CA1155316A - Electrochemical sensing apparatus with in situ calibration and method of making same - Google Patents
Electrochemical sensing apparatus with in situ calibration and method of making sameInfo
- Publication number
- CA1155316A CA1155316A CA000372600A CA372600A CA1155316A CA 1155316 A CA1155316 A CA 1155316A CA 000372600 A CA000372600 A CA 000372600A CA 372600 A CA372600 A CA 372600A CA 1155316 A CA1155316 A CA 1155316A
- Authority
- CA
- Canada
- Prior art keywords
- opening
- tube
- layer
- chamber
- sensor assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/14542—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring blood gases
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1468—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using chemical or electrochemical methods, e.g. by polarographic means
- A61B5/1473—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using chemical or electrochemical methods, e.g. by polarographic means invasive, e.g. introduced into the body by a catheter
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1495—Calibrating or testing of in-vivo probes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/4163—Systems checking the operation of, or calibrating, the measuring apparatus
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/4163—Systems checking the operation of, or calibrating, the measuring apparatus
- G01N27/4165—Systems checking the operation of, or calibrating, the measuring apparatus for pH meters
Abstract
ABSTRACT OF THE DISCLOSURE An in vivo electrochemical monitoring device is formed by a catheter-like member which terminates in a closed end having a wall with a fixed opening to admit fluid to be tested, such as blood in an artery. An electrochemical sensor, such as an ion sensitive field effect transistor (ISFET) device for monitoring the con-centration of a particular ion in blood, is mounted inside the tube at a fixed location below the opening preferably a larger sensing chamber. An infusion channel in the tube is arranged to flood the sensor with a fluid of known chemical properties so that the sensor output can be calibrated. Under pressure the calibration fluid expels the test fluid out of the tube or chamber via the fixed opening. A method of con-structing a suitable chamber on an ISFET wafer is also disclosed.
Description
BACKGROUND OF THE INVENTION
The invention relates generally to electrical sensor assemblies used in in vivo measurement of chemi-cal parameters in a test fluid, such as blood in an axtery, and in particular to calibration systems for chemically sensitive electrodes used in catheters, for example.
Electrochemical sensing devices, such as ion sensitive field effect transistors (ISFETS) are finding numerous applications in measuring the chemical proper-ties of fluids. One such application has been the use of an ISFET device in conjunction with an ion selective membrane for performing continuous in vivo measurement o the concentration of a particular ion in the blood.
The sensor is mounted on a catheter which is fed into an artery via a conventional catheter introducer. While extremely sen~itive to variations in ion concentration, the ISFET device, like other electrochemical sensors, suffers from drift which seriously undermines the accuracy of the readings. Frequent recalibration of the output device connected to the sensor essentially removes these inaccuracies. One method of calibration which has been used in the past is to draw a sample of blood, for example, from a separate arterial puncture or by means of a syringe connected to a side arm assembly of the catheter containing the sensor and actually measuring the electrochemical activity of the ion of interest using standard laboratory techniques.
A]ternatively, the sensor itself may be rernoved for in vitro calibration in a fluid of known exact ion con-centration. The ideal system, however, would per~orm recalibra-tion in vivo without laboratory analysis.
Une system which has been proposed for per-forming in vivo calibration of an electrochemical sensor is referred to in U.S. Patent No. 4,016,866 to Lawton, involving a retractable sensing electrode carried by an insertion catheter. To perform measurements, the electrode is extended axially out of the insertion catheter. For xecalibration, the sensing electrode is retracted into the insertion catheter to an infusion chamber where it i8 contacted with calibrating solution furnished by a drip line in which a reference electrode also contacts the calibrating solution. Following calibration the sensor i5 protracted to the exterior measurement position. The electrode must be accurately aligned with an opening in the end of the insertion catheter and the opening must be large enough to allow the electrode to freely pass through the opening in either direction. Thus the opening must be larger than the electrode. Moreover, the need for axial retrac-tability requires a rather complicated mechanism involving sealing glands and guard tubes to maintain a sliding seal. The mechanical action of the sensor places certain constraints on the mounting arrangement 1 1~S316 of the ~ensor and generally increases the ri~k of mechanical damage to the sensor and electrical connec-tions to the sensor. secau~e of the ~ize of the opening i~ the insertion catheter, there i8 also a pos~ibility of blood flowing into the catheter-and mixing with the calibration liquid.
