Field

The present application relates to a peristaltic pump, a fluid delivery device and a flexible conduit.

Background

A peristaltic pump may be used for pumping a fluid. WO2021/155048 A2 discloses a ratcheting peristaltic pump including a ratcheting driving mechanism. The ratcheting driving mechanism can include muscle wire.

It is desirable to control the positive displacement of a peristaltic pump more accurately. For example, a peristaltic pump may be used to deliver insulin to a person. It is important to carefully control the amount and/or rate of fluid that is delivered.

Summary

According to an aspect of the present disclosure, there is provided a peristaltic pump comprising: a flexible conduit for containing a fluid; and an SMA actuator assembly comprising: a compressor part configured to compress the flexible conduit as the compressor part moves relative to the flexible conduit; and one or more SMA elements configured, on contraction, to cause the compressor part to be driven relative to the flexible conduit so as to compress the flexible conduit and displace fluid within the flexible conduit. Optionally, the compressor part may be driven over a continuous range relative to the flexible conduit.

The high accuracy of the SMA drive offers high resolution of dispensing. This may allow a higher concentration fluid to be used without unduly increasing the possibility of dispensing an amount or at a rate that is unsatisfactorily far from a target amount and/or rate. Use of a higher concentration of fluid may allow the volume of fluid held in the peristaltic pump to be reduced. This may help to reduce the size of the peristaltic pump.

By using one or more SMA elements to drive displacement of the fluid, the fluid can be displaced continuously (i.e. uninterrupted). The displacement of the fluid may be controlled over a continuous range, rather than only at discrete intervals.

Optionally, the SMA actuator assembly comprises a movable part arranged to move in a plane. The one or more SMA elements may be arranged, on contraction, to move the movable part in the plane so as to drive the compressor part over the continuous range relative to the flexible conduit. The movable part may be directly controlled by the contraction of the one or more SMA elements. The position of the movable part may be controlled accurately over a continuous range, thereby allowing the displacement of the fluid to be controlled continuously. The movable part may be integral with or connected to the compressor part.

Optionally, the one or more SMA elements are arranged, on contraction, to move the movable part in the plane so as to drive the compressor part rotationally over the continuous range relative to the flexible conduit. The compressor part may undergo rotational motion. For example, the compressor part may be moved over a cycle (e.g. in a circular or substantially circular path). This may help the peristaltic pump to be used without interruption. The peristaltic pump may be used to displace any arbitrary amount of the fluid.

Optionally, the SMA actuator assembly comprises a rotating part coupled to the movable part and arranged to rotate about a rotation axis. The compressor part may be secured to or may be integral with the rotating part. The movable part may be arranged to move in a plane perpendicular to the rotation axis. The one or more SMA elements may be arranged, on contraction, to move the movable part, such that coupling between the movable part and the rotating part drives continuous rotation of the rotating part about the rotation axis, thereby driving the compressor part over the continuous range relative to the flexible conduit.

The use of the rotating part allows an SMA rotatory actuator to be used to drive the peristaltic pump. A rotary actuator may have a particularly low-profile design. This may be particularly desirable when the peristaltic pump is to be used by being secured to the body of a patient, with the fluid being dispensed over a longer period of time. This may help to reduce the inconvenience to the user of the device by reducing the extent to which the device protrudes above the skin. The rotating part may be particularly accurately indexed using control of the one or more SMA elements. This helps to increase the accuracy of controlling the displacement of the fluid.

Optionally, the movable part is arranged to move along a boundary of the rotating part. The one or more SMA elements may be arranged, on contraction, to move the movable part along the boundary of the rotating part, such that contact between the movable part and the rotating part drives continuous rotation of the rotating part about the rotation axis, thereby driving the compressor part over the continuous range relative to the flexible conduit. By moving the movable part along the boundary of the rotating part, the rotational position of the rotating part can be particularly accurately controlled. The rotational position of the rotating part may be controlled so as to control the displacement of the fluid. This can help to displace the fluid continuously (i.e. uninterrupted) over a continuous range of fluid amounts.

Optionally, the movable part is coupled to the rotating part via a crank mechanism. The one or more SMA elements may be arranged, on contraction, to move the movable part, such that the crank mechanism between the movable part and the rotating part drives continuous rotation of the rotating part about the rotation axis, thereby driving the compressor part over the continuous range relative to the flexible conduit.

The design of the drive mechanism may be selected so as to match a particular application. By providing a crank mechanism, it may not be necessary to use a gear for example. This may help to simplify the design of the peristaltic pump and/or make the peristaltic pump more robust. The number of moving parts of the peristaltic pump may be reduced. This may help to reduce the cost of manufacturing the peristaltic pump.

Optionally, the peristaltic pump comprises a further SMA actuator assembly comprising a further movable part arranged to move in a further plane. The further SMA actuator assembly may comprise one or more SMA elements configured, on contraction, to move the further movable part in the plane so as to drive the compressor part over the continuous range relative to the flexible conduit. The further plane may be coplanar with or parallel to the plane in which the movable part is arranged to move.

By providing a further SMA actuator assembly, a compressor part may be driven with a greater force and/or efficiency. This may, in turn, allow drive mechanisms that can be controlled more accurately to be used, without unduly reducing the overall force applied to the flexible conduit.

Optionally, the compressor part is sandwiched between the movable part and the further movable part.

For example, one or more compressor parts may be sandwiched between two rotary actuators. This may help to reduce the radial forces on the rotational axis. This may, in turn, improve the robustness of the peristaltic pump and/or increase the lifetime of the peristaltic pump.

Optionally, the movable part and the further movable part are configured to be moved out of phase of each other. This may help to balance out the radial forces on the axis. This may help to reduce the possibility of the peristaltic pump being damaged during use.

Optionally, the compressor part is arranged relative to the movable part such that a position of the compressor part in the plane is determined by a position of the movable part in the plane, whereby movement of the movable part in the plane drives the compressor part over the continuous range relative to the flexible conduit.

For example, the compressor part and the movable part may be formed integrally, i.e. they may be different parts of the same element. Alternatively, the compressor part may be secured relative to the movable part. The position of the movable part may be controlled accurately within the plane by controlling the SMA elements. This may directly allow the position of the compressor part to be controlled to the same level of accuracy as the movable part. The high level of control of the one or more SMA elements may be directly translated into a high level of control of displacement of the fluid within the peristaltic pump.

Optionally, the one or more SMA elements are arranged, on contraction, to move the movable part along a cyclical path in the plane.

The movable part may be moved in a cyclical path which may therefore be repeated continuously. This may help the peristaltic pump to be used to displace fluid continuously over a longer period of time.

Optionally, the cyclical path is circular or substantially circular.

By moving the movable part over a circular path, the movement of the movable part may be particularly smooth, which may help to improve the accuracy of movement of the movable part. In turn, this may help to improve the accuracy with which fluid may be displaced.

Optionally, the compressor part is arranged relative to the movable part such that a rotational position of the compressor part relative to the flexible conduit is determined by a rotational position of the movable part relative to the flexible conduit.

The movable part may be rotated, which may provide a convenient way of continuously running the peristaltic pump. The accurate rotation of the movable part by the one or more SMA elements may be translated directly into an equally accurate displacement of the fluid.

Optionally, the compressor part is arranged to rotate relative to the movable part. By providing that the compressor part may rotate relative to the movable part, the friction between the compressor part and the flexible conduit may be reduced. For example, the compressor part may be provided as a roller with a surface that pushes against the surface of the flexible conduit. The roller may rotate during the compression of the flexible conduit. This may reduce undesirable forces on the compressor part by the flexible conduit. This may help to improve the accuracy of movement of the compressor part.

Optionally, the peristaltic pump comprises a positional guide configured to constrain the position of the movable part in the plane so as to hold the compressor part in compression against the flexible conduit.

The positional guide may help to provide a constraint for the movable part and/or the rotatable part in the plane. This may help to reduce the number of parts of the peristaltic pump. For example, it may not be necessary to provide an additional element that provides the constraint for the movable part in the plane. The positional guide may help to increase compression of the flexible conduit.

Optionally, the positional guide comprises an arm pivoted on a pivot and configured to hold the movable part a predetermined distance from the pivot.

The arm may be located so as not to increase the footprint of the peristaltic pump within the plane. This may help to reduce the overall size of the peristaltic pump.

