Abstract:
A tool for a sensor includes a first portion having an elongated channel that extends therealong for accommodating the sensor, and a second portion with an end slot that accommodates an end portion of the sensor, the sensor having one or more wire electrodes embedded between two substrates. One or both of the substrates has transaxial scoring for facilitating the snapping off of segments to expose a clean portions of the wire electrodes. One or both of the tool portions has a rounded end portion. The end slot of the second portion is dimensioned to correspond to an axial dimension of a segment that is to be snapped off from the sensor. The first tool portion has a shoulder and handle portions, the shoulder portion having a greater thickness than the handle portion, and the handle portion having a thickness that is less than the width of the sensor.

Description:
RELATIONSHIP TO OTHER APPLICATIONS 
     This application is a continuation, and claims the benefit of the filing date, of International Patent Application Ser. No. PCT/US2010/003145 filed on Dec. 10, 2010, which claims the benefit of the filing date of Provisional Patent Application Ser. No. 61/283,996 filed on Dec. 10, 2009, Conf. No. 6390 (Foreign Filing License Granted) in the names of the same inventor as herein. The disclosure in the identified PCT and United States Provisional Patent Applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to sensors, such as the type used to perform volammetric analysis, and more particularly, to a tool for use with a sensor arrangement having snap-off segments whereby one or more electrodes of the sensor are renewed. 
     2. Description of the Related Art 
     Electroanalytical methods are used in experimental analytical chemistry, and in multiple types of industrial processes. One such electroanalytical method is known as “voltammetry,” wherein the characteristics of an analyte are learned by measuring current as voltage is varied. Systems employed in voltammetric experimentation typically require at least two electrodes. On such electrode is termed the “working electrode,” which communicates with the analyte and applies the desired potential. The voltage is applied in accordance with a predetermined pattern wherein the transfer of electrons through the analyte is facilitated. Such voltage patterns include ramps (linear sweep), timed steps, square waves, and alternating sinusoidal and other cyclic voltage functions. 
     There is additionally provided in known electroanalytical systems a second electrode that functions as the other half of the cell. The second electrode is characterized with a known potential that is used to gauge the potential of the working electrode. In addition, the second electrode, in some systems, balances the electrons that have been added to, or removed from, the analyte by the working electrode. One significant issue with this known arrangement is that it is difficult to maintain a constant potential at the second electrode while passing current therethrough in an effort to counter the redox events taking place at the working electrode. 
     On known effort to overcome the forgoing difficulty involves the dividing of the functions of supplying electrons and of simultaneously providing a reference potential between two separate electrodes. In such an arrangement, the reference electrode constitutes a half cell having a known potential, and its role is limited to function as a reference in measuring and controlling the voltage of the working electrode. More specifically, it does not conduct any current. A separate auxiliary electrode passes all of the current that would be required to balance the current observed at the working electrode. In use, the auxiliary electrode (also known as a “counter electrode”) will experience extensive variations in it voltage, often to the extreme potentials associated with the analyte under consideration. At such extreme voltages, the analyte, which may be a solvent or and electrolyte, is oxidized, or “reduced.” 
     It is necessary that the working electrode have known dimensions and surface characteristics, and that it be cleaned and polished regularly. Such is not the case with the auxiliary electrode, which can be formed of a material that is conductive and that will not react with the analyte solution, or at least not the bulk analyte that has been added to reduce the overall resistance of the solution and thereby serves to improve accuracy. 
     As noted, there is a need to maintain the electrode clean. This creates a collateral need for a sensor arrangement that is inexpensive and does not need to be replaced simply because the electrode has become contaminated. 
     There is additionally a need in the art for a sensor system that facilitates renewal of the working electrode without requiring the entire sensor to be discarded. 
     It is, therefore, an object of this invention to provide a sensor arrangement that is inexpensive. 
     It is another object of this invention to provide an inexpensive sensor arrangement in which the working electrode can easily and inexpensively be renewed. 
