DEVICE AND METHOD FOR CIRCULATING LIQUIDS

Abstract

Disclosed is a device including at least one circulating zone and at least one fluid including at least one more-paramagnetic liquid and at least one less-paramagnetic liquid forming a liquid-liquid interphase, the device including at least one element generating, in the circulating zone, a magnetic field, wherein the less-paramagnetic liquid is surrounded by the more-paramagnetic liquid in the circulating zone or wherein the more-paramagnetic liquid is surrounded by the less-paramagnetic liquid in the circulating zone. Also disclosed is a method including circulating at least one less-paramagnetic liquid inside one or more circulating zones of a device including at least one circulating zone and at least one more-paramagnetic liquid in the circulating zone.

Claims

1-16. (canceled)

17. A device comprising at least one circulating zone and at least one fluid comprising at least one more-paramagnetic liquid and at least one less-paramagnetic liquid forming a liquid-liquid interphase, said device comprising at least one element generating, in said circulating zone, a magnetic field, wherein said less-paramagnetic liquid is surrounded by said more-paramagnetic liquid in the circulating zone and wherein said less-paramagnetic liquid circulates in said circulating zone without contact with a solid wall.

18. The device according to claim 17, wherein said less-paramagnetic liquid circulates though said more-paramagnetic liquid in said circulating zone.

19. The device according to claim 17, wherein said magnetic field is theoretically null along the centre of the cross-section of the circulating zone.

20. The device according to claim 17, wherein said element generating a magnetic field is selected from the group consisting of permanent or electropermanent magnets, electromagnets, magnetised soft magnets, and any combination thereof, where additionally, the field strength and/or orientation can be time dependent, for example by means of mechanical actuation and/or rotation of permanent magnets or by increasing and/or decreasing the current in an electromagnet.

21. The device according to claim 17, wherein said device comprises a multipolar configuration of N magnets with N equal or greater than 2 or equal or greater than 3, N representing the number of magnets.

22. The device according to claim 17, wherein said elements generating a magnetic field comprises a quadrupole.

23. The device according to claim 17, wherein said device is a microfluidic device, a magnetically actuated fluid valve, a magnetically actuated peristaltic pump, an anti-fouling device, an anti-clogging device, a propulsion device, a heat exchanger, an extractor, a desalinator, or a mixing device.

24. The device according to claim 17, wherein said device comprises a movable pinching point in said circulating zone, said movable pinching point moving in the liquid flow direction to circulate said fluid in said circulating zone.

25. The device according to claim 17, wherein said device comprises an undulated liquid-liquid interface (due to normal-field instabilities), where said undulations can move in the liquid flow direction to circulate said fluid in said circulating zone.

26. The device according to claim 17, wherein said less-paramagnetic liquid is a diamagnetic liquid.

27. The device according to claim 17, wherein said less-paramagnetic liquid is a biological fluid or a fluid including a suspension of biological cells in a liquid medium.

28. The device according to claim 17, wherein said device comprises an organic paramagnetic liquid.

29. A method comprising circulating at least one less-paramagnetic liquid inside one or more circulating zones of a device comprising at least one circulating zone and at least one more-paramagnetic liquid in said circulating zone, said device comprising at least one element generating, in said circulating zone, a magnetic field, wherein said less-paramagnetic liquid is introduced in a circulating zone, said less-paramagnetic liquid circulating in said circulating zone comprising at least one more-paramagnetic liquid, thereby forming a liquid-liquid interphase with said more-paramagnetic liquid, wherein said less-paramagnetic liquid is surrounded by said more-paramagnetic liquid in the circulating zone.

30. The method according to claim 29, wherein the device comprises at least one circulating zone and at least one fluid comprising at least one more-paramagnetic liquid and at least one less-paramagnetic liquid forming a liquid-liquid interphase, said device comprising at least one element generating, in said circulating zone, a magnetic field, wherein said less-paramagnetic liquid is surrounded by said more-paramagnetic liquid in the circulating zone and wherein said less-paramagnetic liquid circulates in said circulating zone without contact with a solid wall.

