Flow regulator for controlling a liquid front in a microfluidic structure

Abstract

The present invention relates to flow regulation in microfluidic devices. In particular, the present invention relates to flow regulation in a chamber having a first raised surface and a second channel surface, using one or more passive valve structures in or on the second channel surface to improve uniformity and flow when filling a chamber or defined region in a microfluidic device.

Description

Technical Field

[0001] This invention relates to flow regulation in microfluidic devices. In particular, it relates to flow regulation using one or more passive valve structures to improve uniformity and flow when filling chambers or defined regions in a microfluidic device.

[0002] background Microfluidic devices have gained significant prominence as essential tools in the field of molecular diagnostics, particularly in the development of point-of-care (POC) devices. These POC devices, typically configured as boxes or tubes, are revolutionizing the healthcare industry by enabling rapid and reliable molecular analyses (such as polymerase chain reaction (PCR) and microarray-based assays) to be performed at or near the patient, minimizing turnaround time, and improving patient care. Microfluidic devices are particularly useful in a wide range of applications, finding widespread use in biomedical applications due to their small sample and reagent volumes, high throughput, and automation potential. However, despite their many advantages, microfluidic devices used in POC molecular diagnostics continue to face technological limitations due to challenges in controlling fluid flow and the formation and entrainment of bubbles within the fluid pathway.

[0003] In fluid or microfluidic devices, flow control challenges arise as fluid or fluid slugs move through different regions that may have different geometries and / or surface properties. For example, in WO2019 / 077323, there is a fluid pathway into a microarray chamber with a bubble deflection pathway that directs bubbles away from the observation area. However, moving fluid through such a chamber without air entrainment can be challenging. Typically, this is addressed by significantly reducing the flow rate through the region and by including additives such as low-foaming nonionic surfactants (e.g., Pluronic® in the sample liquid and elution) and / or hydrophilic array imprints on the chamber surface. This can result in slow usage times due to the time required to fill regions such as chambers, the additional costs of additives and surface additives, and potential downstream issues.

[0004] The presence of air bubbles within the fluid pathway can also cause problems such as fluid flow interruption and may hinder the performance of downstream analyses, such as imaging. This is particularly evident in devices that are partially heated (e.g., during PCR reactions) and then passed through for imaging (e.g., on microarrays), as the cyclic heating and cooling of the liquid in the fluid pathway leads to increased bubble formation, and bubble entrainment occurs at the liquid-gas interface of the microarray chamber.

[0005] Numerous methods and techniques have been proposed to avoid and suppress bubble generation during PCR processes in microfluidic systems. For example, a bubble trap with a microporous membrane has been described in US20150209783, and an upstream bubble trap for retaining bubbles has been described in EP17926551. Various methods for venting to the external atmosphere have been described; however, open systems with external venting are not always suitable, especially in medical devices testing potentially pathogenic substances.

[0006] Addressing flow control and / or bubble entrainment issues in microfluidic devices would be beneficial, especially for those designed for POC molecular diagnostics.

[0007] This patent application aims to eliminate or mitigate one or more problems related to flow control and / or bubble formation within microfluidic devices, particularly those used in POC molecular diagnostic kits and kits characterized by PCR components and microarrays.

[0008] Throughout this document, the term “microchannel” or “microchamber” refers to a channel or chamber having a hydraulic diameter of less than 1 mm in at least one dimension.

[0009] The term "chamber" as used herein refers to any chamber in a microfluidic device, such as a sample chamber and a detection chamber. The term "chamber" can also refer to a portion of a microfluidic channel in which specific activities occur or which possess specific characteristics.

[0010] The term "fluid connectivity" refers to a functional connection between two or more regions or chambers that allows fluid to pass between them.

[0011] The term "liquid front" refers to the leading edge or boundary of a liquid as it advances or spreads into different regions or media. Invention Overview According to the present invention, a microfluidic device with improved fluid flow regulation is provided, comprising a device body having at least one microfluidic passage, the passage including a microfluidic chamber that can be at least partially filled with fluid during use, the microfluidic chamber comprising: A first wall, a second wall, and one or more side walls, together defining a cavity, wherein the first wall includes: First base surface; A second base surface, adjacent to and recessed relative to the first base surface, defines at least one external channel, the external channel including at least one flow regulating structure, the flow regulating structure restricting the flow of liquid by reducing the cross-sectional area of ​​the chamber at the flow regulating structure.

