Electrochemical sensing well

A well is formed in a body of dielectric material and has a chamfered edge about a top side of the well. A top electrode layer is on a top face of the body and on the chamfered edge of the well. A bottom electrode is on a floor of the well.

BACKGROUND

Electrochemical analysis is sometimes used to identify particular chemical species in a liquid analyte having a fixed concentration of a particular chemical species and/or a fixed volume, which may be in the milliliter range. The field of electrochemical analysis may be advanced by a lower-cost sensing system that facilitates more efficient analysis utilizing, for instance, reduced analyte size and/or reagent consumption.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1is a sectional view illustrating an example electrochemical sensing cell20. Cell20is configured to contain an individual analyte undergoing electrochemical analysis. Although illustrated as a single cell, cell20may be incorporated as part of a larger array of cells20. As will be described hereafter, cell20facilitates a high precision high-volume manufacture of an array of such cells20into which analytes of chemicals in liquid or biological fluids may be easily introduced. Cell20further facilitates new methods of chemical sensing, smaller form factors, lower chemical consumption for analysis and lower cost for a given capability.

Cell20comprises substrate22, bottom electrode24, body28, well30and top electrode32. Substrate22comprises a base, platform, panel, plate or other foundational structure upon which a remainder of cell20is supported. Substrate22comprises at least one layer of dielectric material. In one implementation, substrate22comprises one or more layers of flexible dielectric materials provided from a roll, facilitating a roll-to-roll manufacturing or fabrication process. In one implementation, substrate22may comprise a layer of one or more polymers. In other implementations, substrate22may be formed from other materials and may have other configurations. In some implementations, substrate22may be omitted.

Bottom electrode24comprises an electrically conductive structure in electrical connection with a bottom or floor of well30so as to apply an electrical charge to a liquid analyte contained within well30. In the example illustrated, bottom electrode24comprises bottom electrode portion36and well electrode portion38. Bottom electrode portion36comprises a layer of electrically conductive material, such as a metal or indium tin oxide, formed upon and supported by substrate22. In one implementation, bottom electrode portion36comprises one or more electrically conductive traces. In another implementation, bottom electrode portion36comprises a sheet or panel of electrically conductive material.

Well electrode portion38comprises that portion of electrode24serving as an electrical contact to the liquid analyte within well30. In one implementation, well electrode portion38is formed concurrently with the formation of top electrode32. In some implementations, well electrode portion38may be omitted, wherein portions of bottom electrode portion36serve as an electrical contact for a liquid analyte within well30.

Body28comprises a mass of dielectric material adjacent bottom electrode36. Body28provides a volume of dielectric material in which well30is formed. Body28further supports top electrode32. In one implementation, body28is formed from a dielectric embossable material such as an embossing resin. In other implementations, body28may be formed from other materials.

Well30comprises a hole, bore, depression, open topped receptacle or open topped reservoir extending into body28from a topside40towards a bottom side42of body28. In one implementation, well30is one of an array of such wells formed in body28. In one implementation, well30has a microscopic scale volume (having a height and/or breadth of 50 μm or less), reducing analyte size and reagent consumption. In another implementation, well30may have a macroscopic scale volume.

Well30comprises a floor44, vertical sidewalls46and chamfer48. Floor44extends along a bottom of well30. In one implementation, the entirety of floor44is provided by electrode24. In another implementation, portions of floor44are provided by electrode24.

Sidewalls46extend upward from floor44substantially perpendicular to floor44, bottom electrode24and substrate22. In one implementation, sidewalls46have a circular cross sectional shape. In another implementation, sidewalls46have an elliptical cross sectional shape, a polygonal cross sectional shape or another cross sectional shape. For example, in other implementations, in lieu of comprising a cylinder, each of wells30may comprise a hexagon, a square, a rectangle, a triangle or any other shape forming an open topped volume for containing a liquid analyte or sample. The surfaces of sidewall46are formed or provided by the dielectric material of body28. As a result, the dielectric surface of sidewall46electrically separate bottom electrode24from top electrode32.