31. A method comprising circulating at least one less-paramagnetic liquid inside one or more more-paramagnetic liquids, wherein method comprising generating a magnetic field providing a liquid-liquid interface configuration wherein said less-paramagnetic liquid is surrounded by said more-paramagnetic liquid.

32. The method according to claim 29, wherein said element generating, in said circulating zone, a magnetic field generates a variation in the magnetic field thereby circulating the less-paramagnetic liquid in the circulating zone.

33. The method according to claim 31, wherein said element generating, in said circulating zone, a magnetic field generates a variation in the magnetic field thereby circulating the less-paramagnetic liquid in the circulating zone.

Description

[0125] In the figures:

[0126] FIG. 1 represents Geometries, simulations, and experimental verification of liquid tubes and anti-tubes according to example 1.

[0127] FIGS. 2 and 3 represent water in oily ferrofluid anti-tubes in a device with a quadrupole magnet. FIG. 2 is a plot of anti-tube diameter vs. applied pressure, and the resulting flow.

[0128] FIG. 3 represents is a plot similar to a), but using a closed outlet, leading to transient flow upon pressure increase.

[0129] FIG. 4 represents a simulated magnetic field distribution for a quadrupolar array with gap of 12 mm. The lowest field is created in the centre of the gap between two magnets and is represented on the left; on the right is a cross-sectional view of aqueous anti-tube (white dot in the centre) confined in a commercial ferrofluid (black colour) in a 3D printed plastic holder with permanent magnets.

[0130] FIG. 5 represents a 3D printed wheel 1 with ten magnets 10 placed around the outer surface 20 of the wheel 1, thereby forming a magnetically actuated peristaltic pump when in combination with elements generating a magnetic field in a circulating zone, according to the invention, for example forming a quadrupole.

[0131] FIG. 6 represents residual blood as a function of elution volume of TMB (3,3′,5,5′-Tetramethylbenzidine) rinsing in anti-tube (squares), medical grade Tygon tube (circles), and regular Tygon tube (triangles).

[0132] FIG. 7 represents a schematic example of permanent magnets magnetising a soft magnetic foil with two notches. The two notches generate a confinement field as shown in FIG. 8.

[0133] FIG. 8 represents a cross-sectional magnetic field distribution |B| for a horizontally magnetised foil with different notch cuts, from 0-0.3 Tesla (T).

[0134] FIG. 9 represents a schematic example of two permanent magnets with the same shape as the notches in FIG. 7, but magnetised in the opposite sense.

[0135] FIG. 10 represents |B| for a bilayer consisting of two permanent magnets vertically magnetised in opposition directions, from 0-0.5 Tesla (T).

[0136] FIG. 11 represents |B| for a bilayer consisting of two permanent magnets horizontally magnetised in opposition directions, from 0-0.5 Tesla (T).

[0137] FIG. 12 represents |B| in (T) for a bilayer consisting of a horizontally magnetised permanent magnet (bottom) and soft iron foil (top) with a single cut through the bilayer, from 0-0.5 Tesla (T).

[0138] FIG. 13 represents |B| for two permanent magnets vertically magnetised in parallel, from 0-0.5 Tesla (T).

[0139] FIG. 14 represents |B| for two permanent magnets vertically magnetised in opposite directions, from 0-0.5 Tesla (T).

[0140] FIG. 15 represents |B| for two permanent magnets horizontally magnetised in parallel, from 0-0.5 Tesla (T).

[0141] FIG. 16 represents |B| for two permanent magnets horizontally magnetised in opposite directions, from 0-0.5 Tesla (T).

[0142] FIG. 17 represents a crossectional magnetic field magnitude distribution |B| for four multipolar geometries, N=3, 4, 6, 8; (δ=1, t=0), from 0-0.5 Tesla (T).