[0013] An external channel refers to a channel with the second base surface as its base. In contrast, the first base surface forms a raised base, which can be considered as an internally raised base. In a preferred embodiment, the external channel completely surrounds the internally raised base.

[0014] Optionally, the flow regulation structure is in the form of a raised portion that extends from the second base surface of the first wall into the chamber.

[0015] Optionally, the flow regulation structure is in the form of a raised portion that extends from the second wall into the chamber.

[0016] Optionally, the top of the protrusion (the end or portion of the protrusion that extends to the farthest part of the cavity) is located below the first base surface (i.e., the top of the protrusion does not extend into the cavity as far as the first base surface) and above the second base surface (i.e., the top of the protrusion does extend from the second base surface and extends beyond the second base surface).

[0017] Preferably, the flow regulating structure is in the form of a raised portion that extends from the sidewall into the chamber, thereby reducing the cross-sectional area of ​​the chamber at the raised portion.

[0018] Optionally, at the location where the protrusion extends upward, the sidewall also extends inward, thereby further reducing the cross-sectional area of ​​the chamber at that location.

[0019] The protrusion is in the form of a wall or bump, having a front end extending into the cavity substantially perpendicular to the second base surface, a top portion (e.g., the top of the protrusion), and a rear end extending back to the second base surface.

[0020] Advantageously, the flow regulating structure controls the movement and distribution of fluid in the external channel. The flow regulating structure ensures uniform flow, minimizes bubble formation, and maintains the desired flow rate without requiring an external energy source. The flow regulating structure controls fluid flow by generating back pressure through contracting regions formed by protrusions or bulges that reduce the cross-sectional area of ​​the channel in which they reside. Preferably, the flow regulating structure is a portion of the channel that has a reduced cross-sectional area compared to portions of the channel directly upstream and downstream of it.

[0021] The phrase “recessed relative to” is used to describe the spatial relationship between the first and second surfaces. When the second base surface is “recessed” relative to the first base surface, it means that the first base surface is spatially positioned further inward into the cavity, or, for example, spatially lower than the second base surface (when the device is in use).

[0022] Advantageously, the second base surface provides grooves or one or more external channels surrounding the first base surface. The first base surface is essentially a base comprising the first base surface and one or more peripheral base walls extending to the second surface. By controlling or regulating the flow of liquid into and through the grooves, this allows for the management of fluid flow on the base, and thus the management of fluid flow on the first surface, resulting in more uniform filling of the chamber with reduced, minimal, or no bubble entrainment.

[0023] Advantageously, the liquid travels within an external channel defined by the second base surface, until it reaches the flow regulating structure. This restricts liquid flow and generates sufficient "back pressure" to force the liquid "leading edge" across the first base surface (which provides greater resistance) to a location where the leading edge catches up with the liquid held at the flow regulating structure. This acts as a trigger valve to release the liquid held at the flow regulating structure, allowing the liquid to then pass through or flow through the flow regulating structure into the next section of the external channel formed by the second base surface.

[0024] Preferably, the flow regulation structure is a passive valve.

[0025] Active valves require an external energy source, such as electrostatic, electromagnetic, pneumatic, hydraulic, or photothermal energy. These energy sources control fluid flow by deforming boundaries or by changing the state of boundaries (e.g., by melting wax or hydrogel). In contrast, passive valves do not require additional drive equipment, and their operation is determined by the controlled fluid. Passive valves do not require an external system to control the actuator to provide power (although they can exist in systems where fluid moves under power). Preferably, the flow regulating structure is a capillary valve.

[0026] A capillary valve is a passive valve that utilizes capillary forces within a fluid to regulate flow. These capillary forces arise from the surface tension of the liquid and the interaction between the liquid and the surface of the microchannels. These forces can be used to control the movement of the liquid without requiring an external power source. Capillary valves operate by generating varying capillary pressures within a region, which determine the fluid flow based on the valve's geometry and surface characteristics. This flow regulation method is highly efficient, particularly in microfluidic applications, as it ensures precise control of fluid movement through small-scale channels.

[0027] Preferably, the chamber has a fluid inlet and a fluid outlet.

[0028] Preferably, the first base surface is surrounded by the second base surface on at least one side.

[0029] Advantageously, the second base surface forms a groove or external channel surrounding the first base surface, wherein the groove or external channel includes one or more flow regulator structures.

