Microfluidic device

Abstract

A microfluidic device for delivering fluid to one or more assays, the device comprising a first region 4 for receiving a fluid sample, a channel 5, and a second region 6. The channel connects the first and second regions, transferring sample from the first region to the second region via capillary action. The microfluidic device further comprises at least one well 9, 19, 29 for receiving and retaining a portion of the sample wherein the or each well comprises an inlet 10 fluidly connected to the channel, and an outlet 12 for delivering the sample portion to an assay of the one or more assays 2a, 2b, 2c. Ideally, the outlets are shaped to retain the sample unless the surface tension of the sample within the well is changed. A system 18 comprising the device and assays, which maybe ELISAs or lateral flow, wherein the device is movable relative to the assays. In use, a sample is introduced into the device at the first region and travels along the device to the second region whilst filling the or each well. Ideally, the sample is retained in a well until the outlet of the well contacts an absorbent pad of an assay and a portion is wicked from the well.

Description

Technical Field The present invention relates to a microfluidic device for delivering fluid to one or more assays, and a method of using a microfluidic device. Background Assays, such as lateral flow assays, well based assays, or ELISAs, are used to conduct tests for purposes such as detecting disease, assessing the health of a patient, or for nutritional reasons. In conducting the test, a fluid sample (e.g. blood) is provided and applied to a lateral flow assay. However, there are various problems with using assays. In some instances, the volume of the fluid sample may be too great which results in the assay being flooded and the test result being void. In other instances, insufficient volume can also be problematic in obtaining a reliable result, and hence test results being void. In other instances, it is necessary to ensure that a more exact volume of fluid sample is applied to the assay. Variation in the volume in tests of the fluid sample can lead to inaccurate results. If a more exact volume of the fluid sample is required then the volume of the fluid sample may be measured using an additional apparatus such as a pipette or capillary tube but the additional apparatus results in additional steps which increases the complexity of an operator performing the test, and risk of errors from the operator. Sometimes it is desirable to conduct multiple tests on multiple assays using a sample from the same patient. In this case, a portion of the fluid sample must be applied to each assay which conducts a different test on the fluid sample. It can be cumbersome and time consuming to co-ordinate the application of the fluid sample to multiple assays. There is a risk of operator error if the operator is handling the fluid sample and having to apply the fluid sample to multiple assays e.g. the operator may drop the fluid sample between applying it to the different assays. It is therefore the object of the present invention to provide a microfluidic device that overcomes one or more of the problems mentioned above. Summary The present invention provides a microfluidic device for delivering fluid to one or more assays, wherein the microfluidic device comprises: a first region for receiving a fluid sample; a channel; a second region, wherein the channel connects the first region to the second region, and wherein the channel is for transferring the fluid sample from the first region to the second region via capillary action; and at least one well for receiving and retaining a portion of the fluid sample, the or each well comprising an inlet which is fluidly connected to the channel, and an outlet for delivering the portion of the fluid sample to an assay of the one or more assays. The or each well may be configured to retain the portion of the fluid sample by capillary forces. The or each well may be configured to retain the portion of the fluid sample by capillary forces until the portion of the fluid sample in the or each well is connected to an associated assay for drawing the fluid sample from the or each well. The second region may comprise an absorbent pad for drawing the fluid sample from the channel when the fluid sample contacts the absorbent pad. The width of the inlet of the or each well may be smaller than the width of the channel. The channel may comprise at least one microfluidic cavity which is fluidly connected to the inlet of an associated well of the at least one wells. The width of the or each microfluidic cavity may be greater than the width of the inlet of its associated well. The at least one microfluidic cavity may comprise a first microfluidic cavity. The channel may have a first channel width between the first region and the first microfluidic cavity. The width of the first microfluidic cavity may be greater than the first channel width. The ratio of the first channel width to the width of the first microfluidic cavity may be between 0.6 to 1 and 0.8 to 1, and optionally around 0.7 to 1. The at least one microfluidic cavity may comprise a second microfluidic cavity, and wherein the channel has a second channel width between the first microfluidic cavity and the second microfluidic cavity, wherein the width of the second microfluidic cavity is greater than the second channel width. The first channel width may be the same or substantially the same as the second channel width. The ratio of the second channel width to the width of the second microfluidic cavity may be between 0.6 to 1 and 0.8 to 1, and optionally around 0.7 to 1. The or each microfluidic cavity has a length along the direction of the channel from the first region to the second region. The length of the or each microfluidic cavity may be greater than the length of the inlet of its associated well along the direction of the channel from the first region to the second region. The length of the or each microfluidic cavity may be around 0.5mm to 10mm. The length of the or each microfluidic cavity may be around 4.6mm. The height of the or each well between the inlet and the outlet may be around 0.5mm to 50mm. The height of the or each well between the inlet and the outlet may be around 5mm. The length of the or each well along the direction of the channel from the first region to the second region may be around 0.5mm to 10mm. The length of the or each well along the direction of the channel from the first region to the second region may be around 4mm. The or each well may comprise sidewalls which surround the outlet of the or each well. The sidewalls may have a thickness of 0.5 mm or less, and optionally wherein the sidewalls have a thickness of around 0.1 mm. The sidewalls may comprise at least one recess for assisting the delivery of the portion of the fluid sample to the assay. Additionally or alternatively, the sidewalls may comprise protrusions and / or abrasions for assisting the delivery of the portion of the fluid sample to the assay. The width of the outlet of the or each of the wells may be around 0.1mm to 