Chamfer48comprises a surface about a perimeter of well30that extends oblique to both sidewalls46and top surface50of body28. Chamfer48comprises a sloped surface extending between sidewall46and top surface50. Chamfer48forms a portion of the interior of well30at a top of well30. Chamfer48provides a surface that at least partially faces in an upward direction such that top electrode32may be formed by directional deposition in a direction perpendicular to floor44and top surface50, wherein the directionally deposited top electrode32is formed on chamfer48so as to be able to contact the liquid analyte within well30and is not formed on sidewalls46providing electrical isolation of bottom electrode24and top electrode32.

In one implementation, chamfer48extends at a 45° angle with respect to sidewalls46and top surface50of body28. In another implementation, chamfer48may extend at other angles oblique to sidewall46. In the example illustrated in which well30comprises a cylindrical bore, chamfer48has a circular cross sectional shape. In other implementations in which well30comprises a polygonal cross sectional shape or elliptical cross sectional shape, chamfer48may have other corresponding cross-sectional shapes.

Top electrode32comprise a layer of electrically conductive material formed on top surface50of body28and on chamfer48of well30. In one implementation, top electrode32comprise a metal layer. In another implementation, top electrode32comprise a layer of indium tin oxide or other electrically conductive material. In one implementation, top electrode32comprises a continuous sheet on top surface50of body28and chamfer48. In another implementation, top electrode32may comprise a patterned layer of electrically conductive material on top surface50so as to form one or more electric conductive traces. In one implementation, top electrode32is formed by directional deposition such as sputtering or evaporation. Top electrode32and bottom electrode24are configured so as to be connectable to a voltage source and an analytical device, facilitating the establishment of an electrical potential across or between electrodes24,32and facilitating electrochemical analysis, such as through the analysis of impedance of the liquid analyte within well30.

FIG. 2is a flow diagram of an example method100for forming electrochemical sensing cell20. As indicated by step102, well30having chamfer48is formed in body28. As described hereafter, various methods for forming well30with chamfer48and body28may be utilized. In one implementation, well30may be formed by embossing. In another implementation, well30may be formed by photo imaging or other material removal techniques. In one implementation, sidewalls46and chamfer48are formed concurrently. In another implementation, sidewalls46and chamfer48are formed in distinct steps.

As indicated by step104, electrode32is formed by directionally depositing an electrically conductive material, such as a metal or indium tin oxide, on the top surface50of body28and on chamfer48of well30. In one implementation, electrode32is formed by directional deposition such as sputtering or evaporation. The electrically conductive material forming electrode32is deposited in a direction perpendicular to top surface50of body28and parallel to sidewalls46of well30such that electrically conductive material is not deposited upon sidewalls46. As a result, sidewalls46electrically separate or isolate bottom electrode24from top electrode32.

As indicated by step106, the second or bottom electrode24is formed. In one implementation, bottom electrode24is formed in a two-part process, wherein portion36is first formed upon substrate22and wherein well portion38is formed by electrically conductive material that is directionally deposited upon portion36at the same time that top electrode32is formed through the same directional deposition. In another implementation, well portion38may be omitted such as where top electrode32is formed through directional deposition such as sputtering or evaporation such that portion36provides the floor in electrical contact within the bottom of well30. In one implementation, portion36of electrode24is joined to body28prior to the formation of well30. In another implementation, portion36of electrode24is joined to body28after the formation of well30.

FIGS. 3A-3Dillustrate method200, an example implementation of method100, for forming cell20ofFIG. 1.FIGS. 3A-3Dillustrate formation of cell20comprising the step of embossing. As shown byFIG. 3A, bottom electrode portion36is formed upon substrate22. In one implementation, substrate22is flexible and is provided from a roll. In one implementation, electrode portion36is also flexible and provided from a roll, wherein electrode portion36is laminated or otherwise joined to substrate22. In yet another implementation, electrode portion36may be formed by spraying or coating electrically conductive material onto substrate22. In some implementations, electrode portion36may be patterned using masks, photolithography or the like to form discrete portions or conductive traces on substrate22.

As shown byFIG. 3B, a volume or mass of embossable dielectric material providing body28, such as an embossable resin, is formed on electrode portion36, in contact with electrode portion36. As shown byFIG. 3C, while body28is in an embossable state, an embossing tool60embosses body28. Embossing tool60has an outer profile corresponding to the inner profile of well30. In particular, tool60comprises a well forming projection61having a lower outer profile62shaped to form sidewalls46and an upper outer profile shaped to form chamfer48. In one implementation, embossing tool60penetrates body28to a depth so as to contact and subsequently expose electrode portion36upon removal of embossing tool60. In other implementations, material removal techniques may be employed to remove portions of body28at the bottom of the well30that cover electrode portion36.

