Interface component for a microfluidic device, assemblies, and method for extracting particles from a sample

Abstract

All interface component (40), suitable for cooperating with a microfluidic device (1), the interface component comprising, one or more elements (41) which can be selectively connected to a pneumatic system (71 a,71 b) which can provide a positive and/or negative air flow to the one or more elements (41); wherein each of the one or more elements 141) comprises, an input port (42) which can be selectively fluidly connected to a pneumatic system (71 a,71 b); and a flow restrictor (43) according to a further aspect of the present invention; the flow restrictor (43) being arranged in fluid communication with the input port (42), wherein the flow restrictor (43) can restrict the flow of fluid through the element (41); and an aerosol filter (49) which is arranged to be in fluid communication with the flow restrictor (43); and wherein the interface component (40) further comprises one or more outlets (45), each of the one or more outlets (45) being in fluid communication with a respective element (41), so that fluid can flow from the element (41) out of the interface component (40) via the one or more outlets (45); and wherein each of the one or more outlets (45) can be selectively arranged to be in fluid communication with a respective reservoir (105,1(16,107,108) of a microfluidic device (1). There is further provided a corresponding method and assembly for extracting ferromagnetic, paramagnetic and/or diamagnetic particles from a sample.

Claims

1. A flow restrictor suitable for use in an interface component, the flow restrictor comprising, an inlet member which has an inlet channel defined therein; an outlet member which has an outlet channel defined therein; wherein the inlet channel and outlet channel are fluidly connected; and a capillary member which comprises an intermediate channel which is located between the inlet and outlet members, and wherein the intermediate channel is in fluid communication with the inlet channel and outlet channel; and wherein the intermediate channel has dimensions smaller than the dimensions of the inlet and outlet channels; wherein the flow restrictor comprises a male member and female member which are configured so that they can mechanically cooperate with each other so that the male and female members can be fixed together; wherein the male member comprises the inlet member, and the female member comprises the outlet member; and wherein the male and female member each have a pocket which can receive a portion of the capillary member so that a portion of capillary member is contained within the pocket in the male member, and another portion of the capillary member is contained within pocket of the female member.

2. A flow restrictor according to claim 1 wherein at least 0.5 mm of the length of the capillary member extends out of the pocket of the male member.

3. A flow restrictor according to claim 1 further comprising an o-ring located at an interface between the male and female members.

4. A flow restrictor according to claim 3 wherein the capillary member extends through the o-ring.

5. A flow restrictor according to claim 1 wherein said capillary member is composed of glass.

6. A flow restrictor according to claim 1 wherein the depth of the pocket in the male member is such that when the capillary member is positioned into the pocket so that capillary member abuts a base of the pocket, at least 0.5 mm of the length of the capillary member extends out of the pocket of the male member.

7. A flow restrictor according to claim 1 wherein the depth of the respective pockets in the male member and female member is between 1-20 mm.

8. A flow restrictor according to claim 1 wherein the male member further comprises ribbing defined on an outer surface thereof and/or the female member further comprises ribbing defined on an outer surface thereof.

9. A flow restrictor assembly comprising, a flow restrictor according to claim 1, wherein the male member and female member can mechanically cooperate such that the pockets in each member align to define a volume which can receive a capillary member; and a plurality of capillary members each of which has an intermediate channel defined therein; wherein the length of each the capillary members is different such that the lengths of their respective intermediate channels are different; and wherein each of the capillary members being dimensioned such that they can be fully contained within the volume defined by the pockets in the male and female members.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which:

(2) FIGS. 1a & 1b show a perspective view of a microfluidic device according to an embodiment of the present invention;

(3) FIG. 1c shows a magnified perspective view of a first junction of said microfluidic device;

(4) FIG. 1d provides a cross sectional view of a part of the microfluidic device taken along line ‘A’ of FIG. 1b;

(5) FIG. 1e is a plan view of part of the microfluidic device showing one of the main channels and its respective two inlet subsidiary channels and respective two outlet subsidiary channels;

(6) FIG. 1f provides a magnified view of a second junction of said microfluidic device;

(7) FIG. 2a provides a perspective view of an assembly according to a further aspect of the present invention; and FIG. 2b provides a cross-sectional view taken along line ‘A’ in FIG. 2a;

(8) FIG. 3a illustrates the arrangement of the sample and buffer fluid in the main channel and two inlet subsidiary channels; and FIG. 3b illustrates the arrangement of the sample and buffer fluid in the main channel and two outlet subsidiary channels;

(9) FIGS. 4a and 4b provide perspective views of an interface component according to a further aspect of the present invention;

(10) FIG. 5a provides a perspective, part cross-sectional, view of a flow restrictor of an element of the interface component shown in FIGS. 4a and 4b;

(11) FIG. 5b provides an exploded view of the flow restrictor of an element of the interface component shown in FIGS. 4a and 4b;

(12) FIGS. 6a and 6b each provide a cross sectional view of a magnetic assembly of the interface component shown in FIGS. 4a and 4b;

(13) FIG. 6c provides a perspective view the magnetic assembly of the interface component shown in FIGS. 4a and 4b;

(14) FIG. 7 provides a perspective view of an assembly according to a further aspect of the present invention.

DETAILED DESCRIPTION OF POSSIBLE EMBODIMENTS OF THE INVENTION

(15) FIGS. 1a and 1b provide perspective views of a microfluidic device 1 according to an embodiment of the present invention. The microfluidic device 1 comprises a pallet 3 which has a first surface 4a and a second, opposite, surface 4b. The pallet 3 is composed of transparent material, such as transparent thermoplast. FIG. 1a is a perspective view of a microfluidic device 1 showing the first surface 4a; and FIG. 1b is a perspective view of a microfluidic device 1 showing the second, opposite, surface 4b.

(16) Referring to FIG. 1a, the first surface 4a has four main channels 5 defined therein. It will be understood that any number of main channels may be defined in the first surface 4a. Each of the main channels 5 a first end 5a and a second, opposite, end 5b.

(17) For each main channel 5 there is provided are two inlet subsidiary channels 6a,6b, each of which is in fluid communication with a respective main channel 5 at a first junction 7 which is located at the first end 5a of the respective main channel 5. Corresponding two outlet subsidiary channels 8a,8b each of which is in fluid communication with a respective main channel 5 at a second junction 9 which is located at the second, opposite, end 5b of the respective main channel 5. It will be understood that any number of inlet subsidiary channels and any number of outlet subsidiary channels may be provided for each main channel 5; however most preferably the number of inlet subsidiary channels will correspond to the number of outlet subsidiary channels. The two inlet subsidiary channels 6a,6b mirror one another, and the and two outlet subsidiary channels 8a,8b mirror one another.

