US20040122339A1 - Sampling devices and methods utilizing biased capillary action - Google Patents

Abstract

A device is constructed so as to define a capillary channel that draws a body fluid form a proximal portion of the capillary channel toward a distal portion. A counterbore defining a “ledge” not substantially normal to the center line of channel causes the meniscus of body fluid to be “biased” into a non-radially-symmetric shape. In one example, the bias draws the body fluid toward a testing element that is set into a groove in the main body of the device. In another example, hydrophilic and/or hydrophobic regions are created on or in device to produce the biasing effect. In certain configurations, device requires less blood to be drawn into the capillary channel for a successful test than if the biasing effect were not created.

Description

REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Application No. 60/436,331, filed Dec. 24, 2002 (Attorney Docket No. 7404-453), which is hereby incorporated by reference in its entirety.[0001]
BACKGROUND
• The present invention generally relates to the medical field, and more specifically, but not exclusively, relates to the sampling of bodily fluids.[0002]
• The acquisition and testing of body fluids is useful for many purposes, and continues to be of importance for use in medical diagnosis and treatment, and in other diverse applications. In the medical field, it is desirable for lay operators to perform tests routinely, quickly and accurately outside of a laboratory setting, with rapid results and a read-out of the resulting test information. Testing can be performed on various body fluids, and for certain applications, it is particularly related to testing of blood and/or interstitial fluid. Such fluids can be tested for a variety of characteristics of the fluid or analytes contained in the fluid, in order to identify medical conditions, determine therapeutic responses, assess progress of treatments and the like.[0003]
• A common medical test is the measurement of blood glucose levels. The glucose level can be determined directly by analysis of the blood, or indirectly by analysis of other fluids, such as interstitial fluid. Diabetics are generally instructed to measure their glucose levels several times a day, depending on the nature and severity of their diabetes. Based upon observed patterns in the measurement of glucose levels, the patient and physician can determine the appropriate level of insulin to be administered, also taking into account such issues as diet, exercise and other factors.[0004]
• In testing for the presence of analytes such as glucose in a body fluid, test systems are commonly used which take advantage of oxidation/reduction reaction, which occurs using an oxidase/peroxidase detection chemistry. The testing reagent is exposed to a sample of the body fluid for a suitable period of time, and there is a color change if analyte (glucose) is present. Typically, the intensity of the change is proportional to the concentration of analyte in the sample. The color of the reagent is then compared to a known standard, which enables one to determine the amount of analyte present in the sample. This determination can be made, for example, by visual check or by an instrument, such as a spectrophotometer at a selected wave length, or a blood glucose meter. Electrochemical and other systems are also well known for testing body fluids for properties of constituents. Typically, a fingertip or some other body location of a patient is lanced with a lancet in order to obtain a body fluid sample.[0005]
• Although fingertips generally provide an ample supply of blood, repeated lancing of fingertips can be quite painful due to the high concentration of nerve endings in the fingertips. Therefore, there has been a trend towards sampling fluids from alternate sites on the body, where the nerve concentrations are lower, such as the forearm. As should be appreciated, since alternate sites have lower nerve concentrations, the patient experiences less pain when lancing the alternate site. However, these alternate sites usually produce less fluid as compared to fingertips. Consequently, it has been a goal to reduce the amount of fluid needed for a successful test. To achieve this goal, it is desirable to ensure that as much fluid as possible is transported from the incision to the test area so as to minimize waste.[0006]
• Thus, there remains a need for improvement in this field.[0007]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is an isometric view of a portion of an example apparatus according to the present invention.[0008]
• FIG. 2A is an end view of the apparatus of FIG. 1.[0009]
