EP2862630B1 - Leakage protection unit for a microfluidic device and corresponding microfluidic device - Google Patents

Description

State of the art

The present invention relates to a leakage protection unit for a microfluidic device and a microfluidic device.

Microfluidic lab-on-a-chip systems (LOC) are usually designed as disposable components and often consist of polymer layer systems in which microfluidic unit functions such as valves or pumps are integrated. Such functions can be mapped, for example, using two polymer substrates that are separated by a flexible polymer membrane. In this case, the polymer membrane can be deflected by pneumatic pressures in order to displace liquid within the lab-on-chip system or to close a channel. For this purpose, both positive and negative relative pressures are generated in an external control unit and passed on to the microfluidic system.

The US2007 / 0000613 discloses a microfluidic device with two elements, a recess, a passage opening and a channel which connects the recess with the passage opening.

The US200870008628 discloses a microfluidic device with a lower and an upper substrate, wherein a chamber is formed in the lower substrate and a channel is formed in the upper substrate.

The DE10 2010 028 524 A1 discloses a microfluidic component comprising a layer structure of a fluidic substrate, a control substrate and an elastic membrane arranged in between.

The WO 02/41994 A2 discloses a test device for performing chemical testing of a fluid. The testing device has a membrane which is arranged between an upper and a lower cavity and has a through opening.

Against this background, the present invention provides a leakage protection unit for a microfluidic device and a microfluidic device according to FIG presented to the main claims. Advantageous refinements result from the respective subclaims and the following description.

• ein Deckelelement;
• ein Bodenelement, in dem zumindest eine Bodenausnehmung als Fluidbehälter ausgebildet ist, wobei die Bodenausnehmung dem Deckelelement gegenüberliegend angeordnet ist;
• zumindest einen Druckkanal zum Anlegen eines Drucks, wobei der Druckkanal in dem Bodenelement und/oder dem Deckelelement ausgebildet ist; und
• zumindest einen Widerstandskanal, der zwischen dem Deckelelement und dem Bodenelement ausgebildet ist, um den Druckkanal und den Fluidbehälter fluidisch zu koppeln, wobei der Widerstandskanal einen fluidischen Widerstand für ein sich in dem Widerstandskanal befindliches Fluid darstellt.

A leakage protection unit for a microfluidic device is presented, the leakage protection unit having the following features:

• a lid member;
• a base element in which at least one base recess is designed as a fluid container, the base recess being arranged opposite the cover element;
• at least one pressure channel for applying a pressure, the pressure channel being formed in the base element and / or the cover element; and
• at least one resistance channel which is formed between the cover element and the base element in order to fluidically couple the pressure channel and the fluid container, the resistance channel representing a fluidic resistance for a fluid located in the resistance channel.

A microfluidic device can be understood to mean, for example, a device for processing, duplicating and / or analyzing a biochemical material such as nucleic acids, proteins and cells. A cover element and a base element can each be understood to mean a layer that is made, for example, from a plastic, in particular from a polymer. A bottom recess can be understood to mean, for example, a depression in the bottom element. The bottom recess can be designed as a fluid container and filled with a fluid. A fluid can be understood to mean, for example, a liquid containing the biochemical material. A fluidic resistance, also called flow resistance, can be understood as a damping characteristic of the resistance channel, by means of which a flow rate of a fluid located in the resistance channel is reduced. A fluid located in the microfluidic device, for example one or more liquids, can be retained by the fluidic resistance. For example, the resistance channel can be a represent fluidic resistance, by means of which the flow rate of the fluid is reduced by a factor of 50 to 150 or 75 to 125 compared to an embodiment without a resistance channel. The resistance channel can thus represent a fluidic resistance which is such that a flow rate of a fluid located in the resistance channel is reduced by a predetermined factor.

The approach described can be based on the use of a flow resistance for retaining liquids in the device, for example in the form of a chip.