2mm. The width of the outlet of the or each of the wells may be around 0.45mm. The volume of the or each well may be around 5 to 40 microlitres, optionally wherein the volume of the or each well is around 6 to 10 microliters and optionally wherein the volume of the or each well is around 6 microlitres. The or each well may have a longitudinal direction which is aligned with the direction of the channel from the first region to the second region. The first region may comprise a slope which is declined towards the channel for assisting the transfer of the fluid sample from the first region to the channel. The or each well may comprise a plurality of wells. The plurality of wells may comprise a first well and a second well, and optionally a third well. The channel may comprise a hydrophilic agent, and optionally wherein the hydrophilic agent comprises PBS-Tween. The device may further comprise an covering, such as an adhesive film or lid, which is located over the channel on the opposite side of the channel to the or each of the at least one wells. A system comprising the microfluidic device as defined herein claims, and one or more assays, and optionally wherein the or each well is movable relative to the assays. The device may further comprise a platform on which the channel and the or each well are mounted, and a base for mounting the one or more assays, wherein the platform is movable relative to the base between a filling position for allowing the fluid sample to be received in the first region and a test position for allowing the portion of the fluid sample to be delivered from the or each well to an associated assay of the one or more assays. The first region and / or the second region may be mounted on the platform. The microfluidic device may further comprise the one or more assays, wherein the one or more assays are mounted on the base. The platform may be connected via a hinge to the base, and optionally wherein the hinge is a living hinge. The hinge may be located closer to the second region than the first region. The longitudinal axis of the channel may be declined from the first region towards the second region when the platform is in the filling position. The longitudinal axis of the channel may be rotated through 5 to 15 degrees, and optionally rotated through around 10 degrees, when the platform is moved from the filling position to the test position. The base may comprise a planar surface for mounting the one or more assays, and wherein the channel is parallel or substantially parallel to the planar surface when the platform is in the test position. The device may further comprise a holding mechanism for holding the platform in the filling position. The device may further comprise a locking mechanism for locking the platform in the testing position. The or each assay may comprise an absorbent pad. The present invention further provides a method of using a microfluidic device for delivering fluid to one or more assays, wherein the microfluidic device comprises: a first region for receiving a fluid sample; a channel connecting the first region to the second region for transferring the fluid sample from the first region to the second region via capillary action; and at least one well for receiving and retaining a portion of the fluid sample, the or each well comprising an inlet which is fluidly connected to the channel, and an outlet for delivering the portion of the fluid sample to an assay of the one or more assays, the method comprising providing the fluid sample into the first region. The method may further comprise waiting until the or each well has received a portion of the fluid sample before connecting the portion of the fluid sample in the or each well to an associated assay for drawing the fluid sample from the or each well. The second region may comprises a absorbent pad for drawing the fluid sample from the channel when the fluid sample contact the absorbent pad, and wherein the method further comprises waiting until the absorbent pad has drawn the fluid sample from the channel before connecting the portion of the fluid sample in the or each well to its associated assay for drawing the fluid sample from the or each well. The method may comprise a method of using a microfluidic device having any of the features as claimed or described herein. Brief Description of the Drawings Embodiments of the invention will now be described, by way of example only, in relation to accompanying drawings, in which: Figure 1A shows a perspective view of a microfluidic device according to an embodiment of the invention; Figure IB shows example assays mounted to a base; Figure IC shows a perspective view of a microfluidic device according to another embodiment of the invention having one well; Figure 2 shows a top view of the microfluidic device of Figure 1A; Figure 3 shows a perspective underneath view of the wells of the microfluidic device of Figure 1A; Figure 4A shows a cross sectional view of the wells of the microfluidic device of Figure 1A cut through the axis A-A; Figure 4B shows a cross sectional view of the wells of the microfluidic device of Figure 1A cut through the axis B-B; Figures 5A-5D illustrate the channel and one of the wells from the device of Fig. 1A from above, during use of the microfluidic device; Figure 6A shows a perspective view of an alternative embodiment of a microfluidic device in a filling position; Figure 6B shows the device of figure 6A in a testing position; Figure 7 shows a top view of the microfluidic device of Fig. 6A ; Figure 8A shows a cross-section through the axis of the channel of the microfluidic device in Fig. 6A; Figure 8B shows a cross-section through the axis of the channel of the microfluidic device in Fig. 6B; and Figures 9 shows the method for using the microfluidic device according to an embodiment. Detailed Description In the description and drawings, like reference numerals refer to like elements throughout. Referring to Figure 1A, a microfluidic device 1 according to an embodiment of the invention is shown for delivering fluid to one or more assays, such as the assays 2A, 2B, 2C which are shown in Fig. IB, which are mounted to a rigid base 30. The assays 2A, 2B, 2C each comprise an absorbent pad 3. The microfluidic device 1 comprises a first region 4 for receiving the fluid sample such as blood, a channel 5 and a second region 6. The channel 5 transfers the fluid sample from the first region 4 to the second region 6 via capillary action. The first region 4 comprises a slope 17 which is declined towards the channel 5 for assisting the transfer of the fluid sample from the first region 4 to the channel 5. However, in an alternative embodiment, the first region 4 does not comprise a slope and the first region 4 receives the fluid sample on a base surface which is co-planar with a base 51 of the channel. In the example shown in Fig. 1A, the first region 4 has a base and walls extending from the base. The width of the first region 4 may taper towards the channel 5 for funnelling the fluid sample towards the channel. The first region 4 is open on its upper side for a user to access the first region 4. The second region 5 is