Abstract:
A urine sugar detecting device including (a) a urine sugar sensor including a contact electrode and a cover film covering the contact electrode therewith, (b) a cartridge encasing the urine sugar sensor in fluid tight except the contact electrode, and (c) at least one contact pin having a straightly extending proximal portion and an obliquely, downwardly inclining distal portion, the contact pin being kept deformed in the cartridge so as to have a force with which the contact pin pierces the cover film to thereby have electrical connection with the contact electrode.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a urine sugar detecting device, and a method of fabricating the same. 
     2. Description of the Related Art 
     Many urine sugar detecting devices have been suggested so far. For instance, Japanese Unexamined Patent Publication No. 8-193969 has suggested a device for electrically, chemically detecting glucose, and Japanese Patent Publication No. 8-23545 has suggested an enzyme electrode to be used for a glucose sensor. 
     For another instance, Japanese Unexamined Patent Publication 5-72172 has suggested an enzyme electrode to be used for a urine sugar detecting sensor. FIG. 1 illustrates the enzyme electrode suggested in the Publication. The illustrated enzyme electrode is fabricated as follows. 
     First, a platinum layer is formed on an insulating substrate  1  by sputtering. Then, the platinum layer is patterned by photolithography and etching steps to thereby form operation electrodes and reference electrodes. Each of the operation and reference electrodes is comprised of a sensitive portion  2   a , a lead portion (not illustrated), and a connection portion  2   b.    
     Then, dip coating is applied to the insulating substrate  1  to thereby form an enzyme film  3  over the insulating substrate  1  except the connection portions  2   b . Thereafter, the insulating substrate  1  is divided into enzyme electrodes. 
     In the enzyme electrode illustrated in FIG. 1, dip coating is applied to the insulating substrate  1  in order to form the enzyme film  3 . However, the dip coating is accompanied with problems that the dip coating cannot be applied to a plurality of substrates at a time, and hence, is not suitable for mass-production of enzyme electrodes, and that it is quite difficult for the dip coating to uniformize film quality and film thickness. 
     To solve these problems, Japanese Patent Publication No. 8-16669 has suggested a method of patterning an enzyme film in a region other than contact electrodes by photolithography. In this method, lift-off is carried out using a photoresist film. This method is carried out as follows. 
     First, contact electrodes are formed on a substrate. Then, a photoresist film is formed over the substrate by spin coating. Then, the photoresist film is removed in a region other than contact electrodes by photolithography. 
     Then, an enzyme film is formed over the substrate by spin coating. Then, the residual photoresist film is dissolved by organic solvent to thereby remove the enzyme film on the contact electrodes. 
     According to the method suggested in Japanese Patent Publication No. 8-16669, a plurality of substrates can be treated at a time, because a photoresist film can be applied to those substrates at a time by spin coating. Hence, the suggested method is suitable for mass-production of enzyme electrodes, and, in addition, has an advantage that film quality and film thickness can be readily uniformized. 
     However, the method suggested in Japanese Patent Publication No. 8-16669 needs to carry out a photolithography step. In other words, the method needs a particular apparatus for carrying out photolithography, and hence, is accompanied with a problem that it is not possible to shorten a time for fabricating an enzyme electrode. 
     In addition, the necessity of preparing a photolithography apparatus increases fabrication costs. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems, it is an object of the present invention to provide a urine sugar detecting device which can be fabricated in simpler fabrication steps, specifically, without carrying out a photolithography step. It is also an object of the present invention to provide a method of fabricating such a urine sugar detecting device. 
     In one aspect of the present invention, there is provided a urine sugar detecting device including (a) a urine sugar sensor including at least one contact electrode and a cover film covering the contact electrode therewith, (b) a cartridge encasing the urine sugar sensor in fluid tight except the contact electrode, and (c) at least one contact pin encased in the cartridge and electrically connecting the contact electrode through the cover film. 
     It is preferable that the contact pin pierces the cover film to thereby have electrical connection with the contact electrode. For instance, the contact pin is kept deformed in the cartridge so as to have a force with which the contact pin pierces the cover film. 
     For instance, the contact pin is comprised of a straightly extending proximal portion and an obliquely, downwardly inclining distal portion, in which case, it is preferable that the distal portion obliquely, downwardly inclines by about 45 degrees. 