SUMMARY OF THE INVENTION
-The general object of the invention is to pro-vide a ~tructural arrangement for an electrochemical ~ensor such as an ISFET device in a catheter-like tube in which the sensor remains at a fixed location in a chamber which functions both as a calibration chamber and as a test fluid chamber. In accordance with the invention, an in vivo electrochemical monitoring device is formed by a catheter-like member which terminates in a closed end having a wall with a fixed opening to admit fluid to be tested, such as blood in an artery. An electrochemical ~en60r, such as an ISFET device for monitoring the concentration of a particular ion in blood, is mounted insiae the tube in a fixed location below the opening, preferably in a larger sensing chamber. An infusion channel in the tube is arranged to flood the sensor at its fixed location with a fluid of known chemical properties for calibration. Under pressure, the calibration fluid expels the test fluid out of the tube or chamber yia the fixed opening.
Maintaining a positive flow of calibration fluid at a controlled pressure keeps the test fluid out of contact with the sensor while bathing the sensor in the known ion concentration.
According to a further aspect of the inven-tion, a method of constructing a suitable chamber on an ISFET wafer includes applying a first layer of soluble material, covering the first layer with a second layer of another material, making a hole through the second layer and removing the first layer entirely by intro-ducing solvent through the hole in the second layer.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a diagramatic longitudinal sectionalview of a closed tubular catheter having a chemically sensitive sensor bonded to the sidewall.
Fig. 2 is a diagramatic longitudinal sectional view of a bilumen tubular catheter in which the sensor is mounted on a common partition.
Fig. 3 is a cross-sectional view taken generally at the location of the sensor of Fig. 2.
Fig. 4 is a plan view of the end of a tubular catheter according to the invention having a separate infusion tube.
Fig. 5 is a diagramatic longitudinal sectional view of the catheter of Fig. 4.
Fig. 6 is a diagramatic cross-sectional view of the tubular catheter and sensor of Fig. 4.
Fig. 7 is a diagramatic sectional view illustrating the construction of a calibration compart-ment on an ISFET wafer.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
In the following examples the electrochemical sensor comprises an ISFET with a source and drain electrode and an Ag/AgCl reference electrode. In Fig.
1, a closed tubular catheter 10 made of flexible synthe-tic plastic material has a small opening 11 formed in the sidewall thereof which is sealed off on the inside of the catheter 10 by an ISFET device 9 which is bonded to the inner wa~l of the catheter by means of a suitable adhe~ive, for example. The catheter 10, over a limited circumferential extent, is double-walled to form an infusion channel 12 which leads to the opening 11. The end portion 13 of the outer wall of the channel 12 extends part way over the opening 11 so as to constrict the opening 11 at the outer surface of the catheter 10.
The compartment or chamber formed by the opening 11, end portion 13 of the wall and the ISFET 9 functions as a calibration compartment for the ISFET. When calibration liquid of a known chemical composition is forced through channel 12, the liquid, for example blood, present in the opening or chamber 11 will be expelled. Thus opening 11 will become entirely filled with calibration 1~5S316 liquid. While the supply of calibration liquid i5 being nlaintained under controlled pressure, the ISFET electri-cal output can be calibrated. When the flow of calibra-tion liquid is ~topped or reversed, the opening 11 functioniny as a small compartment refills with blood and rneasurement can be continued. The calibration step can be automatically cycled if desired.
In the embodiment of Fig. 2, the catheter 14 has two lumina 15 and 16 separated by a common partition 17. Adjacent to the end of catheter 14, a tapered opening 18 is formed in the catheter wall. Under the opening 18, the sensor 19 with ISFET 20 and Ag/AgCl reference electrode 21 with respective electrical leads 22 and 23, are mounted in partition 17. During measure-ment, channel 15, formed by the lumina in communication with opening 1~, contains blood which is in contact with the sensor 19. By supplying calibration liquid through channel 15, the blood present therein is expelled and the sensor can be calibrated. When the supply of calibration liquid is discontinued, blood will again flow into channel 15 and the unit will return to the measuring phase. The catheter end 24 may take the form of a loose cap which, after sensor 19 has been installed, can be placed in position on the partition and secured, for example, with adhesive.
