Patent Publication Number: US-2022212187-A1

Title: Liquid sensor assemblies, apparatus, and methods

Description:
This application claims priority to U.S. provisional application No. 62/839,827, filed Apr. 29, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates to test sensors and sensing methods, and particularly to test sensor assemblies configured to test for a presence of one or more constituents within a test liquid, such as in a biological liquid specimen (bio-liquid specimen). 
     BACKGROUND 
     In liquid testing, such as in analyte testing of a bio-liquid specimen, a volume of a test liquid (e.g., whole blood, blood serum, or blood plasma) can be provided in a pathway and sensors contained in the pathway can be used to sense certain identifiable constituents contained in the bio-liquid specimen. 
     SUMMARY 
     Some embodiments of the present disclosure provide a sensor assembly configured to sense the presence of one or more constituents within a bio-liquid specimen. 
     Some embodiments of the present disclosure provide a sensor assembly configured to measure an amount of one or more analytes contained in a bio-liquid specimen obtained from a patient, wherein the available test liquid volume is very small, such as less than 100 μL, or even less than 50 μL in some embodiments. 
     Some embodiments of the present disclosure provide a sensor assembly configured to sense the presence of one or more constituents within a bio-liquid wherein the sensor assembly includes a single reference electrode. 
     Some embodiments of the present disclosure provide a sensor assembly wherein the sensor assembly includes more working electrodes than reference electrodes, not in a 1:1 ratio. 
     Embodiments of the present disclosure provide a sensor assembly configured to minimize an amount of test liquid (e.g., bio-liquid specimen) used therein. The sensor assembly comprises a flow channel; two or more working electrodes located in the flow channel; and one or more reference electrodes located in the flow channel, wherein a total number of working electrodes is greater than a total number of reference electrodes. 
     In a system aspect, a liquid testing apparatus is provided. The liquid testing apparatus comprises a flow channel; two or more working electrodes located in the flow channel; and one or more reference electrodes located in the flow channel, wherein a total number of working electrodes is greater than a total number of reference electrodes; and a controller coupled to the one or more reference electrodes and the two or more working electrodes, the controller configured to measure a voltage potential between at least one of the two or more working electrodes and at least one of the one or more reference electrodes. 
     According to another aspect of the present disclosure, a method of testing a test liquid is provided. The method comprises providing a flow channel, two or more working electrodes located in the flow channel, one or more reference electrodes located in the flow channel, wherein a total number of working electrodes is greater than a total number of reference electrodes; flowing a test liquid through the flow channel; and measuring one or more voltage potentials between the one or more reference electrodes and the two or more working electrodes. 
     Still other aspects, features, and advantages of the present disclosure may be readily apparent from the following detailed description by illustrating a number of example embodiments and implementations. The present disclosure may also be capable of other and different embodiments, and its several details may be modified in various respects, all without departing from the scope of the present disclosure. Further features and aspects of embodiments will become more fully apparent from the following detailed description, the claims, and the accompanying drawings. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. The disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, described below, are for illustrative purposes and are not necessarily drawn to scale. The drawings are not intended to limit the scope of the disclosure in any way. Like numerals are used throughout the specification and drawings to denote like elements. 
         FIG. 1A  illustrates a top plan view of a sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 1B  illustrates a cross-sectioned side view of a sensor assembly taken along section line  1 B- 1 B of  FIG. 1A  illustrating an example construction of primary and secondary channels within the sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 1C  illustrates a top plan view of an intermediate layer of a sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 1D  illustrates a bottom plan view of a first layer of a sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 1E  illustrates a top plan view of a second layer of a sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 1F  illustrates a side cross-sectioned side view of a sensor assembly with some components removed according to one or more embodiments of the disclosure. 
