US20050258037A1 - Electrochemical sensor - Google Patents

Abstract

A sensor (10,110) is provided for determination of various concentrations of one or more components within a fluid sample. The sensor (10,110) includes an injection molded body (12,112), at least two electrodes (30,31,32,130,131,132), an enzyme (57,157), and, if desired, an electron transfer mediator. The body includes a reaction zone (24,124) for receiving a fluid sample. The electrodes (30,31,32,130,131,132) are at least partially embedded within the plastic body (12,112) and extend into the reaction zone (24,124). Also contained within the reaction zone is an enzyme (57,157) capable of catalyzing a reaction involving a compound within the fluid sample.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of co-pending prior U.S. application Ser. No. 09/820,372 filed Mar. 23, 2001.
TECHNICAL FIELD
• The present invention generally relates to electrochemical sensors and, in particular, to molded electrochemical sensors for detection or measurement of analytes in test samples, such as fluids and dissolved solid materials, and the methods of making and using these sensors.
BACKGROUND OF THE INVENTION
• Electrochemical sensors are used to determine the concentrations of various analytes in testing samples such as fluids and dissolved solid materials. For instance, electrochemical sensors have been made for measuring glucose in human blood. Such sensors have been used by diabetics and health care professionals for monitoring blood glucose levels. The sensors are usually used in conjunction with a meter, which measures light reflectance, if the strip is designed for photometric detection of a die, or which measures some electrical property, such as electrical current, if the strip is designed for detection of an electroactive compound.
• Typically, electrochemical sensors are manufactured using an electrically insulating base upon which conductive inks such as carbon and silver are printed by screen printing to form conductive electrode tracks or thin strips of metal are unrolled to form the conductive electrode tracks. The electrodes are the sensing elements of the sensor generally referred to as a transducer. The electrodes are covered with a reagent layer comprising a hydrophilic polymer in combination with an oxidoreductase or a dehydrogenase enzyme specific for the analyte. Further, mounted over a portion of the base and the electrodes is an insulating layer.
• Precision and accuracy of electrochemical measurements to a great extent rely on the reproducibility of the electrode surface area on a microscopic scale. Variations in the morphology of the electrode can result in very significant changes in the electrochemical signal readout. Screen-printing has made significant in-roads in the production of sensors for determining glucose. The wide use of screen-printing stems from the ability to mass-produce relatively inexpensive sensors. The use of metal strips unrolled from large rolls has also been employed to mass produce such sensors.
• While many advances have been made in the field of screen printing and conductive ink production, the technology still suffers from poor reproducibility of the electrode surface area, dimensional variations, thickness variations, micro-cracks, and shrinkage due to the repetitive and high temperature curing processes involved in using film printing technology. Loss of solvent during printing is another factor that leads to variations in the thickness of electrodes.
• Sensor development using printing technology requires several passes of different conductive inks demanding different screens. Slight variations in positioning the screens can lead to substantial errors in IR drop and the applied potentials. Wear and tear of these screens is another source of error. Also, sensor strip production by screen printing suffers from a high level of raw material waste. Generally, for every gram of ink used, there is a gram of ink wasted. Manufacture of such sensors also involves several lamination processes that add to the production complexity and cost of the final product.
SUMMARY OF THE INVENTION
• The present invention is an electrochemical sensor that provides for the determination of various analyte concentrations in a testing sample such as fluids and dissolved solid materials. The sensor is designed to facilitate production in large quantities using reliable and cost effective injection molding manufacturing methods. The present invention includes an injection molded plastic strip or body, at least two electrodes, an enzyme, and if desired, an electron transfer mediator. The body includes a cavity or reaction zone for receiving a fluid sample. The electrodes are at least partially embedded within the plastic body and extend into the reaction zone where they are exposed to a test sample. Also contained within the reaction zone is an enzyme capable of catalyzing a reaction involving a compound within the fluid sample.
• Specifically, the device cooperates with an electronic meter capable of measuring the difference between the electrical properties of the electrically conductive electrodes within the device. The device, a sensor, includes at least two, and preferably three, spaced apart electrically conductive electrodes, a body having two ends of insulative material molded about and housing the electrodes, means for connecting the meter to the housing, means for receiving a fluid sample, and means for treating one or more electrodes with one or more chemicals to change the electrical properties of the treated electrodes upon contact with the fluid sample. One end of the housing has the means for connecting the meter and the opposite end of the housing has the means for receiving the fluid sample. The means for connecting the meter is a plug formed in the housing exposing the electrodes outside the body.