Optionally, the one or more SMA elements are arranged, on contraction, to move the movable part over the continuous range relative to the flexible conduit while substantially maintaining a rotational position of the movable part relative to the flexible conduit.

It may not be necessary to rotate the movable part. This may increase the design freedom of the SMA mechanism used to drive the movement of the movable part. This may help to simplify the design of the driving mechanism of the peristaltic pump.

Optionally, the compressor part comprises at its outer surface one or more flexible members arranged to be capable of flexing tangentially when compressing the flexible conduit.

This may help to reduce friction between the flexible conduit and the compressor part during motion of the compressor part relative to the flexible conduit. This may help to reduce undesirable forces on the compressor part, which may, in turn, improve the accuracy with which the compressor part can be moved. Optionally, the peristaltic pump comprises a plurality of compressor parts configured to compress the flexible conduit as they move relative to the flexible conduit. By providing a plurality of compressor parts, the displacement of fluid through the flexible conduit may be controlled more accurately. For example, the compression of the flexible conduit may be controlled at a greater number of positions along the flexible conduit.

Optionally, the one or more SMA elements are configured, on contraction, to cause a plurality of the compressor parts to be driven over the continuous range relative to the flexible conduit.

The SMA elements may drive a plurality of compressor parts. This may help to reduce the number of driving mechanisms that are required in order to drive a plurality of compressor parts relative to the flexible conduit. This may help to reduce the number of parts of the peristaltic pump and/or reduce the cost of manufacturing the peristaltic pump.

Optionally, the peristaltic pump comprises a further SMA actuator assembly comprising one or more SMA elements configured, on contraction, to cause one or more of the compressor parts to be driven over the continuous range relative to the compressor parts.

Two or more compressor parts may be driven by different actuators. This may have the benefit of providing an additional region of compression of the flexible conduit. This may help the displacement of the fluid to be controlled more accurately.

Optionally, the peristaltic pump comprises a housing in which the flexible conduit is fitted.

By providing a housing, the position and arrangement of the flexible conduit may be controlled more accurately. This may allow the relative position of the compressor parts and the flexible conduit to be controlled more accurately. This may help to improve the accuracy of displacement of the fluid. Optionally, the peristaltic pump comprises a further SMA actuator assembly comprising a plurality of SMA elements configured, on contraction, to cause the housing to be driven relative to the compressor part.

For example, the housing may be driven in the opposite direction to the compressor part. This may help to increase the amplitude of compression of the flexible conduit.

Optionally, the housing may be connected to or integral with the movable part. In this way, the housing may provide the constraint (in the x-y plane) for the rotating part, for example in embodiments in which the movable part is arranged to move along a boundary of the rotating part (where the movable part moves in the x-y plane).

Optionally, the compressor part comprises a wiper or a roller.

By providing a wiper or a roller, the friction between the compressor parts and the flexible conduit may be reduced. This may help to increase the accuracy with which the compressor part is moved relative to the flexible conduit, for example by reducing unwanted frictional forces on the compressor part.

Optionally, the peristaltic pump comprises a one-way clutch configured to prevent a direction in which the compressor part is driven relative to the flexible conduit from being reversed.

This may help to prevent at pressure reversing the peristaltic pump, which may happen if, for example, the peristaltic pump is depowered.

Optionally, the peristaltic pump comprises a brake configured to controllably prevent the compressor part from being driven relative to the flexible conduit. The brake may be a zero-hold-power brake, i.e. the brake may be configured to prevent the compressor part moving with respect to the flexible conduit when the pump is powered off (and in particular when no power is supplied to the one or more SMA elements).

Alternatively, the brake could be an active brake which is controlled by one or more SMA elements or another actuator.

By providing a brake, movement in one or both directions of the peristaltic pump may be prevented when the peristaltic pump is powered off. This may help to reduce the possibility of fluid being undesirably displaced and/or the flexible conduit being undesirably filled with another type of fluid.

Optionally, the flexible conduit comprises two layers defining a channel between them and arranged to collapse flat against each other, thereby closing the channel, when the flexible conduit is compressed.

The design of the flexible conduit may be selected so as to reduce, or minimise, forces and/or displacement needed to seal the tube under the compression from the compressor part. This may allow the flexible conduit to seal more easily under the compressor part. This may allow a greater range of driving mechanisms for the compressor part to be used. Optionally, one layer of the flexible conduit is connected to the compressor part.

By connecting one layer of the flexible conduit to the compressor part, the flexible conduit may be more easily opened during use of the peristaltic pump, in particular after the two layers have been sealed together.

Optionally, the other layer of the flexible conduit is connected to a component that has a fixed position relative to the flexible conduit.

For example, the other layer of the flexible conduit may be connected to the housing. As the peristaltic pump is driven, following compression of the flexible conduit, the flexible conduit may be opened as the compressor part and the housing, for example, move away from each other. This may help to reduce the possibility of the flexible conduit remaining undesirably sealed or not opening to its full extent. This may help to increase the accuracy with which the fluid is displaced.

Optionally, the flexible conduit comprises a first portion separated from a second portion by two fold lines, one at each of two opposing edges of the conduit. A channel is defined between the first and second portions. The first and second portions may be arranged to collapse flat against each other, thereby closing the channel, when the flexible conduit is compressed. One of the first and second portions may be connected to another part of the apparatus (e.g. the housing or compressor part) as described above for one layer of a two-layer conduit.

Optionally, the one or more SMA elements comprises a total of four SMA elements, specifically SMA wires. Optionally, none of the four SMA wires are collinear. Optionally, the four SMA wires are capable of being selectively driven to move the movable part relative to the flexible conduit to any position in a range of movement without applying any net torque to the moveable part in the plane of movement of the movable part. Optionally, the SMA wires are connected between the movable part and a support structure.

Optionally, the peristaltic pump comprises a controller configured to measure an electrical characteristic of the one or more SMA elements, and determine a position of the movable part based on the electrical characteristic. The electrical characteristic may be (electrical) resistance, for example.

By providing that the controller can perform resistance control of the one or more SMA elements, the SMA elements can be controlled particularly accurately. In turn, this is translated into a particularly accurate control of the displacement of the fluid. According to another aspect of the present disclosure, there is provided a fluid delivery device comprising the peristaltic pump as described elsewhere in this document. The flexible conduit may be configured to hold the fluid to be delivered.

The present apparatuses may be employed within a fluid delivery device so as to improve the accuracy with which a fluid is delivered. For example, insulin may be delivered to the body of patient particularly accurately.

According to another aspect of the disclosure, there is provided a flexible conduit for a peristaltic pump. The flexible conduit comprises two layers secured to each other at opposing edges so as to define a channel between the layers. The layers are arranged to collapse flat against each other, thereby closing the channel, when the flexible conduit is compressed.

The flexible conduit is designed to reduce forces and/or displacement needed to seal the flexible conduit under compression from a wiper, for example, as a peristaltic pump.

According to another aspect of the disclosure, there is provided a flexible conduit for a peristaltic pump. The flexible conduit comprises a first portion separated from a second portion by two fold lines, one at each of two opposing edges of the conduit. A channel is defined between the first and second portions. The first and second portions are arranged to collapse flat against each other, thereby closing the channel, when the flexible conduit is compressed.

In the above embodiments, and in peristaltic pumps generally, the compressor part moves over the flexible conduit and at some point, the compressor part releases the conduit and it expands again, from its compressed state back to an uncompressed state. Especially when pumping very low volumes of fluid, this release of the conduit causes variations in flow rate. Embodiments of a peristaltic pump which alleviates this disadvantage is now described.

According to an aspect of the disclosure there is provided a peristaltic pump. The pump comprises a flexible conduit for containing a fluid, wherein the flexible conduit is arranged in a loop. The pump further comprises a plurality of compressor parts configured to compress the flexible conduit as the compressor part moves relative to the flexible conduit. The pump further comprises an actuator assembly configured to drive movement of the compressor parts along the flexible conduit. The flexible conduit comprises: a first region in which, in use, a first volume of fluid is displaced by movement of a compressor part per unit angle along the flexible conduit, wherein the first volume is constant over the first region; a second region in which, in use, a second volume of fluid is displaced by movement of a compressor part per unit angle along the flexible conduit, wherein the second volume is constant over the second region and wherein the second volume is greater than the first volume; and a first transition region which connects a first end of the first region to a second end of the second region; a second transition region which connects a first end of the second region to a second end of the first region; a fluid inlet disposed in the first transition region; and a fluid outlet disposed in the second transition region.

As the compressor parts move along the flexible conduit: the compressor parts compress the conduit fully in the first and second regions, so as to separate the respective region into two volumes which are not in fluidic communication with each other and to displace fluid along the conduit, and the compressor parts do not compress the flexible conduit fully in the first and second transition regions such that the respective region contains a single volume of fluid.

Such a pump uses a continuous circuit of a flexible conduit which can be compressed by the compressor parts. Various different regions of the flexible conduit are provided which have various characteristics and these regions together result in effective pumping of fluid through the conduit and out through the outlet. The absence of a ramp-on and ramp-off event (which occurs as the compressor parts pass by the ends of the tubes in other peristaltic pumps) allows the flow rate of fluid to be much more continuous or, if driven by an indexing mechanism, more consistent between each activation of the indexing drive.

Optionally, the actuator assembly is configured to drive rotation of the compressor parts around an axis of rotation.

Optionally, the first region of the flexible conduit is an arc having a first radius and the second region of the flexible conduit is an arc having a second radius, wherein the second radius is greater than the first radius.

Optionally, each of the first and second transition regions comprises a first portion which is further from the axis of rotation than a second portion of the respective transition region. Optionally, the compressor parts are angularly spaced equally around the axis of rotation.

Optionally, the actuator assembly comprises a constraining component which is configured to: constrain each of the compressor parts to a respective fixed angular position with respect to the constraining component; and allow movement of the compressor parts along a radial direction (with respect to the axis of rotation). In some embodiments the compressor parts may each comprise a rolling element. In some embodiments the constraining element may comprise a plurality of grooves or apertures. The grooves or apertures may be equally angularly-spaced around the axis of rotation. For example the constraining element may comprise a sheet of material comprising a plurality of grooves (or elongate apertures) each arranged along a radial direction, with respect to the axis of rotation.

Optionally, the actuator assembly comprises a constraining component comprising a plurality of grooves or apertures which are angularly spaced around the axis of rotation and which each constrain a respective compressor part, wherein each groove or aperture allows movement of the compressor part along a path such that the angular position and the radial position of the compressor part with respect to the constraining component varies along the path. In some embodiments the compressor parts each comprise a rolling element. In some embodiments the grooves or apertures may be equally angularly spaced with respect to the axis of rotation. For example the constraining element may comprise a sheet of material comprising a plurality of grooves or apertures.

Optionally, each compressor part is an elongate component which is aligned with a respective radial direction. For example, the compressor parts may be cylindrical rollers.

Optionally, a cross-sectional area of the flexible conduit (when in a neutral, uncompressed state) varies along a length of the flexible conduit.

Optionally, a cross-sectional area of the flexible conduit (when in a neutral, uncompressed state) in the first region is a first area and is constant along the first region, and wherein a cross-sectional area of the flexible conduit along the second region is a second area and is constant along the second region, wherein the second area is greater than the first area.

Optionally, a cross-sectional area of the flexible conduit varies along the first transition region and/or a cross-sectional area of the flexible conduit varies along the second transition region. Optionally, the actuator assembly comprises one or more SMA elements configured, on contraction, to cause the compressor parts to be driven relative to the flexible conduit. The actuator assembly may comprise an arrangement as described with reference to Figures 1, 3a or 3b, for example.

Brief description of the drawings

Certain embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of an SMA actuator assembly;

Figure 2 is a schematic view of a peristaltic pump;

Figure 3A is a schematic view of part of a peristaltic pump;

Figure 3B is a schematic view of part of a peristaltic pump;

Figure 4 is a schematic view of a peristaltic pump;

Figure 5 is a schematic view of a peristaltic pump;

Figure 6 is a schematic view of a peristaltic pump;

Figure 7 is s schematic view of an uncompressed flexible conduit;

Figure 8 is a schematic view of a compressed flexible conduit;

Figure 9 is a schematic view of an uncompressed flexible conduit;

Figure 10A is a plan view of a peristaltic pump;

Figure 10B is a perspective view of a portion of a peristaltic pump;

Figure IOC is a perspective view of a portion of a peristaltic pump;

Figure 10D is a cross-sectional view of a conduit;

Figure 10E is an exploded view of a peristaltic pump;

Figure 11 is a plan view of a peristaltic pump;

Figure 12 comprises cross-sectional views of a portion of a peristaltic pump;

Figure 13 is a cross-sectional view of a portion of a peristaltic pump;

Figure 14A comprises cross-sectional views of a portion of a peristaltic pump;

Figure 14B comprises cross-sectional views of a portion of a peristaltic pump;

Figure 15 is a cross-sectional view of a portion of a peristaltic pump; and Figure 16 is a cross-sectional view of a peristaltic pump.

Detailed description

An embodiment relates to a peristaltic pump 2. Figure 2 is a schematic view of a peristaltic pump 2. The peristaltic pump 2 is a type of positive displacement pump. The peristaltic pump 2 may be configured to pump a fluid. The peristaltic pump 2 comprises a flexible conduit 27. The flexible conduit 27 is for containing a fluid. The flexible conduit 27 may be a flexible tube. The conduit may comprise a tube with one or more chambers. Optionally, the flexible conduit 27 defines a lumen 73 in which the fluid may be contained.

The peristaltic pump 2 comprises an SMA actuator assembly comprising a compressor part 21. The compressor part 21 is configured to compress the flexible conduit 27 as the compressor part 21 moves relative to the flexible conduit 27. The compressor part 21 may comprise a wiper or a roller, for example. The compressor part 21 compresses the flexible conduit 27.

As shown in Figure 2, part of the flexible conduit 27 under compression is closed. This forces the fluid to move through the flexible conduit 27 as the compressor part 21 moves. As shown in Figure 2, the flexible conduit may comprise an inlet 23 and an outlet 24. The fluid may move through the flexible conduit 27 from the inlet 23 to the outlet 24.

As the flexible conduit 27 opens to its natural state after the compressor part 21 passes, more fluid may be drawn into the flexible conduit 27. The fluid may be drawn into the flexible conduit 27 through the inlet 23.

As shown in Figure 2, optionally the peristaltic pump 2 comprises a plurality of compressor parts 21 compressing the flexible conduit 27. A body of fluid may be trapped between adjacent compressor parts 21. The body of fluid is transported through the flexible conduit 27 towards the outlet 24.

Figure 1 is a schematic view of part of an SMA actuator assembly 1. As shown in Figure 1, the SMA actuator assembly 1 comprises one or more SMA wires 30. The one or more SMA wires 30 are configured, on contraction, to cause the compressor part 21 to be driven over a continuous range relative to the flexible conduit 27 so as to compress the flexible conduit 27 and displace fluid within the flexible conduit 27. The peristaltic pump 2 is configured to run continuously.

The SMA actuator assembly 1 functions as an SMA drive for the peristaltic pump 2. The SMA actuator assembly 1 has relatively high accuracy. This means that the amount of fluid that is displaced through the outlet 24 of the flexible conduit 27 can be accurately controlled. The forces applied by the one or more SMA wires 30 may be accurately controlled. The extent to which the one or more SMA wires 30 contract may be accurately controlled. The high accuracy of the SMA drive offers high resolution of dispensing of the fluid. This means that the amount of fluid dispensed by the peristaltic pump 2 may be accurately controlled. Additionally or alternatively, the rate of dispensing of fluid by the peristaltic pump 2 may be accurately controlled.

One possible application for the peristaltic pump 2 is for delivering a drug. For example, the peristaltic pump 2 may be configured to deliver insulin to the body of a user. The peristaltic pump 2 may be attached to the body of a user. The peristaltic pump 2 may be provided with an adhesive base to stick onto the skin. The peristaltic pump 2 may sit protruding above the skin.

By providing a high resolution of dispensing, a higher concentration of drug (e.g. insulin) may be used without unduly risking lowering the accuracy of insulin dosage. If higher concentration insulin is used, then the volume of fluid required to be contained within the peristaltic pump 2 may be reduced. By reducing the volume of fluid held in the peristaltic pump 2, the size of the peristaltic pump 2 may be reduced. By reducing the size of the peristaltic pump 2, the inconvenience to the user may be reduced, particularly when the peristaltic pump 2 sits protruding above the skin.