(18) A film 18, overlays the main channels 5, and the respective inlet subsidiary channels 6a,6b and outlet subsidiary channels 8a,8b so as to confine the flow of fluids to within the respective channels 5,6a,6b,8a,8b. The film 18 is removably attached to (or fixed to) the first surface 4a so that it can be selectively removed and attached to the first surface 4a. The film is composed of transparent material, such as transparent thermoplast, so as to allow a user to observe the flow of fluids within the microfluidic device

(19) FIG. 1c provides a magnified view of a first junction 7; it will be understood that all of the first junctions 7 in the microfluidic device 1 will have a similar configuration. It can be seen from FIG. 1c that the depth ‘d’ of each of the two inlet subsidiary channels 6a,6b is less than the depth ‘f’ of the main channel 5. Accordingly, there are respective steps 106a, 106b defined at the first junction 7 at the interfaces between each of the inlet subsidiary channels 6a,6b and the main channel 5. At the first junction 7 the two inlet subsidiary channels 6a,6b are arranged to join the main channel 5 at opposite sides 25a,25b of the main channel 5. Both inlet subsidiary channels 6a,6b join the main channel 5 at the same point along the length of the main channel 5; in that respect it should be understood that in the present invention the first junction 7 is defined by the point along the length of main channel 5 where the two inlet subsidiary channels 6a,6b meet the main channel 5.

(20) FIG. 1f provides a magnified view of a second junction 9; it will be understood that all of the second junctions 9 in the microfluidic device 1 will have a similar configuration. It can be seen from FIG. 1f that the depth ‘x’ of each of the two outlet subsidiary channels 8a,8b is less than the depth ‘f’ of the main channel 5. Accordingly, there are respective steps 108a, 108b defined at the second junction 9 at the interfaces between each of the outlet subsidiary channels 8a,8b and the main channel 5. The depth ‘x’ of each of the two outlet subsidiary channels 8a,8b is equal to the depth ‘d’ of the depth of each of the two inlet subsidiary channels 6a,6b. At the second junction 9 the two outlet subsidiary channels 8a,8b are arranged to join the main channel 5 at opposite sides 25a,25b of the main channel 5. Both outlet subsidiary channels 8a,8b join the main channel 5 at the same point along the length of the main channel 5; in that respect it should be understood that in the present invention the second junction 9 is defined by the point along the length of main channel 5 where the two inlet subsidiary channels 6a,6b meet the main channel 5.

(21) Referring to FIG. 1b which provides a perspective view of a microfluidic device 1 showing the second, opposite, surface 4b of the pallet 3. The second, opposite, surface 4b a plurality of grooves 15 defined therein each of which can receive a means for generating a magnetic field (e.g. a magnet). The number of groove 15 defined in the second, opposite, surface 4b correspond to the number main channels 5 defined in the first surface 4a of the pallet 3; therefore in this example four grooves 15 are defined in the second, opposite, surface 4b. Each groove 15 is aligned with a respective main channel 5. Each groove 15 extends along a length (L7) which is equal to the length (L8—see FIG. 1e) of main channel which extends between the first junction 7 and second junction 9, It can be seen that the pallet 3 further comprises a notch 128 which is used for alignment; in particular the notch 128 is used for aligning the microfluidic device 1 into a predefined position in an assembly (such as the assemblies which will be described later).

(22) FIG. 1d provides a cross sectional view, of the microfluidic taken along line ‘A’ of FIG. 1b. FIG. 1d includes a cross sectional view of a groove 15; it will be understood the all of the grooves 15 will have a configuration similar to that shown in FIG. 1d. It can be seen in FIG. 1d the main channel 5 which is defined in the first surface 4a has a rectangular cross section having a width ‘s’ and depth T. The ratio between the width ‘s’ and depth ‘f’ of the main channel 5 is preferably between 0.2 and 5; in this particular example the ratio between the width ‘s’ and depth ‘f’ of the main channel 5 is 1.75. The main channel has a channel bed 5d which is planar, and opposing side surfaces 5e,5f which are perpendicular to the channel bed 5d so as to define the rectangular cross section.

(23) The groove 15 is shown to be aligned with the main channel 5; in other words the centre of the groove 15 is aligned with the centre of main channel 5 as represented by axis 16. The width ‘w’ of the groove 15 tapers. Specifically, side walls 15a,15b defining the groove 15 are slanted so that width ‘w’ of the groove 15 tapers towards a surface 15c which defines a base of the groove 15. The thickness ‘t’ of the pallet 3 between the groove 15 and channel 5 is never below 0.01 mm, and is preferably 0.15 mm (or at least between 0.01-10 mm); more specifically along the axis 16 (on which the centre of the groove 15 and centre of main channel 5 lie) the thickness ‘t’ of the pallet 3 is between 0.01-10 mm, and is preferably 0.15 mm.

(24) In this example shown in FIG. 1d, the surface 15c which defines a base of the groove 15 is flat, however in an another embodiment the surface which defines a base of the groove 15 is curved, and preferably has a radius of curvature between 0.05 mm-0.5 mm; and most preferably has a radius of curvature of between 0.2 mm. In yet another embodiment the groove 15 has a v-shaped cross section.

(25) As shown in FIG. 1b the microfluidic device 1 further comprises a plurality of buffer source reservoirs 106, sample source reservoir 105, buffer drain reservoirs 107 and sample drain reservoirs 108. The number of buffer source reservoirs 106 correspond to the number main channels 5 defined in the first surface 4a of the pallet; therefore in this example four buffer source reservoirs 106 are provided. The number of sample source reservoir 105 correspond to the number main channels 5 defined in the first surface 4a of the pallet; therefore in this example four sample source reservoir 105 are provided. The number of buffer drain reservoirs 107 correspond to the number main channels 5 defined in the first surface 4a of the pallet; therefore in this example four buffer drain reservoirs 107 are provided. The number of sample drain reservoirs 108 correspond to the number main channels 5 defined in the first surface 4a of the pallet; therefore in this example four sample drain reservoirs 108 are provided. Each buffer source reservoir 106 is arranged in fluid communication with a respective main channel 5, and can hold a buffer liquid which is to be fed into the main channel 5. Each sample source reservoir 105 is arranged in fluid communication with a respective pair of inlet subsidiary channels 6a,6b, and can hold a sample liquid which is to be fed into the inlet subsidiary channels 6a,6b. Each buffer drain reservoir 107 is arranged in fluid communication with a respective main channel 5, and can receive a buffer liquid which has flown along said main channel 5. Each sample drain reservoir 108 is arranged in fluid communication with a respective pair of outlet subsidiary channels 8a,8b and can receive a sample liquid which has flown out of the main channel 5 and along an outlet subsidiary channel 8a,8b.