• The sensor is molded and can be a single, unitary piece or two pieces. In the two piece construction, an end cap is attached to the body. In the single piece construction, the body pivots about a hinge and connects onto itself. Protuberances formed in a portion of the body cooperate with troughs to ensure proper alignment.
• A capillary inlet is constructed at one end of the sensor to draw the fluid sample into the body upon contact with the fluid sample. The capillary inlet is molded into the end of the body and is in communications with a reaction zone. This reaction zone is a channel formed in the body about the electrodes and is adapted for reacting with the fluid drawn into the body by the capillary force. While the reaction zone may be formed above or below the electrodes, the preference has been to construct it above the electrodes. The capillary has a vent for relieving pressure.
• As noted, the electrodes are molded into the plastic. In one embodiment, the electrodes are conductive wires. In another embodiment, the electrodes are constructed from a metal plate. The electrodes may be coated with a different conductive material to enhance their performance.
• Apertures are formed in the body of the sensor to permit the holding of the electrodes during the molding process. Apertures may also be formed in the body to chemically treat one or more electrodes in the reaction zone before or after the molding process. Adding chemicals (e.g., reagents with and without enzymes) changes the electrical properties of the treated electrodes upon contact with the fluid sample. In the preferred embodiment, the enzyme is applied to the outer surface of one of the electrodes. An antibody may also be applied to another of the electrodes. An electron mediator may further be applied to the outer surface of one or more of the electrodes.
• The methods of making and using the electrochemical sensor are also disclosed. The method of making the device includes the steps of positioning at least two spaced apart electrically conductive electrodes in a mold, before or after molding treating at least one of the electrodes with one or more chemicals to change the electrical properties of the treated electrode upon contact with a fluid sample, and molding a body of insulative material with two ends around the electrodes with one end having therein means for receiving a fluid sample. As before, the body is molded in two pieces, with a body and end cap for attaching to one another after the molding is completed, or in a single, unitary piece.
BRIEF DESCRIPTION OF THE DRAWINGS
• In the accompanying drawings forming part of the specification, and in which like numerals are employed to designate like parts throughout the same,
• FIG. 1 is an enlarged top plan view of a first embodiment of an electrochemical sensor made in accordance with the teachings of the present invention;
• FIG. 2 is a sectional end view of the electrochemical sensor ofFIG. 1 taken along plane2-2;
• FIG. 3 is a sectional end view of the electrochemical sensor ofFIG. 1 taken along plane3-3;
• FIG. 4 is a sectional end view of the electrochemical sensor ofFIG. 1 taken along plane4-4;
• FIG. 5 is a sectional end view of the electrochemical sensor ofFIG. 1 taken along plane5-5;
• FIG. 6 is a sectional side view of the electrochemical sensor ofFIG. 1 taken along plane6-6;
• FIG. 7 is an enlarged top plan view of a second embodiment of an electrochemical sensor made in accordance with the teachings of the present invention;
• FIG. 8 is an end elevation view of the electrochemical sensor ofFIG. 7;
• FIG. 9 is a side elevation view of the electrochemical sensor ofFIG. 7;
• FIG. 10 is a bottom plan view of the electrochemical sensor ofFIG. 7;
• FIG. 11 is a sectional end view of the electrochemical sensor ofFIG. 7 taken along plane11-11; and,
• FIG. 12 is a sectional end view of the electrochemical sensor ofFIG. 7 taken along plane12-12.
DETAILED DESCRIPTION
• While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.
The First Embodiment
• Referring toFIGS. 1-6, an electrochemical sensor in accordance with the present invention, first embodiment, is depicted.FIG. 1 shows thesensor10 as though it were made out of clear plastic, permitting one to look inside it. As discussed herein, the internal components and hidden external components would not normally be visible looking down on thesensor10. This rendition would be similar to a view taken along plane x-x inFIG. 2.
• The sensor or test strip of thefirst embodiment10 includes an injection moldedplastic body12, opaque or preferably translucent, having a meter attachment end or plugend14 and a fluidsample receiving end16. The body has abottom surface13, atop surface15 and a taperedportion20 connecting a firsttop surface15ato a secondtop surface15b,the first top surface being lower than the second top surface, and a thirdtop surface15c,also lower than the second top surface. Thebody12 contains three spaced apartelectrodes30,31,32. Theplug end14 of thebody12 includes a pair of tapered side edges18,19 and a wedge shapedtop portion20. The tapered side edges18,19 facilitate a user inserting the sensor'splug end14 into the socket cavity of a conventional meter (not shown). Moreover, the wedgedportion20 of the sensor serves as a stop, and frictionally holds thesensor10 within the socket cavity of the meter.
• The fluidsample receiving end16 of thesensor10 includes anelectrochemical reaction zone24 adjacent theterminal end16 of the body. Thisreaction zone24 is a channel formed in the thirdtop surface15c and about/adjacent theelectrodes30,31,32 in thebody12 for reacting with the fluid drawn into thebody12. While the reaction zone may be formed above or below the electrodes, the preference has been to construct it above the electrodes. Anend cap27 is welded [by ultrasonics or adhesive] over thereaction zone24 and onto the thirdtop surface15c.The top of theend cap27 aligns with the top15,15bof thebody12. Theend cap27 is preferably made of the same material as the moldedbody12 and attached thereto by ultrasonic welding or gluing.