open its upper side for a user to visibly see when the fluid sample is located in the second region 5. In the Figures, the channel 5 is advantageously straight for improved capillary action and defines a longitudinal axis A-A and perpendicular axis B-B which is transverse to the channel 5. It is to be appreciated that other shaped channels 5, such as curved channels, channels comprising an angle (which may be a 90-degree angle), and branched channels are intended within the scope of the present invention. In use, the fluid sample flows from the first region 4 to the second region 6. Therefore, it is possible to talk about a flow direction of the fluid along the channel from the first region 4 to the second region 6. Features can be described as upstream or downstream relative to one another in relation to the flow direction, for example the second region 6 is downstream of the first region 4. The second region 6 comprises an absorbent pad 16 for drawing the fluid sample from the channel 5 when the fluid sample contacts the absorbent pad 16. The volume of the fluid which is delivered via the outlet 12 of each of the wells 9, 19, 29 is equal or substantially equal to the volume of the fluid which is retained in each of the wells. The absorbent pad 16 may be formed from cellulose. In an alternative embodiment (not shown), the absorbent pad 16 could be omitted and the end of the channel 5 at the second region 6 could be open for transferring the fluid sample from the first region 4 to the second region 6 via capillary action. The microfluidic device 1 has a plurality of wells including a first well 9, a second well 19 and a third well 29. Each of the first, second and third wells 9, 19, 29 is for receiving and retaining a portion of the fluid sample. Each of the first, second third wells 9, 19, 29 comprises an inlet 10 which is fluidly connected to the channel 5 and an outlet 12 for delivering the portion of the fluid sample from the well to an assay 2A, 2B, 2C. The wells 9, 19, 29 extend from a base 51 of the channel 5. Each of the wells 9, 19, 29 has a longitudinal direction which is aligned with the direction of the channel from the first region 4 to the second region 6. The direction of the channel 5 is along the longitudinal axis A-A. In the example shown in the figures, the microfluidic device 1 comprises three wells 9, 19, 29. Each of the wells 9, 19, 29 is able to retain a portion of the fluid sample and deliver the portion of the fluid sample to an assay 2A, 2B, 2C. Figure IC shows a perspective view of an alternative embodiment of a microfluidic device with only one well 9. The microfluidic device of Fig. IC is the same as the microfluidic device of Fig. 1A except that the device only has one well 9. Figure IC retains the same reference numerals as those used in relation to Figure 1A. It is to be appreciated that in alternative embodiments, the microfluidic device 1 may alternatively comprise two wells or four or more wells. If a plurality of wells are provided then each of the wells may have the same features. In other words, each of the plurality of wells may have identical features. This is advantageous as multiple wells can be filled consistently with the same volume of fluid sample to ensure the different assays receive the same volume of the fluid sample. In an alternative embodiment (not shown) the plurality of wells may not be identical. For example, one well of the plurality of wells could have a larger volume than the other wells of the plurality of wells or each of the wells may have different volumes. Each well may deliver its portion of fluid sample to a separate assay 2A, 2B, 2C. If a single well is provided, then the single well may deliver its fluid sample to a single assay. Referring to Figure 2, there is shown a view of the channel 5 of Fig. 1A from above comprising the first, second and third wells 9, 19, 29. As noted, each of the wells 9, 19, 29 comprises an inlet 10 which is fluidly connected to the channel 5. Each of the inlets 10 has a width W2. The width W2 extends in a direction which is transverse to the channel 5. The width W2 of the inlet of each of the wells 9 19, 29 may be the same or substantially similar. The channel 5 comprises a microfluidic cavity 11, 111, 211 associated with each well 9, 19, 29. Specifically, a first microfluidic cavity 11 is fluidly connected to the inlet 10 of the first well 9, a second microfluidic cavity 111 is fluidly connected to the inlet 10 of the second well 19, and a third microfluidic cavity 211 is fluidly connected to the inlet 10 of the third well 219. The width of the channel 5 increases to form the or each of the microfluidic cavities 11, 111, 211. Each of the microfluidic cavities 11, 111, 211 has a width W3. The microfluidic cavities 11, 111, 211 may have a substantially similar or the same width. The width of the channel W1 is the same or substantially similar both upstream and downstream of the or each of the microfluidic cavities 11, 111, 211. Specifically, the channel 5 has a first channel width W1 between the first region 4 and the first microfluidic cavity 11. The width W3 of the first microfluidic cavity 11 is greater than the first channel width Wl for improving the filling of the well. The ratio of the first channel width W1 to the width of the first microfluidic cavity W3 may be between 0.6 to 1 and 0.8 to 1, and optionally 0.7 to 1. The width W2 of the inlet of the first well 9 is smaller than the width W3 of the first microfluidic cavity. In alternative embodiments, the width W2 of the inlet of the first well 9 may be equal to the width W3 of the first microfluidic cavity. The width W2 of the inlet of the first well is smaller than the first channel width Wl. In another embodiment, the width W2 of the inlet of the first well 9 may be equal to the first channel width Wl. The channel has a second channel width Wl between the first microfluidic cavity 11 and the second microfluidic cavity 111. The width W3 of the second microfluidic cavity 211 is greater than the second channel width Wl for improving the filling of the wells. The ratio of the second channel width Wl to the width of the second microfluidic cavity W3 may be between 0.6 to 1 and 0.8 to 1, and optionally 0.7 to 1. The width W2 of the inlet of the second well 19 is smaller than the width W3 of the second microfluidic cavity. In alternative embodiments, the width W2 of the inlet of the second well 19 may be equal to the width W3 of the second microfluidic cavity. The width W2 of the inlet of the second well 19 is smaller than the second channel width Wl. In alternative embodiments, the width W2 of the inlet of the second well 19 may be equal to the second channel width Wl. The channel has a third channel width Wl between the second microfluidic cavity 111 and the third microfluidic cavity 211. The width W3 of the third microfluidic cavity 211 is greater than the third channel width Wl for improving the filling of the well. The ratio of the third channel width Wl to the width of the third microfluidic cavity W3 may be between 0.6 to 1 and 0.8 to 1, and optionally 0.7 to 1. The width W2 of the inlet of the third well 29 is smaller