(26) Briefly referring back to FIG. 1a, each main channel 5 is fluidly connected, via a first conduit 11, to a respective buffer source reservoir 106 (shown in FIG. 1b). The two inlet subsidiary channels 6a,6b for each main channel 5, are each fluidly connected, via a common second conduit 12, to a respective sample source reservoir 105 (shown in FIG. 1b); both inlet subsidiary channels 6a,6b being fluidly connected to the same sample source reservoir 105 via the common second conduit 12. In this example the first and second conduits 11,12 each pass through the pallet 3 from the first surface 4a to the second, opposite, surface 4b.

(27) Each main channel 5 is also fluidly connected, via a third conduit 13, to a respective buffer drain reservoir 107 (shown in FIG. 1b). The two outlet subsidiary channels 8a,8b for each main channel 5, are fluidly connected, via a common fourth conduit 14, to a respective sample drain reservoir 108 (shown in FIG. 1b); both outlet subsidiary channels 8a,8b being fluidly connected to the same sample drain reservoir 108 via the common fourth conduit 14. In this example the third and fourth conduits 13,14 each pass through the pallet 3 from the first surface 4a to the second, opposite, surface 4b.

(28) FIG. 1e which provides a plan view of one of the main channels 5 and its respective two inlet subsidiary channels 6a,6b and respective two outlet subsidiary channels 8a,8b; it will be understood that all of the main channels 5 and their respective two inlet subsidiary channels 6a,6b and respective two outlet subsidiary channels 8a,8b will have the same configuration as shown in FIG. 1d. Referring to FIG. 1e it can be seen that in this embodiment the respective lengths (L2,L3) of each of the two inlet subsidiary channels 6a,6b, from the second conduit 12 to the first junction 7, is equal to twice the length (L1) of the main channel 5 from the first conduit 11 to the first junction 7 (i.e. 2.L1=L2 and 2.L1=L3). Also the respective lengths (L2,L3) of each of the two inlet subsidiary channels 6a,6b, from the second conduit 12 to the first junction 7 are equal (i.e. L2=L3). The respective lengths (L5,L6) of each of the two outlet subsidiary channels 8a,8b, from the fourth conduit 14 to the second junction 9, is equal to twice the length (L4) of the main channel 5 from the third conduit 13 to the second junction 9 (i.e. 2.L4=L5 and 2.L4=L6), Also the respective lengths (L5,L6) of each of the two outlet subsidiary channels 8a,8b, from the fourth conduit 14 to the second junction 9 are equal (i.e. L5=16). In this example the lengths ‘L2’, ‘L3’, ‘L5’ and ‘L6’ are equal to each other; however this condition is not essential to the invention. Most preferably the lengths ‘L2’, ‘L3’, ‘L5’ and ‘L6’ will be between 20 and 60 mm, preferably 40 mm. In this example the lengths ‘L1’ and ‘L4’ equal to each other; however this condition is not essential to the invention. Most preferably the lengths ‘L1’ and ‘L4’ will be between 10 and 40 mm, preferably 20 mm. The length (L8) of the main channel 5 which extends between the first junction 7 and second junction 9 is also illustrated in FIG. 1e. Typically the length (L8) of the main channel 5 which extends between the first junction 7 and second junction 9 is between 1 mm-50 mm; in this example the length (L8) of the main channel 5 which extends between the first junction 7 and second junction 9 is 20 mm.

(29) The microfluidic device 1 shown in FIGS. 1a-e can be used to form an assembly according to a further aspect of the present invention. FIG. 2a provides perspective view of an assembly according to a further aspect of the present invention and FIG. 2b provides a cross-sectional view taken along line ‘A’ in FIG. 2a. Referring to FIGS. 2a and 2b, it can be seen that the assembly comprises a microfluidic device 1 (as shown in FIGS. 1a-e) and a means for generating a magnetic field in the form of permanent magnets 20a-c. It should be understood that the present invention is not limited to requiring means for generating a magnetic field in the form of permanent magnets, and that any suitable means for generating a magnetic field may be used (e.g. an electromagnet). Importantly the assembly is modular having a microfluidic device 1 which is mechanically independent of the means for generating a magnetic field (permanent magnets 20a-d); advantageously the means for generating a magnetic field is not integral to the microfluidic device 1 thus decreasing the manufacturing costs of the microfluidic device 1.

(30) Each of the permanent magnets 20a-d is received into a respective groove 15 which is defined in the second surface 4b of the pallet 3. The cross section of each permanent magnet 20a-d has a shape corresponding to the shape of the cross section of the groove 15; thus in this example each permanent magnet 20a-d have a tapered width and each permanent magnet 20a-d also has a flat top surface 21 corresponding to the flat surface 15c which defines a base of the groove 15. It will be understood that if the cross section of the grooves 15 had a curved apex (i.e. a base surface 15c which has a curved profile), then each permanent magnet 20a-d would have a cross section with a correspondingly curved apex (in this case preferably each permanent magnet 20a-d would have a cross section would have an apex which has a radius of curvature between 0.05 mm-0.5 mm; and most preferably each permanent magnet 20a-d would have a cross section would have an apex which has a radius of curvature of 0.2 mm). Likewise if the grooves has a v-shaped cross section then the permanent magnets 20a-c would also be shaped to have a corresponding v-shaped cross section. By having the cross sectional shape of each permanent magnet 20a-d corresponding to the cross sectional shape of the grooves 15, allows the permanent magnets 20a-d to snugly fit into their respective grooves 15. Preferably the permanent magnets 20a-d will snugly fit into their respective grooves 15 so that the apex or top of each of the permanent magnets 20a-d abuts the surface 15c defining base of the respective groove 5 into which it is received; this ensures that there is no air gap between the permanent magnets 20a-d and the surfaces 15c defining base of the respective grooves 15.

(31) Furthermore the length of each of the permanent magnets 20a-d corresponds to the length of the respective groove 15 into which it is received. Since in this example the length of the grooves 15 corresponds to the length of the main channels 5 between the first junction 7 and second junction 9, the length of each of the permanent magnets 20a-d will correspond to the length of the main channels 5 between the first junction 7 and second junction 9.