• FIG. 2B is a side view of the apparatus of FIG. 1.[0010]
• FIG. 2C is a cross-sectional view taken along[0011]line2C-2C of FIG. 2B.
• FIG. 3 is a side view of the apparatus of FIG. 1 disposed above body fluid on a tissue surface.[0012]
• FIG. 4 is a side view illustrating the apparatus of FIG. 1 displaying the initial capillary action.[0013]
• FIG. 5 is a side view illustrating the apparatus of FIG. 1 displaying biased capillary action.[0014]
• FIG. 6 is a side view of a portion of an alternative example apparatus according:to the present invention displaying another form of biased capillary action.[0015]
• FIG. 7 is a side view of the apparatus of FIG. 6 illustrating a test strip disposed within a groove in the apparatus.[0016]
• FIG. 8 is a side view of a portion of another alternative example apparatus according to the present invention.[0017]
• FIG. 9 is a side view of the apparatus of FIG. 8 displaying another form of biased capillary action.[0018]
• FIG. 10 is a side view of the apparatus of FIG. 8 illustrating a test strip disposed within a groove in the apparatus.[0019]
• FIG. 11 is a side view of a portion of yet another alternative example apparatus according to the present invention.[0020]
• FIG. 12 is an isometric view of a portion of another example apparatus according to the present invention.[0021]
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• Provided below is a written description of examples embodying the invention and examples of making and using the same. The scope of the invention is not limited to these examples, but rather is defined solely by the numbered claims that appear at the end of this document, and the invention includes alterations, modifications, and further applications that fall within the claims. The written description uses full, clear, concise, and exact terms to enable any person skilled in the art to which the invention pertains to make and use the invention. The best mode contemplated by the inventor of carrying out the invention is also set forth herein.[0022]
• All the information set forth in the following patent applications is incorporated by reference, as if fully set forth herein: U.S. patent application Ser. No. 10/054,270, filed Jan. 22, 2002, entitled LANCET DEVICE HAVING CAPILLARY ACTION; and U.S. patent application Ser. No. 10/165,101, filed Jun. 7, 2002, entitled SAMPLING DEVICES AND METHODS UTILIZING A HORIZONTAL CAPILLARY TEST STRIP.[0023]
• The present invention generally concerns a sampling device that is configured to bias the flow of body fluid in the device so as to reduce the amount of fluid needed for sampling. In one embodiment, the device has a capillary channel that is structured to bias a miniscus of the fluid in a radially asymmetric manner. Specifically, the capillary channel has an angled counter bore that biases the meniscus of the fluid in a radial asymmetric manner. In another embodiment, the capillary channel includes hydrophobic and hydrophillic portions that bias the flow of fluid.[0024]
• FIG. 1 illustrates one example of a[0025]device100 for sampling body fluid (not shown), comprising amain body110 defining acapillary channel120. Thecapillary channel120 is preferably dimensioned to draw a body fluid into thecapillary channel120 through capillary action, as described more fully in the above-incorporated patent applications. In this example thecapillary channel120 is further dimensioned to form anangled counterbore130.
• Though the[0026]device100 is shown in FIG. 1 as cylindrical with an annular cross-section, this is just one example geometry. Any geometry can be used fordevice100, as long asdevice100 provides acapillary channel120 dimensioned to draw a body fluid into saidcapillary channel120 through capillary action. For example, one or more portions ofdevice100 and/orcapillary channel120 could independently have square, rectangular, triangular, oval, U-shaped, amorphous, or any other shape cross-sections.Device100 may comprise any material and may be made by any means, such as the materials and methods of manufacture set forth in the above-incorporated patent applications.
• FIGS. 2A, 2B and[0027]2C further illustrates the example of FIG. 1. The device, or apparatus,100 comprises abody110 defining acapillary channel120 having afirst region140 and asecond region150 and aproximal portion160 and adistal portion170. In the example shown in FIGS.1-5, thesecond region150 of thecapillary channel120 defines acounterbore130 ending in a surface non-normal to thelongitudinal axis180 of thecapillary channel120 by angle α.
