GB2406794A - Piezoelectric lancing device - Google Patents

Abstract

A lancing device 4 having a piezoelectric actuator mechanism 9 for driving a lance towards the skin of a patient. The lance is mounted on an actuator arm 1 that is fixed at one end and has piezoelectric Iayer(s) 7, 8 mounted on its sides. An electric field applied across the piezoelectric layers causes the arm to bend and controllably move the lance. The lancing device may be combined with a testing device.

Description

A LANCING DEVICE USING A PIEZOF,LECTRIC A('TUArfOR FIEI,D OF Till:

INVENTION The present invention relates to a lancing device for use in sampling body fluids, a method for lanchlg a patient using the lancing device and a method for making a lancing device.

BACKGROUND Of TIlE INVENTION

Samples of body fluid are commonly required for medical testing. L) iabetics, for example, must frequently take blood samples in order to measure their blood glucose level. Lancing devices provide the user with a convenient and discrete way of providing a body fluid sample. Such devices generally comprise a sharp lancing needle and a triggcrable mechanism for propelling said needle into the skin so that body fluid can flow to the surface, where a sample can be collected for testing. Body fluids to be sampled in this way include blood and interstitial fluid (ISF). The presence or concentration of other analyses or indicators such as thrombin, pharmaceuticals, glycated protein, such as HBA 1 c, haematrocrit and so on can be readily determined by the patient using such devices.

Ordinarily, the propelling mechanism is a spring cocked by means of a lever. A trigger is also provided to release the spring, driving the lancing needle into the user's skin. The depth of penetration can normally be adjusted by means of a selectively movable stop, which blocks the movement of the lancing needle once it has travelled a specified distance.

Spring-propelled lancing devices, for example the device disclosed in U.S. patent application No. 2002/0029058 Al, have several disadvantages.

al he energy delivered by spring driven lancing devices is difficult to harness in such a way as to minimise the distress of the blood sampling procedure.

The energy stored in a spring is subject to Plooke's law. When a compressed spring is released a neo ballistic acceleration of the attached mass produces a recoil when the spring is released into the housing of the lance. In addition, the end of the travel as defined by a mechanical stop generates noise and vibration. The recoil and mechanical stop in a spring l device produce vibration in the spring perpendicular to the desired path of the lancing needle. Energy in this direction (perpendicular to the lancing direction) is transferred to the needle and hence the skin of a patient, stimulating the pain receptors that populate the tissues around the sampling area.

Spring-driven lancing devices can be noisy and, since a spring releases its energy immediately on release and the energy decays according to Hooke's law, any load on the spring is put into an oscillating motion unless damped. Additionally, spring-driven lances devices are prone to vibration perpendicular to the lancing needle's desired path, which causes unnecessary pain to the user.

There exist lancing devices wherein the lancing needle is propelled and then retracted by a magnetic field. Such a device is disclosed in U.S. patent No. 6,364,889 and the electromagnetic actuator for such a device is described in International patent application No. WO 02/100460. Whereas it is possible to control the strength of the magnetic field used to drive the lancing needle, it is difficult to control accurately the position of the needle so as, for example, to retract it only partially from a wound.

Current lances devices cause undue pain to the user and can be difficult to use for users with restricted hand movement, for example sufferers from arthritis. It would clearly be desirable to find an easier and less painful manner of providing a body fluid sample.

An example of a preferred lancing device would accelerate the lancing needle rapidly into the epidermis and then decelerate, pushing the needle into body fluid-carrying capillaries.

After remaining in the wound long enough to transfer cutting action to the capillaries, the needle is removed. Since a feeling of pain can be exacerbated by factors other than penetration of the lancing needle, noise due to moving parts should be kept to a minimum.

Noise can be caused, especially in spring activated devices, by a stop to cause the lance to stop at the end of its travel. Users may tense up, particularly following priming or cocking of the lance, in anticipation of the lancing action and noise - such tensing is undesirable in a lancing action since this may exacerbate pain or the pain experienced. Reducing noise will also have the advantage of making the use of such a lancing device more discreet.

It is an object of the present invention to provide a lancing needle which overcomes, at least in part, the disadvantages ol prior art lancing devices.

SUMMARY OF Tl IE INVENTION

the present invention provides a lancing device comprising a lance and a piez.oelectric actuator mechanism tor driving said lance towards a body to be lanced.

