Fluidic card assembly

Abstract

A fluidic card assembly (1) comprises an inlet (20) for introducing a fluid to the fluidic card assembly (1), a turbulent flow portion (30) downstream of the inlet (20), the turbulent flow portion (30) comprising a widening fluid channel (31) whereby a fluid introduced via the inlet (20) channel undergoes turbulence, and a laminar flow portion (40) downstream of the turbulent flow portion (30). The laminar flow portion (40) is configured to allow fluid passing from the turbulent flow portion (30) into the laminar flow portion (40) to establish a laminar flow pattern, and is configured to house a biochip (44) such that a fluid in the laminar flow portion (40) may be in contact with the biochip (44).

Claims

1. A fluidic card assembly comprising: an inlet comprising an inlet channel for introducing a fluid to the fluidic card assembly, a turbulent flow portion downstream of the inlet, the turbulent flow portion comprising a widening fluid channel whereby a fluid introduced via the inlet channel undergoes turbulence, and a laminar flow portion downstream of the turbulent flow portion, the laminar flow portion being configured to allow fluid passing from the turbulent flow portion into the laminar flow portion to establish a laminar flow pattern; and wherein the laminar flow portion is configured to house a biochip such that a fluid in the laminar flow portion may be in contact with the biochip; wherein the fluidic card assembly further comprises: an exhaust portion downstream of the laminar flow portion, the exhaust portion comprising a fluid channel of a greater depth than the laminar flow portion, wherein the exhaust portion comprises a lower wall arranged at a freater depth than a lower wall of the laminar flow portion.

2. The fluidic card assembly of claim 1, wherein the fluidic card assembly further comprises a biochip housed inside the laminar flow portion.

3. The fluidic card assembly of claim 1, wherein the laminar flow portion comprises a fluid channel of a constant width.

4. The fluidic card assembly of claim 1, wherein the laminar flow portion further comprises a recess in which a biochip may be situated.

5. The fluidic card assembly of claim 4, wherein the biochip is housed inside the recess, and where the recess permits a surface of the biochip situated therein to be flush with an interior surface of the laminar flow portion.

6. The fluidic card assembly of claim 1, wherein the inlet comprises an aperture through which fluid may pass into the turbulent flow portion, the aperture having a cross-sectional area in the range of 0.6-0.9 mm.sup.2.

7. The fluidic card assembly of claim 1, wherein the fluid channel of the turbulent flow portion comprises an interior surface that: tapers outwardly from the inlet in one plane at an angle in the range of 50-60°, and comprises opposed planar sections, each having an area in the range of 20-22 mm.sup.2.

8. The fluidic card assembly of claim 1, wherein an interior surface of the laminar flow portion comprises opposed planar sections.

9. The fluidic card assembly of claim 1, wherein the exhaust portion further comprises one or more outlets for extracting fluid from the fluidic card assembly.

10. The fluidic card assembly of claim 1, wherein the inlet, turbulent flow and laminar flow portions are sections of a continuous depressed channel formed in a solid housing.

11. The fluidic card assembly of claim 10, wherein the exhaust portion is formed in the same housing as the inlet, turbulent flow and laminar flow portions.

12. The fluidic card assembly of claim 10, wherein the assembly further comprises a removable cover secured over the channel so as to form an upper wall of the channel.

Description

(1) An example of a fluidic card assembly according to the present invention and methods for its use in delivering a fluid sample to a biochip will now be described, with reference to the accompanying figures. In the figures:

(2) FIG. 1 illustrates a fluid channel formed in a casing;

(3) FIG. 2 shows an alternative perspective view of the fluid channel of FIG. 1, illustrating the depth profile of the channel; and

(4) FIG. 3 shows a cutaway view of the channel of FIGS. 1 and 2 and a cover for sealing the top of the channel.

(5) FIGS. 1, 2 and 3 depict an exemplary embodiment of the invention. The fluidic card assembly 1 includes a fluid channel 11 formed within a casing 10. The fluid channel is divided into a number of portions 20, 30, 40, 50 through which a fluid flows consecutively after being introduced to the fluidic card assembly. A cover 12 is provided, and may be secured over the fluid channel 11 so as to seal the fluid channel and allow fluid to be introduced and extracted only via designated inlets and outlets. Securing the cover 12 over the fluid channel 11 causes a surface 13 of the cover to form an upper wall along the extent of the channel.

