Microfluidic device with rectifier function

Abstract

The present invention relates to a microfluidic device comprising a rectifier unit having a substrate, a valve arrangement formed in the substrate, and a fluid channel arrangement formed in the substrate having a first inlet opening, a second inlet opening, a first rectifier opening and a second rectifier opening.The valve arrangement can be brought from a first state into a second state, wherein in the first state a liquid can be conveyed from the first inlet opening to the first rectifier opening and from the second rectifier opening to the second inlet opening, and wherein in the second state the liquid can be conveyed from the second inlet opening to the first rectifier opening and from the second rectifier opening to the first inlet opening, wherein the valve arrangement comprises four valves, one of which is an umbrella valve in which a through hole is formed under the umbrella of the umbrella valve, which through hole is covered by the umbrella when the valve is in a blocked state. The present invention further relates to an associated method.

Description

[0001] The present invention relates to a microfluidic device for rectifying a liquid flow, a system comprising the microfluidic device, and an associated method.

[0002] In a variety of microbiological applications, liquids are passed through a microfluidic system to study biofilms and cell aggregates, or to investigate the behavior of cells under continuous flow conditions. For this purpose, the cells can be contained in a reservoir on a chip or in a substrate, and the substrate is connected to the microfluidic system, which is used to pass the fluid through the reservoir. This setup is used, for example, in arteriosclerosis research in connection with the adhesion behavior of cells, or in the simulation of organ models, where physiological conditions such as those found in an organ (e.g., the intestine) are imitated on a microfluidic chip. A substrate or chip with such a reservoir can be placed in an incubator and cultivated there.Of particular importance in these investigations and simulations is that a continuous, unidirectional flow of the fluid is achieved, for which purpose, for example, the valve arrangement of EP 1 944 084 A1 was developed.

[0003] The cells can also be continuously observed under a microscope. For this, all components—the substrate with the cells and the microfluidic system—must be incubated to create controlled and stable environmental conditions. This has so far only been possible with large or separate incubators for the individual components. A disadvantage of separate components is that tubing connections between the microfluidic system and the substrate are routed through an intermediate area at room temperature, and a temperature gradient can lead to bubbles forming in the tubing. Further disadvantages of this type of setup are the complexity of the system and the high dead volume created by the tubing connections.

[0004] Bubbles can form in the microfluidic system, for example, at sharp edges and can become trapped in the valve area. Such bubbles are detrimental to the described studies because, by interrupting the fluid flow, they can lead to unphysiological cultivation conditions and thus distort the study. A microfluidic device that suppresses the fixation of bubbles in the valve area would be desirable.

[0005] It is therefore an object of the present invention to provide a microfluidic device with a rectifying function and a method for generating a unidirectional flow, which allow a compact construction of a cell examination device and suppress bubble formation during the transport of a liquid through a microfluidic device.

[0006] This object is achieved by the microfluidic device according to claim 1 and the method according to claim 17. Further aspects can be found in the respective subclaims.

[0007] According to the invention, a microfluidic device is provided, comprising a rectifier unit. The rectifier unit comprises a substrate, a valve arrangement formed in the substrate, and a fluid channel arrangement formed in the substrate. The fluid channel arrangement comprises a first inlet opening and a second inlet opening, a first rectifier opening and a second rectifier opening, and a channel system, wherein the channel system fluidically connects the first inlet opening to the first rectifier opening via the valve arrangement and fluidically connects the second inlet opening to the second rectifier opening via the valve arrangement, or wherein the channel system fluidically connects the first inlet opening to the second rectifier opening via the valve arrangement and fluidically connects the second inlet opening to the first rectifier opening via the valve arrangement.wherein the valve arrangement can be brought from a first state into a second state, wherein in the first state a liquid can be conveyed from the first inlet opening to the first rectifier opening and from the second rectifier opening to the second inlet opening, and wherein in the second state the liquid can be conveyed from the second inlet opening to the first rectifier opening and from the second rectifier opening to the first inlet opening, wherein the valve arrangement comprises four valves, one of which is an umbrella valve, in which a through hole is formed under the umbrella of the umbrella valve, which through hole is covered by the umbrella in a blocking state.

[0008] The formation of the rectifier unit comprising the fluid channel arrangement and the valve arrangement in a single substrate represents a compact design of the microfluidic device, allowing the microfluidic device to be flexibly combined with other components. Furthermore, an umbrella valve with the through hole located below the umbrella has the property of suppressing the detrimental fixation of bubbles compared to other valve types, such as a check valve with a conical seat and a ball.

[0009] The first inlet and the second inlet serve to supply and discharge fluid to the rectifier unit. The flow direction at the two rectifier inlets is independent of whether the fluid is supplied through the first inlet or the second inlet. The fluid is guided in the fluid channel arrangement such that it always flows from the fluid supply point (first or second inlet) to the first rectifier inlet. From the second rectifier inlet, the fluid then flows to the other inlet, which is not used for fluid input.

[0010] Overall, the rectifier unit is able to provide a unidirectional flow between the two rectifier ports.

[0011] The channel system formed in the substrate serves to connect the ports of the microfluidic device as mentioned above (first and second input ports, first and second rectifier ports). The channel system can comprise one channel or a plurality of channels, as long as the stated purpose is fulfilled. A channel refers, in particular, to a cavity formed in the substrate.

[0012] An umbrella valve comprises a flexible or elastic umbrella that covers the through-hole located beneath the umbrella. Fluid can flow through this through-hole. When fluid flows through the through-hole and hits the side of the umbrella facing the through-hole, the fluid pressure causes the umbrella to open, allowing the fluid to flow past the umbrella valve. The umbrella valve is in an open state, and flow is therefore not blocked. When fluid flows from a side of the umbrella facing away from the through-hole toward the through-hole, the fluid pressure causes the umbrella to be pressed onto the through-hole, sealing the through-hole in a fluid-tight manner. The umbrella valve is in a blocked state, and fluid flow through the valve is blocked.

[0013] The umbrella valve, in particular the umbrella, may comprise an elastomer material, for example silicone, liquid silicone rubber, fluorosilicone, nitrile rubber or neoprene.

