U.S. patent application number 11/392201 was filed with the patent office on 2006-07-27 for method of filling an amperometric cell.
This patent application is currently assigned to LifeScan, Inc.. Invention is credited to Thomas W. Beck, Alastair M. Hodges, Ian A. Maxwell.
Application Number | 20060163061 11/392201 |
Document ID | / |
Family ID | 3800159 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060163061 |
Kind Code |
A1 |
Hodges; Alastair M. ; et
al. |
July 27, 2006 |
Method of filling an amperometric cell
Abstract
The invention relates to an amperometric electrochemical cell
having a first insulating substrate carrying a first electrode, a
second insulting substrate carrying a second electrode, said
electrodes being disposed to face each other and spaced apart by
less than 500 .mu.m, and defining a sample reservoir therebetween,
and wherein at least one, and preferably both, insulating
substrates and the electrode carried thereon include an
electromagnetic radiation transmissive portion in registration with
said reservoir. The walls of the electrochemical cell may be formed
from a thin metallic portion on a transparent substrate. Such cells
are useful in providing visual confirmation of the validity of the
electrochemical measurement.
Inventors: |
Hodges; Alastair M.;
(Blackburn South, AU) ; Beck; Thomas W.; (North
Richmond, AU) ; Maxwell; Ian A.; (Five Dock,
AU) |
Correspondence
Address: |
LIFESCAN/NUTTER MCCLENNEN & FISH LLP
155 SEAPORT BOULEVARD
BOSTON
MA
02210-2604
US
|
Assignee: |
LifeScan, Inc.
Milpitas
CA
|
Family ID: |
3800159 |
Appl. No.: |
11/392201 |
Filed: |
March 29, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10387212 |
Mar 10, 2003 |
7041210 |
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11392201 |
Mar 29, 2006 |
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09568076 |
May 10, 2000 |
6592744 |
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10387212 |
Mar 10, 2003 |
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09404119 |
Sep 23, 1999 |
6454921 |
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09568076 |
May 10, 2000 |
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PCT/AU98/00200 |
Mar 25, 1998 |
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09404119 |
Sep 23, 1999 |
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Current U.S.
Class: |
204/401 |
Current CPC
Class: |
G01N 27/3272
20130101 |
Class at
Publication: |
204/401 |
International
Class: |
G01N 27/26 20060101
G01N027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 1997 |
AU |
PO 5857 |
Claims
1. A method of filling an amperometric cell comprising the steps
of: a) drawing a liquid sample into said cell comprising a first
insulating substrate carrying a first electrode, a second
insulating substrate carrying a second electrode, said electrodes
being disposed to face each other and spaced apart by less than 500
.mu.m, and defining a sample reservoir therebetween, wherein at
least one of said insulating substrates and the electrode carried
thereon includes an electromagnetic radiation transmissive portion
in registration with said reservoir; b) exposing the transmissive
portion to electromagnetic radiation; c) monitoring a property of
the electromagnetic radiation passing and/or reflected through said
transmissive portion; d) comparing said monitored property with a
value indicative of the cell being filled; and e) continuing to
draw the liquid sample into the cell until said monitored property
reaches said value.
2. A method according to claim 1 wherein the electromagnetic
radiation is selected from the group consisting of visible light,
ultraviolet, infra-red, and laser.
3. A method according to claim 2 wherein the visible light is
daylight.
4. A method according to claim 1 wherein said monitored property is
selected from the group consisting of optical density, wavelength,
refractive index and optical rotation.
5. A method according to claim 1 wherein the liquid sample is
blood.
6. A method according to claim 1 wherein the electromagnetic
property is monitored outside the cell.
7. A method according to claim 1 wherein the electromagnetic
property is monitored inside the cell.
8. A method according to claim 1 wherein the electromagnetic
radiation passing substantially directly through the sample is
monitored.
9. A method according to claim 1 wherein the electromagnetic
radiation reflected internally in the cell is monitored.
10. A method according to claim 1 wherein the electromagnetic
property is observed by a fibre optical device.