[0143] FIG. 18 represents a crossectional magnetic field magnitude distribution |B| for four multipolar geometries, N=3, 4, 6, 8; (δ=0,t=0), from 0-0.5 Tesla (T).

[0144] FIG. 19 represents a crossectional magnetic field magnitude distribution |B| for four multipolar geometries, N=3, 4, 6, 8; (δ=1,t=1), from 0-0.5 Tesla (T).

[0145] FIG. 20 represents a crossectional magnetic field magnitude distribution |B| for four multipolar geometries, N=3, 4, 6, 8; (δ=1,t=1), from 0-0.5 Tesla (T).

[0146] FIG. 21 represents a crossectional magnetic field magnitude distribution |B| for four multipolar geometries, N=3, 4, 6, 8; (δ=1,t=−1), from 0-0.5 Tesla (T).

[0147] The permanent magnets may be made from NdFeB, SmCo, alnico or hexagonal ferrite, the said material in sintered or bonded form.

[0148] FIG. 22 represents a graph of water antitube diameter d versus gap width w. The graph is a simulation. Points are experimental data on the curve “APG311” (Ferrotec). The curve “QK100+surfactant” is obtained with a very strong ferrofluid (QK100 with M.sub.s of 100 kA m.sup.−1, Qfluidics) and where the surface tension 6 is lowered to 1 mN m.sup.−1 using surfactants (e.g., Tween-20 and Span-80). The inset shows an enlarged area for APG311 data points and error bars from at least three independent experiments.

[0149] FIG. 23 represents a graph showing the Null Point of a Quadrupolar Magnet (Magnets used: 9×9×50 mm bars, gap of 9 mm). The measure is performed along the central axis the direction of the magnetic field switches, meaning there is a true null or zero point as shown in FIG. 23. In FIG. 23: Vertical Field Profile. x component of the magnetic field measured along z. Inset shows the measurement axis.

EXAMPLES

Example 1—Aqueous/Aqueous Liquid Anti-Tubes

[0150] A range of different magnet arrangements have been used to stabilize paramagnetic liquid anti-tubes (i.e., a tube of a diamagnetic liquid within a paramagnetic fluid). The paramagnetic liquid in this section is made by dissolving holmium chloride (HoCl.sub.3) in water, whereas the diamagnetic (less paramagnetic) liquid is pure water. In all cases small commercially available NdFeB magnets were used to fabricate the magnet arrangements and the tube was visualized by confocal microscopy (using Rhodamine B as a dye). For each of four magnet arrangements MA1-4 the following three types of information are shown in FIG. 1.

[0151] In FIG. 1:

[0152] a) Schematic of liquid tube and anti-tube confinement for four magnet arrangements, the first two stabilize tubes of paramagnetic HoCl.sub.3 in water, the last two stabilize anti-tubes of water or LaCl.sub.3 in HoCl.sub.3; b) analytically evaluated contour plots of |B| for the geometries; c) confocal cross-section fluorescence images of rhodamine in tubes (columns 1,2), and anti-tubes (columns 3,4).

[0153] The first magnet arrangement MA-1 is a rectangular magnet magnetized vertically. When the paramagnetic liquid is flowed close to the magnet, a tube forms with a bimodal height profile across its cross-section. In order to avoid the bimodal shape, a flux-concentrator (fabricated from a soft ferromagnetic material) was used (MA-2). Of particular interest for applications in microfluidics is the anti-tube, where no magnetic species need be present in the main channel. The easiest implementation is MA-3, where a narrow notch is cut or etched in a NdFeB permanent magnet. The notch effectively creates a magnetic void in the surface magnetic field (FIG. 1b, MA-3), which leads to an anti-tube at the b substrate (FIG. 1c, MA-3). However, the anti-tube stabilization is weak in the vertical direction, leading to a plume of ascending (diamagnetic) water, aided by the density difference (specific gravity of HoCl.sub.3,aq is 1.3). The inventors discovered the arrangement providing full magnetic anti-tube confinement in all three dimensions (MA-4) which is a quadrupole arrangement. In addition, there is no physical wall contact at any point, in contrast to the other three magnet arrangements.