The present approach is based on the knowledge that a lab-on-a-chip system can be connected to a pressure-generating control unit. Particularly in connection with negative relative pressures, there can be the risk that liquid from the lab-on-a-chip system will be drawn into the control unit and this will be contaminated. A channel between a liquid container of the lab-on-a-chip system and a pressure connection of the lab-on-a-chip system can advantageously be designed with such a high fluidic resistance that the liquid is prevented from flowing back in the direction of the pressure connection .

By means of the present approach, high costs, which can arise from a possible decontamination of the control unit by replacing components and downtimes, can be avoided. Furthermore, the present approach offers the advantage of high reliability, since no analyte can be distributed in the control unit in the event of a malfunction and thus the risk of incorrect results, in particular false positive results, can be reduced on a subsequent lab-on-a-chip system. Finally, the present approach can also reduce the risk of health hazards from escaping liquids.

According to one embodiment of the present approach, the pressure channel can be designed as a through opening in the base element and / or the cover element. Here, the bottom recess can also be arranged laterally offset to the through opening. This enables an inexpensive and efficient interface for initiating the pressure to be provided.

According to a further embodiment of the present approach, the fluidic resistance can be predetermined by a cross-sectional shape and / or a diameter and / or a length of the resistance channel. As a result, the fluidic resistance can be adapted very precisely to different conditions such as the type of fluid or the level of the pressure applied.

Furthermore, a film is arranged between the cover element and the base element. Here, the film has the resistance channel. A film can be understood to be a flat, flexible element such as a plastic layer. The film can for example be impermeable to fluid. With this embodiment, the resistance channel can be implemented particularly cost-effectively. Furthermore, the most varied geometries of the resistance channel can thereby be implemented with low manufacturing and cost expenditure.

The film closes the fluid container in a fluid-tight manner. This can prevent a fluid located in the fluid container from escaping. Furthermore, the film can be deflected, for example, by the pressure applied to the passage opening in order to control a fluid flow.

According to the invention, at least one cover recess is formed as a component of the resistance channel in the cover element in order to increase a volume of the resistance channel. A cover recess can be understood as a recess in the cover element. The cover recess can serve as a fluid buffer, in particular when a negative pressure is applied to the pressure channel, in order to collect a fluid sucked in through the resistance channel and thus prevent the fluid from leaking through the pressure channel.

In addition, in the area of the cover recess and / or the cover recess, the film has at least one resistance element and / or a hydrophobic layer in order to increase the fluidic resistance. Under a resistance element, for example, a transverse to Resistance channel arranged groove or edge are understood. Under one hydrophobic layer can be understood, for example, as a wax or paraffin layer. By means of this embodiment, filling of the cover recess with the fluid can be delayed in a controlled manner.

Furthermore, the cover recess can have an indicator material for identifying a liquid. An indicator material can be understood to mean a material that experiences a change of state on contact with a liquid. For example, the indicator material can discolour. This enables an early and reliable detection of leaks in a microfluidic system.

At least one pressure diversion channel with a first channel opening and a second channel opening can be formed in the cover element. Here, the first channel opening can be arranged opposite the fluid container and the second channel opening can be fluidically coupled and / or can be coupled to the resistance channel. This allows pressure to be exerted on the film in a controlled manner in order to deflect the film. In this way, for example, a valve and / or pump mechanism can be implemented.

In addition, at least a partial section of the resistance channel can have a liquid-absorbing material which is designed to close the resistance channel in a liquid-tight manner when a liquid is absorbed. The liquid-absorbing material can be, for example, a fibrous material that increases in size when the liquid is absorbed in such a way that the resistance channel is closed in a liquid-tight manner. This can further increase the reliability of the leakage protection unit.

The liquid-absorbing material can be arranged between the cover recess and the pressure channel. This can prevent the fluid from leaking through the pressure channel if the cover recess overflows.

According to a further embodiment of the present approach, a sealing membrane can be formed between the resistance channel and the pressure channel in order to close the pressure channel in a liquid-tight manner. A flat flexible element such as for example a plastic layer can be understood. The sealing membrane can, for example, be gas-permeable but liquid-impermeable. As a result, the reliability of the leakage protection unit can be ensured independently of the fluidic resistance of the resistance channel or a volume of the cover recess.

