Microfluidic devices for membrane analysis

Abstract

A microfluidic device for analyzing the permeability of a substance through a membrane. A plurality of flow channels pass respective fluid flows with the substance through the housing between respective connectors. An access cavity extends from the exterior into the housing through the first flow channel and into the second flow channel 12, providing access to the interior of the housing. The membrane can be positioned over a cavity opening that forms a fluid interconnection between the overlapping areas of the flow channels. A clamping ring in the first flow channel holds the sample membrane in place over the cavity opening while the membrane is exposed to the respective fluid flows through the flow channels on either side of the membrane. A retaining ring in the first flow channel holds the sample membrane in place over the cavity opening while the membrane is exposed to the respective fluid flows through the flow channels on either side of the membrane.

Description

[Technical field]

[0001] The present disclosure relates to a microfluidic device, such as a chip or a flow cell, and also to a method for analyzing the permeability of a sample membrane, such as an (epithelial) barrier, a (fresh) tissue explant, a cell layer, a scaffold, or other membrane. For example, a tissue explant may contain different cell types that can be distinguished from a cell monolayer or bilayer, or a suspension of cells injected into the chip. [Background technology]

[0002] WO 2012 / 118799 A2 describes systems and methods for culturing and / or maintaining in vitro intestinal cells, tissues and / or organoids that mimic or recapitulate the structure and behavior of the native intestinal epithelium and are capable of supporting the co-cultivation of the intestinal microbiota.

[0003] WO 2014 / 069995 A1 describes a vial for holding a section of epithelial tissue. More specifically, WO 2014 / 069995 A1 describes a vial that is easy to assemble and allows horizontal alignment of the tissue sample. This prior art further relates to a device comprising said vial, a method for producing said device, and a number of said devices that allow medium throughput measurements of absorption, transport, and / or secretion through epithelial tissue.

[0004] EP 2233924 A1 describes a biochip assembly with a semipermeable membrane and an assay method for performing cell-based assays using said biochip assembly. Being able to observe the migration of biological cells through dense layers of other cells and tissues can be important for understanding disease mechanisms and developing therapeutics. In this prior art, a method is provided for measuring the migration of sample cells in an assembly with multiple compartments in fluid communication, the method comprising introducing an analyte into at least one analyte-containing compartment and introducing a sample cell into at least one sample cell-containing compartment, in which the sample cell is separated from the analyte by a semipermeable membrane, and the analyte and / or the sample cell are subjected to controlled flow conditions. As such, the assembly may comprise two compartments in the form of a channel divided in two by a semipermeable membrane, or a channel and a well / chamber. Alternatively, the assembly may comprise multiple compartments in the form of two or more channels, or even two or more channels and a well / chamber. The compartments are in fluid communication over at least a portion of the surface / length of the compartments, such that the analyte-containing compartment is separated from the sample cell-containing compartment by a semi-permeable membrane. Summary of the Invention [Problem to be solved by the invention]

[0005] One challenge with existing devices is to mimic the properties of human epithelial cells. For example, epithelial cells are cultured on a substrate to mimic epithelial tissue in the digestive tract. However, such cultured cells may not have all the intestinal epithelial subtypes and genetic variations of real epithelial tissue. Another or additional challenge may relate to mounting the epithelial tissue sample, e.g., the sample does not adhere well to both sides of the membrane. For example, proliferation (cell growth) makes it difficult to attach the tissue sample to both sides, which may result in leakage. Another or additional challenge may relate to reliably mounting and removing the membrane between channels inside the device. [Means for solving the problem]

