverse direction is reduced on the inlet side toward the retaining section to the side wall spacing of the narrow region and is widened again on the outlet side in a corresponding manner. The narrow region thus forms a constriction of the pipe cross section.

In order to prevent the flow velocity of the liquid from rising sharply due to a constriction of the line cross section, an advantageous embodiment of the invention provides that the fluid line in the holding section widens laterally in a second direction (second transverse direction) perpendicular to the flow direction relative to the inlet section and the outlet section. A second advantage of the widening is that larger liquid volumes can be processed without significantly increasing the space requirement of the structures on the microfluidic chip. In contrast, a correspondingly elongated channel itself requires more space when bent.

The fluid line may in particular widen in the second transverse direction on one side of the narrow region, on one side of the wide region or on both sides.

It is particularly advantageous if the broad regions are arranged offset in a second direction perpendicular to the flow direction with respect to the inlet section and/or the outlet section.

This design has the advantage that the flow of the fluid is not deflected as much or at all through the narrow region in the holding section, so that the risk of turbulence is reduced.

A further advantageous embodiment of the invention provides that the fluid line has at least one stop upstream and/or downstream of the holding section in the flow direction.

The at least one stop structure is preferably configured in the form of a shoulder which interrupts the course of at least one of the side walls of the fluid line.

In this sense, the shoulder forms, for example, one or more hollow shapes in at least one side wall of the fluid line, or one or more protrusions along at least one side wall of the fluid line, or both. The hollow shape can be formed, for example, by channels or recesses which issue laterally. The plurality of protrusions may for example form a comb-like structure. In all cases it is important that the stop structure cannot be passed over merely by the capillary force. The stop structure prevents the first liquid from exceeding the end of the holding section after flowing into the holding section or being pulled into the entry section due to capillary forces. The stop structure in this way supports the holding function of the narrow region and makes the flow process more reliable when polymerizing the two liquids.

Drawings

Further advantages of the invention are explained below with the aid of the figures. Wherein:

FIGS. 1a-1c show a first embodiment of the invention in three views;

2a-2c show a second embodiment of the invention in three views;

3a-3c show a third embodiment of the invention in three views;

4a-4e show a fourth embodiment of the invention in five views;

5a-5c show three snapshots of fluid flowing into a holding section of the fluidic structure according to FIG. 1;

fig. 6 shows a fifth embodiment of the invention, in which the stop structure upstream of the holding section is designed in an alternative manner;

fig. 7 shows a sixth embodiment of the invention, in which the shoulder between the narrow region and the wide region of the retaining section is designed in an alternative manner;

fig. 8 shows a seventh embodiment of the invention, in which the shoulder between the narrow region and the wide region of the retaining section is designed in an alternative manner;

9a-9c show an eighth embodiment of the invention in three views;

FIGS. 10a-10c show a ninth embodiment of the invention in three views, and

fig. 11a-11c show three snapshots of fluid flowing into the holding section of the fluidic structure according to fig. 9.

Detailed Description

Fig. 1a shows a plan view of a first embodiment of the invention. Fig. 1b shows a longitudinal section and fig. 1c correspondingly shows a cross section at the position marked in fig. 1 a. A substrate 10 of a microfluidic chip is shown, schematically and very schematically simplified, in which only one fluid line 12 in the form of a channel is constructed. A fluid, not shown, flows through the fluid line 12 under pressure in the direction indicated by the arrow 13, which is also referred to as the flow direction or longitudinal direction. The fluid line or channel has a cross section which is delimited on each side transversely to the flow direction by a side wall. The cross section is defined in a first direction perpendicular to the flow direction by a channel bottom 14 and a cover, not shown, at a position 16 opposite the channel bottom.

In practice, microfluidic chips typically have a plurality of fluid conduits as well as functional elements, such as reaction chambers, mixing structures, valves, etc. Furthermore, the channels are closed at their open upper side by means of a film (just covering) laminated onto the substrate. In fig. 1a to 1c, the illustration of the cover is omitted for the sake of simplicity.

The channel 14 is functionally divided in the flow direction into an entry section 18, a downstream holding section 20 and a further downstream discharge section 22.

The retaining section 20 is in turn divided laterally (i.e. transversely to the flow direction) into a narrow region 24 and a wide region 26 laterally adjoining it.

The fluid line has a side wall spacing h in the first transverse direction in the narrow region 24 between the channel bottom 14 and the cover (position 16)_eWhich in this case is determined by the channel depth. Of the expanse 26Sidewall spacing through h_wTo represent and in the example shown extend in another transverse direction. As can be seen in the cross-sectional illustration of fig. 1c, the spacing h_eLess than the minimum sidewall spacing h of the expanse_w. This condition is only critical for this: the wetting liquid (better than the surrounding buffer medium) flowing into the holding section 20 is held due to capillary forces in the narrow region 24, or the less than the surrounding buffer medium or non-wetting liquid flowing into the holding section 20 is held in the wide region 26. It is in principle not critical whether the sidewall spacings in the same or different directions are equal to one another. It is also not important whether the narrow region is wider or narrower than the minimum sidewall spacing h of the wide region in the second lateral direction_w。

H is shown here_eCoinciding with the channel depth, it is suitable for the channel depth in the expanse (which is greater than or equal to the minimum side wall spacing h)_w) And must also be greater than the channel depth in the narrow region.