than the width W3 of the third microfluidic cavity. In alternative embodiments, the width W2 of the inlet of the third well 29 may be equal to the width W3 of the third microfluidic cavity. The width W2 of the inlet of the third well 29 is smaller than the third channel width Wl. In alternative embodiments, the width W2 of the inlet of the third well 29 may be equal to the third channel width Wl. The channel has a fourth channel width Wl between the third microfluidic cavity 211 and the second region 6. In an alternative embodiment (not shown) the width of the microfluidic cavities 11, 111, 211 may vary between the microfluidic cavities. In an alternative embodiment (not shown) the width of the channel Wl may vary upstream and downstream of the microfluidic cavities. In an alternative embodiment (not shown) the width of the first, second and third microfluidic cavities W3 is the same as the first, second and third channel widths Wl. The portion of the fluid sample is retained in each of the wells 9, 19, 29 by capillary forces. The capillary forces may be influenced by, for example, the selection of the ratio of the channel widths Wl to the microfluidic cavity widths W3, the selection of materials used for the cavities 111, 211, 311, wells 9, 19, 29 and channel 5, any surface treatment of the materials used and / or the properties of the fluid sample. Each of the microfluidic cavities 11, 111, 211 has a longitudinal direction which is aligned with the direction of the channel 5 from the first region to the second region 6. It is to be appreciated that the microfluidic cavities 11, 111, 211 are only optional, and channels 5 that do not comprise the microfluidic cavities 11, 111, 211 are intended within the scope of the present invention. Referring to Figure 3, a perspective underneath view of the wells 9, 19, 29 is shown. Each of the wells 9, 19, 29 comprises an outlet 12 for delivering a portion of the fluid sample from the well 9, 19, 29 to an assay 2. Each of the wells 9, 19, 29 is configured to retain the portion of the fluid sample therein by capillary forces such as surface tension. In embodiments that comprise a absorbent pad 16, the portion of the fluid sample is retained in each of the wells 9, 19, 29 after the fluid sample present in the channel 5 is drawn out of the channel 5 by the absorbent pad 16. This enables each of the wells to deliver a precise volume of fluid, which is equal to the volume of fluid which is retained in each well, to an assay. The outlet 12 of each of the wells 9, 19 29, is shaped and dimensioned such that the portion of the fluid sample which is received in the well 9, 19, 29, does not exit the well unless the capillary force acting to retain the fluid sample in the well 9, 19, 29 are overcome. This may be by changing the surface tension of the portion of the fluid sample within the well or by introducing alternative forces on the fluid sample, such as an attractive drawing force to draw the fluid sample out of the wells. It will be appreciated that the shape and dimensions of each of the wells can vary in order to retain the portion of the fluid sample therein. It is further appreciated that the retention of the portion of the fluid sample in the wells will depend on factors such as the fluid to be tested, and the material from which the wells are made of, the dimensions of the wells and any coatings on the inside of the wells, for example. In the embodiment shown in Figure 3, each of the wells 9, 19, 29 comprises sidewalls 13 which surround the outlet 12 of each of the wells. The sidewalls 13, have a thickness of 0.5 mm or less, optionally 0.1 mm. The thickness of the sidewalls 13 may advantageously assist in delivering the portion of the fluid sample from the outlet 12 onto an absorbent pad 3 of an assay 2. The thickness of the sidewalls may be greater than 0.5mm in an alternative embodiment. Fibres from the absorbent pad 3 enter into the outlet 12 when a user brings the assay 2 in proximity to the outlet 2 for assisting in the absorbent pad 3 of the assay contacting and wicking the portion of the fluid sample out of the well. The sidewalls 13 of each well 9, 19, 29 comprise recesses 15 for assisting the delivery of the portion of the fluid sample to the assay. The recesses 15 allow fibres from an absorbent pad 3 to enter into the outlet 12 and hence assist in the absorbent pad wicking the portion of the fluid sample out of the well. It is to be appreciated that the sidewalls 13 may alternatively comprise a single recess, or no recesses. Alternatively or additionally the sidewalls 13 of each well 9, 19, 29 comprise protrusions and / or abrasions for assisting the delivery of the portion of the fluid sample to the assay. The microfluidic device 1 may further comprise stoppers 21 which may abut the rigid base 30 when the wells 9, 19, 29 are brought into contact with the assays 2A, 2B, 2C, respectively (see Fig IB). The microfluidic device 1 may therefore be restricted in its vertical movement. It is to be appreciated that embodiments of the invention that do not comprise the stoppers 21 are intended within the scope of the present invention. Figure 4A shows a cross sectional view of part of the microfluidic device of Fig. Figure 1A, taken along the axis A-A, which is marked in Fig. 2. Further shown are the assays 2A, 2B, 2C from Fig. IB, mounted to the rigid base 30 whereby the wells 9, 19, 29 are positioned such that they can be moved by a user to bring the portion of the fluid sample in each of the wells 9, 19, 29 into contact with an associated assay. The portion of the fluid sample in the first well 9 can therefore be connected to the first assay 2A, the portion of the fluid sample in the second well 19 can therefore be connected to the second assay 2B, and the portion of the fluid sample in the third well 29 can therefore be connected to the third assay 2C. The height of the channel 5 is defined by height Hl, and may be between 0.5 to 1.5 mm, and optionally 1mm. The height H2 of each of the wells 9, 19, 29 between the inlet 10 and the outlet 12 may be between 0.5mm and 50mm, and may be 5 mm. The length L2 of the inlet 10 of each of the wells 9, 19, 29 is defined by length L2 along the direction of the channel from the first region 4 to the second region 6. The length L2 may be between 0.5mm mm and 10 mm, optionally between 3 and 5 mm, and optionally be around 4 mm. Figure 4B shows an alternative cross-sectional view of one of the wells which is taken along an axis which is transverse to the channel 5. In some embodiments, the width W5 of the outlet 12 of each of the wells 9, 19, 29 may be around 0.1mm to 2mm. The width W5 of the outlet 12 of each of the wells 9, 19, 29 may be 0.45 mm. The width of the outlet W5 may be the same as the width of the inlet W2 for each of the wells. The volume of each of the wells 9, 19, 29 may be between 5 and 40 microlitres, optionally between 6 to 10 microlitres, and optionally around 6 microlitres, for example. The volume of each of the wells 9, 19, 29 is the same. However, in an alternative embodiment, the volume of each of the wells 9, 19, 29 may be different. It is to be appreciated that the height