• FIG. 3 illustrates the[0028]device100 positioned above a drop ofbody fluid310 issuing from anincision305 inbody tissue300. Thebody fluid310 may be produced by puncturing thebody tissue300, or by any other means, including as described in the above-incorporated patent applications. FIG. 4 illustrates thedevice100 lowered toward thebody tissue300 until theproximal portion160 of thecapillary channel120 is in fluid communication with thebody fluid310. Thebody fluid310 is then drawn into thecapillary channel120 by capillary action, as represented in FIGS. 4 and 5. As shown in FIGS. 4 and 5, thebody fluid310 flows in thecapillary channel120 from theproximal portion160 toward thedistal portion170. However, when thebody fluid310 reaches theangled counterbore130, themeniscus320 of thebody fluid310 is biased radially asymmetrically about thecenterline180 toward one side ofcapillary channel120, as shown in FIG. 5.
• Capillary mechanics dictate that the step or offset created by the[0029]angled counterbore130 causes thefirst region140 to have an effectively stronger capillary attraction tobody fluid310 than thesecond region150 when thebody fluid310 flows in thecapillary channel120 from theproximal portion160 toward thedistal portion170. Though anangled counterbore130 is shown as an example, any geometry including a step or other shape can be used that has the capillary biasing effect of biasing the forces of capillary action acting onbody fluid310 so that they are radially asymmetric about thecenterline180, such as by tending to favor one side ofcapillary channel120.
• This difference in capillary attraction pulls or biases the[0030]meniscus320 radially asymmetrically about thecenterline180, toward thefirst region140 and away from thesecond region150, thus biasing thebody fluid310 toward afirst side122 of thecapillary channel120, and away from asecond side124 of thecapillary channel120. Subject to the materials and dimensions used indevice100 and their interaction with aparticular body fluid310, increasing the angle α tends to increasingly bias thebody fluid310 toward afirst side122 of thecapillary channel120, and away from asecond side124 of thecapillary channel120.
• FIG. 6 shows a[0031]device100′ that is similar todevice100, but has acounterbore130′ with an increased angle α′. As shown in FIG. 6, increasing the angle from α to α′ tends to increase the bias of themeniscus320 radially asymmetrically about thecenterline180, thus tending to increase the bias of thebody fluid310 toward afirst side122 of thecapillary channel120, and away from asecond side124 of thecapillary channel120.
• FIG. 7 shows the[0032]device100′ of FIG. 6 further including atesting element700 disposed within agroove710 in themain body110′ of thedevice100″. Whenbody fluid310 has moved upfirst side122, as shown, thetesting element700 is in spatial communication withbody fluid310 through one ormore passageways720, so that thetesting element700 may be used to test various aspects of thebody fluid310, for instance as described in the above-incorporated patent applications.Testing element700 may be any testing means that interfaces withbody fluid310, such as a test strip or other chemistry, for instance as described in the above-incorporated patent applications.
• Since the[0033]body fluid310 tends to bias toward thefirst side122 of thecapillary channel120,passageways720 are shown formed in thefirst side122 of thecapillary channel120.Passageways720 are filled withbody fluid310, even though the adjacent portion of thecapillary channel120 is only partially filled withbody fluid310 due to the biasing effect described above. Thus, thedevice100″ is capable of communicatingbody fluid310 totesting element700 usingless body fluid310 than would be required without the capillary biasing effect described herein.
• FIG. 8 illustrates another[0034]example device100″ configured to create a capillary biasing effect without requiring anangled counterbore130 or any geometry such as a step or other shape in thecapillary channel120. Instead, thefirst side122 of thecapillary channel120 includes ahydrophilic region800. Thehydrophilic region800 is hydrophilic relative to one or more adjacent regions of thecapillary channel120, such as thesecond side124. Thehydrophilic region800 need only be relatively hydrophilic; for instance, thehydrophilic region800 may be defined by providing hydrophobic surrounding regions. A relativelyhydrophilic region800 may be created by forming portions of thecapillary channel120 from hydrophilic or hydrophobic materials, or by treating portions to be relatively hydrophilic or hydrophobic, for instance in the manners described in the above-incorporated patent applications.