In the cross-sectional representation in fig. 1b, it can also be seen that the inlet section has a side wall spacing h in the first transverse direction_inAnd the discharge section 22 has a sidewall spacing h_outAnd h is_inAnd h_outAnd a sidewall spacing h in a narrow region of the holding section 20_eAs large. The inlet section 18 and the outlet section 22 thus merge steplessly into the narrow region 24 in the first transverse direction. In other words, the channel bottom 14 in the intake section and the discharge section and in the narrow region 24 of the holding section 20 continues flat.

While the broad area 26 is recessed from the channel bottom 14. The total depth of the broad area 26 is even greater than its width, which in this example defines the minimum sidewall spacing h_w. Due to the recess, a transverse transition in the form of a shoulder 28 extending in the flow direction is formed between the narrow region 24 and the wide region 26. The shoulder 28 again has a sharp edge 29 in this embodiment. The sharp edge in principle provides greater process reliability, since greater energy must be used for this purposeThe liquid flows over the edge. For this purpose, the contact angle hysteresis is responsible, which causes the contact line formed by the interface and the side walls to stay at the edges and bends. On the other hand, for reasons of manufacturing technology, there are no sharp edges at all and functional requirements are also not necessary. In this sense, the term "edge" is also intended to encompass rounded or chamfered edges.

Fig. 2a to 2c show a schematic, greatly simplified second embodiment of a fluidic structure according to the invention. Once again, a fluid line 32 in the form of a channel is formed in the substrate 30 of the microfluidic chip, which fluid line is closed in a first transverse direction by a channel bottom 34, 34' and on its upper side 36 by a cover or membrane, not shown.

Unlike the exemplary embodiment according to fig. 1, the fluid line 32 has, in the flow direction, an inlet section 38, a first transition section 39, a holding section 40, a second transition section 41 and a downstream discharge section 42 in succession. The retaining section 40 is in turn divided laterally into a narrow region 44 and a wide region 46 laterally adjoining it. Here, too, the wide section 46 is recessed starting from the level of the channel bottom 34 in the narrow section 44, so that a transverse transition in the form of a shoulder 48 with a sharp edge 49 extending in the flow direction is formed between the narrow region 44 and the wide region 46.

In the longitudinal section of fig. 2b, it can be seen that the side wall spacing h between the channel bottom 34' and the upper side 36 in the entry section_inIs greater than the side wall spacing h in the narrow region 44 of the retaining section 40_e. This can be attributed to the level difference of the channel bottom, which is bridged in the transition section 39 by the ramp-like channel bottom 35. In other words, the side wall spacing is thus from h in the flow direction 13_inSteadily tapering to h_e。

Similarly, the sidewall spacing h of the discharge section 42_outGreater than the sidewall spacing h of the narrow region_eThe second transition section 41, which has a ramp-like channel bottom 35', also serves to compensate for level differences, i.e., also serves to adjust the lateral wall spacing in the flow direction in the second transition section41 from h_eSteadily expand to h_out. In this example, therefore, the inlet section 38 and the outlet section 42 also merge in the flow direction without a shoulder into the narrow region 44 of the retaining section 40.

From the point of view of the flowing fluid, the narrow region 44 therefore forms a pronounced cross-sectional constriction starting from the cross section of the entry section 38, which leads to an increase in the flow velocity with constant volume delivery.

To avoid this, the fluidic structure may be modified as shown in fig. 3a to 3 c. As before, this embodiment includes a microfluidic chip having a substrate 60 in which fluid conduits 62 in the form of channels are machined. The fluid flowing in the flow direction 13 first flows through the inlet section 68 again, then through the first transition section 69, then through the holding section 70, then through the second transition section 71 and finally through the downstream discharge section 72. The retaining section 70 is in turn divided in the transverse direction with a sidewall spacing h in the first transverse direction_eAnd a sidewall spacing h in the longitudinal direction of the narrow region 74 with a minimum_wAdjacent to the wide area 76. Also suitable here are h_e<h_w. Furthermore, as in the exemplary embodiment of fig. 2, here too the side wall spacing h in the entry section 68_inAnd a sidewall spacing h in the discharge section 72_outIs greater than the side wall spacing h in the narrow region 74 of the retaining section 70_e. Accordingly, the first transition section 69 and the second transition section 71 are each provided with a ramp-like channel bottom 65, 65', which form a shoulder-free transition.