         FIG. 2  illustrates a schematic diagram of a circuit that measures voltage potential(s) between one or more working electrodes and a reference electrode in a sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 3  illustrates a schematic diagram of a liquid testing apparatus including an embodiment of a sensor assembly including primary and secondary channels according to one or more embodiments of the disclosure. 
         FIG. 4  illustrates a cross-sectioned side view of a sensor assembly illustrating an example construction of a flow channel within the sensor assembly according to one or more embodiments of the disclosure. 
         FIG. 5  illustrates a flowchart of a method of testing a test liquid according to one or more embodiments of the disclosure. 
         FIG. 6  illustrates a flowchart of another method of testing a test liquid according to one or more embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In some chemical tests, it may be desirable to test for more than one constituent in a test liquid (e.g., a bio-liquid specimen) at a time. For example, a sensor assembly that can test for eight or more different constituents at a time is desirable. Moreover, in some instances the available volume of the test liquid (e.g., blood serum or plasma or other bio-liquid) to be tested may be quite small, such as when taken from, for example, a neonatal patient. Neonatal patient as used herein means an infant of less than 28 days of age. In certain instances, it may be desirable to not only test for multiple constituents at one time in one sensor assembly because but the available volume of test liquid available for the tests may be relatively small in volume, such as less than 100 μl or even less than 50 μl in some embodiments, for example. 
     Prior art sensor assemblies include chemical sensors, such as potentiometric sensors that measure the concentrations of specific chemical constituents in a test liquid. Each of the potentiometric sensors includes a reference electrode and a working electrode. A charge that is proportional to a constituent being measured develops on each of the working electrodes. By measuring the electric potential between the reference electrode and the working electrode of each potentiometric sensor, the concentration of the different constituents can be measured. 
     As described above, each potentiometric sensor in the prior art sensor assemblies includes two electrodes, the working electrode and the reference electrode. Thus, a sensor assembly that measures the concentrations of four constituents, for example, has eight electrodes. The sensor assemblies described herein include a common reference electrode that is associated with two or more working electrodes. Therefore, a sensor assembly that measures the concentrations of four constituents may have as few as five electrodes. It follows that the cumulative sensor sizes of the sensor assemblies described herein may be smaller than the cumulative sensor sizes of prior art sensor assemblies. The smaller cumulative sensor sizes described herein enable the sizes of the sensor assemblies described herein to be smaller than prior art sensor assemblies. As a result, the volume of test liquid used by the sensor assemblies described herein may be less than the volume of test liquid used in prior art sensor assemblies. In addition, the working electrodes may be arranged to face each other, which concentrates the working electrodes in smaller areas. This working electrode arrangement may further reduce the sizes of the sensor assemblies and the volume of test liquid used in the sensor assemblies. 
     Some reference electrodes in conventional sensor assemblies may interfere with their working electrodes. For example, the reference electrodes may emit small traces of chemicals that may interfere with the working electrodes. Some embodiments of the sensor assemblies described herein include one or more primary flow channels spaced from a secondary flow channel. The primary flow channels may each contain one or more working electrodes and the secondary flow channel may contain the reference electrode. Accordingly, the reference electrode is spaced a distance from the working electrodes, which may reduce the interference. In some embodiments, the reference electrode is located downstream of the working electrodes, which may further reduce the probability of the reference electrode interfering with the working electrodes. In some embodiments the secondary flow channel, including the reference electrode, is (vertically) offset from the primary flow channels, so the reference electrode is further spaced from the working electrodes. 
     Accordingly, in one aspect, an improved sensor assembly is provided that enables the carrying out of liquid testing (e.g., bio-liquid specimen testing) of multiple constituents simultaneously. In another aspect, the liquid testing can be carried out in some embodiments while utilizing a relatively small volume of the test liquid, such as when the test liquid comes from a neonatal patient. These and other aspects and features of the present disclosure will be described with reference to  FIGS. 1A-4  herein. 