(6) In this embodiment, the casing 10 is in the form of a rigid card, and the fluid channel 11 is formed as a depression therein. However, the fluid channel 11 could be formed by alternative means, such as a pipe formed to include the features listed above. The cover 12 is preferably a flexible film, but may alternatively be, for example, in the form of a rigid sheet that could be clamped, screwed or fixed by one or more hinges to the casing 10. The cover 12 may be fixed to the casing 10 by laser welding. The cover 12 may be removable so as to allow access to the interior of the assembly.

(7) The casing 10 and the cover are preferably made of plastics or glasses that do not react with the sample compounds and solvents typically used in biochip assays. It is also preferable that the materials used to construct the fluidic card assembly, and particularly the cover, are transparent, so as to permit a fluid located therein to be monitored visually, and to permit analysis of the biochip 44 without requiring the fluidic card assembly to be disassembled. For example, chemiluminscence, which may be observed when test regions on a biochip are activated, might be measured at wavelengths in the range of 300-500 nm. The cover 12 should therefore be transparent over at least this range for assays involving the measurement of chemiluminescence. The cover 12 may, for example, be provided in the form of a polypropylene foil.

(8) An inlet portion 20 comprises an inlet channel 21 that allows a fluid to be introduced to the fluidic card assembly. An upper wall of the inlet channel 21 is formed when the cover 12 is secured over the fluid channel 11. The inlet channel 21 terminates at an aperture 22, through which a fluid may pass into the turbulent flow portion 30. The inlet channel 21 and the aperture 22 preferably have a cross-sectional area in the range of 0.6-0.9 mm.sup.2.

(9) The turbulent flow portion 30 of the fluidic card assembly is bounded by two outwardly-tapering side walls 31 formed at an angle preferably in the range of 50-60° to the direction D of flow of a fluid exiting the inlet channel 21 via the aperture 22, and by a lower wall 32, preferably having an area in the range of 20-22 mm.sup.2. An upper wall of the turbulent flow portion 30 is formed when the cover 12 is secured over the fluid channel 11.

(10) The tapering of the side walls 31 results in the turbulent flow portion 30 having a cross-sectional area that increases in the downstream direction D. This configuration causes a fluid travelling in the downstream direction D to decelerate, thereby subjecting the fluid to inertial forces sufficient to induce turbulence. The disordered flow pattern that arises where turbulent flow occurs causes the sample to be substantially homogenised.

(11) Downstream of the turbulent flow portion 30 is the laminar flow portion 40. The laminar flow portion is bounded by parallel side walls 41 and a lower wall 42. Formed in the lower wall is a recess 43, which is constructed so as to house a biochip 44. An upper wall of the laminar flow portion 40 is formed when the cover 12 is secured over the fluid channel 11. Preferably, the lower wall of the laminar flow portion has an area in the range of 60-170 mm.sup.2.

(12) The laminar flow portion 40 has an approximately constant cross-sectional area in the downstream direction D, so the inertial forces experienced by a fluid travelling through this portion are less than in the turbulent flow portion 30. Furthermore, the increase in the cross-sectional area of the fluid channel through the turbulent flow portion causes a substantial reduction in the flow speed of the fluid after passing through the aperture 22. Subject to the fluid being introduced under suitable conditions, the flow pattern will therefore transition from turbulence to laminarity between the turbulent and laminar flow portions. In embodiments with the preferred dimensions described herein, fluid is typically passed through the fluid channel 11 at a rate of 5-200 μL per minute.

(13) The biochip 44 is a thin slate with dimensions of approximately 9×9 mm. One or more discrete test regions that are capable of immobilising specific biomarkers present in a fluid are arranged on a surface 45 of the biochip in a conventional manner.

(14) The biochip 44 is secured inside the recess 43 such that the surface 45 is on the open side of the recess and may be in contact with a fluid passing through the laminar flow portion. The recess is preferably constructed such that the surface 45 of the biochip is level with the lower wall 42 of the laminar flow portion when the biochip 44 is secured inside the recess. If the dimensions of the biochip and the recess are closely matched, it may not be necessary to provide any additional means of securing the biochip. Otherwise, various means of securing the chip may be employed, such as glue, a low-tack adhesive that permits the biochip to be removed from the fluidic card assembly for further analysis or storage after an assay has been performed, or clips that hold the chip by its edges.

(15) The combination of the turbulent and laminar flow portions as described herein provides a means of first homogenising a sample via turbulence, then ensuring an even distribution of the sample across the surface of a biochip.