In contrast to the exemplary embodiment according to fig. 2, in the exemplary embodiment according to fig. 3, the fluid line 62 in the holding section 70 widens in a second direction perpendicular to the flow direction 13 relative to the inlet section 68 and in a transverse direction relative to the outlet section 72. The lateral widening is symmetrical to the central axis of the fluid conduit 64, while the broad area 76 is located at the edge of the fluid conduit 62 in the second lateral direction as in the previous two examples. Thus, in other words, the fluid conduit 62 widens in the second transverse direction on the side of the narrow area and on the side of the wide area.

The transverse widening first of all facilitates the narrow region 74 in such a way that it is wider in the second direction than the inlet section and the outlet section. Thus, since in the first transverse direction from h_inTaper to h_eCan be partially compensated for and the flow velocity can be reduced in the narrow region 74 with constant volume flow.

At the same time, the broad area 76 is arranged offset in the second transverse direction with respect to the entry section 68 and with respect to the exit section 72. The width of the broad area is selected such that its position is in the bulge formed by the widening. Thus, a transverse transition or shoulder 78 extending in the flow direction 13 between the narrow region 74 and the wide region 76 is flush with a lateral wall 79 of the fluid line 62 in the inlet section 68 and the outlet section 72. This causes the flow of fluid to be directed less overall through the narrow region 74 in the retaining section 70. The risk of eddy currents is thereby significantly reduced by the design of the widening.

Fig. 4 shows a further developed embodiment of the fluidic structure. In the substrate 80 of the microfluidic chip, a fluid line 82 in the form of a channel is formed as before. The fluid line 82 has an inlet section 88, a first transition section 89, a holding section 90, a second transition section 91 and a downstream discharge section 92, which follow one another in the flow direction 13. The retaining section 90 is in turn divided laterally into a narrow region 94 and a wide region 96 laterally adjoining it. The wide region 96 is also recessed starting from the level of the channel bottom 84 in the narrow region 94, so that a transverse transition in the form of a shoulder 98 extending in the flow direction 13 and having a sharp edge 99 is formed between the narrow region 94 and the wide region 96. Although as before, the associated sidewall spacing h of the narrow region 94_eDetermined by the channel depth. But unlike before, the minimum sidewall spacing h in the expanse 96_wCoincides with the first transverse direction. In other words, the minimum sidewall spacing h in the broad area 96_wBut also by the channel depth here. Herein, according to the present inventionThe following are also applicable: h is_e<h_w。

The transverse expansion of the fluid line in the transition section and in the holding section, as before, serves to compensate at least partially for the transverse reduction in the line cross section in the constriction region and thus to reduce the flow velocity in this case. In this embodiment, too, the wide region 96 is positioned in such a way that the shoulder 98 forming the transverse transition to the narrow region 94 is flush with the side walls 100 of the inlet and outlet sections.

Unlike the embodiment according to fig. 3, the

walls

101, 102 in the first transition section 89, the holding section 90 and the second transition section 91 have a rounded or "continuously differentiable" contour. This facilitates flow and more prevents the formation of vortices at the section transitions. Furthermore, this continuous profile minimizes the retention forces acting on the line of contact between the interfaces between the surfaces of the liquid, gas and channel (solid), as described above with reference to the sharp edge 29 in fig. 1. At the transition mentioned here, it is desirable that the sidewall contact does not have an increased effort to release the bypass compared to the edge 29 discussed above. Thus, a "round" or "smooth" or "continuously differentiable" profile is advantageous here.

Also in this embodiment, the wider area is not as complex as before. It has approximately the shape of a cane, wherein the "handle" is at the end of the discharge side of the holding section, which end points away from the narrow region 94. Thus, the end of the expanse 96 forms a dead end 104. This has proven to be very advantageous if the liquid inadvertently enters a wide area. The air cushion locked at the end 104 is now prevented, i.e. the liquid can completely wet a wide area. Thus, there always remains an interface here which ensures a starting point for the liquid tear and thus a complete emptying of the wide area.

Finally, in this embodiment, two

stop structures

105, 106 are present upstream of the holding section 90 in the opposing

walls

101 and 102 of the fluid line 82. The

stop structures

105, 106 are designed as hollow shapes in the two

walls

101, 102, to be precise as dead-end channels, and interrupt the course of the walls, so that the fluid flowing in the narrow region 94 of the holding section 90 does not flow back into the intake section 98 due to capillary forces.

Fig. 5a to 5c show a sequence of flows to a liquid in the fluidic structure according to fig. 1. All three snapshots show the same section of a microfluidic chip 110, schematically shown very schematically and in simplified form, having a substrate 120 in which fluid lines 122 in the form of channels are machined. Here, a cover 125 in the form of a film is also shown, which closes the channel which is open on one side in the transverse direction.

The fluid line 122 is shown in section in the region of a retaining section, in which it comprises a narrow region 134 with a smaller channel depth and laterally adjoining wide regions 136 with a greater channel depth. The first fluid 140 flowing in direction 13 has a leading edge or boundary surface 142, which is also located in the entry section at the time according to fig. 5 a.