H2, length L2 and width of each of the wells 9 can be adjusted to adjust the volume of the fluid sample which is provided and retained by the wells, and which is subsequently delivered to the assays. The length LI of each of the microfluidic cavities 11, 111, 211 along the direction of the channel from the first region 4 to the second region 6 is between 0.5mm and 10 mm, and optionally is 4.6 mm. The length of each microfluidic cavity is greater than the length of its associated well. In an alternative embodiment, the length of each microfluidic cavity is the same as the length of its associated well. The channel 5 may comprise a hydrophilic agent, such as PBS-Tween, which is coated on the channel 5 surface and interacts with the fluid sample to increase the hydrophilicity of the channel 5. This advantageously increases the speed at which the fluid sample runs along the channel 5 and hence speeds up operation of the microfluidic device 1. The channel 5 may comprise a covering such as an adhesive film or lid located over the channel 5 on the opposite side of the channel 5 to the wells 9, 19 29. The covering improves the channel's 5 ability to draw fluid via capillary action due to increased surface area of the channel 5. In use, a user applies a fluid sample such as blood to the first region 4. The fluid sample is transferred from the first region 4 to the second region 6 along the channel 5 by capillary action. As the fluid sample travels along the channel 5 it enters the first well 9, the second well 19 and the third well 29 via their respective inlets 10 which are fluidly connected to the channel 5. A portion of the fluid sample is therefore received in each of the wells and retained therein by capillary forces, which may include surface tension. If an absorbent pad 16 is present, then a user waits until the absorbent pad has drawn the fluid sample from the channel 5 before connecting the portion of the fluid sample in each of the wells to an associated assay. The portion of the fluid sample is retained in each of the wells 9, 19, 29, and is not drawn from the wells by the absorbent pad 16. Typically, an assay comprises an absorbent pad. The portion of the fluid sample which is in each of the wells exits the well in which it is stored when the fluid contacts an absorbent pad of an assay, wherein the absorbent pad draws the portion of the fluid sample out of the well. The or each assay may be a lateral flow assay, a well based assay or an ELISA assay. The or each assay may comprise an absorbent pad for connecting to the portion of the fluid sample in a well. The absorbent pad may be a pad of a processing layer. The assays may be physically unconnected to the microfluidic device or the assay(s) may be integrated with the microfluidic device, as described in relation to Figs. 6A, 6B, 7, 8A and 8B. Figures 5A-5D show the channel 5 and one of the wells, such as the first well 9, during varying stages of the operation of the device. Figure 5A shows the fluid sample 100 flowing along the channel 5 from the first region 4 towards the second region 6, along the direction indicated by arrow C, before entering the first microfluidic cavity 11. Figure 5B shows when the microfluidic cavity 11 and the first well 9 have been filled by the fluid sample. Figure 5C shows the fluid moving along the channel 5 towards the second region 6. If the absorbent, pad 16 is present then the absorbent pad 16 draws the fluid sample from the channel 5 but the portion of the fluid sample is retained in the well 9, as show in Fig. 5D. Figs. 5A-5D only show the fluid sample in relation to the first well 9 but it is to be appreciated that the fluid sample also moves along the channel 5 and into the second and third wells 19, 29, in a corresponding way to that described in relation to the first well 9. Also, as noted, it is possible that the device may only comprise one well such as the first well 9. Referring to Figures 6A, 6B, 7, 8A and 8B, a microfluidic device 18 according to another embodiment of the invention is shown. The microfluidic device of Figs. 6A to 8B has corresponding features to the microfluidic device 1 which is shown and described in relation to Figs. 1A, IC, 2, 3, 4A and 4B but features of the microfluidic device are mounted on a platform 131. Figs. 6A to 8B retain the same reference numerals as those used in relation to the earlier figures. The assays 2A, 2B, 2C are mounted on a base 130. The platform 131 is movable relative to the base 130 between a filling position for allowing the fluid sample to be received in the first region 4 and a test position for allowing the portion of the fluid sample to be delivered from the wells 9, 19, 29 to an associated assay 2. In other words, in the test position, the portion of the fluid sample in the first well 9 can be delivered to a first assay 2A, the portion of the fluid sample in the second well 19 can be delivered to a second assay 2B and the portion of the fluid sample in the third well can be delivered to a third assay 2C. In the filling position, the portion of the fluid sample in the or each well cannot be delivered to its associated assay. The portion of the fluid sample in the first well 9 cannot be delivered to the first assay 2A, the portion of the fluid sample in the second well 19 cannot be delivered to the second assay 2B and the portion of the fluid sample in the third well cannot be delivered to the third assay 2C. Fig. 6A shows the platform 131 in the filling position, and Fig. 6B shows the platform 131 in the test position. When the platform 131 is in the filling position, the outlet 12 of each of the wells is spaced from the assays 2A, 2B, 2C such that the portion of the fluid in each of the wells 9 cannot contact the assays 2A, 2B, 2C. This ensures that the fluid sample is not prematurely delivered to the assays 2A, 2B, 2C before the wells 9, 19, 29 have been filled with the sample fluid. This also ensures that fluid sample is not prematurely delivered to the assays 2A, 2B, 2C before the fluid sample has been drawn from the channel 5, which ensures no fluid sample present in the channel 5 is delivered to the assays 2A, 2B, 2C. When the platform is in the test position, the outlet 12 of each of the wells is pushed into the absorbent pad of each of the assays 2A, 2B, 2B, which connects the fluid sample in each of the wells to the absorbent pads of the assays 2A, 2B, 2C to allow the fluid sample to be drawn out from each of the wells 9, 19, 29. Alternatively, in the test position, the outlet of each of the wells may not be pushed into the absorbent pad of each of the assays and instead in the test position the portion of the fluid sample in each of the wells is connected with the absorbent pad of each of the lateral flow assays. In the test position, each of the wells 9, 19, 29 is positioned relatively closer to the assays 2A, 2B, 2C than in the filling position for allowing the portion of the fluid sample in the wells to be connected to an associated assay 2A, 2B, 2C. The device shown in Figures 6A and 6B comprise the stoppers 21, as shown in relation to Figure 3. The stoppers 21 are configured to abut the top surface of the base 130 