(32) During use the permanent magnets 20a-d can provide a magnetic field within a respective main channel 5. Since each of the permanent magnets 20a-d have a length corresponding to the length of the main channels 5 between the first junction 7 and second junction 9, each of the respective permanent magnets 20a-d can generate a magnetic field which is constant along the length of a respective main channel between the first junction 7 and second junction 9.

(33) The microfluidic device 1, as shown in FIGS. 1a-e, may be used to implement a method, according to a further aspect of the present invention. An embodiment of the method is a method for removing ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles from a sample, as will be described below: A microfluidic device 1, as shown in FIGS. 1a-e, is first provided.

(34) The sample which contains ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles is provided in a sample source reservoir 105. The sample flows from the sample source reservoir 105, via the second conduit 12, into the pair of inlet subsidiary channels 6a,6b. A buffer fluid, such as particle-free water is provided in a buffer source reservoir 106. The buffer fluid flows from the buffer source reservoir 106, via the first conduit 11, into the main channel 5. It will be understood that the buffer fluid may be any fluid which is absent of the particles which are to be removed from the sample (i.e. absent of the ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles which are to be removed); besides particle-free water other liquids such as phosphate buffer saline (PBS) solution or water containing a detergent may be used.

(35) The sample flows along the inlet subsidiary channels 6a,6b and enters the main channel 5 at the first junction 7. Accordingly at junction 7 the main channel 5 will contain both the sample and buffer fluid so that both the sample and buffer fluid simultaneously flow along the main channel 5.

(36) FIGS. 3a and 3b the arrangement a sample 30 and buffer fluid 31 in the main channel 5 as they flow along the main channel 5. The direction of flow of the sample 30 and buffer fluid 31 along the main channel 5 is indicated by the arrows. Upstream of the first junction 7 the main channel 5 contains only buffer fluid 31 which is coming from the buffer source reservoir 106. However, at junction 7, both of the inlet subsidiary channels 6a,6b join the main channel 5; at the first junction 7 the sample 30 which is flowing in the respective inlet subsidiary channels 6a,6b enters the main channel 5 so that both the sample 30 and buffer 31 simultaneously flow along the main channel 5.

(37) As can be seen in FIGS. 3a&b, two streams 30a,30b of sample are formed in the main channel 5; a first stream 30a of sample is formed by the sample 30 coming from one of the inlet subsidiary channels 6a, and a second stream 30b of sample is formed by the sample 30 coming from the other one of the inlet subsidiary channels 6b. Importantly, as the depth ‘d’ of each of the two inlet subsidiary channels 6a,6b is less than the depth ‘f’ of the main channel 5, the sample 30 and buffer fluid 31 form a particular arrangement within the main channel 5; specifically buffer fluid 31 is interposed between each of the sample streams 30a,30b and the planar channel bed 5d of the main channel 5.

(38) A magnetic field is applied to the sample 30 and buffer 31 which are simultaneously flowing along the main channel 5. The magnetic field moves the ferromagnetic, paramagnetic (or super-paramagnetic), and/or diamagnetic particles contained within the sample 30 in both of the sample streams 30a, 30b into the buffer 31. In this example in order to apply a magnetic field to the sample 30 (and buffer fluid 31) which is flowing along the main channel 5, a permanent magnet 20a-d is moved into the groove 15 on the second surface 4b of the pallet 3, which is aligned with said main channel 5 in which the sample 30 and buffer 31 flow. The permanent magnet 20a-c has a magnetisation which is in a direction which is perpendicular to the direction of flow of the sample 30 and buffer 31 in the main channel 5, and is also perpendicular to the planar channel bed 5d of the main channel (or perpendicular to a tangent to the apex of the cross section of the main channel if the main channel has a curved channel bed or if the main channel 5 has a v-shaped cross section). It will be understood that any means for generating a magnetic field may be used to provide the magnetic field which is applied to the sample 30 and buffer 31; the present invention is not limited to requiring the use of a permanent magnet 20a-d. It is pointed out that by providing a permanent magnet 20a-d in the groove the assembly shown in FIGS. 2a&b is formed.

(39) Advantageously, because buffer fluid 31 is interposed between each of the sample 30 and the channel bed 5d of the main channel 5, ferromagnetic, paramagnetic (or super-paramagnetic), and/or diamagnetic particles contained within the sample 30 can be moved from the sample 30 into the buffer fluid 31, in a direction which is perpendicular to, or substantially perpendicular to, the direction of flow of the sample streams 30a,30b and buffer fluid 31 in the main channel 5. More specifically ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles contained within the sample 30 can be moved from each of the sample streams 30a,30b, into the buffer fluid 31, in a direction which is towards the channel bed 5d of the main channel 5 (or in a direction which perpendicular to the channel bed 5d of the main channel 5; or perpendicular to a tangent to the apex of the cross section of the main channel if the main channel has a curved channel bed or if the main channel 5 has a v-shaped cross section).

(40) Furthermore, as is shown in FIGS. 3a&b, buffer fluid 31 is interposed between the sample streams 30a, 30b; thus ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles contained within the sample 30 can also be moved from each of the sample streams 30a,30b, into the buffer fluid 31, in a direction which is perpendicular to, or substantially perpendicular to, the direction of flow of the sample streams 30a,30b, and buffer fluid 31 in the main channel 5, More specifically ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles contained within the sample 30 can be moved from each of the sample streams 30a,30b, into the buffer fluid 31, in a direction which is parallel to the channel bed 5d of the main channel 5 (or in a direction which is parallel to a tangent to the apex of the cross section of the main channel if the main channel has a curved channel bed or a v-shaped cross section).

(41) By the time the sample 30 and buffer fluid 31 have reached the second junction 9, all of (or substantially all of) the ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles contained within the sample 30 will have been moved out of the sample 30 in both sample streams 30a,30b and into the buffer fluid 31 by the magnetic field.

(42) Due to the arrangement of the sample 30 and buffer fluid 31 within the main channel 5, and since the depth ‘g’ of the two outlet subsidiary channels 8a,8b correspond to the depth of the two inlet subsidiary channels 6a,6b the sample fluid 30, which is now absent of any ferromagnetic (or super paramagnetic), paramagnetic, and/or diamagnetic particles, will flow into the respective outlet subsidiary channels 8a,8b at the second junction 9. More specifically, the first stream 30a of sample fluid 30 is received into the outlet subsidiary channel 8a and the second stream 30b of sample fluid 30 is received into the other outlet subsidiary channel 8a. From the outlet subsidiary channels 8a,8b the sample will flow, via the fourth conduit 14, into the sample drain reservoir 108 where it is collected,

(43) At the second junction 9 the buffer fluid will however contain all the ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles which have been removed from the sample 30. Due to the arrangement of the sample 30 and buffer fluid 31 within the main channel 5, and since the depth ‘g’ of the two outlet subsidiary channels 8a,8b is less than the depth of the main channel 5, the buffer fluid containing the ferromagnetic, paramagnetic (or super paramagnetic), and/or diamagnetic particles will remain in the main channel 5 (will not flow into either of the outlet subsidiary channels 8a,8b) and will flow, via the third conduit 13, into the buffer drain reservoir 107.