In fig. 5b, the first fluid 140 has traveled further, so that the rear interface 144 of the first fluid in the entry section is already visible. The first fluid 140 forms a so-called fluid column. The front interface has reached the holding section of the fluid conduit and due to capillary forces entered the flat area 134, while it has not yet wetted the broad area 136.

After the liquid column there is a buffer medium 146, which spatially separates the first fluid 140 from a subsequent second fluid 150, which is present in the inlet section in fig. 5 c. By continuing the two fluid columns, at some point the rear interface 144 of the first liquid column 140 also reaches the beginning of the holding section's wide area 136. Here, the rear interface 144 of the first liquid column 140 is disengaged from the wall of the fluid passage 122 where the broad area 136 is located. The wide area 136 then releases a bypass line, through which the buffer medium 146, gases or liquids that are not soluble in the first fluid and the second fluid, can escape, as symbolically represented by the arrow 152. The first fluid column 140 is now stopped in the holding area because it no longer senses the delivery pressure. Thus, the subsequent liquid column 150 may continue to be conveyed in the direction of the first liquid column 140 until the two liquid columns merge. Then, both are continuously conveyed together. This can be arranged such that the combined liquid column completely surrounds the gas cushion in the bypass line, or it first empties the bypass line and only then leaves the holding region completely. In this regard, the process depends on the details of the construction of the transition section.

The system referred to in fig. 5 therefore has: fluidic structure or microfluidic chip in which a narrow region 134 has a volume V_e(ii) a A first liquid 140 having a defined volume V_Fl1(ii) a A second liquid 150 having a defined volume V_Fl2(ii) a And a buffer medium 146 arranged between the first liquid and the second liquid at the entrance of the holding area and transportable together with the first liquid and the second liquid through the fluid line 122, wherein the first and

second liquids

140, 150 wet the side walls of the fluidic structure more strongly than the buffer medium 146, and wherein the applicable conditions are: v_Fl1<V_eAnd V_Fl1+V_Fl2>V_e. If the

fluids

140 and 150 are water-based and the sidewalls of the fluid lines are hydrophilic, the buffer medium 146 may be, for example, a gas or an oil.

Fig. 6 shows an alternative embodiment of a fluidic structure, which corresponds to the embodiment of fig. 1 and 5 with regard to the shape of the fluid line 158. The only difference is the stop structure 160 having a plurality of protrusions 162 along the side wall, and more specifically along the channel bottom 163 of the fluid line. The protrusions 162 together form a comb-like structure at the end of the narrow region 164. This arrangement prevents the wetting liquid from flowing through in total and thus prevents, in particular, the liquid from inadvertently flowing back out of the narrow region of the holding section into the discharge section of the fluid line.

Fig. 7 shows a simplified microfluidic chip 170 in which the fluid lines 172 are designed in an alternative manner, more specifically shoulders 178 extending in the flow direction which form a transverse transition between a narrow region 174 and a wide region 176. As in the example according to fig. 4, the side wall spacing h of the narrow region 174_eAnd minimum sidewall spacing h of wide area 176_wThrough the corresponding channel depthAnd (5) determining the degree. However, the shoulder 178 does not have a sharp edge, but rather a rounded edge 180, unlike all of the embodiments shown above. In addition, the shoulder 178 also merges into a channel bottom 182 of the wide region 176 in the form of a radius 184. Thus, the transition has a curvilinear cross-section, without abrupt or kinks, with the effect that the sidewall spacing increases in a continuously differentiable manner from the narrow region 174 in the lateral direction toward the wide region 176.

Fig. 8 shows a simplified microfluidic chip 90, in which the fluid lines 192, that is to say the shoulders extending in the flow direction, which form the transverse transitions between the narrow regions 194 and the wide regions 196, are again designed in an alternative manner. As in the example according to fig. 7, the side wall spacing h of the narrow region 194_eAnd minimum sidewall spacing h of wide region 196_wAgain determined by the respective channel depth, and the shoulder has a rounded edge and a rounding in the transition from the channel bottom 202 of the broad area 196 to the shoulder 198. Unlike the previous example or the example according to fig. 1, the broad areas 196 are not recessed starting from the channel bottom 203 in the narrow areas 196. Instead, the retaining section is formed in such a way that the narrow region 194 forms a high point or plateau starting from the channel bottom 202. This shape is similar to the embodiment according to fig. 2 to 4. In contrast, however, the channel floor 202 continues from the inlet section 208 through the first transition section 209, the wide region 196 of the retaining section 210, the second transition section 211 toward the outlet section 212 at the same level without transition. In other words, the

transition sections

209, 211 do not extend over the entire channel width.

