EP2308589B1 - Microfluid structure - Google Patents

Description

The invention provides a microfluidic structure for the combination of liquid volumes and a microfluidic system with such a microfluidic structure.

Microfluidic systems have been the subject of biotechnological research and development in recent years and are increasingly being used in the form of so-called lab-on-a-chip systems, among others. also used for medical diagnosis in point-of-care products. The terms microfluidic system and lab-on-a-chip are used synonymously here. On these microfluidic chip systems, previously processed protocols in the laboratory are converted as completely as possible into a microfluidic structure on the Lab-on-a-Chip, so that the protocols are largely automated and run with as few manual interventions as possible. The chip systems are usually used with operator equipment, the operator equipment is equipped with a receptacle for the chip and possibly electrical, fluidic and aktuatorischen interfaces to the chip.

The microfluidic systems contain different microfluidic structures with size dimensions in the micrometer range, wherein individual microfluidic structures, in particular fluid chambers or fluid reservoirs, can also have larger cross sections down to the millimeter range. Often the microfluidic systems are formed by a base plate with trenches and depressions formed therein and a lid foil closing the trenches and depressions. The base plates are molded from plastic by injection molding or embossing process and the lid films by adhesive or welding process fluid-tightly connected to the base plates. Also known are modular microfluidic systems comprising a plurality of planar and / or block-shaped microfluidic modules, as described, for example, in the publication Drese, K .; by Germar, F .; Ritzi, M .: "Sample preparation in Lab-on-a-Chip Systems - Combining modules to create a fully integrated system" In: Medical Device Technology 18 (2007) 1, 42-47 to be discribed. These individual modules are coupled with each other via suitable connections in order to be able to realize different process paths depending on the task.

A frequently occurring process operation within microfluidic systems is i.a. the union of different volumes of fluid. There are already various solutions for this.

State of the art

In the publication of Götz Münchow, Dalibor Dadic, Frank Doffing, Steffen Hardt, Klaus-Stefan Drese "Automated chip-based device for simple and fast nucleic acid amplification", in Expert Rev. Mol. Diagn. 5 (4), (2005 ) is in Figure 7 and the associated description (page 616, left column) given a microfluidic structure for the union of two volumes of liquid. The Y-shaped structure has for this purpose two at an acute angle converging leads, which are combined in a channel. In the area of the mouths of the supply lines in the channel, the supply lines are narrowed in their cross section. The liquids to be combined are introduced into the supply lines and, due to capillary forces occurring, penetrate into the constrictions of the supply lines, but stop at the end of the constrictions prior to entry into the channel which is widened in cross-section. Only when a pressure pulse is applied to at least one supply line can the capillary force counteract the passage of the liquid into the channel be overcome and triggers the union of the liquids in the channel.

In the European patent application EP 1 932 593 A1 is a microfluidic structure for the combination of liquids specified, in which a feed line for a first liquid opens into a channel. The first liquid is given in a connected to the supply line and open to the environment reservoir and flows due to capillary forces to the mouth of the supply line into the channel. The first liquid is taken up by a second liquid, which is also conveyed in the channel by capillary forces. Important for this type of fluid management is the correct coordination of the capillary forces acting in the channel, feed opening and reservoir by structure sizes and surface quality. Furthermore, aeration of the reservoir is necessary.

In the US Pat. No. 7,247,274 B1 a microfluidic structure according to the preamble of claim 1 is disclosed.

definitions

Under microfluidic structures and systems according to the invention specified systems and structures understood, the fluid channels have cross-sectional dimensions with sizes in at least one orientation perpendicular to the flow direction in the range 10 microns to 2000 microns and more preferably in the range of 25 microns - 1500 microns. The liquid volumes transported and stored in these microfluidic systems and structures are in the nanometer to multi-digit microliter range for small volumes, and in the larger volumes up to the milliliter range.

Pressure-actuated or pressure-operated in the sense of the microfluidic systems or structures according to the invention means that fluid volumes in the microfluidic systems or structures according to the invention can be driven or driven via a delivery pressure acting from outside the microfluidic system or the microfluidic structure, for example generated by a syringe pump. A passive drive, for example a drive acting solely by means of capillary forces, is not possible and provided for the microfluidic systems or structures according to the invention since the cross-sectional dimensions of the microfluidic structures in the microfluidic systems according to the invention are at least partially so large or the surface textures of the microfluidic structures are formed in this way in that there is insufficient capillary pressure for the reliable delivery of fluid through the microfluidic systems.

On the other hand, capillary drive of the liquids is possible in individual sections of the microfluidic systems according to the invention.