• While thecap27 is shown as a separate piece, it can also be constructed as part of thebody12 and hingably connected to the body such that it can be pivoted onto the thirdtop surface15c and attached [e.g., see The Second Embodiment]. In this manner, the entire sensor can be made at one time and as one molded, unitary piece.
• Acapillary opening28 is formed in theterminal end16 of thesensor10 when thecap27 is welded (or folded) to thebody12. This capillary opening leads to thereaction zone24. Preferably, thesensor10 is a capillary fill device, that is, thereaction zone24 is small enough to draw a fluid sample into the zone when the capillary opening orinlet28 is placed in contact with the fluid being tested, such as a drop of blood. Accordingly, if one wants to test his/her blood, s/he touches theterminal end26 to the blood and the blood is drawn into thesensor10 andreaction zone24 through thecapillary opening28. This is much easier than placing the sample (such as blood) on the sensor and on a target zone as in the prior art. To effectuate the capillary effect with thecapillary opening28 to thereaction zone24, avent29 is constructed into thecap27. This vent is in communication with thereaction zone24. Thisvent29 releases air pressure as thereaction zone24 draws and fills with fluid. For additional discussion regarding capillary filling, see U.S. Pat. Nos. 4,254,083; 4,413,407; 4,473,457; 5,798,031; 5,120,420; and 5,575,895, the disclosures of which are hereby incorporated by reference.
• Mostly encased within the injection moldedbody12 are a plurality of electrically conductive leads orelectrodes30,31,32. Preferably, thebody12 is molded about theseleads30,31,32. As noted, these leads are spaced from one another. They30,31,32 are primarily encased in thebody12 and run from theplug end14 to thereaction zone24, just before theterminal end16. The leads'30,31,32 ends26 are positioned just before theterminal end16 of the sensor.
• The conductive leads30,31,32 consist of an electrically conductive material like metal or metal alloy such as platinum, palladium, gold, silver, nickel, nickel-chrome, stainless steel, copper or the like. Moreover, each lead preferably consists of a single wire, or in an alternative preferred embodiment (See The Second Embodiment), a stamped metal member plated with gold or the like. In the first embodiment, the outer leads30 and32 are equally spaced from theinner lead31 with the spacing of the leads at the fluidsample receiving end16 of thebody12 being closer together than at themeter attachment end14.
• Segments33 of theleads30,31,32 are exposed about theplug end14 of thebody12 to providecontact surface areas34,35,36 respectively with the meter (not shown). Preferably, the exposedcontact surface areas34,35,36 extend from the taperedtop portion20 of thebody12 to theplug end14 of thebody12 on or partially embedded into the firsttop surface15a.Specifically, thebody12 may be molded such that thesegments33 of theleads31,31,32 are embedded (partially molded into the firsttop surface15a) and held by thebody12 opposite thecontact surface areas34,35,36. In this manner, the leads are exposed for contact with the meter and maintained in a position without the use of adhesives or welding.
• The portion of theleads30,31,32 between thesensor plug end14 and the fluidsample receiving end16 are embedded within the plastic injection moldedbody12. Accordingly, thebody12 is constructed of an electrically insulating injection moldable plastic.
• Certain structural support components are molded within thebody12 of thesensor10 to hold and maintain theleads30,31,32 within the body, in spaced relationship to one another, during and after the molding process. Specifically, guide blocks42 and alignment pins44 are molded within thebody12 for proper mounting of theleads30,31,32. Apertures are also formed in thetop surface15 andbottom surface13 of thebody12 for permitting the ingress and egress of fingers into the mold during the molding process (to be discussed below). In particular, afirst aperture46 is molded into the secondtop surface15band asecond aperture48 andthird aperture50 are formed into thebottom surface13 of thebody12. Once the molding is completed, each of theseapertures46,48,50 can be covered up with plastic (e.g., the same plastic used in the molding process) or left open. Their46,48,50 sizes are relatively small; leaving them open should not cause any safety issues or affect the sensor's ability. Fingers cannot fit into the apertures and debris from the outside will likely be unable to enter the apertures and contact theleads30,31,32.
• Within thereaction zone24, onelead30 serves as a primary workingelectrode52, asecond lead31 acts as a reference orcounter electrode53, and thethird lead32 serves as an auxiliary, secondary or second workingelectrode54. Desirably, the conductive leads30,31,32 (orelectrodes52,53,54) are the only leads (electrodes) coming into contact with the test sample of fluid entering thesensor10. Theelectrodes52,53,54 are electrically insulated from the rest of thesensor10 by molded plastic to ensure a signal carried by the leads arises only from that portion exposed to the test sample in theelectrochemical reaction zone24.