     In accordance with a first embodiment of the disclosure, as best shown in  FIGS. 1A-1F and 4 , sensor assemblies  100 ,  400  are provided. The sensor assemblies  100 ,  400  are configured to enable liquid testing (e.g., bio-liquid specimen testing). In some embodiments, the bio-liquid specimen testing can be while using only a small volume of the test liquid, although the bio-liquid specimen testing by the sensor assemblies  100 ,  400  can also be used for adult patients. Although the present disclosure is generally focused on microfluidics and testing small volumes of test liquids (e.g., bio-liquids), the present disclosure is applicable to testing of other volumes of test liquids as well as testing for the presence of and/or concentration of multiple constituents in non-bio-liquid specimens. 
     Reference is now made to  FIGS. 1A, 1B, and 1C .  FIG. 1A  illustrates a top plan view of an embodiment of the sensor assembly  100 .  FIG. 1B  illustrates a cross-sectioned side view of an embodiment of the sensor assembly  100  taken along section line  1 B- 1 B of  FIG. 1A .  FIG. 1C  illustrates an intermediate layer of the sensor assembly  100 . The sensor assembly  100  includes a primary body  102  and a secondary body  104  that may be coupled together. The primary body  102  includes one or more primary channels that enable a test liquid to flow through the primary body  102 . The embodiments described herein may include a flow channel  106  including a first primary channel  106 A and a second primary channel  106 B located within and formed in part by an intermediate layer  107  described below. The secondary body  104  includes a secondary channel  108  that is connected to and fluidly coupled in use to one or more of the first primary channel  106 A and the second primary channel  106 B. The first primary channel  106 A may be referred to as a first flow channel portion, the secondary channel  108  may be referred to as a second flow channel portion, and the second primary channel  106 B may be referred to as a third flow channel portion. The first primary channel  106 A includes a first primary inlet  110 A that may be located proximate a first end  111 A of the first primary channel  106 A. A first primary outlet  110 B may be located proximate a second end  111 B of the first primary channel  106 A. The first primary inlet  110 A may be configured to couple to the test liquid source, such as an inlet channel  354  ( FIG. 3 ) formed in or as a part of the testing equipment the sensor assembly  100  is operative with. The inlet channel  354  can supply a test liquid  353  (e.g., bio-liquid specimen) from a reservoir  355  ( FIG. 3 ) to be tested by the sensor assembly  100 . Any suitable pump  356  may be provided to transfer the test liquid  353  from the reservoir  355  through the inlet channel  354  and into the first primary inlet  110 A of the sensor assembly  100 . 
     The first primary outlet  110 B may be connected and coupled to a secondary channel inlet  112 A located proximate a first end  113 A of the secondary channel  108 . The secondary channel  108  may include a secondary channel outlet  112 B located proximate a second end  113 B of the secondary channel  108 . The secondary channel outlet  112 B may be connected and coupled to a second primary inlet  114 A located proximate a first end  115 A of the second primary channel  106 B. A second primary outlet  114 B may be located proximate a second end  115 B of the second primary channel  106 B. The second primary outlet  114 B may be configured to be connected and coupled to an outflow channel  357  that can be connected to a receptacle (e.g., waste receptacle  358 ,  FIG. 3 ) that collects the test liquid  353  being expelled from the sensor assembly  100  after testing is completed. 
     A liquid flow path extends through the sensor assembly  100  between the first primary inlet  110 A and the second primary outlet  114 B as shown by the dotted arrows in  FIG. 1B . The first primary inlet  110 A may be coupled to a source of a test liquid (e.g., test liquid  353 ,  FIG. 3 ). The test liquid  353  enters the sensor assembly  100  via the first primary inlet  110 A, where the test liquid flows through the first primary channel  106 A. The test liquid  353  exits the first primary channel  106 A at the first primary outlet  110 B and enters the secondary channel  108  via the secondary channel inlet  112 A. The test liquid  353  then flows through the secondary channel  108  and exits via the secondary channel outlet  112 B to the second primary inlet  114 A. The test liquid  353  then flows through the second primary channel  106 B to the second primary outlet  114 B where the test liquid  353  exits the sensor assembly  100  through outflow channel  357 . 