According to a second aspect ol the invention, there is provided a method of lancing a patient which comprises: providing a lancing device comprising a lance and a piczoelectric actuator mechanism for driving said lance towards a body to be lanced; positioning the lancing device on the patient such that the lance is arranged ready to move towards the skin of a patient; and actuating the piczoelectric actuator mechanism to cause the lance to move towards the skin of a patient.

According to a third aspect of the present invention, there is provided a method of manul:acturing a lancing device which comprises connecting a lance to a piezoelectric actuator in such a manner that, on operation of the piezoclcctric actuator, the lancing needle is driven towards a body to be lanced such as to skin penetrating position optionally in a controlled or controllable manner.

OPTIONAL FEATURES AND Al)VANTAGES Optionally, the actuator mechanism comprises an actuator arm having one end fixed to the body of the lancing device and a lance is mounted on the other end of the actuator arm.

This can help reduce noise since an actuator arm, connected to a lancing device body and a lance can not only provide a lancing action but may also provide a breaking action or action limiting the travel of the lance and hence, in one possible embodiment, eliminating or reducing the requirement for a stop, or changing the effect of a stop on the operation of the dcvicc, say by reducing the speed of the lance as it approaches the stop, hence reducing noise as it hits the stop. Optionally the arm is elongated so that the arm is more flexible along its length.

The body of the device to which the actuator arm is attached may be a solid rnernber or a part of a frame supporting other parts of the device.

The lance may be a lancing needle, blade, point, sharp or other skin puncturing member as would be well understood by one skilled in the art from the information contained herein.

The actuator arm may have a single piezoelectric layer mounted on one of its sides such that, on activation ol the piezoelectric layer, the actuator arm is bent.

Optionally, there is a piezoelectric layer on each side of the actuator arm.

An actuator arm with one or more piezoelectric layers on its side(s) is known in the art as a piezoelectric bender.

In an optional embodiment, a plurality of piezoelectric layers are stacked on each side of the actuator arm, to increase the force generated at the lance. This permits the lance to be accelerated more rapidly and thus reduces the pain experienced by the user.

In another embodiment, the piezoelectric actuator mechanism comprises a plurality of piezoelectric benders, each one having its own actuator arm. The actuator arm of each device may be connected to the lancing needle, which is driven by the combined force of the piezoelectric benders.

It has been found that skin deformation has a significant effect on puncture pain. In the current state of the art devices, the lancing needle impacts the skin at a speed in excess of 2m/s. However, the required speed can vary depending upon the sharpness of the lance being used. Typically, though a minimum speed of 1.2m/s is required. In one embodiment of this invention, the lance in the lancing device travels at a speed of 1.2m/s or more.

I-Iowever, to further try and reduce the pain experienced by the user, the lancing device of the present invention is optionally adapted so that the lance is travelling at substantially more than 2 m/s when it impacts the skin, advantageously from 3 to 6 m/s.

Optionally, the device further comprises a penetration depth control, which may be set manually or automatically, to accommodate different users and enable a user to extract samples from different areas of the body. A variation in penetration depth also affects the quantity of body fluid that can be collected. Optionally, the penetration depth can be set to between 0.5mm and Smm and preferably between 0.5mm to 2mn1 of depth since this is particularly useful for blood extraction. For ISF extraction there is a depth range of around 200pm or more below the skin surface. Furthermore, optionally the device is able to reproduce a penetration depth to within 0.02mm to aid control of the depth.

Furthermore, in one embodiment the lance can be controllably driven to a certain position in a certain time within the physical limits of the device, ie the speed can be controlled, for example, by the rate and/or amount of charge imported to the piezoelectric layer.

For travel of 2mm through skin, 8mJ of kinetic energy are required to facilitate this mechanical work. Optionally, the device has a minimum power capability of 8mJ to allow a variation in depth control of up to 2mm.

After penetrating the skin, the lance can be accurately and reproducibly held in the wound for a predetermined period of time, holding the wound open and encouraging body fluid to flow to the surface. Studies have shown that most people begin to perceive the needle in their skin after 10 ms. Hence, the residence time for the needle or other lance in the wound is optionally less than this period. The present invention can optionally be used in this way.

Optionally, the lancing device includes a trigger means for activating the piezoelectric actuator mechanism. There are a number of possible trigger means for triggering the lancing operation. Each trigger means may be present alone or in combination with any other trigger means. 'I'he trigger means may be a manual switch. When the user presses this switch, the lancing device is activated. Alternatively, the manual switch may be replaced with an automatic control, for example an optical or pressure-sensitive proximity detector, a temperature sensor or a timing device. The use of a piezoelectric device typically avoids the need l'or priming the lance and a trigger alone can be used.

The lancing device may be combined with a testing device. One such embodiment comprises an integrated lancing device incorporating a lancing device and a biosensor or meter for testing an analyte, such as glucose in blood. 'I'his may be a meter for use with individual disposable test strips or a cartridge of test strips or test sensors. A piezoelectric actuator is well suited for use in such an integrated lancing device since the position of the needle can be accurately controlled. Indeed the piezoelectric activated lancing device can I O he used in such a way even if it is not connected to a meter. For example, first, the needle or other lance is rapidly driven into the skin, then it is withdrawn but held close to the wound to allow body fluid to escape and be collected by capillary action. After sufficient fluid is collected, the needle or other lance is completely withdrawn from the skin area.

Thus, the method of deployment of the needle or other lance is controllable because of the use of a piezoelectric actuator. Indeed the method of deployment of the lance may be in stages eg lance, penetration, then total or partial retraction, then total retraction or then repenetration, then total or partial retraction and so on as would be understood by someone skilled in the art from the information described herein.

L)ESCRlPTION OF THE DRAWINGS Figure I illustrates, by way of example only, an elevation view of a lancing device comprising a lancing needle driven by a piezoelectric actuator mechanism having a single activator arm and a pie;zoelectric layer on either side of the arm.

Figure 2 illustrates, by way of example only, a plan view of an alternative lancing device comprising two actuator arms interconnected with one another - each having one piezoelectric layer on opposing sides.

Figure 3 illustrates, by way of example only, an elevation view of a device of Figure I showing a bent actuator arm in dotted line (not to scale)

DETAILED DESCRIPTION OF THE INVENTION

A lancing device of the present invention is illustrated, by way of example only, in figure 1. The lancing device comprises an elongate actuator arm (1) having first (2) and second (3) ends. '['he actuator arm may be a piezoelectric bender such as that in a servocell device available from PB'I' Ltd. I Astra Centre, Edinburgh Way, l larlow, l4,ssex, CM20 2BN, I JK.

A lance, such as a lancing needle (4) is detachably mounted at said first end (2), substantially perpendicular to the actuator arm (1), by means of a mounting bracket (5).

The lance may be a lancing needle, blade, sharp or other member nor lancing skin.

Examples ol' needles include the Unilet Universal Comfort Touch available from Mumford 1,td, Oxford, UK. Examples of blades include bladed lancers such as that described in US patent applications US10/116.386. US2002/016X290, US10/226,906 Examples of other sharps include those described in patents and applications W002/49507, US5997561, WO01/72220, US patent applications US2003/0009113, US2003/0028087, US 09/923093. Information concerning such needles, blades, lancers and sharps is hereby incorporated herein from the above mentioned references.

Said second end (3) is fixed to the body (6) of the lancing device (not shown). The body (6) may be a solid member or part of a frame, for example, a frame surrounding the actuator arm. The actuator arm (1) is flexible and may bend about its second end (3) along its length in region (9). The actuator arm (1) may be plastic or metal (or any other suitable resiliently deformable material such as PTFE, steel etc. Optionally, the actuator arm is conductive or an additional conductive layer or other conductive electrode is provided as a first electrode between the actuator arm and the piezoelectric layer so as to apply potential across the piezoelectric layer. The actuator arm (1) forms part of a piezoelectric bender (10), which here also comprises two piezoelectric layers (7, 8) bonded to said actuator arm (1). The piezoelectric layers (7,8) may be piezoelectric crystal such as that found in the servocell available from PBT Ltd. Other piezoelectric materials which can be used include co-fired multilayer actuators available from TRS Ceramics Inc., 2820 FCollege Avenue, State College PA 16801 USA.

The piezoelectric layers (7,8) may be bonded to the arm (1) by adhesive such as cold cure adhesive or heat seal adhesive, or the layers be spot welded to the arm (1) to form the piezoelectric actuator mechanism, in this case a bender (10). At least one second electrode, for example, in the form of a conductive layer is applied to the upper surface of the piezoelectric layer to allow a potential to be applied across the piezoelectric layer.

Whilst not intended to be limiting, the following explanation is thought to be how the device works. On application ol a potential across the piezoelectric layer, from one surface to another, it thickens causing retraction in the plane of the layer. Since the underlying activator arm is fixedly attached to the layer but is not affected by the applied potential, the arm bends in a direction towards the piezoelectric layer, Release of the potential, allows the arm to resume its original position. A second layer on the reverse of the arm can be used to send the arm in a like manner in the opposite direction.