     In another aspect of the present invention, there is provided a method of fabricating a urine sugar detecting device, including the steps of (a) fixing a urine sugar sensor in a lower half of a cartridge, the sensor including a contact electrode and a cover film covering the contact electrode therewith, (b) fixing a contact pin in an upper half of a cartridge, the contact pin having a free distal end, and (c) coupling the lower and upper halves of a cartridge in fluid tight so that the distal end of the contact pin pierces the cover film, and makes electrical contact with the contact electrode. 
     There is further provided a method of fabricating a urine sugar detecting device, including the steps of (a) fixing a urine sugar sensor in a lower half of a cartridge, the urine sugar sensor including a contact electrode and a cover film covering the contact electrode therewith, (b) fixing a contact pin in an upper half of a cartridge so that a straightly extending proximal portion of the contact pin is fixed and an obliquely, downwardly inclining distal portion of the contact pin is free, and (c) coupling the lower and upper halves of a cartridge in fluid tight so that the distal portion of the contact pin is deformed to thereby pierce the cover film, and makes electrical contact with the contact electrode. 
     A urine sugar detecting device is generally fabricated as follows. First, contact electrodes composed of platinum and silver are formed on an insulating substrate. Then, an organic, insulating thin film for detecting glucose is formed over the insulating substrate. According to this method, it is impossible to externally establish electrical connection, because the insulating thin film entirely covers the contact electrodes therewith. 
     Hence, in the present invention, a contact pin is pressurized to thereby pierce the insulating thin film at a distal end thereof. As a result, the contact pin makes electrical connection with the contact electrodes to thereby establish electrical connection. 
     In accordance with the present invention, it no longer necessary to carry out a step of removing the insulating thin film formed on the contact electrodes, and a step of forming the insulating thin film on the substrate in an area other than terminals. Hence, the urine sugar detecting device can be fabricated in simplified process relative to a conventional process. 
     The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an enzyme electrode to be used in a conventional urine sugar detecting device. 
     FIG. 2 is a plan view illustrating a urine sugar detecting sensor in a urine sugar detecting device in accordance with an embodiment of the present invention. 
     FIG. 3 is a cross-sectional view taken along the line III—III in FIG.  2 . 
     FIG. 4A is a plan view of a urine sugar detecting sensor in accordance with an embodiment of the present invention.  10 FIG. 4B is a side view of the urine sugar detecting sensor illustrated in FIG.  4 A. 
     FIG. 5A is a plan view of a lower half of a cartridge constituting a urine sugar detecting sensor in accordance with the embodiment. 
     FIG. 5B is a cross-sectional view taken along the line VB—VB in FIG.  5 A. 
     FIG. 6A is a longitudinal cross-sectional view illustrating an inside of a detecting sensor in accordance with the embodiment. 
     FIG. 6B is a cross-sectional view taken along the line VIB—VIB in FIG.  6 A. 
     FIG. 7A is a plan view of an upper half of a cartridge constituting a urine sugar detecting sensor in accordance with the embodiment. 
     FIG. 7B is a cross-sectional view taken along the line VIIB—VIIB in FIG.  7 A. 
     FIG. 8 is an enlarged view illustrating a contact pin and contact electrodes in a urine sugar detecting device in accordance with the embodiment. 
     FIG. 9 is a perspective view illustrating a urine sugar detecting device in accordance with the embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A urine sugar detecting device in accordance with a preferred embodiment of the invention is used for measuring a concentration of glucose contained in urine, and basically includes a urine sugar detecting sensor  1  and a cartridge  10  encasing the urine sugar sensor therein. In the cartridge  10 , the urine sugar detecting sensor  1  is electrically connected to a circuit for detecting a glucose concentration. The cartridge  10  is formed fluid tight, because the urine sugar detecting device is dipped into urine when a glucose concentration is to be detected. 
     As illustrated in FIGS. 2 and 3, the urine sugar detecting sensor  1  is comprised of an insulating substrate  8 , an operation electrode  4 , an opposing electrode  5 , a reference electrode  6 , contact electrodes  4   a ,  5   a  and  6   a , leads  4   b ,  5   b  and  6   b , and a film  7  for detecting glucose. 