     As shown in  FIG. 1B , the channels have end barriers that cause the test liquid to transition between the first primary channel  106 A, the secondary channel  108 , and the second primary channel  106 B. As shown, the secondary channel  108  is located on a plane that is different than planes where at least one of the first primary channel  106 A and the second primary channel  106 B are located. In some embodiments, the first primary channel  106 A and the second primary channel  106 B may be located on the same plane. In other embodiments, the first primary channel  106 A and the second primary channel  106 B may be located on different planes. In other embodiments, the first primary channel  106 A, the second primary channel  106 B, and the secondary channel  108  may all be located on different planes. The transition between the plane of the secondary channel  108  and a plane of at least one of the first primary channel  106 A and the second primary channel  106 B may constitute the physical barrier between the secondary channel  108  and at least one of the first primary channel  106 A and the second primary channel  106 B. 
     The primary body  102  may include three layers as shown, including a first layer  120 , a second layer  122 , and the intermediate layer  107 . Additional reference is made to  FIG. 1D , which illustrates a bottom plan view of the first layer  120 . Additional reference is also made to  FIG. 1E , which illustrates a top plan view of the second layer  122 . The first layer  120  includes an outer side  120 A and an inner side  120 B. The second layer  122  also includes an outer side  122 A and an inner side  122 B. The intermediate layer  107  includes a first side  107 A and a second side  107 B. The inner side  120 B of the first layer  120  may be bonded to or otherwise fastened to the first side  107 A of the intermediate layer  107  so as to form a sealed interface there between. The inner side  122 B of the second layer  122  may be bonded to or otherwise fastened to the second side  107 B of the intermediate layer  107  so as to form a sealed interface there between. The secondary body  104  may be coupled to or otherwise fastened to the outer side  120 A of the first layer  120  so as to form a sealed interface there between. 
     The intermediate layer  107  may be formed from a gasket-type material. For example, the intermediate layer  107  may be impermeable to liquids that flow between the first primary inlet  110 A and the second primary outlet  114 B. The intermediate layer  107  may seal with the inner side  120 B of the first layer  120  and the inner side  122 B of the second layer  122  so as to prevent liquids from leaking from the sensor assembly  100 . 
     As shown in  FIG. 1C , the intermediate layer  107  may have portions of the first primary channel  106 A and the second primary channel  106 B formed therein. For example, the first primary channel  106 A and the second primary channel  106 B may extend fully between the first side  107 A and the second side  107 B of the intermediate layer  107 . The first primary channel  106 A can be elongated having a length L 11  extending between the first end  111 A and the second end  111 B. The first primary channel  106 A has a width W 11  extending between a first side  124 A and a second side  124 B. The second primary channel  106 B can be elongated having a length L 12  extending between the first end  115 A and the second end  115 B. The second primary channel  106 B has a width W 12  extending between a first side  126 A and a second side  126 B. In some embodiments, the width W 11  may be approximately the width of at least one of the first primary inlet  110 A and the first primary outlet  110 B. In some embodiments, the width W 12  may be approximately the width of at least one of the second primary inlet  114 A and the second primary outlet  114 B. 
     The first primary channel  106 A may have a height H 11  ( FIG. 1B ) extending between the inner side  120 B of the first layer  120  and the inner side  122 B of the second layer  122 . The second primary channel  106 B may have a height H 12  extending between the inner side  120 B of the first layer  120  and the second side  132 B of the second layer  122 . In some embodiments, the height H 11  and/or the height H 12  may be approximately the thickness of the intermediate layer  107 . In some embodiments, the height H 11  may be approximately the same as the height H 12 . 