     It is also an object of this invention to provide a simple sensor arrangement wherein the working electrode can easily be renewed without complex associated systems, as is the case, for example, in dropping mercury sensor systems. 
     SUMMARY OF THE INVENTION 
     The foregoing and other objects are achieved by this invention which provides a tool for a sensor arrangement. In accordance with the invention, the tool includes a first tool portion having an elongated channel extends that completely therealong for accommodating the sensor arrangement. A second tool portion has an end slot that accommodates therein an end portion of the sensor arrangement. In the practice of the invention, the sensor arrangement is provided with first and second substrates that are arranged in juxtaposed relation to each other, and a wire electrode embedded between the first and second substrates. At least one of the first and second substrates has transaxial scoring for facilitating the snapping off of segments of the first and second substrates to expose a clean portion of the wire electrode. 
     In one embodiment of the invention, a selectable one of said first and second tool portions is provided with a rounded end portion. In other embodiments, both of the first and second tool portions are provided with a rounded end portions. 
     In a further embodiment, the end slot of the second tool portion is dimensioned to correspond to an axial dimension of a segment that is to be snapped off from the sensor arrangement. 
     Preferably, the first tool portion has a shoulder portion and a handle portion. The shoulder portion has a greater thickness than the handle portion. In such an embodiment, the handle portion has a thickness that is less than a width dimension of the sensor arrangement. 
     In the practice of on embodiment the invention, the wire electrode is formed of gold. In other embodiments, there is provided a second electrode interposed between the first and second substrates of the sensor arrangement. 
     In accordance with a further apparatus aspect of the invention, there is provided a tool for use with a sensor, the sensor being of the type having an elongated wafer substrate with a predetermined width dimension and a predetermined thickness dimension. In this further apparatus aspect, the tool is provided with a first tool portion having an elongated channel that extends completely therealong for accommodating the predetermined thickness dimension of the sensor. The first tool portion is further provided with shoulder and handle portions, the shoulder portion having a thickness dimension that corresponds to the predetermined width dimension of the sensor. There is additionally provided a second tool portion having an end slot that accommodates therein an end portion of the sensor arrangement. The end slot is dimensioned to accommodate the predetermined thickness dimension of the sensor. 
     In one embodiment of this further apparatus aspect, the first tool portion is provided with a substantially rounded end portion in the vicinity of the shoulder portion. In another embodiment, the second tool portion is provided with a substantially rounded end portion in the vicinity of the end slot. Of course, in some embodiments, each of the first and second tool portions has a rounded end portion. 
     In a still further embodiment of the invention, the sensor is provided with a break-away portion having a predetermined length, and the end slot of said second tool portion has a depth dimension that corresponds to the predetermined length of the break-away portion. In this manner, the tool of the present invention will snap off the break-away portion of the sensor at a determined point along its length. 
     The tool of the present invention is particularly suite for use in connection with a sensor arrangement that has first and second substrates arranged in juxtaposed relation to each other. A working electrode is interposed between the first and second substrates. At least one of the first and second substrates has transaxial scoring for facilitating the snapping off of segments of the first and second substrates to expose a clean portion of the working electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which: 
         FIG. 1  is a simplified schematic representation of a sensor arrangement having snap-off segments for renewing the working electrode in accordance with the principles of the present invention; 
         FIG. 2  is a simplified cross-sectional schematic representation of a portion of the embodiment of the invention illustrated in  FIG. 1 ; 
         FIG. 3  is a simplified representation of an arrangement that is useful in the production of a specific illustrative embodiment of the invention; 
         FIG. 4  is a simplified schematic representation of an arrangement that is useful in the production of an embodiment of the invention that has a plurality of electrode wires; 
         FIG. 5  is a simplified schematic representation of a multi-electrode sensor arrangement having snap-off segments for renewing the working electrode in accordance with the principles of the present invention; 
         FIG. 6  is a simplified schematic representation of an arrangement that is useful in the production of an embodiment of the invention that has three electrode wires; 
         FIG. 7  is a simplified schematic representation of a multi-electrode sensor arrangement having snap-off segments for renewing the three working electrodes of  FIG. 6  in accordance with the principles of the present invention; 
         FIG. 8  is a perspective representation of a two-part tool for snapping off cleanly the snap-off segments of the multi-electrode sensor arrangement of the present invention; 
         FIG. 9  is a perspective representation of the two-part tool for snapping off cleanly the snap-off segments of the multi-electrode sensor arrangement of the present invention shown in  FIG. 9 , wherein the multi-electrode sensor arrangement is engaged with both parts of the two-part tool; 
         FIG. 10  is a perspective representation of a first portion of the two-part tool, this figure showing the early steps involved in manipulation of the tool; and 
         FIG. 11  is a perspective representation of the first and second portions of the two-part tool, this figure showing an intermediate step involved in manipulation of the tool. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a simplified schematic representation of a sensor arrangement  100  having snap-off segments  110   a  through  110   f , in this specific illustrative embodiment of the invention, for renewing a working electrode  112 . In this figure, the working electrode appears as but a dot and, in this specific illustrative embodiment of the invention, is shown as the cross-section of a wire, as will be discussed below in relation to  FIGS. 2 and 3 . 