As shown byFIG. 3D, after embossing, body28is cured or otherwise solidified and embossing tool60is removed, leaving the formed well30. In one implementation, such curing is achieved using ultraviolet light. In other implementations, depending upon the material forming body28, body28may be cured or otherwise solidified in other fashions.

As further shown byFIG. 3D, electrically conductive material is directionally deposited in a direction parallel to sidewalls46of well30and upon electrode portion36, upon top surface50of body28and upon chamfer48of well30. Such directional deposition may be achieved using sputtering, evaporation or other directional deposition techniques. Because directional deposition is used, the electric conductive material becomes deposited upon electrode portion36as part of bottom electrode24and becomes deposited upon top surface50and chamfer48as part of top electrode32. Top electrode32extends into well30by means of chamfer48, but does not extend onto sidewalls46such that sidewalls46electrically isolate top electrode32from bottom electrode24.

AlthoughFIGS. 3A-3Dillustrate the formation of an individual cell20, method200may concurrently form an array of cells including cell20. When forming such an array of cells20, the steps shown in suchFIGS. 3A-3Dare substantially the same except that embossing tool60comprises an array of embossing projections corresponding to the array of wells30to be formed. The array of embossing projections concurrently or simultaneously emboss body28to form the array of wells, wherein the directional deposition step shown inFIG. 3Dsimultaneously or concurrently deposits electrically conductive material such that top electrode32extends into each of the wells30along each of the chamfers48of the wells30. Overall, method200facilitates high precision and high-volume manufacture of an electrochemical sensing array of cells20into which chemicals in liquid or biological fluids may be easily introduced.

FIGS. 4A and 4Billustrate method300, another example implementation of method100for forming electrochemical sensing cell20ofFIG. 1, which may be part of a larger array of cells that are concurrently formed with the formation of the illustrated cell20. As shown byFIG. 4A, well30is formed in body28prior to body28being joined to electrode portion36or substrate22. In one implementation, well30is formed by embossing, wherein the lower supporting substrate is separated from body28upon completion of embossing. In another implementation, well30may be formed by photolithography, drilling, etching or other material removal techniques.

As shown byFIG. 4B, after the formation of well30and body28, substrate22and electrode portion36of bottom electrode24are joined to body28. As further shown byFIG. 4B, electrically conductive material is directionally deposited upon electrode portion36, upon top surface50of body28and upon chamfer48of well30in a direction parallel to sidewalls46of well30. Such directional deposition may be achieved using sputtering, evaporation or other directional deposition techniques. Because directional deposition is used, the electrically conductive material becomes deposited upon electrode portion36as part of bottom electrode24and becomes deposited upon top surface50and chamfer48as part of top electrode32. Top electrode32extends into well30by means of chamfer48, but does not extend onto sidewalls46such that sidewalls46electrically isolate top electrode32from bottom electrode24.

FIGS. 5A and 5Billustrate method400, another example implementation of method100for forming electrochemical sensing cell20ofFIG. 1, which may be part of a larger array of cells that are concurrently formed with the formation of the illustrated cell20. As shown byFIG. 5A, well30is formed in body28prior to body28being joined to electrode portion36or substrate22. Well30is formed in a two-step process. As shown byFIG. 5A, sidewalls46of well30are formed in body28prior to the formation of chamfers28. In one implementation, sidewalls46are formed by embossing, drilling or other material removal techniques. In yet another implementation, sidewalls46may be formed by patterned material buildup of body28so as to form sidewalls46.

As shown byFIG. 5B, chamfer48is subsequently formed in body28along an upper edge of sidewalls46near the top surface50of body28. Chamfer48is formed using one or more material removal techniques such as etching, drilling, photolithography and the like. Body28is further joined to substrate22and electrode portion36of bottom electrode24. After the formation of chamfer48, electrically conductive material is directionally deposited upon electrode portion36, upon top surface50of body28and upon chamfer48of well30in a direction parallel to sidewalls46of well30. Such directional deposition may be achieved using sputtering, evaporation or other directional deposition techniques. Because directional deposition is used, the electric conductive material becomes deposited upon electrode portion36as part of bottom electrode24and becomes deposited upon top surface50and chamfer48as part of top electrode32. Top electrode32extends into well30by means of chamfer48, but does not extend onto sidewalls46such a sidewalls46electrically isolate top electrode32from bottom electrode24.