(44) In the above example, in the main channel 5 the flow rate of the sample 30 flowing along the main channel 5 is equal to the flow rate of the buffer fluid 31 flowing along the main channel 5; the ratio between flow rate of sample 30 in the inlet subsidiary channels 6a,6b and buffer sample 31 in main channel 5 at the first junction 7 is 0.1-10 and is preferably 0.5-2; and the ratio between flow rates of sample in the outlet subsidiary channels 8a,8b and buffer in main channel at the second junction is 0.1-10 and is preferably 0.5-2.

(45) FIGS. 4a and 4b provide perspective views of an interface component 40 according to a further aspect of the present invention. FIG. 4a provides a perspective view of a top of the interface component 40 and FIG. 4b provides a perspective view of a bottom of the interface component 40. The interface component 40 is suitable for cooperating with the microfluidic device 1 shown in FIGS. 1a and b. When the interface component 40 is placed in cooperating with the microfluidic device 1 an assembly according to a further aspect of the present invention is formed.

(46) Referring to FIGS. 4a and 4b, the interface component 40 further comprises a plurality of magnetic assemblies 44. In this example the interface component 40 comprises four magnetic assemblies 44, however it will be understood that the interface component 40 may comprises any number of magnetic assemblies 44.

(47) The interface component 40 further comprises a plurality of elements 41, each of which can be selectively connected to a pneumatic system which can provide a fluid (such a pressurized air) to the elements 41. In this example the interface component 40 comprises sixteen elements 41, however it will be understood that the interface component 40 may comprise any number of elements 41; preferably the interface component 40 comprises at least four elements 41.

(48) Each element 41 comprises an input port 42 which can be selectively fluidly connected to a pneumatic system; a flow restrictor 43, which is fluidly connected to the input port 42, wherein the flow restrictor 43 is configured to restrict the flow of fluid through the element 41; and an aerosol filter 49 which is arranged to be in fluid communication with the adjustable flow restrictor 43. In this example the aerosol filter 49 is defined by a layer 49 of hydrophobic material; the layer 49 comprising pores having a size 0.22 μm (or at least in the range 0.1-0.3 μm).

(49) The interface component 40 further comprises a platform 46 which supports each of the magnetic assemblies 44 and elements 41. In this example the platform 46 is modular composed of two flat-gaskets 46a,46b and main member 46c; each of the two flat-gaskets 46a,46b are received into a respective cut-out 146 which is defined in the main member 46c.

(50) The interface component 40 further comprises a plurality of outlets 45a-p, each of the outlets 45a-p is in fluid communication with a respective element 41, so that fluid can flow from the element 41, out of the interface component, via the outlets 45a-p. In the example illustrated in FIGS. 4a and 4b, the outlets 45a-p are defined by apertures 45a-p which are defined in the platform 46. A layer 49 of hydrophobic material which defines the aerosol filter 49 of a respective element 41, overlays a respective apertures 45a-p which defines an outlet 45a-p.

(51) The number of outlets 45a-p should preferably correspond to the number of elements 41; accordingly in this example the interface component 40 comprises sixteen outlets 41. However it will be understood that the interface component 40 may be provided with any number of outlets 4a-p; preferably the interface component 40 comprises at least four outlets 45a-p. Each of the outlets 45a-p can be selectively arranged to be in fluid communication with a respective sample source reservoir 105, buffer source reservoir 106, buffer drain reservoir 107, or sample drain reservoir 108, of the microfluidic device 1.

(52) FIG. 5a provides a perspective, part cross-sectional, view of a flow restrictor 43 of an element 41. FIG. 5b provides an exploded view of the flow restrictor 43. It will be understood that each of the flows restrictors 43 in the interface component 40 will have a similar configuration to the flow restrictor 43 illustrated in FIGS. 5a and b.

(53) Referring to FIGS. 5a and 5b, the flow restrictor 43 comprises, an inlet member 707 which has an inlet channel 708 defined therein; and an outlet member 716 which has an outlet channel 717 defined therein. The inlet channel 708 and outlet channel 717 are fluidly connected. Each of the inlet and outlet channels 708, 717 each have a circular cross section. The inlet and outlet channels 708, 717 each have a diameter in the range 0.2 mm-1.5 mm.

(54) A capillary member 701, which comprises an intermediate channel 715, is interposed between the inlet channel 708 and outlet channel 717. The intermediate channel 715 has dimensions smaller than the dimensions of the inlet and outlet channels 708,717; specifically the diameter of the intermediate channel 715 is less than the diameters of each of inlet and outlet channels 708,717. Preferably the intermediate channel has a circular cross section that has a diameter which is between 1-100 μm. In this example the capillary member 701 is composed of glass; however it will be understood that capillary member 701 may be composed of any suitable material e.g. polymer.

(55) The flow restrictor 43 comprises a male member 703 and female member 704. The male member 703 comprises the inlet member 707, and the female member 704 comprises the outlet member 716.

(56) The male member 703 and female member 704 are configured so that they can mechanically cooperate with each other so that the male and female members can be fixed together. In this example the male member 703 has an external tread 721, and the female has a corresponding internal thread 722, which allow the members 703,704 to be fixed together. The male member 703 further comprises ribbing 711 defined an outer surface thereof, and the female member 704 further comprises ribbing 718 on an outer surface thereof; the ribbings 711,718 facilitate gripping of the members 703,704 as the members 703,704 are rotated with respect to one another so that their respective threads 721,722 can engage one another.

(57) When the male member 703 and female member 704 are mechanically cooperated, an end extremity 703a of the male member 703 will abut the female member 704 at an interface 725.