[0014] All valves in the valve arrangement can be passive valves, particularly passive check valves, which are opened and closed solely by the pressure of the fluid flowing in the fluid channel arrangement. An umbrella valve is a passive check valve. If all valves are passive valves, the valve arrangement is self-controlled, i.e., can be brought from the first state to the second state and vice versa, solely by the pressure of the flowing fluid.

[0015] One, several, or all of the aforementioned ports may further have a corresponding connector. The connector(s) at the respective channel end may conform to the Luer standard, with the connectors preferably having a female Luer or Luerlock adapter. Using connectors that conform to the Luer standard allows for easy, fluid-tight connection. Furthermore, the microfluidic device is compatible with numerous devices.

[0016] The channel system can be formed in a first plane and a second plane, wherein the first plane is formed parallel to the second plane, and wherein the first plane and the second plane are fluidically connected to one another by at least one of the valves of the valve arrangement. The first plane and the second plane can also be parallel to a bottom and / or a top side of the substrate. Additionally, it is conceivable that the first plane and the second plane are fluidically connected to one another by one or more through-holes through the substrate.

[0017] The use of two parallel planes allows for a more compact design of the channel system, especially in conjunction with one or more umbrella valves. Since the umbrella valve fluidically connects the two planes, the umbrella valve's shield lies in the plane of the channels. This requires a lower substrate height compared to, for example, if the shield is arranged perpendicular to the plane of the channels.

[0018] Each of the valves in the valve assembly can be an umbrella valve.

[0019] As discussed above, an umbrella valve can reduce bubble fixation. Therefore, it is particularly advantageous to use umbrella valves exclusively because they further suppress the blockage of fluid flow by bubbles.

[0020] Two of the valves may be configured to block flow from the first level to the second level and the other two of the umbrella valves may be configured to block flow from the second level to the first level.

[0021] This valve arrangement represents a simple way to implement a fluid channel arrangement with a valve arrangement that achieves the desired rectifying function. However, this need not be the only possible configuration. One advantage of umbrella valves is that by changing the flow direction (from the first level to the second level or vice versa), the function of the microfluidic device can also be easily changed or adapted.

[0022] Exactly two, three, four, or five through holes can be arranged under the umbrella of the umbrella valve or each of the umbrella valves, the cross-section of which corresponds, in particular, to a circular ring segment with rounded corners. Such a cross-sectional shape is also referred to below as "kidney-shaped."

[0023] Tests have shown that small through-holes lead to increased bubble fixation. Therefore, no more than five individual through-holes should be provided for each umbrella valve to effectively suppress bubble fixation. Furthermore, it is advantageous if the through-holes together account for as large an area as possible under the umbrella. For this purpose, the through-holes can have a cross-sectional shape corresponding to a circular ring segment with rounded corners. The rounded corners reduce the risk of bubble formation on sharp edges. The cross-section is considered to be the area of the through-holes that is perpendicular to the direction of flow of the liquid through the through-holes.

[0024] In the described microfluidic device, the length of a section of the channel system connecting the first input port to the first rectifier port may be identical to the length of a section of the channel system connecting the second input port to the second rectifier port, and / or the length of a section of the channel system connecting the first input port to the second rectifier port may be identical to the length of a section of the channel system connecting the second input port to the first rectifier port.

[0025] In the described microfluidic device, the cross-sectional area of a portion of the channel system connecting the first input port to the first rectifier port may be identical to the cross-sectional area of a portion of the channel system connecting the second input port to the second rectifier port, and / or the cross-sectional area of a portion of the channel system connecting the first input port to the second rectifier port may be identical to the cross-sectional area of a portion of the channel system connecting the second input port to the first rectifier port.

[0026] A channel system in which the described channel sections are of equal length and have the same cross-sectional area possesses a higher degree of symmetry. For example, the distance between the first inlet opening and the first rectifier opening is just as long as that between the second inlet opening and the first rectifier opening. This means that regardless of which inlet opening the liquid is fed to, any external influences have the same effect and the liquid exiting at the first rectifier opening always has the same properties. If a flow chamber is connected to the rectifier openings, a liquid with constant properties (e.g. temperature, gas concentration, etc.) flows through the flow chamber, regardless of which inlet opening the liquid is fed to.There can also be no runtime differences between the two different switching states of the microfluidic system, which can each lead to a different volume transport.

[0027] The microfluidic device may further comprise a supply unit having a first liquid reservoir and a second liquid reservoir, wherein the first inlet opening is fluidically connected to the first liquid reservoir and the second inlet opening is fluidically connected to the second liquid reservoir.

[0028] In this case, the two fluid reservoirs serve to supply fluid to be passed through the microfluidic device. If the supply unit is integrated into the microfluidic device, no external fluid supply is required, and the microfluidic device can be operated as a closed system. This also effectively prevents any external contamination of the fluid.

[0029] Another advantage of this microfluidic device is that unidirectional flow is achieved by pumping the liquid back and forth between the first liquid reservoir and the second liquid reservoir. Therefore, a small amount of liquid is required and no liquid is wasted. This is advantageous compared to the case where the liquid is always supplied at the same inlet port, which requires large quantities of liquid to be stored depending on the operating mode and duration.

[0030] The first liquid reservoir and / or the second liquid reservoir can be formed on or in the substrate of the rectifier unit. This results in a particularly compact design of the microfluidic device. Furthermore, the connections between the first liquid reservoir and the first inlet opening, as well as between the second liquid reservoir and the second inlet opening, can be formed at least partially in the form of a channel in the substrate. This aspect has the advantage that no hose connections are required and the transport paths of the liquid can be shortened. As a result, the liquid is less likely to be exposed to a temperature gradient, which reduces the risk of bubble formation in the liquid, and the volume of liquid required for perfusion in the microfluidic device is reduced.Alternatively, the two fluid reservoirs can be formed on or in a separate supply substrate. This allows for greater flexibility in the configuration of the microfluidic device, making it more flexible to use.

[0031] The first liquid reservoir and / or the second liquid reservoir may further comprise a line leading from the outside into the interior of the respective liquid reservoir, wherein the line is led in particular through a cover or through a side wall of the respective liquid reservoir.

[0032] The purpose of this type of liquid reservoir design is to allow gas to be introduced into the liquid from the outside, provided the line extends into the liquid in the liquid reservoir. This allows the content of a specific gas in the liquid (e.g., oxygen) to be efficiently adjusted. A specific design for this is explained below.