A drive of liquid volumes in the microfluidic systems or structures according to the invention using magnetorheological fluids or ferrofluids can also be used in alternative embodiments. In this case, in the flow direction in front of or behind the volumes of liquid to be transported in the channels or structures of the microfluidic system are plugs of a magnetorheological fluid or a ferrofluid brought. A drive of the plugs and the respectively associated liquid volumes takes place via magnets which are moved parallel to the fluid structures. In a further variant of this type of drive, a plug of a magnetorheological fluid or a ferrofluid is moved in a cross-sectionally larger channel section and generates a delivery pressure in a fluidically connected with this channel cross-sectional smaller channel via movements. Due to the different cross-sectional sizes of the channels, it is possible to achieve a high delivery capacity in the smaller cross-section channels with short adjustment paths of the magnets. In the case of also possible, inverse size ratios of the cross sections, a very positional and / or pressure accurate delivery in the smaller cross-section channels can be achieved.

task

The invention has for its object to provide a simple microfluidic structure for bubble-free union of liquid volumes and a Lab-on-a-chip with such a microfluidic structure.

description

The object is achieved by a microfluidic structure according to claim 1 and a lab-on-a-chip according to claim 14.

The pressure-actuatable, microfluidic structure according to the invention for bubble-free combination of a first and a second fluid volume has a fluid chamber with an addition opening and a respective inlet and outlet channel opening into the fluid chamber.

The fluid chamber has a fluid chamber cross-section widened in the direction of flow from the supply line to the discharge channel with respect to the supply channel and is set up by the widened cross-section, a substantially pressure-driven first fluid volume through the supply passage and through the fluid chamber in the entire flow through the fluid chamber in its cross section to a corresponding at least approximately the full cross section of the fluid chamber cross section, ie at least 75%, preferably 95% of the cross-sectional area widen.

The formation of the expansion from the supply channel to the fluid chamber cross section in the form of a continuous expansion, preferably curved expansion, without corners and edges, supports the expansion of the first fluid volume to the at least approximately full cross section of the fluid chamber during the entire flow through the fluid chamber.

The fluid chamber has a holding position for a second fluid volume. The holding position is designed in such a way that a second liquid volume introduced through the feed opening into the fluid chamber can be held in the region of the holding position, so that only part of the fluid chamber cross-section is filled and the second liquid volume is taken up by the first liquid volume during pressure-driven passage and as a combined liquid volume is passed through the fluid chamber in the discharge channel.

In the case of small second liquid volumes, the contact surfaces forming between the small, second liquid volume and the fluid chamber, preferably contact surfaces to the base, ceiling and a wall surface of the fluid chamber in the region of the feed opening, are sufficient to form a limited holding position as holding structures. Preferably, the holding position for the second liquid volume is formed in a region of the fluid chamber with at least one at least partially curved and / or at least partially trough-shaped wall, floor and / or ceiling surface as a holding structure. The curvature and / or trough increases the contact area between the second fluid volume and the fluid chamber and generates higher holding forces. This is preferably a curvature or depression of a surface formed locally in the region of the holding position.

Due to the simple, less demanding design, a microfluidic structure according to the invention allows a hardly error-prone and safe operation and economical production. The inclusion of air bubbles in the combined liquid volume is safely avoided in a simple procedure of the union of the liquid volume in the microfluidic structure.

Further embodiments:

The surfaces of the channels and the fluid chamber of the microfluidic structure according to the invention and / or of the lab-on-a-chip can be made wettable by the material selection and / or the production method. However, coatings or other surface-wettable processes are also possible. Wettable means in a microfluidic structure for aqueous solutions to select a hydrophilic surface with a contact angle of greater than 0 ° to less than 90 °, or preferably with a contact angle of 5 ° to 70 °. In the case of very low contact angles, there is a risk of liquid creeping along the surfaces and edges. In the case of microfluidic structures for organic, non-polar solutions, lipophilic surfaces are preferred.

By virtue of the surfaces of the microfluidic structure of the invention which are wettable in the stated manner, the first liquid, when flowing through the fluid chamber in contact with the wall, floor and ceiling surfaces, is clamped onto the full cross-section of the fluid chamber, there is no possibly gas-permeable interspace between the first liquid and Wall, floor and ceiling surfaces when flowing through the fluid chamber.

The hydrophilization or lipophilization can be carried out in a known manner by a dipping method, as in DE 100 13 311 C2 described or carried out by a coating. For example, polycarbonate can be hydrophilized as a weakly hydrophobic material by an oxygen plasma treatment on the surface.

The polymer material in which the microfluidic structure or the lab-on-a-chip according to the invention is preferably produced is preferably an injection-moldable or (hot) embossable polymer, particularly preferably a thermoplastic or even elastic thermoplastic. One or more of the following materials may also be used include acrylate, polymethyl acrylate, polymethyl methacrylate, polycarbonate, polystyrene, polyimide, cycloolefin copolymer (COC), cycloolefin polymer (COP), polyurethane, epoxy resin, halogenated acrylate, deuterated polysiloxane, PDMS, fluorinated polyimide, polyetherimide, perfluorocyclobutane, perfluorovinyl ether copolymer (Teflon AF), perfluorovinyl ether cyclopolymer ( CYTOP), polytetrafluoroethylene (PTFE), fluorinated polyarylethersulfide (FRAESI), inorganic polymer glass, polymethyl methacrylate copolymer (P2ANS).