[0154] This example supports the manufacturing of a device according to the present invention comprising at least one circulating zone and at least one fluid comprising at least one more-paramagnetic liquid and at least one less-paramagnetic liquid forming a liquid-liquid interphase, said device comprising at least one element generating, in said circulating zone, a magnetic field, wherein said less-paramagnetic liquid is surrounded by said more-paramagnetic liquid in the circulating zone. The reverse arrangement wherein said more-paramagnetic liquid is surrounded by said less-paramagnetic liquid in the circulating zone is also supported by these experiments.

Example 2—Aqueous/Oily Anti-Tubes

[0155] The inventors noted that anti-tubes described in example 1 have only a limited life-time when the paramagnetic liquid is an aqueous solution of paramagnetic ions and the less-paramagnetic liquid is pure diamagnetic water, due to diffusion of Ho.sup.3+ ions across the paramagnetic/diamagnetic boundary. The ion diffusion reduces the difference in magnetic susceptibility between the two initially well-defined regions, which in turn lowers the magnetic pressure and bulk forces. However, when implementing two liquids that are immiscible by replacing the aqueous paramagnetic liquid by an (APG 300, Ferrotec) oil-based ferrofluid, any transport across the boundary was prevented, and thus leads to anti-tubes that are stable for months. The anti-tube diameter can be measured from the side-view of the device using a stereoscope in transmission mode. To characterize the behaviour of the anti-tube a series of pressure experiments was performed. Firstly, a defined pressure was applied to the inlet of the anti-tube by flowing pure water using a pressure-driven pump. The pressure induces flow through the anti-tube towards the outlet, which was measured using a mass-flow sensor. FIG. 2 shows a typical experiment, in which it is clear that an increase in pressure leads to an increase in flow, as well as a slight dilation of the anti-tube diameter. When the outlet of the anti-tube is closed off completely, there is only a transient flow into the anti-tube. The increased pressure dilates the anti-tube and accommodates more water. When the pressure is reduced again, there is a negative (reverse) flow to excrete the excess water (FIG. 3).

Example 3—Designs of Elements Generating a Magnetic Field

[0156] 3.1. Quadrupole

[0157] The inventors have designed magnetic arrays to form an anti-tube by magnetic field simulations (using either finite element methods or analytical expressions using SciPy) and prototyping (using a 3D printer). With a quadrupole magnet arrangement it is possible to achieve stable anti-tubes of virtually any diamagnetic liquid that is immiscible with the paramagnetic medium as shown in FIG. 4.

[0158] A commercial ferrofluid (black colour) was used as paramagnetic liquid and water as diamagnetic liquid. Water that was flowed through the ferrofluid remained clear and transparent further supporting the stability of the anti-tube. Water flows freely through the black oily ferrofluid without being contaminated by the paramagnetic liquid. In other words, the combination of the quadrupole magnets and the ferrofluid results in a channel with liquid walls.

[0159] 3.2. Single Sided Designs

[0160] Single sided designs are suitable when buoyancy/density differences between the more diamagnetic and paramagnetic liquids are not significant as they have weaker vertical confinement.

[0161] 3.2.1 Horizontally Magnetised Soft Magnets

[0162] In this configuration, soft magnetic foils are magnetised horizontally using external magnetic sources, e.g. permanent magnets in intimate contact (FIG. 7), or larger external fields. The magnetic field stays within the soft foil except where there are cuts or notches. Pairs of notches cut into a foil allow the magnetic field to escape, and lead to the formation of a stable region that contains a liquid tube (FIG. 8).

[0163] 3.2.2 Horizontally Magnetised Multi-Track Hard Magnets

The same magnetic field structure as that described above can be generated using magnet sources with the same shape as the notches, but magnetised in the opposite direction (FIG. 9).