[0033] The microfluidic device may further comprise a flow chamber, wherein the flow chamber comprises an inlet and an outlet, and wherein the inlet of the flow chamber is fluidically connected to the first rectifier orifice and the outlet of the flow chamber is fluidically connected to the second rectifier orifice.

[0034] According to the described device, the connected flow chamber is perfused by the liquid in a predetermined direction (from inflow to outflow), regardless of whether the liquid is supplied at the first inlet orifice or the second inlet orifice. The flow chamber can be used as a cell culture chamber that is perfused unidirectionally by the liquid. The microfluidic device, including the cell culture chamber, is thus designed to cultivate cell cultures under a unidirectional flow. The previously described advantages of the microfluidic device still apply.

[0035] The flow chamber may further comprise a porous membrane that divides the flow chamber into a first region and a second region, with the inlet and outlet fluidically connected to the first region. The porous membrane is particularly permeable to the liquid.

[0036] Such a setup enables the simulation of systems in which a concentration gradient of gas dissolved in a liquid exists. Consider the flow chamber, in which both areas are filled with liquid. The first area is flowed through by liquid containing a certain concentration of gas, specifically oxygen. A different oxygen concentration may be present in the second area. If different oxygen concentrations exist in the two areas, diffusive exchange occurs through the porous membrane, resulting in a slow equalization of the oxygen concentration in both areas.

[0037] One possible application example is the simulation of an intestinal model. The intestine is in a hypoxic regime with reduced oxygen concentration (<21%). The surrounding blood vessels, in contrast, exhibit a normal oxygen concentration of around 21%. The flow chamber unit allows the transport processes between the intestine and the blood vessels to be realistically simulated and investigated in a compact and simplified setup.

[0038] The flux chamber may be formed in the substrate of the rectifier unit.

[0039] The entire microfluidic device can be designed compactly in this way, since both the flow chamber and the rectifier unit are located on or in a common substrate. This is also advantageous for easy handling, as it eliminates the need to connect multiple individual components. Furthermore, the connection between the first rectifier port and the inlet, as well as between the second rectifier port and the outlet, can be at least partially formed as a channel in the substrate. As previously stated, this aspect reduces the risk of bubble formation in the fluid and the fluid volume required for perfusion.

[0040] Alternatively, the flow chamber can be formed in a separate substrate. It is also possible for the flow chamber, together with the first and second liquid reservoirs, to be formed in a separate substrate from the rectifier unit.

[0041] Furthermore, a sensor for measuring the oxygen concentration of the liquid may be provided. The sensor is therefore also referred to below as an oxygen sensor.

[0042] The oxygen sensor can be located inside the flow chamber, for example, by being glued to it. The oxygen sensor can be optically read from outside because the sensor exhibits a change in fluorescence depending on the oxygen concentration of the liquid. In this respect, it can be an optically readable sensor.

[0043] The oxygen sensor can also be used to regulate the oxygen concentration in the liquid. For this purpose, the oxygen sensor is connected to a gas mixer via a feedback loop. The gas mixer can be configured to generate a gas mixture with specific proportions of individual gases (e.g., oxygen, nitrogen, carbon dioxide, etc.) and to introduce the gas mixture via a connection into one or both of the liquid reservoirs. The feedback loop determines which proportions of the gases must be mixed so that the liquid has a predefined oxygen concentration. This process can be carried out continuously.

[0044] The described rectifier unit can be constructed in multiple parts. In this case, the substrate comprises a base plate, a cover plate, and a center plate, wherein at least one trench is formed in an underside of the center plate facing the base plate, and wherein at least one trench is formed in an upper side of the center plate facing the cover plate. The base plate and the center plate, as well as the cover plate and the center plate, are connected to one another in a planar manner, such that the trench in the upper side is covered by the cover plate and the trench in the underside is covered by the base plate, and wherein the covered trenches are part of the fluid channel arrangement or channel system.

[0045] Dividing the device into three individual units that are combined to form a microfluidic device simplifies the manufacturing of the device. For example, the center plate can be manufactured using injection molding, which is a simple, precise, and cost-effective manufacturing method. While injection molding cannot easily create cavities in a component to be manufactured, forming grooves on the top and bottom sides of the center plate, which are covered by the top plate and the bottom plate, respectively, represents a simple alternative for obtaining an equivalent microfluidic device.

[0046] The substrate may comprise or consist of a plastic. In particular, it may comprise plastics such as COC (cycloolefin copolymer), COP (cycloolefin polymer), PC (polycarbonate), PS (polystyrene), PE (polyethylene), PMMA (polymethyl methacrylate), or a transparent thermoplastic or elastomer.

[0047] The substrate can be manufactured by injection molding. Using the materials and processes mentioned above, the microfluidic devices can be produced cost-effectively and in large quantities with consistent quality. This is because injection molding with plastics is an established and reliable process and is particularly applicable to the aforementioned plastics.

[0048] Alternatively, the substrate may comprise a glass.

[0049] The glass or plastic may in particular exhibit the birefringence and autofluorescence of a Schott cover glass (such as D 263 M Schott Glass, No. 1.5H (170 + / - 5 µm)).

[0050] An optically high-quality material can enable microscopy examinations with high precision and low optical imperfections.

[0051] The center plate can have a thickness between 0.5 mm and 2 cm, in particular between 0.5 mm and 5 mm. The thickness refers to the distance between the top and bottom of the center plate. The base plate can have a thickness between 1 µm and 2 mm, in particular between 1 µm and 300 µm. An analogous definition applies to the thickness of the base plate. The statements regarding the base plate apply analogously to the cover plate. The external dimensions of the substrate can be 25 mm by 75 mm or 85.4 mm by 127.6 mm.

[0052] The cover plate may comprise a first film, and / or the base plate may comprise a second film. In particular, the cover plate and / or the base plate may be transparent in the visible spectral range.

[0053] The first film and / or the second film can comprise or consist of the aforementioned plastics. The first film and / or the second film can have a refractive index of 1.5, minimal intrinsic fluorescence, and / or minimal birefringence. The thickness of the first film and the second film can range between 1 µm and 300 µm.

[0054] The cover plate, in the form of a first film, can be attached to the middle plate by welding, e.g., ultrasonic welding or solvent welding. Gluing is also conceivable, for example, with dispersion adhesives or an adhesive film (double-sided adhesive film). The same considerations also apply to the base plate, in the form of the second film.