[0006] Aspects of the present disclosure relate to a microfluidic device for analyzing the permeability of a substance through a (sample) membrane, for example to study various properties of an epithelial barrier, such as the permeability of the epithelial barrier to various biological and pharmacological substances. The microfluidic device comprises a housing having flow channels for passing respective fluid streams, e.g., two parallel streams, between respective connectors. For example, the substance can be dissolved or suspended in at least one of the fluid streams. An access cavity can be used to access the housing and place the membrane, e.g., biological barrier, over the cavity opening. The cavity opening is preferably a dedicated opening between the overlapping areas of the flow channels. of A fastening ring, preferably forming part of a flow channel, can be used to hold the sample membrane in place over the cavity opening while the membrane is exposed to the respective fluid flows through the flow channels on both sides of the membrane during use. The microfluidic device can be used in a system including pumps and respective reservoirs connected to the channels. Use of the microfluidic device or system can include placing the membrane between the first and second flow channels in the cavity opening and passing respective flows through the flow channels via the respective reservoirs on either side of the membrane.

[0007] These and other features, aspects, and advantages of the presently disclosed devices, systems, and methods will become better understood from the following description, appended claims, and accompanying drawings. [Brief description of the drawings]

[0008] [Figure 1A] FIG. 1A shows a perspective view of a microfluidic device closed by a cap. [Figure 1B] FIG. 1B shows another view of the microfluidic device without the cap to reveal the cavities that extend into the housing and interconnect the channels. [Figure 2A] FIG. 2A is a schematic diagram of the microfluidic device. [Figure 2B] FIG. 2B is a schematic diagram of the microfluidic device. [Figure 2C] FIG. 2C is a schematic diagram of the microfluidic device. [Figure 3A] FIG. 3A shows a cutaway / exploded view of the microfluidic device with its various components. [Figure 3B] FIG. 3B shows another enlarged cutaway view between the flow channels around the cavity opening. [Figure 4A] FIG. 4A shows a microfluidic device in which a membrane is disposed between a sealing ring and a fastening ring. [Figure 4B] FIG. 4B shows a microfluidic device in which the fastening ring comprises a channel. [Figure 5A] FIG. 5A shows a microfluidic device in which both flow channels are configured to reduce the channel height at the location of the membrane. [Figure 5B] FIG. 5B illustrates a system (not to scale) and method for using the microfluidic devices described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The terms used to describe particular embodiments are not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The word "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the words "comprising" and / or "comprising" specify the presence of the stated feature but do not preclude the presence or addition of one or more other features. When a particular step of a method is referred to as following another step, it will be further understood that the step may immediately follow the other step, or one or more intermediate steps may be performed prior to performing the particular step, unless otherwise specified. Similarly, when a connection between structures or components is described, it will be understood that the connection may be established directly or through an intermediate structure or component, unless otherwise specified.

[0010] The present invention will now be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic illustrations and / or cross-sectional illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numerals refer to like elements throughout. Relative terms and their derivatives should be construed as referring to the orientation shown in the drawings being described or discussed at the time. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation, unless specifically specified.

[0011] FIG. 1A shows a perspective view of a microfluidic device 100 closed by a cap 15. In one embodiment, for example as shown, the microfluidic device 100 has a housing forming at least two flow channels 11, 12. More than two channels can also be envisaged (not shown). In the embodiment shown, the microfluidic device 100 is semi-transparent, so that the channels 11, 12 through the housing 10 are visible, as well as the possible contents of the channels. This may allow easy viewing of the flow inside the housing without opening the cap. Other, for example opaque, materials can also be used. Preferably, the housing 10 comprises, for example consists essentially of, a material, for example plastic. In a preferred embodiment, for example as shown here, the device is manufactured by 3D printing. For example, the device is made from a printable (cured) material. Other manufacturing methods and materials can also be envisaged.

[0012] FIG. 1B shows another view of the microfluidic device 100 without the cap to show the cavity 13 that extends into the housing 10 and interconnects the channels 11, 12. In some embodiments, the channels 11, 12 extend between the respective connectors 11a, 11b; 12a, 12b. Preferably, the connectors protrude from the housing to connect (flexible) hoses or flow tubes (not shown here). For example, each connector has the shape of a short tube extending from the housing. In some embodiments, the connectors are tapered to more easily connect flow tubes. In other or further embodiments, the connectors have edges to prevent the flow tubes from slipping out. Alternatively, or in addition to protruding connectors, inwardly extending (recessed) connectors can also be envisaged (not shown). For example, a flow tube, or a connection thereof, can be inserted into the connector of the device housing. The inwardly facing connectors can also be tapered and / or provided with edges. Other types of connections between the device 100 and the respective flow tubes or other channels can also be envisioned.