when the platform is in the testing position. As shown in the Figures, the base 130 may comprise a window 134 located above the assays 2A, 2B, 2C for allowing the user to view the results of the assays 2A, 2B, 2C after the portion of the fluid sample has been transferred to the assays 2A, 2B, 2C. The platform 131 is connected to the base 130 by a hinge 132. The hinge 132 is a living hinge. In other words, the hinge 132 is a thin flexible hinge which is made from the same material as the base 130 and the platform 131 which are the two rigid pieces which it connects. The platform 131 may be biased away from the base 130 towards the filling position by the resilient nature of the hinge 132. The hinge 132 is located closer to the second region 6 than the first region 4. The channel 5 is declined from the first region 4 towards the second region 6 when the platform is in the filling position. This advantageously makes the fluid sample flow along the channel 5 faster, and hence speeds up operation of the microfluidic device 18. The longitudinal axis of the channel 5 rotates through 5 to 15 degrees, and optionally through around 10 degrees when the platform is moved from the filing position to the test position. The base 130 comprises a planar surface 133 on which the assays 2A, 2B, 2C are mounted, as seen in Figs. 8A and 8B. The longitudinal axis of the channel is parallel or substantially parallel to the planar surface 133 when the platform 131 is in the test position. The fluid in the wells 9, 19, 29 may contact the assays 2A, 2B, 2C at the same time. When the platform 131 is in the filling position, the channel 5 may be declined at an angle of 5 to 15 degrees, optionally 10 degrees, relative to the planar surface 133. In other embodiments, channel 5 may be parallel with the planar surface 133 in the filling position. The microfluidic device 18 further comprises a holding mechanism for holding the platform in the filling position. The holding mechanism comprises a sprung arm 140 connected to the platform 131. The sprung arm 140 has a protrusion 141. The protrusion 141 abuts against an abutment surface 142 of the base 130 for preventing the platform 131 from moving from the filling position to the test position. The holding mechanism may be implemented in other ways, for example the arm may be connected to the base 130 and the protrusion may be provided on the platform 131, or the releasable locking mechanism may be a breakable seal or comprise a push button. In use, a user presses down on the platform 131 which causes the protrusion 141 to press against the abutment surface 142, and the sprung arm 140 to flex to allow the protrusion 141 to move past the abutment surface 142 and the platform 131 to move towards the base 130. The microfluidic device 18 further comprises a locking mechanism for locking the platform in the testing position. The locking mechanism comprises the sprung arm 140. When the platform 131 reaches the testing position, the protrusion 141 is biased by the sprung arm 140 into a recess 152 connected to the platform 130. The locking mechanism is engaged which prevents the platform 131 from moving away from the base 130. The locking mechanism can be seen as a type of snap fit mechanism. It is to be appreciated that other mechanisms configured to retain the platform 131 in the testing position are intended within the scope of the present invention. In yet further embodiments the holding mechanism and / or the locking mechanism are absent. Although a hinge 132 is described herein, alternative mechanisms for movably connecting the platform 131 and the base 130 are within the scope of the present invention such as providing guide rails and / or a spring between the platform 131 and the base 130. The microfluidic device 18 may comprise a finger pricking device (not shown in the Figures) which comprises a needle for piercing the user's finger to obtain a blood sample which can then be inserted into the region 4 to act as the fluid sample. The provision of the finger pricking device is optional. It is important to ensure the fluid sample is not prematurely delivered to the assays 2A, 2B, 2C before the wells 9, 19, 29 have been filled with the correct amount of sample fluid. With reference to Figure 9, the operation of the microfluidic device 1 and the microfluidic device 18 will now be described. The first step 301 comprises a user providing a fluid sample into the first region 4. The second step 302 comprises a user then waiting until the or each well 9, 19, 29, has received a portion of the fluid sample. If a absorbent pad 16 is provided, then the second step 302 may further comprise waiting until the absorbent pad has drawn the fluid sample from the channel 5. In a third step 303, which is performed after the second step 302, the method comprises connecting the portion of the fluid sample in the or each well to an associated assay 2 for drawing the fluid sample from the or each well. If the microfluidic device comprises a platform and a base, then the third step 303 may comprise moving the platform relative to the base between a filling position for allowing the fluid sample to be received in the first region and a test position for allowing the portion of the fluid sample to be delivered from the or each well to an associated assay of the one or more assays. If the microfluidic device comprises a holding mechanism for holding the platform in the filling position, then the method comprises a user releasing the holding mechanism prior to moving the platform relative to the base. If the microfluidic device comprises a locking mechanism for locking the platform in the testing position, then the method may further comprise engaging the locking mechanism to hold the platform in the testing position. These methods advantageously allow for a user to ensure a volume of sample fluid can be provided to the assays 2A, 2B, 2C and further to ensure the assays 2A, 2B, 2C are not overflowed or underfilled with fluid sample. In embodiments which comprise more than one well 9, a volume of sample fluid can be provided to more than one assay 2A, 2B, 2C from a single original fluid sample provided to the first region 4. If a absorbent pad 16 is provided then this draws the fluid from the channel 5 which may enable a precise volume of fluid to be delivered to the assays from each of the wells. It will be appreciated that both the precise and relative dimensions of the features of the device which are described herein will vary depending on factors such as the type of fluid in the fluid sample, the volume of the fluid sample required for the assays, the material from which the channel and wells are made of and any coatings applied thereto, for example. Different configurations of the microfluidic device are also possible. Numerous modifications and variations of the present disclosure are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein. Various features may be combined in any matter suitable to implement the technique. It is to be appreciated that the assays discussed in any of the previous embodiments may be any assay for example, lateral flow assays, well based assays, or ELISAs.