In Figs. 4 and 5, an ISFET 31 is mounted in an opening in the wall of the catheter 41. ISFET 31 comprises source electrode 37, drain electrode 38 and bulk contact 39, with leads 35. The ion-sensitive por-tion of the ISFET is housed in a chamber 34 formed by the ISFET and adjacent catheter wall, which also accom-rnodates the Ag/AgCl reference electrode 36. An aperture 40 i8 formed throuyh the bulk of the ISFET terminating in chamber 34, to which infusion tube 33 is connected for supplying calibration liquid to the chamber. At the top the chamber 34 has an aperture 42 for incosning blood or outgoing calibration liquid.
During the measuring phase, chamber 34 is entirely filled with blood. In order to switch over to calibration of t:he ion-sensitive electrode, a stream of calibration liquid is supplied to chamber 34 in excess of blood pressure. If desired, the pressure driving the calibration liquid may be adjusted automatically as a function of blood pressure. The blood present in chamber 34 is expelled through aperture 42. So long as adequate pressure i8 maintained, calibration liquid will flow in direction A, as indicated in Fig. 6, out of the opening 42. When, after the calibration, a reduced pressure, or at any rate no excess pressure, is established in chamber 34, the chamber will again be entirely filled with blood, and measurement can be resumed. Calibration and measurement can be performed automatically in pre-programmed repetition.
Tube 33 is not an essential component. The calibration liquid can be supplied through catheter tube 41 provided that the leads 35 are suitably insulated.
The chamber for the calibration compartment can be formed directly on an ISFET wafer using the same integrated circuit technology that is used for making the ISFET itself. A few additional step~ are required for making the chamber. A~ shown in Fig. 7, the ion-sensitive portion (the gate) with the source electrode 51 and the drain electrode 52 of the ISFET 50 are covered with a temporary protective layer 53 of a material that can easily be dissolved or etched.
Subsequently a layer 54, preferably of a conductive material, e.g., a metal or polysilicon, is applied on top of and around layer 53. Next a mask 55 having an opening 56 therein is laid on top of conductive layer 54, and through opening 56 an etching agent is supplied for etching an opening 57 in layer 54. Finally, a solvent for layer 53 is supplied through opening 57, and layer 53 is dissolved and removed, leaving an empty chamber.
Although an in~ulating material may be selected for layer 54, the use of a conductor is pre-ferred because the chamber formed therein functions as a Faraday cage.
It is of advantage, after forming the chamber, to cover the unit of Fig. 7 with a layer which promotes its biological compatability without unduly affecting its response period. A preferred material for this pur-pose is a hydrogel material.
The chamber 3~ of Figs. 4-6 may be formed in the rnanner of Fig. 7 or by fixing a separately manufac-tured apertured charnber wall to the ISFET with adhesive, for example.
The utility and applicability of the invention is not limited to ISFET devices. The possibility of neutralizing the effect of the drift phenomena by con-tinual recalibration in a standard medium in acalibration/test chamber might also be beneficial with other types of electrochemical sensors.
Among the many advantages of the invention is the u~e of a single location and single chamber for both measuring and calibrating the sensor whereby, without mechanical intervention, the contents of the chamber are solely determined by the pressure applied to the infu-sion channel, thus facilitating an automatic calibration cycle. The simple construction of the sensing apparatus according to the invention results in an inexpensively constructed reliable instrument. In addition, the Faraday cage effect of forming the calibration chamber in conductive material reduces the sensitivity of the instrument to external and internal (bio) sources of electrical interference. The constant access to infu-sion fluids enhances the biological compatability of the ~ 155316 sensor by reyularly washing it, for example, with heparinated liquid. In addition, the construction enables automatic testing of electrical sensitivity via a pulse on the reference electrode which is in a fixed electrolytic trough arrangement.