In further embodiments, the microfluidic structure according to the invention and the lab-on-a-chip can also be made of glass, silicon, metal and / or ceramic, depending on the application. A combination of different of the mentioned materials can also be used for the production, for example one Glass or silicon base plate with incorporated channels and chambers can be covered by polymer films.

In a preferred embodiment of the invention, the fluid chamber has a cross section, which is widened by not more than 5 times, more preferably not more than 2.5 times, in relation to the supply channel. This limited widening of the fluid chamber with respect to the feed channel ensures that the first volume of liquid is expanded in the pressure-driven flow through the fluid chamber to the at least approximately full cross-section of the fluid chamber.

The fluid chamber has a preferably elongated shape, i. its length in the flow direction is greater than its largest cross-sectional dimension of the fluid chamber, more preferably by several times longer than the largest cross-sectional dimension of the fluid chamber. The supply and / or discharge channel respectively opens at a short side or tip into the elongated fluid chamber.

The fluid chamber can also be formed asymmetrically in the flow direction with only one-sided widening, ie in plan view, for example, triangular, trapezoidal or or circular segment-shaped, wherein the supply and discharge channels are each in the region of the ends of the longest side and the ends of the chord.

In further, advantageous embodiments of the microfluidic structure according to the invention, further structures may be provided in the fluid chamber to assist the merging of the fluid volumes. It can be mounted, for example, in the mouth region of the supply passage in the fluid chamber a one-sided curved into the fluid chamber in the indentation. A fluid volume flowing into the fluid chamber via the supply channel is initially only guided along a wall surface of the fluid chamber and only expanded in the flow direction downstream of the structure to support the merger onto the at least approximately full fluid chamber cross section. This formation of the fluid chamber supports the expansion of the first fluid volume to the at least approximately full cross-section of the fluid chamber, without, for example, a breakthrough of a conveying gas.

In the case of asymmetrically shaped fluid chambers, the first volume of liquid is guided in this way from the wall surface near the longest side or along the circular chord to a central flow line in the fluid chamber lying in the fluid chamber, so that a less pronounced, double-sided widening the liquid volume can be made subsequent to the structures for assisting the merge along the central flow direction.

The addition opening and / or holding position for the second liquid volume are preferably decentralized, ie arranged away from a central flow line from the supply channel through the fluid chamber to the discharge channel in the fluid chamber. In the case of the asymmetrical shaping of the fluid chamber, the feed opening and / or holding position in the flow direction in the region of the one-sided bulge of the fluid chamber, also be disposed away from the central flow line from the supply line to the discharge channel through the fluid chamber.

This shaping prevents a gas flowing through the microfluidic structure from entraining a second volume of liquid already introduced into the microfluidic structure before the first volume of liquid passes into the fluid chamber.

In a preferred embodiment of the invention, the addition port is closable. The pressure difference prevailing in the pressure-driven drive of the liquids can be kept at a lower level in the case of a closed addition opening and it is possible to operate at a pressure lowered in relation to the surroundings. The addition opening is preferably designed to be self-closing, for example by attaching a septum or an elastic lidding film. It is therefore possible to apply sample liquids as second liquid volumes without the risk of the sample liquids emerging from the microfluidic structure according to the invention. Also, a contamination of the interiors of the microfluidic structure according to the invention can be prevented.

In a further embodiment, the feed opening can also be designed to be closable by a sealing element which can be displaced relative to the feed opening. The sealing element in this embodiment is a component of the microfluidic structure. In the case of the use of a displaceable sealing element, the sealing element preferably has engagement elements into which corresponding actuators of the operator device can intervene during operation in an operator device.

A configuration of the feed opening, which is to be opened and closed via an operator device, is provided in a further preferred embodiment of the microfluidic structure according to the invention. For this purpose, the feed opening has, for example, a sealing surface which, when the microfluidic structure is operating in an operator device, is fluidically tightly connected to a closable fluid line of the operator device or can be opened and closed by an active sealing element of the operator device.

The opening width of the feed opening is preferably small, ie less than 1/20 and more preferably less than 1/100, compared to the largest cross-sectional area of the fluid chamber in the flow direction from the feed channel to the discharge channel. With a small opening width of the addition opening reduces the risk of contamination. If it is envisaged not to close the feed opening during operation of the microfluidic structure, there is also no risk of leakage of the liquids conveyed in the microfluidic structure given a small opening width of the feed opening.

In a further preferred embodiment, the feed opening can also be designed as a channel opening into the fluid chamber. In order to ensure an unimpeded flow through the fluid chamber during operation of the microfluidic structure from the feed channel to the discharge channel, the cross section of the feed openings in a preferred embodiment is very small in relation to the cross-sectional area of the fluid chamber transversely to the flow direction, preferably less than 1/20. The addition opening can also be designed to be closable in this embodiment.

The fluid chamber can also have a plurality of feed openings for adding a plurality of second liquid volumes. It can be combined with each other in this way more than just two volumes of liquid or the addition amount can be distributed to a plurality of feed openings and holding positions.