[0013] In some embodiments, such as shown, the connectors 11a, 12a on the same side of the housing can be offset laterally (X) from the central plane. This can provide more room to place the connectors and / or connect external flow circuits, especially when the flow channels 11, 12 run close to each other in the height direction (Z). In some embodiments, such as shown, the flow channels 11, 12 are symmetrical before and after the access cavity 13. For example, the paths of the channels can be rotationally symmetric as in the embodiment shown, and / or mirror symmetric.

[0014] In one aspect, the present disclosure provides a microfluidic device 100 for analyzing the permeability of a substance through a (sample) membrane M. For example, the substances are disposed in respective fluid flows F1, F2. Typically, the microfluidic device 100 comprises a housing 10 having flow channels 11, 12. In some embodiments, the first flow channel 11 is configured to pass a first fluid flow F1 through the housing 10 between a first input connector 11 and a first output connector 11b. In other or further embodiments, the second flow channel 12 is configured to pass a second fluid flow F2 through the housing 10 between a second input connector 12a and a second output connector 12b.

[0015] In a preferred embodiment, the device comprises an access cavity 13, which extends from the outside through the first flow channel 11 into the housing 10 and into the second flow channel 12. The cavity can thus be used to access the interior of the housing 10 and to place the membrane M on a cavity opening 13i. Most preferably, the cavity opening 13i forms a (dedicated) fluid interconnection between the overlapping areas of the flow channels 11, 12.

[0016] In a preferred embodiment, the access cavity 13 can be opened and / or closed by a cap 15. Most preferably, the cap 15 can be reversibly removed to access the cavity, for example to place or replace the membrane M. For example, the cap 15 and / or the housing comprise an elastic material, e.g. rubber, between them to seal the cap to the housing. Other elastic structures can also be used, or the cap can be screwed onto the housing.

[0017] In one embodiment, for example as shown, the flow channels 11, 12 have a channel width Wh (in a transverse direction X transverse to the main flow direction Y) immediately before or immediately after the cavity opening 13i, which is larger than the cross-sectional diameter Wi of the cavity opening 13i between the flow channels 11, 12, for example at least 1.1 times, preferably at least 1.2 times, or even more than 1.3 times. For example, the cross-sectional diameter Wi of the cavity opening 13i in the embodiment shown is around 5.5 mm, while the channel width Wh immediately before the cavity opening 13i is around 7 mm. The wider the flow channels 11, 12 before and / or after the cavity opening 13i, the more uniform the flow across the membrane.

[0018] In another or further embodiment, the flow channel 11, 12 starts with a first channel width Wg at the input connector and / or output connector side and gradually widens towards the cavity opening 13i to a second channel width Wh, which is at least two, three or more times larger than the first channel width Wg. For example, the initial channel width Wh can be on the same order as the channel height (not shown here), for example around 1 mm in the embodiment shown, while the channel width Wh just before the cavity opening 13i can be around 7 mm. By gradually widening the channel width, a more predictable / uniform flow across the membrane can be achieved. For example, the gradually widening can be quantified as the increase in width (ΔW) per unit length (ΔL) along the flow direction (Y) (through the center of the channel), with the ratio (ΔW / ΔL) preferably being less than 1. For example, in the illustrated embodiment, (Wh-Wg) / Lgh ≈ (7mm-1mm) / 10mm = 0.6.