[0055] The base plate and the middle plate, as well as the cover plate and the middle plate, are connected to each other in such a way that the optical properties of the substrate and thus of the microfluidic device are preserved, allowing, for example, microscopy, particularly fluorescence microscopy or inverted microscopy, to be performed with the microfluidic device. At the same time, these methods are established in connection with plastic components and represent a cost-effective and efficient way of attaching the base plate and the cover plate to the middle plate.

[0056] The transparency of the first film and / or the second film may be a prerequisite for performing microscopy on the microfluidic device.

[0057] A low thickness of the base plate and / or cover plate within the specified range has the advantage that, during inverted microscopy, the objective lens can be brought particularly close to the observed region in the microfluidic device (in the substrate). This enables improved optical resolution.

[0058] The microfluidic device may further comprise a compressed air unit fluidically connected to the first liquid reservoir and the second liquid reservoir, wherein the compressed air unit is configured to provide compressed air so that the liquid can be pumped from the first liquid reservoir through the fluid channel arrangement toward the second liquid reservoir, as well as in the reverse direction.

[0059] The compressed air unit can be or comprise an air pump, a piston pump, a diaphragm pump, a peristaltic pump, a syringe, or a syringe pump to supply compressed air to the first and / or second fluid reservoir. Pressure refers to both positive pressure and negative pressure. In the case of negative pressure, the fluid would be sucked in.

[0060] The use of a compressed air unit that is spatially separated from a fluid circuit in the microfluidic system between the first fluid reservoir and the second fluid reservoir by an air column has the advantage that the fluid does not come into contact with parts of the compressed air unit. This would be the case, for example, if a fluid pump were used to pump the fluid. This can prevent potential contamination of the fluid.

[0061] The present invention further provides a microfluidic system. This comprises the previously described microfluidic device and an incubator, wherein the microfluidic device is arranged within the incubator such that a fluid circuit of the microfluidic device lies entirely within the incubator. The fluid circuit can be defined between the first inlet opening and the second inlet opening or between the first fluid reservoir and the second fluid reservoir.

[0062] In other words, this means that the liquid remains exclusively within the incubator, and no additional liquid is added from outside. The conveyance or pumping is carried out using compressed air through the compressed air unit.

[0063] The compressed air unit can optionally be located outside the incubator, preventing unwanted heating inside the incubator due to waste heat from the compressed air unit. A gas-filled hose can be used to connect the compressed air unit to the supply unit, for example, via an interface or through an external wall of the incubator.

[0064] Such an arrangement, in which the entire fluid circuit is located within the incubator, is advantageous because it prevents the formation of bubbles in the fluid, which can otherwise occur due to a temperature gradient. Furthermore, the rectifier unit, the flow chamber, and the supply unit can be stored in the incubator under predetermined environmental conditions. This allows for advantageous cultivation and study of living cells, in particular, in the flow chamber.

[0065] Furthermore, the invention comprises a method comprising the following steps: providing the microfluidic device according to the above description, supplying a liquid at the first inlet opening and pumping the liquid through the fluid channel arrangement towards the second inlet opening, and reversing the pumping direction by pumping the liquid through the fluid channel arrangement towards the first inlet opening.

[0066] To supply the liquid at the first inlet port, the valve arrangement is brought into the first state and to reverse the pumping direction, the valve arrangement is brought into the second state.

[0067] This method enables the generation of a unidirectional flow, allowing a compact design of a cell examination device and suppressing bubble formation during the transport of a liquid through a microfluidic device or a system comprising the microfluidic device.

[0068] The supply of liquid and the reversal of the pumping direction can be controlled using compressed air.

[0069] As already described in the context of the microfluidic device, the use of compressed air to convey the fluid has the advantage that the fluid does not come into contact with parts of a compressed air unit that supply the compressed air. This can prevent potential contamination of the fluid.

[0070] The method may further comprise incubating the microfluidic device in an incubator, wherein the microfluidic device is arranged within the incubator such that a fluid circuit of the device is located entirely within the incubator. This means that the fluid remains exclusively within the incubator, and no fluid is added from the outside. As already described in connection with the system, living cells, in particular, can be advantageously examined using this method.

[0071] Furthermore, the present invention provides a supply unit comprising: a substrate having a first liquid reservoir formed on or in the substrate and a second liquid reservoir formed on or in the substrate, wherein each of the liquid reservoirs comprises a supply line, and wherein the first liquid reservoir and / or the second liquid reservoir comprises a line which projects from the outside into the interior of the respective liquid reservoir.

[0072] This design of a liquid reservoir offers the possibility of influencing the properties of the liquid in the liquid reservoir and, if applicable, in the microfluidic system. One possible application, for example, is to conduct a gas through the line into the interior of the respective liquid reservoir. If a liquid is present in the respective liquid reservoir and the line extends into the liquid, the gas is conducted into the liquid, thus influencing the gas content of the liquid. Furthermore, the gas content of the liquid can be adjusted more easily and precisely than if the gas were merely located above the liquid. This aspect will be discussed in more detail below.

[0073] For example, the line can be a rigid pipe or a flexible hose. The line can also be composed of a rigid pipe and a flexible hose.

[0074] The line can be led through a cover or a side wall of the respective liquid reservoir into its interior.

[0075] The supply line(s) of one or both liquid reservoirs can be formed in the substrate. In particular, the supply lines can be formed at least partially in the form of a channel in the substrate.

[0076] This aspect has the advantage of eliminating the need for hose connections and shortening the fluid transport path. This reduces the likelihood of the fluid being exposed to a temperature gradient, thus reducing the risk of bubble formation in the fluid.

[0077] The oxygen sensor can be located inside the flow chamber, for example, by being glued to it. The oxygen sensor can be optically read from outside because the sensor exhibits a change in fluorescence depending on the oxygen concentration of the liquid. In this respect, it can be an optically readable sensor.

[0078] Furthermore, a sensor for measuring the oxygen concentration of the liquid can be provided. The sensor is therefore also referred to below as an oxygen sensor. The oxygen sensor can be an optical sensor. It can be arranged, for example, glued, within one of the liquid reservoirs. The oxygen sensor can have a change in its fluorescence depending on the oxygen concentration of the liquid. The oxygen sensor can be read optically, and the oxygen concentration of the liquid can be measured accordingly. In this respect, it can be an optically readable sensor. As explained below, the oxygen concentration in the liquid can also be used for control and / or simulation purposes using the sensor.