The foregoing description and drawings are intended to be illustrative not restrictive, the scope of the invention being indicated by the appended claims.
The invention relates generally to electrical sensor assemblies used in in vivo measurement of chemi-cal parameters in a test fluid, such as blood in an axtery, and in particular to calibration systems for chemically sensitive electrodes used in catheters, for example.
Electrochemical sensing devices, such as ion sensitive field effect transistors (ISFETS) are finding numerous applications in measuring the chemical proper-ties of fluids. One such application has been the use of an ISFET device in conjunction with an ion selective membrane for performing continuous in vivo measurement o the concentration of a particular ion in the blood.
The sensor is mounted on a catheter which is fed into an artery via a conventional catheter introducer. While extremely sen~itive to variations in ion concentration, the ISFET device, like other electrochemical sensors, suffers from drift which seriously undermines the accuracy of the readings. Frequent recalibration of the output device connected to the sensor essentially removes these inaccuracies. One method of calibration which has been used in the past is to draw a sample of blood, for example, from a separate arterial puncture or by means of a syringe connected to a side arm assembly of the catheter containing the sensor and actually measuring the electrochemical activity of the ion of interest using standard laboratory techniques.
A]ternatively, the sensor itself may be rernoved for in vitro calibration in a fluid of known exact ion con-centration. The ideal system, however, would per~orm recalibra-tion in vivo without laboratory analysis.
Une system which has been proposed for per-forming in vivo calibration of an electrochemical sensor is referred to in U.S. Patent No. 4,016,866 to Lawton, involving a retractable sensing electrode carried by an insertion catheter. To perform measurements, the electrode is extended axially out of the insertion catheter. For xecalibration, the sensing electrode is retracted into the insertion catheter to an infusion chamber where it i8 contacted with calibrating solution furnished by a drip line in which a reference electrode also contacts the calibrating solution. Following calibration the sensor i5 protracted to the exterior measurement position. The electrode must be accurately aligned with an opening in the end of the insertion catheter and the opening must be large enough to allow the electrode to freely pass through the opening in either direction. Thus the opening must be larger than the electrode. Moreover, the need for axial retrac-tability requires a rather complicated mechanism involving sealing glands and guard tubes to maintain a sliding seal. The mechanical action of the sensor places certain constraints on the mounting arrangement 1 1~S316 of the ~ensor and generally increases the ri~k of mechanical damage to the sensor and electrical connec-tions to the sensor. secau~e of the ~ize of the opening i~ the insertion catheter, there i8 also a pos~ibility of blood flowing into the catheter-and mixing with the calibration liquid.
SUMMARY OF THE INVENTION
-The general object of the invention is to pro-vide a ~tructural arrangement for an electrochemical ~ensor such as an ISFET device in a catheter-like tube in which the sensor remains at a fixed location in a chamber which functions both as a calibration chamber and as a test fluid chamber. In accordance with the invention, an in vivo electrochemical monitoring device is formed by a catheter-like member which terminates in a closed end having a wall with a fixed opening to admit fluid to be tested, such as blood in an artery. An electrochemical ~en60r, such as an ISFET device for monitoring the concentration of a particular ion in blood, is mounted insiae the tube in a fixed location below the opening, preferably in a larger sensing chamber. An infusion channel in the tube is arranged to flood the sensor at its fixed location with a fluid of known chemical properties for calibration. Under pressure, the calibration fluid expels the test fluid out of the tube or chamber yia the fixed opening.
Maintaining a positive flow of calibration fluid at a controlled pressure keeps the test fluid out of contact with the sensor while bathing the sensor in the known ion concentration.
According to a further aspect of the inven-tion, a method of constructing a suitable chamber on an ISFET wafer includes applying a first layer of soluble material, covering the first layer with a second layer of another material, making a hole through the second layer and removing the first layer entirely by intro-ducing solvent through the hole in the second layer.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a diagramatic longitudinal sectionalview of a closed tubular catheter having a chemically sensitive sensor bonded to the sidewall.
Fig. 2 is a diagramatic longitudinal sectional view of a bilumen tubular catheter in which the sensor is mounted on a common partition.