• einer Auslaufschutzeinheit gemäß einer der vorangehend beschriebenen Ausführungsformen; und
• einem Mittel zum Anlegen des Drucks am Druckkanal der Auslaufschutzeinheit.

The present approach also creates a microfluidic device with the following features:

• a leakage protection unit according to one of the embodiments described above; and
• a means for applying the pressure to the pressure channel of the leakage protection unit.

A means for applying the pressure can be understood to mean, for example, a pump which is designed to generate an overpressure and / or underpressure in the pressure channel.

Furthermore, the present approach creates a method for operating a leakage protection unit according to one of the embodiments described above, the method comprising the following steps:
Applying the pressure to the pressure channel in order to control a fluid flow of a fluid located in the fluid container.

For example, the fluid flow can be controlled very efficiently if, in the application step, a pressure which alternates at certain time intervals is applied to the pressure channel.

• Bereitstellen eines Deckelelements und eines Bodenelements, in dem zumindest eine Bodenausnehmung als Fluidbehälter ausgebildet ist, wobei in dem Bodenelement und/oder dem Deckelelement zumindest ein Druckkanal zum Anlegen eines Drucks ausgebildet ist;
• Zusammenfügen des Deckelelements und des Bodenelements, wobei das Zusammenfügen derart erfolgt, dass die Bodenausnehmung dem Deckelelement gegenüberliegt; und
• Bilden zumindest eines Widerstandskanals zwischen dem Deckelelement und dem Bodenelement, um den Druckkanal und den Fluidbehälter fluidisch zu koppeln, wobei der Widerstandskanal einen fluidischen Widerstand für ein sich in dem Widerstandskanal befindliches Fluid repräsentiert.

Finally, the present approach creates a method for producing a leakage protection unit according to one of the embodiments described above, the method comprising the following steps:

• Providing a cover element and a base element, in which at least one base recess is designed as a fluid container, wherein in the The base element and / or the cover element has at least one pressure channel for applying a pressure;
• Joining the cover element and the base element together, the joining taking place such that the base recess is opposite the cover element; and
• Forming at least one resistance channel between the cover element and the base element in order to fluidically couple the pressure channel and the fluid container, wherein the resistance channel represents a fluidic resistance for a fluid located in the resistance channel.

Fig. 1

eine schematische Darstellung einer Auslaufschutzeinheit;

Fig. 2

eine schematische Darstellung einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 3

eine schematische Darstellung einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 4

eine schematische Darstellung einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 5

eine schematische Darstellung einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 6

eine schematische Darstellung einer mikrofluidischen Vorrichtung gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 7

ein Ablaufdiagramm eines Verfahrens zum Betreiben einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung; und

Fig. 8

ein Ablaufdiagramm eines Verfahrens zum Herstellen einer Auslaufschutzeinheit gemäß einem Ausführungsbeispiel der vorliegenden Erfindung.

The invention is explained in more detail below with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of a leakage protection unit;

Fig. 2

a schematic representation of a leakage protection unit according to an embodiment of the present invention;

Fig. 3

a schematic representation of a leakage protection unit according to an embodiment of the present invention;

Fig. 4

a schematic representation of a leakage protection unit according to an embodiment of the present invention;

Fig. 5

a schematic representation of a leakage protection unit according to an embodiment of the present invention;

Fig. 6

a schematic representation of a microfluidic device according to an embodiment of the present invention;

Fig. 7

a flowchart of a method for operating a leakage protection unit according to an embodiment of the present invention; and

Fig. 8

a flow chart of a method for producing a leakage protection unit according to an embodiment of the present invention.

In the following description of advantageous exemplary embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, a repeated description of these elements being dispensed with.

Fig. 1 shows a schematic representation of a leakage protection unit 100. The leakage protection unit 100 has a cover element 105 and a base element 110. In the cover element 105, a pressure channel 115 for applying pressure is formed. A base recess 120 is formed in the base element 110 as a fluid container 125. The bottom recess 120 is arranged opposite the cover element 105. A resistance channel 130 is formed between the cover element 105 and the base element 110 in order to fluidically couple the pressure channel 115 and the fluid container 125. Here, the resistance channel 130 represents a fluidic resistance which is such that a flow rate of a fluid located in the resistance channel 130 is reduced by a predetermined factor and leakage of the fluid via the pressure channel 115 is prevented. The channel 130 can be recessed in either layer 105 or layer 110.

According to this exemplary embodiment, the pressure channel 115 is designed as a through opening in the cover element 105. Here, the bottom recess 120 is also arranged laterally offset to the through opening.

According to one embodiment, the fluid container 125 is connected to a fluidic network into the plane of the drawing, that is to say, for example, transversely to a direction of longitudinal extent of the channel 130. The container 125 can be filled and emptied during regular operation of the device according to the invention through the fluidic network.

Fig. 2 shows a schematic representation of a leakage protection unit 100 according to an embodiment of the present invention. In contrast to Fig. 1 indicates the in Fig. 2 The leakage protection unit 100 shown also has a film 200 which is arranged between the cover element 105 and the base element 110. Here, the resistance channel 130 is formed in the film 200. Furthermore, the fluid container 125 is closed in a fluid-tight manner by the film 200. Furthermore, the cover element 105 has a cover recess 205 as a component of the resistance channel 130. The cover recess 205 is fluidically coupled to the pressure channel 115 via a cover recess channel 210 formed in the cover element 105 as a further component of the resistance channel 130.

The cover recess 205 is designed, in particular when a negative pressure is applied to the pressure channel 115, to collect a fluid sucked in via the resistance channel 130 and thus to prevent the fluid from escaping through the pressure channel 115.

Furthermore, the cover element 105 comprises a pressure diversion channel 215 with a first channel opening 220 and a second channel opening 225. Here, the first channel opening 220 is arranged opposite the fluid container 125 and the second channel opening 225 is fluidically coupled to the resistance channel 130.

In Fig. 2 the pressure diversion channel 215 comprises, for example, two sections arranged perpendicular to the floor element 110 and a connecting section arranged along the floor element 110 for connecting the vertical sections. In this case, a first vertical section has the first channel opening 220 and a second vertical section has the second channel opening 225. The connecting section is formed, for example, in the area of a surface of the cover element 105 facing away from the base element 110 and is closed in a fluid-tight manner by a membrane applied to the cover element 105.

The pressure diversion channel 215 is designed to guide the pressure applied to the pressure channel 115 onto the film 200 in the area of the fluid container 125, so that the film 200 is deflected. Is it like in Fig. 2 by an overpressure, the film 200 is arched in the direction of the fluid container 125.

According to a further exemplary embodiment of the present invention, the leakage protection unit 100 comprises a first polymer substrate as a cover element 105, a second polymer substrate as a bottom element 110 and an intermediate flexible polymer membrane as a film 200. Channels and cavities are formed within the polymer substrates 105, 110, like a fluidic access 115 , also called pressure channel 115, and a cavity 205, also called cover recess 205. This is connected to a microfluidic channel 130, which is designed as a resistance channel within the polymer membrane 200 and ends above the polymer membrane 200 via a channel section 215, also called pressure diversion channel 215. At this point there is another cavity as a fluid container 125 below the polymer membrane 200. The fluid container 125 is part of a membrane pump, for example. However, a membrane valve or another microfluidic function that uses a deflection of the polymer membrane 200 can also be located at this point. The channel section 215 is covered, for example, by a further polymer layer 220, for example an adhesive film.

The resistance channel 130 is designed, for example, in the form of a rectangular channel with dimensions of 50 μm by 18 μm by 26 mm. For example, this results in a flow rate of approx. 2.1 µl per second for air at a differential pressure of 20 kPa. Under the same environmental conditions, the flow rate for water is approx. 0.028 µl per second. For a switchover time of, for example, 100 seconds between the positive and negative pressure phase, a volume of the cavity 205 of 2.8 μl is therefore sufficient to prevent the liquid from leaving the system.