[0164] 3.3. Bilayer Designs

[0165] 3.3.1 Vertically Magnetised Permanent Magnets

[0166] An example of Vertically Magnetised Permanent Magnets is represented on FIG. 10

[0167] 3.2.2 Horizontally Magnetised Permanent Magnets

[0168] An example of Vertically Magnetised Permanent Magnets is represented on FIG. 11.

[0169] 3.2.3. Horizontally Magnetised Permanent and Soft Magnets

[0170] An example of Vertically Magnetised Permanent Magnets is represented on FIG. 12.

[0171] 3.4. Dipolar Configurations

[0172] 3.4.1 Vertically Magnetised Permanent Magnets

[0173] An example of Vertically Magnetised Permanent Magnets is represented on FIG. 13.

[0174] An second example of Vertically Magnetised Permanent Magnets is represented on FIG. 14.

[0175] 3.4.2. Horizontally Magnetised Permanent Magnets

[0176] An example of Horizontally Magnetised Permanent Magnets is represented on FIG. 15.

[0177] An example of Horizontally Magnetised Permanent Magnets is represented on FIG. 16.

[0178] 3.5. Symmetric Multipolar Configurations

[0179] Multipolar configurations, with N magnets can include, but are not limited to variations of magnetisations where the k.sup.th magnet in polar coordinates has a magnetisation:

M.sub.θ=M cos(2πk/N+(δ+tk)2π/s)i.sup.2k|t|  (1)

M.sub.r=M sin(2πk/N+(δ+tk)π/s)i.sup.2k|t|  (2)

where i=√−1. Simple examples given below are for s=4, i.e. where the magnetisation of a magnet can be one of four orientations, radial positive (“outwards”), radial negative (“inwards”), transverse positive (“right”), and transverse negative (“left”). Scales in the following sections are from 0-0.5 T.

[0180] 3.5.1 Pointing radially outwards (δ=1, t=0)

M.sub.θ=M cos(2kπ/N+π/2)  (3)

M.sub.r=M sin(2kπ/N+π/2)  (4)

[0181] An example of a Multipolar Configuration of Permanent Magnets is represented on FIG. 17.

[0182] 3.5.2. Alternating transverse (right, left) (δ=0, t=0)

M.sub.θ=M cos(2kπ/N)  (5)

M.sub.r=M sin(2kπ/N)  (6)

[0183] An example of a Multipolar Configuration of Permanent Magnets is represented on FIG. 18.

[0184] 3.5.3. Alternating radially outwards, inwards (δ=1, t=1)

M.sub.θ=M cos(2kπ/N+π/2)i.sup.2k  (7)

M.sub.r=M sin(2kπ/N+π/2)i.sup.2k  (8)

[0185] An example of a Multipolar Configuration of Permanent Magnets is represented on FIG. 19.

[0186] 3.5.4. Alternating radially out, transverse left, radially in, transverse right (δ=1, t=1)

M.sub.θ=M cos(2kπ/N+(1+k)π/2)i.sup.2k  (9)

M.sub.r=M sin(2kπ/N+(1+k)π/2)i.sup.2k  (10)

[0187] An example of a Multipolar Configuration of Permanent Magnets is represented on FIG. 20.

[0188] 3.5.5. Alternating radially out, transverse right, radially in, transverse left (δ=1, t=−1)

M.sub.θ=M cos(2kπ/N+(1−k)π/2)i.sup.2k  (11)

M.sub.r=M sin(2kπ/N+(1−k)π/2)i.sup.2k  (12)

[0189] An example of a Multipolar Configuration of Permanent Magnets is represented on FIG. 21.

Example 4—Magnetically Actuated Valve

[0190] The addition of another magnet affects the magnetic field gradient created by a quadrupole arrangement of permanent magnets. An additional permanent magnet was placed near the exit port of a fluidic device that had water running through; it created a pinch point within an anti-tube and stopped the flow of water.