• In the embodiment, anenzyme56 is applied to the outer surface of the loprimary working electrode52 and, if desired, an electron transfer mediator. The enzyme can consist of, for instance, flavo-proteins, pqq-enzymes, haem-containing enzymes, oxidoreductase, or the like. For additional discussion regarding mediators, see U.S. Pat. Nos. 4,545,382 and 4,224,125, the disclosures of which are hereby incorporated by reference. In an alternative embodiment, anantibody57 can be applied to the outer surface of the secondary workingelectrode54. As such, thereaction zone24 can contain antibodies, enzyme-antibody conjugates, enzyme-analyte conjugates, and the like. It should be noted that anenzyme56 can also be applied to the second workingelectrode54 and an antibody can be applied to the outer surface of the primary workingelectrode52.
• As will be appreciated by those having skill in the art, theenzyme56 is specific for the test to be performed by thesensor10. For instance, the workingelectrode52, or secondary workingelectrode54, or both, can be coated with anenzyme56 such as glucose oxidase or glucose dehydrogenase formulated to react at different levels or intensities for the measurement of glucose in a human blood sample. Thus, as an individual's body glucose concentration increases, theenzyme56 will make more products. The glucose sensor is used with a meter to measure the electrochemical signal, such as electrical current, arising from oxidation or reduction of the enzymatic turnover product(s). The magnitude of the signal is directly proportional to the glucose concentration or any other compound for which a specific enzyme has been coated on the electrodes.
• In an embodiment, theenzyme56 can be applied to the entire exposed surface area of the primary electrode52 (or secondary electrode54). Alternatively, the entire exposed area of the electrode may not need to be covered with the enzyme as long as a well defined area of the electrode is covered with the enzyme.
• In a further embodiment and as shown in the prior art, anenzyme57 can be applied to all theelectrodes52,53,54 in thereaction zone24 and measures can be taken by a meter.
• In the preferred embodiment, one of the working electrodes (52 or54) is selectively coated with theenzyme57 carrying a reagent with the enzyme and the other working electrode (54 or52) is coated with a reagent lacking the respective enzyme. As such, with a meter, one can simultaneously acquire an electrochemical signal from each working electrode and correct for any “background noise” arising from a sample matrix. Thus, the potential or current between the reference and the electrode without the enzyme can be compared with the potential or current between the reference and the electrode with the enzyme. The measuring and comparing of the potential and current differences are well known to those skilled in the art.
• As indicated above, thesensor10 is used in conjunction with a meter capable of measuring an electrical property of the fluid sample after the addition of the fluid sample into thereaction zone24. The electrical property being measured may be, for example, electrical current, electrical potential, electrical charge, or impedance. An example of measuring changes in electrical potential to perform an analytical test is illustrated by U.S. Pat. No. 5,413,690, the disclosure of which is hereby incorporated by reference.
• An example of measuring electrical current to perform an analytical test is illustrated by U.S. Pat. Nos. 5,288,636 and 5,508,171, the disclosures of which are hereby incorporated by reference.
• Theplug end14 of thesensor10 can be inserted and connected to a meter, which includes a power source (a battery). Improvements in such meters and a sensor system are found in U.S. Pat. Nos. 4,999,632; 5,243,516; 5,366,609; 5,352,351; 5,405,511; and 5,438,271, the disclosures of which are hereby incorporated by reference.
• Many analyte-containing fluids can be analyzed by the electrochemical sensor of the present invention. For example, analytes in human and animal body fluids, such as whole blood, blood serum and plasma, urine and cerebrospinal fluid may all be measured. Also, analytes found in fermentation products, food and agricultural products, and in environmental substances, which potentially contain environmental contaminants, may be measured.
• The Molding Process
• In the past, while recognized for its strength and durability, plastic injection molding of sensors has been difficult and thus avoided. One reason is the reluctance to mold around the conductive wires or plates. The industry choice has been to make such sensors like sandwiches, having a top and bottom piece with the insides (conductive elements) being formed on one of the pieces or placed between the pieces. The sandwich-like sensor is then assembled together and sealed closed, such as with an adhesive.
• The present invention molds the sensors with the conductive elements inside the mold during the molding process. The advantages are many. In addition to making a stronger more durable sensor, such a process reduces labor involvement and steps and produces a more consistent product.
• Whilemultiple sensors10 can be produced with one mold, the making of a single sensor will be discussed. The mold has the shape of thebody12. Theconductive wires30,31,32 for the electrodes are first molded into the product. Specifically, the wire leads are fed into the mold and placed on or between figures [not shown] projecting into the mold through the openings in the mold (corresponding to theapertures46,48,50) to hold the wires in place and level during the set-up and molding process. In particular, the bottom apertures permit the fingers projecting into the mold to support the wires and the top apertures permit the fingers projecting into the mold to hold the wires. The liquid plastic is injected into the mold where it fills the mold. The plastic is then cooled.
• Once the plastic has formed and hardened, the fingers are pulled from and exit the mold through the openings (apertures46,48,50). The moldedsensor12 is next ejected from the mold.
