This invention relates to a magnetically controllable device such as a pump, and in particular to a small (for example sub-millimetre or micro-scale) pump device operable to drive or pump a fluid for movement. The pump may be used, for example, to deliver or dispense a fluid from a container or passage or may be used to agitate or mix a fluid within a container or the like. Whilst suitable for use as a pump, the invention is not restricted in this regard and may be employed in a range of other applications. There are many applications in which it would be desirable to be able to positively drive small quantities of a fluid for movement along, for example, a flow channel or the like. By way of example, such an arrangement may be used to allow the delivery of small, accurately controlled doses of medicinal fluids to a patient, or may be used to allow the delivery of small, accurately controlled volumes of fluid to a sample chamber for use in undertaking tests on the fluid. It will be appreciated, however, that this represents merely two examples of applications in which a pump may be used, and the invention is not restricted in this regard.

US8405477 describes a device that is capable of being propelled through a fluid, the device comprising a pair of magnetic elements that are coupled to one another by way of a flexible coupling. In use, the application of a varying magnetic field to the device causes relative movement between the elements, causing the device to 'swim' through the fluid. US8405477 further suggests that such a device, if tethered in a flow channel, may be used as a pump to drive fluids along a flow channel.

It is an object of the invention to provide a pump or other device suitable for use in applications of the type outlined hereinbefore. Whilst suitable for use in such applications, it will be appreciated that the invention is not restricted to use in such applications.

According to a first aspect of the invention there is provided a magnetically controllable device comprising a body defining a fluid flow channel, a first magnetic material particle located within the flow channel and rigidly secured to a wall defining the flow channel, and a second magnetic material particle located within the flow channel and moveable relative to the first particle, the first and second particles having different magnetic anisotropies at least in the direction of an axis upon which both of the particles lie.

In use, as a result of the different magnetic anisotropies, the application of a varying magnetic field to the device may cause relative movement between the first and second particles, causing the spacing of the first and second particles and/or the orientation of the second particle relative to the first particle to change. The change in relative position and/or orientation may cause a displacement of fluid along the flow channel. Accordingly, it will be appreciated that the application of a varying magnetic field may cause fluid to be pumped along the flow channel.

The second particle may be directly coupled to the first particle by an elastic coupling member. Alternatively, the second particle may be coupled to the wall of the flow channel by an elastic coupling member.

The pump may further comprise one or more additional magnetic material particles. By way of example, one or more additional first particles may be rigidly secured to the flow channel wall. Similarly, one or more additional second particles may be located within the flow channel. Where additional first and second particles are provided, the additional second particles may be movable relative to the respective additional first particles.

By appropriate selection of the location of the additional particles in the flow channel, the device may further serve as a valve. By way of example, if the flow channel is of forked form, control over the device may allow selective supply of fluid along chosen limbs of the flow channel.

Furthermore, the device may serve as a mixer or agitator. It will be appreciated that such an arrangement may be advantageous in that the pumping effect by which fluid may be displaced along the flow channel, in use, may be enhanced.

According to a second aspect of the invention there is provided a magnetically controllable device comprising a flexible substrate upon which a plurality of first particles are located and upon which a plurality of second particles are located, the first particles being of a different magnetic anisotropy to the second particles such that the application of a varying magnetic field to the device causes relative movement between the first particles and the second particles, the substrate flexing to accommodate such relative movement.

The substrate may take the form of a mesh.

The substrate may be shaped to be of tubular form, spherical form, or to adopt another three dimensional shape.

Different parts of the substrate may have different stiffnesses with the result that relative movement between certain of the particles may be resisted. In another aspect of the invention, a magnetically controllable device comprises a first particle and a plurality of second particles connected to the first particle, the first particle being of a different magnetic anisotropy to the second particles such that the application of a varying magnetic field to the device causes relative movement between the second particles and the first particle.

According to another aspect of the invention there is provided a magnetically controllable device comprising a body defining a fluid flow channel, a first magnetic material particle located within the flow channel and secured to a wall defining the flow channel by a flexible element.

The application of a varying magnetic field to the device may cause the orientation of the particle to change, the flexible element flexing to accommodate this movement, the flexing of the flexible element, upon repeated changes in the orientation of the particle, causing fluid to be moved along the flow channel.

Preferably, a plurality of such particles are located within the flow channel.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation illustrating a pump in accordance with an embodiment of the invention;

Figure 1a illustrates a modification of the pump illustrated in Figure 1 ;

Figure 2 is a view similar to Figure 1 illustrating an alternative embodiment; Figure 3 illustrates a modification to the arrangement of Figure 2; Figure 4 illustrates a further embodiment of the invention; Figures 5a and 5b illustrate further embodiments; Figure 6 is a view illustrating another embodiment of the invention; and

Figure 7 is a view representing another embodiment of the invention.

Referring firstly to Figure 1 , a magnetically controllable device in the form of a pump is illustrated comprising a body 10 in which a passage defining a flow channel 12 is formed, the flow channel 12 being bounded by a peripheral wall 14.

Located within the flow channel 12 is a first magnetic particle 16. The particle 16 is secured by way of a rigid mounting post 18 to the wall 14. It will be appreciated that the manner in which the first particle 16 is mounted is such that movement of the particle 16 relative to the body 10 and flow channel 12 is resisted.

Also located within the flow channel 12 is a second magnetic particle 20. The first and second particles 16, 20 are located in close proximity to one another so as to magnetically interact with one another. The second particle 20 is connected to the first particle 16 by a flexible or elastic material coupling 22. It will be appreciated that, although the first magnetic particle 16 is securely fixed within the flow channel 12 in such a manner that movement thereof is resisted, the flexible coupling 22 permits limited movement of the second particle 20 relative to the first particle 16. The limited movement permitted by the flexible coupling 22 may allow the spacing of the first and second particles 16, 20 to vary and/or may allow the relative orientations of the first and second particles 16, 20 to vary.

The first and second particles 16, 20 are of different materials and have different magnetic anisotropies, at least in the direction of an axis upon which the first and second particles lie. By way of example, one of the particles may be of hard magnetic form and the other may be of soft magnetic form. With the exception of the fact that the first particle 16 is rigidly secured to the channel wall 14, the pump is of a form similar to that described in US8405477. It will be appreciated that, in use, upon the application of a varying magnetic field to the device relative movement will occur between the particles, the positions and/or orientations of the particles changing relative to one another, and the flexible coupling 22 flexing to accommodate such movement. The relative movement may arise as a result of the magnetic interaction between the particles and the varying magnetic field, and/or as a result of changes in the magnetic interaction between the particles arising from the application of the varying magnetic field. As US8405477 describes how the application of a varying magnetic field will cause relative movement of the first and second particles 16, 20, a detailed description of the principles giving rise to the resulting movement is not set out herein.

In use, with the flow channel 12 charged with a fluid, a varying magnetic field is applied to the pump. As a result of the different magnetic anisotropies of the first and second particles 16, 20, the application of the varying magnetic field causes relative to movement to occur between the first and second particles 16, 20. The relative movement may take the form of the second particle 20 moving closer to or further from the first particle 16 (within the range of movement permitted by the coupling 22, and/or may take the form of a change in the orientation of the second particle 20 relative to the first particle 16. The nature of the movement is conveniently such that return movement of the second particle 20 follows a different path. As a consequence of the movement of the second particle 20 relative to the first particle 16, fluid is driven along the flow channel 12 past the particles 16, 20.

It will be appreciated that whilst a pump comprising a single pair of particles 16, 20 may serve to deliver of pump a small quantity of fluid along the flow channel 12, in many applications it may be preferred to provide one or more additional first particles 16' rigidly secured to the channel wall 14 and one or more additional second particles 20' coupled to respective ones of the additional first particles 14' by respective additional couplings 22, as shown in Figure 1 a. In such an arrangement, the application of the varying magnetic field will cause movement of each of the second particles 20 and additional second particles 20' relative to the first particles 16 and additional first particles 16' with the result that a greater quantity of fluid can be dispensed, or fluid can be pumped along the flow channel 12 at an increased rate.

The fluid delivery rate and direction may be accurately controlled by appropriate control over the magnetic field applied to the device, in use. The device may thus find application in controlling the delivery of, for example, medicines or drugs to a patient, or in conducting tests on small, accurately controlled samples. However, it is not restricted to such applications. In the arrangement shown in Figure 1 , the second particle 20 is directly coupled by the flexible coupling 22 to the associated first particle 16. Figure 2 illustrates an arrangement in which this is not the case, and instead the second particle 20 is coupled to the channel wall 14 by the flexible coupling 22. It will be appreciated that although not directly coupled to the first particle 16, the second particle 20 will still undergo substantially the same movement as occurs in the arrangement of Figure 1 upon the application of a varying magnetic field thereto. The operation thereof is substantially the same as that of Figures 1 and 1 a.

As with the arrangement of Figure 1 , the arrangement of Figure 2 may be modified to incorporate additional pairs of particles, if desired.

In the arrangements described hereinbefore, the particles 16, 20 are arranged in pairs, each second particle 20 being associated with a single respective first particle 16. It will be appreciated that this need not always be the case, and Figure 3 illustrates a variant of the arrangement of Figure 2 in which additional second particles 20' are provided, each being flexibly coupled to the channel wall 14 by a respective flexible coupling 22', the second particle 20 and each additional second particle 20' being movable relative to the first particle 16 upon the application of a varying magnetic field to cause fluid to be pumped along and/or dispensed from the flow channel 12. It will be appreciated that the variant shown in Figure 3 is equally applicable to any of the arrangements described hereinbefore. Where the first and second particles 16, 20 are directly coupled to one another, then the additional second particle 20' may be flexibly coupled to the second particle 20, for example, forming a flexible chain of particles which magnetically interact with one another.