     In some embodiments, the length L 11  of the first primary channel  106 A may be equal to the length L 12  of the second primary channel  106 B. In some embodiments at least one of the length L 11  and the length L 12  may be in a range from 8 mm to 16 mm each, for example. In some embodiments, the width W 11  may be equal to the width W 12 . In some embodiments at least one of the width W 11  and the width W 12  may be in a range from 0.056 mm to 0.94 mm, for example. In some embodiments, the height H 11  and the height H 12  can be in the range from 0.38 mm to 0.63 mm, for example. In some embodiments, the height H 11  may be equal to the height H 12 . The secondary channel  108  may have dimensions equal to or approximate the dimensions of at least one of the first primary channel  106 A and the second primary channel  106 B. In some embodiments, the length of the secondary channel  108  may be shorter than at least one of the first primary channel  106 A and the second primary channel  106 B. Other suitable dimensions can be used. 
     Additional reference is made to  FIG. 1F , which illustrates a side cross-sectioned view of the sensor assembly  100  with some components removed and or not referenced for illustration purposes. The sensor assembly  100  may include one or more working electrodes  130 A- 130 H and at least one reference electrode  132  that form one or more sensors, such as potentiometric sensors. For example, the reference electrode  132  forms at least one potentiometric sensor with at least one of the working electrodes  130 A- 130 H. In the depicted embodiment of  FIG. 1E , the sensor assembly  100  include eight working electrodes  130 , which are referred to individually as working electrodes  130 C- 130 D and  130 G- 130 H. The working electrodes  130 C- 130 D and  130 G- 130 H located in the first primary channel  106 A may be referred to as the first working electrodes and the working electrodes  130 A- 130 B and  130 E- 130 F located in the second primary channel  106 B may be referred to as the second working electrodes. The sensor assembly  100  may include different numbers of working electrodes  130 . The working electrodes  130  may be made of any suitable conductive material, such as metal foil, conductive ink, or the like, and combinations thereof. 
     A controller  136  may be electrically coupled to the working electrodes  130 A- 130 H and also the reference electrode  132 . In some embodiments, the controller  136  may supply a reference voltage to the reference electrode  132 . The controller  136  may measure respective voltage potentials between each of the individual working electrodes  130 A- 130 H and the reference electrode  132 . Based on the voltage potentials, the controller  136  may determine the concentration of specific analytes or chemical constituents in the test fluid  353  as described below. 
     Additional reference is made to  FIG. 2 , which illustrates an example embodiment of a circuit  240  within the controller  136  that may be utilized to measure the potential voltages (the electro-motive force (EMF)) between each of the working electrodes  130 A- 130 H and the reference electrode  132 . The circuit  240  may include a switching device  242 , such as an electronic switch that selectively couples one or more working electrodes  130 A- 130 H to a voltage measuring device  244 . The voltage measuring device may be any suitable device that operates to measure the voltage potential (EMF) between the selected working electrodes  130 A- 130 H and the reference electrode  132 . 
     As described above, the working electrodes  130 A- 130 H and the reference electrode  132  may form potentiometric sensors. Potentiometric sensors are a type of chemical sensor that may be used to determine the concentration of some components of a gas or a liquid. Potentiometric sensors measure the electrical potential between a respective working electrode  130 A- 130 H and the reference electrode  132  when no current is conducting between the working electrodes  130  and the reference electrode  132 . Thus, each of the individual working electrodes  130 A- 130 H may be an individual potentiometric sensor referenced to the common reference electrode  132 . A single reference electrode is shown. However, in some embodiments a first reference sensor may be configured to be used with a first grouping of working electrodes and a second reference sensor may be configured to be used with a second grouping of working electrodes. 
     Each of the working electrodes  130 A- 130 H may include a membrane or the like including a particular selective reagent that reacts with a specific analyte in the test liquid  353 . For example, the membrane can react with specific analytes such as sodium, potassium, calcium, or chloride. These reactions accumulate charges on the working electrodes  130 , which then can be measured as electric potentials between the individual working electrodes  130 A- 130 H and the reference electrode  132 . The amount of charge accumulated on a working electrode is proportional to the analyte concentration in the test liquid  353 , which is proportional to the potential between the respective working electrode  130 A- 130 H and the reference electrode  132 . The potential of a potentiometric sensor is based on the Nernst equation (1), which predicts a linear dependence of the potential, E, on the logarithm of a function of the activity of specific ions the test solution as follows: 
     