• The reagents are next applied to the electrodes after the molding process is finished. First, after molding is finished, the cap is treated with a surfactant that facilitates pulling or drawing the fluid (e.g., test blood) into the capillary gap at the end of the sensor. Then, the reagents (including the enzyme) are applied to the electrodes.
• Theend cap27 is thereafter connected to themain body12 and any undesirable openings in the sensor can be sealed closed by the same plastic used for the mold. In the alternative, the chemicals can be applied to the wires after the end cap is married to the body. Any extraneous wire(s) projecting from the sensor can be cut and removed. Then, any desired writings on the sensor (e.g., manufacturing codes, product name, etc.) can then be applied to the sensor by conventional means.
The Second Embodiment
• Referring toFIGS. 7-12, an electrochemical sensor in accordance with the present invention, second embodiment, is depicted. In these figures, components similar to those in the first embodiment (10) will be identified with the same reference numbers, but in the100 series. Specifically,FIG. 7 shows thesensor110 as though it were made out of clear plastic, permitting one to look inside it. As noted previously, the internal components and hidden external components would not normally be visible looking down on thesensor110. The sensor of thesecond embodiment110 includes a moldedplastic body112 having a meter attachment end or plugend114 and a fluidsample receiving end116. The body has abottom surface113 and atop surface115. Anend cap127 is integral to thebody112 and molded with the body. Ahinge227 permits the pivoting of the end cap onto the main body as will be explained. Specifically, thetop surface115 of thesensor110 has threetop surfaces115a,115b,115c.The firsttop surface115aruns most of the length of the body and terminates at aledge215; the secondtop surface115bis positioned below or is lower than the first115a;and, the thirdtop surface115cis separated from the other twotop surfaces115a,115bby thehinge227. During construction of thesensor110, theend cap127 is rotated about the hinge such that the thirdtop surface115cabuts the secondtop surface115b,face-to-face, and rests adjacent theledge215 of thetop surface115a.Thebottom surface13aof thecap127 thus becomes the top surface adjacent the firsttop surface115a.SeeFIG. 8. A pair of taperedprotuberances125 formed in theend cap127 and a pair of taperedtroughs122 formed in themain body112 align and mate when the cap is folded into place. This facilitates and ensures correct alignment of the hinged parts.
• Thebody112 contains three spaced apartelectrodes130,131,132. Theplug end114 of thebody112 includes a pair of tapered side edges118,119 to facilitate a user inserting the sensor'splug end114 into the socket cavity of a conventional meter (not shown).
• The fluidsample receiving end116 of thesensor110 includes anelectrochemical reaction zone124 adjacent theterminal end116 of the body. Thisreaction zone124 is a channel formed in the secondtop surface115band about/adjacent theelectrodes130,131,132 in thebody112 for reacting with the fluid drawn into thebody112. While this reaction zone may be formed above or below the electrodes, the preference has been to construct it above the electrodes. Aridge327 is formed on the top surface (thirdtop surface115c) of the end cap. This ridge prevents any fluid from leaving thereaction zone124 or debris from entering the reaction zone once theend cap127 is welded [by ultrasonics or adhesive] onto the secondtop surface115b.When the end cap is folded, it is welded into position along the side surfaces of thepiece110. Thus, the ridge can be collapsed during welding and not affect the performance of the sensor. Anoptional channel327amay be constructed in the thirdtop surface115cto increase the height of thereaction zone124.
• Acapillary opening128 is formed in theterminal end116 of thesensor110 when thecap127 is folded and welded into place. This capillary opening leads to thereaction zone124. The width of theopening128 is approximately the same as the length of thesensing electrodes130,131,132 exposed to the test fluid in thereaction zone124. Thesensor110 of the second embodiment is also a capillary fill device, that is, thereaction zone124 is small enough to draw a fluid sample into the zone when thecapillary opening128 is placed in contact with the fluid being tested. Avent129 provided in thecap127 is in communication with thereaction zone124 to release pressure as thereaction zone124 draws and fills with fluid. Preferably, the bottom or base of the capillary inlet is flush with the top surface ofelectrodes130,131,132.
• Mostly encased within the injection moldedbody112 is an electrically conductive plate (stamped or cast) having leads orelectrodes130,131,132. Thebody112 is molded around the plate and theseleads130,131,32. The conductive plate is a single piece of material; it includes theleads130,131,132 and connectingsegments230 and231. When the sensor is made, the segments are connecting the leads. After molding, thesegments230,231 are cut and/or removed so that the leads are distinct and separated from one another. If they were connected, the system would short circuit.
• Theelectrodes130,131,132 are primarily encased in thebody112 and run from theplug end114 into thereaction zone124, just before theterminal end116. The leads130,131,132 may be widened if desired in the reaction zone to expose more surface area to the fluid and chemicals contacting one another in the zone. The leads130,131,132 can be as wide as the sensing parts. These leads130,131,132 are an electrically conductive material like metal or metal alloy such as platinum, palladium, gold, silver, nickel, nickel-chrome, stainless steel, copper or the like. To enhance their performance and sensitivity, they may also be coated, e.g., made of copper and coated with gold. In the second embodiment, theleads130,131,132 are spaced from and parallel to one another.