FIG. 6illustrates use of electrochemical sensing cell20as part of the electrical chemical sensing system500. In addition to cell20, system500comprises voltage source502and controller504. Voltage source502comprise a source of electrical voltage connected to electrode24and32so as to apply an electric field to or through the analyte sample within well30. In one implementation, one of electrodes24,32may be electrically connected to ground while charge is applied to the other of electrodes24,32. In another implementation, different electrical charge may be applied to electrodes24,32.

Controller504comprises one or more processing units configured to control the application of particular electric fields between electrodes24,32designed to detect particular chemical species in the analyte sample (a particular buffered solution containing a chemical species) by controlling output of voltage source502. Controller504is further configured to sense or detect impedance or other electrical characteristics to analyze the analyte sample within well30. For example, controller504may determine or detect particular chemical species in an analyte sample based upon a detected electrical impedance of the analyte sample.

For purposes of this application, the term “processing unit” shall mean a presently developed or future developed processing unit that executes sequences of instructions contained in a non-transitory memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals. The instructions may be loaded in a random access memory (RAM) for execution by the processing unit from a read only memory (ROM), a mass storage device, or some other persistent storage. In other embodiments, hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. For example, controller504may be embodied as part of one or more application-specific integrated circuits (ASICs). Unless otherwise specifically noted, the controller is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit.

FIG. 7is a flow diagram of an example method600that may be carried out by electrochemical sensing system500shown inFIG. 6. As indicated by step610, the fluidic analyte sample is deposited in well30such that the analyte sample is in contact with both bottom electrode24and top electrode32along chamfer48of well30. As indicated by step612, controller504, following instructions contained in a non-transitory memory, generates control signals causing voltage source502to apply charge or electric potential to at least one of electrodes24,32to establish an electric field across the analyte sample within well30. As indicated by step614, controller504utilizes impedance signals and one or more electrochemical analytic techniques, such as electrochemical impedance spectroscopy, to sense or detect minute concentrations of chemical and/or biochemical species within the analyte sample. The detected chemical and/or biochemical species is an output via a display, print out or other output mechanism.

FIGS. 8 and 9illustrate an example array618of electrochemical sensing cells20.FIG. 9is a sectional view of the array618of electrochemical sensing cells20. Array618may be formed by any of methods100,200,300and400described above. In one implementation, each of wells30of the cells20are concurrently formed, facilitating high-volume high precision manufacture of array618. In other implementations, portions of array618may be formed at different times.

FIGS. 10 and 11illustrate portions of an array718of electrochemical sensing cells720. Each of cells720is similar to cell20described above except that each of cells720additionally comprises a fluidic channel760. Fluidic channel760comprises a fluid passage extending through body28and opening into an interior of well30. In the example illustrated, fluidic channel760is open along the top face of body28and open through top electrode32. Fluidic channel760extends from the top face50of body28into body28. In one implementation, fluidic channel760extends to electrode portion36. In another implementation, fluidic channel760extends to substrate22. In yet another implementation, fluidic channel760terminates so as to have a floor within body28, spaced from electrode portion36. In one implementation, the floor of fluidic channel760has deposited thereon electric conductive material from the directional deposition of top electrode32.

Fluidic channel760facilitates filling and emptying of well30with the analyte sample. Fluidic channel760may further facilitate mixing of the analyte sample within well30. Although illustrated as having straight or linear paths, fluidic channel760may alternatively be serpentine or of other path shapes. Although illustrated as having substantially vertical sidewalls, fluidic channel76may alternatively have angled or rounded sidewalls. Although fluidic channels760of the two illustrated cells720are illustrated as extending parallel to one another, in other implementations, fluidic channels760may have other paths to the respective wells30.