[0079] Furthermore, a supply system is provided, comprising the described supply unit and a gas source including a gas mixer. The gas mixer is configured to generate a gas mixture with specific proportions of individual gases (e.g., oxygen, nitrogen, carbon dioxide, etc.). The gas mixture is fed into the interior of the respective liquid reservoir via a gas connection and the line.

[0080] This system offers the possibility described above to realistically simulate complex systems in a compact and simplified structure.

[0081] The supply unit can be used with the previously described microfluidic device. The supply system can also be combined with the microfluidic system.

[0082] Further features and advantages are explained below using the example figures. They show: Figure 1 shows a schematic cross-sectional view looking at the top of a microfluidic device; Figure 2 shows a schematic cross-sectional view looking at the bottom of a microfluidic device according to Fig. 1 ; Figure 3A shows a schematic representation of a closed umbrella valve in cross section; Figure 3B shows a schematic representation of an open umbrella valve in cross section; Figure 4 shows a schematic cross-sectional view looking at the top of another microfluidic device; Figure 5 shows a schematic cross-sectional view looking at the bottom of a microfluidic device according to Fig. 4 ; Figure 6 shows a schematic representation of a microfluidic system; and Figure 7 shows a schematic cross-sectional view of a supply unit,

[0083] In the following and in the figures, the same reference numerals are used for the same or corresponding elements in the various embodiments, unless otherwise specified.

[0084] In Figure 1 A first embodiment of a microfluidic device 1 is shown as a cross-sectional view, so that a top side of the microfluidic device 1 is shown. The microfluidic device 1 comprises a rectifier unit 10. As will be explained in more detail below, the rectifier unit 10 is designed to generate a unidirectional flow, regardless of the inlet opening at which a liquid is supplied. The rectifier unit 10 comprises a substrate 11 in which a valve arrangement 20 and a fluid channel arrangement are arranged. The design of the valve arrangement 20 and the fluid channel arrangement will now be explained in detail.

[0085] White-framed areas represent through-holes extending from the bottom to the top of the substrate 11. Hatched, framed areas are depressions or grooves formed in the top side (or in the bottom side, see Figure 2). The microfluidic device can be constructed in multiple parts, and the substrate can comprise a base plate, a middle plate, and a cover plate. For simplicity, only the middle plate is shown in the figures. The cover plate and base plate can be a film that is welded or glued to the middle plate. As a result, the grooves / recesses in the middle plate are covered by the base plate and the cover plate, respectively, and corresponding channels are formed.

[0086] Solvent welding or ultrasonic welding are possible methods for welding. Dispersion adhesives or adhesive films, such as double-sided adhesive films, are suitable for bonding.

[0087] In this sense, the channel system 30 comprises two levels, or rather, the channel system is arranged in two levels. The first level is represented by the trenches formed in the upper side of the center plate. The second level is represented by the trenches formed in the underside of the center plate. The two levels are fluidically connected to one another by at least one of the valves in the valve arrangement 20. Likewise, the through holes fluidically connect the two levels.

[0088] The fluid channel arrangement comprises a first inlet opening 12 and a second inlet opening 13. Both inlet openings can be used to supply a liquid to the fluid channel arrangement. The fluid channel arrangement further comprises a first rectifier opening 14 and a second rectifier opening 15. A channel system is formed / arranged between these four openings (see Figure 2). The channel system fluidically connects the first inlet opening 12 via the valve arrangement 20 to the first rectifier opening 14 and the second inlet opening 13 via the valve arrangement fluidically connects the second rectifier opening 15, or the channel system 30 fluidically connects the first inlet opening 12 via the valve arrangement 20 to the second rectifier opening 15 and the second inlet opening 13 via the valve arrangement 20 to the first rectifier opening 14. In other words, this means that the liquid always exits at the first rectifier opening 14, regardless of whether the liquid is supplied at the first inlet opening 12 or the second inlet opening 13.

[0089] The valve arrangement 20 comprises four valves 20a, 20b, 20c, 20d. At least one of these valves is an umbrella valve; in this case, all four valves 20a, 20b, 20c, 20d are umbrella valves. The two valves 20a and 20b are arranged such that the umbrella is located on the upper side shown (indicated by dashed lines). Below the umbrella are three through holes 23, whose cross-section has the shape of a circular ring segment with rounded corners. The round middle hole is provided for the attachment of the respective umbrella valve (see Figure 3 and associated description). In reference to a human kidney, this cross-sectional shape of the three through holes 23 of each valve is also referred to as kidney-shaped.

[0090] Figure 21 now shows a cross-sectional view of the underside of the microfluidic device 1 according to the first embodiment. Channels in the form of grooves are formed on the underside, or rather the underside of the center plate. These grooves together form the channel system 30. Furthermore, the two umbrella valves 20c and 20d are arranged such that the respective umbrella is located on the underside (indicated by dashed lines).

[0091] One intended use of this rectifier unit 10 will now be explained in detail. In addition to the first inlet opening 12 and the second inlet opening 13, the rectifier unit 10 also includes four additional openings (not specified in more detail) that serve the purpose of flushing and filling the fluid channel arrangement with liquid before use of the microfluidic device 1. These additional openings have no function for the rectifier function itself. Before use, these four additional openings are sealed liquid-tight. The additional openings allow the fluid channel arrangement to be cleaned and freed of air.

[0092] If liquid is now supplied at the first inlet opening 12, it is first guided along the underside of the channel system 30 and then flows through valve 20b to the top (valve 20c is closed because the liquid pressure presses the screen onto the through-holes, thus blocking the flow). From there, the liquid flows on to the rectifier opening 14 because valve 20a is closed (screen on the top). Conversely, if the liquid is supplied at the second inlet opening 13, it passes through valve 20a and also reaches the first rectifier opening 14 because valve 20b is closed (screen on the top). If a flow chamber is connected to the two rectifier openings 14, 15, the liquid flows through the second rectifier opening 15 after flowing through the flow chamber and back into the rectifier unit 10.When the liquid is supplied to the first inlet port 12, the valve 20c is kept closed by the liquid pressure and the liquid flows through valve 20d and the channel system 30 to the second inlet port 13. Conversely, if the liquid is originally supplied to the second inlet port 13, the liquid is directed from the second rectifier port 15 to the first inlet port 12 through the valve 20c.