Fig. 3 is a cross-sectional view taken generally at the location of the sensor of Fig. 2.
Fig. 4 is a plan view of the end of a tubular catheter according to the invention having a separate infusion tube.
Fig. 5 is a diagramatic longitudinal sectional view of the catheter of Fig. 4.
Fig. 6 is a diagramatic cross-sectional view of the tubular catheter and sensor of Fig. 4.
Fig. 7 is a diagramatic sectional view illustrating the construction of a calibration compart-ment on an ISFET wafer.
DESCRIPTION OF THE PREFERRED EMBODIME~TS
In the following examples the electrochemical sensor comprises an ISFET with a source and drain electrode and an Ag/AgCl reference electrode. In Fig.
1, a closed tubular catheter 10 made of flexible synthe-tic plastic material has a small opening 11 formed in the sidewall thereof which is sealed off on the inside of the catheter 10 by an ISFET device 9 which is bonded to the inner wa~l of the catheter by means of a suitable adhe~ive, for example. The catheter 10, over a limited circumferential extent, is double-walled to form an infusion channel 12 which leads to the opening 11. The end portion 13 of the outer wall of the channel 12 extends part way over the opening 11 so as to constrict the opening 11 at the outer surface of the catheter 10.
The compartment or chamber formed by the opening 11, end portion 13 of the wall and the ISFET 9 functions as a calibration compartment for the ISFET. When calibration liquid of a known chemical composition is forced through channel 12, the liquid, for example blood, present in the opening or chamber 11 will be expelled. Thus opening 11 will become entirely filled with calibration 1~5S316 liquid. While the supply of calibration liquid i5 being nlaintained under controlled pressure, the ISFET electri-cal output can be calibrated. When the flow of calibra-tion liquid is ~topped or reversed, the opening 11 functioniny as a small compartment refills with blood and rneasurement can be continued. The calibration step can be automatically cycled if desired.
In the embodiment of Fig. 2, the catheter 14 has two lumina 15 and 16 separated by a common partition 17. Adjacent to the end of catheter 14, a tapered opening 18 is formed in the catheter wall. Under the opening 18, the sensor 19 with ISFET 20 and Ag/AgCl reference electrode 21 with respective electrical leads 22 and 23, are mounted in partition 17. During measure-ment, channel 15, formed by the lumina in communication with opening 1~, contains blood which is in contact with the sensor 19. By supplying calibration liquid through channel 15, the blood present therein is expelled and the sensor can be calibrated. When the supply of calibration liquid is discontinued, blood will again flow into channel 15 and the unit will return to the measuring phase. The catheter end 24 may take the form of a loose cap which, after sensor 19 has been installed, can be placed in position on the partition and secured, for example, with adhesive.
In Figs. 4 and 5, an ISFET 31 is mounted in an opening in the wall of the catheter 41. ISFET 31 comprises source electrode 37, drain electrode 38 and bulk contact 39, with leads 35. The ion-sensitive por-tion of the ISFET is housed in a chamber 34 formed by the ISFET and adjacent catheter wall, which also accom-rnodates the Ag/AgCl reference electrode 36. An aperture 40 i8 formed throuyh the bulk of the ISFET terminating in chamber 34, to which infusion tube 33 is connected for supplying calibration liquid to the chamber. At the top the chamber 34 has an aperture 42 for incosning blood or outgoing calibration liquid.
During the measuring phase, chamber 34 is entirely filled with blood. In order to switch over to calibration of t:he ion-sensitive electrode, a stream of calibration liquid is supplied to chamber 34 in excess of blood pressure. If desired, the pressure driving the calibration liquid may be adjusted automatically as a function of blood pressure. The blood present in chamber 34 is expelled through aperture 42. So long as adequate pressure i8 maintained, calibration liquid will flow in direction A, as indicated in Fig. 6, out of the opening 42. When, after the calibration, a reduced pressure, or at any rate no excess pressure, is established in chamber 34, the chamber will again be entirely filled with blood, and measurement can be resumed. Calibration and measurement can be performed automatically in pre-programmed repetition.