       
         
           
             
               
                 
                   E 
                   = 
                   
                     
                       E 
                       ∘ 
                     
                     + 
                     
                       
                         
                           R 
                           ⁢ 
                           T 
                         
                         
                           n 
                           ⁢ 
                           F 
                         
                       
                       ⁢ 
                       ln 
                       ⁢ 
                       
                         a 
                         i 
                       
                     
                   
                 
               
               
                 
                   
                     ( 
                     1 
                     ) 
                   
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Nernst 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   Equation 
                 
               
             
           
         
       
     
     where E is the potential between the working electrode and the reference electrode  132 , R is the gas coefficient (8.314 J/K), F is the faraday constant (96,500 C/mol), n is the number of electrons, and a i  is the activity of the ion being detected. E° is a potential applied to the reference electrode  132 . The controller  136  may calculate the concentration of an analyte in the test liquid  353  based on the Nernst equation. 
     The potentials of different working electrodes  130 A- 130 H may be measured relative to the reference electrode  132  to measure concentrations of specific analytes within the test liquid  353 . Different analytes may be measured by different ones of the working electrodes. For example each working electrode  130 A- 130 H may include a different selective reagent applied thereto, so that a large number of analytes can be tested on the test liquid  253 . 
     In some embodiments, the working electrodes  130 A- 130 H may be grouped to form microsensors that may measure microsamples in the test liquid  353 . For example, the working electrodes  130 A,  130 B,  130 E, and  130 F, which are downstream from the reference electrode  132  may constitute a first microsensor. The working electrodes  130 C,  130 D,  130 G, and  130 H, which are upstream of the reference electrode  132  may constitute a second microsensor. The working electrodes  130 B,  130 C,  130 F, and  130 G, which are located closest to the reference electrode  132  may constitute a third microsensor. Other arrangements of the working electrodes  130  may form other microsensors. 
     The working electrodes in the first primary channel  106 A may be referred to as the first working electrodes and the working electrodes in the second primary channel  106 B may be referred to as the second working electrodes. At least one of the first working electrodes and the second working electrodes may include a first working electrode and a second working electrode, wherein the first working electrode faces the second working electrode across the first primary channel  106 A. For example, referring to  FIG. 1F , the working electrode  130 C faces the working electrode  130 G. In some embodiments, the first working electrode and the second working electrode are located on opposite sides of at least one of the first primary channel  106 A and the second primary channel  106 B. In some embodiments, the first working electrodes and/or the second working electrodes include two or more working electrodes arranged along a length of the first primary channel  106 A and/or the second primary channel  106 B. In some embodiments, the first working electrodes include a first array of working electrodes arranged along a length of the first primary channel  106 A and a second array of working electrodes arranged along a length of the first primary channel  106 A, wherein the first array of working electrodes faces the second array of working electrodes. Such an arrangement is shown by the working electrodes  130 C,  130 D,  130 G, and  130 H. The same arrangement may apply to the second primary channel  106 B. 
     Some reference electrodes in conventional sensor assemblies interfere with their working electrodes. For example, the reference electrodes may emit small traces of chemicals that may interfere with the working electrodes  130 . Secondary channel  108  described herein includes the reference electrode  132  contained therein. Accordingly, the reference electrode  132  is spaced a distance from the working electrodes  130 C- 130 D and  130 G- 130 H located upstream from the reference electrode  132 , which reduces the probability of the reference electrode  132  interfering with these working electrodes  130 C- 130 D and  130 G- 130 H. In addition, by offsetting the secondary channel  108  including the reference electrode  132  from the first primary channel  106 A and/or the second primary channel  106 B, the reference electrode  132  is further spaced from the working electrodes  130 , as they are located in different planes. 
     Conventional sensor assemblies using potentiometric sensors include a reference electrode and a working electrode for every potentiometric sensor. Accordingly, every sensing location in conventional sensor assemblies consume relatively large areas. Sensing in the sensor assembly  100  is performed by each of the working electrodes  130 A- 130 H in conjunction with the single reference electrode  132  that is spaced from the location of the working electrodes  130 A- 130 H. Accordingly, the sensing locations of the sensor assembly  100  may be much smaller than the sensing locations of conventional senor assemblies. Optionally, they may be made larger to possibly improve signal strength. 