Claims

1. A microfluidic device for delivering fluid to one or more assays, wherein the microfluidic device comprises:a first region for receiving a fluid sample;a channel;a second region, wherein the channel connects the first region to the second region, and wherein the channel is for transferring the fluid sample from the first region to the second region via capillary action; andat least one well for receiving and retaining a portion of the fluid sample, the or each well comprising an inlet which is fluidly connected to the channel, and an outlet for delivering the portion of the fluid sample to an assay of the one or more assays.

2. The microfluidic device according to claim 1, wherein the or each well is configured to retain the portion of the fluid sample by capillary forces.

3. The microfluidic device according to claim 1 or 2, wherein the second region comprises an absorbent pad for drawing the fluid sample from the channel when the fluid sample contacts the absorbent pad.

4. The microfluidic device according to any preceding claim, wherein the width of the inlet of the or each well is smaller than the width of the channel.

5. The microfluidic device according to any preceding claim, wherein the channel comprises at least one microfluidic cavity which is fluidly connected to the inlet of an associated well of the at least one wells.

6. The microfluidic cavity according to claim 5, wherein the width of the or each microfluidic cavity is greater than the width of the inlet of its associated well.

7. The microfluidic device according to claim 5 or 6, wherein the at least one microfluidic cavity comprises a first microfluidic cavity, and wherein the channel has a first channel width between the first region and the first microfluidic cavity, wherein the width of the first microfluidic cavity is greater than the first channel width.

8. The microfluidic device according to claim 7, wherein the ratio of the first channel width to the width of the first microfluidic cavity is 0.7 to 1.

9. The microfluidic device according to claim 7 or 8, wherein the at least one microfluidic cavity comprises a second microfluidic cavity, and wherein the channel has a second channel width between the first microfluidic cavity and the second microfluidic cavity, wherein the width of the second microfluidic cavity is greater than the second channel width.

10. The microfluidic device according to claim 9, wherein the first channel width is the same or substantially the same as the second channel width.