     The wire of the present embodiment that constitutes working electrode  112  is interposed between substrates  120  and  122 . The two substrates are disposed in juxtaposition along a juncture  124 . In one embodiment, substrates  120  and  122  are respective printed circuit boards formed of conventional materials, such as polytetrafluoroethylene, phenolic cotton paper, cotton paper and epoxy, woven glass and epoxy, woven glass and polyester, matte glass and polyester, etc. Each of the substrates has deposited thereon an electrode. In the case of substrate  120 , there is deposited a silver pad  126  that serves as an electrode. Substrate  122  in this specific illustrative embodiment of the invention bears thereon a gold pad  128  (not shown in  FIG. 1 , see,  FIG. 2 ) that also serves as an electrode. It is to be understood that in some embodiments of the invention, silver pad  126  and/or gold pad  128  can extend over the entire length to sensor arrangement  100 , whereby a three-electrode system is renewed at the working tip. 
     Illustratively, the sensor of this particular embodiment comprises a sensor wire  112  that extends throughout the length of sensor arrangement  100 . The sensor wire may comprise any known metal or combination of metals, such as gold, platinum, gold/mercury, iridium, iridium/mercury, etc. While the sensor is shown here as a wire, it is to be understood that the sensor may be in any known form, such as an individual sensor or an array of sensors, formed by any technique such as screen-printing, lithography, or various deposition techniques. Potentiometric and voltammetric sensors are included within the scope of the present invention. 
     As sensor arrangement  100  is employed in use in an analyte (not shown), the working electrode becomes fouled resulting in inaccuracy and eventual near total loss of functionality. In accordance with the invention, the working electrode is renewed by snapping off segment  110   a  at the associated score mark (shown as a dashed line, not specifically designated), thereby presenting a clean portion of working electrode  112  to the analyte. Once the portion of the working electrode disposed at the proximal end of segment  110   a  becomes fouled, then segment  110   b  is removed exposing an additional clean portion of the working electrode. In this specific illustrative embodiment of the invention, this process is continued until segment  110   f  is snapped off, and once the clean portion of the working electrode proximal to segment  110   f  becomes fouled, the sensor is discarded. Thus, the useful life of an already inexpensive sensor arrangement is greatly extended. 
     Traditionally the working electrode always has been polished to create a mirrored surface and to clean it before the next analysis. It is expected that a clean surface provides reproducible results as recorded in a voltammetric curve known in the art as a “voltammogram.” The conventional cleaning of the surface of the electrode could in some instances be problematical as the surface of the electrode might be changed as it is modified (i.e., polished) with the abrasive materials (not shown) that are commonly used in the cleaning process, specifically diamond or alumina of different grit sizes. The present invention, however, provides a clean surface every time a segment is removed by snapping same off. The resulting surface might be irregular, but it will be clean. Basic qualitative analysis can be performed with such a surface, and if a quantitative analysis is required, standard curves can be made for determination of concentration. It is to be understood, however, that although the electrode of the present invention is intended for analytical sensor work, the sensor can be treated and polished in the conventional manner. 