Preferably, a holding position is arranged in the fluid chamber per addition opening. The added second volumes of liquid are thus brought into communication with each other only when a first volume of liquid is passed through the fluid chamber and receives the second volumes of liquid sequentially.

In further embodiments, holding structures in the region of the holding positions in addition to the o.g. Structures or formed as a sole support structure. These holding structures alone or in differently designed combinations of alternative holding structures ensure the secure positioning and fixing of small to larger second liquid volumes in the microfluidic structure according to the invention.

The holding position may have, for example, special surface structures such as depressions, surface finishes or one or more steles as holding structures. For example, changes in the surface energies (contact angle) to the Localization of the stored drops can be used. Preferably, the contact angle of the second volume of liquid to the surface of the support structure is greater than 0 ° and less than 90 °, more preferably greater than 5 ° and less than 70 °.

In a further embodiment, structures for the secure positioning of the second liquid volume on the holding position comprise in particular two-sided structures, such as stelae on both sides of the feed opening in the fluid chamber, since in this way the holding position for the second liquid volume is formed between these steles and additional holding surfaces for can form the second volume of fluid to the fluid chamber.

Furthermore, different heights of the fluid chamber can be used for secure positioning of the second fluid volume. In the region of the holding position, the fluid chamber is, for example, designed to be lower than in the remaining region of the fluid chamber, so that the second fluid volume has a contact with the bottom, top and side walls of the fluid chamber in the region of the holding position.

In further embodiments, surface roughnesses of the fluid chamber walls are employed as holding structures in the holding position to support hysteresis effects to assist in secure positioning of the second fluid volume.

The holding position occupies only a part of the fluid chamber cross section, so that not the entire fluid chamber cross section is blocked. The restriction of the holding position to portions of the fluid chamber can be supported by the corresponding localized formation of support structures in the holding position.

In microfluidic systems consisting of a base plate with cover film, the so-called lab-on-a-chip, the feed openings are preferably formed as a hole above the fluid chamber in a lid film. In a further embodiment, however, the feed openings may also be formed as openings in the bottom and / or side surfaces of the fluid chamber in the base plate.

In a further embodiment of the microfluidic structure according to the invention, a plurality of fluid chambers with feed openings are arranged one behind the other. This embodiment allows the sequential union of liquids. It can be carried out so consecutive reactions.

In further embodiments, the microfluidic structure according to the invention may also have further elements which assist in widening and flowing through the fluid chamber, for example to the almost full cross-section of the fluid chamber, with complete wetting of the wall, bottom and top surface of the fluid chamber in accordance with the invention, for example single or multi-sided, continuous shaped cross-sectional constrictions in the transition from the inlet channel to the fluid chamber.

In a further embodiment of the invention, after the union of the liquid volumes and the forwarding via the discharge channel, the flow direction of the combined liquid volumes can also be reversed.

The invention also comprises a lab-on-a-chip having at least one microfluidic structure according to one of the aforementioned embodiments, wherein the lab-on-chip additionally comprises a plurality of further channels, chambers and 1 or reservoirs. The lab-on-a-chip according to the invention is therefore suitable for carrying out a plurality of successive process steps including the bubble-free combination of two liquid volumes in the microfluidic structure according to the invention.

Such a lab-on-a-chip may already be prefilled with certain chemicals in some chambers and / or reservoirs during production. During operation, for example, the sample to be processed is then introduced into the lab-on-a-chip via the feed opening and a process chain is processed using suitable actuators in the operator device using the chemicals already stored on the chip.

The lab-on-a-chip can have the microfluidic structures according to the invention once or several times in the flow direction of the fluids in successive or also parallel arrangement, so that sequential or parallel combinations of liquid volumes can be done. In the case of the sequential arrangement, reaction sequences can be processed in the Lab-on-a-Chip. In a parallel arrangement, parallel running process chains can be processed on a chip.

The invention is not limited to the embodiments and the following embodiments described above, but also comprises novel feature combinations formed from the basic idea of the invention given in claim 1 or claim 14 and individual features and feature combinations of the preferred embodiments as well as the exemplary embodiments.

In the following exemplary embodiments, the microfluidic structures according to the invention, which are designed as trenches and depressions in a base plate and covered with a foil, are usually illustrated alone. However, in microfluidic systems, the microfluidic structure according to the invention represents only a part of the structures in the overall system, i. In addition to the microfluidic structure according to the invention, other elements, such as channels, chambers, reservoirs, actuators, etc., are contained in these systems and are connected to one another constructively or functionally.

