Microfluidic device for analyzing a membrane

Abstract

A microfluidic device for analyzing the permeability of a substance through a membrane. Flow channels pass respective fluid streams containing a substance between respective connectors through a housing. An access cavity extends from outside the housing through a first flow channel and into a second flow channel to access the interior of the housing. A membrane can be placed over a cavity opening that forms a fluid interconnection between overlapping regions 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 streams passing through the flow channels on either side of the membrane.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to microfluidic devices, such as a slice or flow cell, and methods of 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 piece of tissue explant can comprise different cell types that can be distinguished from a cell monolayer or bilayer, or a cell suspension injected into a slice. BACKGROUND

[0002] WO 2012 / 118799 A2 describes systems and methods for culturing and / or maintaining intestinal cells, tissues and / or in vitro organoids. The cultured cells, tissues and / or organoids can mimic or reproduce natural intestinal epithelial structure and behavior and support co-culturing of intestinal microbiota.

[0003] WO 2014 / 069995 A1 describes a vial for preserving a piece of epithelial tissue. More specifically, it relates to a vial that is easy to assemble and enables horizontal alignment of the tissue sample. The prior art also relates to a device comprising the vial, a method for producing the device, and a plurality of said devices enabling medium flux measurements of absorption, transport and / or secretion across epithelial tissue.

[0004] EP 2 233 924 A1 describes a biological slice assembly comprising a semipermeable membrane and a test method for performing cell-based tests using the biological slice assembly. Monitoring the ability of biological cells to migrate through tight layers of other cells and tissues is of great importance for understanding disease mechanisms and developing therapeutic drugs. In this prior art, a method for measuring the migration of sample cells in an assembly comprising a plurality of fluidly connected compartments is provided, wherein the method comprises introducing an analyte into at least one analyte-receiving compartment, introducing sample cells into at least one sample cell-receiving compartment, wherein the sample cells are separated from the analyte by a semipermeable membrane, and subjecting the analyte and / or the sample cells to controlled flow conditions. In this way, the assembly can comprise two compartments in the form of a channel bisected by a semipermeable membrane, or comprising a channel and a well / chamber. Alternatively, the assembly can comprise a plurality of compartments in the form of two or more channels, or even comprising two or more channels and wells / chambers. The compartments are fluidly connected over at least part of the surface / length of the compartments. In this way, the analyte-receiving compartment is separated from the sample cell-receiving compartment by a semipermeable membrane.

[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 gut. However, such cultured cells can not have the full complement of intestinal epithelial subtypes and genetic variations of actual epithelial tissue. Another or further challenge can involve mounting an epithelial tissue sample, e.g., where the sample does not adhere sufficiently to the sides of a membrane. For example, leakage can occur due to the difficulty of attaching the tissue sample to both sides by proliferation (cell growth). Other or further challenges can involve reliably mounting and dismounting a membrane between channels inside a device. SUMMARY

[0006] Aspects of the present disclosure relate to a microfluidic device for analyzing the permeability of a substance through a (sample) membrane, e.g., to study different properties of an epithelial barrier, such as the permeability of the epithelial barrier to different biological and pharmacological substances. The microfluidic device comprises a housing having flow channels for passing respective fluid streams (e.g., two parallel flows) 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 for placing a membrane (e.g., a biological barrier) over a cavity opening. Preferably, the cavity opening forms an exclusive fluid interconnection between overlapping regions of the flow channels. A clamping ring (preferably forming part of the flow channels) can be used to hold the sample membrane in place over the cavity opening, while the membrane is exposed in use to the respective fluid streams of the flow channels on both sides of the membrane. The microfluidic device can be used in a system comprising pumps and respective reservoirs connected to the channels. Use of the microfluidic device or system can comprise placing a membrane in the cavity opening between a first flow channel and a second flow channel, and causing respective flows to pass through the flow channels on both sides of the membrane via the respective reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0007] These and other features, aspects, and advantages of the above-described apparatuses, systems, and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings, where:

[0008] FIG. 1A A perspective view of a microfluidic device is shown, enclosed by a cover;

[0009] FIG. 1B Another view of the microfluidic device is shown, without the cover, to show a cavity that extends into the housing and interconnects with the channels;

[0010] FIGS. 2A-2C Various schematic views of the microfluidic device are shown;

[0011] FIG. 3A A cross-sectional view / explosion view of the microfluidic device is shown, with its various components;

[0012] FIG. 3B Another cross-sectional view showing enlargement around the cavity opening between flow channels is shown;

[0013] FIG. 4A A microfluidic device is shown in which a membrane is disposed between a seal ring and a clamp ring;

[0014] FIG. 4B A microfluidic device is shown in which the clamp ring includes a channel;

[0015] FIG. 5A A microfluidic device is shown in which two flow channels are configured to reduce the channel height at the location of the membrane;

[0016] FIG. 5B A system (not to scale) and a method for using a microfluidic device as described herein are shown. DETAILED DESCRIPTION

[0017] The terminology used to describe the specific embodiments is not intended to be limiting of the present application. 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 term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, but do not preclude the presence or addition of one or more other features. It will be further understood that, when a particular step of a method is referred to as following another step, the particular step can directly follow the other step, or one or more intermediate steps can be performed before performing the particular step, unless otherwise stated. Also, it is to be understood that the connection between structures or components, when described, can be established directly or through intermediate structures or components, unless otherwise stated.

[0018] The present application is more fully described in the following reference to the drawings, in which embodiments of the present application are shown. In the drawings, the absolute and relative sizes of systems, components, layers, and regions can be exaggerated for clarity. Embodiments can be described with reference to schematic and / or cross-sectional illustrations of possibly idealized embodiments and intermediate structures of the present application. Identical reference numerals in different drawings denote the same elements. Relative terms as well as derivatives thereof should be construed to refer to the appropriate one or an item depicted as at the time of the referring statement being made. These relative terms are intended to encompass different positional relationships to the claimed invention as depicted in the drawings and described in the written description. Unless otherwise stated, the system is not required to be constructed or operated in a particular orientation.

[0019] FIG. 1AA perspective view of the microfluidic device 100 closed by the lid 15 is shown. In an embodiment, for example, as shown, the microfluidic device 100 has a housing forming at least two flow channels 11, 12. Three or more channels (not shown) are also conceivable. In the shown embodiment, the microfluidic device 100 is translucent, so that the channels 11, 12 of the housing 10 and possibly the contained matter of the channels are visible. This can enable easy viewing of the flow inside the housing without opening the lid. Other materials, for example opaque materials, can also be used. Preferably, the housing 10 comprises, for example, consists mainly of a material such as plastic. In a preferred embodiment, for example, as shown here, the device is manufactured by 3D printing. For example, the device is made of a printable (cured) material. Other manufacturing methods and materials are also conceivable.

[0020] FIG. 1B Another view of the microfluidic device 100 without the lid is shown to illustrate the cavity 13, which extends into the housing 10 and interconnects the channels 11, 12. In some embodiments, the channels 11, 12 extend between 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 comprises a short tube shape 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 an edge to prevent the flow tubes from slipping off. Alternatively, or in addition to protruding connectors, inwardly extending (concave) connectors (not shown) are also conceivable. For example, the flow tubes or their connection parts can be inserted into the connectors of the device housing. Inward connectors can also be tapered and / or provided with an edge. Other types of connections between the device 100 and the respective flow tubes or other channels are also conceivable.

[0021] In some embodiments, for example, as shown, the connectors 11a, 12a on the same face of the housing can be offset from the central plane in the lateral direction (X). This can provide more space to place the connectors and / or to connect an external flow circuit, especially if the flow channels 11, 12 extend close together in the height direction (Z). In some embodiments, for example, as shown, the flow channels 11, 12 are symmetrical before and after entering the cavity 13. For example, the path of the channels can be rotationally symmetrical, as in the shown embodiment, and / or mirror symmetrical.

[0022] In an aspect, the present disclosure provides a microfluidic device 100 for analyzing the permeability of a substance through a (sample) membrane M. For example, the substance is arranged in a respective fluid flow F1, F2. Typically, the microfluidic device 100 comprises a housing 10 with flow channels 11, 12. In some embodiments, the first flow channel 11 is configured to pass the first fluid flow F1 through the housing 10 between a first input connector 11a and a first output connector 11b. In other or further embodiments, the second flow channel 12 is configured to pass the second fluid flow F2 through the housing 10 between a second input connector 12a and a second output connector 12b.

[0023] In preferred embodiments, the device comprises an access cavity 13 that extends from the outside through the first flow channel 11 into the housing 10 and into the second flow channel 12. Thus, the cavity can be used to access the interior of the housing 10 to place the membrane M over the cavity opening 13i. Most preferably, the cavity opening 13i forms a (exclusive) fluidic interconnection between the overlapping regions of the flow channels 11, 12.

[0024] In preferred embodiments, the access cavity 13 can be opened and / or closed by a lid 15. Most preferably, the lid 15 can be reversibly removed to access the cavity and, for example, to place or replace the membrane M. For example, the lid 15 and / or the housing comprise an elastic material, such as rubber, at the seal between the lid and the housing. Other elastic structures can also be used, or the lid can be screwed onto the housing.

[0025] In embodiments, 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) directly before and / or after the cavity opening 13i that 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 the cross-sectional diameter Wi of the cavity opening 13i between the flow channels 11, 12. For example, in the shown embodiment, the cross-sectional diameter Wi of the cavity opening 13i is about 5.5 mm, while the channel width Wh directly before the cavity opening 13i is about 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.

[0026] In another or further embodiment, the flow channel 11, 12 gradually widens from a first channel width Wg (which is on one side of the input connector and / or output connector) to a second channel width Wh towards the cavity opening 13i, wherein the second channel width Wh is greater than the first channel width Wg, at least twice, three times or more. For example, the initial channel width Wh can be similar to the channel height (not shown here), e.g. about 1 mm in the illustrated embodiment, while the channel width Wh immediately before the cavity opening 13i can be about 7 mm. By gradually widening the width of the channel, a more predictable / more uniform flow through the membrane can be achieved. For example, the gradual widening can be quantified as an amount of width increase (AW) per unit length (AL) along the direction of flow (Y) (through the center of the channel), wherein the ratio (AW / AL) is preferably less than one. For example, in the illustrated embodiment (Wh-Wg) / Lgh ~ (7mm-1mm) / 10mm = 0.6.

[0027] In some embodiments, the width Wh (here along direction X) of the flow channel 11, 12 at least immediately before the cavity opening 13i is much greater than the respective height (here along direction Z) of the flow channel 11, 12, e.g. at least twice, three times, four times, five times or more than the respective height of the flow channel. For example, in the illustrated embodiment, the width Wh is about seven times the height (not shown here). The smaller the height compared to the width of the channel at the overlap location, the more of the membrane surface can be covered by the flow to interact with its components without increasing the total flow.

[0028] FIGS. 2A-2C Various schematic views of the microfluidic device 100 are shown. Preferably, the microfluidic device 100 is relatively small, e.g. the typical length Lc, width Wc and / or height Hc of the housing 10 is between half a centimeter and ten centimeters, preferably less than five or six centimeters. For example, in the present embodiment, the housing has a length Lc of about four centimeters, a width Wc of about two centimeters and a height Hc of about one centimeter. Of course, other dimensions are also conceivable. The flow channels can be even smaller, e.g. typically a minimum diameter of less than one millimeter.

[0029] FIG. 3A A cross-sectional view / exploded view of the microfluidic device 100 with its various components is shown. FIG. 3BAnother cross-sectional view is shown, magnified around the cavity opening 13i between the flow channels 11, 12. As described herein, in preferred embodiments, the microfluidic device 100 includes a clamping ring 14. In one embodiment, for example, as shown, the clamping ring 14 includes a connection structure 14c. For example, the connection structure 14c is configured to engage a corresponding connection structure 13c of the housing inside the entrance to the cavity 13. Thus, the clamping ring 14 can be used to hold the sample membrane M in place over the cavity opening 13i. Typically, the membrane M is exposed, in use, to respective fluid flows Fl, F2 through the flow channels 11, 12 on either side of the membrane M.

[0030] In one embodiment, the housing 10 extends with a cavity seat 13s forming a platform around the cavity opening 13i between the overlapping regions of the flow channels 11, 12 to hold the membrane M directly or indirectly between the cavity seat 13s and the clamping ring 14. For example, the membrane M can be placed directly on the cavity seat 13s. For example, the clamping ring 14 can clamp directly on the membrane M. Preferably, however, a sealing ring 16 is arranged on one or both sides of the membrane M. In one embodiment, for example, as shown, in use, at least one sealing ring 16 is arranged between the membrane M and the clamping ring 14. This can improve sealing and / or prevent the clamping ring from damaging (e.g., cutting into) the membrane M. Furthermore, other or further structures can be arranged between the clamping 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 clamping ring 14 on the other side of the membrane M) are configured, in use, to expose the membrane M to respective fluid flows Fl, F2 in the flow channels 11, 12.

[0031] In preferred embodiments, the clamping ring 14 is configured to form part of the first flow channel 11. For example, the clamping ring 14 is configured to direct the first fluid flow past the top of the clamping ring 14 to the ring opening 14i between the bottom 15b of the lid 15 (sealing against the entrance to the cavity 13) and the clamping ring 14. In some embodiments, the structures around the openings are relatively thin near the openings, preferably, these structures include structures that gradually transition from the flow channels 11, 12. In one embodiment, the clamping ring 14 has an inner thickness along its inner diameter at its opening 14i and an outer thickness second thickness along its outer diameter, wherein the outer thickness is greater than the inner thickness, for example, the outer thickness is at least twice the inner thickness. Preferably, the clamping ring 14 includes a sloped and / or rounded transition 14r between its inner diameter and outer diameter that tapers towards its center. Thus, the flow in the first flow channel 11 can be diverted to gradually approach the membrane M at the top.

[0032] In other or further embodiments, the cavity seat 13s has an inner thickness along its inner diameter at its opening 13i, and an outer thickness distal from the opening, wherein the outer thickness is greater than the inner thickness, for example at least twice the inner thickness. Preferably, the cavity seat 13s comprises a tapered and / or rounded transition 11r that tapers towards the cavity opening 13i. Accordingly, the flow in the second flow channel 12 can alternatively or additionally be diverted to gradually approach the membrane M at the bottom.

[0033] In one embodiment, the connection structure 13c of the housing inside the entrance to the cavity 13 surrounds the cavity seat 13s. In another or further embodiment, the connection structure 13c of the housing inside the entrance to the cavity 13 comprises a set of clamping fingers with hooks configured to clamp around the edge of the clamping ring 14. In some embodiments, each finger is configured to pivot radially outwards to enable the clamping ring to be inserted, and then back inwards, with the hooks engaging a corresponding structure, for example the edge, of the clamping ring 14. For example, at least two, preferably three, four or more clamping fingers are positioned circumferentially around the cavity opening 13i. In some embodiments discussed later with reference to FIG. 4B In some embodiments discussed later with reference to

[0034] In one embodiment, the connection structure 13c of the housing, for example the clamping fingers, protrude from the cavity seat 13s. In another or further embodiment, a sealing ring 16 is arranged between the cavity seat 13s and the clamping ring 14, together with the membrane M. While the clamping ring can comprise a relatively hard material, the sealing ring 16 preferably comprises a (more) elastic material, such as rubber. In some embodiments, the sealing ring 16 is configured to prevent fluid from passing around the sealing ring 16 when held by the clamping ring 14. In other or further embodiments, the sealing ring 16 is configured to only allow fluid to pass through an opening 16i in the sealing ring 16 (the opening of the sealing ring is covered by the membrane M in use, such that substances in the fluid can permeate through the opening of the sealing ring).

[0035] Preferably, the ring opening 14i of the clamping ring 14 and the cavity opening 13i between the flow channels 11, 12 have substantially matching mutual connection diameters Wi, for example with a deviation of less than thirty percent, preferably less than twenty percent or less than ten percent. Similarly, the opening 16i of the sealing ring 16 is preferably arranged between the ring opening and the cavity opening of the clamping ring. Although in the preferred embodiment the openings are circular, other shapes are also conceivable. Typically, the sealing ring 16 is configured to abut (in use) against the membrane M. In some embodiments, for example as shown in Figs. 1-3, the membrane M is arranged between the sealing ring 16 and the cavity seat 13s. Further, other or further configurations are also conceivable, for example as discussed below.

[0036] FIG. 4A A microfluidic device 100 is shown, wherein the membrane M is arranged between the sealing ring 16 and the clamping ring 14. This configuration can have the advantage of lifting the membrane M closer to the first fluid flow Fl. For example, the thickness of the sealing ring 16 can be similar to the thickness of the clamping ring 14, so that the membrane M can be arranged more centrally between the respective flow channels 11, 12.

[0037] In one embodiment, the first channel height Ml (between the position of the membrane M clamped inside the device and the opposing wall of the first flow channel 11) is similar to the second channel height M2 (between the position of the membrane M and the opposing wall of the second flow channel 12) across the membrane, within a factor of two, preferably within a factor of one and a half. The more similar the respective heights of the channels on both sides of the membrane, the more similar the respective maximum flow distances and the corresponding efficiencies of the portion of the flow interacting with the membrane.

[0038] Further, other or further components can also be arranged between the membrane M and the cavity seat 13s and / or between the sealing ring 16 and the cavity seat 13s. In the preferred embodiment, a mesh 17 is provided in close proximity to the membrane M to improve the structural integrity of the membrane. For example, the mesh 17 can 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 in addition, the mesh can be provided above the membrane M.

[0039] FIG. 4BA microfluidic device 100 is shown in which the clamping ring 14 includes a channel 14a. In a preferred embodiment, for example, as shown, the clamping ring 14 has a channel 14a through which the clamping ring forms a portion of the first flow channel 11. For example, the clamping ring 14 is configured to form a portion of the first flow channel 11 to direct the first fluid flow Fl through the clamping ring 14 via the channel 14a to a ring opening that exposes the membrane M. Advantageously, the clamping ring 14 can thus be thicker without obstructing the first flow channel 11 and without increasing the flow distance Ml. Further, the clamping ring 14 can optionally be urged and / or held in place by the cover 15. Optionally, the connecting structure 13c of the housing that enters inside the cavity 13 can be omitted.

[0040] In some embodiments, for example, by the shape of the channel 14a that protrudes towards the membrane, the flow distance Ml to the membrane can be further reduced. In embodiments, the respective channel height Ml, M2 (the position of the membrane M clamped inside the device between the opposing walls of the respective first flow channel 11 and / or second flow channel 12) is less than one millimeter, preferably less than 0.8 mm, less than 0.6 mm, or even less than half a millimeter. The smaller the channel height Ml, M2 at the position of the membrane, the closer the flow distance, the more effectively the flow can interact with the membrane.

[0041] In other or further embodiments, the respective channel height Ml, M2 of the respective flow channel 11, 12 at the position of the membrane M is similar, for example, within two times, preferably within one and a half times or less, to the channel height Hl, H2 of the respective flow channel 11, 12 before and / or after the clamping ring 14. Keeping the channel height relatively constant can facilitate more predictable flow.

[0042] FIG. 5A A microfluidic device 100 is shown in which both flow channels 11, 12 are configured to reduce the channel height at the position of the membrane M. In one embodiment, the first flow channel 11 and / or the second flow channel 12 is provided with a respective protrusion AHl, AH2 towards the entry cavity 13 to reduce the respective channel height Hl, H2 at the position of the entry cavity 13 and to divert the respective flow towards the membrane M. In another or further embodiment, the protrusion can be formed as part of the housing (for example, AH2 in the second flow channel 12 as shown here). In another or further embodiment, the protrusion can be formed in the cover 15 (for example, AHl in the first flow channel 11 as shown here). In another or further embodiment, the protrusion can be formed in the clamping ring 14 (for example, as shown here in the second flow channel 12). In another or further embodiment, the protrusion can be formed in the membrane M (for example, as shown here in the first flow channel 11). FIG. 4BThe distance between the top of the first flow channel 11 and the membrane without protrusions can typically be between 2 mm and 2.5 mm. By adding protrusions or bumps, this can direct the flow closer to the membrane, e.g. less than one millimeter, or even less than 0.8 mm, e.g. similar or the same as the channel height (H1) before and / or after the membrane.

[0043] FIG. 5B A system 1000 (not to scale) and a method for using a microfluidic device 100 as described herein are shown.

[0044] Aspects of the present disclosure can be embodied in a system comprising a microfluidic device 100 as described herein. In one embodiment, the system comprises a pump 110, preferably a peristaltic pump. In a further or in a further embodiment, the system comprises at least a first reservoir 121 and a second reservoir 122. Channels or tubes can be used to interconnect the microfluidic device 100, the pump 110 and the reservoirs 121, 122 (e.g. with reference to FIG. 1A via the first set of connectors 11a, 11b or the second set of connectors 12a, 12b). Preferably, the first flow F1 through the first reservoir 121 is separated from the second flow F2 through the second reservoir 122 (except by the membrane M which is held inside the microfluidic device 100).

[0045] The microfluidic device 100 or the system 1000 as described herein can be used, for example, to analyze the permeability of a substance through a membrane M. In use, the membrane M is placed in the cavity opening 13i between the first flow channel 11 and the second flow channel 12. 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, a substance can be arranged in at least one of the fluid flows F1, F2, e.g. in different amounts. In some embodiments, the respective content of the substance in the first reservoir 121 and / or the second reservoir is measured and / or monitored to determine the exchange of the substance through the membrane M.

[0046] For example, a typical flow rate can be set between one milliliter and one hundred milliliters per hour, e.g. depending on the channel height. For example, a composition can be added to the first reservoir 121 and the composition in the second reservoir 122 is measured, e.g. by taking a sample from the reservoir. For example, the first reservoir 121 can be used to act as a (simulated) lumen, while the second reservoir 122 can be used to act as a blood vessel. For example, the composition can comprise a nutritional composition, a drug, etc. For example, the membrane M comprises a tissue sample, a scaffold (e.g. a 3D structure with cells) or other membranes (e.g. plastic or polyester). Thus, the microfluidic device 100 or the system 1000 can be used to test various membranes.

[0047] In interpreting the appended claims, it should be understood that the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim; the word "a" or "an" preceding the citation of a singular item does not exclude the presence of plural of the same item; any reference signs in the claims should not be construed as limiting the scope of the claims; the use of the term "about" in relation to a numerical value preferably means ± 10 % of the value; the mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the word "comprising" does not exclude other elements or steps than those listed in a given claim; any reference signs in the claims should not be construed as limiting the scope of the claims; the use of the term "about" in relation to a numerical value preferably means ± 10 % of the value; the mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the word "comprising" does not exclude other elements or steps than those listed in a given claim; any reference signs in the claims should not be construed as limiting the scope of the claims; the use of the term "about" in relation to a numerical value preferably means ± 10 % of the value; the mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the word "comprising" does not exclude other elements or steps than those listed in a given claim; any reference signs in the claims should not be construed as limiting the scope of the claims; the use of the term "about" in relation to a numerical value preferably means ± 10 % of the value; the mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage; the word "com

Claims

1. A microfluidic device (100) for analyzing the permeability of a substance through a membrane (M), wherein, The substances are arranged in respective fluid flows (F1, F2), the microfluidic device (100) comprising: a housing (10); a first flow passage (11) for passing a first fluid flow (Fl) through the housing (10) between a first input connector (11a) and a first output connector (lib); a second flow passage (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 inlet cavity (13) which extends from the outside into the housing (10) through the first flow channel (11) and into the second flow channel (12) for access to the interior of the housing (10) to place the membrane (M) above a cavity opening (13i) which forms a dedicated fluidic interconnection between the overlapping regions of the flow channels (11, 12); and a clamping ring (14) comprising a connection structure (14c) configured to engage a corresponding connection structure (13c) of the housing inside the access cavity (13) for holding a sample membrane (M) in place over the cavity opening (13i) with the membrane (M) in use exposed to respective fluid flows (F1, F2) through the flow channels (11, 12) on both sides of the membrane (M), wherein the cavity opening (13i) on one side of the membrane (M) and a ring opening (14i) through the clamping ring (14) on the other 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 clamping ring (14) is configured to form part of the first flow channel (11) for exposure to the first fluid flow (F1), wherein the clamping ring (14) is configured to form part of the first flow channel (11) and comprises a tapered or rounded transition (14r) between an inner diameter and an outer diameter of the clamping ring, the transition tapering towards a centre of the clamping ring where the membrane (M) is exposed to the first fluid flow (F1).

2. The microfluidic device (100) according to claim 1, wherein An integral part of the housing (10) extends with a cavity seat (13s) forming a platform around the cavity opening (13i) between the overlapping regions of the flow channels (11, 12) to hold the membrane (M) directly or indirectly between the cavity seat (13s) and the clamping ring (14), wherein the connection structure (13c) of the housing inside the entry cavity (13) surrounds the cavity seat (13s), wherein the connection structure (13c) of the housing protrudes from the cavity seat (13s).

3. The microfluidic device (100) according to claim 2, wherein The cavity seat (13s) comprises a sloped or rounded transition (11r) that tapers thin towards the cavity opening (13i) where the membrane (M) is exposed to the second fluid flow (F1).

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

5. The microfluidic device (100) according to claim 1, wherein The clamping ring (14) is configured to direct the first fluid flow (F1) through the clamping ring (14) to the ring opening (14i) via a connection channel (14a) and to direct the first fluid flow (F1) over the clamping ring (14) between a bottom (15b) of a lid (15) sealing the entry cavity (13) and the clamping ring (14) to the ring opening (14i).

6. The microfluidic device (100) according to claim 1, wherein The connection structure (13c) of the housing inside the entry cavity (13) comprises a set of clamping fingers with hooks configured to clamp around an edge of the clamping ring (14), wherein each of the fingers is configured to pivot radially outwards to enable insertion of the clamping ring and then back inwards with the hooks engaging a corresponding structure around the clamping ring (14), wherein the clamping fingers are positioned circumferentially around the cavity opening (13i).

7. The microfluidic device (100) according to claim 1, wherein A mesh (17) is provided between the membrane (M) and the cavity opening (13i).

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

9. The microfluidic device (100) according to claim 1, wherein The flow channels (11, 12) start with a first channel width (Wg) at a side of the input connector or the output connector and taper to a second channel width (Wh) towards the cavity opening (13i), wherein the second channel width (Wh) is greater than the first channel width (Wg) is at least twice the first channel width.

10. The microfluidic device (100) according to claim 1, wherein, The width (Wh) of the flow channel (11, 12) at least directly before the cavity opening (13i) is greater than the respective height of the flow channel (11, 12), being at least twice the respective height of the flow channel.

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

12. The microfluidic device (100) according to claim 1, wherein One or both of the first flow channel (11) and the second flow channel (12) are provided with a respective protrusion (AH1, AH2) towards the entry cavity (13) to reduce the respective channel height (H1, H2) at the location of the entry cavity (13) and divert the respective flow towards the membrane (M).

13. A system for analyzing the permeability of a substance through a membrane (M), the system comprising: a microfluidic device (100) according to claim 1; a pump (110); a first reservoir (121) and a second reservoir (122); and channels (11, 12, 14a) interconnecting the microfluidic device (100), the pump (110) and the reservoirs (121, 122); wherein a first flow (Fl) through the first reservoir (121) is separated from a second flow (F2) through the second reservoir (122) except by the membrane (M) held inside the microfluidic device (100).

14. A method for analyzing the permeability of a substance through a membrane, the method comprising: providing a microfluidic device (100) according to claim 1; placing the membrane (M) in the cavity opening (13i) between the first flow channel (11) and the second flow channel (12); passing a first flow (Fl) containing the substance through the first flow channel (11) via a first reservoir (121); passing a second flow (F2) through the second flow channel (12) via a second reservoir (122); and monitoring the respective content of the substance in at least the first reservoir (121) and the second reservoir (122) to determine the exchange of the substance through the membrane (M).

15. The method of claim 14, wherein, The first flow (Fl) through the first reservoir (121) is separated from the second flow (F2) through the second reservoir (122) except by the membrane (M) held inside the microfluidic device (100).

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