[0030] Preferably, the first base surface is surrounded on both sides by grooves or external channels, the grooves or external channels including multiple flow regulating structures.

[0031] In this context, the reference to "both sides" refers to the second base surface acting as a diversion channel, such that there is actually a channel that splits into two outer channel portions as the fluid reaches the upstream edge of the first base surface. These two portions encircle the first base surface and then eventually rejoin downstream of the first base surface. Each of the two portions is considered a "side".

[0032] Optionally, the external channel includes multiple flow regulator structures.

[0033] In a particular embodiment, three flow regulators are present on each side of the first base surface.

[0034] In a particular embodiment, at least three flow regulators are present on each side of the first base surface.

[0035] In a particular embodiment, seven or eight flow regulators are present on each side of the first base surface.

[0036] Preferably, at least some of the multiple flow regulator structures are arranged in series, such that fluid flowing into and through the microfluidic chamber flows sequentially through each of the sequentially arranged flow regulator structures.

[0037] Optionally, the first wall and sidewalls of the microfluidic chamber are formed as grooves in the first substrate, and the second substrate is covered to surround the microchannel and form the lower wall.

[0038] Alternatively, the first substrate is substantially rigid.

[0039] Preferably, the first substrate is substantially planar.

[0040] Optionally, the second substrate is a membrane.

[0041] Preferably, the first substrate and the second substrate are combined together.

[0042] Preferably, the first substrate and the second substrate are laser welded together.

[0043] Optionally, the first substrate and the second substrate are bonded together with an adhesive.

[0044] In a particularly interesting embodiment, the chamber contains a microarray.

[0045] Preferably, the microarray is formed on the first surface region.

[0046] Optionally, the microfluidic chamber is at least partially formed in a plug that can be inserted into a first substrate or a second substrate, the plug being adapted to form at least a portion of the microfluidic chamber.

[0047] Optionally, the geometry of the first surface region and / or the second surface region is set on the surface of the plug that forms part of the microfluidic chamber.

[0048] Preferably, the first microfluidic chamber includes a curved outer wall.

[0049] It is preferable to have curved walls rather than angles or corners, as this ensures streamlined fluid flow and avoids flowing into corners (known as stagnation zones in fluid mechanics).

[0050] Alternatively, the microfluidic device is designed to allow fluid flow via capillary flow.

[0051] Alternatively, the microfluidic device is designed to make the fluid flow under positive pressure, such as agitating the fluid.

[0052] Alternatively, the microfluidic device is designed to allow fluid to flow under negative pressure, such as by pulling or sucking the fluid.

[0053] Alternatively, fluid is drawn into the microfluidic chamber by creating a pressure difference between the chamber and the upstream fluid passage. This is typically achieved by reducing the pressure in the chamber compared to the upstream region. This can be described as generating flow under negative pressure or suction.

[0054] A method of filling a microfluidic chamber in a microfluidic device as defined above includes allowing fluid to flow into the microfluidic chamber until the fluid reaches a flow conditioning structure for restricting liquid flow and generating sufficient "back pressure" to force a liquid "fronting edge" across a first base surface to a location where the liquid fronting edge flowing across the first base surface contacts and releases the liquid held at the flow conditioning structure, such that the liquid then flows through the flow conditioning structure into a next portion of an external channel formed by a second base surface.

[0055] Optionally, the microfluidic chamber comprises a microarray. In the case of a chamber with a grooved and raised base, controlled filling of the chamber in the microfluidic device occurs, the grooved and raised base being effectively formed by the chamber having a second base surface adjacent to and recessed relative to the first base surface. This second base surface defines at least one external channel. Flow regulating structures are employed to allow a liquid front to move in a controlled manner across the base surface in a way that reduces bubble formation. These structures control the advance of the liquid by generating sufficient back pressure, thereby ensuring uniform and uninterrupted flow. When the fluid reaches the flow regulating structure, the flow regulating structure contracts, building up sufficient pressure to force the liquid front to cross the first base surface. Upon contact, the liquid front releases the liquid held at the flow regulating structure, allowing it to enter the next portion of the external channel defined by the second base surface. This orderly progression ensures a smooth and efficient filling process, which is crucial for maintaining the integrity of the microarray and preventing the formation of air bubbles that could disrupt the microfluidic process.

[0056] Various other features and aspects of the invention are defined in the claims.