The peristaltic pump 2 is configured to dispense fluid without requiring valves that can open and close. This helps to increase the accuracy of dispensing because the opening and closing of valves can otherwise reduce the accuracy of dispensing.

By providing that the peristaltic pump is driven by SMA wires, it is possible for the compressor part 21 to be driven over a continuous range relative to the flexible conduit 27. It is possible for the peristaltic pump 2 to be driven continuously (i.e. uninterrupted). This allows the peristaltic pump to be used, for example, to continuously deliver insulin into the body. By providing that the compressor part 21 can be driven over a continuous range, the amount of fluid delivered can be controlled more accurately. The accuracy of delivery of the fluid is not limited by the granularity caused by, for example, a ratcheting mechanism.

As shown in Figure 1, optionally the SMA actuator assembly 1 comprises a movable part 20. The movable part 20 may be arranged to move in a plane. For example, the movable part 20 shown in Figure 1 is arranged to move in the X-Y plane. The one or more SMA wires 30 are arranged, on contraction, to move the movable part 20 in the plane so as to drive the compressor part 21 over the continuous range relative to the flexible conduit 27. The one or more SMA wires may be arranged to move the movable part 20 directly. This means that the SMA wires 30 are connected directly to the movable part 20, or to another component that has a fixed position relative to the movable part 20. A variety of different mechanisms may be employed to drive the compressor part 21 using one or more SMA actuator assemblies 1. Figure 1 schematically depicts one possible type of SMA actuator assembly 1. Figure 1 shows an SMA actuator assembly 1 comprising a rotary actuator. The rotary actuator is configured to transfer the contraction of the SMA wires 30 into rotational motion. Optionally, the one or more SMA wires 30 are arranged, on contraction, to move the movable part 20 in the plane so as to drive the compressor part 21 rotationally over the continuous range relative to the flexible conduit 27.

In the view shown in Figure 2, the compressor part 21 is arranged to be driven in a clockwise direction as indicated by the curved arrow. The compressor part 21 is configured to rotate about a rotational axis R.

As shown in Figure 1, optionally the SMA actuator assembly 1 comprises a support structure 10, a movable part 20 and a rotating part 40. The rotating part 40 is coupled to the movable part 20 and arranged to rotate about a rotation axis R. As shown in Figure 2, the compressor part 21 is secured to the rotating part 40. Alternatively the compressor part 21 may be integral with the rotating part 40. As the rotating part 40 rotates about the rotation axis R, the compressor part 21 is caused to rotate about the rotation axis R.

In the arrangement shown in Figure 1, the support structure 10 is used as a reference point to describe movement of the rotating part 40 and the movable part 20. Optionally, the rotation axis R is perpendicular to the X-Y plane, namely the plane in which the movable part 20 is arranged to move.

The rotating part 40 may be arranged to only rotate relative to the support structure 10 about the rotation axis R, so translational movement of the rotating part 40 relative to the support structure 10 may be constrained.

Optionally, the movable part 20 is arranged to move in a plane perpendicular to the rotation axis R. The one or more SMA wires 30 may be arranged, on contraction, to move the movable part 20, such that coupling between the movable part 20 and the rotating part 40 drives continuous rotation of the rotating part 40 about the rotation axis R, thereby driving the compressor part 21 over the continuous range relative to the flexible conduit 27.

The SMA wires 30 drive movement of the movable part 20. SMA material has the property that on heating it undergoes a solid-state phase change which causes the SMA material to contract. A range of contraction occurs as the temperature of the SMA increases over the range of temperature in which there occurs the transition of the SMA material from the Martensite phase to the Austenite phase. Conversely, on cooling of the SMA wires 30 so that the stress therein decreases, the SMA wires 30 expand under tensile forces (e.g. from opposing ones of the SMA wires 30 or from springs or other resilient elements). This allows the movable part 20 to move in the opposite direction. The position of the movable part 20 relative to the support structure 10 in the x-y plane may thus be controlled by selectively varying the temperature of the SMA wires 30. This may be achieved by passing through SMA wires 30 selective drive currents or voltages, for example pulse-width modulated (PWM) control signals, that provide resistive heating. Heating is provided directly by the drive signals. Cooling is provided by reducing or ceasing the drive signals to allow the SMA wires 30 to cool by conduction, convection and/or radiation to the surroundings.

In the embodiment shown in Figure 1, the SMA actuator assembly 1 comprises a total of four SMA wires 30. The four SMA wires 30 are connected between the support structure 10 and the movable part 20. Each of the SMA wires 30 is held in tension, thereby applying a force between the movable part 20 and the support structure in a direction in the plane of movement of the movable part 20. In operation, the SMA wires 30 move the movable part 20 relative to the support structure in two orthogonal directions (x and y, as shown in Figure 1) in the plane.

The SMA wires 30 each extend perpendicular to the z axis. In this arrangement, the SMA wires 30 extend in a common plane which is advantageous in minimising the size of the SMA actuator assembly along the z axis.

Each of the SMA wires 30 is arranged along one side of the movable part 20. Thus, the four SMA wires 30 may consist of two pairs of SMA wires arranged on opposite sides of the movable part 20. One pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a first direction in the plane, and the other pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a second direction in the plane transverse to the first direction. Movement in directions other than parallel to the SMA wires 30 may be driven by a combination of actuation of these pairs of the SMA wires 30 to provide a linear combination of movement in the transverse directions. Another way to view this movement is that simultaneous contraction of any pair of the SMA wires 30 that are adjacent each other in the loop will drive movement of the movable part 20 in a direction bisecting those two of the SMA wires 30.

The SMA wires 30 move the movable part 20 translationally in the x-y plane, and in particular along the boundary 45 of the rotating part 40. In the depicted embodiment, the SMA wires move the movable part 20 along a circular path so as to move along the boundary 45 of the rotating part 40. In general, the movement path of the movable part 20 may be non-circular for other geometries of the rotating part 40 and/or movable part 20. The movable part 20 remains in constant contact with the rotating part 40 as it moves around the rotating part 40. Movement of the movable part 20 drives rotation of the rotating part 40. For example, as shown in Figure 1, translational movement of the movable part 20 in direction 22 drives rotation 46 of the rotating part 40 around the rotation axis R. The SMA actuator assembly 1 is thus capable of generating continuous rotation. The rotating part 40 can be rotated indefinitely and without interruption. Using SMA wires 30 to ultimately drive rotation has the benefit of providing rotation with a relatively high torque using relatively little electrical power, due to the high energy density of SMA. The SMA actuator assembly 1 can further be made compact compared to motors making use of other actuators, such as induction coils.

By providing an SMA rotary actuator to drive the peristaltic pump 2, the peristaltic pump 2 may have a lower profile design. This is because an SMA rotary actuator has a particularly low-profile design.

In the depicted embodiment, the rotating part 40 is an inner gear 42a and the movable part 20 comprises an outer gear 22a. The gears 22a, 42a comprise complementary teeth, i.e. the teeth of the rotating part 40 and the teeth of the movable part 20 intermesh. The outer gear 22a comprises a greater number of teeth than the inner gear 42a. In particular, the outer gear 22a comprises at least one more tooth than the inner gear 42a. The outer gear 22a may, for example, comprise a number of teeth that is greater than 10, preferably greater than 25, further preferably greater than 50. The inner gear 42a may comprise, for example at least 1 fewer tooth than the outer gear 22a, or 2 or more fewer teeth than the outer gear.

In alternative embodiments, the movable part 20 and the rotating part 40 do not comprise complementary teeth. Instead, the movable part 20 and the rotating part 40 may comprise surfaces that constrain sliding between the movable part 20 and the rotating part 40 along the boundary 45 of the rotating part 40. The surfaces may, for example, be relatively rough to constrain sliding therebetween.

The SMA wires 30 are connected at one end to the movable part 20 by respective connection elements 33a and at the other end to the support structure 10 by connection elements 33b. The connection elements 33a, 33b crimp the SMA wire 30 to hold it mechanically, optionally strengthened by the use of adhesive. The connection elements 33a, 33b also provide an electrical connection to the SMA wires 30. The connection elements 33a, 33b may, for example, be crimping members. However, any other suitable means for connecting the SMA wires 30 may alternatively be used.

Optionally, the arrangement shown in Figure 2 could be driven using a crank mechanism. Figure 3A is a schematic view of part of a peristaltic pump 2 that may use a crank mechanism. Optionally, the movable part 20 is coupled to the rotating part 40 via a crank mechanism. The one or more SMA wires 30 may be arranged, on contraction, to move the movable part 20, such that the crank mechanism drives continuous rotation of the rotating part 40 about the rotation axis R, thereby driving the compressor part 21 over the continuous range relative to the flexible conduit 27. Figure 3A shows a schematic diagram of an SMA actuator assembly for directly driving a movable part 20 which is a drive spindle. The peristaltic pump 2 comprises a rotating part 40 that is rotatable relative to the flexible conduit 27. The rotating part 40 has a rotation axis R about which the rotating part 40 rotates. The rotating part 40 may be a rotor or rotor disc. The peristaltic pump 2 comprises a drive spindle as the movable part 20. The drive spindle is coupled to the rotating part 40 at a position away from the rotation axis R of the rotating part 40. The SMA actuator assembly 1 comprises at least two SMA wires 30. In the example shown in Figure 3A, the actuator assembly comprises three SMA wires 30, but other embodiments may comprise only two SMA actuator wires or four or more SMA wires (see Figure 3B, for example). The at least two SMA wires 30 are each coupled at a first end to a support structure via crimps or connection components 102. The SMA wires 30 are arranged to apply, upon contraction, a force to the movable part 20 to thereby drive rotation of the rotating part 40.

The movable part 20 may be able to rotate relative to the rotating part 40, so that the SMA wire exit angle does not vary as the rotating part 40 rotates. Thus, the movable part 20 may be a pin or rod that moves as a sliding bearing within a hole in the rotating part 40. The movable part 20 must be able to transfer the force applied by the SMA wires 30 on the drive spindle to a torque applied to the rotating part 40.

In SMA actuator assembly 1, the two SMA wires 30 are directly coupled to the movable part 20. Specifically, a second end of each SMA wire 30 is coupled to the movable part 20. The second end of each SMA wire 30 may be coupled to the movable part 20 by a crimp or connection component (not shown).

When the SMA wires 30 are electrically driven, the resultant force on the movable part 20 acts as a moment that causes rotation of the movable part 20. The moment may be controlled to cause rotation of the drive spindle in any direction (i.e. clockwise or anti-clockwise). Each SMA wire 30 may be driven independently to control the position of the movable part 20, and thereby the position of the rotating part/rotor 40. If the SMA wires 30 are driven such that there is no resultant force or such that the resultant force does not create a moment, then the movable part 20 will be stationary.

The SMA actuator assembly 1 may comprise a bearing (not shown) to constrain motion of the rotating part to rotation only. The bearing may be provided between the rotating part 40 and a support structure.

In the example SMA actuator assembly 1 of Figure 3A, the first end of each SMA wire 30 is spaced from the other two SMA actuator wires. Preferably, the first end of each SMA wire 30 may be equidistantly spaced from the other two SMA actuator wires. However, equidistant spacing is not essential for the operation of the SMA actuator assembly 1, as other techniques may be used to compensate for non- equidistant spacing (e.g. by applying a different drive voltage to each SMA actuator wire).

Figure 3B shows a further embodiment of an actuator assembly for directly driving a movable part 20. The Figure 3B embodiment uses a different arrangement of SMA wires (as compared to that in Figure 3A), namely that employed in the embodiment of Figure 1. The embodiment shown in Figure 3B has a number of features in common with the embodiment shown in Figure 3A and only the differences are described here.

In the embodiment of Figure 3B, the actuator assembly 2 comprises a total of four SMA wires 30. The four SMA wires 30 are each connected between the support structure 10 and the movable part 20. Each of the SMA wires 30 is connected at one end to the support structure 10 by crimps/connection elements 102 and at the other end to the movable part 20 by crimps/connection elements 120. Each of the SMA wires 30 is held in tension, thereby applying a force between the movable part 20 and the support structure in a direction in the plane of movement of the movable part 20. In operation, the SMA wires 30 move the movable part 20 relative to the support structure in two orthogonal directions in the x-y plane.

The SMA wires 30 each extend perpendicular to the z axis. In this arrangement, the SMA wires 30 extend in a common plane which is advantageous in minimising the size of the SMA actuator assembly along the z axis.

Each of the SMA wires 30 is arranged along one side of the movable part 20. Thus, the four SMA wires 30 may consist of two pairs of SMA wires arranged on opposite sides of the movable part 20. One pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a first direction in the plane, and the other pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a second direction in the plane transverse to the first direction. Movement in directions other than parallel to the SMA wires 30 may be driven by a combination of actuation of these pairs of the SMA wires 30 to provide a linear combination of movement in the transverse directions. Another way to view this movement is that simultaneous contraction of any pair of the SMA wires 30 that are adjacent each other in the loop will drive movement of the movable part 20 in a direction bisecting those two of the SMA wires 30.

The actuator assembly 2 comprises a drive spindle 126. The drive spindle 126 is integral with (i.e. is part of) the movable part 20. In other embodiments the drive spindle 126 is connected to the movable part 20. In either case, the drive spindle extends through a hole 124 in the rotating part 40 located at a position away from the axis of rotation of the rotating part 40 (indicated by 'R'). Accordingly, movement of the movable part 20 in a cyclical path drives rotation of the rotating part 40.

Alternatively, in some embodiments, the drive spindle may be integral with or connected to the rotating part 40 and may extend through a hole in the movable part 20.

In any embodiment in which a drive spindle is employed (e.g. those shown in and described with reference to Figures 3A and 3B, the rotating part 40 may drive movement of any type of compressor part 21. The rotating part 40 may be connected to or integral with a plurality of compressor parts, for example as shown in Figures 2, 4 or 6, or a single, large roller, e.g. as shown in Figure 5.

Figure 4 is a schematic view of part of a peristaltic pump 2. As shown in Figure 4, the compressor parts 21 may be formed as part of a central region. The central region may be connected to the movable part 20 of an SMA actuator assembly 1. This may allow the central region to be moved along a path without necessarily requiring it to be rotated. For example, the compressor parts 21 may be moved in a circular manner by the SMA actuator assembly 1 without being rotated.

The fluid to be pumped by the peristaltic pump 2 may be contained within the flexible conduit 27. In the arrangement shown in Figure 4, the fluid is, in use, pumped in a clockwise direction by the movement of the compressor parts 21. In the view shown in Figure 4, there is a region of conduit compression towards the bottom-right corner of the drawing. The region of conduit compression moves in a clockwise direction. The movement of the conduit compression is caused by the compressor parts 21 impinging on the flexible conduit 27. The movement of the conduit compression pumps the fluid through the flexible conduit 27. The movement of the movable part 20 may be translated directly to movement of the compressor parts 21. Optionally, the compressor part 21 is arranged relative to the movable part 20 such that a position of the compressor part 21 in the plane is determined by a position of the movable part 20 in the plane, whereby movement of the movable part in the plane drives the compressor part 21 over the continuous range relative to the flexible conduit 27. The accuracy with which the movable part 20 may be moved by the one or more SMA wires 30 leads to accurate movement of the compressor part 21 relative to the flexible conduit 27.

As indicated by Figure 4, optionally the one or more SMA wires 30 are arranged, on contraction, to move the movable part 20 along a cyclical path in the plane. For example, in the arrangement shown in Figure 4, the cyclical path is substantially circular. However, it is not essential for the cyclical path to be circular. Alternatively, the path may be elliptical, for example. It may be desirable for the cyclical path to be formed of curves rather than have sharp corners. As explained above, it is not essential for the rotating part 40 to be provided. However, rotational movement may be combined with cyclical movement of the compressor part 21. Optionally, the compressor part 21 is arranged relative to the movable part 20 such that a rotational position of the compressor part 21 relative to the flexible conduit 27 is determined by a rotational position of the movable part 20 relative to the flexible conduit 27. There may be a direct link between the rotational position of the compressor part 21 and the movable part 20. The movable part 20 may be rotated by contraction of the one or more SMA wires 30. This may lead to rotational driving of the compressor part 21.

Optionally, the peristaltic pump 2 may comprise a plurality of SMA actuator assemblies 1. For example, the peristaltic pump 2 may comprise a further SMA actuator assembly 1 comprising a further movable part 20 arranged to move in a plane, and one or more further SMA wires 30 configured, on contraction, to move the further movable part 20 in the plane so as to drive a compressor part 21 over a continuous range relative to the flexible conduit 27. By providing a further SMA actuator assembly 1, the force imparted to the compressor part 21 may be increased.

The further SMA actuator assembly may be of the same type as the first SMA actuator assembly 1. For example, they may both relate to rotary actuators. Alternatively, different types of SMA actuator assembly may be combined in the same peristaltic pump 2.

Optionally, the compressor part 21 is sandwiched between the movable part 20 and the further movable part. Additionally or alternatively, the compressor part 21 may be sandwiched between the rotating part 40 and a further rotating part of the further SMA actuator assembly.

Figure 6 is a schematic view of a peristaltic pump 2. One SMA actuator assembly comprises a plurality of compressor parts 21 that are secured to, or are integral with, the rotating part 40. Optionally, the peristaltic pump 2 comprises a further SMA actuator assembly with a further rotating part. The further rotating part is not shown in Figure 6 because Figure 6 is a cross-sectional view of the peristaltic pump 2. The further SMA actuator assembly may comprise further compressor parts 51. The further compressor parts 51 may have a similar design to the compressor parts 21 secured to the rotating part 40. The compressor parts 21, 51 are sandwiched between the rotating parts 40 of the SMA actuator assemblies. This may help to increase the force and efficiency.

As shown in Figure 6, optionally the compressor parts 21, 51 are formed as splines 34, 54. These are described in more detail elsewhere with reference to Figure 4. As shown in Figure 6, optionally the rotating parts 40 are offset relative to each other. The rotating parts may rotate eccentrically. In the view shown in Figure 6, the rotating part 40 and its associated compressor parts 21 are positioned slightly rightward of the further rotating part and its associated further compressor parts 51 of the further SMA actuator assembly. Optionally, the movable part and the further movable part are configured to be moved out of phase of each other. Optionally, the rotating parts 40 are configured to rotate out of phase of each other. For example, the two actuators may be driven at 180 degrees out of phase. This may help to reduce radial forces on the axis.

Optionally, the peristaltic pump 2 comprises a further SMA actuator assembly 1 comprising one or more SMA wires 30 configured, on contraction, to cause one or more of the compressor parts 21 to be driven over the continuous range relative to the flexible conduit 27. As shown in Figure 4, for example, a plurality of compressor parts 21 may be provided. Additionally or alternatively, a plurality of central regions, each comprising one or more compressor parts 21 may be provided. Two or more central regions may be driven by different SMA actuator assemblies. For example, different actuators may operate out of phase of each other so that different central regions having different compressor parts may be driven out of phase with each other. This may allow a second region of compression of the tubes to be provided. The arrangement shown in Figure 6 has two sets of compressor parts 21, 51 that are driven out of phase of each other. This may lead to a plurality of regions of conduit compression.

As shown in Figures 2 and 4, for example, optionally the peristaltic pump 2 comprises a housing 26. The flexible conduit 27 may be fitted in the housing 26. The housing 26 may be referred to as a casing, or a guide. The flexible conduit 27 is positioned between the compressor parts 21 and the housing 26. Optionally, a surface of the flexible conduit 27 is in contact with a surface of the housing 26. The housing 26 may help to maintain the shape of the flexible conduit 27.

Optionally, a further SMA actuator assembly is provided. The further SMA actuator assembly may comprise a plurality of SMA wires configured, on contraction, to cause the housing 26 to be driven relative to the compressor part 21. For example, one SMA actuator may move the central region with its associated compressor parts 21 and a second actuator may be configured to move the housing 26. Optionally, the housing 26 may be moved in the opposite direction to the compressor parts 21. This may help to increase the amplitude of compression of the flexible conduit 27.

As shown in Figure 4, optionally the compressor part 21 comprises one or more flexible members 34 arranged to be capable of flexing tangentially when compressing the flexible conduit 27. This may help to reduce rubbing (e.g. friction) between the flexible conduit 27 and the compressor part 21 during motion. However, it is not essential for the compressor part 21 to comprise one or more flexible members 34. Optionally, the compressor part comprises a wiper or a roller. For example, the arrangement shown in Figure 2 has compressor parts 21 that are rollers. Optionally, the rollers are configured to rotate about a respective spindle 25. This may help to reduce undesirable forces on the compressor parts 21 from the flexible conduit 27 and/or the housing 26. The spindles 25 may be attached to the rotating part 40.

Figure 5 is a schematic view of a peristaltic pump 2. Figure 5 schematically depicts an arrangement which uses a large roller as the compressor part 21 mounted on a lever arm which is driven by an SMA actuator. The compressor part 21 is configured to rotate as its centre is moved in a cyclical (e.g. circular) path. The compressor part 21 is arranged to rotate relative to the movable part 20.

As shown in Figure 5, optionally the peristaltic pump 2 comprises a positional guide 48 configured to constrain the position of the movable part 20 in the plane so as to hold the compressor part 21 in compression against the flexible conduit 27. The positional guide may comprise a lever arm. The lever arm constrains the movement of the movable part 20 relative to the fixed pivot 47. The fixed pivot 47 may have a fixed position relative to the housing 26. The fixed pivot 47 may be at the centre of the cyclical path of the movable part 20. The movable part 20 is moved by the one or more SMA wires 30 of the SMA actuator assembly 1. The positional guide 48 may comprise an arm pivoted on the pivot 47 and configured to hold the movable part 20 a predetermined distance from the pivot 47. Any suitable SMA actuator may be used to move the movable part 20. For example, the actuator shown in and described with reference to Figure 1 may be used. In another example, the actuator arrangement shown in Figure 3A or Figure 3B may be used.

Optionally, the one or more SMA wires 30 are arranged, on contraction, to move the movable part 20 over the continuous range relative to the flexible conduit 27 while substantially maintaining a rotational position of the movable part relative to the flexible conduit 27. The movable part 20 itself may not be required to rotate. The compressor part 21 may be configured to rotate relative to the movable part 20.

Optionally, the peristaltic pump 2 comprises a one-way clutch. The one-way clutch is configured to prevent a direction in which the compressor part 21 is driven relative to the flexible conduit 27 from being reversed. For example, the one-way clutch may be configured to prevent back pressure reversing the pump if the pump is depowered.

Additionally or alternatively, the peristaltic pump 2 may comprise a brake configured to controllably prevent the compressor part 21 from being driven relative to the flexible conduit 27. The brake may be configured to prevent movement in either direction when the peristaltic pump 2 is powered off. Optionally, the brake is an active brake. The brake may be controlled by a user. Alternatively, the brake may be a passive brake. The brake may be a zero-hold power brake. This may help to improve the safety of a device for delivery of a fluid such as a drug (e.g. insulin).

Optionally, the housing 26 provides a constraint for the rotating part 40 within the X-Y plane. This may help to reduce the number of parts of the peristaltic pump 2. In particular, it may not be necessary to provide a separate component dedicated to the function of constraining the movement of the rotating part 40 within the X-Y plane. The housing 26 may help to ensure good compression of the flexible conduit 27.

Figure 7 is a schematic view of a flexible conduit 27. The flexible conduit 27 may comprise two layers 71, 72. The layers 71, 72 may define a lumen (or channel) 73 between them.

Figure 8 is a schematic view of the flexible conduit 27 when it is collapsed. As shown in Figure 8, the layers 71, 72 are arranged to collapse flat against each other, thereby closing the channel 73, when the flexible conduit 27 is compressed. By providing that the flexible conduit 27 is formed from two layers 71, 72 as shown in Figures 7 and 8, the amount of force and/or displacement required to collapse (e.g. seal) the flexible conduit 27 by the compressor part 21 may be reduced. The flexible conduit 27 may seal more easily under action from the compressor part 21 (e.g. a roller).

As shown in Figure 7, optionally the layers 71, 72 are secured to each other at opposing edges 74 so as to define the channel 73 between the layers 71,72. For example, the layers 71, 72 may be adhered to each other, or otherwise bonded to each other.

Optionally, one layer 71 of the flexible conduit 27 is connected to the compressor part 21. Additionally or alternatively, the other layer 72 of the flexible conduit 27 may be connected to a component that has a fixed position relative to the flexible conduit 27. For example, the other layer 72 could be connected to the housing 26. This may help to ensure that the flexible conduit 27 opens when no longer compressed by the compressor part 21. As the compressor part 21 moves away from the surface of the housing 26, the flexible conduit 27 may be opened up so that fluid can continue to be transported through the channel 73.

