Sampling devices and methods utilizing biased capillary action

This application is a continuation of U.S. application Ser. No. 10/732,615, filed Dec. 10, 2003 now abandoned, which claims the benefit of U.S. Provisional Application No. 60/436,331, filed Dec. 24, 2002, which are hereby incorporated by reference in their entirety.

The present invention generally relates to the medical field, and more specifically, but not exclusively, relates to the sampling of bodily fluids.

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.

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.

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.

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.

Thus, there remains a need for improvement in this field.

FIG. 1 is an isometric view of a portion of an example apparatus according to the present invention.

FIG. 2A is an end view of the apparatus of FIG. 1 .

FIG. 2B is a side view of the apparatus of FIG. 1 .

FIG. 2C is a cross-sectional view taken along line 2 C- 2 C of FIG. 2B .

FIG. 3 is a side view of the apparatus of FIG. 1 disposed above body fluid on a tissue surface.

FIG. 4 is a side view illustrating the apparatus of FIG. 1 displaying the initial capillary action.

FIG. 5 is a side view illustrating the apparatus of FIG. 1 displaying biased capillary action.

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.

FIG. 7 is a side view of the apparatus of FIG. 6 illustrating a test strip disposed within a groove in the apparatus.

FIG. 8 is a side view of a portion of another alternative example apparatus according to the present invention.

FIG. 9 is a side view of the apparatus of FIG. 8 displaying another form of biased capillary action.

FIG. 10 is a side view of the apparatus of FIG. 8 illustrating a test strip disposed within a groove in the apparatus.

FIG. 11 is a side view of a portion of yet another alternative example apparatus according to the present invention.

FIG. 12 is an isometric view of a portion of another example apparatus according to the present invention.

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.

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.

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. FIG. 1 illustrates one example of a device 100 for sampling body fluid (not shown), comprising a main body 110 defining a capillary channel 120 . The capillary channel 120 is preferably dimensioned to draw a body fluid into the capillary channel 120 through capillary action, as described more fully in the above-incorporated patent applications. In this example the capillary channel 120 is further dimensioned to form an angled counterbore 130 . Though the device 100 is shown in FIG. 1 as cylindrical with an annular cross-section, this is just one example geometry. Any geometry can be used for device 100 , as long as device 100 provides a capillary channel 120 dimensioned to draw a body fluid into said capillary channel 120 through capillary action. For example, one or more portions of device 100 and/or capillary channel 120 could independently have square, rectangular, triangular, oval, U-shaped, amorphous, or any other shape cross-sections. Device 100 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 , 2 B and 2 C further illustrates the example of FIG. 1 . The device, or apparatus, 100 comprises a body 110 defining a capillary channel 120 having a first region 140 and a second region 150 and a proximal portion 160 and a distal portion 170 . In the example shown in FIGS. 1-5 , the second region 150 of the capillary channel 120 defines a counterbore 130 ending in a surface non-normal to the longitudinal axis 180 of the capillary channel 120 by angle α.

FIG. 3 illustrates the device 100 positioned above a drop of body fluid 310 issuing from an incision 305 in body tissue 300 . The body fluid 310 may be produced by puncturing the body tissue 300 , or by any other means, including as described in the above-incorporated patent applications. FIG. 4 illustrates the device 100 lowered toward the body tissue 300 until the proximal portion 160 of the capillary channel 120 is in fluid communication with the body fluid 310 . The body fluid 310 is then drawn into the capillary channel 120 by capillary action, as represented in FIGS. 4 and 5 . As shown in FIGS. 4 and 5 , the body fluid 310 flows in the capillary channel 120 from the proximal portion 160 toward the distal portion 170 . However, when the body fluid 310 reaches the angled counterbore 130 , the meniscus 320 of the body fluid 310 is biased radially asymmetrically about the centerline 180 toward one side of capillary channel 120 , as shown in FIG. 5 .

Capillary mechanics dictate that the step or offset created by the angled counterbore 130 causes the first region 140 to have an effectively stronger capillary attraction to body fluid 310 than the second region 150 when the body fluid 310 flows in the capillary channel 120 from the proximal portion 160 toward the distal portion 170 . Though an angled counterbore 130 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 on body fluid 310 so that they are radially asymmetric about the centerline 180 , such as by tending to favor one side of capillary channel 120 .

This difference in capillary attraction pulls or biases the meniscus 320 radially asymmetrically about the centerline 180 , toward the first region 140 and away from the second region 150 , thus biasing the body fluid 310 toward a first side 122 of the capillary channel 120 , and away from a second side 124 of the capillary channel 120 . Subject to the materials and dimensions used in device 100 and their interaction with a particular body fluid 310 , increasing the angle α tends to increasingly bias the body fluid 310 toward a first side 122 of the capillary channel 120 , and away from a second side 124 of the capillary channel 120 .