• FIG. 9 illustrates the[0035]device100″ of FIG. 8 positioned nearbody tissue300 so that theproximal portion160 of thecapillary channel120 is in fluid communication with a small drop ofbody fluid310 issuing from anincision305 inbody tissue300, thebody fluid310 being drawn into thecapillary channel120 by capillary action. When thebody fluid310 reaches the relativelyhydrophilic region800, thebody fluid310 is disproportionately attracted to thehydrophilic region800. This difference in capillary attraction pulls or biases themeniscus320 radially asymmetrically about thecenterline180, thus biasing thebody fluid310 toward the relativelyhydrophilic region800 of thefirst side122 of thecapillary channel120, and away from the relatively hydrophobicsecond side124 of thecapillary channel120.
• FIG. 10 shows the[0036]device100″ of FIG. 9 further including atesting element700 disposed within agroove710 in themain body110″ of thedevice100″. Thetesting element700 is in spatial communication withbody fluid310 through one ormore passageways720, so that thetesting element700 may be used to test various aspects of thebody fluid310, as set forth above. Since thebody fluid310 tends to bias toward thehydrophilic region800 on thefirst side122 of thecapillary channel120,passageways720 are shown formed in thefirst side122 of thecapillary channel120.Passageways720 are filled withbody fluid310, even though the adjacent portion of thecapillary channel120 is only partially filled withbody fluid310 due to the biasing effect described above. Thus, thedevice100″ is capable of communicatingbody fluid310 totesting element700 usingless body fluid310 than would be required without the capillary biasing effect described herein.
• FIG. 11 shows a[0037]device100′″ including by way of example both anangled counterbore130 and a relativelyhydrophilic region800 in thecapillary channel120, and further including anintegrated lancet1100 for forming theincision305. Theintegrated lancet1100, or any other structure, may be used in conjunction with devices incorporating the capillary biasing effect described herein. For instance, devices including anintegrated lancet1100 can include any or all of the structure set forth in the above-incorporated patent applications. In this example, anangled counterbore130 works in conjunction with a relativelyhydrophilic region800 to biasbody fluid310 towardtesting element700 usingless body fluid310 than would be required without the capillary biasing effect described herein.
• FIG. 12 illustrates a[0038]capillary tube1200 according to another embodiment of the present invention. In the illustrated embodiment, thecapillary tube1200 has a stepped-end counterbore1202 for biasing the fluid in a specified direction inside the capillary tube.
• Various alternatives to the structures and details described herein are available, and could be implemented without undue experimentation by those skilled in the art. For example, a plurality of sites on a testing device might be used for testing the same or different characteristics of the body fluid. Those sites might be spaced around the circumference of the device at approximately the same distance from the proximal end, or they might be situated at different distances from the proximal end. They may be on the same side of the device, opposite sides of the device, or in some other relative configuration.[0039]
• Further, various test methods may be implemented at the one or more test sites, including for example optical, magnetic, and chemical tests as would occur to one skilled in the art given the disclosure herein, which includes the matter incorporated by reference above.[0040]
• Furthermore, a wide variety of techniques might be used to bias the body fluid toward the testing site(s). These techniques might include (but are not limited to) the angled-end counterbore and hydrophobic/hydrophilic wall techniques discussed above; chemically treating or coating one or more portions of the inner wall of the capillary tube with one or more different hydrophobic, hydrophilic, or other chemicals known in the art; the stepped-[0041]end counterbore1202 as shown in FIG. 12; roughening the inner wall of the capillary tube in one region relative to another; and forming longitudinal grooves in certain portions of the inner wall (or more grooves in certain portions than in others).
• While examples embodying the invention have been illustrated and described in detail in the drawings and foregoing description, which includes material incorporated by reference, these examples are illustrative and not restrictive in character, it being understood that only certain examples have been shown and described and that all changes and modifications that come within the spirit of the invention are to be protected.[0042]