Fig. 9a shows a view of a further embodiment of the invention in a manner similar to fig. 1 a. Fig. 9b accordingly shows a longitudinal section, and fig. 9c accordingly shows a transverse section at the position indicated in fig. 9 a. A substrate 310 of a microfluidic chip is shown, schematically and very schematically simplified, in which substrate only one fluid conduit 312 in the form of a channel is constructed. A fluid, not shown, is forced through the fluid line 312 in the direction indicated by arrow 13. The fluid line or channel has a cross section which is delimited on each side transversely to the flow direction by a side wall. The cross section is defined in a first direction perpendicular to the flow direction by a channel bottom 314 and a cover, not shown, at a position 316 opposite the channel bottom.

The channel 312 is again functionally divided in the flow direction into an entry section 318, a downstream holding section 320 and a further downstream discharge section 322.

The retaining section 320 is divided laterally, i.e. transversely to the flow direction 13, into a narrow region 324 and a wide region 326 laterally adjoining it.

The fluid line has a side wall spacing h in the narrow region 324 in the first transverse direction between the channel bottom 314 and the cover (position 316)_eWhich in this case is determined by the channel depth. Minimum sidewall spacing through h of broad area 326_wTo represent and in the example shown extend in another transverse direction.

As can be seen in the cross-sectional illustration of fig. 9c, the spacing h_eLess than the minimum sidewall spacing h of the expanse_w. This condition is only decisive for the fact that the more wetting liquid flowing into the holding section is held in the narrow region 324 by capillary forces or the less wetting liquid flowing into the holding section is held in the wide region 326. Likewise, it is not decisive here whether the side wall spacings are identical to one another in the same or different directions. Likewise, it is not important whether the narrow region is wider or narrower than the minimum sidewall spacing h of the wide region in the second lateral direction_w。

H being present here_eIt is also particularly suitable, in coincidence with the channel depth, for the channel depth in the wide area 326 to be greater than its width, which in this example defines the smallest side wall spacing h_w。

As can also be seen in fig. 9a to 9c, the entry section 318 and the discharge section 322 have a side wall spacing h in the first transverse direction perpendicular to the channel bottom 314_inAnd h_outWhich corresponds to the channel depth in the broad area 324 of the retention section 420. Thus, the entry section318 and the exhaust section 322 steplessly transition in a first lateral direction into a wide area 324. In other words, the channel bottom 314 continues flat in the entry and exit sections and in the broad area 324 of the holding section 320.

Whereas the narrow region 326 forms, starting from the channel bottom 314, a transverse transition in the form of a shoulder 328 extending in the flow direction 13. In this embodiment, shoulder 328 in turn has a sharp edge 329.

Fig. 10a to 10c show a further embodiment of the invention in a plan view, in a longitudinal section and in a transverse section, analogously to fig. 9a to 9 c. The substrate of the microfluidic chip, which is very schematically simplified, is indicated with 410, in which only one fluid conduit 412 in the form of a channel is constructed. A fluid, not shown, is forced through the fluid line 412 in the direction indicated by arrow 13. The fluid line or channel has a cross section which is delimited on each side transversely to the flow direction by a side wall. The cross section is defined in a first direction perpendicular to the flow direction by a channel bottom 414 and a cover, not shown, at a position 416 opposite the channel bottom 414.

The channel 412 is again functionally divided in the flow direction into an entry section 418, a downstream holding section 420 and a further downstream discharge section 422.

The retaining section 420 is divided in the transverse direction, i.e. transversely to the flow direction 13, into a narrow region 424 and a wide region 426 laterally adjoining it.

Unlike the embodiment according to fig. 9, the fluid line 412 in the embodiment according to fig. 10 widens in the retaining section 420, analogously to the example in fig. 3, in a second direction perpendicular to the flow direction 13 transversely with respect to the inlet section 418 and transversely with respect to the outlet section 422. The broad area 426 is located at an edge of the fluid conduit 412 in the second lateral direction and is thus arranged offset in the second lateral direction with respect to the entry section 418 and with respect to the exit section 422.

The lateral widening in turn facilitates a narrow region 424 which is wider in the second direction than the inlet section and the outlet section. Thus, since in the first transverse direction from h_inReduction to h_eCan be partially compensated for and the flow velocity in the narrow region 424 is reduced with constant volume flow.

Furthermore, the fluid line, as in the example in fig. 9, has a side wall spacing h in the first transverse direction in the narrow region 424 between the channel base 414 and the cover (location 416)_eWhich is determined by the channel depth. Minimum sidewall spacing through h of broad area 426_wTo represent and extend in a second, different lateral direction.