[0057] When referring to the “upper” or “lower” wall or surface in a chamber or channel, it can obviously be interpreted differently, since this refers to microfluidic flow where gravity is not actually dominant and therefore direction is not important.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. Brief description of the attached diagram Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which similar parts are provided with corresponding reference numerals, and wherein: Figure 1a This is a plan view of a portion of the microarray chamber according to the present invention; Figure 1b yes Figure 1a A partial unfolded diagram; Figure 2 This is a plan view of a portion of a microarray chamber according to another embodiment of the present invention; Figure 3 It shows Figure 2 Fluid flow in microarray chambers; and Figure 4 This is a table summarizing the experimental work on microarrays.

[0060] Detailed description In an exemplary embodiment of the invention, a microfluidic cartridge with continuously flowing microchannels is provided. The microchannels are formed inside the microfluidic cartridge at a desired length and shape to allow samples in liquid form (preferably biological samples) to pass through along a fluid flow path. The channels are formed in the lower surface of a first substrate, which in this embodiment is polycarbonate. The first substrate overlaps with a second substrate, which itself may have grooves formed in its upper surface that align with the channels of the first substrate. By joining the substrates together, a substantially closed channel (which may include an inlet and an outlet if desired) is provided. Again, since this refers to microfluidic flow, gravity does not actually play a dominant role, so the orientation of the upper and lower portions can be opposite. Any suitable joining means can be used; however, laser welding is particularly preferred. Where necessary, the first and second substrates can be aligned prior to joining. The length and cross-sectional shape of the channel can be any suitable shape to allow for desired transport and handling of the sample. For example, microchannel 2 may have a length of about 0.01 μm. 2 Up to 100mm 2 The cross-sectional area of ​​the microchannel. A region or portion of the microchannel, or a chamber within the microchannel, is dedicated to PCR, allowing the nucleic acid of interest to be amplified. This portion may have annealing, extension, and denaturation regions. Then, downstream of the PCR portion of the cassette, there is a portion of the channel forming a microarray chamber that provides capture of the amplified material. The microarray chamber 17 also allows observation or imaging of the captured material through an observation surface. For example, a camera can be aligned with the microarray chamber.

[0061] Figure 1a The image depicts a plan view of a portion of a microarray chamber 1 according to one aspect of the invention. The chamber 1 has a first basal surface 2 located at a relative center of the chamber 1, providing a base-like structure having a first basal surface 2a and a base wall 2b extending vertically from its periphery, and a second basal surface 3 recessed relative to and completely surrounding the first basal surface 2 to define a groove or external channel (in practice, the main channel divides into separate first and second external channels, which then reconverge downstream of the first basal surface). The first basal surface 2a is a microarray surface with multiple biological probes attached. The second basal surface 3, defining the walls of the groove, has multiple raised bumps 4 or walls (in... Figure 1aIn this embodiment, eight raised bumps 4 are present on each side of the first base surface 2 in the form of a microarray. The chamber also has an inlet 5 at the upstream end of the chamber 1 and an outlet 6 at the downstream end of the chamber 1. In this embodiment, the first base surface has a teardrop shape, wherein the narrower portion 9 of the teardrop is located at the downstream end of the chamber. This helps to prevent liquid from the filled first diversion channel from blocking the airflow out of the still unfilled second diversion channel in the case of asymmetrical filling.

[0062] Figure 1b A more detailed view of a portion of chamber 2 is shown. This shows in more detail the raised bumps 4 in the groove formed on the second base surface 3 (the cross-section of the groove and the raised bumps together form a delay valve). It can also be seen that the outer wall 8 of the chamber is shaped to have a protrusion 7a that projects inward into the channel formed by the second surface 3, further reducing the cross-sectional area of ​​the external channel formed by the second surface 3 at this protrusion 7a. Similarly, the outer periphery of the first base surface 2 also has a protrusion 7b shaped to project outward into the channel formed by the second base surface 3, further reducing the cross-sectional area of ​​the channel formed by the second surface 3 at this protrusion 7b. In this example, the first surface 2 is recessed 170 μm from the upper wall (not shown), which serves as a window. The total height of the chamber from the lowest point of the second base surface (i.e., the location without the bumps 4) to the opposite wall is 600 μm. The external channel or groove at the location without the bumps extends 1.1 mm between the outer wall 8 and the base wall 2b. The protrusion 4 is in the form of a wall, which is substantially perpendicular to the second base surface 2 and extends 200 μm from the second base surface 2 (walls of 100 μm and 150 μm have also been shown to work in this arrangement). The top surface of the protrusion 4 extends 550 μm between the outer wall 8 and the base wall 2b (due to the protrusions 7a and 7b), and has a width of 250 μm between its front (upstream) and rear (downstream) faces.