11. A method for monitoring an analyte in a liquid sample
comprising the steps of: a) drawing the sample into an amperometric
electrochemical cell comprising a first insulating substrate
carrying a first electrode, a second insulating substrate carrying
a second electrode, said electrodes being disposed to face each
other and spaced apart by less than 500 .mu.m, and defining a
sample reservoir therebetween, wherein at least one of said
insulating substrates and the electrode carried thereon includes an
electromagnetic radiation transmissive portion in registration with
said reservoir; b) exposing the transmissive portion to
electromagnetic radiation; c) monitoring a property of the
electromagnetic radiation passing and/or reflected through said
transmissive portion; d) comparing said monitored property with a
value indicative of the cell being filled; and e) prior to,
simultaneously with or after any one of steps b) to d) applying a
potential across the electrochemical cell and measuring the
resultant current to detect the analyte.
12. A method according to claim 11 further comprising the step of:
f) repeating steps a) to e) until the monitored property reaches
the value.
13. A method according to claim 12 wherein steps a) to e) are
repeated on the same cell.
14. A method according to claim 12 wherein steps a) to e) are
repeated on a new cell.
15. A method according to claim 12 wherein the sample is blood.
16. A method according to claim 11 wherein the electromagnetic
radiation is visible light.
17. A method according to claim 11 wherein the monitored property
is selected from the group consisting of optical density,
wavelength, refractive index and optical rotation.
18. A method according to claim 11 wherein the analyte is
glucose.
19. A method of determining whether an amperometric cell is filled
with a liquid sample, said cell comprising a first insulating
substrate carrying a first electrode, a second insulating substrate
carrying a second electrode, said electrodes being disposed to face
each other and spaced apart by less than 500 .mu.m, and defining a
sample reservoir therebetween, wherein at least one of said
insulating substrates and the electrode carried thereon includes an
electromagnetic radiation transmissive portion in registration with
said reservoir, said method comprising the steps of: a) exposing
said transmissive portion to electromagnetic radiation; b)
monitoring a property of the electromagnetic radiation passing
and/or reflected through said transmissive portion; and c)
comparing said monitored property with a value indicative of the
cell being filled.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
09/568,076, filed May 10, 2000, which is a division of application
Ser. No. 09/404,119, filed Sep. 23, 1999, which is a continuation,
under 35 U.S.C. .sctn. 120, of International Patent Application No.
PCT/AU98/00200, filed on Mar. 25, 1998 under the Patent Cooperation
Treaty (PCT), which was published by the International Bureau in
English on Oct. 1, 1998, which designates the U.S. and claims
priority from Australian Provisional Patent Application No. PO
5857, filed Mar. 25, 1997.
FIELD OF THE INVENTION
[0002] This invention relates to disposable electrochemical sensors
of the type used for quantitative analysis, for example, of glucose
levels in blood, or the like.
BACKGROUND OF THE INVENTION
[0003] Light transmissive electrodes are known in the prior art,
however they have not previously been applied to amperometric
cells. For example, GB 2 194 112 discloses the use of optically
transparent electrodes used to drive a microelectrophoresis cell
while laser Doppler velocimetry is used to determine the velocity
and micro current motion of charged particles within the
sample.
[0004] JP, A 05080018 discloses another approach to making
transparent electrodes by the use of conductive glass for
electrochromic and field emission devices.
[0005] JP, A 06310746 also teaches the use and formation of yet
another type of conducting transparent electrode formed from the
deposition of organic conducting polymers onto a glass slide. This
type of electrode is useful in solar energy collection cells.
Ullery, in U.S. Pat. No. 4,254,546 also discloses a photovoltaic
cell in which the top layer is a light collecting electrode.
[0006] U.S. Pat. No. 4,782,265 discloses two spaced apart
translucent electrodes useful in luminescent cells. However, U.S.
Pat. No. 4,782,265 specifically teaches that gold, silver,
aluminum, platinum and the like are only suitable for the
production of non-transmissive electrodes.