• Segments133 of theleads130,131,132 extend outwardly from thebody112 from theplug end114 of thesensor110 and are exposed to providecontact surface areas134,135,136 respectively with the meter (not shown). These leads can also be embedded in the molded plastic such that their upper surfaces are exposed in portions.
• As before, the portion of theleads130,131,132 between thesensor plug end114 and the fluidsample receiving end116 are embedded, or encased, within the plastic injection moldedbody112; thebody112 is constructed of an electrically insulating injection moldable plastic.
• Apertures are formed in thetop surface115 andbottom surface113 of thebody112 for permitting the ingress and egress of fingers into the mold during the molding process. In particular, a set (3) offirst apertures146 and a set (3) ofsecond apertures147 are molded into thetop surface15a;athird aperture148 andfourth aperture150 and a set (3) offifth apertures160,161,162 are formed into thebottom surface113 of thebody112. Once the molding is completed, each of theseapertures146,147,148,150 can be covered up with plastic (e.g., the same plastic used in the molding process) or left open.
• Within thereaction zone124, oneouter lead130 serves as aprimary working electrode152, thecenter lead131 acts as a reference orcounter electrode153, and the otherouter lead132 serves as an auxiliary or secondary or second workingelectrode154. These conductive leads130,131,132 (orelectrodes152,153,154) are the only leads (electrodes) coming into contact with the test sample of fluid entering thesensor110. Theelectrodes152,153,154 are electrically insulated from the rest of thesensor110 by molded plastic to ensure a signal carried by the leads arises only from that portion exposed to the test sample in theelectrochemical reaction zone124.
• As with the first embodiment, anenzyme156 is applied to the outer surface of theprimary working electrode152 and, if desired, an electron transfer mediator. Anantibody157 may also be applied to the outer surface of the secondary workingelectrode154. Anenzyme156 can also be applied the second workingelectrode154 and an antibody to the outer surface of the primary workingelectrode52.
• Theenzyme156 can be applied to the entire exposed surface area of the primary electrode152 (or secondary electrode154). Alternatively, the entire exposed area of the electrode may not need to be covered with the enzyme as long as a well defined area of the electrode is covered with the enzyme. Or, an enzyme can be applied to all theelectrodes152,153,154 in thereaction zone124 and measurements can be taken by a meter. Preferably, one of the working electrodes (152 or154) is selectively coated with the enzyme carrying a reagent with the enzyme and the other working electrode (154 or152) is coated with a reagent lacking the respective enzyme.
• Thesensor110 is used in conjunction with a meter capable of measuring an electrical property of the fluid sample after the addition of the fluid sample into thereaction zone124. Theplug end114 of thesensor110 is inserted and connected to a meter, as before with the first embodiment.
• The Molding Process
• The mold has the shape of thebody112. The conductive130,131,132 leads/electrodes (in the form of a plate with the joiningextensions230,231 for the electrodes) are first treated with any coatings (metal). The chemicals/reagents (with and without enzymes) may also be applied before molding; or, they can be applied after the molding. The plate is fed into the mold and placed on or between fingers (not shown) projecting into the mold through the openings in the mold (corresponding to theapertures146,147,148,150) to hold the plate in place and level during the set-up and molding process. Knives or punches (not shown) are also inserted through the top surface of the mold (outline of opening formed by the knives/punches170). These knives punch and sever thejointing extensions230,231 and hold the bent portions in place during molding (seeFIG. 11). As before, the bottom apertures permit the fingers projecting into the mold to support the plate with leads and the top apertures permit the fingers projecting into the mold to hold the plate and leads. The liquid plastic is injected into the mold where it fills the mold. The plastic is then cooled.
• Once the plastic has formed and hardened, the fingers are drawn from the mold through the openings (apertures146,147,148,150,160,161,162). The knives/punches are drawn through theupper surface openings170. Once the knives/punches are removed, the cut or skivedextensions230,231 disposed between theleads130,131 and131,132 ensures the leads are kept separate. The moldedsensor112 is then ejected from the mold and any undesirable openings in the sensor can be sealed closed by the same plastic used for the mold. In the preferred alternative, the critical reagents are applied to the sensors in thereaction zone124 above the leads. A surfactant can be used to treat the capillary inlet to facilitate the capillary function. Any extraneous metal projecting from the sensor can be cut and removed. Then, any desired writings on the sensor (e.g., manufacturing codes, product name, etc.) can then be applied to the sensors by conventional means.
• While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying Claims. For instance, in another embodiment of the present invention, a sensor is designed for use with a light reflectance measuring meter for photometric detection of a die contained within a fluid sample receiving well.