[0019] In some embodiments, the width Wh of the flow channels 11, 12 at least immediately before the cavity opening 13i (here in direction X) is much larger than the respective heights (here in direction Z) of the flow channels 11, 12, e.g., at least 2, 3, 4, 5, or more times larger. For example, in the illustrated embodiment, the width Wh is about 7 times larger than the heights (not shown here). The smaller the height compared to the widths of the channels at the overlap position, the more membrane surface can be covered by the flow for interaction with the components of the flow without the need to increase the total flow rate.

[0020] 2A-2C show various schematic diagrams of the microfluidic device 100. Preferably, the microfluidic device 100 is relatively small, for example with a typical length Lc, width Wc, and / or height Hc of the housing 10 between 0.5 centimeters and 10 centimeters, preferably less than 5 or 6 centimeters. For example, in this embodiment, the housing has a length Lc of about 4 centimeters, a width Wc of about 2 centimeters, and a height Hc of about 1 centimeter. Of course, other sizes can be envisioned. The flow channels can be even smaller, for example with a typical minimum diameter of less than 1 millimeter.

[0021] FIG. 3A shows a cutaway / exploded view of the microfluidic device 100 with various components. FIG. 3B shows another cutaway view enlarged around the cavity opening 13i between the flow channels 11, 12. In a preferred embodiment described herein, the microfluidic device 100 comprises a fastening ring 14. In one embodiment, for example as shown, the fastening ring 14 comprises a connecting structure 14c. For example, the connecting structure 14c is configured to engage with a corresponding connecting structure 13c of the housing inside the access cavity 13. Thus, the fastening ring 14 can be used to hold the sample membrane M in place over the cavity opening 13i. Typically, the membrane M is exposed to the respective fluid flows F1, F2 through the flow channels 11, 12 on both sides of the membrane M during use.

[0022] In one embodiment, the housing 10 extends with a cavity seat 13s that forms a seat around the cavity opening 13i between the overlapping areas of the flow channels 11, 12 to hold the membrane M directly or indirectly between the cavity seat 13s and the fastening ring 14. For example, the membrane M can be placed directly on the cavity seat 13s. For example, the fastening ring 14 can fasten the membrane M directly. However, preferably, a sealing ring 16 is placed on either or both sides of the membrane M. In one embodiment, for example as shown, at least one sealing ring 16 is placed between the membrane M and the fastening ring 14 during use. This may improve sealing and / or prevent the fastening ring from damaging the membrane M (e.g., cutting into the membrane M). Other or further structures may also be placed between the fastening ring 14 and the membrane M and / or between the membrane M and the cavity seat 13s. For example, a mesh can be provided to help further support the membrane M. In one embodiment, the cavity opening 13i on one side of the membrane M and the ring opening 14i through the fastening ring 14 on another side of the membrane M are configured to expose the membrane M to the respective fluid flows F1, F2 in the flow channels 11, 12 during use.

[0023] In a preferred embodiment, the fastening ring 14 is configured to form a part of the first flow channel 11. For example, the fastening ring 14 is configured to direct the first fluid flow over the fastening ring 14 to the ring opening 14i between the fastening ring 14 and the bottom 15b of the cap 15 sealing the access cavity 13. In some embodiments, the structure surrounding the opening is relatively thin near the opening, preferably with a gradual transition from the flow channels 11, 12. In one embodiment, the fastening ring 14 has an inner thickness at the opening 14i along its inner diameter and a second thickness that is an outer thickness at its outer diameter, the outer thickness being greater than the inner thickness, for example by at least a factor of two. Preferably, the fastening ring 14 has a sloped and / or rounded transition 14r between its inner and outer diameters, the transition 14r gradually thinning toward the center of the transition 14r. Thus, the flow in the first flow channel 11 can be guided gradually closer to the top of the membrane M.

[0024] In another or further embodiment, the cavity seat 13s has an inner thickness at its opening 13i along its inner diameter and an outer thickness remote from the opening, the outer thickness being greater than the inner thickness, for example by a factor of at least two. Preferably, the cavity seat 13s is provided with a sloping and / or rounded transition 11r that gradually thins towards the cavity opening 13i. Thus, the flow in the second flow channel 12 can alternatively or additionally be guided gradually closer to the bottom of the membrane M.