     The insulating substrate  8  is a silicon substrate on which a silicon dioxide film is formed. As an alternative, the insulating substrate  8  may be composed of glass, quartz, polyimide, polycarbonate, or glass epoxy. 
     The electrodes  4 ,  5 , and  6 , the contact electrodes  4   a ,  5   a  and  6   a , and the leads  4   b ,  5   b  and  6   b  are all formed on the insulating substrate  8 . The leads  4   b ,  5   b  and  6   b  electrically connect the operation electrode  4 , the opposing electrode  5 , and the reference electrode  6  to the contact electrodes  4   a ,  5   a  and  6   a , respectively. The operation electrode  4 , the opposing electrode  5 , and the reference electrode  6  cooperate with one another to thereby measure a concentration of hydrogen peroxide contained in urine. 
     The operation electrode  4  and the opposing electrode  5  are comprised of a titanium layer and a platinum layer deposited on the titanium layer. As an alternative, the operation electrode  4  and the opposing electrode  5  may be composed of platinum and any one of carbon, gold, and iridium. The operation electrode  4  and the opposing electrode  5  may be formed by evaporation, sputtering, screen printing, or plating. When the operation electrode  4  and the opposing electrode  5  are formed by sputtering, it is preferable that the titanium layer has a thickness in the range of 0.02 to 0.2 μm, and the platinum layer has a thickness in the range of 0.1 to 1.0 μm. 
     The reference electrode  6  is comprised of a silver layer formed on the insulating substrate  8 , and a silver chloride layer formed by chemically treating a surface of the silver layer. A titanium layer and a platinum layer may be formed under the silver layer in order to enhance adhesion. When the reference electrode  6  is formed by sputtering, it is preferable that the silver layer has a thickness in the range of 0.1 to 1.0 μm. The silver chloride layer may be formed by treating a surface of the silver layer with iron chloride (II) solution or chromium chloride (II) solution, or by electrolyzing the silver layer in chloride solution. 
     The operation electrode  4  has a size of 1.2 mm×2.0 mm, the opposing electrode  5  has a size of 0.4 mm×2.0 mm, and the reference electrode  6  has a size of 0.4 mm×2.0 mm. The leads  4   b ,  5   b  and  6   b  have the same size of 1.2 mm×2.8 mm. The contact electrodes  4   a ,  6   a  and  6   a  have the same size of 1.6 mm×0.8 mm. The urine sugar sensor  1  has a size of 6.0 mm×9.0 mm. 
     As illustrated in FIG. 3, the electrodes  4 ,  5 , and  6 , the contact electrodes  4   a ,  5   a  and  6   a , and the leads  4   b ,  5   b  and  6   b  are all covered with the glucose detecting film  7 . The glucose detecting film  7  contains glucose oxidase (GOD) therein. The glucose detecting film  7  has a multi-layered structure including a first film  7   a  formed on the insulating substrate  8 , a second film  7   b  formed on the first film  7   a , and a third film  7   c  formed on the second film  7   b.    
     The first film  7   a  allows only hydrogen peroxide to pass therethrough, and disallows interfering substance to pass therethrough. As a result, the first film  7   a  removes interfering substance. The first film  7   a  is composed of at least one of silane coupling agent, fluorine contained resin, and acetyl cellulose. The first film  7   a  is formed by spin coating. 
     The second film  7   b  fixes enzyme therein. The second film  7   b  is formed by spin-coating an aqueous solution containing glucose, albumin, and glutaric aldehyde. 
     The third film  7   c  restricts transmission of glucose therethrough to hereby broaden a range in which the urine sugar detecting device can detect glucose. The third film  7   c  is formed by spin-coating any one of silicone, carboxymethyl cellulose, polyurethane, perfluorocarbon. 
     A total thickness of the first to third films  7   a  to  7   c  is designed to be equal to or smaller than 1 μm. 
     Glucose oxidase oxidizes glucose to δ-D-gluconic lactone. With this oxidation, oxygen is reduced to hydrogen peroxide in accordance with the following reaction formula. 
     
       
         β-D-glucose + O 2 →δ-D-gluconic lactone+H 2 O 2   
       
     
     The thus generated hydrogen peroxide is oxidized on the electrodes  4 ,  5  and  6 , and an oxidation current is measured in the oxidation. Based on the thus measured oxidation current, a concentration of hydrogen peroxide can be detected in accordance with the following reaction formula. 