Claims (39)

1. An electrochemical device for cooperating with an electronic meter capable of measuring electrical properties between at least two electrically conductive electrodes, comprising:

at least two spaced apart electrically conductive electrodes;

a body of molded insulative material housing the electrodes and partially embedding at least a portion of each of the electrodes;

means for connecting the meter to the body;

means for receiving a fluid sample; and,

one or more substances on at least one of the electrodes to change the electrical properties between the electrodes upon reacting with the fluid sample.

2. The electrochemical device ofclaim 1 wherein the electrodes are substantially molded into the insulative material.

3. The electrochemical device ofclaim 1 wherein the means for receiving the fluid sample is a capillary inlet adapted to draw the fluid sample into the body upon contact with the fluid sample.

4. The electrochemical device ofclaim 3 wherein the capillary inlet is molded into an end of the body and is in communication with a reaction zone.

5. The electrochemical device ofclaim 4 wherein the reaction zone is a channel formed in the body and is adapted for permitting the reaction of the fluid drawn into the body by the capillary force.

6. The electrochemical device ofclaim 3 wherein the capillary inlet has a vent in communication therewith for relieving pressure.

7. The electrochemical device ofclaim 3 wherein the capillary inlet is molded into the body and is in communication with a reaction zone, the reaction zone being a chamber formed in the body, adapted for permitting the reaction of the fluid drawn into the body by the capillary force, and in communication with a vent for relieving pressure.

8. The electrochemical device ofclaim 1 wherein the electrodes are one of either conductive wires or formed from a conductive plate.

9. The electrochemical device ofclaim 1 wherein at least one electrode is coated with a conductive material different than the composition of the electrode.

10. The electrochemical device ofclaim 1 wherein an enzyme is on at least one of the electrodes and at least an antibody is on another of the electrodes.

11. The electrochemical device ofclaim 10 wherein an electron mediator is on one or more of the electrodes.

12. The electrochemical device ofclaim 1 wherein a coating is on at least one electrode with a reagent and an enzyme.

13. The electrochemical device ofclaim 1 wherein the means for connecting the meter to the body is a plug formed at one end of the body exposing the electrodes outside the body for connecting the meter to the body.