Claims (41)

What is claimed is:

1. A device comprising a main body that defines a capillary channel, wherein:

said capillary channel is dimensioned to draw a body fluid into said capillary channel by capillary action;

said body fluid defines a meniscus when said body fluid is drawn into said capillary channel; and

said capillary channel is constructed to tend to bias said meniscus in a radially asymmetric manner when said body fluid is drawn into said capillary channel.

2. The device ofclaim 1 wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

3. The device ofclaim 2 wherein said testing element comprises a test strip.

4. The device ofclaim 3 wherein said test strip comprises a membrane.

5. The device ofclaim 3 wherein said test strip is mounted in a groove defined in said device.

6. A device for sampling body fluid, comprising a main body that defines a capillary channel, wherein:

said capillary channel is dimensioned to draw a body fluid into said capillary channel by capillary action;

said body fluid defines a meniscus when said body fluid is drawn into said capillary channel; and

said capillary channel has a relatively hydrophilic portion tending to bias said meniscus in a radially asymmetric manner when said body fluid is drawn into said capillary channel.

7. The device ofclaim 6 wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

8. The device ofclaim 7 wherein said testing element comprises a test strip.

9. The device ofclaim 8 wherein said test strip comprises a membrane.

10. The device ofclaim 8 wherein said test strip is mounted in a groove defined in said device.

11. A fluid sampling device comprising a capillary tube defining a capillary channel adapted to contain fluid defining a meniscus, the capillary channel further adapted to impart a radially asymmetric bias to the meniscus of the fluid when the fluid is within the capillary channel.

12. The device ofclaim 11, the capillary channel having an angled counterbore adapted to impart the radially asymmetric bias to the meniscus of the fluid when the fluid is within the capillary channel.

13. The device ofclaim 12, wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

14. The device ofclaim 13, wherein said testing element comprises a test strip.

15. The device ofclaim 14, wherein said test strip comprises a membrane.

16. The device ofclaim 14, wherein said test strip is mounted in a groove defined in said device.

17. The device ofclaim 11, the capillary channel having a hydrophilic region adapted to impart the radially asymmetric bias to the meniscus of the fluid when the fluid is within the capillary channel.

18. The device ofclaim 17, wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

19. The device ofclaim 18, wherein said testing element comprises a test strip.

20. The device ofclaim 19, wherein said test strip comprises a membrane.

21. The device ofclaim 19, wherein said test strip is mounted in a groove defined in said device.

22. A device, comprising:

a body defining a capillary channel having a first region and a second region and a proximal portion and a distal portion;

the first region having a first capillary attraction to a fluid when the fluid flows in the capillary channel from the proximate portion toward the distal portion;

the second region having a second capillary attraction to the fluid when the fluid flows in the capillary channel from the proximate portion toward the distal portion; and

the first capillary attraction being stronger than the second capillary attraction sufficiently to bias the flow of the fluid within the capillary channel toward the first region when the fluid flows in the capillary channel from the proximate portion toward the distal portion.

23. The device ofclaim 22 wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

24. The device ofclaim 23, wherein said testing element comprises a test strip.

25. The device ofclaim 24, wherein said test strip comprises a membrane.

26. The device ofclaim 24, wherein said test strip is mounted in a groove defined in said device.

27. A fluid sampling device comprising body means defining capillary channel means, wherein the capillary channel means includes means for biasing the meniscus of fluid within the capillary channel means.

28. The device ofclaim 27, wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

29. The device ofclaim 28, wherein said testing element comprises a test strip.

30. The device ofclaim 29, wherein said test strip comprises a membrane.

31. The device ofclaim 29, wherein said test strip is mounted in a groove defined in said device.

32. A device for sampling body fluid, comprising:

a body defining a capillary channel; and

a lancet disposed within said capillary channel and defining a space between said lancet and said body;

said lancet being selectively advancable and retractable;

said capillary channel being dimensioned to draw a body fluid into said space through capillary action;

said body fluid defining a meniscus when said body fluid is drawn into said space; and

said capillary channel, or said lancet, or both, being dimensioned to tend to bias said meniscus in a radially asymmetric manner when said body fluid is drawn into said space.

33. The device ofclaim 32, wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

34. The device ofclaim 33, wherein said testing element comprises a test strip.

35. The device ofclaim 34, wherein said test strip comprises a membrane.

36. The device ofclaim 34, wherein said test strip is mounted in a groove defined in said device.

37. A device for sampling body fluid, comprising:

a body defining a capillary channel; and

a lancet disposed within said capillary channel and defining a space between said lancet and said body;

said lancet being selectively advancable and retractable;

said capillary channel being dimensioned to draw a body fluid into the space through capillary action;

said body fluid defining a meniscus when said body fluid is drawn into the space; and

said capillary channel, or said lancet, or both, having a relatively hydrophilic portion tending to bias said meniscus toward said hydrophilic portion when said body fluid is drawn into the space.

38. The device ofclaim 37, wherein said bias tends to bias said fluid toward a testing element in spatial communication with said fluid.

39. The device ofclaim 38, wherein said testing element comprises a test strip.

40. The device ofclaim 39, wherein said test strip comprises a membrane.

41. The device ofclaim 39, wherein said test strip is mounted in a groove defined in said device.

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