Figur 1:

Schematische Darstellung einer erfindungsgemäßen mikrofluidi- schen Struktur in der Draufsicht mit drei alternativen Ausführungs- formen der mikrofluidischen Struktur;

Figur 2a bis 2c:

Schematische Darstellung des Vorgangs der Vereinigung der Flüssigkeitsvolumina in einer erfindungsgemäßen mikrofluidischen Struktur;

Figur 3:

Schematische Darstellung der sequentiellen Abfolge zweier erfin- dungsgemäßer mikrofluidischer Strukturen in der Draufsicht;

Figur 4:

Schematische Darstellung der parallelen Anordnung zweier erfin- dungsgemäßer mikrofluidischer Strukturen in der Draufsicht;

Figur 5a bis 5d:

Darstellung des Querschnitts dreier erfindungsgemäßer mikrofluidi- schen Strukturen;

Figur 6:

Schematische Darstellung einer erfindungsgemäßen mikrofluidi- schen Struktur in der Draufsicht mit Haltestrukturen im Bereich der Haltepositionen in der Draufsicht;

Figur 7:

Schematische Darstellung einer erfindungsgemäßen mikrofluidi- schen Struktur im Bereich eines Sackgassenkanals in der Drauf- sicht;

Figur 8:

Schematische Darstellung einer erfindungsgemäßen mikrofluidi- schen Struktur mit einer die Vereinigung der Flüssigkeitsvolumina fördernden Struktur in der Draufsicht.

Figur 9:

Lab-on-a-Chip / mikrofluidisches System für die Durchführung einer PCR-Reaktion in der Draufsicht

In the following individual embodiments are shown:

FIG. 1:

Schematic representation of a microfluidic structure according to the invention in plan view with three alternative embodiments of the microfluidic structure;

FIGS. 2a to 2c:

Schematic representation of the process of combining the liquid volumes in a microfluidic structure according to the invention;

FIG. 3:

Schematic representation of the sequential sequence of two inventive microfluidic structures in plan view;

FIG. 4:

Schematic representation of the parallel arrangement of two inventive microfluidic structures in plan view;

FIGS. 5a to 5d:

Representation of the cross section of three inventive microfluidic structures;

FIG. 6:

Schematic representation of a microfluidic structure according to the invention in plan view with holding structures in the region of the holding positions in plan view;

FIG. 7:

Schematic representation of a microfluidic structure according to the invention in the region of a dead end channel in the plan view;

FIG. 8:

Schematic representation of a microfluidic structure according to the invention with a structure promoting the union of the liquid volumes in plan view.

FIG. 9:

Lab-on-a-chip / microfluidic system for performing a PCR reaction in plan view

In the figures, liquid interfaces of the liquid volumes 41, 42, 43, 141 are shown in the form of broken lines. In the embodiments with a figure in plan view, the lid film is not shown in each case. In these figures, only the base plate is shown with the contours of the channels and chambers. The flow direction of the fluids is indicated by black arrows.

In FIG. 1 three different embodiments of the inventive microfluidic structure 1 are shown schematically in plan view. The structures such as fluid chamber 2, inlet 3 and outlet lines 4 and feed openings 5 are formed in this case as groove-shaped recesses and / or recesses in a base plate 10 and by a cover sheet 11 (in the figures except FIGS. 5a to 5d not visible) closed. The cross sections are transverse to the indicated flow direction in Here shown embodiment, a rectangular shape, but there are also other cross-sectional shapes, such as. B. semicircles, possible.

In the first alternative embodiment of the microfluidic structure 1 according to the invention, in FIG. 1 left, an asymmetrically formed fluid chamber 2, in this embodiment in approximately circular segment-shaped, is shown. The feed opening 5 in the base plate and the holding position 6 for the second liquid volume 42 are located in the region of the widening of the fluid chamber 2 in the vicinity of or already in connection with the lateral wall surface 21 of the fluid chamber, away from the shortest flow path through the feed channel 3. Fluid chamber 2 and discharge channel 4, to prevent entrainment of the second chamber located in the fluid chamber 2 liquid volume 42 by a gas flow.

Due to the proximity of the addition opening 5 and / or the holding position 6 to the lateral wall surface 21 of the fluid chamber 2, the second liquid volume 42 can form a larger contact surface with the curved wall surface 21 of the fluid chamber 2 as a holding structure 7 and thus be held more reliably on the holding position 6.

In the second, middle embodiment in FIG. 1 a symmetrically shaped fluid chamber 2 is shown, the feed opening 5 is also below the fluid chamber 2 in the base plate 10, not in the region of the lateral wall surface 21 of the fluid chamber 2, but between a central flow line and the lateral wall surface 21 of the fluid chamber 2. The holding position 6 has in this case a holding structure 7 in the form of a recess 72 in the base plate 10.

In the third embodiment, right in FIG. 1 illustrated, another channel 31 opens via a narrowed formed addition port 5 into the fluid chamber 2. About this channel 31, a second liquid volume 42 is introduced into the fluid chamber 2. The channel 31 can be fed in this case via an operator device with the second liquid volume 42. Again, a holding structure 7 is provided in the form of a recess in the base plate in the region of the holding position 6.

In operation, in the inventive microfluidic structure 1, as in FIGS. 2a to 2c shown, first pretend by the addition of opening 5, a second fluid volume 42 on the holding position 6. Subsequently, a first liquid volume 41 is introduced into the fluid chamber 2 via the supply channel 3 and driven by a pressure difference in the direction of the discharge channel 4. During the pressure-driven passage of the first liquid volume 41 through the fluid chamber 2, the first liquid volume 41 is expanded to the full in this case due to the wettable surfaces fluid chamber cross-section and coalesced without gas inclusion with the already specified in the fluid chamber 2 second fluid volume 42. The combined fluid volume 41 + 42 finally arrives in the discharge channel 4.