[0063] Figure 2Another embodiment of the microarray chamber 1' is shown, also in plan view through a cross-section of the chamber without an upper wall. Similarly, chamber 1 has a first base surface 2' and a second base surface 3', the first base surface 2' being located at the opposite center of chamber 1, providing a base-like structure, with a base wall 2b' extending vertically from the periphery of the first base surface 2', and the second base surface 3' being recessed relative to and completely surrounding the first base surface 2' to provide a groove or external channel (effectively divided into two external channel portions). Again, the first base surface 2' is a microarray surface with multiple biological probes attached. The second base surface 3' or groove has multiple raised bumps 4 or walls. In this embodiment, each side of the first base surface 2' has three raised bumps 4' in the form of a microarray. The raised bumps 4' together with the channel or groove portion directly upstream of the bumps 4' form a delay valve. If bubbles are present, reducing the number of bumps 4' (or delay valves) in the channel portion can provide more space for bubble treatment. Chamber 1' also has an inlet 5' at its upstream end and an outlet 6' at its downstream end. Similar dimensions can be used for the above-mentioned... Figure 1a and Figure 1b Those described. In this embodiment, the first base surface has an extension 9' at the downstream end of the chamber. This helps to prevent liquid from the first filled diversion channel from blocking the airflow from the second, still unfilled diversion channel in the case of asymmetrical filling.

[0064] The basic design principle of this invention is that a capillary valve is used to create a pressure barrier at the interface during the initial filling of the outer channel of the chamber (formed by a recessed second base surface), the chamber having a base-like structure including a first base surface. The capillary valve causes a pressure increase that pushes liquid toward the center of the chamber and above the base-like structure. The outer channel is made as wide as possible to accommodate larger volume bubbles within the channel while maintaining functionality during initial filling. A balance is struck between the number of valves to adequately control the initial interface while optimizing the volume to accommodate the bubbles. Manufacturing constraints also determine the number and size of the valves. The separation between the two channels prevents liquid flowing out of the filled first channel from blocking the airflow from the still unfilled second channel in the case of asymmetric filling.

[0065] While the embodiments described herein depict bumps 4 and 4' and protrusions 7a, 7a', 7b, and 7b', they collectively provide a region with a reduced cross-sectional area. Those skilled in the art will understand that either bumps or protrusions can be used. However, it is preferred to have at least protrusions 7a, 7a', and 7b.

[0066] Figure 3 It shows how the liquid flows. Figure 2The microarray chamber 1' (although it is understood that the same flow characteristics will also occur in other chambers designed according to the invention, for example) Figure 1a The chamber 1 shown is illustrated. When a liquid sample enters through inlet 5', it initially flows onto the upstream portion of the second base surface 3'. This initial upstream portion widens in an extended conical shape and has relatively low resistance due to its wider surface area compared to inlet 5'. When the liquid leading edge encounters the front of the base wall 2b' (in this embodiment, the base wall 2b' extends substantially vertically upward relative to the second surface 3'), the liquid splits into two streams, such as... Figure 3 As shown in (A), the liquid flows along a groove-like channel formed by the second surface 3', the outer side wall 8, and the base wall 2b. Each stream advances until it reaches the front wall of the raised bump 4, where it temporarily stops flowing while restricting the liquid flow. This creates sufficient "back pressure" to force the liquid front to flow over the first base surface 2. The liquid front flows over the first base surface until it contacts and releases the liquid held at the bump 4a' (as shown in (A)). Figure 3 As shown in (B), the liquid then flows through the flow regulating structure into the next part of the external channel formed by the second base surface. The liquid then follows the same pattern until it reaches the front wall of the next raised bump 4b', which again temporarily stops the flow because the front arm restricts the liquid flow. This again generates enough "back pressure" to force the liquid front to flow further across the first base surface 2'. The liquid front flows across the first base surface until it contacts and releases the liquid held at the bump 4b' (as shown in (B)). Figure 3 (as shown in (C)).