FIG. 6 shows a device 100 ′ that is similar to device 100 , but has a counterbore 130 ′ with an increased angle α′. As shown in FIG. 6 , increasing the angle from α to α′ tends to increase the bias of the meniscus 320 radially asymmetrically about the centerline 180 , thus tending to increase the bias of the body fluid 310 toward a first side 122 of the capillary channel 120 , and away from a second side 124 of the capillary channel 120 .

FIG. 7 shows the device 100 ′ of FIG. 6 further including a testing element 700 disposed within a groove 710 in the main body 110 ′ of the device 100 ″. When body fluid 310 has moved up first side 122 , as shown, the testing element 700 is in spatial communication with body fluid 310 through one or more passageways 720 , so that the testing element 700 may be used to test various aspects of the body fluid 310 , for instance as described in the above-incorporated patent applications. Testing element 700 may be any testing means that interfaces with body fluid 310 , such as a test strip or other chemistry, for instance as described in the above-incorporated patent applications. In one embodiment, the testing element 700 includes a membrane.

Since the body fluid 310 tends to bias toward the first side 122 of the capillary channel 120 , passageways 720 are shown formed in the first side 122 of the capillary channel 120 . Passageways 720 are filled with body fluid 310 , even though the adjacent portion of the capillary channel 120 is only partially filled with body fluid 310 due to the biasing effect described above.

Thus, the device 100 ″ is capable of communicating body fluid 310 to testing element 700 using less body fluid 310 than would be required without the capillary biasing effect described herein.

FIG. 8 illustrates another example device 100 ″ configured to create a capillary biasing effect without requiring an angled counterbore 130 or any geometry such as a step or other shape in the capillary channel 120 . Instead, the first side 122 of the capillary channel 120 includes a hydrophilic region 800 . The hydrophilic region 800 is hydrophilic relative to one or more adjacent regions of the capillary channel 120 , such as the second side 124 . The hydrophilic region 800 need only be relatively hydrophilic; for instance, the hydrophilic region 800 may be defined by providing hydrophobic surrounding regions. A relatively hydrophilic region 800 may be created by forming portions of the capillary channel 120 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 device 100 ″ of FIG. 8 positioned near body tissue 300 so that the proximal portion 160 of the capillary channel 120 is in fluid communication with a small drop of body fluid 310 issuing from an incision 305 in body tissue 300 , the body fluid 310 being drawn into the capillary channel 120 by capillary action. When the body fluid 310 reaches the relatively hydrophilic region 800 , the body fluid 310 is disproportionately attracted to the hydrophilic region 800 . This difference in capillary attraction pulls or biases the meniscus 320 radially asymmetrically about the centerline 180 , thus biasing the body fluid 310 toward the relatively hydrophilic region 800 of the first side 122 of the capillary channel 120 , and away from the relatively hydrophobic second side 124 of the capillary channel 120 .

FIG. 10 shows the device 100 ″ of FIG. 9 further including a testing element 700 disposed within a groove 710 in the main body 110 ″ of the device 100 ″. The testing element 700 is in spatial communication with body fluid 310 through one or more passageways 720 , so that the testing element 700 may be used to test various aspects of the body fluid 310 , as set forth above.

Since the body fluid 310 tends to bias toward the hydrophilic region 800 on the first side 122 of the capillary channel 120 , passageways 720 are shown formed in the first side 122 of the capillary channel 120 . Passageways 720 are filled with body fluid 310 , even though the adjacent portion of the capillary channel 120 is only partially filled with body fluid 310 due to the biasing effect described above. Thus, the device 100 ″ is capable of communicating body fluid 310 to testing element 700 using less body fluid 310 than would be required without the capillary biasing effect described herein.

FIG. 11 shows a device 100 ″' including by way of example both an angled counterbore 130 and a relatively hydrophilic region 800 in the capillary channel 120 , and further including an integrated lancet 1100 for forming the incision 305 . The integrated lancet 1100 , or any other structure, may be used in conjunction with devices incorporating the capillary biasing effect described herein. For instance, devices including an integrated lancet 1100 can include any or all of the structure set forth in the above-incorporated patent applications. In this example, an angled counterbore 130 works in conjunction with a relatively hydrophilic region 800 to bias body fluid 310 toward testing element 700 using less body fluid 310 than would be required without the capillary biasing effect described herein.

FIG. 12 illustrates a capillary tube 1200 according to another embodiment of the present invention. In the illustrated embodiment, the capillary tube 1200 has a stepped-end counterbore 1202 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.

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.

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-end counterbore 1202 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.