(58) At its end extremity 703a the male member 703 comprises an annular groove 726 defined by perpendicular surfaces 726a,726b. An o-ring 702 abuts both surfaces 726a,726b. The o-ring also abuts surface 704a which defines a base of the female member 704. The capillary member 701 passes through the o-ring 702; the diameter of the o-ring is substantially equal to the diameter of the capillary member 701 so that the o-ring also abuts an outer surface 701b of the capillary member 701. In the present embodiment the ratio of the cord thickness of the o-ring 702 to the inner diameter ‘r’ of the o-ring is 0.5 (or 0.8 for example); however the ratio of the cord thickness of the o-ring to the inner diameter may be any value between 0.5-1.

(59) In a variation of the embodiment the annular groove 726 may be defined in the female member and the o-ring 702 will be arranged to abut the surfaces which define the annular groove in the female member; for example the surface 704a the surface 704a which defines the base of the female member 704 may comprise an annular groove defined therein, and the o-ring 702 abuts surfaces which define the annular groove.

(60) The male member 703 has a pocket 719a defined therein; and the female member 704 has a pocket 719b defined therein. The pockets 719a,b can each receive a portion of the capillary member 701, so that a portion of length of the capillary member 701 is contained within the pocket 719a of the male member 703, and another a portion of length of the capillary member 701 is contained within pocket 719b of the female member 704.

(61) The depth of the pocket 719a in the male member 703 such that when the capillary member 701 is positioned into the pocket 719a, such that capillary member 701 abuts a base 719c of the pocket 19a, at least 0.5 mm of the length of the capillary member 701 extends out of the pocket 19a of the male member 703. In the example illustrated in FIG. 5, the capillary member 701 has a length of 2 mm; however it will be understood that the capillary member 701 may have any length greater than, or equal to, 0.5 mm. Since at least 0.5 mm of the length of the capillary member 701 should extend out of the pocket 19a of the male member 703, the pocket 719a defined in the male member 703 has a depth of 1.5 mm. However it will be understood that the pocket 719a defined in the male member 703 may have a depth between 1 mm-20 mm. The depth of the pocket 719b defined in female member 704 should be as large as possible so as to allow for the accommodation of capillary members 701 have different lengths; preferably the depth of the pocket 719b defined in female member 704 is between 1-20 mm; example illustrated in FIG. 5, the depth of the pocket 719b defined in female member 704 is 5 mm.

(62) In an further aspect of the present invention, an assembly comprising a interface component 40 and a plurality of capillary members 701 each of which comprises an intermediate channel 715, but the length ‘L’ of the capillary members 701 differ between each of the plurality of capillary members 701 so that the each have intermediate channels 715 of different lengths. In a preferred embodiment the diameter of the intermediate channels 715 of the plurality of capillary members 701 are equal. The plurality of capillary members 701 of different length 12 can be used to achieve different levels of restriction to the flow through an element 41 of the interface component 40. A user can select from the plurality of capillary members 701 a capillary member 701 which has a length which will provide the appropriate resistance to flow; for example in order to increase the restriction to flow through an element 41, the user can replace the capillary member 701 in said element 41 with a capillary member 701 which has a longer length ‘L’; likewise in order to decrease the restriction to flow through an element 41, the user can replace the capillary member 701 in said element 41 with a shorter capillary member 701. Importantly, the depth of the pocket 719a provided in the male member 703 plus the depth of the pocket 719b which is provided in the female member 704 must be equal to, or greater than, the length of the longest capillary member 701 in the plurality of capillary members 701.

(63) FIGS. 6a and 6b each provide a cross sectional view of a magnetic assembly 44. FIG. 6c provides a perspective view the magnetic assembly 44. It will be understood that each of the magnetic assembly 44 of the interface component 40 will have a similar configuration to the magnetic assembly 44 illustrated in FIGS. 6a-c.

(64) Referring to FIGS. 6a-c it is shown that the magnetic assembly 44, comprises, a plunger 60. The plunger 60 comprises a housing 633 which has a threaded portion 608 which is received into a through-hole 65 defined in the platform 46 so as to secure the magnetic assembly 44 to the platform 46 of the interface component 40. The surface of the through-hole 65 is also threaded and the threads provided on the threaded portion 608 cooperate with the threads provided on the surface of the through-hole 65.

(65) One end of the plunger 60 is connected to a means for generating a magnetic field 513. In this example means for generating a magnetic field 513 is a permanent magnet 513. It will be understood that any suitable means for generating a magnetic field may be provided.

(66) The plunger 60 comprises a shaft 61 which has a cap member 606 at a first end 61a thereof, and a support member 512 (only one pin shown in FIGS. 6a, 6b) at a second, opposite, end 61b thereof. In this example the shaft 61 is treaded at the second end 61b and the second end 61b is received into a corresponding treaded hole which is defined in the support member 512. The threaded portion 608 of the housing 633 is tubular shaped and the shaft 61 extends through the volume defined within the tubular shaped threaded portion 608. The permanent magnet 513 is mechanically supported on the support member 512. The support member 512 further comprises two parallel guide pins 514. The two parallel guide pins 514 extend through respective guide-through-holes which are defined in the platform 46. The two parallel pins 514 help to prevent the permanent magnet 513 from rotating around the longitudinal axis of the shaft 61.

(67) The plunger 60 further comprises an electromagnet 603 which is housed within a housing 603. The plunger 60 comprises a biasing means in the form of a spring 605 which biases the shaft 61 towards a first position; the spring 605 is interposed between the cap member 606 on the shaft 61 and housing 603. The electromagnet 603 cooperates with the shaft 61 such that operating the electromagnet 603 forces the shaft 61 to move, against the biasing force of the spring 605, towards a second position. FIG. 6a shows the shaft 61 having been moved by the biasing force of the spring 605, to its first position. FIG. 6b shows the shaft 61 having been moved by the electromagnet 603, against the biasing force of the spring 605, to its second position. When the shaft 61 is moved towards its first position the permanent magnet 513 is moved in a direction which is towards the platform 46; when the shaft 61 is moved towards its second position the permanent magnet 513 is moved in a direction which is away from the platform 46.

(68) FIGS. 6a and 613 also illustrate a cross section of a microfluidic device 1; showing a cross section of the groove 15 and a cross section of the main channel 5. As shown in FIG. 6a, the electromagnet 603 is deactivated so that the shaft 61 is moved towards its first position and the permanent magnet 513 is moved in a direction which is towards the platform 46. When the shaft 61 is in its first position the interface component 40 is positioned so that the permanent magnet 513 of the magnetic assembly 44 is aligned over the groove 15 which is defined in the second surface 4b of the microfluidic device 1. The electromagnet 603 is then operated so that it move the shaft 61 against the biasing force of the spring 605, to its second position and the permanent magnet 513 is moved in a direction away from the platform 46. When the shaft 61 is in its second position the permanent magnet 513 is received into the groove 15 of the microfluidic device 1. Once received into the groove 15 the permanent magnet 513 can provide a magnetization in the region of the main channel 5 which will move ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles from a sample into a buffer fluid which are simultaneously flowing along the main channel 5.