[0025] In one embodiment, the connection structure 13c of the housing inside the access cavity 13 surrounds the cavity seat 13s. In another or further embodiment, the connection structure 13c of the housing inside the access cavity 13 includes a set of fastening fingers having hooks configured to fasten around the edge of the fastening ring 14. In some embodiments, each of the fingers is configured to pivot radially outward to allow insertion of the fastening ring and then pivot back inward with the hooks engaging corresponding structures, e.g. edges, around the fastening ring 14. For example, at least two, preferably three, four, or more fastening fingers are circumferentially located around the cavity opening 13i. In some embodiments described later with reference to FIG. 4B, the connection structure, e.g. fingers, may be omitted at least in the path of the first flow channel 11 to allow the connecting channel 14a to pass through the fastening ring 14. For example, the fingers can be located only on the sides, or the fastening ring 14 can be retained by other means.

[0026] In one embodiment, the connection structure 13c of the housing, e.g., a fastening finger, protrudes from the hollow seat 13s. In another or further embodiment, a sealing ring 16 is disposed between the hollow seat 13s and the fastening ring 14 together with the membrane M. The fastening ring may comprise a relatively hard material, whereas the sealing ring 16 preferably comprises a (more) elastic material, e.g., rubber. In some embodiments, the sealing ring 16 when held by the fastening ring 14 is configured to prevent fluid from passing around the sealing ring 16. In other or further embodiments, the sealing ring 16 is configured to pass fluid only through the opening 16i of the sealing ring 16 (this opening is covered by the membrane M during use, and therefore substances in the fluid may permeate through the membrane M).

[0027] Preferably, the ring opening 14i through the fastening ring 14 and the cavity opening 13i between the flow channels 11, 12 have substantially matching interconnection diameters Wi, for example offset by less than 30 percent, preferably less than 20 percent, or less than 10 percent. The same is true for the opening 16i through the sealing ring 16, which is preferably located between the ring opening 14i and the cavity opening 13i. In a preferred embodiment, the opening is circular, but other shapes can be envisioned. Typically, the sealing ring 16 is configured to abut (in use) the membrane M. In some embodiments, such as shown in Figures 1-3, the membrane M is located between the sealing ring 16 and the cavity seat 13s. Other or further configurations can be envisioned, for example as described below.

[0028] 4A shows a microfluidic device 100 in which the membrane M is disposed between the sealing ring 16 and the fastening ring 14. This configuration may have the advantage of lifting the membrane M closer to the first fluid flow F1. For example, the thickness of the sealing ring 16 may be comparable to the thickness of the fastening ring 14, and thus the membrane M may be more centrally disposed between the respective flow channels 11, 12.

[0029] In one embodiment, a first channel height M1 between the location of the membrane M fastened inside the device and the opposing wall of the first flow channel 11 is similar to within a factor of 2, preferably within a factor of 1.5, as a second channel height M2 between the location of the membrane M and the opposing wall of the second flow channel 12 on the opposite side of the membrane M. The more similar the respective heights of the channels on either side of the membrane are, the more similar their respective maximum flow distances and corresponding efficiencies with which the flow moieties interact with the membrane will be.

[0030] Other or further components may be disposed between the membrane M and the cavity seat 13s and / or between the sealing ring 16 and the cavity seat 13s. In a preferred embodiment, a mesh 17 is provided that abuts the membrane M to improve its structural integrity. For example, the mesh 17 may provide a relatively open structure that does not substantially affect the permeability of the membrane M. Preferably, the mesh is provided at least below the membrane M. Alternatively or additionally, a mesh may be provided above the membrane M.