For higher switching frequencies, the volume of the cavity 205 can also be formed only through the channel to the pneumatic interface 115. The pneumatic interface 115 can also be referred to as a pressure channel 115.

Fig. 3 shows a schematic representation of a leakage protection unit 100 according to an embodiment of the present invention. In contrast to Fig. 2 indicates the in Fig. 3 The leakage protection unit 100 shown has a further floor recess 300. The further base recess 300 is arranged opposite the cover recess channel 210, so that the further base recess 300 forms an extension of the cover recess channel 210. A liquid-absorbing material 305 is introduced into the further bottom recess 300, which material is designed to close the cover recess channel 210 in a liquid-tight manner when a liquid emerging from the cover recess 205 is absorbed.

Another exemplary embodiment of the present invention provides that a material 305 is incorporated in front of the pneumatic interface 115 which does not impede the flow of gases. If the material 305 comes into contact with liquids, strong swelling leads to the closure of the cover recess channel 210.

This embodiment has the particular advantage that an additional safety mechanism prevents liquids from escaping. This increases the reliability of the leakage protection.

Fig. 4 shows a schematic representation of a leakage protection unit 100 according to an embodiment of the present invention. In contrast to those described above Figures 1 to 3 is the pressure channel 115 in the in Fig. 4 The leakage protection unit 100 shown is not formed in the cover element 105, but in the base element 110. Furthermore, the leakage protection unit 100 comprises a sealing membrane 400, which is arranged in a region of the base element 110 between the pressure channel 115 and the cover recess channel 210. The sealing membrane 400 is designed to fluidically separate the pressure channel 115 and the cover recess channel 210.

According to a further exemplary embodiment of the present invention, the leakage protection unit 100 in front of the pneumatic interface 115 contains, as a sealing membrane 400, a membrane which is permeable to gases but blocks liquids. This increases the reliability of the leakage protection.

Fig. 5 shows a schematic representation of a leakage protection unit 100 according to an embodiment of the present invention. In contrast to the in Fig. 2 The leakage protection unit 100 shown is the cover recess 205 in FIG Fig. 5 equipped with resistance elements 500 in order to increase the fluidic resistance of the resistance channel 130 in the region of the cover recess 205. The resistance elements 500 are in Fig. 5 on the one hand as elevations on a wall area of the cover recess 205 opposite the base element 110, on the other hand as recesses in a subsection of the film 200 opposite the cover recess 205. Here, the recesses are each arranged laterally offset from the elevations.

This results in a structure that functions as a capillary stop and counteracts excessive filling of the cover recess 205 with the fluid.

According to a further exemplary embodiment of the present invention, structures within the polymer membrane 200 and / or structures on the upper side of the cavity 205 are formed within the cavity 205. The structures are characterized by edges at which a progressing liquid meniscus experiences resistance due to capillary forces. This is also known as a capillary stop. Alternatively, a hydrophobic surface coating is also introduced within the cavity 205, such as, for example, surfaces treated with plasma, fluorinated surfaces, polytetrafluoroethylene (PTFE), wax or paraffin coatings. Both approaches lead to the fact that filling the cavity 205 is made more difficult. This also increases the leakage protection.

According to further exemplary embodiments of the present invention, combinations of swelling material 305, liquid-impermeable membrane 400 or capillary stop are also possible.

According to a further exemplary embodiment, a moisture indicator, for example indicator powder, which changes its color when it comes into contact with liquid, is stored in a leakage protection unit 100 within the cavity 205. In this way, an error, for example by a user or by an optical evaluation, can be detected within an external control unit and that The result of the last test will be marked as invalid. In this case it is particularly advantageous if some or all of the polymer layers 105, 110 are transparent.

Fig. 6 shows a schematic representation of a microfluidic device 600 according to an embodiment of the present invention. The microfluidic device 600 has a leakage protection unit 100 and a means 605 for applying the pressure to the pressure channel of the leakage protection unit 100. For this purpose, the means 605 is fluidically connected to the pressure channel. The microfluidic device 600 is implemented, for example, as a pressure-driven microfluidic polymer layer system to which an external control unit is connected as means 605.