FIGS. 12A and 12Billustrate an example method800for forming one of cells720by embossing. Similar to the embossment of cell20according to method200shown inFIGS. 3A and 3B, an embossable mass of material, such as an embossing resin, is formed upon electrode portion36and substrate22to form body28. As shown byFIGS. 12A and 12B, well30and fluidic channel760are concurrently formed by embossing tool860. Embossing tool860is similar to embossing tool60(shown inFIG. 3C) except that embossing tool860comprise an additional fluid channel forming extension portion862. Upon insertion into the mass of embossment material forming body28, fluid channel forming extension portion862embosses fluid channel760(shown inFIGS. 10 and 11). The remaining formation of cell720is similar to the steps shown inFIG. 3Dabove with respect to method200. In particular, body28is cured or otherwise solidified, embossing tool860is removed and electrically conductive material is directionally deposited in a direction parallel to sidewalls46of well30to form electrode portion38in the bottom of well30and top electrode32extending on top surface50and chamfer48of well30. AlthoughFIGS. 12A and 12Billustrate the formation of a single one of cells720, multiple cells720of array718may be concurrently formed using an embossing tool860which includes multiple projections and multiple portions862that are concurrently embossed into body28.

FIG. 13is a top perspective view of electrochemical sensing cell920, another example implementation of electrochemical sensing cell20. Electrochemical sensing cell920is similar to electrochemical sensing cell720except that electrode chemical sensing cell920comprises fluidic channel960in lieu of fluidic channel760. Like fluidic channel760, fluidic channel960comprises a fluid passage extending through body28and opening into an interior of well30. In the example illustrated, fluidic channel760is surrounded but for an outer axial opening and an inner axial opening adjacent the interior of well30. In the example illustrated, fluidic channel960is surrounded on three sides by body28and has a floor provided by electrode portion36. In another implementation, channel960may have a floor provided by substrate22. In other implementations, channel960may have the floor provided by body28. Although illustrated as being linear and having a rectangular or square cross sectional shape, in other implementations, channel960may extend along other non-linear paths and have other cross-sectional shapes.

Fluidic channel960facilitates filling and emptying of well30with the analyte sample. Fluidic channel960may further facilitate mixing of the analyte sample within well30.

FIGS. 14A-14Dillustrate an example method1000for forming one of cells920by embossing. As shown byFIG. 14A, bottom electrode portion36is formed upon substrate22. In addition, a sacrificial core1002is formed upon the platform provided by bottom electrode portion36and substrate22. In one implementation, sacrificial core1002is formed directly upon a top of electrode portion36. In another implementation, sacrificial core1002may alternatively be formed directly upon a top of substrate22, wherein electrode portion36is patterned around sacrificial core1002. Sacrificial core1002has a negative shape corresponding to a shape of fluidic channel960. Sacrificial core1002comprise a material that may be sacrificed or removed once body28has been solidified or cured to leave fluidic channel960. In one implementation, sacrificial core1002comprises a material configured to be converted to a fluid state (liquid or gas) for removal. In another implementation, sacrificial core1002comprise a material configured to be etched, broken or shattered to facilitate such removal. In one implementation, the sacrificial core1002comprises a wax material that remains in a solid-state as the embossment material is formed or molded about sacrificial core1002, wherein the wax composition forming the sacrificial core1002may subsequently be melted without melting, deforming or damaging the solidified or cured embossment material forming fluidic channel960.

As shown byFIG. 14B, a volume or mass of embossable dielectric material providing body28, such as an embossable resin, is formed on electrode portion36, in contact with electrode portion36and about sacrificial core1002. As shown byFIG. 14C, while body28is in an embossable state, an embossing tool60embosses body28adjacent to the sacrificial core1002such that the sacrificial core1002is exposed to the embossing tool60. As a result, upon removal of embossing tool60, sacrificial core1002is exposed to the interior of the formed well30.

Embossing tool60has an outer profile corresponding to the inner profile of well30. In particular, tool60has a lower outer profile62shaped to form sidewalls46and an upper outer profile before shaped to form chamfer48. In one implementation, embossing tool60penetrates body28to a depth so as to contact and subsequently expose electrode portion36upon removal of embossing tool60. In other implementations, material removal techniques may be employed to remove portions of body28at the bottom of the well30that cover electrode portion36.