[0031] FIG. 4B shows the microfluidic device 100, in which the fastening ring 14 comprises a channel 14a. In a preferred embodiment, such as that shown, the fastening ring 14 has a channel 14a that forms a part of the first flow channel 11 through the ring 14. For example, the fastening ring 14 is configured to form a part of the first flow channel 11 to guide the first fluid flow F1 through the fastening ring 14 via the channel 14a to the ring opening that exposes the membrane M. As an advantage, this allows the fastening ring 14 to be thicker without obstructing the first flow channel 11 and without increasing the flow distance M1. Furthermore, the fastening ring 14 can be optionally pressed and / or held in place by the cap 15. Optionally, the connection structure 13c of the housing inside the access cavity 13 can be omitted.

[0032] In some embodiments, the flow distance M1 to the membrane can be further reduced, for example, by the shape of the channel 14a protruding toward the membrane. In one embodiment, the channel height M1, M2 between the membrane M fastened inside the device and the facing wall of each of the first and / or second flow channels 11, 12 is less than 1 millimeter, preferably less than 0.8 mm, less than 0.6 mm, or even less than 0.5 mm. The smaller the channel height M1, M2 at the membrane, the closer the flow distance is, and the more effectively the flow can interact with the membrane.

[0033] In other or further embodiments, the channel height M1, M2 of each of the flow channels 11, 12 at the location of the membrane M is similar, for example within a factor of 2, preferably within a factor of 1.5 or less, to the channel height H1, H2 of the respective flow channels 11, 12 before and / or after the fastening ring 14. Keeping the channel heights relatively constant may promote more predictable flow.

[0034] FIG. 5A shows a microfluidic device 100 in which both flow channels 11, 12 are configured to reduce the channel height at the location of the membrane M. In one embodiment, the first flow channel 11 and / or the second flow channel 12 are provided with respective ridges ΔH1, ΔH2 toward the access cavity 13 in order to reduce the respective channel heights H1, H2 at the location of the access cavity 13 and direct the respective flows toward the membrane M. In another or further embodiment, the ridges can be formed as part of the housing (e.g., ΔH2 in the second flow channel 12 as shown here). In another or further embodiment, the ridges can be formed in the cap 15 (e.g., ΔH1 in the first flow channel 11 as shown here). In another or further embodiment, the ridges can be formed in the fastening ring 14 (e.g., as shown in FIG. 4B). For example, the distance between the top of the first flow channel 11 and the membrane without the ridges can typically be 2-2.5 mm. By adding the ridge or bulge, this can direct the flow closer to the membrane, for example less than 1 millimeter, or even less than 0.8 mm, for example, to be comparable or the same as the channel height (H1) before and / or after the membrane.

[0035] FIG. 5B illustrates a system 1000 (not to scale) and method for using the microfluidic device 100 described herein.

[0036] Aspects of the disclosure may be embodied as a system including the microfluidic device 100 described herein. In one embodiment, the system includes a pump 110, preferably peristaltic. In another or further embodiment, the system includes at least a first and a second reservoir 121, 122. Channels or tubes may be used to interconnect the microfluidic device 100, the pump 110, and the reservoirs 121, 122 (e.g., via either a first set of connectors 11a, 11b or a second set of connectors 12a, 12b, see FIG. 1A). Preferably, a first flow F1 through the first reservoir 121 is separate from a second flow F2 through the second reservoir 122 (other than through the membrane M held inside the microfluidic device 100).

[0037] The microfluidic device 100 or system 1000 described herein can be used to analyze, for example, the permeability of a substance through a membrane M. In use, the membrane M is placed between the first flow channel 11 and the second flow channel 12 in the cavity opening 13i. In some embodiments, a first flow F1 is passed through the first flow channel 11 via the first reservoir 121, and a second flow F2 is passed through the second flow channel 12 via the second reservoir 122. For example, the substance can be disposed in at least one of the fluid flows F1, F2, for example in different amounts. In some embodiments, the respective contents of the substances in the first and / or second reservoirs 121 are measured and / or monitored to determine the exchange of the substances through the membrane M.