14. An electrochemical device for cooperating with an electronic meter capable of measuring electrical properties between at least two electrically conductive electrodes, comprising:

at least two spaced apart electrically conductive electrodes;

a body of molded insulative material housing the electrodes, partially embedding at least a portion of each of the electrodes, the body composed of at least two pieces, a body and an end cap, attached to one another;

means for connecting the meter to the body;

means for receiving a fluid sample; and,

one or more substances on at least one of the electrodes to change the electrical properties between the electrodes upon reacting with the fluid sample.

15. The electrochemical device ofclaim 14 wherein the electrodes are substantially molded into the insulative material.

16. The electrochemical device ofclaim 14 wherein the means for receiving the fluid sample is a capillary inlet adapted to draw the fluid sample into the body upon contact with the fluid sample.

17. The electrochemical device ofclaim 16 wherein the capillary inlet is molded into an end of the body and is in communication with a reaction zone.

18. The electrochemical device ofclaim 17 wherein the reaction zone is a channel formed in the body and is adapted for permitting the reaction of the fluid drawn into the body by the capillary force.

19. The electrochemical device ofclaim 16 wherein the capillary inlet has a vent in communication therewith for relieving pressure.

20. The electrochemical device ofclaim 16 wherein the capillary inlet is molded into the body and is in communication with a reaction zone, the reaction zone being a chamber formed in the body, adapted for permitting the reaction of the fluid drawn into the body by the capillary force, and in communication with a vent for relieving pressure.

21. The electrochemical device ofclaim 14 wherein the electrodes are one of either conductive wires or formed from a conductive plate.

22. The electrochemical device ofclaim 14 wherein at least one electrode is coated with a conductive material different than the composition of the electrode.

23. The electrochemical device ofclaim 14 wherein an enzyme is on at least one of the electrodes and at least an antibody is on another of the electrodes.

24. The electrochemical device ofclaim 23 wherein an electron mediator is on one or more of the electrodes.

25. The electrochemical device ofclaim 14 wherein a coating is on at least one electrode with a reagent and an enzyme.

26. The electrochemical device ofclaim 14 wherein the means for connecting the meter to the body is a plug formed at one end of the body exposing the electrodes outside the body for connecting the meter to the body.

27. An electrochemical device for cooperating with an electronic meter capable of measuring electrical properties between at least two electrically conductive electrodes, comprising:

at least two spaced apart electrically conductive electrodes;

a body of molded insulative material housing the electrodes, partially embedding at least a portion of each of the electrodes, the body having a hinge constructed therein for permitting the pivoting and connecting of a portion of the body onto itself;

means for connecting the meter to the body;

means for receiving a fluid sample; and,

one or more substances on at least one of the electrodes to change the electrical properties between the electrodes upon reacting with the fluid sample.

28. The electrochemical device ofclaim 27 wherein the electrodes are substantially molded into the insulative material.

29. The electrochemical device ofclaim 27 wherein the means for receiving the fluid sample is a capillary inlet adapted to draw the fluid sample into the body upon contact with the fluid sample.

30. The electrochemical device ofclaim 29 wherein the capillary inlet is molded into an end of the body and is in communication with a reaction zone.

31. The electrochemical device ofclaim 30 wherein the reaction zone is a channel formed in the body and is adapted for permitting the reaction of the fluid drawn into the body by the capillary force.

32. The electrochemical device ofclaim 29 wherein the capillary inlet has a vent in communication therewith for relieving pressure.

33. The electrochemical device ofclaim 29 wherein the capillary inlet is molded into the body and is in communication with a reaction zone, the reaction zone being a chamber formed in the body, adapted for permitting the reaction of the fluid drawn into the body by the capillary force, and in communication with a vent for relieving pressure.

34. The electrochemical device ofclaim 27 wherein the electrodes are one of either conductive wires or formed from a conductive plate.

35. The electrochemical device ofclaim 27 wherein at least one electrode is coated with a conductive material different than the composition of the electrode.

36. The electrochemical device ofclaim 27 wherein an enzyme is on at least one of the electrodes and at least an antibody is on another of the electrodes.

37. The electrochemical device ofclaim 36 wherein an electron mediator is on one or more of the electrodes.

38. The electrochemical device ofclaim 27 wherein a coating is on at least one electrode with a reagent and an enzyme.

39. The electrochemical device ofclaim 27 wherein the means for connecting the meter to the body is a plug formed at one end of the body exposing the electrodes outside the body for connecting the meter to the body.

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