As shown byFIG. 14D, after embossing, body28is cured or otherwise solidified and embossing tool60is removed, leaving the formed well30. In one implementation, such curing is achieved using ultraviolet light. In other implementations, depending upon the material forming body28, body28may be cured or otherwise solidified in other fashions. Sacrificial core1002is exposed in the interior of well30. In another implementation, sacrificial core1002may be sacrificed or removed prior to the removal of embossing tool60.

As further shown byFIG. 14D, sacrificial core1002is sacrificed or removed, leaving fluidic channel960. As noted above, in one implementation, sacrificial core1002is converted to a fluid state, or the fluid flows or is drawn from body28. In another implementation, sacrificial core1002is etched away, broken or shattered to facilitate removal, leaving fluidic channel960.

Prior to or following the sacrifice or removal of sacrificial core1002, electrically conductive material is directionally deposited upon electrode portion36, upon top surface50of body28and upon chamfer48of well30in a direction parallel to sidewalls46of well30. Such directional deposition may be achieved using sputtering, evaporation or other directional deposition techniques. Because directional deposition is used, the electric conductive material becomes deposited upon electrode portion36as part of bottom electrode24and becomes deposited upon top surface50and chamfer48as part of top electrode32. Top electrode32extends into well30by means of chamfer48, but does not extend onto sidewalls46such a sidewalls46electrically isolate top electrode32from bottom electrode24.

AlthoughFIGS. 14A-14Dillustrate the formation of an individual cell920, method200may concurrently form an array of cells including cell20. When forming such an array of cells920, the steps shown in suchFIGS. 14A-14Dare substantially the same except that embossing tool60comprises an array of embossing projections corresponding to the array of wells30to be formed and that a plurality of sacrificial cores1002corresponding to the array of embossing projections and the array of wells30are formed upon the platform provided by substrate22and electrode portion36. The array of embossing projections concurrently or simultaneously emboss body28to form the array of wells, wherein the directional deposition step shown inFIG. 14Dsimultaneously or concurrently deposits electrically conductive material such that top electrode32extends into each of the wells30along each of the chamfers48of the wells30. Overall, method1000facilitates high precision high-volume manufacture of an electrochemical sensing array of cells920into which chemicals in liquid or biological fluids may be easily introduced through fluidic channel960.

FIGS. 15-18illustrate array1118of electrochemical sensing cells1120, another example implementation of electrochemical sensing cell20. Array1118is similar to array718(shown and described above with respect toFIGS. 10 and 11) except that array1118comprises electrochemical sensing cells1120A and1120B (collectively referred to as sensing cells1120). Sensing cells1120A and1120B are similar to sensing cells720and920, respectively, except that sensing cells1120each additionally comprise isolation walls1170. Those remaining components of cells1120A and1120B which correspond to cells720and920, respectively, are numbered similarly.

Isolation walls1170comprise walls extending outwardly from vertical walls46of wells30, partitioning the otherwise continuous chamfer48of each well30into two or more separate chamfer portions, wherein the portions are spaced from one another by isolation walls1170. Each of isolation walls1170comprises an electrical isolation surface continuously extending outwardly from sidewalls46of wells30and oriented so as to not receive the electrically conductive material during the directional deposition of top electrode32. As a result, the electrical isolation surface electrically isolates electrical charge conducted to different portions of the same chamfer48about the same well30, but for the conduction of electrical charge across any analyte sample within well30from one chamfer portion to another chamfer portion. Isolation walls1170facilitate the formation of multiple electrically distinct top electrodes32connected to a single well30.

FIGS. 15-18illustrate an example wherein each isolation wall1170has one or more isolation surfaces1172that extend parallel to sidewalls46, wherein the isolation surfaces1172are located on an end of wall1170contiguous with sidewalls46and on one side of each wall1170or on both sides of each wall1170. In the example illustrated, each isolation wall1170has two end vertical isolation surfaces1172and two opposite side vertical isolation surfaces1170perpendicular to top surface50that do not receive the electrically conductive material that is directionally deposited (in a direction parallel to sidewalls46) during the formation of top electrode32. As a result, as shown byFIGS. 15-17, each isolation wall1170further comprises a top surface1174upon which is deposited layer electrically conductive layer1176from the directional deposition of top electrode32. However, the isolation surfaces1172electrically isolate the electrically conductive layer1174formed from the directionally deposited electrically conductive material on top surface50of body28forming top electrode32.

As further shown byFIGS. 15-18, fluidic channel760in combination with isolation walls1170provide cell1120A with three distinct, electrically isolated top electrodes1132A,1132B and1132C, each of which may have a distinct electrical charge. Isolation walls1170electrically isolate one side of chamfer48of well30from the other side chamfer48of well30to electrically separate electrode1132A from electrode1132B and electrode1132C. Fluidic channel760extends into body28through chamfer48and includes electrical isolation surface1173. Similar to electrical isolation surfaces1172, surface or surfaces1173extend parallel to sidewalls46of well30such that the directionally deposited (in a direction parallel to sidewalls46) electrically conductive material forming top electrode1132B and1132C is not deposited upon surfaces1173. As a result, surfaces1173further partition chamfer48into electrically distinct regions upon which electrically distinct electrodes1132B and1132C are formed. As noted above, fluidic channel760further facilitates filling, emptying or mixing of an analyte sample within the associated well30. In other implementations, fluidic channel760may be shallower or may not be used to move analyte into and/or out of well30, but may be merely provided for further electrically partitioning chamfer48to provide additional electrically distinct electrodes for the particular well30.

As shown byFIG. 15, isolation walls1170further partition well30of cell1120B into two distinct top electrodes1132A and1132D. Because cell1120B includes fluidic channel920which does not electrically partition chamfer48of cell1120B, analyte may be supplied to, withdrawn from or mixed within well30of cell1120B, while providing1120B with two, rather than three top electrodes. In other implementations, one or both of fluidic channels720,920may be omitted.

FIGS. 19A-19Eillustrate an example method1200for forming cell1120A of array1118. Method1200may be utilized to concurrently form cell1120B with the cell1120A, where cell1120B is formed by concurrently forming the same embossable material forming body28about cell1120A about sacrificial core1002and subsequently sacrificing sacrificial core1002as described above with respect toFIGS. 14C and 14D. In other implementations, array1118may include an array of just cells1120A or an array of just cells1120B.

As shown byFIGS. 19A-19C, well30, fluidic channel760and isolation walls1170are concurrently formed by embossing tool1160.FIG. 19Ais a bottom view of embossing tool1160.FIGS. 19B-19Dillustrate the bottom of embossing tool1160pressed into or embossing body28while body28is in an embossable state. Embossing tool1160is similar to embossing tool860(shown inFIGS. 12A and 12C) except that, in addition to comprising extension862projecting from a bottom of embossing tool1160and from the well forming portion61, embossing tool1160comprises additional channels1164extending into a bottom surface of embossing tool1160for forming isolation walls1170. Upon the depressment into the mass of embossment material forming body28, fluid channel forming extension portion862embosses fluid channel760(shown inFIG. 15). Channels1164are filled with the embossable material of body28to form isolation walls1170.

The remaining formation steps for forming cell1120A is similar to the steps shown inFIG. 3Dabove with respect to method200and shown inFIG. 19E. In particular, body28is cured or otherwise solidified, embossing tool1160is removed and electrically conductive material is directionally deposited in a direction parallel to sidewalls46of well30to form electrode portion38in the bottom of well30and top electrodes1132A-1132C extending on top surface50and chamfer48of well30of cell1120A. AlthoughFIGS. 12A and 12Billustrate the formation of a single one of wells720, multiple wells1120A (or1120B) of array1118may be concurrently formed using an embossing tool1160which includes multiple well forming projections61, multiple fluidic channel forming portions862and multiple isolation walls forming portions or channels1164that are concurrently embossed into body28.

FIGS. 20 and 21illustrate electrochemical sensing cell1220, another example implementation of electrochemical sensing cell20. Electrochemical sensing cell1220is similar to electrochemical sensing cell20except that cell1220additionally comprises isolation channels1260. Those remaining components of cell1220which correspond to components of cell20are numbered similarly.

Isolation channels1260comprise grooves or channels extending outwardly from vertical walls46of wells30, partitioning the otherwise continuous chamfer48of well30into two or more separate chamfer portions, wherein the chamfer portions are spaced from one another by isolation channels1260. Each of isolation channels1260comprises an electrical isolation surface continuously extending outwardly from sidewalls46of wells30so as to not receive the electrically conductive material during the directional deposition of top electrode32. As a result, the electrical isolation surface electrically isolates electrical charge conducted to different portions of the same chamfer48about the same well30, but for the conduction of electrical charge across any analyte sample within well30from one chamfer portion to another chamfer portion. Isolation channels1260facilitate the formation of multiple electrically distinct top electrodes32connected to a single well30.

FIGS. 20 and 21illustrate an example wherein each isolation channel1260has one or more isolation surfaces1273that extend parallel to sidewalls46, wherein the isolation surfaces1273are located on one side of each channel1260or on both sides of each channel1260. In the example illustrated, each isolation channel1260has two opposite side vertical isolation surfaces1273perpendicular to top surface50that do not receive the electrically conductive material that is directionally deposited (in a direction parallel to sidewalls46) during the formation of top electrode32. As a result, as shown byFIG. 21, each isolation channel1260further comprises a floor1274upon which is deposited layer electrically conductive layer1276from the directional deposition of top electrode32. However, the isolation surfaces1273electrically isolate the electrically conductive layer1274formed from the directionally deposited electrically conductive material on top surface50of body28forming top electrodes1232A and1232B. Each of isolation channels1260may be formed utilizing the method illustrated inFIGS. 12A and 12Band utilizing an embossing tool similar to embossing tool860but including an additional oppositely extending extension862.

FIGS. 22 and 23illustrate electrochemical sensing cell1320, another example implementation of electrochemical sensing cell20. Electrochemical sensing cell1320is similar to electrochemical sensing cell1220except that cell1320comprises channels1360and chamfer1348in place of channels1260and chamfer48, respectively. Those remaining components of cell1320which correspond to components of cell1220are numbered similarly.

Channels1360are similar to channels1260except that channel1360terminate at chamfer1348of well30. As with channels1260, channels1360comprise isolation surfaces1273which extend parallel to sidewalls46and which do not receive electrically conductive material during directional deposition of the electrically conductive material. Chamfer1348is similar to chamfer48except that chamfer1348is provided at the ends of channels1360. In contrast to chamfer48which is located at a top of well30between sidewalls46of well30and top surface50of body28, chamfer1348is located between sidewalls46of well30and floor1274of each of channels1360. During directional deposition of electrically conductive electrode material, the electrically conductive material is deposited upon chamfer1348as well of floor1274of channels1360to form top electrodes, a first top electrode1332A extending along one of channels1360and a second top electrode1332B extending along the other of channels1360. Isolation surfaces1273serve to electrically isolate electrodes1332A and1332B from one another. During use, well30is filled with the liquid analyte sample to a level above a lower end of chamfer1348, wherein distinct electrical fields may be applied to the analyte sample within well30using either of electrodes1332A,1332B. Chamfer1348may be formed by embossing or any of the aforementioned methods.

Each of isolation walls1170and isolation channels1260(as well as fluidic channel760in cell1120A) have isolation surfaces that are parallel to sidewalls46such that the electrically conductive material directionally deposited to form the top electrode(s) is not deposited upon such isolation surfaces.FIGS. 22 and 23illustrate alternative isolation surfaces wherein such isolation surfaces are not parallel to sidewalls46of well30, but extend below notches or undercuts such that directionally deposited electrically conductive material does not form thereon such that electrical isolation is achieved to electrically partition chamfer48and electrically conductive material on top50of body28into multiple electrodes.

FIG. 24illustrates isolation wall1370having isolation surface1373formed in a notch or cut out1375. In one implementation, the notch or cut out1375may continuously extend about end of wall1370adjacent well30. In another implementation, wall1370may have surface that is parallel to sidewalls46. During directional deposition of the top electrode(s), electrically conductive material is not deposited upon isolation surface1373.

FIG. 25illustrates isolation channel1460. Isolation channel1460similar to isolation channel1260except that isolation channel1460has isolation surface1473formed in a cut outer notch1475. During directional deposition of the top electrode(s), electrically conductive material is not deposited upon isolation surface1473. Using one or both of isolation walls1374of isolation channels1460, an electrochemical sensing cell may be electrically partitioned to provide a plurality of electrodes for a single well30. Although not illustrated, each of the aforementioned electrochemical sensing cells is employed as part of electrochemical sensing system comprising voltage source502and controller504shown and described above with respect toFIG. 6for carrying out the method600shown and described with respect toFIG. 7.