[0093] This illustrates how the rectifier unit 10 can provide unidirectional flow, regardless of whether the liquid is supplied at the first inlet 12 or the second inlet 13. The use of umbrella valves with through-holes 23 arranged below the umbrella suppresses the disruptive fixation of bubbles in the liquid, enabling particularly physiological conditions for cell cultivation. Furthermore, the arrangement of all components of the rectifier unit 10 in a substrate 11 represents a compact and flexible design.

[0094] It is understood that other configurations of a rectifier arrangement can also fulfill the intended function and the present invention is therefore not limited to this embodiment according to the Figures 1 and 2 is limited.

[0095] Figures 3A and 3B show an example of a cross section of an umbrella valve 24, wherein Figure 3Athe umbrella valve 24 in the closed state (also blocking state) and Figure 3B shows the umbrella valve in the open state. The umbrella valve 24 comprises a shield 21 and a fastening element 22. The umbrella valve 24 is designed such that the fastening element 22 is inserted through a fastening hole in the substrate 11 of the rectifier assembly and is thereby held in position. The shield 21 covers one or more through-holes 23 formed in the substrate 11. The through-holes can connect a first level of the channel system 30 to a second level of the channel system 30.

[0096] The arrows indicate the flow direction of a fluid relative to the umbrella valve 24. When the fluid hits the side of the umbrella 21 facing away from the through holes 23 (see Figure 3A), the umbrella 21 is pressed against the through holes 23 by the fluid pressure. The through holes 23 are thus sealed and the flow of fluid is blocked. The umbrella valve 21 is in a blocking state. The mutual case is in Figure 3B shown. When the liquid hits the side of the shield facing the through-holes 23, the shield 21 is pushed away from the substrate 11 by the liquid pressure, and the liquid can flow around the shield 21. The shield valve is in an open state.

[0097] Components of the umbrella valve 24, in particular the umbrella 21, can be made of or comprise an elastic material. Suitable materials include, for example, an elastomer material such as silicone, liquid silicone rubber, fluorosilicone, nitrile rubber, or neoprene, or a suitable combination thereof. An umbrella valve is a passive check valve. As previously described, umbrella valves with through holes arranged below the umbrella have the advantage of reducing bubble formation. Furthermore, umbrella valves are a cost-effective option for use as a check valve.

[0098] Figures 4 and 5 show a cross-sectional view of a second embodiment of the microfluidic device 1, wherein Figure 4 the top and Figure 5the underside. The above statements regarding the first embodiment apply equally or analogously to this second embodiment, as they are largely very similar. Therefore, only the differences between the two embodiments will be highlighted below.

[0099] A flow chamber 40 is also formed in the substrate 11. This can be in the form of a through-hole or in the form of a recess, particularly in the upper side. The fluid channel arrangement, in particular the channel system 30, is largely identical to the first embodiment, so that the fluid path is also very similar. Depending on whether the fluid is supplied at the first inlet opening 12 or the second inlet opening 13, the fluid passes through the valve 20a or 20b to the upper side (first level) and floods the flow chamber 40, so that a fluid exchange takes place in the flow chamber 40. The fluid then flows further through valve 20c or 20d to the second inlet opening 13 or the first inlet opening 12, respectively.

[0100] The area between valve 20b and flow chamber 40 can be considered as inlet 41, and the area between flow chamber 40 and valve 20c can be considered as outlet 42. Furthermore, valves 20a and 20b (depending on where the fluid enters the first level when supplied at the first inlet port 12 or the second inlet port 13) also assume the role of the first rectifier port 14. Analogously, valves 20c and 20d assume the role of the second rectifier port 15.

[0101] This embodiment combines the flow chamber 40 and the rectifier unit 10 on a common substrate. This compacts the entire structure. A further advantage is that no hoses or similar fluid connections are required between the fluid channel arrangement and the flow chamber 40. This eliminates the need to transport the fluid through a potential temperature gradient, further reducing the risk of bubble formation in the fluid. Furthermore, the hoses would create dead volume, which is avoided here and reduces the required amount of fluid.

[0102] Figure 6depicts a microfluidic system 100 according to the invention. The microfluidic system 100 comprises a previously described microfluidic device 1 with a rectifier unit 10, a flow chamber unit 46, a supply unit 50, and a compressed air unit 60. The rectifier unit 10, the flow chamber unit 46, and the supply unit 50. The microfluidic device 1 is arranged in an incubator 90. In principle, the microfluidic device 1 in the form described in this example can also be considered to fall within the scope of the invention on its own.

[0103] The rectifier unit 10 may be a previously described rectifier unit 10.

[0104] The flow chamber unit 46 comprises a flow chamber 40, as well as an inlet 41 and an outlet 42. The inlet 41 is fluidically connected to the first rectifier orifice 14 of the rectifier unit 10, and the outlet 42 is fluidically connected to the second rectifier orifice 15 of the rectifier unit 10. The flow chamber unit 46 comprises its own substrate 45. However, it is also possible for the flow chamber unit 46 to be formed in the same substrate 11 as the rectifier unit 10, or for the substrate 11 and the substrate 45 to be connected to form a common substrate.

[0105] In addition, the flow chamber unit 46 includes a sensor 44 for measuring the oxygen concentration of the liquid in the flow chamber 40. The oxygen sensor can be optically read from outside the flow chamber 40 because the sensor exhibits a change in fluorescence depending on the oxygen concentration of the liquid. In this respect, it can be an optically readable sensor.

[0106] Sensor 44 can interact with the gas mixer to form a control loop. To do this, sensor 44 transmits a measured value to the gas mixer. The gas mixer then generates a gas mixture such that the oxygen content of the liquid is adjusted to a predetermined value. This process can be performed continuously, thus forming a control loop.

[0107] Furthermore, the microfluidic device 1 comprises a supply unit 50 with a first liquid reservoir 51 and a second liquid reservoir 52. The first liquid reservoir 51 and the second liquid reservoir 52 are formed in or on a substrate 53, which is also part of the supply unit 50. The first liquid reservoir 51 is fluidically connected to the first inlet opening 12 via a connection, for example, a hose connection 5112. The second liquid reservoir 52 is fluidically connected to the second inlet opening 13 via a connection, for example, a hose connection 5212.