[0007] In co-pending applications PCT/AU95/00207, PCT/AU96/00365,
PCT/AU96/00723 and PCT/AU96/00724 (the contents of which are
incorporated herein by reference) there are described various very
thin electrochemical sensors or cells. These cells are by a pair of
oppositely facing spaced apart electrodes which are formed as thin
metal coatings (for example sputter coatings) deposited on thin
inert plastic film (for example 100 micron thick PET). The
electrodes are separated one from the other by a spacer of
thickness of for example 500 .mu.m or less.
[0008] Such cells may be provided with one or more fluid
passageways into and out of the sample reservoir whereby the cell
may be filled with an analyte and air expelled during filling. In
some embodiments the analyte is drawn into the cell by the energy
liberated as a reagent contained therein dissolves.
[0009] The sensors are, as discussed above, very small and normally
contain only small amounts of the liquid sample. Accurate
measurement requires that the cell be filled with liquid. Even
minute variations in the quantity of liquid in the cell can affect
the sensing measurements. It can be difficult for a user to be sure
that in use the cell has been uniformly filled with a sample to be
analysed.
[0010] Further, sensors of the kind under discussion are usually
intended to be discarded after use. If a user is distracted after
use or prior to disposal it is not always easy for the user to know
which sensors have been used and which have not
[0011] It is an object of the present invention to overcome or
ameliorate at least one of the disadvantages of the prior art, or
to provide a useful alternative.
SUMMARY OF THE INVENTION
[0012] According to one aspect the present invention provides an
amperometric electrochemical cell comprising a first insulating
substrate carrying a first electrode, a second insulating substrate
carrying a second electrode, said electrodes being disposed to face
each other and spaced apart by less than 500 .mu.m, and defining a
sample reservoir therebetween, wherein at least one of said
insulating substrates and the electrode carried thereon includes an
electromagnetic radiation transmissive portion in registration with
said reservoir.
[0013] Preferably, both said insulating substrates and the
electrodes thereon include a transmissive portion. Most preferably,
the transmissive portion is formed by a conductive metallic coating
on the substrate, which is of a thickness such that it is
transparent or translucent. Suitable substances for the metallic
coating include gold, indium oxide, tin oxide, or mixtures thereof.
A suitable substrate is PET.
[0014] According to a second aspect, the invention provides a
method of filling an amperometric cell comprising the steps of: a)
drawing a liquid sample into said cell comprising a first
insulating substrate carrying a first electrode, a second
insulating substrate carrying a second electrode, said electrodes
being disposed to face each other and spaced apart by less than 500
.mu.m, and defining a sample reservoir therebetween, wherein at
least one of said insulating substrates and the electrode carried
thereon includes an electromagnetic radiation transmissive portion
in registration with said reservoir; b) exposing the transmissive
portion to electromagnetic radiation; c) monitoring a property of
the electromagnetic radiation passing and/or reflected through said
transmissive portion; d) comparing said monitored property with a
predetermined value indicative of the cell being filled; and e)
continuing to draw the liquid sample into the cell until said
monitored property reaches said predetermined value.
[0015] According to a third aspect, the invention provides a method
of determining whether an amperometric cell is filled with a liquid
sample, said cell comprising a first insulating substrate carrying
a first electrode, a second insulating substrate carrying a second
electrode, said electrodes being disposed to face each other and
spaced apart by less than 500 .mu.m, and defining a sample
reservoir therebetween, wherein at least one of said insulating
substrates and the electrode carried thereon includes an
electromagnetic radiation transmissive portion in registration with
said reservoir, said method comprising the steps of: a) exposing
said transmissive portion to electromagnetic radiation; b)
monitoring a property of the electromagnetic radiation passing
and/or reflected through said transmissive portion, and; c)
comparing said monitored property with a predetermined value
indicative of the cell being filled.
[0016] Suitable forms of electromagnetic radiation include visible,
ultraviolet, infrared and laser light. Daylight is especially
preferred. The monitored property can include optical density,
wavelength, refractive index, and optical rotation.