     
       
         H 2 O 2 →2H + +O 2 +2 e   −   
       
     
     Since a hydrogen peroxide concentration is in proportion to a glucose concentration, a glucose concentration can be calculated based on the hydrogen peroxide concentration. 
     With reference to FIG. 2, a constant voltage in the range of 0.4V to 0.7V is applied across the operation electrode  4  and the reference electrode  6  in the urine sugar sensor  1 . As a result, hydrogen peroxide is anodically oxidized on the operation electrode  4 , and an oxidation current runs between the operation electrode  4  and the opposing electrode  5 . The thus generated oxidation current is measured, and a hydrogen peroxide concentration is detected in the above-mentioned manner. 
     Hereinbelow is explained a method of fabricating the above-mentioned urine sugar sensor  1 . 
     First, a titanium layer and a platinum layer are formed on an insulating substrate  8  having a size of 60 mm×70 mm by sputtering. Further, a silver layer is formed over the platinum layer by sputtering. Then, the titanium, platinum and silver layers are patterned by photolithography into the operation electrode  4 , the opposing electrode  5 , the reference electrode  6 , the leads  4   b ,  5   b  and  6   b , and the contact electrodes  4   a ,  5   a  and  6   a.    
     Then, the resultant product is treated with iron chloride (III) solution to thereby form a silver chloride layer at a surface of the silver layer. 
     Then, the first, second and third films  7   a ,  7   b  and  7   c  are formed in this order on the insulating substrate  8  by spin-coating. 
     Then, the insulating substrate  8  is divided into separate urine sugar detecting sensors  1  each having a size of 6 mm×9 mm. Each of the urine sugar detecting sensors  1  is encased into the cartridge  10 . Thus, there is completed a urine sugar detecting device. 
     The cartridge  10  is comprised of an upper half  10   a  illustrated in FIGS. 4A,  4 B,  7 A and  7 B, and a lower half  10   b  illustrated in FIGS. 5A and 5B. 
     As illustrated in FIGS. 4A and 4B, the operation electrode  4 , the opposing electrode  5 , and the reference electrode  6  of the urine sugar detecting sensor  1  are encased into the cartridge  10  so that they make contact with an external solution through a window  13  formed with the upper half  10   a  and that the leads  4   b ,  5   b  and  6   b  and the contact electrodes  4   a ,  5   a  and  6   a  do not make contact with an external solution. As explained later in detail, the contact electrodes  4   a ,  5   a  and  6   a  are designed to make electrical contact with a detecting circuit (not illustrated) mounted in the cartridge  10 , through contact pins  9   a ,  9   b  and  9   c.    
     As illustrated in FIGS. 5A and 5B, the lower half  10   b  of the cartridge  10  is formed with a raised base portion  14  on which the urine sugar sensor  1  is to be fixedly mounted. The lower half  10   b  is further formed at a periphery thereof with a projection  15  having a rectangular cross-section. 
     As illustrated in FIGS. 4A,  4 B,  7 A and  7 B, the upper half  10   a  of the cartridge  10  is designed to be coupled to the lower half  10   b  to thereby form an enclosure. As best illustrated in FIG. 7B, the upper half  10   a  is formed at a peripheral lower surface thereof with a groove  16  having a rectangular crosssection, into which the projection  15  of the lower half  10   b  can be fit. The upper half  10   a  is formed with the window  13  above the raised base portion  14  of the lower half  10   b . A wall defining the window  13  is formed at a lower surface thereof with a sealing groove  18 . 
     As illustrated in FIG. 7A, the upper half  10   a  includes the contact pins  9   a ,  9   b  and  9   c . Each of the contact pins  9   a ,  9   b  and  9   c  is comprised of a straightly extending proximal portion  91 , and an obliquely, downwardly inclining distal portion  92 . The proximal portions  91  are fixed to the upper half  10   a , whereas the distal portions  92  are set free. 
     Each of the contact pins  9   a ,  9   b  and  9   c  are composed of phosphor bronze, and is plated with gold. Each of the contact pins  9   a ,  9   b  and  9   c  has a diameter of 0.45 mm and a length of 13 mm. The contact pins  9   a ,  9   b  and  9   c  are spaced away from one another in parallel by a distance of 1.27 mm, and the proximal portions  92  are integral with one another by resin. 
     The distal portion  92  of each of the contact pins  9   a ,  9   b  and  9   c  is 1 mm long, and inclines obliquely, downwardly by about 45 degrees. The distal portions  92  have a sharpened end having a point angle of 15 degrees. As illustrated in FIG. 8, the distal portions  92  pierce the glucose detecting film  7  to thereby make electrical contact with the contact electrodes  4   a ,  5   a  and  6   a.    
     The upper and lower halves  10   a  and  10   b  are composed of ABS resin, and are designed to have a length 25 mm, a width of 12 mm, and a thickness of 0.5 mm. The coupled upper and lower halves  10   a  and  10   b  have a height of 5 mm. 
     A seal  11  is fit into the sealing groove  18  of the upper half  10   a . The seal  11  is made from an acrylic adhesive sheet. The seal  11  is designed to have a size of 7 mm×7 mm and a thickness of 0.25 mm, and is formed centrally with an inner opening having a diameter of 4 mm. When the seal  11  is fit into the sealing groove  18 , the inner opening of the seal  11  is in alignment with the window  13  having an inner diameter of 4 mm. 
     The urine sugar detecting device in accordance with the embodiment is assembled as follows. 
     First, the urine sugar detecting sensor  1  is fixedly adhered onto the raised base portion  14  of the lower half  10   b.    
     Then, the contact pins  9   a ,  9   b  and  9   c  are mounted on the upper half  10   a  by inserting the contact pins  9   a ,  9   b  and  9   c  into positioning grooves (not illustrated). Then, silicone adhesive is applied to the groove  16  of the upper half  10   a  by means of a dispenser, and the seal  11  is fit into the sealing groove  18  of the upper half  10   a.    
     Then, the projection  15  of the lower half  10   b  is fit into the groove  16  of the upper half  10   a  to thereby position the upper and lower halves  10   a  and  10   b  relative to each other, and the upper and lower halves  10   a  and  10   b  are adhered to each other through adhesive in fluid tight. 
     Thus, only the operation electrode  4 , the opposing electrode  5 , and the reference electrode  6  of the urine sugar detecting sensor  1  can make contact with external solution through the window  13  formed with the cartridge  10 , and the leads  4   b ,  5   b  and  6   b  and the contact electrodes  4   a ,  5   a  and  6   a  are not allowed to make contact with external solution. 
     As illustrated in FIG. 8, when the upper and lower halves  10   a  and  10   b  are coupled to each other, since the contact pins  9   a ,  9   b  and  9   c  make contact with the urine sugar detecting sensor  1 , the contact pins  9   a ,  9   b  and  9   c  are forced to be deformed. As a result, the distal portions  92  of the contact pins  9   a ,  9   b  and  9   c  receive a force generated due to the deformation of the contact pins  9   a ,  9   b  and  9   c , and hence, pierce the glucose detecting film  7  formed on the contact electrodes  4   a ,  5   a  and  6   a . Thus, the contact pins  9   a ,  9   b  and  9   c  make contact with the contact electrodes  4   a ,  5   a  and  6   a , respectively, and thereby, make electrical contact with a detecting circuit (not illustrated) mounted in the cartridge  10 . 
     The distal portions  92  of the contact pins  9   a ,  9   b  and  9   c  are designed to deform by such a length that they can pierce the glucose detecting film  7  by virtue of a force generated due to the deformation of the contact pins  9   a ,  9   b  and  9   c . In this embodiment, the length is set about 2 mm. 
     FIG. 9 illustrates the urine sugar detecting device in accordance with the embodiment. Urine sugar is measured by dipping the urine sugar detecting device into urine. Enzymatic reaction occurs at a surface of the urine sugar detecting sensor  1  with the result of generation of hydrogen peroxide. The generation of hydrogen peroxide causes generation of an oxidation current, which is detected by the detecting circuit (not illustrated) mounted in the cartridge  10 . The detecting circuit calculates a concentration of glucose, based on the thus detected oxidation current, and displays the calculated concentration in a display section  12 . 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the subject matter encompassed by way of the present invention is not to be limited to those specific embodiments. On the contrary, it is intended for the subject matter of the invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims. 
     The entire disclosure of Japanese Patent Application No. 10-072077 filed on Mar. 20, 1998 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.