     For example, a sensing location may only include a working electrode. Thus the sensing location may be much smaller than in conventional potentiometric sensors. Thus, the flow channel  106  in which test liquid  353  flows within the sensor assembly  100  may be smaller than those in conventional sensor assemblies. Although the sensor assembly  100  includes the secondary channel  108 , the overall volume of the secondary channel  108 , the first primary channel  106 A, and the second primary channel  106 B may be less than the volume of channels in conventional sensor arrays because the sensing locations may be smaller. For example, volume of the first primary channel  106 A, the second primary channel  106 B, and the secondary channel  108  can be less than 100 μl, or from 50 μl to 100 μl in some embodiments. The first primary channel  106 A, the second primary channel  106 B, and the secondary channel  108  can have other volumes. 
     The sensor assembly  100  can be configured to test for a concentration of a constituent in various types of the test liquid  353 . For example, the test liquid can be a bio-liquid selected from a group of whole blood, blood serum or plasma, urine, cerebrospinal fluid (CSF), dialysate, serous fluid (such as pleural fluid, pericardial fluid, and peritoneal fluid), interstitial fluid, synovial fluid, intraocular fluid, lymph plasma, digestive fluid, and human tissue-containing liquid. Other bio-liquids and other types of non-bio-liquids can be tested. In other embodiments, the sensor assembly  100  can be configured to test for concentrations of two or more constituents contained in the test liquid  353  flowing through the flow channel  106 . 
     In  FIG. 3 , an embodiment of a liquid testing apparatus  350  utilizing a sensor assembly  100  including one or more primary channels  106 A,  106 B and a secondary channel  108  is illustrated. The sensor assembly  100  used in this embodiment can be positioned in a horizontal orientation as shown. Other orientations are possible. In operation, the reservoir  355  can receive a test liquid  353  by any suitable means. For example, the test liquid  353  can be injected therein (indicated by arrow  352 ), such as by a syringe or other injection mechanism coupleable to the reservoir  355 . A pump  356  coupled to or operative within the reservoir  355 , such as a pressure pump, piston pump, or the like, can be actuated via control signals from the controller  136 . As a result, some, or all, of the test liquid  353  is moved by the pump  356 . Any suitable liquid moving system can be used. 
     The test liquid  353  then flows through inlet channel  354  and into the first primary inlet  110 A. One or more valves may be included in the channel or associated with the pump  356  to control the extent of flow and to stop flow as desired. In other embodiments, the pump  356  is precise and can control the flow volume precisely. 
     With additional reference  FIG. 1B , the test liquid  353  flows through the first primary channel  106 A into the secondary channel inlet  112 A, through the secondary channel  108 , into the second primary inlet  114 A, through the second primary channel  106 B, and out the second primary outlet  114 B. As the test liquid  353  flows through the first primary channel  106 A and the second primary channel  106 B, the test liquid  353  contacts each of the working electrodes  130 A- 130 H. As the test liquid  353  flows through the secondary channel  108 , the test liquid  353  contacts the reference electrode  132 . 
     The tests can be run and the analyte measurements can be obtained from each of the working electrodes  130 A- 130 H in combination with the reference electrode  132  by communication with the controller  136  and by way of conventional computations. The controller  136  may be communicatively coupled to a laboratory information system (LIS)  370 , for example, so that analyte concentrations from the test can be promptly sent to the originator/requestor or elsewhere. 
     Following each test, a valve (not shown) can be opened to flow a wash liquid  375  from a wash liquid source  376  to and through the reservoir  355 , inlet channel  354  and the sensor assembly  100  and finally to a waste receptacle  358 . The primary channels  106 A,  106 B and the secondary channel  108  receiving the wash liquid  375  cleans and readies the sensor assembly  100  for the next test on a new test liquid  353 . Multiple washes may be undertaken in some embodiments. 
     Another embodiment of a sensor assembly  400  is illustrated in  FIG. 4 . The sensor assembly  400  includes a continuous flow channel  406  that may be located on a single plane and that may be straight between an inlet  410  and an outlet  414 . The flow channel  406  may be formed in the same or similar manner as the first primary channel  106 A and the second primary channel  406 B. The inlet  410  may function in the same or similar manner as the first primary inlet  110 A of  FIG. 1B  and the outlet  414  may function in the same or similar manner as the second primary outlet  114 B of  FIG. 1B . In some embodiments, the dimensions of the sensor assembly  400  may be the same or substantially similar to the dimensions of the primary body  102  ( FIG. 1B ) of the sensor assembly  100 . 