11. The microfluidic device according to claim 9 or 10, wherein the ratio of the second channel width to the width of the second microfluidic cavity is 0.7 to 1.

12. The microfluidic device according to any of claims 5 to 11, wherein the or each microfluidic cavity has a length along the direction of the channel from the first region to the second region.

13. The microfluidic device according to claim 12, wherein the length of the or each microfluidic cavity is greater than the length of the inlet of its associated well along the direction of the channel from the first region to the second region.

14. The microfluidic device according to claim 12 or 13, wherein the length of the or each microfluidic cavity is around 0.5mm to 10mm, and optionally around 4.6mm.

15. The microfluidic device according to any preceding claim, wherein the height of the or each well between the inlet and the outlet is around 0.5mm to 50mm, and optionally around 5mm.

16. The microfluid device according to any preceding claim, wherein the length of the or each well along the direction of the channel from the first region to the second region is around 0.5mm to 10mm, and optionally around 4mm.

17. The microfluidic device according to any preceding claim, wherein the or each well comprises sidewalls which surround the outlet of the or each well.

18. The microfluidic device according to claim 17, wherein the sidewalls have a thickness of 0.5 mm or less, and optionally wherein the sidewalls have a thickness of around 0.1 mm.

19. The microfluidic device according to claim 17 or 18, wherein the sidewalls comprise at least one recess for assisting the delivery of the portion of the fluid sample to the assay.

20. The microfluidic device according to any preceding claim, wherein the width of the outlet of the or each of the wells is around 0.1mm to 2mm, and optionally around 0.45mm.

21. The microfluidic device according to any preceding claim, wherein the volume of the or each well is around 5 to 40 microlitres, optionally wherein the volume of the or each well is around 6 to 10 microliters and optionally wherein the volume of the or each well is around 6 microlitres.

22. The microfluidic device according to any preceding claim, wherein the or each well has a longitudinal direction which is aligned with the direction of the channel from the first region to the second region.

23. The microfluidic device according to any preceding claim, wherein the first region comprises a slope which is declined towards the channel for assisting the transfer of the fluid sample from the first region to the channel.

23. The microfluidic device according to any preceding claim, wherein the or each well comprises a plurality of wells.

24. The microfluidic device according to any preceding claim, wherein the channel comprises a hydrophilic agent, and optionally wherein the hydrophilic agent comprises PBS-Tween.

25. The microfluidic device according to any preceding claim, wherein the device further comprises an adhesive film which is located over the channel on the opposite side of the channel to the or each of the at least one wells.

26. A system comprising the microfluidic device as defined in any one of the preceding claims, and one or more assays, and optionally wherein the or each well is movable relative to the assays.

27. The microfluidic device according to any of claims 1 to 25, wherein the device further comprises a platform on which the channel and the or each well are mounted,and a base for mounting the one or more assays, wherein the platform is movable relative to the base between a filling position for allowing the fluid sample to be received in the first region and a test position for allowing the portion of the fluid sample to be delivered from the or each well to an associated assay of the one or more assays.

28. The microfluidic device according to claim 27, wherein the first region and / or the second region are mounted on the platform.

29. The microfluidic device according to claim 27 or 28, further comprising the one or more assays, wherein the one or more assays are mounted on the base.

30. The microfluidic device according to any one of claims 27 to 28, where the platform is connected via a hinge to the base, and optionally wherein the hinge is a living hinge.

31. The microfluidic device according to claim 30, wherein the hinge is located closer to the second region than the first region.

32. The microfluidic device according to any one of claims 27 to 30, wherein the longitudinal axis of the channel is declined from the first region towards the second region when the platform is in the filling position.

33. The microfluidic device according to any one of claims 27 to 32, wherein the longitudinal axis of the channel is rotated through 5 to 15 degrees, and optionally rotated through around 10 degrees, when the platform is moved from the filling position to the test position.

34. The microfluidic device according to any one of claims 27 to 32, wherein the base comprises a planar surface for mounting the one or more assays, and wherein the channel is parallel or substantially parallel to the planar surface when the platform is in the test position.

35. The microfluidic device according to any one of claims 27 to 34, wherein the device further comprises a holding mechanism for holding the platform in the filling position.

36. The microfluidic device according to any one of claims 27 to 35, wherein the device further comprises a locking mechanism for locking the platform in the testing position.

37. A method of using a microfluidic device for delivering fluid to one or more assays, wherein the microfluidic device comprises:a first region for receiving a fluid sample;a channel connecting the first region to the second region for transferring the fluid sample from the first region to the second region via capillary action; andat least one well for receiving and retaining a portion of the fluid sample, the or each well comprising an inlet which is fluidly connected to the channel, and an outlet for delivering the portion of the fluid sample to an assay of the one or more assays, the method comprising providing the fluid sample into the first region.

38. The method according to claim 37, wherein the method further comprises waiting until the or each well has received a portion of the fluid sample before connecting the portion of the fluid sample in the or each well to an associated assay for drawing the fluid sample from the or each well.

39. The method of claim 38, wherein the second region comprises an absorbent pad for drawing the fluid sample from the channel when the fluid sample contact the absorbent pad, and wherein the method further comprises waiting until the absorbent pad has drawn the fluid sample from the channel before connecting the portion of the fluid sample in the or each well to its associated assay for drawing the fluid sample from the or each well.

40. The method of any one of claims 37 to 39, wherein the microfluidic device is according to any one of claims 1 to 36.

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