A further embodiment of a flexible conduit 27 is illustrated in Figure 9. The flexible conduit 27 is made of a single piece of material (i.e. it does not comprise two layers, as in the embodiment shown in Figure 7 and 8) but comprises two fold lines 75 and 76. For example, the conduit 27 may initially be a tube of circular or oval cross-section and the fold lines 75 and 76 may be achieved via a creep process, e.g. using high temperature and/or pressure. The fold lines 75 and 76 mean that the conduit 27 may seal more easily under action from the compressor part (e.g. a roller). The direction of action of the compressor part is shown by arrow 77.

Optionally, the peristaltic pump 2 comprises a controller configured to determine a measure of an electrical characteristic of the one or more SMA wires 30, and determine a position of the movable part 20 based on the measure of the electrical characteristic. For example, the controller may be configured to measure or determine a measure of a resistance (electrical resistance) of the one or more SMA wires 30. The controller may be configured to determine the position of the movable part 20 based on the measured resistance or determined measure of resistance. The controller may be configured to control the position of the movable part 20 based on the determined position of the movable part 20 and its target position or movement.

The peristaltic pump 2 may be embodied within a fluid delivery device. The flexible conduit 27 may be configured to hold the fluid to be delivered. The fluid to be delivered may be a drug. For example, the fluid to be delivered may be an insulin. The peristaltic pump 2 may be used as an insulin pump.

Optionally the SMA actuator assembly 1 comprises a total of four SMA wires 30, as shown in Figure l.Such an SMA actuator assembly 1 may be used to drive the movable part 20 shown in Figure 1, the compressor parts 21 of the arrangement shown in Figure 4, the movable part 20 shown in Figure 3A or 3B, the housing 26 of any of the arrangements described in this document or the movable part 20 of the arrangement shown in Figure 5, for example.

The four SMA wires 30 may be connected between a support structure 10 and the movable part 20. Each of the SMA wires 30 is held in tension, thereby applying a force between the movable part 20 and the support structure in a direction in the plane of movement of the movable part 20. In operation, the SMA wires 30 move the movable part 20 relative to the support structure in two orthogonal directions (x and y, as shown in Figure 1) in the plane.

The SMA wires 30 each extend perpendicular to the z axis. In this arrangement, the SMA wires 30 extend in a common plane which is advantageous in minimising the size of the SMA actuator assembly along the z axis.

Each of the SMA wires 30 is arranged along one side of the movable part 20. Thus, the four SMA wires 30 may consist of two pairs of SMA wires arranged on opposite sides of the movable part 20. One pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a first direction in the plane, and the other pair of SMA wires are capable on selective driving to move the movable part 20 relative to the support structure in a second direction in the plane transverse to the first direction. Movement in directions other than parallel to the SMA wires 30 may be driven by a combination of actuation of these pairs of the SMA wires 30 to provide a linear combination of movement in the transverse directions. Another way to view this movement is that simultaneous contraction of any pair of the SMA wires 30 that are adjacent each other in the loop will drive movement of the movable part 20 in a direction bisecting those two of the SMA wires 30.

With reference to Figure 10A-E a peristaltic pump 2 is described. Figure 10A is a plan view of the pump 2 with various components of the pump visible (some translucent for clarity of other components). Figure 10B shows one layer of the pump 2 and Figure 10C is a perspective view of the pump 2. Figure 10D is a cross-sectional view of a portion of the pump 2. Figure 10E is an exploded view of the pump 2.

With reference to Figures 10A, 10E and 10D, a peristaltic pump 2 is described. The peristaltic pump 2 is configured to pump a fluid. The peristaltic pump 2 comprises a flexible conduit 27 which is for containing a fluid. The flexible conduit 27 is made up of a solid base portion 52 comprising a groove 54, which forms a lower surface of the conduit 27, and a flexible membrane 56 adhered to the base portion (see Figures 10D and 10E). The flexible membrane forms an upper surface of the flexible conduit 27.

The peristaltic pump 2 comprises a plurality of compressor parts 21. The compressor parts are ball bearings and are configured compress the flexible conduit 27 as the compressor part 21 moves relative to the flexible conduit 27. Specifically, the ball bearings deform the flexible membrane 56 and are pushed into the groove 54 by a pressure plate 94, shown in Figure 10E, (which imparts a force on the ball bearings in the z direction - see axis labels in Figure 10A- as shown by arrow D in Figure 10D). The pressure plate may be a solid disc, or may feature a series of deformable leaves, that ensure each compressor part 21 is subject to its own independent force. The compressor part 21 may comprise elements other than a ball bearings, for example a wiper or a roller.

The pump 2 further comprises a constraining element 58 which is a disc comprising a plurality of slots 60. The slots 60 are equally angularly spaced about axis R (see Figure 10A) and extend in radial directions. A compressor part 21 (i.e. a ball bearing) sits in each slot 60. The slots 60 constrain the compressor parts to a fixed respective angular position (with respect to the constraining component 58) but allow the compressor parts 21 to move in a radial direction (with respect to the axis of rotation), along the slot. The pump 2 further comprises an actuator assembly (not shown in Figures 10A-D) which drives rotation of constraining element 58, which in turn drives rotation of the compressor parts 21, about an axis of rotation R and along the groove 54 (and hence along the flexible conduit 27). The compressor parts may be driven along the conduit by rotation of the pressure plate, constraining component or both. The actuator assembly may comprise any drive system, for example SMA, SMA elements indexing the rotor, an SMA rotary actuator, a conventional motor with feed forward or feedback control, Piezo indexing, and/or solenoid indexing.

The flexible conduit 27 comprises various regions as follow:

(1) A first region 62 (indicated by the dashed line labelled 62 in Figure 10A).

(2) A second region 64 (indicated by the dashed line labelled 64 in Figure 10A).

(3) A first transition region 66 (indicated by the dashed line labelled 66 in Figure 10A) and

(4) A second transition region 68 (indicated by the dashed line labelled 68 in Figure 10A).

The flexible conduit 27 comprises an inlet 70 and an outlet 72. The inlet 70 is in fluidic communication with an inlet conduit 70a (see Figure 10B), which in turn is connected to a fluid reservoir (not shown). The inlet 70 is disposed on the first transition region 66. The outlet 72 is in fluidic communication with an outlet conduit 72a, which in turn is connected to a fluid dispensing mechanism (e.g. a cannula) or other downstream fluid handling structure. The outlet 72 is disposed on the second transition region 68.

The first region 62 of the flexible conduit has an arc shape with a constant radius Ri (i.e. constant distance to the axis R). The second region 64 of the flexible conduit has an arc shape and also has a constant radius R2 (i.e. a constant distance to the axis R). R2 is greater than Ri.

The distance of the first transition region 66 from the axis R varies along the length of the first transition region. Similarly, the distance of the second transition region 68 from the axis R varies along the length of the second transition region. The first transition region 66 connects a first end of the first region to a second end of the second region. The second transition region connects a first end of the second region to a second end of the first region.

The first and second transition regions each comprises a further groove 104 and 82 (respectively), within the groove 54. In this way, the first and second transition regions are deeper than the first and second regions 62 and 64. This has the effect that the compressor parts 21 do not fully compress the flexible conduit 27 in the first and second transition regions. Instead, the first and second transitions regions contain a single, contiguous volume of fluid despite the presence of the compressor parts 21.

Figure 10D shows a cross-section of the conduit 27. In the upper figure, the conduit is in an uncompressed state. In the lower figure, the compressor part 21 deforms the membrane 56 into the groove 54. Figure 10E is an exploded view of the components of the pump 2. The components are biased together by spring 100, which is compressed by an outer pump casing or some other support structure (not shown).

Operation of the pump 2 will now be described. As mentioned above, the pressure plate 94 acts to push the compressor parts 21 into the groove 54. The actuator assembly (also not shown) drives rotation of the compressor parts 21 by rotating the constraining component 58.

As the constraining component 58 rotates, the ball bearings are driven along the flexible conduit 27. The distance of the conduit 27 from the axis R varies along the length of the conduit but the ball bearings (i.e. the compressor parts 21) are free to move along slots 60 and so this variation of distance is accommodated by the slots and the ball bearings remain in the groove 54.