In the embodiment illustrated in figure 1, the actuator arm (1) is substantially flat and piezoelectric layers (7, 8) are attached to either side. The actuator arm (1) can be bent up or down by applying electric fields across the two piezoelectric layers (7, 8). For example, such fields can be applied as described in patent application W003/003479 to PBT (IP) Ltd. The first end (2) of the actuator arm (1) bends about the second end (3) in an arc.

However, since the length of the arc described by the first end (2) is small relative its radius, the motion of the first end (2), and therefore also of the lancing needle (4), is approximately linear in a direction towards the skin of a patient, say. Typically, this direction will be approximately perpendicular to the skin surface.

A further example is shown in Figure 2 in which a frame 102 provides a fixing point 101 for arms 110 and 111. Arm 110 has a piezoelectric layer 107 on its upper surface when viewed in figure 2. Arm 104 has a piezoelectric layer on its rear surface when viewed in figure 2.

Arm 110is fixed atpoint 101 tofrarne 102. The distalendof arm 110 relative to point 101 is connected to cross arm 106 which is free to move. One end of arm 111 is connected to cross arm 106 and therefore moves with cross arm 106. In addition, the distal end of arm 111, relative to cross arm 106, is free to move relative to the fixed end of arm 111 to cross arm 106. A lances 109 is fixed by adhesive, spot welding or comolding to the distal end of arm 11. Optionally the lances 109 is removably connected to arm 111 for example by means of co- operating snap-fit features on lances 1 ()9 and arm I I I (not shown).

Frame 102 is electrically insulating. Connection points 103 and 108 are in the Dorm of conductive pins passing from one side to the other of frame 102. Frame 102 supports two electrically conductive steel arms 110 and 111. 'The arms are resiliently connected to one another via steel cross arm 106. Arm 110 is connected to the frame by a rivet at connection point 101. A flying lead in the form of a piece of wire 112 or a PCH track (not shown) connects pin 103 to electrically conductive arm 110. Thus arm 110 provides a negative connection to piezoelectric layer 104 immediately adjacent arm 110. A second flying lead in the form of a wire 113 provides a positive electrical connection to the outermost face of piezoelectric layer 104 by means of an electrode situated on the outermost face of electrode 104 (not shown). Thus piezoelectric layer 104 is sandwiched between a negative and positive electrical connection when the power is switched on.

An insulated electrical connector 105 connects the outermost surl:ace ol piezoelectric layer 104 to the outermost surl'ace of piezoelectric layer 107 at connection points 105A and 105B respectively. Thus electrically insulated conductor 105 bends around the edge of arm 110. Thus, a positive electrical connection is provided to the outermost surface of piezoelectric layer 107 via pin 108, wire 113, electrode layer on the outermost surface of piezoelectric layer 104, connection point 105A and electrically insulated conductor 105 and connection point 105B. Electrically insulated conductor 105 may be a metal wire with a plastic coating. The electrically conductive arms 110 and I 11 provide via cross electrically conductive cross arm 106, a negative electrical connection to the rear of piezoelectric layer 107. A lances 109 is positioned at the distal end of arm 111.

When power is applied a negative potential is applied to the innermost surface of piezoelectric layer 104 immediately adjacent arm 110 and likewise to the innermost surface of piezoelectric layer 107 immediately adjacent arm 111. A positive potential is applied to the outermost surface of piezoelectric layer 107. Thus, arm 110 will bend downwards into the plane of the paper about point 101 and force cross arm 106 downwards with respect to frame 102. Thus the end of arm 111 adjacent cross arm 106 will be moved downwards with respect to the plane of frame 102. In contrast arm 111 and in particular the frcc-end thereof adjacent removable, disposable lances 109 will bend upwards out of the plane of the paper, moving lances 109 towards a lancing site on a patient. Thus, any number of piezoelectric arms or actuators can be combined in this or other ways to produce greater precision or degree of movement or speed of movement of lances 109 towards a particular lancing site as will be understood by someone skilled in the art Prom the information contained herein.

Figure 3 shows an arm (1), with the first end 2 free to move about a second end 3 Axed to an anchor point (6) in a region 9. Two piezoelectric layers (7 and 8) are positioned either side of electrically conductive arm (1). Piezoelectric layers (7 and 8) each have an electrically conductive electrode 100 and 101 respectively positioned adjacent to the outermost surfaces so as to be able to apply positive potential to the piezoelectric layers.