     In some embodiments of the invention, the electrode surface is renewed, as herein described, preferably by snapping of segments of the electrode. However, in other embodiments, the electrode can be renewed by cutting, cleaving, or polishing. Although difficulty might arise when endeavoring to polish an entire multiple electrode system, one is nevertheless assured that the snapping off of electrode segments will result in a clean electrode surface. 
     A voltammogram represents results measured from an electrochemical cell (not shown), having three electrodes. These are, the reference electrode, the working electrode, and the counter electrode. The potential (voltage) is applied between the working and reference electrodes, and the responsive current is measured between the working electrode and the counter electrode. 
     The measurement of the current needs to be accurate and precise, and is responsive to the cross sectional area of the electrode to be the same. In addition, the measurement must itself be reproducible. This is effected by contamination (i.e., poisoning) of the electrode surface. Certain materials of chemical ions or species can become attached to the surface and not come off the surface when the electrode is used (voltage scanned). Such poisoning of the surface affects the overall current measured. 
     Electrochemists have used various techniques to clean the electrode between runs without the need for polishing. One such electrochemical technique cleans the electrode surface by pulse cleaning, whereby the potential is driven into an oxidative potential and then into a reductive potential before the electrode is used again. This technique pushes the contaminants off of the surface oxidatively, and then the potential of interest is applied to record a current, or the potential is scanned and the resulting variation in the current is observed as a voltammogram. However, when the electrode cannot be renewed in this simple fashion more aggressive steps, such as polishing or snapping off of a segment in accordance with the invention, are required. 
     In embodiments of the invention that are intended for extended use, mechanisms may be employed (not shown) that automatically snap off the electrode segments to renew the electrode when required. The need for electrode renewal would become apparent when the data collected on periodic standard solutions (not shown) varies. 
     In a specific illustrative embodiment of the invention, sensor arrangement  100  is approximately 5″ long (including the snap-off segments) and ¼″ wide. Each of the snap-off segments is approximately ¼″ long along the principal axis (not specifically designated). However, it is understood that these dimension are merely illustrative, and any other suitable dimensions can be employed in the practice of the invention. In some embodiments of the invention, the width of the sensor arrangement is responsive to the number of wires therewithin. 
       FIG. 2  is a simplified cross-sectional schematic representation of a portion of sensor arrangement  100  illustrated in  FIG. 1 , the representation of  FIG. 2  being significantly enlarged to reveal the internal structure of the sensor arrangement of the present embodiment of the invention. Elements of structure that have previously been discussed are similarly designated. As shown in this figure, working electrode  112 , in this specific illustrative embodiment of the invention, is a gold wire that, as previously indicated, is interposed between substrates  120  and  122 . In some embodiments of the invention the working electrode, rather than being in the form of a wire as shown herein, is printed on, or deposited onto, one or both of the substrates. More that one such working electrode (not shown in this figure) can easily be employed in the practice of the invention, while maintaining the significant advantage achieved by the snapping off of sensor segments to renew multiple working electrodes simultaneously. Also, different working materials can be employed within a single sensor. 
     As previously noted, silver pad  126  is disposed on substrate  120 . This figure shows a specific illustrative embodiment of the invention wherein a gold pad  128  is disposed on substrate  122 . 
       FIG. 3  is a simplified representation of an arrangement that is useful in the production of a specific illustrative embodiment of the invention. As shown in this figure, a substrate  130  is provided with studs  132  and  134  about which are wound gold wire  112 . An adhesive (not shown) is then deposited over the substrate and the gold wire, and a second substrate (not shown) is placed over substrate  130  whereby gold wire is disposed between the substrates. In the practice of this aspect of the invention, the overall length of substrate  130  is approximately 6″. 