Motion of the compressor parts 21 along the first region and the second region will be described first but it will of course be appreciated that the compressor parts move around the circuit of the conduit 27 in sequence (e.g. the first region, the first transition region 66, the second region 64 and the second transition region 68).

In the first region 62 of the flexible conduit 27, the compressor parts 21 compress the conduit 27 fully and the fluid in the first region 62 is split into separate volumes which are not in communication with each other. This compression of the conduit 27 drives displacement of the fluid in the conduit along the conduit.

In the second region 64 of the conduit 27 the compressor parts 21 also compress the conduit 27 fully and the fluid in the second region 64 is split into separate volumes which are not in communication with each other. This compression of the conduit 27 drives displacement of the fluid in the conduit along the conduit 27.

As mentioned above, the radius of the second region 64, R2, is greater than the radius of the first region 62, Ri. Since the compressor parts 21 are equally angularly spaced about the axis R, a greater volume of fluid is trapped between two adjacent compressor parts in the second region 64 (e.g. compressor parts 21b and 21e) than is trapped between two adjacent compressor parts in the first region 62. The compressor parts 21 all move at the same angular rate (because they are all driven by the constraining element). Due to this and the difference in volumes trapped in the first and second regions, there is a greater flow rate of liquid in the second region 64 than in the first region 62. Accordingly, more liquid is being pushed into the second transition region 68 (as it leaves the second region 64) than is being allowed to leave the second transition region 68 via the first region 62. Accordingly, there is a well- defined volume of liquid V which is forced out of the second transition region 68 via outlet 72. Volume V is equal to a difference between (i) the total volume of liquid trapped in the second region 64 and (ii) the total volume of liquid trapped in the first region 62. Similarly, the same volume of liquid (V) is drawn into the first transition region 66 via the inlet 70. In this way, liquid is pumped around the conduit 72 and periodically, a well-defined volume of liquid (V) is dispensed out of outlet 72.

As described above, the first and second transition regions are deeper than the first and second regions 62 and 64. This has the effect that the compressor parts 21 do not fully compress the flexible conduit 27 in the first and second transition regions. Instead, the first and second transitions regions contain a single, contiguous volume of fluid despite the presence of the compressor parts 21. Accordingly, liquid is drawn into the first transition region 66 via the inlet 70 and is able to move through the first transition region 66 despite the presence of the compressor parts 21 (since they do not fully compress the conduit 27 in the first transition region). Similarly, liquid in the second transition region 68 is forced out of the outlet 72 but movement of this liquid through the second transition region is not prevented by the compressor parts 21.

The volume V which is dispensed by the pump 2 is well-defined and can be controlled particularly precisely for two reasons. Firstly, there is no 'ramp on' or 'ramp off' events (in which a compressor part moves off of the conduit and releases it from a compressed state, as in previous peristaltic pumps). Secondly, because it is a difference between volumes (i) and (ii) (described above) which is expelled, the pump can be configured so as to make this difference particularly small. Accordingly, for a given rotation of the compressor parts, a very small volume can be dispensed. By controlling the rotation of the compressor parts very accurately itself, the dispense volume can be made to be even more precise and accurate.

A further embodiment of the pump 2 is described with reference to Figure 11. The pump 2 largely operates in the same way as that described with reference to Figures 10A-D and so only the differences will be described here.

With reference to Figure 11, the conduit 27 is circular and offset from the axis of rotation R. The slots 60 in the constraining component 58 are also non-linear and instead have a curved profile. This means that as the compressor parts 21 change in radial distance from the axis R they are also caused to change in angular position around the axis R relative to the constraining component 58. This configuration provides another way of maintaining a constant volume between adjacent compressor parts 21 over two regions of the device (which correspond to the first and second regions 62 and 64 described with reference to Figures 10A-D) when the radial distance of those regions from the axis R is not constant over those regions.

Embodiments described above comprise a solid base with a groove and a flat, flexible membrane on top to create the conduit 27. An alternative arrangement of the pump comprises a flat, solid base with a profiled membrane on top to create the conduit.

With reference to Figure 12, the pump 2 may comprise a solid, flat base portion 52 and a profiled, flexible membrane 56 adhered to the base portion 52. The profile of the membrane 56 creates the conduit 27. In a further variation, the base portion 52 may comprise a groove (as in Figure 10A, for example) and the membrane 56 may also have a raised profile which is aligned with the groove.

In configurations in which the membrane 56 comprises a raised profile, the compressor parts 21 may comprise elongate components, as illustrated in Figure 12. For example, the constraining component 58 of the Figures 10A-D embodiment may be dispensed with and instead, the pressure plate (94) may comprise elongate protrusions which are arranged radially (i.e. each parallel to a radial direction with respect to the axis R) and are equally angularly spaced. Alternatively, as illustrated in Figure 12, the compressor parts 21 may each comprise an elongate (e.g. cylindrical) roller) which are driven to rotate about the axis of rotation R but which are also free to rotate about their own longitudinal axis (labelled 78 in Figure 12).

With reference to Figure 13, an alternative arrangement is described. The pump 2 may comprise a solid base portion 52. On top of the base portion 52 is disposed a tube 81 surrounded on top by a membrane 80a and underneath by a second membrane 80b. The tube may be a pre-made flexible tube. The upper portion (comprising the tube and the membranes) is then adhered to the base portion 52.

With reference to Figure 14A, a further embodiment is described. The pump 2 may comprises a solid base portion 52 which comprises a groove. A bottom surface of the groove may be the same height (i.e. the same position along the axis of rotation) along the whole conduit 27 but an upper surface of the base portion 52 may have a varying height. In this way, a conduit 27 with varying depth (i.e. extent along the axis of rotation) is created.

In a further embodiment shown in Figure 14B, a height (i.e. position along the axis R) of the lower surface of the groove is varied along the length of the conduit. This requires the pressure plate to accommodate movement of the compressor parts 21 in directions parallel to the axis of rotation R but allows the membrane 56 to lie in a single plane, which may be valuable in the manufacturing process. A combination of the two approaches shown in Figure 14A and 14B may also be used.

The various regions of the conduit may be configured to have different depths. The first region may have a first depth DI and the second region may have a second depth D2. DI and D2 may be constant along their respective regions. D2 may be greater than DI. In this way, a difference in flow rates between the two regions may be provided by controlling the depth of the conduit (or the cross-sectional area more generally) in those regions. The pump would be configured such that the conduit is still compressed fully in the first and second regions but not in the first and second transition regions. This requires the pressure plate to accommodate the balls being displaced up and down, but allows the membrane to be a simple plane which may be valuable to certain manufacturing processes.

This could be used as an alternative to or an addition to varying the radius of the conduit in order to achieve the difference in flow rates in the first and second regions which drives the flow and dispensing of the fluid.

With reference to Figure 15, in certain regions of the conduit in which it is desired that the compressor parts 21 do not separate the fluid into separate volumes which are not in fluidic communication with each other (e.g. in the first and second transition regions in the embodiment of Figures 10A-D), fluidic communication across the relevant region may be provided by multiple ports 72i and 722 (as opposed to a deeper groove 82, for example, as described with reference to Figure IOC).

In embodiments in which the membrane 56 comprises a raised profile, the volume above the membrane remains constant, whatever the angular position of the compressor parts 21. Therefore, with reference to Figure 16, in some embodiments the pump 2 may comprise a sealed volume 92. The sealed volume is contained by an outer wall 94 and the membrane 56. The sealed volume contains the pressure plate 94, the constraining element 58, a rotor shaft 90 (optionally) and the compressor parts 21. The sealed volume 92 also contains an incompressible fluid, such as oil. The oil provides resistance to any negative pressure that may develop in the region of the inlet 70 and may otherwise deflect the flexible membrane into the groove in the base portion 52. Accordingly, negative pressure is provided by the incompressible fluid which aids the decompression of the conduit 27 as the compressor parts 21 move over it. Seals are provided at the points at which the rotor 90 coincides with the outer wall 90 and the base portion 52.

The above-described SMA actuator assemblies comprise at least one SMA element. The term 'shape memory alloy (SMA) element' may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA element' may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling or deposition and/or other forming process(es). The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

It will be appreciated that there may be many other variations of the above-described examples. For example, the SMA actuator assembly 1 may comprise one single SMA wire 30 configured to move the movable part. As another example, the flexible conduit 27 may be provided as a unitary tube, rather than as a two-layer conduit as shown in Figures 7 and 8.