In FIG. 3 a sequential sequence of two microfluidic structures 1, 1 'according to the invention is shown. In the fluid chamber 2 of the first microfluidic structure 1 according to the invention, a first liquid volume 41 has already been combined with a second liquid volume 42. Upon further conveying the combined liquid volumes 41 + 42 through the second microfluidic structure 1 'according to the invention, a third liquid volume 43 applied there to a holding position 6' is likewise taken up in the liquid volume.

In FIG. 4 shows a parallel arrangement of two inventive microfluidic structures 1 a, 1 b, wherein the two supply channels 3a, 3b are fed via a dividing channel 31. In this case, a first liquid volume 41 can each be combined with different second liquid volumes. In a microfluidic system with such a structure, the two combined liquid volumes can be further processed separately.

In the FIGS. 5a to 5d the microfluidic structure 1 according to the invention is shown in section, cut in each case at the level of the fluid chamber 2 with feed opening 5. The microfluidic structure 1 is formed by a base plate 10 with recesses introduced therein and a cover film 11.

In the FIG. 5a is in the base plate 10 below the fluid chamber 2, the addition port 5 is formed. In the region of the feed opening 5, the base plate 10 from the bottom Coming from a recess 51 on. In the region of the recess 51, a septum 52 is attached, so that after the second fluid volume is dispensed with a syringe through the septum 52 an automatically closing seal of the addition opening 5 is achieved, which is also resistant to larger pressures in the fluid chamber 2.

In FIG. 5b is an opening formed in the base plate 10 opening 5 via a sliding sealing element 53 to open and close again. The sealing element 53 is driven via an actuator in the operator device.

In FIG. 5c the feed opening 5 is formed via an opening 54 in the cover sheet 11. The opening 54 can also be generated in this case via a syringe tip in the task of the second fluid volume 42 into the fluid chamber 2. When elastic films are used as the cover film 11, an automatic closure of the opening 54 takes place after puncture. Adhesive structures 7 in the form of a plurality of short steles 71 are arranged in the base plate 10 in the region of the holding position 6 for the second liquid volume 42.

Also in FIG. 5d the feed opening 5 is formed via an opening 54 in the cover sheet 11. In the base plate 10, a holding structure 7 in the form of a recess 72 in the region of the holding position 6 for the second liquid volume 42 is attached.

In FIG. 6 In the region of the feed opening 5 for the second liquid volume 42 in the fluid chamber 2, two steles 73 extending from the base plate 10 to the cover film 11 are formed as holding structures 7 in the region of the holding position 6. In this case, a second fluid volume 42 introduced via the addition opening 5 is held between the lateral wall 21, bottom 22 and cover surfaces 23 of the fluid chamber 2 and the surfaces of the stems 73. Alternatively, other surface structures which increase the contact area between the second fluid volume 42 and the fluid chamber 2 can also be attached as holding structures 7 in the region of the holding position 6 for the second fluid volume 42.

In FIG. 7 a microfluidic structure 1 according to the invention is represented in the region of a dead-end channel 32 of a lab-on-a-chip. In operation, a first volume of liquid 41 driven by a pressure difference in a main channel 33. As soon as the first liquid volume 41 in the region of the intersection 34 has passed from the main 33 and the dead end channel 32, a pressure is built up in the main channel 33 in the flow direction in front of the first liquid volume 41, without lowering the pressure behind the first liquid volume 41 in the flow direction. Since a compressible fluid, for example a gas or air is enclosed in a large-volume reservoir 35 at the dead end of the dead-end channel 32, the first liquid volume 41 penetrates into the dead-end channel 32 and is further in through further coordinated increase of the two pressures in the main channel 33 in the dead end channel 32 is driven beyond the microfluidic structure 1 according to the invention, wherein a second liquid volume 42 held in a fluid chamber 2 in the dead end channel 32 is combined with the first liquid volume 41. By subsequent reduction of the pressures in the main channel 33, the combined liquid volume 41 + 42 is again driven out of the dead end channel 32 into the main channel 33 and further conveyed there.

In FIG. 8 an embodiment of the inventive microfluidic structure 1 is shown with a union of the liquid volumes supporting structure. In this case, in the region of the mouth of the supply channel 3 into the fluid chamber 2, the fluid chamber 2 has an indentation 24, projecting into the asymmetrically shaped fluid chamber 2, of the lateral wall surface 21 of the fluid chamber 2. By virtue of this structure 24, the first liquid volume 41 penetrating into the fluid chamber 2 is urged in the direction of the lateral wall surface 21 lying opposite the indentation 24, so that an expansion of the first liquid volume 41 over the full fluid chamber cross section is promoted by wetting all side surfaces 21 of the fluid chamber.

In FIG. 9 A lab-on-a-chip 100 for carrying out a PCR reaction is shown in plan view, which, inter alia, contains the inventive microfluidic structure 1 Q1, 102, 161, 171 several times and in different forms.