As can be seen in the cross-sectional illustration of fig. 10c, the spacing h_eLess than the minimum sidewall spacing h of the expanse_w. This condition is only decisive for the fact that the more wetting liquid flowing into the holding section is held in the narrow region 424 or the less wetting liquid flowing into the holding section is held in the wide region 426 due to capillary forces. Likewise, it is not decisive here whether the side wall spacings are identical to one another in the same or different directions. It is also not important whether the narrow region is wider or narrower than the minimum sidewall spacing h of the wide region in the second lateral direction_w。

H being present here_eCoinciding with the channel depth, it is also applicable that the channel depth in the broad area 426 is greater than its width, which in this example defines the smallest side wall spacing h_w。

As can also be seen in fig. 10a to 10c, the inlet section 318 and the outlet section 422 have a side wall spacing h in the first transverse direction perpendicular to the channel bottom 414_inAnd h_outWhich corresponds to the channel depth in the broad area 424 of the retention segment 420. Thus, the entry section 418 and the exit section 422 transition steplessly in the first lateral direction into the wide area 424. In other words, the channel bottom 414 continues flat in the intake and exhaust sections and in the broad area 424 of the holding section 420.

The narrow region 426 again forms, starting from the channel bottom 414, a transverse transition in the form of a shoulder 428 extending in the flow direction 13. In this embodiment, shoulder 428 again has a sharp edge 429.

Fig. 11a to 11c show a sequence of liquid flow into the fluidic structure, this time the fluidic structure according to fig. 9, similar to fig. 5a to 5 c. All three snapshots show schematically and very schematically the same section of the microfluidic chip 510 with a substrate 520 in which fluid lines 522 in the form of channels are machined. Here again, a cover 525 in the form of a film is shown, which closes a channel which is open on one side in the transverse direction.

The fluid conduit 522 is shown in cross-section in the region of a retaining section in which it includes a narrow region 534 of lesser channel depth and laterally adjoining wide regions 536 of greater channel depth. The first fluid 540 flowing in the direction 13 has a front edge or interface 542 which is still located in the entry section at the time according to fig. 11 a.

In fig. 11b, the first fluid 540 continues to travel, so that the rear interface 544 of the first fluid is already visible in the entry section. The first fluid 540 forms a so-called fluid column. The front interface 542 has reached the holding section of the fluid conduit and due to capillary forces enters the broad area 536, while it avoids the narrow area 534. The capillary forces in this case act differently from the situation in fig. 5 due to the opposite wetting behavior.

Behind the liquid column there is a buffer medium 546 which spatially separates the first fluid 540 from a subsequent second fluid 550, which is visible in fig. 11c in the intake section. At some point, the rear interface 544 of the first liquid column 540 also reaches the beginning of the wide area 536 of the holding section by further travel of the two fluid columns. Here, the rear interface 544 of the first liquid column 540 is detached from the wall of the fluid channel 522, where the narrowed region 534 is present. The narrow region 534 then releases a bypass line through which the buffer medium 546 can escape, as symbolically indicated by an arrow 552. At this point, the first fluid column 540 is stopped in the holding area because it is no longer sensing the delivery pressure. Thus, the subsequent liquid column 550 may continue to be conveyed in the direction of the first liquid column 540 until the two liquid columns merge. And then both are transported further together. This can be arranged such that the combined liquid column runs completely around the gas cushion in the bypass line, or the combined liquid column first empties the bypass line and only then leaves the holding region completely. In this regard, the process depends on the details of the construction of the transition section.

The system referred to in the example in fig. 11 therefore has: fluidic structure or microfluidic chip in which the broad region 536 has a volume V_w(ii) a A first liquid 540 having a defined volume V_Fl1(ii) a A second liquid 550 having a defined volume V_Fl2(ii) a And a buffer medium 546 which is arranged between the first liquid and the second liquid at the inlet of the holding region and can be conveyed through the fluid line 522 together with the first liquid and the second liquid, wherein the first liquid 540 and the second liquid 550 wets the side walls of the fluidic structure more weakly than the buffer medium 546, and wherein the applicable conditions are: v_Fl1<V_wAnd V is_Fl1+V_Fl2>V_W. If

fluids

540 and 550 are water-based and the sidewalls of the fluid lines are hydrophobic, buffer medium 546 may be, for example, a gas or an oil.