(69) The permanent magnet 513 has a shape which corresponds to the shape of the groove 15 in the microfluidic device 1. Specifically permanent magnet 513 has a cross sectional shape which corresponds to the cross sectional shape of the groove 15 in the microfluidic device 1. In the example shown in FIGS. 6a and 6b the groove 15 is v-shaped, accordingly the permanent magnet 513 has a triangular-shaped cross-section having dimension which allow at least the peak of the triangular-shaped cross-sectioned permanent magnet 513 to be received into the groove 15. The permanent magnet 513 also extends over the whole length of the groove 15; and the v-shaped cross sectional profile is constant along the whole length of permanent magnet 513.

(70) It will be understood that the permanent magnet 513 may have any suitable shape. Preferably the shape of permanent magnet 513 will correspond to the shape of the groove 15 defined in the microfluidic device 1 which is to be used with the interface component, so that the permanent magnet 513 can fit snugly into the groove 15 of the microfluidic device 1. In the above-mentioned example permanent magnet 513 had a triangular cross section, thus making it ideally suitable for use with microfluidic devices that have groove 15 which have a v-shaped cross section. It will be understood that the permanent magnet 513 may be configured to have a cross section which has a curved tip (instead of pointed tip in the case of a triangular cross section); interface components with permanent magnet 513 that have curved tip are ideally suited for use with microfluidic devices 1 that have grooves 15 that have a curved cross section; preferably the radius of curvature of the curved tip of the permanent magnet 513 is equal to the radius of curvature of the curved groove 15 in the microfluidic device 1. In an exemplary embodiment the permanent magnet 513 may have a curved tip which has a radius of curvature between 0.05 mm-0.5 mm; and most preferably has a radius of curvature of between 0.2 mm. In another embodiment the permanent magnet 513 may be configured to have cross section which has a flat tip; interface components with permanent magnet 513 that have flat tip are ideally suited for use with microfluidic devices 1 that have grooves 15 with a planar base.

(71) FIG. 7 provides a perspective view of an assembly 70 according to a further aspect of the present invention. The assembly 70 comprises a microfluidic device 1 shown FIGS. 1a and b, and interface component 40 shown in FIGS. 4a and 4b. Importantly the assembly 70 is modular having a microfluidic device 1 which is mechanically independent of the interface component 40 (which comprises the permanent magnets 513); advantageously the interface component 40 can be selectively arranged to mechanically cooperate with the microfluidic device 1; however the permanent magnets 513 are not integral to the microfluidic device 1 thus decreasing the manufacturing costs of the microfluidic device 1.

(72) In the assembly 7 shown in FIG. 7, the interface component 40 is arranged to mechanically cooperate with the microfluidic device 1 so that each of the outlets 45a-p of the interface component 40 is in fluid communication with a respective sample source reservoir 105, buffer source reservoir 106, buffer drain reservoir 107, or sample drain reservoir 108, of the microfluidic device 1. In this example shown in FIG. 7 outlets a-d will overlay a respective sample source reservoir 105 of the microfluidic device 1 so that the outlets 45a-d are in fluid communication with a respective sample source reservoir 105; outlets 45e-h will overlay a respective buffer source reservoir 106 of the microfluidic device 1 so that the outlets 45e-h are in fluid communication with a respective buffer source reservoir 106; outlets 45i-L will overlay a respective buffer drain reservoir 107 of the microfluidic device 1 so that the outlets 45i-l are in fluid communication with a respective buffer drain reservoir 107; outlets 45m-p will overlay a respective sample drain reservoir 108 of the microfluidic device 1 so that the outlets are in fluid communication with a respective sample drain reservoir 108. The dimensions of the cross section of each of the outlets 45a-p correspond to the cross sectional dimensions of the respective buffer source reservoirs 106, sample source reservoir 105, buffer drain reservoirs 107 and sample drain reservoirs 108, such that an impermeable seal is formed between the respective reservoir and outlet 45a-p when in mechanical cooperation. It is also noted that the relative positions of the outlets 45a-p correspond to the relative positions of the reservoirs.

(73) The interface component 40 comprises a row of four magnetic assemblies 44 each identical to the magnetic assembly illustrated in FIGS. 6a, 6b. The elements 41a-h which are located on a first side 55a of the row of four magnetic assemblies 44 are all fluidly connected to a pneumatic system 71a which provides positive air flow (indicated by the arrow 50). The positive air flow which is provided to the elements 41a-d passes through the respective elements 41a-d and into the respective sample source reservoirs 105 via the respective outlets 45a-d. The positive air flow pushes sample which is in the respective sample source reservoirs 105 to flow, via respective second conduits 12, into respective pairs of inlet subsidiary channels 6a,6b; along the respective pairs of inlet subsidiary channels 6a,6b; and subsequently pushes the sample to flow into respective main channels 5 of the microfluidic device 1.

(74) The elements 41e-h which are also located on the first side 55a of the row of four magnetic assemblies 44 are all also fluidly connected to a pneumatic system 71a which provides positive air flow (indicated by the arrow 50). The positive air flow which is provided to the elements e-h passes through the respective elements 41e-h and into the respective buffer source reservoirs 106 via the respective outlets 45e-h; the positive air flow pushes buffer fluid which is in the respective buffer source reservoirs 106 to flow, via respective first conduits 11, into respective main channels 5 of the microfluidic device 1.

(75) The elements 41i-l which are located on a second, opposite, side 55b of the row of four magnetic assemblies 44 are all fluidly connected to a pneumatic system 71b which provides negative air flow (indicated by the arrow 51). The negative air flow which is provided to the elements 41i-l passes through the respective elements 41i-l and into the respective sample source reservoirs 105 via the respective outlets 45i-l; the positive air flow sucks the buffer fluid, which contains ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles which were removed from the sample, from the main channel 5 into respective buffer drain reservoirs 107, via the third conduit 13.

(76) The elements 41m-p which are also located on the second, opposite, side 55b of the row of four magnetic assemblies 44, are also all fluidly connected to a pneumatic system 71b which provides negative air flow (indicated by the arrow 51). The negative air flow which is provided to the elements 41m-p passes through the respective elements 41m-p and into the respective sample drain reservoirs 108 via the respective outlets 45m-p; the positive air flow sucks the sample fluid, which is absent of ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles, from the main channel 5 into respective pairs of outlet subsidiary channels 8a,8b; along the respective pairs of outlet subsidiary channels 8a,8b; and subsequently into respective sample drain reservoirs 108, via the fourth conduit 14.