[0038] A typical flow can be set, for example, between 1 and 100 milliliters per hour, for example depending on the channel height. For example, components can be added to the first reservoir 121 and measured in the second reservoir 122, for example by taking a sample from the reservoir. For example, the first reservoir 121 can be used to act as a lumen (mimicking a lumen), while the second reservoir 122 can be used to act as a blood vessel. For example, the components can include nutrients, drugs, etc. For example, the membrane M comprises a tissue sample, a scaffold, for example a 3D structure with cells, or another membrane, for example plastic or polyester. Thus, the microfluidic device 100 or system 1000 can be used to test various membranes.

[0039] When interpreting the appended claims, the word "comprising" does not exclude the presence of elements or operations other than those recited in a given claim, the word "a" or "an" preceding an element does not exclude the presence of a plurality of that element, and reference signs in the claims do not limit the scope of those claims, and it should be understood that several "means" may be represented by the same or different items or implemented as structures or functions, and that any of the disclosed devices or parts thereof may be combined with each other or divided into further parts, unless specifically stated otherwise. When a claim refers to another claim, this may mean synergistic advantages realized by the combination of the respective features. However, the mere fact that certain measures are recited in mutually different claims does not mean that the combination of those measures cannot be used advantageously. Thus, the present embodiment may include all functional combinations of claims, and each claim may in principle refer to any preceding claim, unless the context clearly precludes it.

Claims

1. A microfluidic device (100) for analyzing the permeability of substances through a membrane (M), the substances being disposed in respective fluid flows (F1, F2), the microfluidic device (100) comprising: A housing (10); a first flow channel (11) for passing a first fluid flow (F1) through the housing (10) between a first input connector (11) and a first output connector (11b); a second flow channel (12) for passing a second fluid flow (F2) through the housing (10) between a second input connector (12a) and a second output connector (12b); an access cavity (13) extending from the outside into the housing (10) through the first flow channel (11) and into the second flow channel (12) for accessing the interior of the housing (10) for placing the membrane (M) over a cavity opening (13i) that forms a dedicated fluid interconnection between the overlapping areas of the flow channels (11, 12); a fastening ring (14) having a connection structure (14c) configured to engage with a corresponding connection structure (13c) of the housing inside the access cavity (13), for holding the sample membrane (M) in position over the cavity opening (13i) while the membrane (M) is exposed to respective fluid flows (F1, F2) through the flow channels (11, 12) on both sides of the membrane (M) during use, wherein the cavity opening (13i) on one side of the membrane (M) and a ring opening (14i) through the fastening ring (14) on another side of the membrane (M) are configured to expose the membrane (M) to the respective fluid flows (F1, F2) in the flow channels (11, 12); wherein the fastening ring (14) is configured to form a portion of the first flow channel (11) that is exposed to the first fluid flow (F1).

2. 2. The microfluidic device of claim 1, wherein the fastening ring (14) is configured to form part of the first flow channel (11) and comprises a sloped and / or rounded transition (14r) between an inner diameter and an outer diameter of the fastening ring (14), the transition (14r) gradually thinning towards the center of the transition (14r) where the membrane (M) should be exposed to the first fluid flow (F1).

3. 3. The microfluidic device (100) of claim 1 or 2, wherein an integral part of the housing (10) extends with a cavity seat (13s) forming a seat around the cavity opening (13i) between the overlapping areas of the flow channels (11, 12) and directly or indirectly holds the membrane (M) between the cavity seat (13s) and the fastening ring (14), wherein the connection structure (13c) of the housing inside the access cavity (13) surrounds the cavity seat (13s) and the connection structure (13c) of the housing protrudes from the cavity seat (13s).

4. 4. The microfluidic device (100) according to claim 1, wherein the cavity seat (13s) is provided with a sloped and / or rounded transition (11r) that gradually thins towards the cavity opening (13i) where the membrane (M) should be exposed to the second fluid flow (F1).