List of reference numerals

10 base

12 fluid line/channel

13 direction of flow

14 channel bottom

Upper side of 16 channels

18 entry zone

20 holding section

22 discharge section

24 narrow region

26 wide area

28 shoulder

29 edge

30 base

32 fluid line

34 channel bottom

34' channel bottom

35 ramp-like channel bottom

35' ramp-like channel bottom

36 upper side of the channel

38 into the section

39 first transition section

40 holding section

41 second transition section

42 discharge section

44 narrow region

46 wide area

48 convex shoulder

49 edge

60 base

62 fluid line/channel

65 ramp-like channel bottom

65' ramp-like channel bottom

68 into the section

69 transition section

70 holding section

71 second transition section

72 discharge section

74 narrow region

76 broad area

78 shoulder

79 lateral wall of a fluid line

80 base

82 fluid line/channel

84 channel bottom

88 entry section

89 transition section

90 holding section

91 second transition section

92 discharge section

94 narrow region

96 wide area

98 shoulder

99 edge

100 lateral wall of the intake and discharge sections

101 wall in transition and holding sections

102 wall in transition and holding sections

104 end of wide area

105 stop structure/hollow shape/dead end channel

106 stop structure/hollow shape/dead end channel

110 microfluidic chip

120 substrate

122 fluid line

125 cover/film

134 narrow region

136 wide area

140 first fluid/fluid column

142 front interface of first fluid column

144 rear interface of the first fluid column

146 buffer medium

150 second fluid/fluid column

152 flow arrow

158 fluid passage

160 stop structure

162 projection

163 channel bottom

164 narrow region

170 microfluidic chip

172 fluid line/channel

174 narrow region

176 wide area

178 shoulder

180 edge

182 wide area channel bottom

184 round

190 micro-fluidic chip

192 fluid line/channel

194 narrow region

196 wide region

202 (in a wide area) channel bottom

203 channel bottom in narrow area

208 into the section

209 first transition section

210 holding section

211 second transition section

212 discharge section

310 base

312 fluid line/channel

314 channel bottom

Upper side of 316 channel

318 entry section

320 holding section

322 discharge section

324 narrow region

326 wide area

328 shoulder

329 edge

410 base

412 fluid line/channel

414 channel bottom

416 upper side of the channel

418 entering section

420 holding section

422 discharge section

424 narrow area

426 broad area

428 shoulder

429 edge

510 microfluidic chip

520 substrate

522 fluid line

525 cover/film

534 narrow area

536 broad area

540 first fluid/fluid column

542 front interface of first fluid column

544 rear interface of the first fluid column

546 buffer media

550 second fluid/fluid column

552 flow arrows

Claims

1. A fluidic structure adapted to control one or more fluids, having a fluid line (12, 32, 62, 82, 122, 172, 192, 312, 412, 522) which defines a flow direction (13) and a cross-section perpendicular to the flow direction (13) which is bounded on each side by a side wall, characterized in that the fluid line (12, 32, 62, 82, 122, 172, 192, 312, 412, 522) has a holding section (20, 40, 70, 90, 210, 320, 420) which extends in the flow direction (13) and is free of further inlet and outlet lines, in which holding section the fluid line (12, 32, 62, 82, 122, 172, 192, 312, 412, 522) has a narrow region (24, 44, 74, 94, 134, 174, 194, 324, 424, 534) and a wide region (26, b) adjoining transversely with respect to the flow direction, 46. 76, 96, 136, 176, 196, 326, 426, 536), wherein the narrow region (24, 44, 74, 94, 134, 164, 174, 194, 324, 424, 534) has a smallest side wall spacing h in at least one first direction perpendicular to the flow direction (13) than the wide region (26, 46, 76, 96, 136, 176, 196, 326, 426, 536)_wSmaller sidewall spacing h_eWherein the fluid line (12, 32, 62, 82, 122, 172, 192, 312, 412, 522) has an inlet section (18, 38, 68, 88, 208, 318, 418) upstream of the holding section (20, 40, 70, 90, 210, 320, 420) in the flow direction (13) and an outlet section (22, 42, 72, 92, 212, 322, 422) downstream of the holding section (20, 40, 70, 90, 210, 320, 420) in the flow direction (13), wherein the inlet section (18, 38, 68, 88, 208, 318, 418) and the outlet section (22, 42, 72, 92, 212, 322, 422) in the first direction steplessly transition into a narrow region (24, 44, 74, 94, 134, 164, 174, 194) of the holding section (20, 40, 70, 90, 210) or into a wide region (176) of the holding section (210, 320, 420), 196. 326, 426, 536) of the first group,

wherein the inlet section (38, 68, 88, 208) has a first direction perpendicular to the flow direction (13)With a side wall spacing h_in>h_eAnd the fluid line (32, 62, 82, 192) has a first transition section (39, 69, 89, 209) downstream of the inlet section (38, 68, 88, 208) and upstream of the holding section (40, 70, 90, 210) in the flow direction (13), in which transition section the sidewall distance in the flow direction (13) is measured from h_inSteadily decrease to h_eAnd is and

wherein the discharge section (42, 72, 92, 212) has a sidewall spacing h in a first direction perpendicular to the flow direction (13)_out>h_eAnd the fluid line (32, 62, 82, 192) has a second transition section (41, 71, 91, 211) downstream of the holding section (40, 70, 90, 210) and upstream of the discharge section (42, 72, 92, 212) in the flow direction (13), in which second transition section the sidewall distance in the flow direction (13) is measured from h_eSteadily widen to h_out。

2. A fluid structure according to claim 1, characterised in that a transverse transition in the form of a shoulder (28, 48, 78, 98, 178, 328, 428) extending in the flow direction (13) between the narrow region (24, 44, 74, 94, 134, 164, 174, 194, 324, 424, 534) and the wide region (26, 46, 76, 96, 136, 176, 196, 326, 426, 536) is configured.

3. A fluid structure according to claim 2, characterized in that the narrow region (24, 44, 74, 94, 134, 164, 174, 194, 324, 424, 534) is configured between a plateau of the shoulder (28, 48, 78, 98, 178, 328, 428) and an opposite side wall section, wherein the first direction is perpendicular to the plateau.