     The sensor assembly  400  may include the reference electrode  132  and two or more working electrodes  130 . In some embodiments, the sensor assembly  400  includes one or more reference electrodes, wherein a number of working electrodes is greater than a number of reference electrodes. The reference electrode  132  may be common to two or more of the working electrodes  130 . In some embodiments, one or more working electrodes may be located to a first side (e.g., the left side as shown in  FIG. 4 ) and one or more electrodes may be located to a second side (e.g., the right side as shown in  FIG. 4 ) of the reference electrode  132 . 
     In some embodiments, the working electrodes  130  include a first working electrode (e.g., working electrode  130 C) and a second working electrode (e.g., working electrode  130 G), wherein the first working electrode faces the second working electrode. In some embodiments, the working electrodes  130  include a first working electrode (e.g., working electrode  130 C) and a second working electrode (e.g., working electrode  130 G), wherein the first working electrode faces the second working electrode, and wherein the first working electrode and the second working electrode are located on opposite sides of the flow channel  406 . 
     In some embodiments, two or more working electrodes  130  are arranged along a length of the flow channel  406 . In some embodiments, at least some of the working electrodes  130  constitute a first array of working electrodes (e.g., working electrodes  130 C and  130 D) arranged along a length of the flow channel  406 . A second array of working electrodes (e.g., working electrodes  130 G and  130 H) is arranged along a length of the flow channel  406 , wherein the first array of working electrodes faces the second array of working electrodes. 
     According to another aspect, a method of testing a test liquid  353  according to embodiments will now be described with reference to  FIG. 5 . The method  500  of testing a test liquid  353  includes, in  502 , providing a flow channel (e.g., flow channel  406 ), one or more reference electrodes (e.g., reference electrode  132 ) located in the flow channel, and two or more working electrodes (e.g., working electrodes  130 ) located in the flow channel, wherein a total number of working electrodes is greater than a total number of reference electrodes. The method  500  further includes, in  504 , flowing a test liquid (e.g., test liquid  353 ) through the flow channel. The method  500  further includes, in  506 , measuring one or more voltage potentials between the one or more reference electrodes and the two or more working electrodes. 
     Following testing, the test liquid  353  is removed and a wash liquid (e.g., wash liquid  375 ) can be introduced to the inlet (e.g., inlet  410 ) to minimize traces of the test liquid  353  therein. Following the test and washing operations, another test of another test liquid, such as from another patient specimen can be conducted. Many tests can be conducted, such as 40 or more tests of different test liquids before the sensor assembly  100  is replaced with a new sensor assembly. In some embodiments, a calibrator liquid can be received in the first primary inlet  110 A, such as before and after a series of tests. 
     According to another aspect, a method  600  of testing a test liquid  353  according to embodiments will now be described with reference to  FIG. 6 . The method  600  of testing a test liquid  353  includes, in  602 , providing a primary body (e.g., primary body  102 ) having a primary channel (e.g., first primary channel  106 A and/or second primary channel  106 B), a secondary body (e.g., secondary body  104 ) having a secondary channel (e.g., secondary channel  108 ), the primary channel and the secondary channel being located on different planes, a primary inlet (e.g., first primary inlet  110 A) coupled to a first end (e.g., first end  111 A) of the primary channel, a primary outlet (e.g., first primary outlet  110 B) coupled between a secondary channel inlet (e.g., secondary channel inlet  112 A) and a second end (e.g., second end  111 B) of the primary channel, a reference electrode (e.g., reference electrode  132 ) of one or more potentiometric sensors located in the secondary channel and one or more working electrodes (e.g., working electrodes  130 A- 130 H) of the one or more potentiometric sensors located in the primary channel. 
     The method  600  further includes, in  604 , flowing a test liquid (e.g., test liquid  353 ) through the primary channel and the secondary channel. The method  600  further includes, in  606 , measuring one or more voltage potentials between the reference electrode and the one or more working electrodes. 
     Additional Embodiments 
     In one or more additional apparatus embodiments, the primary body  102  may include a single primary channel, such as solely the first primary channel  106 A. The single primary channel may be coupled to a secondary channel  108 . In such an embodiment, the secondary channel outlet  112 B may be the outlet of the sensor assembly  100 . Accordingly, the secondary channel outlet  112 B may be coupled to the waste receptacle  358 . 
     In one or more additional apparatus embodiments, the sensor assembly  100  and/or the sensor assembly  400  may include one or more reference electrodes  132 , wherein a number of working electrodes  130  is greater than a number of reference electrodes. In one or more additional apparatus embodiments, one or more working electrodes  130  may be located in the secondary channel  108 . In some embodiments, one or more additional reference electrodes  132 ′ could be provided in the flow channel  406 , provided that a total number of reference electrodes  132 ,  132 ′ are less than a total number of working electrodes  130 . 
     While embodiments of this disclosure have been disclosed in example forms, many modifications, additions, and deletions can be made therein without departing from the scope of this disclosure, as set forth in the claims and their equivalents.