Whilst the description hereinbefore is of the invention as serving to pump or deliver fluid from or along a flow channel, it will be appreciated that a range of other functions may be achieved using the arrangements described hereinbefore. By way of example, Figure 4 illustrates a complex device in which the flow channel 12 defines inlet channels 12a, a mixing chamber 12b, and outlet channels 12c. The particles located within the inlet channels 12a may serve to control the rate of fluid supply to the mixing chamber 12b. By appropriate control over the movement of the particles, the two (or more) inlet channels 12a may be used to supply different quantities of different fluids to the mixing chamber 12b. Within the mixing chamber 12b, the particle movement may be used to achieve agitation or mixing of the fluids. The particles within the outlet channels 12c may be operated to control the proportion of mixed fluid delivered through each of the outlet channels 12c. Accordingly, the particles located therein may serve, effectively, as a valve. It will be appreciated that the particle movement may be used for other purposes than as described above.

In the arrangement of Figure 4, movement of all of the second particles may be achieved using a single, common varying magnetic field, and the orientations of the particles and operation of the electromagnet or the like producing the varying magnetic field may be such as to enable selection of which of the particles cause fluid movement at any given time. In order to maximise the degree of control, it may be desirable to use a 3D magnetic system to produce the varying magnetic field.

In each of the embodiments described hereinbefore, whilst it is important that the first and second particles 16, 20 are in close proximity to one another so as to magnetically interact with one another, it will be appreciated that their relative orientations need not be as illustrated.

It will be appreciated that by varying the frequency and amplitude of the varying magnetic field, the relative movements of the particles 16, 20 can be accurately controlled, and as a consequence, the rate of pumping or dispensing of fluid along or from the channel 12 can be accurately controlled.

Whilst Figure 3 illustrates a pump device including a single first particle and a plurality of second particles interacting therewith, the device may be used in other, non- pumping applications. By way of example, as shown in Figures 5a and 5b, if the particles are flexibly connected to one another but not anchored or tethered to a fixed position within a flow passage, the device may serve as a swimmer or the like. Figures 5a illustrates the case where the particles are arranged in a chain, in this case with the first particle at an intermediate position within the chain, and Figure 5b illustrates a case in which each particle is directly connected to each of the other particles. In each case, further particles may be incorporated if desired. Arrangements of this type are thought to be of enhanced performance as compared to the simple structures of US 8405477.

Further benefits may be achieved by connecting or bundling together two or more of the devices or structures outlined hereinbefore. By way of example, Figure 6 illustrates a device comprising a flexible substrate 30. As illustrates, the substrate 30 takes the form of a mesh defining a plurality of intersections 32. At each intersection 32 is located one of the particles 16, 16', 20, 20'. In use, the application of a varying magnetic field to the device causes relative movement to occur between at least some of the particles, the substrate 30 flexing to accommodate such relative movement.

If desired, certain parts of the substrate 30 may be more rigid than other parts thereof so that relative movement between at least some of the particles is resisted.

The device may serve as, for example, a swimmer or pump or other conveyor device.

Whilst described as taking the form of a mesh, the substrate may take other forms.

The substrate 30 could be shaped to be of, for example, tubular or spherical form or to take another three dimensional shape. Where of tubular form, it could serve as a pump to be located within a passage, pumping fluid along the passage when activated by the application of a varying magnetic field. Whilst a structure of the form outlined above is of porous form, the pores thereof are sufficiently small that it is thought that surface tension will result in little, if any, fluid passing through the pores when the device is not activated. In such an arrangement, activation of the device by the application of a magnetic field thereto may result in fluid being driven through the pores, for example from the interior of the device to the exterior thereof.

Similarly, if the device is shaped to be of spherical or other closed three dimensional shape, activation thereof may result in fluid being dispensed from the interior of the device to the exterior thereof.

One application in which such a device may be used is in the delivery of medicines or drugs. By way of example, the device may be activated only once it has reached a desired location within a body so as to deliver precise quantities of medicines or drugs to desired locations.

In the arrangements described hereinbefore, each device contains particles of two different materials, and operation of the devices requires there to be relative movement between the particles, for example changing their relative positions and/or their relative orientations. This need not always be the case and Figure 7 illustrates a device in which particles of just a single magnetic material are present. In the arrangement of Figure 7, particles 16, 16' are located within a flow channel 12, and are tethered to the wall 14 of the flow channel 12 by flexible couplings 22, 22'. In use, upon the application of a varying magnetic field to the device, the particles 16, 16' will undergo angular movement. In order to accommodate this movement, the flexible couplings 22, 22' must flex. The nature of the flexing movement is such that, where the magnetic field is repeatedly varied, the flexing causes fluid located within the flow channel 12 to be driven along the flow channel 12. The device thus serves as a pump.

It will be appreciated that, if desired, the device may be formed as a valve or to have other functionality as described hereinbefore with reference to Figure 4. Whilst specific embodiments of the invention are described hereinbefore, it will be appreciated that a wide range of modifications and alterations may be made thereto without departing from the scope of the invention as defined by the appended claims.