[0108] Finally, the microfluidic device 1 comprises a compressed air unit 60. The compressed air unit 60 is designed to provide compressed air so that the liquid can be pumped from the first liquid reservoir 51 through the fluid channel arrangement in the rectifier unit 10 toward the second liquid reservoir 52, and in the opposite direction. This means that the liquid is practically pumped back and forth in a closed circuit between the first liquid reservoir 51 and the second liquid reservoir 52, without the need for additional liquid to be supplied from the outside. A closed system can thus be realized that is protected from potential contamination by external influences. For this purpose, the compressed air unit 60 has air hoses 61, 62, which can optionally be connected in a gas-tight manner to the first liquid reservoir 51 and the second liquid reservoir, respectively.The compressed air unit 60 may be or comprise an air pressure pump, a piston pump, a diaphragm pump, a peristaltic pump, a syringe or a syringe pump in order to supply the first liquid reservoir 51 and / or the second liquid reservoir 52 with compressed air.

[0109] The use of a compressed air unit that is spatially separated from a fluid circuit in the microfluidic system between the first fluid reservoir and the second fluid reservoir by an air column also offers the advantage that the fluid does not come into contact with parts of the compressed air unit. This would be the case, for example, if a fluid pump were used to pump the fluid. This avoids potential contamination of the fluid.

[0110] As shown, the supply unit 50 comprises a substrate 53 that is separate from the substrate 11 of the rectifier unit 10. However, it is conceivable that the two substrates 11 and 53 are connected to form a common substrate. In this case, the microfluidic device can be designed even more compactly and manufactured more easily, i.e., in one piece.

[0111] As described, the microfluidic device 1 comprising the four said components (rectifier unit 10, flow chamber unit 46, supply unit 50 and compressed air unit 60) can stand alone.

[0112] For example, cells or cell aggregates can be present in the flow chamber 40, which are cultured under a continuous and unidirectional flow. It may also be provided to observe these cells under a microscope. For this purpose, the flow chamber unit 46 can be viewed under a microscope, optionally an inverted microscope.

[0113] A microfluidic system 100 according to the invention is formed when one of the microfluidic devices 10 described above, with the exception of an optionally provided compressed air unit 60, is arranged in an incubator 90. An incubator is a closed and controllable space that can be temperature-controlled, gassed, and humidified so that constant and / or controllable conditions prevail even over long periods of time. The compressed air unit 60 should not be arranged in the incubator because any waste heat generated by a pump or similar components provided in the compressed air unit 60 can influence the climate in the incubator 90.

[0114] The system thus combines the previously described advantages of the microfluidic device with the advantageous properties of the incubator. These include the provision of adjustable and temporally constant environmental conditions for advantageous examination of living cells under physiologically relevant conditions. It is conceivable to observe the incubator with a microscope. This also allows for microscopic examination of the cultured cells.

[0115] A system comprising the described microfluidic system and the described flow chamber system is also conceivable. In such a system, it is possible to simulate organ models and conduct studies simultaneously. The microfluidic system provides fluid perfusion. The flow chamber system provides the flow chamber in which conditions similar to those in a natural organ are created and simulated. For example, the gas mixer creates a specific oxygen concentration that is intended to mimic the hypoxic conditions in the intestine. In this way, complex natural systems such as human organs can be simulated and studied in a compact setup.

[0116] Figure 7shows the cross-section of a supply unit 50 according to the invention in cross-section. The supply unit 50 comprises a substrate 53, a first liquid reservoir 51, and a second liquid reservoir 52, whereby only one liquid reservoir 51 is shown in the figure for illustrative purposes. The liquid reservoir 51 comprises a supply line 5112 / 5213 for supplying and discharging liquid from the liquid reservoir 51 (note that the connection 5112 / 5213 performs the function). The supply line can be formed in the substrate 53. The liquid reservoir 51 is formed here on the substrate 53, but can in principle also be formed in the substrate 11 of the rectifier unit 10 of the microfluidic device 1. Furthermore, the supply unit 50 comprises a line 54 that leads from the outside into the interior of the liquid reservoir 51.The line 54 can, for example, be routed through a cover or a side wall into the interior of the liquid reservoir 51. In the illustrated case, the line 54 is a tube that is routed through the cover. If a liquid is present inside the liquid reservoir 51, as also indicated in the figure, the tube 54 extends into the liquid.

[0117] The line 54 can be a rigid pipe. The line 54 can also be a flexible hose. Likewise, the line 54 can be composed of a rigid pipe and a flexible hose.

[0118] In addition, the line 54 can be connected to a gas source via a gas-tight connection, for example a suitable hose. In particular, the gas source (not shown) can comprise a gas mixer. The gas mixer can be designed to generate a gas mixture with specific proportions of individual gases (e.g. oxygen, nitrogen, carbon dioxide, etc.). This gas mixture is then fed into the liquid reservoir 51 via the connection and the line 54. This makes it possible to control the gas content of the liquid. For example, the oxygen content of the liquid can be reduced if a gas mixture is introduced which has a reduced proportion of oxygen. Reduced proportion refers in particular to a lower proportion than in the oxygen content present in the environment, for example in air with an oxygen content of around 21%.For example, a gas mixture with a reduced oxygen content can have an oxygen content of less than 21%.

[0119] The supply unit 50 can be used in particular in conjunction with the described microfluidic device. For this purpose, the substrate 53 can, for example, correspond to the substrate 11 of the microfluidic device 1, so that the described components are present in a common substrate 11 of the microfluidic device 1. Alternatively, the supply unit 50 can be separate from the previously described microfluidic device 1. In this case, the supply line 5112 / 5213 can be arranged as shown in Figure 6 shown to be connected to the first rectifier orifice 14. The same applies to the second liquid reservoir 52 and the second rectifier orifice 15.

[0120] One possible implementation provides for a gas mixture generated by the gas mixer to be fed to the compressed air unit 60. The compressed air unit then feeds the pressurized gas mixture via line 54 into the respective liquid reservoir. Optionally, an additional outlet can be provided at the first liquid reservoir 51 and / or the second liquid reservoir 52. This additional outlet is designed for pressure equalization, since otherwise the liquid could be forced through the connection 5112 / 5213 toward the rectifier unit 10 by the pressure from the compressed air unit.

Claims

1. A microfluidic device (1) comprising a rectifier unit (10), wherein the rectifier unit (10) comprises: a substrate (11), a valve arrangement (20) formed in the substrate (11), and a fluid channel arrangement formed in the substrate (11), comprising: a first inlet opening (12) and a second inlet opening (13), a first rectifier opening (14) and a second rectifier opening (15), and a channel system (30), wherein the channel system (30) fluidically connects the first inlet opening (12) to the first rectifier opening (14) via the valve arrangement (20) and fluidically connects the second inlet opening (13) to the second rectifier opening (15) via the valve arrangement (20),or wherein the channel system (30) fluidically connects the first inlet opening (12) via the valve arrangement (20) to the second rectifier opening (15) and fluidically connects the second inlet opening (13) via the valve arrangement (20) to the first rectifier opening (14), wherein the valve arrangement (20) can be brought from a first state into a second state, wherein in the first state a liquid can be conveyed from the first inlet opening (12) to the first rectifier opening (14) and from the second rectifier opening (15) to the second inlet opening (13), and wherein in the second state the liquid can be conveyed from the second inlet opening (13) to the first rectifier opening (14) and from the second rectifier opening (15) to the first inlet opening (12), wherein the valve arrangement (20) comprises four valves (20a, 20b, 20c, 20d), one of which is an umbrella valve (24) is,in which a through hole (23) is formed under the screen (21) of the screen valve (24), which through hole is covered by the screen (21) when the valve is in a closed state., 2. Microfluidic device (1) according to claim 1, wherein the channel system (30) is arranged in a first plane and a second plane, wherein the first plane is formed parallel to the second plane, and wherein the first plane and the second plane are fluidically connected to one another by at least one of the valves of the valve arrangement (20).

3. Microfluidic device (1) according to claim 1 or 2, wherein each valve of the valve arrangement (20) is an umbrella valve (24).

4. Microfluidic device (1) according to claim 2 or 3, wherein two of the valves (24) are configured to block flow from the first level to the second level and the other two of the valves (24) are configured to block flow from the second level to the first level.

5. Microfluidic device (1) according to one of the preceding claims, wherein exactly two, three, four or five through holes (23) are arranged under the umbrella (21) of each umbrella valve (24), in particular whose cross section corresponds to a circular ring segment with rounded corners.

6. Microfluidic device (10) according to one of the preceding claims, wherein the length of a section of the channel system (30) connecting the first inlet opening (12) to the first rectifier opening (14) is identical to the length of a section of the channel system (30) connecting the second inlet opening (13) to the second rectifier opening (15), and / or wherein the length of a section of the channel system (30) connecting the first inlet opening (12) to the second rectifier opening (14) is identical to the length of a section of the channel system (30) connecting the second inlet opening (13) to the first rectifier opening (15).

7. Microfluidic device (1) according to one of the preceding claims, further comprising a supply unit (50) with a first liquid reservoir (51) and a second liquid reservoir (52), wherein the first inlet opening (12) is fluidically connected to the first liquid reservoir (51) and the second inlet opening (13) is fluidically connected to the second liquid reservoir (52), in particular, wherein the supply unit (50) comprises a supply substrate (53), and in particular, wherein the first liquid reservoir (51) and / or the second liquid reservoir (52) are formed in and / or on the supply substrate (53).

8. Microfluidic device (1) according to claim 7, wherein the first liquid reservoir (51) and / or the second liquid reservoir (52) further comprises a line (54) guided from the outside into the interior of the respective liquid reservoir, wherein the line (54) is guided in particular through a cover or through a side wall of the respective liquid reservoir.

9. Microfluidic device (1) according to one of the preceding claims, further comprising a flow chamber (40), wherein the flow chamber (40) comprises an inlet (41) and an outlet (42), wherein the inlet (41) of the flow chamber (40) is fluidically connected to the first rectifier orifice (14) and the outlet (42) of the flow chamber (40) is fluidically connected to the second rectifier orifice (15), and in particular wherein the flow chamber (40) is formed in the substrate (11).

10. Microfluidic device (1) according to claim 9, further comprising a sensor (44) for measuring an oxygen concentration of the liquid.

11. Microfluidic device (1) according to one of the preceding claims, wherein the substrate (11) comprises: a base plate, a cover plate and a middle plate, wherein at least one trench is formed in an underside of the middle plate facing the base plate and wherein at least one trench is formed in an upper side of the middle plate facing the cover plate, wherein the base plate and the middle plate, as well as the cover plate and the middle plate are connected to one another in a planar manner, such that the trench in the upper side is covered by the cover plate and the trench in the underside is covered by the base plate, and wherein the covered trenches are part of the fluid channel arrangement.

12. Microfluidic device (1) according to one of the preceding claims, wherein the cover plate comprises a first film, and / or wherein the base plate comprises a second film, and / or wherein the cover plate and / or the base plate is / are transparent in the visible spectral range.

13. Microfluidic device (1) according to one of claims 7 to 12, further comprising a compressed air unit (60) which is fluidically connected to the first liquid reservoir (51) and the second liquid reservoir (52), wherein the compressed air unit (60) is designed and arranged to pump a liquid from the first liquid reservoir (51) through the fluid channel arrangement in the direction of the second liquid reservoir (52) and in the reverse direction by means of compressed air.

14. A microfluidic system (100) comprising: a microfluidic device (1) according to any one of the preceding claims, and an incubator (90), wherein the microfluidic device (1) is arranged within the incubator (90) such that a liquid circuit of the microfluidic device (1) lies entirely within the incubator (90).

15. A method comprising: providing a microfluidic device (1) according to any one of claims 1 to 13 or a microfluidic system (100) according to claim 14, providing a liquid at the first inlet opening (12) and pumping the liquid through the fluid channel arrangement in the direction of the second inlet opening (13), and reversing the pumping direction by pumping the liquid through the fluid channel arrangement in the direction of the first inlet opening (12), in particular, wherein the provision of the liquid and the reversing of the pumping direction are controlled by means of compressed air, and / or in particular, wherein the method further comprises: incubating the microfluidic device (1) in an incubator (90), wherein a liquid circuit of the microfluidic device (1) or of the microfluidic system (100) is located entirely within the incubator (90).

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