[0017] In preferred embodiments, it is envisaged that the sample
will be blood. The electromagnetic property may be monitored inside
(for instance with a fibre optical device) or outside the cell, and
the electromagnetic radiation may pass substantially directly
through the cell or be internally reflected within the cell.
[0018] According to a fourth aspect, the invention consists in a
method for monitoring an analyte in a liquid sample comprising the
steps of: a) drawing the sample into an amperometric
electrochemical cell comprising a first insulating substrate
carrying a first electrode, a second insulating substrate carrying
a second electrode, said electrodes being disposed to face each
other and space apart by less than 500 .mu.m, and defining a sample
reservoir therebetween, wherein at least one of said insulating
substrates and the electrode carried thereon includes an
electromagnetic radiation transmissive portion in registration with
said reservoir, b) exposing the transmissive portion to
electromagnetic radiation; c) monitoring a property of the
electromagnetic radiation passing and/or reflected through said
transmissive portion; d) comparing said monitored property with a
predetermined value indicative of the cell being filled; and e)
prior to, simultaneously with or after any one of steps b) to d)
applying a potential across the electrochemical cell and measuring
the resultant current to detect the analyte.
[0019] The method of the above aspect may also further comprise the
step of: f) repeating steps a) to e) until the monitored property
reaches the predetermined value.
[0020] In one preferred embodiment, the method is repeated on
different cells, with blood as the sample and visible light the
electromagnetic radiation, until a valid measurement is obtained
for blood glucose.
[0021] In a fifth aspect, the invention provides an apparatus for
determining whether an amperometric cell according to the first
aspect is filled with a liquid sample, said apparatus comprising an
electromagnetic radiation mans adapted to expose said transmissive
portion of said cell to electromagnetic radiation, a monitoring
means adapted to monitor a property of the electromagnetic
radiation passing and/or reflected through said transmissive
portion, and a means for determining whether said monitored
property has reached a predetermined value indicative of the cell
being filled.
[0022] Preferably, said apparatus may also include means to apply
potential across the amperometric cell and detect the resultant
current. It may also include a validation manes to confirm the cell
is filled with a liquid sample.
[0023] "Comprising" as herein used is used in an inclusive sense,
that is to say in the sense of "including" or "containing". The
term is not intended in an exclusive sense ("consisting of" or
"composed of").
[0024] Light-transmissive cells intended for spectrophotometric use
are well known. However this has not previously been accomplished
in a cell wherein the only surfaces suitable for a window are
entirely covered by a metal electrode. One skilled in the art will
appreciate that whilst the embodiments of the invention are
described with respect to light transmissive conductive coatings,
such coatings may be also be transparent to some other forms of
electromagnetic radiation which are not visible to the human
eye.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention will now be particularly described by way of
example only reference to the accompanying schematic drawings
wherein:
[0026] FIG. 1 shows a cross section of a wall of a cell according
to the present invention.
[0027] FIG. 2 shows a cell according to one embodiment of the
present invention.
[0028] FIG. 3 shows a cross section of the cell in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] An embodiment of the invention will now be described by way
of example only. Referring firstly to FIG. 1, each wall of the
cell, 2, 12 comprises an insulating substrate 1, 11 carrying an
electrode 3, 13 thereon.
[0030] The embodiment is generally in accordance with the apparatus
described in our co-pending application PCT/AU96/00724 which is
incorporated herein by reference. The apparatus hereof corresponds
substantially to the apparatus described in that application with
the difference that electrode layer 3, 13 which in application
PCT/AU96/00724 was sputter coated palladium having a thickness of
100-1000 Angstrom, is replaced according to the present invention,
by a light-transmissive conductive metallic coating of a thickness
such that it is transparent or translucent. Gold, indium oxide, tin
oxide and mixtures of indium and tin oxides or other suitable
light-transmissive conductive metallic coating may be utilised.
Those skilled in the art will appreciate that transparent inorganic
and organic polymers or mixtures thereof could also be used.
Substrate 1 is also light-transmissive.
[0031] In one embodiment, the cell takes the form as shown in FIG.