5. 5. The microfluidic device (100) of claim 3 or 4, wherein a sealing ring (16) of elastic material is arranged together with the membrane (M) between the cavity seat (13s) and the fastening ring (14), the sealing ring (16) being configured to abut against the membrane (M).

6. 6. The microfluidic device (100) according to any one of claims 1 to 5, wherein the fastening ring (14) is configured to direct the first fluid flow (F1) to the ring opening (14i) via a channel (14a) passing through the fastening ring (14) and / or to direct the first fluid flow (F1) over the fastening ring (14) to the ring opening (14i) between the fastening ring (14) and a bottom (15b) of a cap (15) sealing the access cavity (13).

7. 7. The microfluidic device (100) of claim 1, wherein the connection structure (13c) of the housing inside the access cavity (13) comprises a set of fastening fingers having hooks configured to fasten around an edge of the fastening ring (14), each of the fingers being configured to pivot radially outward to allow insertion of the fastening ring and then return inward with the hooks engaging corresponding structure around the fastening ring (14), wherein the fastening fingers are circumferentially positioned around the cavity opening (13i).

8. The microfluidic device (100) according to any one of the preceding claims, wherein a mesh (17) is provided between the membrane (M) and the cavity opening (13i).

9. 9. The microfluidic device (100) according to any one of claims 1 to 8, wherein the flow channels (11, 12) have a channel width (Wh) immediately before or after the cavity opening (13i), wherein the channel width (Wh) is at least 1.1 times greater than the cross-sectional diameter (Wi) of the cavity opening (13i) between the flow channels (11, 12).

10. 10. The microfluidic device (100) of claim 1, wherein the flow channels (11, 12) start with a first channel width (Wg) at the input and / or output connector side and gradually widen towards the cavity opening (13i) to a second channel width (Wh), wherein the second channel width (Wh) is at least twice as large as the first channel width (Wg).

11. A microfluidic device (100) according to any one of claims 1 to 10, wherein the width (Wh) of the flow channels (11, 12) at least immediately preceding the cavity opening (13i) is at least twice as large as the respective height of the flow channels (11, 12).

12. 12. The microfluidic device (100) of claim 1, wherein a first channel height (M1) between a position of the membrane (M) fastened inside the device and an opposing wall of the first flow channel (11) is similar to within a factor of two a second channel height (M2) between a position of the membrane (M) and an opposing wall of the second flow channel (12) on the opposite side of the membrane (M).

13. 13. The microfluidic device (100) according to any one of claims 1 to 12, wherein the first flow channel (11) and / or the second flow channel (12) are provided with respective ridges (ΔH1, ΔH2) towards the access cavity (13) in order to reduce the respective channel heights (H1, H2) at the location of the access cavity (13) and to direct the respective flows towards the membrane (M).

14. 1. A system comprising: A microfluidic device (100) according to any one of claims 1 to 13, A pump (110), First and second reservoirs (121, 122), and A plurality of channels interconnecting the microfluidic device (100), the pump (110), and a plurality of reservoirs (121, 122) (e.g., with reference to FIG. 1A, via either a first set of connectors 11a, 11b, or a second set of connectors 12a, 12b). It is equipped with a first flow (F1) through the first reservoir (121) is separated from a second flow (F2) through the second reservoir (122) except through the membrane (M) retained within the microfluidic device (100); The system.

15. A method of using a microfluidic device (100) or a system (1000) according to any one of claims 1 to 14 for analyzing the permeability of a substance through a membrane (M), comprising: placing the membrane (M) within the cavity opening (13i) between the first flow channel (11) and the second flow channel (12); Passing a first flow (F1) having said substance through a first reservoir (121) into said first flow channel (11); passing a second flow (F2) through the second flow channel (12) via the second reservoir (122); and monitoring the respective contents of said substances in said first and / or second reservoirs (121) to determine the exchange of said substances across said membrane (M); The method comprises:

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