[0067] Experimental work To test the benefits of using the filling chamber of this invention, tests were conducted with and without a delay valve. The version without the delay valve showed no area of ​​reduced cross-sectional area in the flow channel (the flow channel typically has a height and width of 600 μm). The version with the valve is as described above. Figure 1a and Figure 1b The test results are shown below. Figure 4 The results show that there are clear benefits. Explanatory notes regarding the results are as follows: Fill with water: The array chambers can be repeatedly filled with both tap water and ultrapure water (MQ water) – this is the worst-case scenario in terms of surface tension. Yes: the chambers can be repeatedly filled with liquid samples (solvents).

[0068] No: Chamber It cannot be filled properly. Fluids exhibit unpredictable behavior.

[0069] Unreliable: The chamber is only sometimes filled; the data is not repeatable.

[0070] Fill time: The time required to completely fill the chamber.

[0071] Permissible air / water bubbles: When bubbles are contained within the water slug, the chamber is filled, and the bubbles are not pushed into the recessed array region.

[0072] Fill with elution buffer + 0.1% Pluronic: The sample contains Pluronic to facilitate filling, but the filling is not repeatable every time.

[0073] Wash-out filling: DNA is eluted from the filter using buffer, and then PCR is performed on the sample before it enters the chamber, which can be repeatedly filled with elution buffer.

[0074] Fill with elution buffer containing a 70 µL air slug: The elution buffer is combined with a 70 μL continuous air slug and bubble-filled elution buffer. The chamber can be repeatedly filled with elution buffer and there are no air bubbles on the concave ring. The air bubbles and air slug flow through the side groove.

[0075] Wash with PBST: PBS buffer containing the nonionic surfactant Tween 20 is used to wash the array after hybridization; the chambers can be repeatedly filled with PBST.

[0076] Maximum permissible PBST bubble volume: The permissible volume of air bubbles in the PBST segment plug.

[0077] All features disclosed in this specification (including any appended claims, abstracts, and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, unless at least some of such combinations of features and / or steps are mutually exclusive. Unless otherwise expressly stated, each feature disclosed in this specification (including any appended claims, abstracts, and drawings) may be replaced by an alternative feature having the same, equivalent, or similar purpose. Therefore, unless otherwise expressly stated, each disclosed feature is merely an example of a series of equivalent or similar features. The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification (including any appended claims, abstracts, and drawings), or to any novel step or any novel combination of steps of any method or process so disclosed.

[0078] In particular, the flow regulating structure can be in the form of a bump or protrusion as described in the preferred embodiment, but it can also be molded into part of a second substrate and then positioned in a groove when bonded to the substrate to create a similar valve structure.

[0079] Regarding the use of virtually any plural and / or singular terms in this document, those skilled in the art may convert plural to singular and / or singular to plural as appropriate, depending on the circumstances and / or application. For clarity, various singular / plural substitutions may be explicitly described herein.

[0080] Those skilled in the art will understand that, in general, the terminology used herein, and especially in the appended claims, is typically intended as “open” terms (e.g., the terms “including” or “comprising” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “at least having,” the term “includes” should be interpreted as “including but not limited to,” and so on). Those skilled in the art will further understand that if a particular number of claims is intended to be introduced, this intention will be explicitly referenced in the claims, and without such reference, such intention does not exist. For example, to aid understanding, the appended claims may contain the introductory phrases “at least one” and “one or more” to introduce the statement of the claims. However, the use of such phrases should not be construed as implying that a claim reference introduced by the indefinite article “a(a)” or “an(an)” limits any particular claim containing such an introduced claim reference to an embodiment containing only one such reference, even when the same claim includes the introductory phrase “one or more” or “at least one” and an indefinite article such as “a(a)” or “an(an)” (e.g., “a(a)” and / or “an(an)” should be interpreted as “at least one” or “one or more”); the same applies to the use of definite articles for introducing claim references. Furthermore, even when a specific number of introduced claim references are explicitly cited, those skilled in the art will recognize that such references should be interpreted as meaning at least the number cited (e.g., a simple reference in “two references” without other modifiers means at least two references, or two or more references).

[0081] It will be understood that various embodiments of this disclosure have been described herein for illustrative purposes, and various modifications may be made without departing from the scope of this disclosure. Therefore, the various embodiments disclosed herein are not intended to be limiting, and their true scope is indicated by the appended claims.