     In some embodiments of the invention, one of the substrates is provided with an axial channel (not shown) that accommodates the gold wire. In other embodiments, the working electrode is deposited or printed onto the substrate. Multiple gold wires or other working material can be printed or deposited as working electrodes within a single sensor arrangement within the scope of the present invention. 
       FIG. 4  is a simplified schematic representation of an arrangement that is useful in the production of an embodiment of the invention that has a plurality of electrode wires, specifically electrode wires  112   a  and  112   b . Elements of structure that have previously been discussed are similarly designated. In a specific illustrative embodiment of the invention, one or both of electrode wires  112   a  and  112   b  are made of gold. However, other suitable electrode materials, such as silver, platinum, and the like, can be used in the practice of the invention. 
     The invention is not limited to the numbers of electrode wires (or conductors) shown in the figures. Moreover, the working electrodes are not limited in the practice of the invention to wires, and may be formed by any of several known printing or deposition processes. 
       FIG. 5  is a simplified schematic representation of a multi-electrode sensor arrangement  200  having snap-off segments as hereinabove described for renewing a plurality of working electrodes in accordance with the principles of the present invention. Elements of structure that have previously been discussed are similarly designated. In this embodiment of the invention, two working electrode wires  112   a  and  112   b  are disposed between substrates  120  and  122 . As described above in relation for  FIG. 1 , the working electrodes are renewed by snapping off segments. The snap-off segments are shown to be separable at regions of reduced substrate thickness, but are not specifically designated in this figure. As shown in this figure, working electrode wires  112   a  and  112   b  extend beyond the distal end of substrates  120  and  122  to facilitate electrical connection to a monitoring system (not shown). 
       FIG. 6  is a simplified schematic representation of an arrangement that is useful in the production of an embodiment of the invention that has three electrode wires. Elements of structure that have previously been discussed are similarly designated. In this specific illustrative embodiment of the invention, electrode wires  112   a ,  112   b , and  112   c  are formed of gold silver, and platinum electrode materials, respectively. 
       FIG. 7  is a simplified schematic representation of a multi-electrode sensor arrangement  300  having snap-off segments for renewing the three working electrodes of  FIG. 6  in accordance with the principles of the present invention. Elements of structure that have previously been discussed are similarly designated. In this embodiment, the entire three-electrode system, which would constitute in some embodiments the working and reference electrodes, is renewable at the tip. Thus, silver pad  126  and gold pad  128  are not necessary, depending upon the intended application. 
     There is additionally shown in this embodiment of the invention a terminal block  150  that facilitates the electrical communication between the working electrode wires and monitoring equipment (not shown). In some embodiments, conductive pads (not shown) are used instead of a terminal block to provide electrical access to the electrode wires. In the present embodiment, working electrode wires  112   a ,  112   b , and  112   c  communicate electrically with respectively associated ones of terminals  150   a ,  150   b , and  150   c , of terminal block  150 . 
     It is to be understood that the multi-electrode sensor arrangement of the present invention is not limited to the substantially rectangular cross-sectional configurations illustrated in the foregoing figures as multi-electrode sensor arrangements  100 ,  200 , and  300 . The multi-electrode sensor arrangements can be configured to have any cross-sectional shape including, for example, a round, oval, or polygonal cross-sectional configuration. 
     In addition, the multi-electrode sensor arrangement bodies can be formed of any of a variety of materials, including, for example, a polymer or plastic material, or polyetheretherketone (PEEK), or a ceramic material, such as alumina oxide, which typically contains about 70-80% aluminum oxide and small amount of silica (SiO 2 ), MgO, and zirconia (ZrO 2 ). Such ceramic materials have excellent electrical insulating properties. 