Tube 33 is not an essential component. The calibration liquid can be supplied through catheter tube 41 provided that the leads 35 are suitably insulated.
The chamber for the calibration compartment can be formed directly on an ISFET wafer using the same integrated circuit technology that is used for making the ISFET itself. A few additional step~ are required for making the chamber. A~ shown in Fig. 7, the ion-sensitive portion (the gate) with the source electrode 51 and the drain electrode 52 of the ISFET 50 are covered with a temporary protective layer 53 of a material that can easily be dissolved or etched.
Subsequently a layer 54, preferably of a conductive material, e.g., a metal or polysilicon, is applied on top of and around layer 53. Next a mask 55 having an opening 56 therein is laid on top of conductive layer 54, and through opening 56 an etching agent is supplied for etching an opening 57 in layer 54. Finally, a solvent for layer 53 is supplied through opening 57, and layer 53 is dissolved and removed, leaving an empty chamber.
Although an in~ulating material may be selected for layer 54, the use of a conductor is pre-ferred because the chamber formed therein functions as a Faraday cage.
It is of advantage, after forming the chamber, to cover the unit of Fig. 7 with a layer which promotes its biological compatability without unduly affecting its response period. A preferred material for this pur-pose is a hydrogel material.
The chamber 3~ of Figs. 4-6 may be formed in the rnanner of Fig. 7 or by fixing a separately manufac-tured apertured charnber wall to the ISFET with adhesive, for example.
The utility and applicability of the invention is not limited to ISFET devices. The possibility of neutralizing the effect of the drift phenomena by con-tinual recalibration in a standard medium in acalibration/test chamber might also be beneficial with other types of electrochemical sensors.
Among the many advantages of the invention is the u~e of a single location and single chamber for both measuring and calibrating the sensor whereby, without mechanical intervention, the contents of the chamber are solely determined by the pressure applied to the infu-sion channel, thus facilitating an automatic calibration cycle. The simple construction of the sensing apparatus according to the invention results in an inexpensively constructed reliable instrument. In addition, the Faraday cage effect of forming the calibration chamber in conductive material reduces the sensitivity of the instrument to external and internal (bio) sources of electrical interference. The constant access to infu-sion fluids enhances the biological compatability of the ~ 155316 sensor by reyularly washing it, for example, with heparinated liquid. In addition, the construction enables automatic testing of electrical sensitivity via a pulse on the reference electrode which is in a fixed electrolytic trough arrangement.
The foregoing description and drawings are intended to be illustrative not restrictive, the scope of the invention being indicated by the appended claims.
Claims (15)
1. Electrochemical sensing apparatus with in situ calibration, comprising a closed tube having a wall with a fixed opening to admit fluid to be tested, an electrochemical sensor assembly affixed inside said tube below said opening, means defining an infusion channel in said tube for flooding said sensor assembly with a known fluid for calibration during which the fluid to be tested is temporarily expelled through said opening.
2. The apparatus of claim 1, wherein said sensor assembly is affixed to the inside wall of said tube covering said opening to define therewith a sensing chamber.
3. The apparatus of claim 2, wherein said infusion channel is formed in the interior of the sidewall of said tube.
4. The apparatus of claim 3, wherein said sensor assembly is substantially flush with the inside wall surrounding said opening.
5. The apparatus of claim 4, wherein the outer portion of the wall defining said infusion channel is extended to partially overlie said opening thus forming at the surface of the tube a threshold passage to said opening of reduced cross-sectional area relative to the subjacent portion of said opening.
6. The apparatus of claim 2, wherein said infusion channel is formed by a separate inner tube extending axially through said closed tube and passing sealingly through said sensor assembly into fluid communication with said sensing chamber.
7. The apparatus of claim 2, further comprising a partition inside said tube arranged to divide the interior thereof into two lumens, the one lumen in communication with said opening forming said infusion channel, said sensor assembly being affixed in said partition so as to be operatively exposed to said one lumen.
8. The apparatus of claim 1, 2 or 7, wherein said opening is tapered with the portion of reduced cross-sectional area lying closer to the outer surface of the tube.