4. The fluidic structure according to any one of claims 1 to 3, characterized in that the fluid line (62, 82, 412) has an entry section (68, 88, 418) upstream of the holding section (70, 90, 420) in the flow direction (13) and has a discharge section (72, 92, 422) downstream of the holding section (70, 90, 420) in the flow direction (13), wherein the fluid line (62, 82, 412) widens laterally in the holding section (70, 90, 420) in a second direction perpendicular to the flow direction (13) relative to the entry section (68, 88, 418) and the discharge section (72, 92, 422).

5. The fluidic structure according to claim 4, characterized in that the broad areas (76, 96, 426) are arranged offset with respect to the intake section (68, 88, 418) and/or with respect to the discharge section (72, 92, 422) in a second direction perpendicular to the flow direction (13).

6. A fluidic structure according to any one of claims 1 to 3, characterized in that the fluidic circuit (82, 158) has at least one stop structure (105, 106, 160) upstream and/or downstream of the holding section (90) in the flow direction (13).

7. A fluid structure according to claim 6, characterized in that the at least one stop structure (105, 106, 160) is configured in the form of a shoulder interrupting the course of at least one side wall of the fluid line (82, 158).

8. A fluid structure according to claim 7, characterized in that the at least one stop structure (105, 106) is configured as a hollow shape in at least one side wall of the fluid line (82).

9. The fluidic structure of claim 7, wherein the at least one stopping structure (160) is configured as a protrusion (162) along at least one sidewall of the fluid conduit (158).

10. A microfluidic chip (110, 170, 190, 510) comprising a substrate (10, 30, 60, 80, 120, 310, 410, 520), a cover (125, 525) for the substrate (10, 30, 60, 80, 120, 310, 410, 520) and a fluidic structure in the substrate (10, 30, 60, 80, 120, 310, 410, 520) according to any one of claims 1 to 9, characterized in that the fluidic circuit (12, 32, 62, 82, 122, 172, 192, 312, 412, 522) is configured in the form of a channel in the substrate (10, 30, 60, 80, 120, 310, 410, 520) and is closed by the cover (125, 525), wherein the channel is divided in the holding section (20, 40, 70, 90, 210, 320, 420) into narrow regions (24, 44, 74, 94, 134, 164, 174, 194, 324), 534) And a broad area (26, 46, 76, 96, 136, 176, 196, 326, 426, 536).

11. A microfluidic chip (110, 170, 190, 510) according to claim 10, wherein the broad regions (26, 46, 76, 96, 136, 176, 196, 326, 426, 536) have a greater channel depth than the narrow regions (24, 44, 74, 94, 134, 164, 174, 194, 324, 424, 534).

12. Microfluidic chip (110, 170, 190, 510) according to claim 10 or 11, wherein the first direction is perpendicular to the channel bottom (14, 34', 84, 163, 202, 203, 314, 414) opposite the cover (125, 525).

13. Microfluidic chip (110, 170, 190, 510) according to claim 12, characterized in that the channel bottom (14, 34', 84, 63, 202, 314, 414) in the entry section (18, 38, 68, 88, 208, 318, 418) in the flow direction (13) upstream of the holding section (20, 40, 70, 90, 210, 320, 420) and in the exit section (22, 42, 72, 92, 212, 322, 422) in the flow direction (13) downstream of the holding section (20, 40, 70, 90, 210, 320, 420) steplessly transitions into the channel bottom of the narrow region (24, 44, 74, 94, 134, 164, 174, 194) or into the channel bottom of the wide region (176, 196, 326, 426, 536).

14. Microfluidic chip (110, 170, 190, 510) according to claim 13, characterized in that the channel bottom of the narrow region (24, 44, 74, 94, 134, 164, 174, 194, 324, 424, 534) forms a plateau in the sense of claim 3.

15. A system having a fluidic structure according to any of claims 1 to 9 or a microfluidic chip (110, 510) according to any of claims 10 to 14, wherein the narrow region (134, 534) has a volume V_eAnd the broad area (136, 536) has a volume V_wThe system comprises:

having a defined volume V_Fl1Has a defined volume V, a first liquid (140, 540)_Fl2Of the second liquid (150, 550),

and a buffer medium (146, 546) arranged between the first liquid and the second liquid at the holding section inlet and transportable together with the first liquid and the second liquid through the fluid line (122, 522).

16. The system of claim 15, wherein,

-the first liquid and the second liquid wet the side walls of the fluidic structure more strongly than the buffer medium, and wherein the applicable conditions are: v_Fl1<V_eAnd V is_Fl1+V_Fl2>V_eOr is or

The first liquid and the second liquid wet the side walls of the fluidic structure weaker than the buffer medium, and wherein the applicable conditions are: v_Fl1<V_wAnd V is_Fl1+V_Fl2>V_w。