(16) Downstream of the laminar flow portion 40 is an exhaust portion 50. A sloping section 51 connects the lower wall 42 of the laminar flow portion to the lower wall 52 of the exhaust portion, thereby causing the depth of the fluid channel to increase. FIG. 2 illustrates the depth profile of the fluid channel 11. The exhaust portion also includes parallel side walls 53 that are formed at a greater separation than those of the laminar flow portion, and an end wall 55. An upper wall of the exhaust portion 50 is formed when the cover 12 is secured over the fluid channel 11. Typically, the lower wall of the exhaust portion has an area of 250 mm.sup.2. A plurality of outlets 54 are formed in the downstream end of the exhaust portion, via which a fluid may be extracted from the fluidic card assembly. Air or other gasses may be present in the exhaust portion, thereby mitigating the effect of backpressures created in fluid exiting the assembly and ensuring that the laminar flow pattern in the laminar flow portion is not disrupted. Air or gas in the exhaust portion 50 will be compressed as fluid is urged through the assembly, causing backpressures to be distributed evenly across the plane of motion of the fluid. This effect acts to encourage a uniform flow pattern through the laminar flow portion 40, and mitigates any non-uniformity that might otherwise be caused by the differing characteristics of the surface of the biochip and the surrounding surfaces of the laminar flow portion.

(17) A user may wish to be able to select or prepare biochips suited to particular applications for use with a fluidic card assembly at will. In such instances, the fluidic card assembly of the above embodiment of the invention may be provided without a biochip. The user would manually place a biochip inside the recess 43 and then use the cover 12 to seal the assembly.

(18) One method of using the embodiment of the invention described above involves the introduction of a single fluid sample to the fluidic card assembly via the inlet portion 20. A pressure is maintained so as to cause the fluid to move through the turbulent flow portion 30, wherein the sample experiences turbulence and is substantially homogenised. This pressure could be created using, for example, a pump or a syringe. The fluid then passes into the laminar flow portion 40 and over the biochip 44, activating discrete test regions corresponding to the biomarkers present. Homogenising the fluid upstream of the biochip 44 provides an even distribution of biomarkers across the test surface 45, thereby ensuring that the results of an assay carried out with this apparatus are not biased by initial inhomogeneity in the fluid sample.

(19) The fluid to be homogenised in the fluidic card assembly may be, a single liquid solution, or could include other phases. For example, a user may wish to test a sample in the form of a suspension, which would contain solid particles. The turbulence experienced by the fluid in the turbulent flow portion of the fluidic card assembly would serve to homogenise the distribution of these particles. In a specific example, a user may use a fluidic card assembly according to the present invention to perform an assay involving solid material that has been freeze-dried and later re-entered into the form of a suspension. In another example, the fluid may include an emulsion. Liquid droplets suspended in the sample would be redistributed by turbulence, and the quality of the emulsion may be improved in instances where the turbulent flow pattern is capable of further splitting the droplets.

(20) Fluid samples in other forms may also be used with the embodiment of the invention described above. It may be desirable that a plurality of samples are stored separately but analysed as one. In such instances, the samples may be injected either simultaneously or consecutively into the fluidic card assembly 1, and be mixed in the turbulent flow portion 30. As the inlet channel 21 is typically narrow, the Reynolds number of the system therein is low, and fluids being introduced to the assembly consecutively may initially only mix by diffusion. After entering the turbulent flow portion 30, consecutively introduced fluids also experience mixing by currents.

(21) Where fluids are injected consecutively, it is preferable that the total volume of fluid to be mixed is less than the capacity of the turbulent flow portion 30 so as to ensure complete mixing of the sample.

(22) In an example in which multiple fluids are intended for simultaneous use with a fluidic card assembly according to the present invention, a user may wish to analyse the products of a chemical reaction in its immediate aftermath. They would introduce via the inlet 20 a plurality of fluids containing the reagents to be mixed, which would then interact in the turbulent flow portion 30, wherein the reaction would proceed. The products of the reaction would then be distributed evenly over the test surface 45 of the biochip 44 in the laminar flow portion 40.

(23) The fluidic card assembly 1 of the above embodiment of the invention is intended for use with a conventional analyser. An analyser is capable of determining which discrete test regions have captured biomarkers, thereby providing a record of the composition of a sample. For example, the discrete test regions on the biochip 44 may be configured to produce chemiluminescence when capturing specific biomarkers. In this case an analyser would record the emission of light from the surface 45 of the biochip to determine which discrete test regions have been activated, and therefore which biomarkers are present. Alternatively, biomarkers such as DNA molecules may be labelled with fluorescent tags. Exposing the biochip 44 to, for example, ultraviolet radiation after passing a sample through the assembly would cause fluorescence to be observed where biomarkers are captured.

(24) Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only.