When operating the lab-on-a-chip 100, a lysed sample is introduced via an opening 110 in the lab-on-a-chip 100 by syringe pump (not shown) in the chip 100 and in a first inventive microfluidic structure 101 with a in of the Fluid chamber 105 stored liquid mixture 141 with contained therein reagents for reverse transcription / prePCR. In a meandering microfluidic channel 151 subsequently arranged in the flow direction, a complete mixing of the sample with the liquid mixture 141 takes place. The mixture formed is then conveyed into the PCR chamber 153 via a fluidic connection released through a rotary valve 152 (dashed circular line).

The correct positioning of the mixture exactly in the PCR chamber is monitored by light barriers 154, 157, depending on the degree of filling of the channels at the end of the PCR chamber 153, a light signal directly to a detector (not shown) arrive or totally reflect the light signal , The further delivery of the sample by syringe pump stops as soon as a signal change at the light barrier 154 is detected and thus the complete filling of the PCR chamber 153 is confirmed. Thereafter, the PCR chamber 153 is fluidically separated from the remaining channels in the chip 100 via the rotary valve 152, and the pre-amplification reaction takes place under cyclically proceeding temperature profiles. The heating takes place by means of heating jaws which are mounted in the operating device and which are in contact with the PCR chamber 153. Subsequently, a fluidic connection between the PCR chamber 153 and a further channel 155 on the chip with a further meandering, microfluidic channel is produced by the rotary valve 152 156 released to the mixture and another microfluidic structure according to the invention 102 for combining two fluid volumes. This microfluidic structure 102 according to the invention for combining two liquid volumes has at the discharge channel 104 an exit opening 111 sealed to the environment with a hydrophobic or non-wettable semipermeable membrane. At this opening 111, a negative pressure can be applied via an operator device (not part of the figure), which ensures a pressure-driven transport of the amplified sample solution into this structure 102. As soon as a liquid abuts the gas-permeable and liquid-impermeable membrane in the opening 111, transport is stopped by a measured increase in pressure. An oligonucleotide mixture 142 previously embedded in this microfluidic structure 102 according to the invention via an addition opening is combined with the amplified sample solution. In a further process step is at a second, located on the inlet channel 103 opening 112 to the environment, which also with a hydrophobic or non-wettable, semipermeable membrane is closed, over an operator device an overprint abandoned. The entire solution present in the microfluidic structure 102 is thus separated from a supernatant outside that in the microfluidic structure 102. The supernatant is passed through the overpressure and a corresponding circuit of the rotary valve 152 via a channel 158 in a waste channel on the Lab-on-a-chip (not shown here). The now measured in the microfluidic structure 102, now measured sample liquid is conveyed by an applied to the opening 111 at the discharge channel 104 overpressure and a corresponding circuit of the rotary valve 152 again in the PCR chamber 153. Also in this case, the correct filling of the PCR chamber 153 is detected and regulated via a light barrier 157. After renewed cyclic temperature runs in the PCR chamber 153, the amplified sample solution is combined via two further microfluidic structures 161, 171 according to the invention for combining two liquid volumes with the required dilution buffer solutions 162, 172 and via an outlet opening 180 from the lab-on-a-chip 100 in a detection device (not shown) on.

Because of the larger volumes of liquid to be combined in the first structure 161, the first microstructure structure 161 in the flow direction has holding structures 163 in the region of the holding position 164 for the first dilution buffer stored in the fluid chamber 167. The holding structures 163 are formed in this case by small indentations 165, 166 in the fluid chamber 167 at the beginning of the holding position 164. Furthermore, this first microfluidic structure 161 has a one-sided cross-sectional constriction 168 at the transition from the supply channel 169 to the fluid chamber 168, which supports a clamping of the sample solution when conveying into the fluid chamber 168.

The fluid chambers 107, 105, 167, 177 in this lab-on-a-chip 100 are asymmetrically shaped in the flow direction, with the addition openings 106, 108, 166, 176 and holding positions 164 in the area of the one-sided bulge of the fluid chambers 107, 105, 167 , 177, off the central flow line from the supply line 169, 103 to the discharge channel 104 through the fluid chamber 107, 105, 167, 177, are arranged.

The channels contained in the Lab-on-a-Chip 100 can, for example, via a rotary valve, as in the German application DE 102008002674.3 described, in different Be connected with each other, so that different flow paths can be switched. In this case, the openings of the channels to be connected to a chip surface of an overlying valve body (not shown, support surface is indicated by a broken circular line) sealed. The valve body has recesses adapted to fluidly interconnect various of the openings of the channels of the lab-on-a-chip.