2 or 3. the cell comprises a first insulating substrate 1
consisting of a Melinex.RTM. PET layer, a first electrode 3
consisting of a conductive metallic layer on substrate 1, an
adhesive layer 7, a PET spacer 9, a second adhesive layer 8, a
second electrode 13 formed as a metallic layer formed as a metallic
coating on second insulating substrate 11. Spacer 9 defines a
sample reservoir 4 having a thickness corresponding to the
thickness of the spacer 9 together with the thickness of adhesive
layers 7 and 8. Access to the sample reservoir 4 is provided at the
side edge of the cell by notches 6.
[0032] At east one of the said insulating substrates and the
electrode carried thereon includes an electromagnetic radiation
transmissive portion 20 in registration with the reservoir 4.
[0033] In preferred embodiments of the invention, a sample to be
analyzes is introduced to the cell by capillary action. The sample
is placed on contact with notch 6 and is spontaneously drawn by
capillary action into the reservoir 4, displaced air from the
reservoir 4 venting from the opposite notch 6. A surfactant may be
included in the capillary space to assist in drawing in the
sample.
[0034] The cell is provided with connection means for example edge
connectors whereby the cell may be placed into a measuring circuit.
In a preferred embodiment this is achieved by making spacer 9
shorter than cell walls 2, 12 and by making one wall 2 of shorter
length than the other 12. The forms a socket region having contact
areas electrically connected with the working and counter
electrodes of a sensing apparatus. A simple tongue plug having
corresponding engaging conduct surfaces can then be used for
electrical connection. Connectors of other form may be devised.
[0035] Chemicals for use in the cell may be supported on the cell
electrodes or walls, may be supported on an independent support
contained within the cell or may be self-supporting.
[0036] In use, when the cell is filled with the liquid sample, e.g.
blood, a film of the sample covers the inside of the transmissive
portion 20 formed by substrate 1, 11 and metal electrode 3, 13 over
reservoir 4, thereby indicating to the user when the cell is
adequately filled, and clearly differentiating a used sensor from
an unused one.
[0037] Apart from simple visual inspection, a user can also monitor
the filling of the cell by exposing the electromagnetic radiation
transmissive portion 20 to electromagnetic radiation such as
infra-red, ultraviolet light or laser light and monitoring a
property of the electromagnetic radiation (for example, optical
density, color or optical rotation) as it exits the cell either by
another transmissive portion on the opposite side of the reservoir,
or as a result of internal reflection within the reservoir.
[0038] A particular embodiment of an apparatus suitable for
carrying out the inventive method is hereby described. The
apparatus has means for holding and orienting a cell according to
the present invention and exposing the electromagnetic portion of
the cell to allow an electromagnetic radiation source, e.g. a light
beam, to enter the reservoir.
[0039] Optionally, the apparatus may also be equipped with means
for automatically placing the cells into the said holding
means.
[0040] The path of the light beam is substantially linear, and it
exits the cell either via another transparent portion of the cell,
or is reflected back through the first mentioned transmissive
portion. The electromagnetic radiation leaving the cell is
monitored by an appropriate detector. This detector monitors a
property of the electromagnetic radiation leaving the cell for
comparison with a predetermined value which is indicative of the
cell being filled, for example if the cell is filled with blood up
to or above the transmissive portion, a reduction in optical
density will be detected. If the cell is empty or only partially
filled to this point, the optical density will remain high but will
reduce as the reservoir is filled until it reaches the
predetermined value indicating a full cell. It will be appreciated
that the apparatus could be made to continue filling until the cell
was satisfactorily filled, by means of a feedback system. The
apparatus could also be adapted so that it performed the necessary
electrochemical measurements on the cell, thus reducing the need
for excessive sample movement.
[0041] The apparatus preferably also includes a validation means
which is triggered when it is determined that the cell is full and
the sensing measurement can be accepted as valid.
[0042] As will be apparent to those skilled in the art from the
teaching hereof the invention may be embodied in other forms
without departing herefrom.
* * * * *