The electrically conductive centrally located arm (1) conducts a negative potential to piezoelectric layers (7 and 8). When power is applied to layer 8 and arm 1, the arm moves in the direction of' arrow 200. The distance moved in the y- direction is Y and the distance moved in the xdirection is X, the angle moved being a. Because the distance Y is likely to lie in the range 2-3 mm and the arm may be several tens of mm in length, the distance X is relatively small ie the sideways travel may be negligible. Therefore, whilst the tip of the needle 4 actually traverses an arc, its movement can be approximated as linear. Typically, the movement is in a direction towards the body of a patient, for example the movement may be approximately perpendicular to the body to be lanced. Typically a range of +20 or -20 to the perpendicular is envisaged, although an optional range for more controlled performance is +10 or -10 from the perpendicular to the skin of a user. When power is applied to layer 7 and removed from layer 8, the arm is bent downwards within the plane of the paper in the direction of arrow 300. Thus the arm 1 and attached needle 4 can be moved in a reciprocal manner, either once or repeatedly depending upon the type of lancing action required to minimise pain and/or noise; and/or maximise blood/lSF volume of the sample produced.

Thus, in this particular embodiment a bender (10) is provided having two piezoelectric layers, one on either side of a single arm (1). Additional piezoelectric layers, or combinations of arm (1) and piezoelectric layers can be envisaged from the information contained herein which enhance the amount of movement Y or the speed with which Y is traversed or the degree of control over which the final position of the needle tip can be determined.

The present invention has been described above by way of example only. However, it should not be construed as being limited to the specific details described with reference to the drawing. Rather, the spirit and scope of the present invention is defined in the appended claims. i}

Claims (20)

1. A lancing device comprising a lance (4) and a piezoelectric actuator mechanism for driving said lance towards a body to be lanced.

2. A lancing device according to claim 1, wherein said piez.oelectric actuator mechanism comprises an elongate actuator arm having one end fixed to the lancing device and the lance is mounted on the other end of the actuator arm.

3. The lancing device ol'claim 2, wherein there is a single piezoelectric layer mounted on one side of the actuator arm

4. The lancing device of claim 2, wherein there is a piezoelectric layer mounted on each side of the actuator arm.

S. The lancing device ol' claim 3 or 4, wherein there is a plurality of piezoelectric layers.

6. The lancing device of claim 1, comprising a plurality of piezoelectric benders wherein the free end ol the actuator arm in each piezoelectric bender is connected to the lance or wherein the free end of one or more actuator arms are connected to one or more actuator arms, the free end of which is connected to the lance.

7. A lancing device according to any preceding claim, wherein the lance is travelling at more than 1.2 m/s and, optionally at substantially more than 2 m/s when it impacts the skin.

8. A lancing device according to claim 7, wherein the lance is travelling at between 3 and 6 m/s when it impacts the skin.

9. A lancing device according to any preceding claim, wherein the penetration depth of the lance is adjustable between O.Smrn and Smm or between O.Smm and 2mm or between 20O'lm and above. iS

10. A lancing device according to any preceding claim, wherein said lance penetrates the skin to within 0.02 mm of the desired depth.

11. A lancing device according to any preceding claim wherein the lance is held in the wound for a predetermined period of time.

12. A lancing device according to claim 11, wherein the lance remains in the wound for a period of less than 20 ms and optionally less than 10 ms. 1()

13. A lancing device according to any preceding claim7 wherein said piezoelectric actuator mechanism is activated by a manual switch.

14. A lancing device according to any preceding claim wherein said piezoelectric I S actuator mechanism is activated automatically.

15. A lancing device according to claim 97 wherein said automatic activation is performed by a proximity sensor.

16. A lancing device according to any preceding claim further comprising a meter to form an integrated testing device for testing an analyte or indicator in a sample.

17. A lancing device according to any preceding claim wherein said lance is hollow and fluid is collected for testing through capillary action.

18. A lancing device according to any preceding claim, wherein said lance comprises one or more of a needle, sharp, points blade or other skin puncturing member.

19. A method of lancing a patient which comprises: providing a lancing device comprising a lance and a piezoelectric actuator mechanism for driving said lance towards a body to be lanced; positioning the lancing device on the patient such that the lance can penetrate the skin of the patient; and 1Ll actuating the piezoelectric actuator mechanism to cause the lance to penetrate the skin of the patient.

20. method of manufacturing a lancing device which comprises connecting a lance to a piezoelectric actuator in such a manner that, on operation of the piezoelectric actuator, the lance is driven towards a skin penetrating position.