LIST OF REFERENCE NUMBERS

1, 1 '1a, 1b, 101, 102, 161, 171

microfluidic structure

2, 2 ', 2a, 2b, 105, 167, 177, 107

fluid chamber

3, 3 ', 3a, 3b, 103, 169

supply channel

4, 4 ', 4a, 4b, 104

Waterway

5, 5 ', 5a, 5b, 106, 108, 176, 166

feed opening

6, 164

hold

7, 1B3

retaining structures

10

baseplate

11

cover film

29

lateral wall surface

22

floor area

23

cover surface

24, 165, 168

indentation

25

largest cross-sectional area of the fluid chamber

31, 155, 158

channel

32

dead-end channel

33

main channel

34

crossing

35

reservoir

41

first fluid volume

42, 42a, 42b

second liquid volume

43

third fluid volume

51

recess

52

septum

53

sliding sealing element

54

opening

71

short steles

72

deepening

73

steles

100

Lab-on-a-chip or microfluidic system

110, 111, 112

opening

121

Got over

141

Liquid mixture reverse transcription / pre-PCR

151, 156

meandering, microfluidic channel

152

rotary valve

153

PCR chamber

154, 157

photocell

162, 172

Diluent solutions

168

Cross-sectional narrowing

180

output port

B

largest width of the cross section of the fluid chamber in the flow direction

Claims (16)

1. Pressure-operable microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) for the bubble-free unification of two liquid volumes, with a fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) which has an administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) and in each case, issuing into the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177), a supply duct (3, 3', 3a, 3b, 103, 169) and a discharge duct (4, 4', 4a, 4b, 104), the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) having a holding position (6, 164) and being designed in such a way that a second liquid volume (42, 42a, 42b, 43, 141, 142, 162, 172) to be fed through the administering orifice (5, 5', 5a, 5b, 106, 108, 165, 176) into the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) can be held in the region of the holding position (6, 164), and, during the pressure-driven passage of the first liquid volume (41), the second liquid volume (42) being capable of being taken up by the latter and of being transferred as a unified liquid volume (41 + 42) through the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) into the discharge duct (4, 4', 4a, 4b, 104), characterized in that the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) has a fluid-chamber cross section widened in the throughflow direction from the supply duct (3, 3', 3a, 3b, 103, 169) to the discharge duct (4, 4', 4a, 4b, 104) in relation to the supply duct (3, 3', 3a, 3b, 103, 169), in such a way that the widening is shaped continuously from the supply duct to the largest fluid-chamber cross section, and in that the fluid chamber is set up, by the widened cross section, to widen an essentially pressure-driven first liquid volume (41), conducted through the supply duct (3, 3', 3a, 3b, 103, 169) and through the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177), to a cross section corresponding at least approximately to the full cross section of the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177).
2. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to Claim 1, characterized in that the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) has a maximum cross section widened by no more than 5 times, especially preferably by no more than 2.5 times with respect to the supply duct (3, 3', 3a, 3b, 103, 169).
3. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that at least the surfaces of the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) and of the supply duct (3, 3', 3a, 3b, 103, 169) are designed to be wettable.
4. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) and/or the holding position (6, 164) are/is arranged on the far side of a central flow line from the supply duct (3, 3', 3a, 3b, 103, 169) through the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) to the discharge duct (4, 4', 4a, 4b, 104).
5. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) is closable.
6. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to Claim 5, characterized in that the administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) is designed to be automatically closing, for example by the attachment of a septum (52) or an elastic cover film (11).
7. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the orifice width of the administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) is small, that is to say smaller than 1/20 and especially preferably smaller than 1/100, with respect to the maximum cross-sectional area of the fluid chamber.
8. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) has a plurality of administering orifices (5, 5', 5a, 5b, 106, 108, 166, 176).
9. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that a plurality of fluid chambers (2, 2', 2a, 2b, 105, 107, 167, 177) are arranged one behind the other.
10. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the holding position (6, 164) occupies only part of the fluid-chamber cross section.
11. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the holding position (6, 164) is provided with holding structures (7, 163), in such a way that the second liquid volume (42, 42a, 42b, 43, 141, 142, 162, 172) is held reliably as a result of the formation of a relatively large surface in the region of the holding position (6, 164) and/or the generation of relatively high adhesion in the region of the holding position (6, 164) by surface modification.
12. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the fluid chamber (2, 2', 2a, 2b, 105, 107, 167, 177) is widened on only one side in the flow direction and/or is shaped asymmetrically so as to form the holding position (6, 164) in the widening.
13. Microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, characterized in that the administering orifice (5, 5', 5a, 5b, 106, 108, 166, 176) can be opened and closed by means of an operator device.
14. Lab-on-a-Chip (100) with at least one microfluidic structure (1, 1', 1a, 1b, 101, 102, 161, 171) according to one of the preceding claims, the Lab-on-a-Chip (100) additionally having a plurality of further ducts, chambers and/or reservoirs.
15. Lab-on-a-Chip (100) according to Claim 14, characterized in that at least one chamber and/or reservoir has already been prefilled with chemicals during production.
16. Lab-on-a-Chip (100) according to Claim 14 or 15, characterized in that the Lab-on-a-Chip (100) has the microfluidic structures (1, 1', 1a, 1b, 101, 102, 161, 171) at least twice in an arrangement successive in the direction of flow of the fluids or else parallel.

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