One embodiment of the present invention includes a channel-shaped structure with high fluidic resistance, which is implemented on a lab-on-a-chip system as a microfluidic device 600 and is located between pneumatic interfaces to an external control unit, also called means 605, and one to controlling microfluidic function is located. A geometry of the channel-shaped structure can be used to set a pressure rising flank and thereby represents a functional extension of the lab-on-a-chip system. This exploits the fact that the fluidic resistance of the same structure for a liquid is higher by orders of magnitude due to its viscosity , for example by a factor of 100. In the event of a fault, this means that with typical differential pressures of a few 100 mbar to several bar, only a very small amount of liquid can escape through the channel-shaped structure in the direction of the pneumatic interface. If a cavity, for example in the form of the cover recess, is created between the channel-shaped structure and the pneumatic interface, a volume of the cavity, together with the fluidic resistance of the channel-shaped structure, can be designed in such a way that the process takes from minutes to a few hours Lab-on-a-chip system, even in the worst case scenario, it is impossible for the liquid to reach the pneumatic interface and contaminate the external control unit.

Advantageously, costs for complex repairs and downtimes of the external control unit can thereby be avoided.

Since it is ensured that no liquids escape from the lab-on-a-chip system, there is also no health risk for operating personnel due to contamination of the control unit.

Furthermore, a detection of an error is made possible, for example by looking at the cavity, by reading out electrical signals such as a change in electrical resistance or a change in electrical capacitance, and by placing a dry indicator powder in the intermediate cavity, which changes color when it comes into contact with liquid.

The structures required for the present invention can be produced using the same production techniques as the remaining components of the lab-on-a-chip system. The costs of a lab-on-a-chip system with corresponding structures are therefore only increased slightly.

Fig. 7 shows a flowchart of a method 700 for operating a leakage protection unit 100 according to an embodiment of the present invention. Here, in a step 705, a pressure is applied to the pressure channel in order to control a fluid flow of a fluid located in the fluid container.

According to an exemplary embodiment of the present invention, during operation the pneumatic pressure at the access 115 is typically switched periodically between positive and negative pressure in order to deflect or press the polymer membrane 200 above the cavity 120. It is often desirable here not to let this process run suddenly, but rather with a delay. For this purpose, the fluidic resistance of the channel 130 can be designed in such a way that it acts as a throttle for gases. In the event that the polymer membrane 200 ruptures within the cavity 120, also called the base recess 120, liquid can be sucked from the cavity 120 into the channel section 215 and the channel 130 during the suction phase. With the same cross section and length of the channel 130, the fluidic resistance increases, for example in the case of water, by a factor of approximately 100, whereupon the flow rate in the direction of the pneumatic interface 115 is increased by approximately the same factor is decreased. The volume of the cavity 205 can now be designed in such a way that the liquid front does not penetrate as far as the pneumatic interface 115 during the suction phase and thus cannot reach the external control unit either.

Fig. 8 FIG. 8 shows a flow chart of a method 800 for producing a leakage protection unit 100 according to an exemplary embodiment of the present invention. First, there is a step 805 of providing a cover element and a base element, in which at least one base recess is designed as a fluid container. Here, at least one pressure channel for applying a pressure is formed in the base element and / or the cover element. In a further step 810, the cover element and the base element are joined together. The joining takes place here in such a way that the bottom recess is opposite the cover element. Finally, in a step 815, at least one resistance channel is formed between the cover element and the base element in order to fluidically couple the pressure channel and the fluid container. Here, the resistance channel represents a fluidic resistance which is such that a flow rate of a fluid located in the resistance channel is reduced by a predetermined factor.

Thermoplastics such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), cyclo-polefin polymer (COP) or cyclo-polefin copolymer (COC) can be used as material examples for the polymer substrate.

As material examples for the polymer membrane, elastomer, thermoplastic elastomer, thermoplastic or hot-melt adhesive films can be used.

For the material 305, for example, materials can be used which increase their volume on contact with liquids, such as superabsorbents.