9. The apparatus of claim 2, wherein said chamber is defined by an electrically conductive material.
10. The apparatus of claim 1, wherein said sensor assembly is larger than said opening.
11. A method of making an electrochemical sensing cell, comprising the steps of making a wafer comprising an ISFET with a chemi-cally sensitive surface, applying over said chemically sensitive surface a first layer of a soluble material, applying a second layer of material on top of and beyond the periphery of said first layer, defining an opening in said second layer above said chemically sensitive surface, removing said first layer by introducing a solvent through said opening to dissolve said first layer, thus forming a sensing chamber.
12. The method of claim 11, wherein said second layer is electrically conductive.
13. The method of claim 11, further comprising the step of forming an infusion through-hole through the wafer leading into the site of said sensing chamber.
14. The method of claim 11, wherein said opening formed in said second layer is narrower than said chamber formed by removing said first layer.
15. The method of claim 11, further comprising the step of covering said cell with a layer of hydrogel to promote biological compatibility.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000432579A CA1173109A (en) | 1980-03-10 | 1983-07-15 | Electrochemical sensing cell with in situ calibration |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL80.01420 | 1980-03-10 | ||
| NL8001420A NL8001420A (en) | 1980-03-10 | 1980-03-10 | ELECTRODE COMPOSITIVE COMPOSITE, FOR AN ELECTROCHEMICAL MEASUREMENT, IN PARTICULAR AN ISFET-CONSTRUCTED COMPOSITION, AND METHOD FOR MANUFACTURING THE ASSEMBLY. |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000432579A Division CA1173109A (en) | 1980-03-10 | 1983-07-15 | Electrochemical sensing cell with in situ calibration |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1155316A true CA1155316A (en) | 1983-10-18 |
Family
ID=19834957
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000372600A Expired CA1155316A (en) | 1980-03-10 | 1981-03-09 | Electrochemical sensing apparatus with in situ calibration and method of making same |
Country Status (5)
| Country | Link |
|---|---|
| US (2) | US4478222A (en) |
| EP (1) | EP0036171B1 (en) |
| CA (1) | CA1155316A (en) |
| DE (1) | DE3161349D1 (en) |
| NL (1) | NL8001420A (en) |
Families Citing this family (126)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL8001420A (en) * | 1980-03-10 | 1981-10-01 | Cordis Europ | ELECTRODE COMPOSITIVE COMPOSITE, FOR AN ELECTROCHEMICAL MEASUREMENT, IN PARTICULAR AN ISFET-CONSTRUCTED COMPOSITION, AND METHOD FOR MANUFACTURING THE ASSEMBLY. |
| US4432366A (en) * | 1981-11-27 | 1984-02-21 | Cordis Corporation | Reference electrode catheter |
| NL8200007A (en) * | 1982-01-05 | 1983-08-01 | Electrofact B V | ELECTRODE FOR ESTABLISHING CONTACT WITH A LIQUID SUCH AS A REDOX ELECTRODE AND REDOX MEASUREMENT EQUIPMENT PROVIDED WITH SUCH ELECTRODE. |
| US4643192A (en) * | 1982-03-22 | 1987-02-17 | Regents Of The University Of Michigan | Hollow viscus tonometry |
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-
1980
- 1980-03-10 NL NL8001420A patent/NL8001420A/en not_active Application Discontinuation
-
1981
- 1981-03-09 CA CA000372600A patent/CA1155316A/en not_active Expired
- 1981-03-10 EP EP81101754A patent/EP0036171B1/en not_active Expired
- 1981-03-10 US US06/242,351 patent/US4478222A/en not_active Expired - Lifetime
- 1981-03-10 DE DE8181101754T patent/DE3161349D1/en not_active Expired
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1984
- 1984-03-09 US US06/587,819 patent/US4534825A/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| US4478222A (en) | 1984-10-23 |
| EP0036171B1 (en) | 1983-11-09 |
| US4534825A (en) | 1985-08-13 |
| NL8001420A (en) | 1981-10-01 |
| EP0036171A1 (en) | 1981-09-23 |
| DE3161349D1 (en) | 1983-12-15 |
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