[0191] The device according to the invention may work as a magnetically actuated valve.

Example 5—Magnetically Actuated Peristaltic Pump

[0192] A traveling wave inside the quadrupole device was created. The zero magnetic field point in the centre of the quadrupole is disrupted by the external (non-quadrupole) magnet, and by moving the magnet along the quadrupole a restriction point is created that effectively moves liquid. To this end, a wheel with 10 permanent magnets was placed around it (FIG. 5) with the wheel rotating on the top of a fluidic device.

[0193] One fluidic opening of the device comprising the quadrupole was immersed in a reservoir of water. When the wheel was rotated, it was observed that water flowed through the anti-tube and came out of the exit port of the fluidic device. While the wheel was running, water kept flowing through the anti-tube. However, water immediately stopped flowing when the rotation of the wheel stopped.

[0194] These experiments demonstrate that pumping can be achieved using magnetic pinching of a quadrupolar field.

Example 6—Life Science Applications

[0195] Blood is one of the most difficult liquids to handle as it easily causes clogging of tubes and red blood cell rupture by shearing (haemolysis). A TMB (3,3′,5,5′-Tetramethylbenzidine) immunoassay was used to characterize the residual blood remaining in an anti-tube manufactured according to the invention, with a design similar to the quadrupole of example 3.

[0196] After the circulation of blood, TMB substrate solution was used to rinse the anti-tube made by the diamagnetic liquid. As the TMB assay produces a chromogenic substrate solution, the colour of the solution was used to quantify the amount of blood remaining. As references, the fouling-properties of commercial Tygon tubes (regular and medical grade) were characterized. Regular Tygon tubes showed permanent adhesion of blood inside the tube (FIG. 6, note that triangles do not return to zero even after flushing many tube volumes). Remarkably, the result of the ferrofluid anti-tube of the invention was at same level as a medical grade Tygon tube.

Example 7—Estimation of Tube Diameter

[0197] FIG. 22 shows how the antitube diameter d changes with the dimensions of the magnetic flux source and the type of confining fluid. Good agreement is found between the experimental points for water antitubes and the predictions of Equations (1) and (2), using measured magnetization and interface energy. For ferrofluid tubes larger than 150 μm in ferrofluids, X-ray imaging can be used, while optical imaging of smaller tubes is possible for some fluids.

[0198] Miniaturization of the channels is possible thanks to an attractive feature of permanent magnets, namely that the fields they produce are independent of length scale l. Hence H, M and the magnetic energy density do not depend on channel size. The interface energy σ however scales as l.sup.−1; with an oil/water interface energy of 23 mJ m.sup.−2, a field of 100 mT and a susceptibility of 1, the antitube will become unstable below a diameter of 5 μm. Further miniaturization would require σ to be reduced. By combining a very strong ferrofluid (QK100 with a magnetisation of 100 kA m.sup.−1 in a hydrocarbon medium) and a double surfactant (e.g., Span-80 in the ferrofluid, and Tween-20 in the aqueous antitube), we estimate that antitube diameters of ˜100 nm could ultimately be achieved. Such nanometer-sized antitubes would allow practical nanofluidic devices to be realized.

Example 8—Mixing Fluids

[0199] Mixing of flow was demonstrated in a ferrofluid antitube Y-junction, which symmetrically split the flow. A less-paramagnetic fluid flowed through one branch of the Y-junction, a more-paramagnetic fluid flowed through the other branch of the Y-junction and fluids mixed in the third branch of the Y-junction.

[0200] Merging of liquid at a Y-junction was visualized using antitubes stabilized by a ferrofluid. Remarkably, mixing occurs immediately after the Y-junction due to the Kelvin-Helmholz instability. This is in striking contrast to the laminar flow observed in a 3D printed microfluidic chip with the same channel size and geometry as the antitube.