Claims

1. A microfluidic device with improved fluid flow regulation, comprising a device body having at least one microfluidic passage, the passage including a microfluidic chamber capable of being at least partially filled with fluid during use, the microfluidic chamber comprising: A first wall, a second wall, and one or more side walls, together defining a cavity, wherein the first wall includes: - First base surface; - A second base surface, adjacent to and recessed relative to the first base surface, the second base surface defining at least one external channel, the external channel including at least one flow regulating structure, and the flow regulating structure restricting the flow of liquid by reducing the cross-sectional area of ​​the chamber at the flow regulating structure.

2. The microfluidic device according to claim 1, wherein, The flow regulating structure is in the form of a raised portion that extends from the second surface of the first wall or from the second wall.

3. The microfluidic device according to claim 2, wherein, The protrusion extends to the farthest end of the cavity but does not extend as far as the first base surface, and extends from and beyond the second base surface.

4. The microfluidic device according to claim 2 or 3, wherein, The flow regulation structure is in the form of a raised portion that extends from the sidewall into the chamber, thereby reducing the cross-sectional area of ​​the chamber at the raised portion.

5. The microfluidic device according to any one of the preceding claims, wherein, The flow regulation structure is a passive valve.

6. The microfluidic device according to any one of the preceding claims, wherein, The flow regulation structure is a capillary valve.

7. The microfluidic device according to any one of the preceding claims, wherein, The chamber has a fluid inlet and a fluid outlet.

8. The microfluidic device according to any one of the preceding claims, wherein, The first base surface is surrounded on at least one side by the second base surface, the second base surface including at least one flow regulator structure.

9. The microfluidic device according to any one of the preceding claims, wherein, The first base surface is surrounded on both sides by the second base surface, which includes a plurality of flow regulator structures.

10. The microfluidic device according to any one of the preceding claims, wherein, The second base surface includes multiple flow regulator structures.

11. The microfluidic device according to claim 10, wherein, At least some of the plurality of flow regulator structures are arranged in series such that fluid flowing into and through the microfluidic chamber flows sequentially through each of the sequentially arranged flow regulator structures.

12. The microfluidic device according to any one of the preceding claims, wherein, In the microfluidic chamber, the first wall and sidewalls are formed as grooves in a first substrate, and a second substrate is covered to surround the microchannel and form the second wall.

13. The microfluidic device according to claim 12, wherein, The first substrate is substantially rigid.

14. The microfluidic device according to any one of claims 12 or 13, wherein, The first substrate is substantially planar.

15. The microfluidic device according to any one of claims 12 to 14, wherein, The second substrate is a film.

16. The microfluidic device according to any one of claims 12 to 15, wherein, The first substrate and the second substrate are bonded together.

17. The microfluidic device according to claims 12 to 16, wherein, The first substrate and the second substrate are laser-welded together.

18. The microfluidic device according to any one of the preceding claims, wherein, The chamber includes a microarray.

19. The microfluidic device according to claim 18, wherein, The microarray is formed on the first surface region.

20. The microfluidic device according to any one of the preceding claims, wherein, The microfluidic chamber is at least partially formed in a plug that can be inserted into the first substrate or the second substrate, the plug being adapted to form at least a portion of the microfluidic chamber.

21. The microfluidic device according to any one of the preceding claims, wherein, The microfluidic chamber includes a curved outer wall.

22. The microfluidic device according to any one of the preceding claims, wherein, The microfluidic device is designed to allow fluid flow via capillary flow.

23. The microfluidic device according to any one of the preceding claims, wherein, The microfluidic device is designed to make fluid flow under positive pressure, such as to propel the fluid.

24. The microfluidic device according to any one of the preceding claims, wherein, The microfluidic device is designed to make fluid flow under negative pressure, for example, to propel the fluid.

25. A method of filling a microfluidic chamber in a microfluidic device according to any one of claims 1 to 24, comprising allowing fluid to flow into the microfluidic chamber until the fluid reaches the flow conditioning structure, the flow conditioning structure being configured to restrict liquid flow and generate sufficient "back pressure" to force a liquid "fronting edge" across a first base surface to a location where the liquid fronting edge flowing across the first base surface contacts and releases the liquid held at the flow conditioning structure, such that the liquid then flows through the flow conditioning structure into a next portion of the external channel formed by a second base surface.

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