As the sealing membrane 400, membranes can be used which are permeable to gases but impermeable to liquids, such as PTFE membranes, also known under the name Gore-Tex.

As exemplary dimensions of the exemplary embodiments, the thickness of the polymer substrates 0.1 to 10 mm, the channel diameter in the polymer substrates 200 μm to 3 mm, the thickness of the polymer membrane 5 to 500 μm, the volume of the cavities 125, 205 1 μl to 10 ml and the lateral dimensions of the entire exemplary embodiment are 10 by 10 mm ² to 200 by 200 mm ² .

If an exemplary embodiment comprises a “and / or” link between a first feature and a second feature, this is to be read in such a way that the exemplary embodiment according to one embodiment includes both the first feature and the second feature and according to a further embodiment either only the has the first feature or only the second feature.

Claims (8)

1. Leakage protection unit (100) for a microfluidic device (600), wherein the leakage protection unit (100) has the following features:

   a cover element (105);

   a base element (110), in which at least one base recess (120) is formed as a fluid container (125), wherein the base recess (120) is arranged so as to be situated opposite the cover element (105);

   a film (200), which is arranged between the cover element (105) and the base element (110) and which closes off the fluid container (125) in a fluidtight manner;

   at least one pressure channel (115) for application of a pneumatic pressure for deflecting and exerting pressure on the film (200), which pneumatic pressure is periodically switched between a positive pressure and a negative pressure, wherein the pressure channel (115) is formed in the base element (110) and/or the cover element (105); and

   at least one resistance channel (130), which is formed between the cover element (105) and the base element (110) so as to fluidically couple the pressure channel (115) and the film (200), wherein the resistance channel (130) provides a fluidic resistance for a fluid situated in the resistance channel (130);

   characterized in that the film (200) has the resistance channel (130), and at least one cover recess (205) is formed as a component of the resistance channel (130) in the cover element (105) so as to increase a volume of the resistance channel (130), wherein a volume of the cover recess (205) amounts to 1 µl to 10 ml and is configured such that, in the event of the film (200) tearing, a liquid front, within the intake phase, does not advance as far as the pressure channel (115), and wherein the film (200), in the region of the cover recess (205), and/or the cover recess (205) have/has resistance elements (500) for forming a structure functioning as a capillary stop, and/or have/has a hydrophobic layer, so as to increase the fluidic resistance, wherein the fluidic resistance acts as a throttle for gases.
2. Leakage protection unit (100) according to Claim 1, characterized in that the pressure channel (115) is formed as a passage opening in the base element (110) and/or the cover element (105), wherein the base recess (120) is furthermore arranged laterally offset from the passage opening.
3. Leakage protection unit (100) according to either of the preceding claims, characterized in that the fluidic resistance is predefined by a cross-sectional shape and/or a diameter and/or a length of the resistance channel (130).
4. Leakage protection unit (100) according to one of the preceding claims, characterized in that at least one pressure bypass channel (215) with a first channel opening (220) and with a second channel opening (225) is formed in the cover element (105), wherein the first channel opening (220) is arranged so as to be situated opposite the fluid container (125), and the second channel opening (225) is fluidically coupled and/or able to be coupled to the resistance channel (130).
5. Leakage protection unit (100) according to one of the preceding claims, characterized in that at least one sub-portion of the resistance channel (130) has a liquid-absorbing material (305), which is designed to close off the resistance channel (130) in a liquid-tight manner upon absorption of a liquid.
6. Leakage protection unit (100) according to Claim 5, characterized in that the liquid-absorbing material (305) is arranged between the cover recess (205) and the pressure channel (115).
7. Leakage protection unit (100) according to one of the preceding claims, characterized in that a closure diaphragm (400) is formed between the resistance channel (130) and the pressure channel (115) so as to close off the pressure channel (115) in a liquid-tight manner.
8. Microfluidic device (600) having the following features:

   a leakage protection unit (100) according to one of the preceding claims; and

   a means (605) for applying the pressure to the pressure channel (115) of the leakage protection unit (100).

Images