(77) The assembly 70 can be used to perform a method according to a further embodiment of the present invention. The assembly 70 is provided. A sample containing ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles, is provided in at least one of the sample source reservoirs 105; in this example the sample is provided in all of the sample source reservoirs 105 in the microfluidic device (in this example microfluidic device 1 comprises four sample source reservoirs 105). A buffer fluid is provided in at least one of the buffer source reservoirs 106; in this example sample is provided in all of the buffer source reservoirs 106 in the microfluidic device (in this example microfluidic device 1 comprises four buffer source reservoirs 106). In this example there are also a corresponding number of buffer drain reservoirs 107 and source drain reservoirs 108 i.e. four buffer drain reservoirs 107, and four source drain reservoirs 108.

(78) Once the respective sample source reservoirs 105 and buffer source reservoirs 106 have been filled, the interface component 40 is then arranged to mechanically cooperate with the microfluidic device 1. Specifically the interface component 40 is arranged so that: the outlets 45a-d overlay a respective sample source reservoir 105 of the microfluidic device 1 so that the outlets 45a-d are in fluid communication with a respective sample source reservoir 105; the outlets 45e-h overlay a respective buffer source reservoir 106 of the microfluidic device 1 so that the outlets 45e-h are in fluid communication with a respective buffer source reservoir 106; the outlets 45i-l overlay a respective buffer drain reservoir 107 of the microfluidic device 1 so that the outlets 45i-l are in fluid communication with a respective buffer drain reservoir 107; the outlets 45m-p overlay a respective sample drain reservoir 108 of the microfluidic device 1 so that the outlets 45i-L are in fluid communication with a respective sample drain reservoir 108.

(79) By arranging the interface component 40 to mechanically cooperate with the microfluidic device 1 in the manner mentioned above, the permanent magnet 513 of each magnetic assembly 44 is aligned over a respective groove 15 of the microfluidic device 1. At this stage the electromagnets 603 of each magnetic assembly 44 may be deactivated so that the shaft 61 occupies its first position thus ensuring that the permanent magnet 513 is at a position which is remote from the microfluidic device 1. However once the interface component 40 has been arranged to mechanically cooperate with the microfluidic device 1 the electromagnet 603 of each magnetic assembly 44 is then operated; the electromagnets force each shaft 61 to move, against the biasing force of the spring 605, to its second position, so that the permanent magnet 513 of each magnetic assembly is moved into a respective groove 15 in the microfluidic device 1. Once received into the groove 15 the permanent magnets 513 is configured to provide a magnetization in the region of a respective main channel 5; the direction of magnetization is perpendicular to the planar channel bed 5d of the main channel, and it also perpendicular to the flow of sample and buffer fluid along the main channel 5. Importantly, if the channel bed of the main channel is curved, then the permanent magnets 513 is configured to provide a magnetization in a direction which is perpendicular to a tangent to the apex of the curve of the channel; likewise or if the cross section of the main channel is v-shaped then the permanent magnets 513 is configured to provide a magnetization in a direction which is perpendicular to a tangent to the apex of the channel. Most preferably the means for generating a magnetic field 513, which in this example is the permanent magnet 513, has a cross section which is tapered in a direction towards the main channel 5. Preferably, the means for generating a magnetic field 513, which in this example is the permanent magnet 513, will be configured to provide a magnetization in a direction which is perpendicular to a longitudinal axis of the permanent magnet 513. Most preferably, the means for generating a magnetic field 513, which in this example is the permanent magnet 513, will be configured to provide a magnetization in a direction which is perpendicular to a longitudinal axis of the permanent magnet 513 and which is perpendicular to the plane of the pallet 3 of the microfluidic device.

(80) The pneumatic systems 71a, 71b are then operated to provide respective a positive air flow and negative air flow. The pneumatic system 71a provides a positive air flow 50 to the elements 41a-h which are located on the first side 55a of the row of magnetic assemblies 44, and the pneumatic system 71b provides a negative air flow 51 to the elements 41i-p which are located on a second, opposite, side 55b of the row of four magnetic assemblies 44. When operated the pneumatic systems 71a, 71b cause the sample to flow out of respective sample source reservoirs 105 via the second conduit 12; along respective pairs of subsidiary inlet channels 6a,6b; along the respective main channels 5 (simultaneously with the buffer fluid) where ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles are removed from the sample; and subsequently along respective pairs of outlet subsidiary channels 8a,8b; and from there into respective sample drain reservoirs 108 via respective fourth conduits 14. When operated the pneumatic systems 71a, 71b cause the buffer fluid to flow out of respective buffer source reservoirs 106 via the first conduit 11; along the main channel 5 (simultaneously with the buffer fluid) where the buffer fluid will receive ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles which have been removed from the sample; and subsequently into respective buffer drain reservoirs 107 via respective third conduits 13.

(81) The sample flowing into the respective main channels from the respective pairs of inlet subsidiary channels 6a,6b will form two streams 30a,30b of sample flowing in each respective main channel 5. Importantly as the depth ‘d’ of each of the pairs of inlet subsidiary channels 6a,6b is less than the depth ‘f’ of the respective main channels 5, along the main channel 5 between respective first and second junctions 7,9, buffer fluid 31 is interposed between each of the sample streams 30a,30b and the channel bed 5d of the main channel; also buffer fluid will be interposed between the two sample streams 30a,30b.

(82) As the sample and buffer fluid simultaneously flow along the respective main channels 5, the magnetization provided in the region of the main channels 5 by the respective permanent magnetics 513 move the ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles, which are contained in the sample, in a direction which is perpendicular to the flow of the sample and buffer fluid in the main channel and is also perpendicular to the channel bed 5d of the main channel, out of the sample and into a buffer fluid. In other words the ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles, which are contained in the sample, are moved into the buffer fluid which is located between the sample and channel bed 5d of the main channel 5.

(83) The ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles may also be moved in a direction which is perpendicular to the flow of the sample and buffer fluid in the main channel and is parallel to the channel bed 5d of the main channel. In other words the ferromagnetic, paramagnetic (including super-paramagnetic), and/or diamagnetic particles, which are contained in the sample, may also moved into the buffer fluid which is interposed between the two sample streams 30a,30b flowing in the main channel 5.

(84) Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiment.