U.S. patent application number 11/544331 was filed with the patent office on 2007-03-22 for method of preventing short sampling of a capillary or wicking fill device.
This patent application is currently assigned to LifeScan, Inc.. Invention is credited to Alastair McIndoe Hodges.
Application Number | 20070062315 11/544331 |
Document ID | / |
Family ID | 24137704 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070062315 |
Kind Code |
A1 |
Hodges; Alastair McIndoe |
March 22, 2007 |
Method of preventing short sampling of a capillary or wicking fill
device
Abstract
The current invention provides a device, and a method for using
the device, for ensuring that capillary or wicking fill device is
fully filled. In particular this invention is directed to, but not
limited to, use with capillary or wicking action filled
electrochemical sensors suitable for use in analyzing blood or
interstitial fluids.
Inventors: |
Hodges; Alastair McIndoe;
(Blackburn South, AU) |
Correspondence
Address: |
NUTTER MCCLENNEN & FISH LLP
WORLD TRADE CENTER WEST
155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Assignee: |
LifeScan, Inc.
Milpitas
CA
|
Family ID: |
24137704 |
Appl. No.: |
11/544331 |
Filed: |
October 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10408189 |
Apr 3, 2003 |
7131342 |
|
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11544331 |
Oct 9, 2006 |
|
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09536234 |
Mar 27, 2000 |
6571651 |
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11544331 |
Oct 9, 2006 |
|
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Current U.S.
Class: |
73/864.72 |
Current CPC
Class: |
B01L 2300/0645 20130101;
B01L 2400/0406 20130101; Y10T 29/49117 20150115; B01L 3/5023
20130101; Y10T 29/49005 20150115; Y10T 29/49007 20150115; A61B
2562/0295 20130101; B01L 3/502738 20130101; B01L 2300/0887
20130101; B01L 2300/069 20130101; B01L 3/502746 20130101; Y10T
436/2575 20150115; B01L 3/502707 20130101; B01L 2300/0825 20130101;
B01L 3/50273 20130101; B01L 2300/165 20130101 |
Class at
Publication: |
073/864.72 |
International
Class: |
G01N 1/12 20060101
G01N001/12 |
Claims
1. A device for sampling a fluid, comprising: a pre-chamber having
an interior surface and being capable of exerting a first capillary
force, a sensing chamber in fluid communication with the
pre-chamber, the sensing chamber having an interior surface and
being capable of exerting a second capillary force; wherein a
differential exist between the capillary forces, the differential
being sufficient to cause flow of fluid from the pre-chamber to the
sensing chamber, and wherein the pre-chamber further comprises a
volume such that when full the pre-chamber comprises at least as
much sample as is needed to substantially fill the sensing
chamber.
2. The device of claim 2, wherein the interior surface of the
pre-chamber comprises at least first and second pre-chamber walls
spaced apart at a first distance to define a pre-chamber height,
and wherein the interior surface of the sensing chamber comprises
at least first and second sensing chamber walls spaced apart at a
second distance to define a sensing chamber height, wherein the
height of the sensing is less than the height of the pre-chamber,
and wherein the differential capillary force derives at least in
part from a difference between the pre-chamber height and the
sensing chamber height.
3. The device of claim 2, wherein the height of the sensing chamber
is defined by layers within the sensing chamber.
4. The device of claim 1, wherein the height of the sensing chamber
is defined by an aperture in a space layer.
5. The device of claim 1, wherein the interior surface of the
pre-chamber having a first surface roughness, as first actual
surface area, and a first geometric surface area, and the interior
surface of the sensing chamber having a second surface roughness, a
second actual surface area, and a second geometric surface area,
wherein the second surface roughness is greater than the first
surface roughness, and wherein the differential capillary force
derives from a difference between the second surface roughness and
the first surface roughness is defined as the actual surface area
divided by the geometric surface area.
6. The device of claim 1, wherein the sensing chamber comprises
electrodes capable of use in an electrochemical cell.
7. The device of claim 6, wherein the electrodes are spaced apart
by a distance of 600 microns or less.
8. The device of claim 6, wherein the electrodes are spaced apart
by a distance of 400 microns or less.
9. The device of claim 6, wherein the electrodes are spaced apart
by a distance of 200 microns or less.
10. The device of claim 1, wherein the interior surface of at least
the pre-chamber or the sensing chamber comprises a surface
treatment, wherein the differential capillary force derives from
the surface treatment.
11. The device of claim 10, wherein the surface treatment comprises
a hydrophilic substance.
12. The device of claim 10, wherein the surface treatment comprises
a hydrophobic substance.
13. The device of claim 10, wherein the surface treatment comprises
a substance selected from the group consisting of a surfactant, a
block copolymer, a hygroscopic compound, an ionizable substance,
and mixtures thereof.
14. The device of claim 10, wherein the interior surface of the
pre-chamber comprises a first surface treatment and the interior
surface of the sensing chamber comprises a second surface
treatment.
15. A method for ensuring that a sensing device is substantially
filled with a sample of fluid comprising: providing a device for
sampling a fluid, comprising a pre-chamber having an interior
surface and being capable of exerting a first capillary force, a
sensing chamber in fluid communication with the pre-chamber, the
sensing chamber having an interior surface and being capable of
exerting a second capillary force; wherein a differential exist
between the capillary forces, the differential being sufficient to
cause flow of fluid from the pre-chamber to the sensing chamber,
and wherein the pre-chamber further comprises a volume such that
when full the pre-chamber comprises at least as much sample as is
needed to substantially fill the sensing chamber; contacting the
device with the fluid for a sufficient period of time to allow the
fluid to enter the pre-chamber; and allowing the sample to flow
from the pre-chamber to the sensing chamber, such that the sensing
chamber is substantially filled.
16. The method of claim 15, wherein the sensing chamber comprises
electrodes capable of use in an electrochemical cell.
17. The method of claim 16, wherein the electrodes are spaced apart
by a distance of 600 microns or less.
18. The method of claim 16, wherein the electrodes are spaced apart
by a distance of 400 microns or less.
19. The method of claim 16, wherein the electrodes are spaced apart
by a distance of 200 microns or less.
20. The method of claim 15, the sensing chamber further comprising
a chemical for use in the sensing chamber.
21. The method of claim 20, the chemical further comprising a
reagent capable of undergoing a redox reaction with an analyte or a
reaction product of the analyte.
22. The method of claim 15, further comprising the step of:
detecting a condition wherein the pre-chamber contains a volume of
fluid sufficient to substantially fill the sensing chamber.
23. The method of claim 15, further comprising the step of:
determining a presence or an absence of an analyte in the
sample.
24. The method of claim 23, wherein the determining step comprises
conducting a quantitative measurement of the analyte.
25. The method of claim 23, wherein the determining step comprises
an electrochemical measurement.
26. The method of claim 23, wherein the analyte comprises a
substance selected from the group consisting of lactate,
cholesterol, enzymes, nucleic acids, lipids, polysaccharides, and
metabolites.
27. The method of claim 23, wherein the analyte comprises
glucose.
28. The method of claim 23, wherein the sample comprises a
biological fluid.
29. The method of claim 28, wherein the biological fluid comprises
a body fluid of an animal or a plant.
30. The method of claim 29, wherein the body fluid is selected from
the group consisting of interstitial fluid, blood, tears,
expectorate, saliva, urine, semen, vomitus, sputum, fruit juice,
vegetable juice, plant sap, and nectar.
31. The method of claim 28, wherein the biological fluid comprises
a food product.
32. The method of claim 23, wherein the sample comprises a
non-biological fluid.
33. The method of claim 32, wherein the non-biological fluid
comprises a water-based solution.
34. The method of claim 15, wherein the interior surface of the
pre-chamber comprises at least first and second pre-chamber walls
spaced apart at a first distance to define a pre-chamber height,
and wherein the interior surface of the sensing chamber comprises
at least first and second sensing chamber walls spaced apart at a
second distance to define a sensing chamber height, wherein the
height of the sensing is less than the height of the pre-chamber,
and wherein the differential capillary force derives at least in
part from a difference between the pre-chamber height and the
sensing chamber height.
35. The method of claim 15, wherein the interior surface of the
pre-chamber having a first surface roughness, as first actual
surface area, and a first geometric surface area, and the interior
surface of the sensing chamber having a second surface roughness, a
second actual surface area, and a second geometric surface area,
wherein the second surface roughness is greater than the first
surface roughness, and wherein the differential capillary force
derives from a difference between the second surface roughness and
the first surface roughness is defined as the actual surface area
divided by the geometric surface area.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/408,189, filed Apr. 3, 2003, which is a
division of U.S. patent application Ser. No. 09/536,234, filed Mar.
27, 2000, now U.S. Pat. No. 6,571,651.
FIELD OF THE INVENTION
[0002] The present invention relates to a device and method for use
in the sampling and analyzing of bodily fluids, such as blood or
interstitial fluid, which prevents short sampling.
BACKGROUND OF THE INVENTION
[0003] The management of many medical conditions requires the
measurement and monitoring of a variety of analytes, e.g., glucose,
in bodily fluids. Currently, the measurement of analytes in blood
typically requires a venipuncture or finger puncture to obtain
blood for sampling purposes. More recently, techniques for
analyzing interstitial fluid components have been developed.
Regardless of the bodily fluid tested or analytical method used, it
is important that sufficient sample is collected in order to ensure
adequate test results. In prior art methods, however, adequate
sample collection is often a matter of trial and error.
[0004] It is therefore desirable to have a sampling and analyzing
device giving a clear signal that adequate sample has been
collected before the sampling device, e.g., a needle or other
penetration device, is removed from the patient's body. It is also
desirable that such a device be suitable for hospital bedside and
home use.
[0005] Capillary and wicking fill devices are well-known as
sampling devices and as sensing devices. However, one of the
deficiencies of the prior art is that there is either no cue, or
only a user-reliant visual cue, to indicate whether the device is
fully filled.
SUMMARY OF THE INVENTION
[0006] The present invention provides a device, and a method for
making and using the device, for ensuring that a capillary or
wicking fill device is fully filled. In particular, the invention
is directed to, but not limited to, use with capillary or wicking
action-filled electrochemical sensors.
[0007] In one embodiment of the present invention, a device for
sampling a fluid is provided, the device including a pre-chamber
having an interior surface and a first volume, the pre-chamber
being capable of exerting a first capillary force, the device
further including a sensing chamber in fluid communication with the
pre-chamber, the sensing chamber having an interior surface and a
second volume, the sensing chamber being capable of exerting a
second capillary force, wherein the first volume is not less than
the second volume, and wherein a differential exists between the
capillary forces, the differential being sufficient to cause flow
of fluid from the pre-chamber to substantially fill the sensing
chamber. The differential in capillary forces can result from the
first and second pre-chamber walls being spaced apart at distance
greater than the distance between the first and second sensing
chamber walls. The differential can also result from the surface
roughness, defined as the actual surface area divided by the
geometric surface area, of the pre-chamber being less than that of
the sensing chamber. Use of one or more surface treatments, which
can be the same or different, in one or both of the pre-chamber and
sensing chamber can result in a differential capillary force. The
surface treatment can include, for example, a hydrophilic or
hydrophobic substance. Surface treatments can be selected from
surfactants, block copolymers, hygroscopic compounds, ionizable
substances, and mixtures thereof.
[0008] In a further embodiment, one or both chambers can include,
for example, one or more materials which contribute to the
capillary force, such as meshes, fibrous materials, porous
materials, powders, and mixtures or combinations thereof. Where a
mesh is used, a smaller mesh can be used in the pre-chamber than
that used in the analysis chamber. The mesh can be made of
polyolefin, polyester, nylon, cellulose, polystyrene,
polycarbonate, polysulfone or mixtures thereof. Fibrous filling
material such as polyolefin, polyester, nylon, cellulose,
polystyrene, polycarbonate, and polysulfone, or other nonwoven or
melt blown polymers can be used. The porous material can include,
for example, a sintered powder or a macroporous membrane, the
membrane including polysulfone, polyvinylidenedifluoride, nylon,
cellulose acetate, polymethacrylate, polyacrylate, or mixtures
thereof. The powder, which can be soluble or insoluble in the
sample, can include, for example, microcrystalline cellulose,
soluble salts, insoluble salts, and sucrose.
[0009] In a further embodiment, the device includes electrodes
capable of use in an electrochemical cell, or a detector capable of
detecting a condition wherein the pre-chamber contains a volume of
fluid sufficient to substantially fill the sensing chamber. A
glucose monitoring test strip can include the device.
[0010] In yet another embodiment of the present invention, a method
is provided for ensuring that a sensing device is substantially
filled with a sample of fluid including: providing a device as
described above; contacting the device with the fluid for a
sufficient period of time to allow the fluid to enter the
pre-chamber in an volume equal to or greater than the volume of the
sensing chamber; and allowing the sample to flow from the
pre-chamber to the sensing chamber, such that the sensing chamber
is substantially filled. The method can further include the step of
determining presence or absence of an analyte in the sample, e.g.,
conducting a quantitative measurement or electrochemical
measurement of the analyte. The analyte can include, for example, a
substance such as glucose, lactate, cholesterol, enzymes, nucleic
acids, lipids, polysaccharides, and metabolites. The sample can
include, for example, a biological fluid, such as a body fluid of
an animal or plant, e.g., interstitial fluid, blood, tears,
expectorate, saliva, urine, semen, vomitus, sputum, fruit juice,
vegetable juice, plant sap, nectar, and biological fluid-based food
products. Non-biological fluids that can be tested include
non-biological fluid-based food products or beverages, drinking
water, process water, and water-based solutions.
[0011] In a further embodiment of the present invention, a method
of manufacturing a device as described above is provided, the
method including: forming an aperture extending through a sheet of
electrically resistive material, the aperture defining a side wall
of the sensing chamber; mounting a first thin layer to a first side
of the sheet and extending over the aperture whereby to define a
first sensing chamber end wall; mounting a second thin layer to a
second side of the sheet and extending over the aperture whereby to
define a second sensing chamber end wall in substantial overlying
registration with the first thin layer, whereby the sheet and
layers form a strip; removing a section of the strip which overlaps
the sensing chamber and an edge of the strip whereby to define a
notch; mounting a first covering layer to a first side of the strip
and extending over the notch whereby to define a first pre-chamber
wall; and mounting a second covering layer to a second side of the
strip and extending over the notch whereby to define a second
pre-chamber wall in substantial overlying registration with the
first covering layer.
[0012] In a further embodiment, the first and second thin layers
can include a first and second electrode layer, the electrode
layers facing in towards the cell. The electrodes, which can
substantially cover the aperture, which can be circular, can
include, for example, a noble metal, e.g., palladium, platinum, and
silver, optionally sputter coated. An adhesive can be used to
adhere the electrode layers to the sheet, e.g., a heat activated
adhesive.
[0013] In a further embodiment, the chamber contains a chemical for
use in the sensing chamber, e.g., a reagent capable of undergoing a
redox reaction with an analyte or a reaction product of the
analyte. The chemical can be printed onto at least one wall of the
sensing chamber, or contained in or on a support included in the
sensing chamber. At least one of the sheet, thin layers, or
covering layers can include, for example, polyethylene
terephthalate. The second electrode layer can be mounted in
opposing relationship a distance of less than 200 microns from the
first electrode layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 provides a top view of the sampling device
illustrating an arrangement of the pre-chamber and sensing chamber.
In the illustrated embodiment, the device has two pre-chambers and
one sensing chamber.
[0015] FIG. 2 provides a cross section of the device along line
A-A' of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] The following description and examples illustrate various
embodiments of the present invention in detail. Those of skill in
the art will recognize that there are numerous variations and
modifications of this invention that are encompassed by its scope.
Accordingly, the description of a preferred embodiment should not
be deemed to limit the scope of the present invention. Methods and
devices for sampling fluid samples are discussed further in
copending U.S. patent application Ser. No. 09/536,235, filed on
Mar. 27, 2000, entitled "METHOD AND DEVICE FOR SAMPLING AND
ANALYZING INTERSTITIAL FLUID AND WHOLE BLOOD SAMPLES," which is
incorporated herein by reference in its entirety.
[0017] The current invention provides a device 10, and a method for
making and using the device 10, for ensuring that a capillary or
wicking fill device 10 is fully filled. In particular this
invention is directed to, but not limited to, use with capillary or
wicking action filled electrochemical sensors.
[0018] The device 10 consists of a pre-chamber 12, which fills by
capillary action or wicking action, which is in fluid communication
with a sensing chamber 14, which also fills by capillary or wicking
action. Reliable and substantially complete filling of the sensing
chamber 14 is a primary object of the present invention.
[0019] The pre-chamber 12 has an interior surface and a volume, and
is capable of exerting a first capillary force. The interior
surface of the pre-chamber 12 comprises first and second
pre-chamber walls 20 spaced apart at a first distance to define the
pre-chamber height. The sensing chamber 14 also has an interior
surface and a volume, and is capable of exerting a second capillary
force different from that of the pre-chamber 12. The interior
surface of the sensing chamber 14 comprises a first and a second
sensing chamber wall 22 spaced apart at a second distance to define
the height of the sensing chamber 14.
[0020] The difference between the capillary force exerted by the
pre-chamber 12 and the sensing chamber 14 causes the flow of fluid
from the pre-chamber 12 to the sensing chamber 14, so as to
substantially fill the sensing chamber 14. To ensure that the
sensing chamber 14 is substantially filled, the pre-chamber 12 is
of such a volume that when full it contains at least as much or
more sample than is needed to fill the sensing chamber 14. In a
preferred embodiment, the layers 18 within the sensing chamber
serve to define the sensing chamber 14. The layers 18 are spaced
apart by a spacer layer (not shown in FIG. 1 or 2), wherein an
aperture in the spacer layer defines the height of the sensing
chamber 14. The pre-chamber 12 has end walls formed by layers 16.
In this embodiment, the pre-chamber layers 16 are adhered or
otherwise attached to the outer surfaces of the sensing chamber
layers 18 in a suitable manner, such as by an adhesive.
[0021] In a preferred embodiment, a single pre-chamber 12 can be
used. Alternatively, two pre-chambers 12 placed on opposite sides
of the sensing chamber 14 chamber can be used, as illustrated in
FIGS. 1 and 2. In such an embodiment, the device can be filled from
both or either of the right and left sides of the device 10.
[0022] In use, a sample is introduced into the pre-chamber 12
through a port on a side of the pre-chamber 12 that is
substantially opposite to the boundary between the pre-chamber 12
and the sensing chamber 14. Sample is drawn into the pre-chamber 12
and fills across the pre-chamber 12 from the sampling port side to
the sensing chamber 14 opening side, until eventually sufficient
sample has been introduced into the pre-chamber 12 that it begins
to fill the sensing chamber 14. At this point, an optional detector
detects that the sensing chamber 14 has begun to fill and indicates
this to the user. Since by this time the pre-chamber 12 is fully
filled with sample, there is sufficient total sample in the
pre-chamber 12 to ensure that the sensing chamber 14 can be filled
completely.
[0023] The stronger capillary or wicking force of the sensing
chamber 14 as compared to that of the pre-chamber 12 ensures that
once the sensing chamber 14 begins to fill, if no additional sample
is added to the pre-chamber 12, then the sensing chamber 14 is
capable of at least partially drawing the sample from the
pre-chamber 12 to complete the filling of the sensing chamber 14.
If filling of the pre-chamber 12 is interrupted prior to being
fully filled, the detector is not triggered and the user knows that
insufficient sample is present in the sensing chamber. Extra sample
can then be added until the detector is triggered.
[0024] In a preferred embodiment of the present invention, the
capillary force is made stronger in the sensing chamber 14 than the
pre-chamber 12 by suitably treating the walls of the two chambers
12, 14 such that the energy liberated when the sample wets the
walls of the sensing chamber 14 is greater than the energy needed
to de-wet the walls of the first chamber 12. The surface treatment
can be applied to either chamber, or both chambers, and can
comprise any suitable hydrophilic or hydrophobic substance. For
example, suitable substances include surfactants, block copolymers,
hygroscopic compounds, or other substances that ionize or otherwise
react with or dissolve in the sample. If both chambers 12, 14 are
treated, the substance used to treat a given chamber 12, 14 can be
the same as or different from that used to treat the other chamber
12, 14, so long as the aggregate capillary forces of the two
chambers are different.
[0025] In another preferred embodiment, mesh is used to draw the
sample into the chambers 12, 14, with a finer mesh in the sensing
chamber 14 than the pre-chamber 12, so that the sample can be drawn
into the sensing chamber 14 and empty the pre-chamber 12. In an
alternative embodiment, the mesh in the sensing chamber 14, is not
finer than the mesh in the pre-chamber, but instead contributes to
a higher total capillary force within the sensing chamber by having
a more negative energy of interaction with the wetting liquid than
the mesh used in the pre-chamber 12. The energy of interaction of
the mesh can be modified through the use of a surface treatment as
described above. Alternatively, a fibrous filling material, a
porous material, or a powder could be used to draw sample into the
chambers 12, 14. Either or both of the chambers 12, 14 can contain
a capillarity enhancer, such as, for example, a mesh, a fibrous
filling material or a porous material. Such capillarity enhancers
can be either soluble or insoluble in the sample. If both chambers
12, 14 contain a capillarity enhancer, such enhancer can be the
same in both chambers or it can be different in each chamber,
provided a differential in capillary force exists between the
pre-chamber 12 and sensing chamber 14. Alternatively, various
combinations of different meshes, different fibrous materials, and
different porous materials are contemplated. Suitable mesh
materials include, for example, polyolefin, polyester, nylon,
cellulose, or meshes woven of fibrous materials. Suitable fibrous
materials include, for example, nonwoven or melt blown materials,
including polyolefin, polyester, nylon, cellulose, polystyrene,
polycarbonate, polysulfone. Suitable porous materials include, for
example, sintered powders or macroporous membranes such as those of
polysulfone, polyvinylidenedifluoride, nylon, cellulose acetate,
polymethacrylate, and polyacrylate. Suitable powders include
microcrystalline cellulose, soluble or insoluble salts, and soluble
powders such as sucrose.
[0026] In another preferred embodiment, the pre-chamber 12 has a
larger height than the height of the sensing chamber 14, such that
the capillary force drawing liquid into the sensing chamber 14 is
greater than the force holding liquid in the pre-chamber 12. Here,
the height of the capillary chamber typically refers to its
smallest internal dimension. Alternatively, the surface roughness
of the sensing chamber 14 can be made greater than the surface
roughness of the pre-chamber chamber 12, such as, for example, by
etching ridges or striations into the walls of the sensing chamber,
or by designing the physical dimensions of the sensing chamber
accordingly, such that the greater surface area of the sensing
chamber provides a greater capillary force. Surface roughness is
defined herein as the actual surface area divided by the geometric
surface area.
[0027] In a particularly preferred embodiment of the present
invention, capillary fill sensor strips 10 of the type disclosed in
PCT/AU96/00724 are fabricated, and a section of the strip 10 which
overlaps the sensing chamber 14 and intersects at least one edge of
the strip 10 is removed. The notch disclosed in PCT/AU96/00724 is
an example of such a region. Tape or other suitable layers 16 are
then overlaid and sealed to both faces of the strip 10 so as to
entirely cover the removed region. By this method a pre-chamber 12
is formed with an aperture or port opening to the edge of the strip
10 and an aperture or port opening to the sensing chamber 14 (which
in this case is the sensing chamber 14 referred to above).
[0028] In this embodiment, the height of the pre-chamber 12 is that
of the three laminate layers described in PCT/AU96/00724. The
height of the sensing chamber 14 is the thickness of the separating
layer between the two electrode layers, which is smaller than the
height of the pre-chamber 12. The capillary force drawing sample
into the sensing chamber 14 can therefore be stronger than the
force holding the sample in the pre-chamber 12, such that the
sensing chamber 14 fills and, if necessary, empties the pre-chamber
12 in the process. Emptying the pre-chamber 12 to at least some
extent is necessary if the sample source is withdrawn from the
pre-chamber 12 filling port during the filling of the sensing
chamber 14.
[0029] In a preferred embodiment, the function of the detector is
based on a change in voltage or current flowing between the sensing
electrodes, which can comprise a noble metal, e.g., palladium,
platinum or silver. The optimal distance between the electrodes is
a function of the reagents and conditions used, the analyte of
interest, the total volume of the cell, and the like. In one
embodiment, the electrodes are spaced apart at a distance of about
400 to 600 microns. In a preferred embodiment, the electrodes are
about 300 microns apart. In a more preferred embodiment, the
electrodes are spaced apart by a distance of 200 microns, or less.
Various most preferred embodiments have electrodes spaced about 40,
80, 120, or 160 microns. The cell can contain one or more
chemicals, e.g., a reagent capable of undergoing a redox reaction
with the analyte or a reaction product of the analyte, the redox
reaction producing a voltage or current indicative of the
concentration of the analyte. At this point the meter used in
conjunction with the test strip can optionally indicate visually or
aurally that sufficient sample has been introduced. Other detectors
useful with the current invention can function based on the
attenuation or change of position of a transmitted light beam, the
change in reflectance of a reflected light beam or any other
features that are capable of detection when the sample enters the
sensing chamber 14.
[0030] In a preferred embodiment, the device 10 can be used as a
glucose monitoring test strip, with the fluid sample being blood or
interstitial fluid. Other biological fluids that can be sampled
using the device 10 include other animal body fluids, such as, for
example, tears, expectorate, saliva, urine, semen, vomitus, and
sputum. Alternatively, the biological fluid can comprise a plant
extract, nectar, sap, or fruit or vegetable juice. Food products,
e.g., beverages, can be tested. Non-biological fluids can be tested
as well, e.g., process water, drinking water, or water-based
solutions.
[0031] The above description discloses several methods and
materials of the present invention. This invention is susceptible
to modifications in the methods and materials, as well as
alterations in the fabrication methods and equipment. Such
modifications will become apparent to those skilled in the art from
a consideration of this disclosure or practice of the invention
disclosed herein. Consequently, it is not intended that this
invention be limited to the specific embodiments disclosed herein,
but that it cover all modifications and alternatives coming within
the true scope and spirit of the invention as embodied in the
attached claims.
* * * * *