       FIG. 8  is a perspective representation of a two-part tool  500  formed of tool portion  510  and tool portion  530  for snapping off cleanly the snap-off segments (not specifically designated) of multi-electrode sensor arrangement  550 . Multi-electrode sensor arrangement  550  is configured in accordance with the inventive sensor described herein in relation to  FIGS. 1-7 . Two-part tool  500  is particularly adapted for achieving a clean break in multi-electrode sensor arrangement  550  which, as described hereinabove, employs a wire electrode (not specifically designated in this figure). It is an advantage of the use of two-part tool  500  that the clean break of the snap-off segments (not specifically designated) results in cross-sectionally consistent presentation of the wire electrode with each renewal of multi-electrode sensor arrangement  550 . This ensures consistent and repeatable analytical results as multi-electrode sensor arrangement  550  is renewed. 
       FIG. 8  additionally shows that tool portion  510  is provided with an elongated channel  512  that accommodates multi-electrode sensor arrangement  550 . Tool portion  530  has a relatively short slot  532  the accommodates a segment of multi-electrode sensor arrangement  550  that is to be snapped off. In a highly advantageous embodiment of the invention, slot  532  has an axial depth dimension that is consistent with the dimension of the snap-off segment (not specifically designated in this figure). 
       FIG. 9  is a perspective representation of the two-part tool for snapping off cleanly the snap-off segments of the multi-electrode sensor arrangement of the present invention shown in  FIG. 9 , wherein the multi-electrode sensor arrangement is engaged with both parts of the two-part tool. Elements of structure that have previously been discussed are similarly designated. 
     Tool portion  510  is shown in  FIGS. 8 and 9  to have a shoulder portion  514  having a thickness that is dimensioned to conform to the width of multi-electrode sensor arrangement  550 . Tool portion  530 , at least in the region of slot  532 , has a similar thickness. Thus, the width of multi-electrode sensor arrangement  550  is fully accommodated in shoulder portion  514  and in slot  532  of tool portion  530 . Tool portion  510  is further shown to have a handle portion  516  that is, in this embodiment of the invention, formed integrally with shoulder portion  514 . Handle portion  516  is not as deep as shoulder portion  514 , and therefore multi-electrode sensor arrangement  550  protrudes therefrom so as to enable multi-electrode sensor arrangement  550  to be held in place by the hand of the user, as will be described below in connection with  FIGS. 10 and 11 . 
     Tool portion  510  is shown to have a rounded end portion  518 . Similarly, tool portion  530  has a rounded end portion  534 . As will be described below in connection with  FIG. 12 , the rounded portions facilitate the snapping-off action whereby a segment of multi-electrode sensor arrangement  550  (not specifically designated in this figure) is snapped off and the electrode is renewed by exposing unused cross-sectional portions of the electrode wire(s) (not shown in this figure). 
       FIG. 10  is a perspective representation of tool portion  510  of the two-part tool with multi-electrode sensor arrangement  550  extending axially therefrom. Elements of structure that have previously been discussed are similarly designated. This figure represents an initial step in the use of the tool of the present invention. As shown in this figure, multi-electrode sensor arrangement  550  is installed in tool  510 , and the portion of multi-electrode sensor arrangement  550  that extends outward of handle portion  516  communicates with the hand of the user (not specifically designated). Multi-electrode sensor arrangement  550  is shown to have a transaxial score  552  that facilitates the snapping off of sensor segment  554 . IN this specific illustrative embodiment of the invention, multi-electrode sensor arrangement  550  is scored with transaxial score  552  on only one side. In other embodiments, however, multi-electrode sensor arrangement  550  can be scored on both sides, as shown in  FIGS. 5 and 7 . 
       FIG. 11  is a perspective representation of the first and second portions of the two-part tool, this figure showing an intermediate step involved in manipulation of the tool. Elements of structure that have previously been discussed are similarly designated. As shown in this figure, slot  532  of tool portion  530  is dimensioned such that transaxial score  552  is disposed precisely where tool portions  510  and  530  communicate with one another, at their respective rounded portions  518  and  534 . Thus, when tool portion  530  is manipulated several times in the directions of two-headed arrow  560 , rounded portion  518  and  534  essentially roll against one another, flexing multi-electrode sensor arrangement  550  at transaxial score  552 , whereby fatiguing results at the score and the snap-off action occurs. 
     Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art can, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention described and claimed herein. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof.