Back side electrode

Abstract

A device includes a monitor. The monitor includes at least one sensor configured to sense an electrical signal indicative of an analyte level of an analyte of a patient. The sensor includes a sensor flex extending from a first axial end to a second axial end. The sensor flex defines front side and a back side opposite the front side. A first electrode is disposed on the front side of the sensor flex and a second electrode is disposed on the back side of the sensor flex. The first electrode and the second electrode form an electrode pair configured to react to the analyte and generate the electrical signal in response to the reaction. The second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

Description

Docket No.: A0011989W001 / 1277-126W001BACK SIDE ELECTRODE

[0001] This application is a PCT with provisional priority of U.S. Provisional Patent Application No. 63 / 762,323, filed 24 February 2025, the entire contents of which is incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure relates to biosensors.BACKGROUND

[0003] Biosensors are configured to detect and / or quantify the amount of an analyte in a patient's body, which enables patients and medical personnel to monitor physiological conditions within the patient's body. In some examples, in a patient with diabetes, it may be beneficial to monitor levels of one or more analytes on a continuing basis (e.g., glucose). Thus, glucose sensors have been developed for use in obtaining an indication of glucose levels in a diabetic patient. Such indications are useful in monitoring and / or adjusting a treatment regimen, which typically includes administration of insulin to the patient.

[0004] A patient can measure their analyte levels using a measurement device such as a test strip meter. In some examples, an analyte level in a patient may be monitored continuously. For example, a continuous glucose measurement system (or a continuous glucose monitor (CGM)) may be configured to monitor interstitial glucose. Some example continuous analyte monitoring systems include subcutaneous (or short-term) sensors and implantable (or long-term) sensors.SUMMARY

[0005] Aspects of the present disclosure are directed to medical devices for sensing an analyte in a patient. The device includes a sensor disposed on a sensor flex. The sensor flex may be inserted into a patient’s body to sense an analyte. The sensor flex extends from a first axial end to a second axial end, and the sensor flex also defines a front side and a back side opposite the front side. The sensor includes an electrode pair, and at least one electrode of the electrode pair is disposed on the back side of the sensor flex in a pattern. The pattern is such that the back side electrode does not include only a uniform layer covering all of the surface area on the back side of the sensor flex. For example, the back side electrode may cover less than all of the surface area on the back side of the sensor flex, or may define a non-uniform thickness, or both.

[0006] Patterning of a back side electrode may enable a number of desirable properties. For example, devices according to the present disclosure may enable configurability of the back sideDocket No.: A0011989W001 / 1277-126W001 of the sensor flex. Such configurability may enable better sensor performance by selective patterning of the shape, size, location, and thickness of the electrodes of the sensor on both the front side and the back side of the sensor flex. Furthermore, devices according to the present disclosure may enable a reduction in size of the sensor flex, or may enable inclusion of additional sensors configured to sense the same or a different analyte on the sensor flex, or both. For example, disclosed herein are devices which are configured to sense multiple analytes, which may enable better patient care outcomes.

[0007] In one example, a device includes a monitor. The monitor includes at least one sensor configured to sense an electrical signal indicative of an analyte level of an analyte of a patient. The sensor includes a sensor flex extending from a first axial end to a second axial end. The sensor flex defines front side and a back side opposite the front side. A first electrode is disposed on the front side of the sensor flex and a second electrode is disposed on the back side of the sensor flex. The first electrode and the second electrode form an electrode pair configured to react to the analyte and generate the electrical signal in response to the reaction. The second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

[0008] In one example, a technique for fabricating a sensor of a medical device includes fabricating a sensor flex extending from a first axial end to a second axial end, the sensor flex defining front side and a back side opposite the front side. The technique includes positioning a first electrode on the front side of the sensor flex and positioning a second electrode on the back side of the sensor flex. The second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

[0009] In one example, a technique includes reacting an electrode pair which includes a first electrode and a second electrode with an analyte of a patient. The electrode pair is part of a sensor. The sensor includes a sensor flex extending from a first axial end to a second axial end. The sensor flex defines a front side and a back side opposite the front side. The first electrode is disposed on the front side of the sensor flex and the second electrode is disposed on the back side of the sensor flex. The second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex. The technique includes generating an electrical signal indicative of an analyte level of the analyte between the first electrode and the second electrode in response to the reaction with the analyte. The technique also includes outputting, from the sensor, an electrical signal indicative of the analyte level of the analyte of the patient.Docket No.: A0011989W001 / 1277-126W001

[0010] In one example, a technique for manufacturing an analyte sensing apparatus includes depositing a back side electrode in a pattern on a substrate. The back side electrode has a first metal composition having an electroactive surface. The technique includes applying a base layer to the back side electrode. The base layer defines a first side facing away from the back side electrode and a second side adjacent to the back side electrode. The technique includes depositing a front side electrode on the first side of the base layer, the front side electrode has a second metal composition having an electroactive surface.

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a schematic diagram illustrating an example glucose level management system, in accordance with one or more examples described in this disclosure.

[0013] FIGS. 2A-2B are schematic diagram illustrating an example medical device including a monitor which includes a sensor which includes a sensor flex.

[0014] FIGS. 3 A-3B is a schematic diagram illustrating a conceptual side view of medical device from a front side in FIG. 3A and from a back side in FIG. 3B.

[0015] FIGS. 4A-4B is a schematic diagram illustrating a conceptual side view of a medical device from a front side in FIG. 4 A and from a back side in FIG. 4B.

[0016] FIGS. 5A-5B are schematic diagrams illustrating a conceptual side view of a medical device including a glucose monitor and insulin cannula from a front side in FIG. 5 A and from a back side in FIG. 5B, in accordance with one or more examples of the present disclosure.

[0017] FIG. 6 is a block diagram illustrating an example monitor, in accordance with one or more examples described in this disclosure.

[0018] FIG. 7 is a schematic diagram illustrating example sensors, and a voltage being applied to the sensors, in accordance with one or more examples of the present disclosure.

[0019] FIGS. 8A-8C are conceptual diagrams illustrating example sensor flex internals of a sensor flex of a medical device.

[0020] FIGS. 9A-9C are conceptual diagrams illustrating the sensor flex internals of a sensor flex of a medical device.

[0021] FIGS. 10-12 are conceptual diagrams illustrating a portion of different example sensor flex internals of a sensor flex of a sensor according to the present disclosure.

[0022] FIG. 13 is a flowchart illustrating an example technique for fabricating a medical device, in accordance with one or more examples of the present disclosure.Docket No.: A0011989W001 / 1277-126W001DETAILED DESCRIPTION

[0023] Aspects of the present disclosure are directed to medical devices for sensing an analyte in a patient. The device includes a sensor disposed on a sensor flex. The sensor flex may be inserted into a patient’s body to sense an analyte. The sensor flex extends from a first axial end to a second axial end, and the sensor flex also defines a front side and a back side opposite the front side. The sensor includes an electrode pair, and at least one electrode of the electrode pair is disposed on the back side of the sensor flex in a pattern. The pattern is such that the back side electrode does not include only a uniform layer covering all of the surface area on the back side of the sensor flex. For example, the back side electrode may cover less than all of the surface area on the back side of the sensor flex, or may define a non-uniform thickness, or both.

[0024] Patterning of a back side electrode may enable a number of desirable properties. For example, devices according to the present disclosure may enable configurability of the back side of the sensor flex. Such configurability may enable better sensor performance by selective tailoring of the shape, size, location, and thickness of the electrodes of the sensor on both the front side and the back side of the sensor flex. Furthermore, devices according to the present disclosure may enable a reduction in size of the sensor flex, or may enable inclusion of additional sensors configured to sense the same or a different analyte on the sensor flex, or both. For example, disclosed herein are devices which are configured to sense multiple analytes, which may enable better patient care outcomes.

[0025] In general, this disclosure describes devices and techniques for determining an analyte level in a patient using a monitor that includes a sensor that includes an electrode pair. The electrode pair includes a first electrode, called a working electrode, and a second electrode, called a counter electrode. At least one of first electrode and the second electrode (e.g., the electrode pair) reacts to the analyte and generates an electrical signal indicative of an analyte level of the analyte of the patient. The electrode pair is typically inserted into the targeted tissue (e.g., an interstitial fluid layer, a vein, or the like) by positioning the electrode pair on a sensor flex and inserting the sensor flex into the patient’s body.

[0026] The sensor including the working electrode and a counter electrode may be part of a monitor that continuously or intermittently senses the level (e.g., concentration in interstitial fluid) of an analyte. For example, the monitor may be a glucose monitor which regularly measures the concentration of glucose in a patient or upon request from the patient or other user and is worn by the patient for an extended period of time (e.g., hours or days) without being removed. Reducing the size of the monitor, especially those components of the monitor which are inserted into the patient’s body, may advantageously improve wearability of the monitorDocket No.: A0011989W001 / 1277-126W001 and / or improve patient comfort. Furthermore, it may be desirable to sense the level of more than one analyte. For example, in the example of a glucose monitor, it may be desirable to measure the levels of one or more analytes in addition to glucose, because information about the level of these additional relevant analytes may be used by the patient, clinician, or medical devices to selectively tailor treatment of the patient (e.g., used to adjust target levels, injections of insulin, or the like).

[0027] Certain analyte sensors may arrange the working electrode, the counter electrode, and optionally, one or more additional electrodes along a front side of the sensor flex. The additional electrodes may include a working electrode and a counter electrode of a second sensor (where the analyte sensor includes more than one sensor), or may include a reference electrode (where the sensor is configured as a three-wire sensor), or may include a background electrode (where a background electrode is included), or a combination of these additional sensors. As a result of positioning all of the electrodes on the same side of the sensor flex, it may be difficult to reduce the length and diameter of the sensor flex. Thus, such devices, which only include electrodes positioned on a front side of the sensor flex, may be uncomfortable to wear and / or may include fewer sensors to sense fewer analytes than would otherwise be desirable. One way to enable the reduction of the size of the sensor flex, or potentially add additional sensors to the sensor flex, may include positioning one or more of the electrodes on a back side of the sensor flex, which may include space which is not utilized for positioning of an electrode.

[0028] It may be difficult to dispose electrodes on both the front side and the back side of a sensor flex of a device because of the challenges associated with the fabrication of such devices. For example, internal components of the sensor flex may be fabricated at wafer scale on a substrate. For example, the sensor flex may include a film that has a metal composition of the electrode disposed on a particular region of the film to define the electrode. The film may be called a base layer, which functions while the device is in operation (e.g., inside a patient’s body) to structurally support and electrically insulate the electrodes disposed on the sensor flex from each other. During fabrication of the device, the base layer may be disposed on a substrate while one or more metal compositions are deposited on the base layer to define the electrodes. The base layer may be removed from the substrate after the electrodes are deposited and housed inside the sensor flex during operation of the device.

[0029] In techniques for fabricating internal components of a sensor flex which includes electrodes disposed on only a front side of the base layer, one or more metal compositions may be deposited (e.g., sputtered, vapor deposited, or the like) on the top of the base layer in particular regions while the bottom of the base layer (which may become the back side while the device is in operation) is disposed on the substrate. The metal compositions may be furtherDocket No.: A0011989W001 / 1277-126W001 processed to form the working electrode, the counter electrode, a reference electrode, a background electrode, or combinations of these electrodes. The base layer may then be cut to size, removed from the substrate, and included into the sensor flex to form the device.Accordingly, each of the electrodes of the sensor flex may be disposed on the front side of the base layer, which was the top side of the base layer during fabrication. Thus, the sensor flex may include only electrodes which are disposed on the front side of the sensor flex. As such, the sensor flex may relatively larger (e.g., in length and / or diameter) than would otherwise be possible if the back side of the sensor flex were available to position one or more electrodes.

[0030] Inclusion of one or more electrodes on the back side of the sensor flex may be relatively challenging because such an arrangement may necessitate positioning one or more components between the base layer and the substrate during fabrication. Since the base layer may be peeled from the substrate after the electrodes are deposited on the base layer, components or materials disposed (e.g., positioned) between the base layer and the substrate may preferentially adhere to the substrate or otherwise not be removed with the base layer when the base layer is removed from the substrate. This condition may generally be referred to as “delamination.”

[0031] Certain devices may position a single electrode on the back side of the sensor flex. However, such an electrode is generally a uniform layer which covers the entire back side of the base layer, because such an arrangement may mitigate the occurrence or severity of delamination. For example, it may be relatively easier to successfully peel a single uniform layer along with the base layer from the substrate without delamination than it is to peel a layer or layers that include void areas, or complex geometries, or non-uniform thicknesses, or the like. Although a device which includes one electrode covering all of the surface area on the back side of the sensor flex may be desirable relative to a device that includes only electrodes positioned on the front side of the sensor flex, still further improvements may be desirable. For example, a device which includes an electrode disposed in a pattern that covers less than all of the surface area on the sensor flex on the back side of the sensor flex may enable a reduction in size of the sensor flex and / or may enable inclusion of additional sensors on a sensor flex that remains the same size. However, such an arrangement may exacerbate challenges associated with delamination during fabrication.

[0032] As described above, in accordance with one or more aspects of the present disclosure, devices and techniques for fabricating such devices may address one or more of these challenges. Devices according to the present disclosure may include at least one electrode that defines a pattern on the back side of the sensor flex. Selective patterning of one or more electrodes on the back side of the sensor flex such that the back side of the sensor flex does not include only a uniform layer covering all of the surface area of the base layer may enable a number of desirableDocket No.: A0011989W001 / 1277-126W001 properties. For example, devices according to the present disclosure may enable configurability of the back side of the sensor flex. Such configurability may enable better sensor performance by selective patterning of the shape, size, location, and thickness of the electrodes of the sensor. Furthermore, devices according to the present disclosure may enable reduction in size of the sensor flex, or may enable inclusion of additional sensors configured to sense the same or a different analyte on the sensor flex, or both. For examples, disclosed herein are devices which are configured to sense multiple analytes, which may enable better patient care outcomes.

[0033] In some cases, the at least one electrode disposed on the back side of the sensor flex may include at least two electrodes. In some examples, the at least two electrodes on the back side of the sensor flex may include at least two different types of electrodes. The electrode types may be selected from the group of working electrodes, counter electrodes, reference electrodes, and background electrodes. In some examples, the at least two electrodes may include a different metal composition than each other, a different thickness than each other, a different geometry than each other, or all of the above. Such configurability of the back side of the sensor flex may enable development of improved sensors.

[0034] Also disclosed herein are techniques for fabricating such devices. According to techniques disclosed herein, a device includes a sensor flex which includes an electrode that defines a pattern on the back side of the sensor flex may be fabricated. Fabrication of the disclosed devices may include fabricating the sensor flex of the device. The sensor flex may include an electrode pair that includes a working electrode and a counter electrode. The sensor may optionally include a reference electrode and / or a background electrode. At least one of the electrodes may be disposed on the back side of the sensor flex, and the electrode or electrodes disposed on the back side of the sensor flex may define a pattern such that the back side electrode covers less than all of the surface area on the back side of the sensor flex, or less than all of the surface area of a base layer housed by the sensor flex.

[0035] The back side electrodes are primarily described below as counter electrodes. This is because it is generally considered that counter electrodes may be relatively less complicated to fabricate than working electrodes and generally ultimately include fewer components than a working electrode. However, it should be understood that the disclosed devices and techniques may include any one or more than one type of electrode positioned on the back side of the sensor flex.

[0036] Fabrication of devices disclosed herein may include depositing a metal composition of the back side electrode directly on a substrate. The substrate may be prepared in a way that tailors the adhesion of the deposited metal composition of the back side electrode to the substrate in a way that helps the back side electrode survive further processing, but weak enough to allowDocket No.: A0011989W001 / 1277-126W001 removal of the back side electrode with the base layer for assembly. For example, the substrate, which may be glass, may be polished, roughened, or coated to tailor the level of the adhesion of metal compositions deposited on the substrate.

[0037] The metal composition of the back side electrode may be deposited by sputtering, or physical vapor deposition, or electron beam, or another suitable process in a pattern. The pattern may define more than one back side electrode (e.g., two back side electrodes, three back side electrodes, or four back side electrodes), or may define void areas and / or areas of non-uniform thickness in a single back side electrode. The metal composition of the back side electrode may include any suitable material for forming an electrode with an electroactive surface. For example, the metal composition of the counter electrode, the working electrode, the reference electrode, and / or the background electrode may include gold, silver, copper, platinum, combinations thereof, or the like. The metal compositions of the different types of electrodes may be the same as each other or may be different from each other.

[0038] In examples that include multiple electrodes on the back side of the sensor flex, the back side electrodes may be deposited on the substrate such that the back side electrodes are displaced from each other. In some examples, another material may be deposited between the displaced back side electrodes. For example, regions of the substrate that are not covered by the deposited metal composition(s) of the back side electrodes may be covered by another deposited material. In some examples, the material may be a hardmask material. The hardmask material may include at least one of a titanium nitride, tantalum nitride, or an amorphous carbon.

[0039] After depositing the metal composition of the back side electrode on the substrate, one or more processing steps may be performed before additional layers are applied or deposited. These processing steps may define the geometry of the back side electrode or electrodes. For examples, one or more photolithography, etching, and / or rinsing steps may define the geometry of the back side electrode, a back side electrode contact pad in the connection portion of the sensor flex, and one or more sensor traces that electrically connect the back side electrode to the back side electrode contact pad with a relatively thin line of the metal composition.

[0040] In accordance with one or more examples of the present disclosure, one or more pillars may be deposited immediately before or immediately after deposition of the metal composition of the back side electrode. The depositing of the one or more pillars may improve adhesion of the back side electrode or electrodes to the subsequently applied base layer.

[0041] The one or more pillars may be disposed at an interface of the back side electrode and the insulation layer, at an interface between the substrate and the back side electrode, or both. In some examples, a pillar may define an axial edge of a back side electrode, or pillars may define both axial edges of a back side electrode. The one or more pillars may function as anchor pointsDocket No.: A0011989W001 / 1277-126W001 which reduce or prevent delamination of the back side electrode and subsequent layers when the base layer is removed from the substrate. In some examples, the one or more pillars may include titanium. Furthermore, in some examples, the one or more pillars may define a thickness perpendicular to the substrate of between about 1 micrometers and about 5 micrometers. The use of titanium as a pillar material may be desirable relative to other materials including gold, silver, copper, or platinum, because titanium may further improve adhesion of the back side electrode to the base layer, and thus reduce the risk of delamination, relative to these other metals. The use of “about” herein is to indicate that there may be manufacturing tolerances based on the applied manufacturing techniques, and may be plus or minus 5%, 10%, 20%, or 30% from the example range.

[0042] In some examples, in addition to or rather than deposition of one or more pillars, one or more bond layers may be deposited onto all or part of the metal composition of the back side electrode or coated (e.g., by electrode deposition, surface sputtering, or the like) onto the base layer such that the one or more bond layers are disposed at the interface between the back side electrode and the base layer. Similar to the one or more pillars, the bond layer may improve adhesion of the back side electrode to the base layer. The bond layer may include titanium, which may form a stronger bond between the back side electrode and the base layer than the bond formed between the back side electrode and the substrate.

[0043] Fabrication of the sensor flex may further include applying the base layer to the back side electrode on the substrate. In some examples, the base layer may include a chemicalresistant, dimensionally-stable, and electrically-insulative polymeric material. For example, the polymeric material may be polyimide. The base layer may be applied by, for example, spin casting the polymeric material onto the substrate and deposited back side electrode and then precuring the polymeric material.

[0044] After applying the base layer to the substrate over the back side electrode, the base layer may be patterned. For example, one or more etch steps (e.g., wet-etch and / or dry-etch) may be included. Fabrication of the device may proceed to building one or more front side electrodes on the front side of the base layer. For example, one or more front side electrodes may be disposed on top of the base layer, such as one or more working electrodes, one or more counter electrodes, one or more reference electrodes, one or more background electrodes, associated contact pads and sensor traces, and the like.

[0045] Devices disclosed herein are described primarily with respect to continuous glucose monitors. Other monitors configured to sense other analytes are also considered.

[0046] FIG. 1 is a conceptual diagram illustrating an example system 110 that includes an implantable medical device (IMD) configured to measure the glucose levels of a patient 112 inDocket No.: A0011989W001 / 1277-126W001 accordance with one or more examples described in this disclosure. FIG. 1 illustrates system 110 that includes insulin pump 114, tubing 116, infusion set 118, monitor 100 (e.g., a glucose level monitoring device comprising a glucose sensor), and patient device 124. Insulin pump 114 may be described as a tethered pump, because tubing 116 tethers insulin pump 114 to infusion set 118. In some examples, rather than utilizing a tethered pump system comprising insulin pump 114, tubing 116, infusion set 118, and / or monitor 100, patient 112 may utilize a patch pump. Instead of delivering insulin via tubing and an infusion set, a pump patch may deliver insulin via a cannula extending directly from an insulin pump. In some examples, a glucose sensor may also be integrated into such an insulin pump (e.g., a so-called “all-in-one (AIO) insulin pump”).

[0047] Moreover, it is not necessary for system 110 to include insulin pump 114, tubing 116, or infusion set 118. For instance, it may be desirable to measure glucose level of patient 112 without needing to deliver insulin via insulin pump 114 or a patch pump. For purposes of description, the following describes a manner in which insulin may be delivered to patient 112, and possibly in conjunction with measurements from monitor 100.

[0048] Patient 112 may be diabetic (e.g., Type 1 diabetic or Type 2 diabetic), and therefore, the glucose level in patient 112 may be controlled with delivery of supplemental insulin. For example, patient 112 may not produce sufficient insulin to control the glucose level or the amount of insulin that patient 112 produces may not be sufficient due to insulin resistance that patient 112 may have developed.

[0049] To receive the supplemental insulin, patient 112 may carry insulin pump 114 that couples to tubing 116 for delivery of insulin into patient 112. Infusion set 118 may connect to the skin of patient 112 and include a cannula to deliver insulin into patient 112. Monitor 100 may also be coupled to patient 112 to measure glucose level in patient 112. Insulin pump 114, tubing 116, infusion set 118, and monitor 100 may together form an insulin pump system.

[0050] Monitor 100 may include a glucose sensor with an electrode pair (e.g., a working electrode and a counter electrode) that is inserted under the skin of patient 112 and positioned on a sensor flex (e.g., in vivo), such as near the stomach of patient 112 or in the arm of patient 112 (e.g., subcutaneous connection). The glucose sensor of monitor 100 may be configured to measure the interstitial glucose level, which is the glucose found in the fluid between the cells of patient 112. Monitor 100 may be configured to continuously, periodically, or in response to user request sample the glucose level and rate of change of the glucose level over time.

[0051] In one or more examples, insulin pump 114, monitor 100, and / or the various components illustrated in FIG. 1, may together form a closed-loop therapy delivery system. For example, patient 112 may set a target glucose level, usually measured in units of milligrams per deciliter (mg / dL), on insulin pump 114. Insulin pump 114 may receive the current glucose levelDocket No.: A0011989W001 / 1277-126W001 from monitor 100 and, in response, may increase or decrease the amount of insulin delivered to patient 112. For example, if the current glucose level is higher than the target glucose level, insulin pump 114 may increase the insulin. If the current glucose level is lower than the target glucose level, insulin pump 114 may temporarily cease delivery of the insulin. Insulin pump 114 may be considered as an example of an automated insulin delivery (AID) device. Other examples of AID devices may be possible, and the techniques described in this disclosure may be applicable to other AID devices.

[0052] Insulin pump 114 and monitor 100 may be configured to operate together to mimic some of the ways in which a healthy pancreas works. Insulin pump 114 may be configured to deliver basal dosages, which are small amounts of insulin released continuously throughout the day. There may be times when glucose levels increase, such as due to eating or some other activity that patient 112 undertakes. Insulin pump 114 may be configured to deliver bolus dosages on demand in association with food intake or to correct an undesirably high glucose level in the bloodstream. In one or more examples, if the glucose level rises above a target level, then insulin pump 114 may deliver a bolus dosage to address the increase in glucose level.Insulin pump 114 may be configured to compute basal and bolus dosages and deliver the basal and bolus dosages accordingly. For instance, insulin pump 114 may determine the amount of a basal dosage to deliver continuously and then determine the amount of a bolus dosage to deliver to reduce glucose level in response to an increase in glucose level due to eating or some other event.

[0053] Accordingly, in some examples, monitor 100 may sample glucose levels for determining rate of change in glucose level over time. Monitor 100 may output the glucose level to insulin pump 114 (e.g., through a wireless link connection like Bluetooth). Insulin pump 114 may compare the glucose level to a target glucose level (e.g., as set by patient 112 or a clinician) and adjust the insulin dosage based on the comparison. In some examples, insulin pump 114 may adjust insulin delivery based on a predicted glucose level (e.g., where glucose level is expected to be in the next 30 minutes).

[0054] As described above, patient 112 or a clinician may set one or more target glucose levels on insulin pump 114. There may be various ways in which patient 112 or the clinician may set a target glucose level on insulin pump 114. As one example, patient 112 or the clinician may utilize patient device 124 to communicate with insulin pump 114. Examples of patient device 124 include mobile devices, such as smartphones, tablet computers, laptop computers, and the like. In some examples, patient device 124 may be a special programmer or controller (e.g., a dedicated remote-control device) for insulin pump 114. Although FIG. 1 illustrates one patient device 124, in some examples, there may be a plurality of patient devices. For instance, systemDocket No.: A0011989W001 / 1277-126W001 110 may include a mobile device and a dedicated wireless controller, each of which is an example of patient device 124. For ease of description only, the example techniques are described with respect to patient device 124 with the understanding that patient device 124 may be one or more patient devices.

[0055] Patient device 124 may also be configured to interface with monitor 100. As one example, patient device 124 may receive information from monitor 100 through insulin pump 114, where insulin pump 114 relays the information between patient device 124 and monitor 100. As another example, patient device 124 may receive information (e.g., glucose level or rate of change of glucose level) directly from monitor 100 (e.g., through a wireless link).

[0056] In one or more examples, patient device 124 may comprise a user interface with which patient 112 or the clinician may control insulin pump 114. For example, patient device 124 may comprise a touchscreen that allows patient 112 or the clinician to enter a target glucose level. Additionally, or alternatively, patient device 124 may comprise a display device that outputs the current and / or past glucose level. In some examples, patient device 124 may output notifications to patient 112, such as notifications if the glucose level is too high or too low, as well as notifications regarding any action that patient 112 needs to take. In some examples, monitor 100 and insulin pump 114 of an insulin pump system may be packaged together such that an electrochemical cell or working electrode of the glucose sensor may be placed relatively near an insulin delivery site on the patient.

[0057] The glucose sensor of monitor 100 includes a working electrode and a counter electrode. The working electrode and the counter electrode form an electrode pair which reacts with an analyte and generates an electrical signal. The electrical signal may include, for example, a voltage, an electrical current, or an impedance. In general, the electrical current flowing through a working electrode of the glucose sensor of monitor 100 is indicative of the glucose level in the patient’s interstitial fluid. For example, the electrical signal may be proportional to the concentration of glucose in an interstitial fluid layer of patient 112. In some examples, the working electrode may be part of an electrochemical cell configured to measure voltage, current as an interstitial signal (iSig), or impedances. In some examples, the glucose sensor of monitor 100 may use the working electrode to sense glucose values in a patient. The electrode pair may be positioned on a sensor flex of monitor 100.

[0058] Processing circuitry of monitor 100 may sense glucose levels in a patient by measuring an operating parameter of the working electrode of the glucose sensor of monitor 100 and determining a glucose value from the measured operating parameter. For example, processing circuitry may measure the amount of electrical current flowing through the working electrode, where different amounts of current are indicative of different glucose values in aDocket No.: A0011989W001 / 1277-126W001 patient. The relation between electrical current and glucose values may be represented by a formula in memory of monitor 100. The formula may include one or more factors, including one or more calibration factors. The processing circuitry may be configured to measure the one or more calibration factors. A pre-calibration value may be a calibration factor measured by processing circuitry at the time of manufacture / assembly of monitor 100. Alternatively, or in addition, a calibration value may be a calibration factor measured by processing circuitry at the time of installation of glucose monitor 100 on a patient. When processing circuitry measures a new calibration factor, it may calibrate the glucose values sensed by the one or more working electrodes by replacing an old calibration factor in the formula with the new calibration factor. In this way, processing circuitry may update the calibration of monitor 100 based on the actual environment monitor 100 will be operating in, rather than relying solely on a calibration made at the time of assembly, manufacture, or initial calibration.

[0059] Processing circuitry may measure a calibration factor for one or more electrodes by measuring an operating parameter of the one or more electrodes and determining a glucose value from the measured operating parameter using the formula in memory. Processing circuitry may compare the determined glucose value to a known or given glucose value. Processing circuitry may determine what calibration factor is necessary (the measured calibration factor), when implemented in the formula, to arrive at the known or given glucose value.

[0060] Processing circuitry of the system which includes monitor 100 may be configured to measure one or more pre-calibration values of an operating parameter of one or more electrodes of monitor 100 at the time of manufacture / assembly of monitor 100. The processing circuitry may then store the pre-calibration values in a memory of the system. Before or during installation of monitor 100, the processing circuitry may measure one or more calibration values of the same operating parameter of one or more monitor electrodes of monitor 100. Processing circuitry may retrieve the one or more pre-calibration values from memory and determine one or more delta values using the one or more pre-calibration values and the one or more calibration values.

[0061] In accordance with one or more examples of the present disclosure, the glucose sensor of monitor 100 includes at least one electrode disposed on a back side of a sensor flex of the sensor opposite the front side of the sensor flex. The at least one electrode may define a pattern that covers less than all of the surface area on the back side of the sensor flex, or may define a non-uniform thickness on a base layer housed by the sensor flex. The location of at least one electrode which defines a pattern on the back side of the sensor flex may allow for one or more components of monitor 100 to be made smaller than these one or more components would otherwise be if all of the electrodes positioned on the sensor flex were positioned on the front side. For examples, the sensor flex of the glucose sensor of monitor 100 may be relativelyDocket No.: A0011989W001 / 1277-126W001 smaller in length and / or diameter, which may improve the comfort of patient 112 while wearing monitor 100. Additionally, or alternatively, the smaller size of the sensor flex of the glucose sensor of monitor 100 may allow patient 112 to wear monitor 100 for a longer period of time than would otherwise be possible because the site on patient 112 where monitor 100 is attached may become relatively less irritated by the presence of monitor 100. As such, monitor 100 may be easier to maintain or may provide better management of diabetes than a monitor which includes a glucose sensor that has all of the electrodes positioned on a front side of the sensor flex.

[0062] In some examples, the glucose sensor of monitor 100 includes a working electrode that is covered by a catalytic agent that reacts with glucose in the interstitial fluid of patient 112 to generate the electrical signal received by monitor 100. For example, the glucose sensor of monitor 100 may be an enzyme-based working electrode, which may include glucose oxidase (GOx), or glucose dehydrogenase (GDH), or the like, which react with glucose at the working electrode to generate the electrical signal. Alternatively, the working electrode may be a polymer-based working electrode, or may be a metal-based working electrode. In any case, the working electrode may define an electroactive surface at the exterior of the sensor flex that it is disposed on.

[0063] In some examples, rather than or in addition to making the sensor flex smaller due to the position of at least one electrode disposed in a pattern on the back side of the sensor flex, monitor 100 may include one or more additional sensors. At least one of the electrodes of the additional sensor may be displaced from the first back side electrode on the back side of the same sensor flex as glucose sensor of monitor 100. The working electrode of the additional sensor may be covered with the same or a different catalytic agent that is configured to react with glucose, which may increase the reliability of the glucose measurement of monitor 100 (e.g., by averaging the measurement of two sensors configured to measure glucose). In some examples, the additional working electrode or working electrodes may be covered with a different catalytic agent which reacts with a different analyte in patient 112. For example, monitor 100 may include a first counter electrode on a back side of a sensor flex that includes a first front side working electrode covered with a catalytic agent configured to react with glucose, a second back side counter electrode and a second front side working electrode covered with a catalytic agent configured to react with a second analyte, and third back side counter electrode and a third front side working electrode configured to react with a third analyte.

[0064] In this way, devices according to the present disclosure may allow for multi-analyte sensing. In some examples, a corresponding counter electrode for each of the first working electrode, the second working electrode, and the third working electrode may be disposed on theDocket No.: A0011989W001 / 1277-126W001 back side of the sensor flex. Information about the levels of the second analyte and / or the third analyte may be used by system 110 alone or in combination with information from the glucose sensor of monitor 100 to tailor or recommend treatment. In this way, aspects of the present disclosure may enable use available space on the back side of the sensor flex that typically is not used. Using the back side of the sensor flex to dispose one or more electrodes may enable improved comfort and care of patient 112.

[0065] In examples where a sensor or sensors are added to the sensor flex, the back side electrode disposed on the back side of the sensor flex may be a counter electrode that is common to each of the sensors of monitor 100. Stated similarly, the back side electrode may be a counter electrode shared by each of the sensors, which each have their own working electrode. Since space on the back side of the sensor flex may not be as limited as it is on the front side of the sensor flex, the back side electrode may be sized such that optimal or nearly optimal electrical efficiency may be achieved. Alternatively, more than one counter electrode may be disposed on a back side of the sensor flex, or another type of electrode may be disposed on the back side of the sensor flex.

[0066] FIG. 2A is a conceptual cross-sectional view of an example monitor 200 from the front side. FIG. 2B is a conceptual diagram of the back side of monitor 200. Monitor 200 is positioned on patient 212 and is configured to monitor a level of an analyte of patient 212.Monitor 200 may be different than monitor 100 of FIG. 1, where monitor 200 includes electrodes on only a front side of a sensor flex. Monitor 200 includes monitor housing 220 which contains electronics and processing circuitry of monitor 200. Monitor housing 220 is adhered to external surface 216 of epidermal layer 214 of patient 212 by dermal adhesion 222. Epidermal layer 214 is positioned above dermal layer 217, which is positioned above interstitial fluid layer 218 of patient 212. In some examples, dermal layer 217 and interstitial fluid layer 218 may be the same layer of patient 212 (e.g., a dermal layer of the skin). In some examples, as illustrated, interstitial fluid layer 218 may be a layer of subcutaneous tissue below the dermal layer 217 of patient 212.

[0067] Monitor 200 further includes sensor 230 positioned on sensor flex 240. Sensor flex 240 extends from first axial end 242 to second axial end 244. Sensor 230 includes counter electrode 232, working electrode 234, and reference electrode 236. As such, sensor 230 is configured as a three-wire sensor. In FIG. 2A, counter electrode 232, working electrode 234, and reference electrode 236 are disposed on front side 241 of sensor flex 240. Therefore, monitor 200 is illustrated for comparison to devices of the present disclosure, where at least one electrode is disposed on back side 243. As illustrated in FIG. 2B, monitor 200 includes only sensors disposed on front side 241 of sensor flex 240, leaving space on back side 243 of sensor flex 240 unused.Docket No.: A0011989W001 / 1277-126W001

[0068] Sensor flex 240 extends along length Li from first axial end 242 connecting sensor flex 240 to monitor housing 220 at external surface 216 of epidermal layer 214 to second axial end 244 in interstitial fluid layer 218. In some examples, interstitial fluid layer 218 may be a layer of subcutaneous tissue forming the deepest layer of the patient’s skin. In such examples, length Li may be in a range of from about 2 millimeters (mm) to about 4 mm. In some examples, length Li of sensor flex 240 may cause irritation or discomfort to patient 112, and / or may penetrate so deeply into interstitial fluid layer that no additional length may be added to make room for additional working electrodes of additional sensors configured to sense the level of a different analyte.

[0069] FIGS. 3A-3B is a conceptual cross-sectional view of an example monitor 300, in accordance with one or more examples of the present disclosure. Monitor 300 is illustrated from a front side in FIG. 3A and from a back side opposite the front side in FIG. 3B. Monitor 300 may be an example of monitor 100 of FIG. 1. Monitor 300 of FIG. 3 may be generally described similarly to monitor 100 of FIG. 1 and monitor 200 of FIG. 2, except where differing as described below. Similar reference numerals indicate similar elements.

[0070] Monitor 300 includes monitor housing 320, sensor flex 340, and sensor 330. Unlike monitor 200, monitor 300 of FIGS. 3A-3B includes counter electrode 332 of sensor 330 that is not disposed on front side 341 of sensor flex 340 but is rather disposed on back side 343 of sensor flex 340. In the illustrated example, counter electrode 332 defines a pattern on back side 343 of sensor flex 340 such that counter electrode 332 covers less than all of the surface area on the back side of sensor flex 340. Such a pattern may be defined by deposition of the counter electrode 332 during fabrication, rather than by covering portions of counter electrode 332 with the housing of the sensor flex. Such an arrangement may improve the electrical performance of sensor 330 in operation and may further reduce consumption of the metal composition of counter electrode 332 during fabrication. Counter electrode 332 may include any suitable material for the electrical circuit such that the surface of counter electrode 332 is electroactive. In some examples, counter electrode 332 may include a metal composition that includes one or more of platinum, gold, silver, or copper.

[0071] Monitor 300 of FIGS. 3A-3B, which includes counter electrode 332 disposed on a portion of back side 343 of sensor flex 340 of sensor 330, may have one or more components that are reduced in size relative to monitor 200 of FIGS. 2A-2B, which includes only electrodes positioned on front side 241 of sensor flex 240. For example, sensor flex 340 may extend along length L2 from first end 342 to second end 344. Length L2 may be between about may be in a range of from about 0.5 mm to about 2.0 mm. As illustrated, monitor 300 may, in some examples, penetrate less than about halfway through interstitial fluid layer 318. The relativelyDocket No.: A0011989W001 / 1277-126W001 shorter length of sensor flex 340 may increase patient comfort of patient 312 while wearing monitor 300 relative to monitor 200 of FIG. 2. Additionally, or alternatively, the reduced size of the transcutaneous components of monitor 300 may reduce irritation of tissue surrounding monitor 300, thus reducing the need to remove monitor 300 as frequently as would be required with monitor 200 of FIG. 2.

[0072] FIGS. 4A-4B are conceptual cross-sectional views of an example monitor 400.Monitor 400 is illustrated from a front side in FIG. 4A, and is illustrated from a back side in FIG.4B. Monitor 400 may be an example of monitor 100 of FIG. 1. Monitor 400 of FIG. 4 may be generally described similarly to monitor 100 of FIG. 1, monitor 200 of FIG. 2, and monitor 300 of FIG. 3, except where differing as described below. Similar reference numerals indicate similar elements.

[0073] Monitor 400 is configured as a multi -analyte monitor. As such, monitor 400 includes first sensor 430A. First sensor 430A includes counter electrode 432A, working electrode 434A, and reference electrode 436A. Counter electrode 432A is disposed on back side 443 of sensor flex 440 while working electrode 434A and reference electrode 436A are disposed on front side 441. First sensor 430A may be configured to sense a first analyte, which may be glucose.Monitor 400 also includes second sensor 430B. Second sensor 430B includes counter electrode 432B, working electrode 434B, and reference electrode 436B. Similar to first sensor 430A, counter electrode 432B of second sensor 430B is disposed on back side 443 of sensor flex 440 while working electrode 434B and reference electrode 436B are disposed on front side 441. Counter electrode 432B is displaced from counter electrode 432A. It is also considered that counter electrode 432B could be disposed on front side 441, and working electrode 434B could be disposed on back side 443. Second sensor 430B may be configured to sense a second analyte, which may be insulin, creatinine, ketones, lactate, alcohol, sodium, potassium, or chloride.Monitor 400 also includes third sensor 430C. Third sensor 430C includes counter electrode 432C, working electrode 434C, and reference electrode 436C. Third sensor 430C may be configured to sense a third analyte, which may be potassium. Counter electrode 432C is also disposed on back side 443 of sensor flex 440, and is displaced from counter electrodes 432A, 432B.

[0074] Sensor flex 440 of monitor 400 extends along length Li from first end 442 to second end 444. As illustrated, length Li of the sensor flex 440 of monitor 400 is equal to length Li of sensor flex 240 of FIG. 2. Thus, in the illustrated example, monitor 400, which includes multiple back side electrodes in a pattern on back side 443 of sensor flex 440, may allow for sensing of a second analyte and a third analyte, each of which is different than the first analyte, without increasing the size (e.g., diameter or length) of a similar single-analyte monitor which positionsDocket No.: A0011989W001 / 1277-126W001 all of the electrodes on front side 441 of the sensor flex. With the electrical signals indicative of the second analyte from second sensor 43 OB and the third analyte from third sensor 43 OC, monitor 400 may provide more information about the physiological conditions of a patient than a single analyte sensor (e.g., monitor 200). The additional information may be used by processing circuitry of monitor 400 to tailor treatment strategies, without requiring a larger sensor flex or additional monitoring devices located at different monitoring sites. The length of sensor flex 440 and sensor flex 240 being the same is one example, and in other examples, the lengths may be different, including examples where sensor flex 440 is longer than sensor flex 240.

[0075] FIGS. 5A-5B are conceptual side views of an example monitor 500, in accordance with one or more examples of the present disclosure. FIG. 5A illustrated monitor 500 from a front side while FIG. 5B illustrates monitor 500 from a back side. Monitor 500 may be an example of glucose monitor 100 of FIG. 1. Monitor 500 of FIGS. 5A-5B may be generally described similarly to glucose monitor 100 of FIG. 1, monitor 200 of FIGS. 2A-2B, monitor 300 of FIGS. 3A-3B, and monitor 400 of FIGS. 4A-4B, except where differing as described below. Similar reference numerals indicate similar elements.

[0076] Monitor 500 includes a glucose monitor and an insulin pump. In the example shown, monitor 500 includes a glucose monitor and an insulin delivery device packaged together.

[0077] Sensors 530A, 530B, and 530C of monitor 500 are configured as 2-wire sensors rather than the 3 -wire sensors of monitor 400. As such, monitor 500 does not include any reference electrodes. Instead, sensors 530A, 530B, and 530C are supplied with power and signal their state through only counter electrodes 532A, 532B, and 532C, and working electrodes 534A, 534B, and 534C. Arranging one or more of sensors 530A, 530B, and / or 530C as a two-wire sensor may advantageously improve ease of wiring and / or may be more compact with the limited space on sensor flex 540, through the omission of reference electrodes.

[0078] Monitor 500 may inserted into a patient (112, FIG. 1) a single time and include both insulin delivery and glucose monitoring functionalities, e.g., so that patient 112 does not need to have two different devices inserted, e.g., two different insertions. In the example shown, monitor 500 includes monitor housing 520, sensor flex 540, and delivery lumen 550 (e.g., which is an example cannula coupled to an infusion pump within medical device 500). Monitor housing 520 may be configured to house the glucose monitor (not shown) and the insulin pump (not shown), such that sensor flex 540 and delivery lumen 550 may be inserted into patient 112 and separated laterally.

[0079] Sensor flex 540 includes analyte sensors 530A, 530B, and 530C. In the example shown, sensor flex 540 includes three working electrodes 534A, 534B, and 534C disposed on front side 541 of sensor flex 540. Each of the individual working electrodes forms an electrodeDocket No.: A0011989W001 / 1277-126W001 pair with a respective counter electrode 532A, 532B, 532C disposed on back side 543 of sensor flex 540. In this way, three separate sensors 530A, 530B, and 530C, e.g., working-counter electrode pairs providing three separate sensor signals may be formed. For example, counter electrode 532A and working electrode 534A may form an electrode pair that makes up sensor 530A, counter electrode 532B and working electrode 534B may form an electrode pair that makes up sensor 530B, and counter electrode 532C and working electrode 534C may form an electrode pair that makes up sensor 530C. Sensor flex 540 may optionally include one or more reference electrodes if it is desired to arrange one or more of the sensors as a three-wire sensor. Sensor flex 540 may be connected to the electronics within monitor housing 520 at connection portion 545 of sensor flex 540 disposed adjacent to first axial end 542, while sensing portion 547 is disposed adjacent to second axial end 544.

[0080] Delivery lumen 550 may be connected to an infusion set and / or an insulin pump housed within monitor housing 520, and may be configured to deliver insulin through an aperture in fluid communication with a lumen of delivery lumen 550 and inserted within a patient (112, FIG. 1). In the example shown, delivery lumen 550 may output the fluid at distal end 552. As illustrated, devices according to the present disclosure may be integrated into an “all-in-one” device which is configured to both monitor an analyte level and deliver treatment.

[0081] FIG. 6 is a block diagram illustrating components of monitor 600. For instance, FIG.6 is a block diagram of sensor electronics device 630 according to an example of the disclosure. Monitor 300 (FIGS. 3A-3B), monitor 400 (FIGS. 4A-4B), monitor 500 (FIGS. 5A-5B), and / or may include one or more processors configured to perform example techniques, although the techniques will primarily be described with respect to monitor 400 of FIGS. 4A-4B. Sensor electronics device 630 may be part of the one or more processors. In one or more examples, the monitor 600 may be considered as including the electrodes used for determining the analyte level. Sensor electronics device 630 may be configured to determine the level of one or more analytes. Sensor electronics device 630 may be connected to a one or more sensors (430A, 430B, 430C, FIGS. 4A-4B). Each individual sensor may include a biomolecule or some other catalytic agent, and may be placed in a human body in a vascular or non-vascular environment. For example, working electrodes 434A, 434B, 434C may be placed in interstitial layer 418 on front side 441 of sensor flex 440, or in a vein and be subjected to a blood stream, or may be placed in a subcutaneous or peritoneal region of the human body. The sensors may each have a respective counter electrode 432A, 432B, 432C, which may be disposed on back side 443 of sensor flex 440.

[0082] Sensor electronics device 630 may include measurement processor 632, display and transmission unit 634, controller 636, power supply 638, and memory 640.Docket No.: A0011989W001 / 1277-126W001 In examples of the disclosure, measurement processor 632, display and transmission unit 634, and controller 636 may be formed as separate semiconductor chips. However, other examples may combine measurement processor 632, display and transmission unit 634, and controller 636 into a single or multiple customized semiconductor chips. In general, measurement processor 632 may be configured to receive a current, voltage, and / or impedance from sensors 430 A, 43 OB, 430C. Each of the sensors may generate an electrical signal indicative of a level (e.g. a concentration) of an analyte being measured. The sensors may generate the electrical signal indicative of the same analyte as the other sensors or a different analyte. For example, sensor 430A may generate an electrical signal may be indicative of a glucose level. The sensor signal may be measured at a working electrode 434A. In an example of the disclosure, the sensor signal may be a current (e.g., iSig) measured at the working electrode 434A. In another example of the disclosure, the sensor signal may be a voltage measured at the working electrode 434A of the sensor electrodes.

[0083] Measurement processor 632 receives the sensor signal (e.g., a measured current, voltage, and / or impedance) after the sensor signal is measured at the electrode (e.g., working electrode 434A). Measurement processor 632 may receive the sensor signal and calibrate the sensor signal utilizing reference values. For example, measurement processor 632 may calibrate the sensor signal utilizing reference values based on a known analyte quantity, e.g., a zeroanalyte measurement to determine a baseline sensor signal. In some examples, changes to the sensor over time may change the responsivity of the sensor, changing the sensor signal and measurement accuracy. Measurement processor 632 may utilize the reference values to adjust for changes over time. In an example of the disclosure, the reference values are stored in a reference memory (e.g., memory 640) and provided to measurement processor 632. Based on the sensor signals and the reference values, measurement processor 632 may determine an analyte measurement. Measurement processor 632 may store the analyte measurements in memory 640. The sensor measurements may be sent to display and transmission unit 634 to be either displayed on a display in or transmitted to an external device. Sensor 430B and sensor 430C may operate similarly to measure, record, store, display, and / or transmit the level of different analytes (e.g., sensor 430A senses glucose, sensor 430B senses lactate, and sensor 430C senses potassium).

[0084] Memory 640 may be any type of memory device and may be configured to store measurements produced by measurement processor 632, reference values used to determine glucose measurements from sensor signals, or other data used and / or produced by measurement processor 632 and / or controller 636. In some examples, memory 640 may further store software and / or firmware that is executable by measurement processor 632 and / or controller 636. For example, memory 640 may store base layer resistance module 642, which may store instructionsDocket No.: A0011989W001 / 1277-126W001 that, when executed, manipulate the measurements produced by measurement processor 632 to account for the back side position of counter electrodes 432A, 432B, 432C.

[0085] Since positioning counter electrode 432A on back side 443 of sensor flex 440 may increase the resistance in the electrical circuit of sensor 430A relative to a sensor which includes both electrodes disposed on front side 441 of sensor flex 440 because a base layer of the sensor flex internals may be disposed between the electrode pair, base layer resistance module 642 may execute one or more post-processing steps to filter or otherwise manipulate the measurements to account for the increased resistance, as will be further explained below. Since the electrodes of sensor 430A may be disposed on opposite sides of the dielectric base layer housed within sensor flex 440, inclusion of base layer resistance module 642 may be desirable in some examples to account for the location of working electrode 434A relative to counter electrode 432A.

[0086] Sensor electronics device 630 may be a single analyte or a multi-analyte monitor which includes a display to display one or more analyte level readings. However, such displays may not be needed, such as in examples where the display is provided by patient device 124.

[0087] Power supply 638 may be a battery. In other examples, different battery chemistries may be utilized, such as lithium-based chemistries, alkaline batteries, nickel metal hydride, or the like, and a different number of batteries may be used. Sensor electronics device 630 provides power to electrodes via power supply 638 through a cable and a cable connector.

[0088] Controller 636 may be a processor, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry. In some examples controller 636 may be configured to cause a specific voltage or current to be output to analyte sensors 430 A, 430B, 430C. Sensors 430A, 430B, 430C may receive the voltage level or value, which may be the same or different for each sensor. With reference to FIGS. 6 and 7, in an example of the disclosure, working electrodes 732A, 732B, and 732C of sensors 730A, 730B, and 730C, respectively and described with respect to FIG. 7, may receive the reference voltage from power supply 638. The application of the voltage level VSET may cause sensors 730A, 730B, and 730C to create a sensor signal (i Sig) 757A, 757B, 757C between their respective working electrode and counter electrodes 732A, 732B, 732C which are disposed on a back side of a sensor flex. Each of the individual iSig values may be indicative of a level of a different analyte being measured.

[0089] FIG. 7 is a block diagram illustrating example sensors 730A, 730B, and 730C in accordance with one or more examples of the present disclosure. In the schematic illustration of FIG. 7, power supply 638 under control of controller 636 may apply a bias voltage to each of first sensor 730A, second sensor 730B, and third sensor 730C. In the example shown, sensors 730A,Docket No.: A0011989W001 / 1277-126W001 730B, and 730C each include a counter electrode 732A, 732B, 732C which are disposed on a back side of a sensor flex and a working electrode 734A. 734B, 734C which are disposed on a front side of a sensor flex. Reference electrode 736 is a common reference electrode, which may be disposed on either the front side or the back side of a sensor flex.

[0090] In the example in FIG. 7, an operational amplifier (op amp) 770 or other servocontrolled device may connect to the sensors through a circuit / electrode interface 772. Op amp 770, utilizing feedback through the sensors, maintains a prescribed voltage between reference electrode 736 and working electrodes 734A, 734B, 734C (e.g., VSET) by adjusting the voltage at counter electrodes 732A, 732B, 732C, respectively. In some examples, the voltage at reference electrode 736 is from about -1000 mV to about 1000 mv. In some examples, a positive voltage may cause a current to be source at counter electrode 732A and sunk at working electrodes 734A, while a negative voltage may cause a current to be sourced at working electrodes 734A, 734B, 734C, and sunk at counter electrodes 732A, 732B, 732C. Working electrode 734A may be covered with a first catalytic agent, and as such may be configured to react with a first analyte, working electrode 734B may be covered with a second catalytic agent configured to react with a second analyte, and working electrode 734C may be covered with a third catalytic agent configured to react with a third analyte.

[0091] In an example sensing mode operation, current 757 A may flow from counter electrode 732A to working electrode 734A, current 757B may flow from counter electrode 732B to working electrode 734B, and current 757C may flow from counter electrode 732C to working electrode 734C. Counter electrodes 732A, 732B, 732C may balance the chemical reactions that are occurring at working electrodes 734 A, 734B, 734C. Measurement processor 632 of FIG. 6 may measure currents 757 to determine the electrochemical reaction between the respective sensor electrodes. The circuitry disclosed in FIG. 7 may be utilized in a long-term or implantable sensor or may be utilized in a short-term or subcutaneous sensor.

[0092] In this way, sensor electronics device 630 may monitor an electrical parameter of the electrical chemical cell, e.g., an electrical current that is proportional to the impedance of the electrochemical cell such as current 757A. For example, measurement processor 632 may provide a sensor signal to controller device 636. In one example, the sensor signal is a current 757A through a working electrode 734A of sensor 730A. Controller 636 may accumulate values for current 757A over a period of time and may calculate a rate of change of the current values. For example, controller 636 may calculate the slope of a plot of the current. Although described with respect to current 757A, the example techniques are applicable to the other current 757 and respective electrodes.Docket No.: A0011989W001 / 1277-126W001

[0093] In some examples, controller 636 may accumulate and measure changes in electrochemical impedance spectroscopy (EIS) (real and imaginary impedance at different frequencies), voltage at counter electrode 732A, and / or current through a background electrode. A background electrode is similar to a working electrode, but may not include a catalytic layer for breaking down and sensing an analyte. Like current through working electrode 734A, larger slopes / changes in these other sensor signals may indicate a need for a higher VSET, while lower slopes / changes in these other sensor signals may indicate a need for a lower VSET at working electrode 734A. In this way, sensor electronics device 630 may be configured to monitor EIS, voltage, and / or current through a background electrode similar to monitoring current 757 A as described herein.

[0094] Returning to FIG. 6, as discussed above, due to the increased resistance in the circuit stemming from the back side position of counter electrodes 732A, 732B, 732C, measured analyte levels by measurement processor 632 may calculate measured analyte levels that are relatively noisy when compared to those values measured by a device that includes only electrodes disposed on the front side of a sensor flex. As such, either of measurement processor 632 and / or controller 636 may execute base layer resistance module 642 to account for the position of a base layer of the sensor flex between working electrode 734A and counter electrode 732A Although base layer resistance module 642 is illustrated as software that executes on measurement processor 632 and / or controller 636, in some examples, base layer resistance module 642 may be fixed-function circuitry that is formed within measurement processor 632 and / or controller 636 or independent of measurement processor 632 and / or controller 636. In some examples, base layer resistance module 642 may be firmware that measurement processor 632 and / or controller 636 execute.

[0095] In some examples, to execute base layer resistance module 642, measurement processor 632 may perform one or more post-processes on the determined analyte measurement before storing the value in memory 640. For example, measurement processor 632 may remove one or more received values of the current 757A by one or both of a low-pass filter or a high-pass filter. Filtering may reduce or eliminate noise and / or improve the signal to noise ratio. In addition to removing noise from the data, measurement processor 632 may cause controller 636 to take one or more actions. For example, responsive to the presence of noise in current 757A that exceeds a threshold, measurement processor 632 may cause controller 636 to reduce VSET at working electrode 734A.

[0096] FIGS. 8A-8C are conceptual diagrams illustrating a portion of example sensor flex internals 860 of a sensor flex 840 of monitor 800. For example, FIGS. 8A-8C may illustrate sensor flex 840 without a housing of sensor flex 840 surrounding sensing portion 845 andDocket No.: A0011989W001 / 1277-126W001 connection portion 847 of sensor flex internals 860. Monitor 800 of FIGS. 8A-8C may be an example of monitor 100 of FIG. 1. FIG. 8A is a conceptual cross-sectional side view of sensor flex internals 860 being fabricated while being supported by substrate 802. FIG. 8B is a conceptual top view of front side 841 of sensor flex internals 860 of sensor flex 840 after removal from substrate 802. FIG. 8C is a conceptual bottom view of back side 843 of sensor flex internals 860 of sensor flex 840. In FIGS. 8B and 8C, front side 841 and back side 843 of sensor flex 840 are turned 90 degrees relative to the sensor flexes illustrated and described above.Sensor flex internals 860 are removed from substrate 802 after fabrication, as illustrated in FIGS.8B and 8C, such that sensor flex internal 860 includes front side electrodes and back side electrodes that contact the interstitial fluid of patient 112 in operation of monitor 800.

[0097] Sensor flex internals 860 includes base layer 804. Base layer 804 includes front side 841 facing away from substrate 802 and back side 843 adjacent to substrate 802. Counter electrode 832A is disposed on back side 843 of base layer 804. Working electrode 834, reference electrode 836, and counter electrode 832B are disposed on front side 841 of base layer 804. Counter electrode 832A is disposed in a pattern on back side 843 of base layer 804 such that counter electrode 832A covers less than all of the surface area of back side 843 of base layer 804, and less than all of the surface area on substrate 802.

[0098] Base layer 804 structurally supports and electrically separates front side electrodes 832B, 836, 834 disposed on front side 841 from counter electrode 832A disposed on back side 843 of base layer 804. Base layer 804 includes a chemical-resistant, dimensionally-stable, and electrically-insulative polymeric material. For example, base layer 804 includes polyimide.

[0099] Sensor flex internals 860 includes additional components, some of which function to keep sensor flex internals 860 from delaminating during fabrication and / or delaminating during a subsequent step where sensor flex internals 860 are removed (e.g., peeled) from substrate 802. For example, sensor flex internals 860 include pillars 810A, 810B, 810C (collectively “pillars 810”) disposed at or near back side 843 of base layer 804. Pillars 810 may be disposed at the interface between counter electrode 832A and substrate 802, or at the interface between counter electrode 832A and base layer 804, may extend through both locations, or may be disposed separately at each location. Pillars 810 may function during removal of sensor flex internals 860 from substrate 802. For example, pillars 810 may act as anchor points which adhere tightly to both counter electrode 832A and base layer 804, while adhering less tightly to substrate 802, which may be glass. Pillars 810 may include any suitable metal composition such as a metal composition which includes titanium. Inclusion of titanium in pillars 810 may reduce risk of delamination of internals 860 when removing internals 860 more than other metals, such as gold, silver, platinum, or other electrode materials. In some examples, an individual pillar of pillarsDocket No.: A0011989W001 / 1277-126W001 810 may define a pillar thickness of from about 1 micrometer and about 5 micrometers when measured in a direction perpendicular to substrate 802.

[0100] In some examples, as illustrated one or more pillars 810A, 810B of pillars 810 may define an axial edge of a back side electrode. Positioning at least one of pillars 810 at an axial edge of a back side electrode may reduce or eliminate cleavage, and subsequent delamination, of sensor flex internals 860 when sensor flex internals 860 are peeled from substrate 802.

[0101] Sensor flex internals 860 may include bond layer 820 disposed between counter electrode 832A and base layer 804. Inclusion of bond layer 820, in addition to or rather than pillars 810, may improve adherence of counter electrode 832A to base layer 804, which may improve the likelihood that counter electrode 832A is removed with sensor flex internals 860 after processing, rather than remaining stuck on substrate 802.

[0102] In some examples, as illustrated, counter electrode 832A may be the only electrode disposed on back side 843 of base layer 804. In such examples, counter electrode 832A may define a non-uniform thickness perpendicular to substrate 802. Pillars 810 and bond layer 820 may enable removal of counter electrode 832A from substrate 802 with sensor flex internals 860. In some examples, counter electrode 832A may extend from sensing portion 845 to connection portion 847, which may obviate the need for contact pads and sensor traces electrically connecting the electrode to the monitor housing. Counter electrode 832A may include a metal composition that includes gold.

[0103] Front side 841 of base layer 804 includes sensor traces 822. Sensor traces 822 may be a thin line of a metal composition that electrically connects working electrode 834 disposed at sensing portion 847 to contact pad 814A disposed in connecting portion 845, where contact pad 814A may be electrically connected to monitor 800. Similarly, reference electrode 836 may be connected by sensor traces 822 to contact pad 814B, and counter electrode 832B may be connected by sensor traces 822 to contact pad 814C.

[0104] Working electrode 834 includes metal composition 833 covered by analyte sensing layer 835. In some examples, metal composition 833 may include gold, silver, platinum, or copper, or another suitable metal. Analyte sensing layer 835 detectably alters an electrical signal present at working electrode 834 in the presence of an analyte. Where working electrode 834 is a glucose sensor, analyte sensing layer 835 may include glucose oxidase.

[0105] Reference electrode 836 may include any suitable metal composition such that the surface of reference electrode 836 is electroactive. In the illustrated example, reference electrode 836 includes silver / silver chloride. Counter electrode 832B may include the same or a different metal composition as counter electrode 832A, metal composition 833, or reference electrode 836. In the illustrated example, counter electrode 832B includes platinum. As such, devices andDocket No.: A0011989W001 / 1277-126W001 techniques disclosed herein may be used to selectively pattern a plurality of electrodes onto both back side 843 and front side 841 of base layer 804. The plurality of electrodes may define different thicknesses, shapes, and materials, and, as such, may provide configurability to an application to which monitor 800 is applied.

[0106] Insulation layer 812 may be disposed adjacent to base layer 804. Insulation layer 812 may cover and surround sensortraces 822 and electrically separate components disposed on front side 841. In some examples, insulation layer 812 may define first opening 811 A to contact pad 814A, second opening 81 IB to contact pad 814B, and third opening 811C to contact pad 814C. Openings 811 may allow for electrical connection of contact pads 814 to components outside of internals 860 of sensor flex 840. In some examples, insulation layer 812 may include a chemicalresistant, dimensionally-stable, and electrically-insulative polymeric material. For example, insulation layer 812 may include polyimide. In some examples, base layer 804 and insulation layer 812 may include different types of polyimide. Inclusion of different types of polyimide as base layer 804 and insulation layer 812 may advantageously allow for selective tailoring of mechanical and electrical properties.

[0107] Disposed over all or a portion of sensing portion 847 on front side 841 of base layer 804 may be optional electrode cover 824. In some examples, electrode cover 824 may protect front side electrodes during further processing, such as cutting sensor flex internals 860 out of a film of base layer 804. In some examples, electrode cover 824 may be removed before inclusion in sensor flex 840. Electrode cover 824 may be adhered to sensing portion 847 using adhesive 826.

[0108] FIGS. 9A-9C are conceptual diagrams illustrating a portion of example sensor flex internal 960 of a sensor flex 940 of monitor 900. Monitor 900 of FIGS. 9A-9C may be an example of monitor 800 of FIGS. 8A-8C. FIG. 9A is a conceptual cross-sectional side view of sensor flex internals 960 being fabricated while supported by substrate 902. FIG. 9B is a conceptual top view of front side 941 of sensor flex internals 960 of sensor flex 940 after removal from substrate 902. FIG. 9C is a conceptual bottom view of back side 943 of sensor flex internals of sensor flex 940. Some labels are omitted for clarity, but monitor 900 may generally be described similarly to monitor 800, differing only as described below.

[0109] Monitor 900 includes two back side counter electrodes 932A, 932B. Back side counter electrodes 932A, 932B are displaced from each other on back side 943 of base layer 904. Back side counter electrodes 932A, 932B are electrically connected by sensor traces 922 to contact pads 914A, 914B on back side 943 of base layer 904. Back side counter electrode 932A, 932B correspond to front side working electrodes 934A, 934B. As such, devices and techniquesDocket No.: A0011989W001 / 1277-126W001 described herein may selectively pattern back side 943 of base layer 904 to fabricate a multianalyte sensor.

[0110] FIGS. 10-12 are conceptual diagrams illustrating a portion of different example sensor flex internals of a sensor flex of a sensor according to the present disclosure. In each example, a counter electrode is disposed in a pattern on a back side of a base layer of a sensing portion, in accordance with one or more examples of the present disclosure.[oni] FIG. 10 illustrates a portion of internals 1060 of sensor flex 1040 of monitor 1000. Monitor 1000 may be an example of monitor 100 of FIG. 1. The illustrated portion is located near back side 1043 of base layer 1004 where it interfaces with substrate 1002. In some examples, as described above, more than one electrode may be disposed on back side 1043 of base layer 1004. For example, counter electrode 1032A and counter electrode 1032B may be displaced from each other and disposed on back side 1043 of base layer 104. In some examples, one or more additional materials may be disposed between counter electrodes 1032A, 1032B. The additional material may include hardmask material 1046 disposed on back side 1043 of base layer 1004. In some examples, hardmask material 1046 may include at least one of a titanium nitride, a tantalum nitride, or an amorphous carbon.

[0112] FIG. 11 illustrates a portion of sensor flex internals 1160 of sensor flex 1140 of monitor 1100. Monitor 1100 may be an example of monitor 100 of FIG. 1. The illustrated portion is located near back side 1143 of base layer 1104 where it interfaces with substrate 1102. In some examples, as described above, more than one electrode may be disposed on back side 1143 of base layer 1004. For example, counter electrode 1132A and counter electrode 1132B may be displaced from each other and disposed on back side 1043 of base layer 104. In some examples, counter electrodes 1132 A, 1132B may be deposited on substrate 1102 prior to applying base layer 1104. In some examples, subsequent to depositing counter electrodes 1132A, 1132B and prior to applying base layer 1104, one or both of counter electrodes 1132A, 1132B may be annealed. In some examples, to anneal counter electrodes 1132A, 1132B, the counter electrodes and substrate 1102 may be heated after deposition of counter electrodes 1132A, 1132B. An annealing step may improve the workability of counter electrodes 1132A, 1132B, which may reduce or eliminate delamination during removal of sensor flex internals 1160 from substrate 1102.

[0113] FIG. 12 illustrates a portion of internals 1260 of sensor flex 1240 of monitor 1200. Monitor 1200 may be an example of monitor 100 of FIG. 1. The illustrated portion is located near back side 1243 of base layer 1204 where it interfaces with substrate 1202. In some examples, counter electrode 1232 may be disposed at back side 1243 of base layer 1204 in a pattern which defines a non-uniform thickness measured perpendicular to surface 1256 ofDocket No.: A0011989W001 / 1277-126W001 substrate 1202. The non-uniform thickness of counter electrode 1232 may selectively tailor the electrical properties or other properties of counter electrode 1232 during operation of monitor 1200 in a patient’s body. Titanium pillars 1210 may be selectively disposed at particular locations, which may reduce or eliminate delamination of internals 1260 when internals 1260 are removed from substrate 1202. In some examples, titanium pillars 1210A, 1210B may be disposed at the same axial position as each other but be displaced from each other in the stack. Such an arrangement may advantageously reduce the frequency or severity of delamination. In some examples, pillars 1210A, 1210B may be disposed at or near a thickest portion of non-uniform counter electrode 1232, which may also reduce or eliminate delamination.

[0114] FIG. 13 is a flowchart illustrating an example technique for fabricating a medical device, in accordance with one or more examples of the present disclosure. The illustrated technique may be used to fabricate portions of any of the above-described monitors. However, the above-described monitors may be manufactured according to other techniques. The illustrated technique is described primarily with respect to monitor 800 of FIGS. 8A-8C.

[0115] One or more pillars 810 may be deposited on substrate 802 (1302). Pillars 810 may include titanium in the metal composition. Pillars 810 may be deposited using physical vapor deposition (e.g., sputtering or electron beam deposition). Pillars 810 may be deposited on substrate 802 in a particular pattern. For example, pillars 810A, 810B may be deposited such that pillars 810A, 810B each define an axial edge of counter electrode 832A. Subsequent to depositing pillars 810, one or more etch or photolithographic processes may be employed to form the final geometry of pillars 810. Pillars 810 may be selectively deposited in relatively small areas on substrate 802 where pillars 810 may function as anchor points which reduce or eliminate delamination of subsequently applied layers. For example, pillar 810 may define an axial length of less than about 20%, or less than about 10% of the axial length of counter electrode 832 A.

[0116] Counter electrode 832A may be deposited on substrate 802 in a pattern (1304). The pattern may include void areas and / or a non-uniform thickness when measured perpendicular to substrate 802. In some examples, counter electrode 832A may cover less than all of substrate 802, and thus may cover less than all of base layer 804. In examples where void areas are included, another electrode may be disposed on back side 843 of base layer 804 by depositing another portion of the metal composition of counter electrode 832A, or another metal composition, onto substrate 802. In some examples, subsequent to depositing the metal composition of counter electrode 832A, bond layer 820 may be deposited on all or part of counter electrode 832A. Bond layer 820 may include a metal composition which includes titanium.DocketNo.: A0011989W001 / 1277-126W001

[0117] Base layer 804 may be applied on substrate 802 over counter electrode 832A. (1306). Base layer 804 may include a polymer layer (such as, but not limited to, a polyimide). In some examples, applying base layer 804 may include spin casting the polymer (e.g., polyimide) onto back side counter electrode 832A, then pre-curing the polymer (e.g., polyimide).

[0118] Base layer 804 may optionally be patterned and / or etched for deposition of one or more electrodes including counter electrode 832B, reference electrode 836, and working electrode 834, and / or one or more contact pads 814. In one or more examples, the patterning comprises depositing a dry-etch mask (e.g., photoresist dry etch mask) on base layer 804, dry etching base layer 804 through openings in the dry-etch mask, and stripping the dry-etch mask from base layer 804 thereby forming an etched pattern in the base layer 804.

[0119] In some examples, the metal composition of sensor traces 822 may be deposited into the etched pattern (1308). Examples of the metal composition of sensor traces 822 may include gold, silver, copper, platinum, or the like. In one or more examples, depositing sensor traces 822 may include sputtering or electron beam depositing the metal composition onto base layer 804. Further processing may include depositing a mask (e.g., photoresist wet-etch mask) on sensor traces 822; etching (e.g., wet etching) the metal through openings in the mask; and stripping the mask from the sensor traces 822.

[0120] Insulation layer 812 may be applied on base layer 804 and subsequently applied metals (1310). Insulation layer 812 may include a polymer layer, such as, but not limited to, a polyimide layer. In some examples, different types of polyimide may be applied as base layer 804 and insulation layer 812. In some examples, insulation layer 812 may be applied by spin casting insulation layer 812 onto base layer 804. Insulation layer 812 may be pre-cured, and may be patterned using photolithography to form openings 811 A, 81 IB, 811C. Prior to patterning insulation layer 812, the technique of FIG. 13 may include depositing the metal composition of front side counter electrode 832B (1312). In other examples, insulation 812 may be broken up into two or more insulation sub-layers. The metal composition of counter electrode 832B may be deposited after a first insulation sub-layer, and followed by deposition of a second insulation sublayer. In some examples, the metal composition may include a platinum catalyst. Sensor flex internals 860 may be cured (1316). Optionally, residue may be removed from insulation layer 812 or other components, for example using oxygen gas (1318).

[0121] Metal composition 833 of working electrode 834 may be deposited onto base layer 804 (1320). Examples of metal composition 833 may include any of the metals described with respect to counter electrode 832A. In one or more examples, metal composition 833 may be deposited by sputtering / e-beam depositing a film (e.g., thin film) of metal composition 833 to base layer 804 to blanket a portion of base layer 804; depositing a mask (e.g., photoresist wet-Docket No.: A0011989W001 / 1277-126W001 etch mask) on metal composition 833 sputtered onto base layer 804; etching (e.g., wet etching) the metal through openings in the mask; and stripping the mask.

[0122] In some examples, another metal composition of working electrode 834 may be deposited (1322). In some examples, another layer of metal composition 833 may be deposited, or one or more pillars 810 may be deposited in a well of working electrode 834 may be deposited. The metal composition of reference electrode 836 may be deposited (1324). In some examples, the metal composition of reference electrode 836 may include silver / silver-chloride. In some examples, analyte sensing layer 835 may be applied to working electrode 834 (1326).Application of analyte sensor layer 835 may ensure that working electrode 834 has the proper functionality in a glucose sensor.

[0123] Sensor flex internals 860 may be defined by cutting or laser patterning base layer 804 with the deposited metal compositions (1328). Sensor flex internals 860 may be removed (e.g., peeled) from substrate 802 (1330). In one or more embodiments, the techniques, materials, and arrangements disclosed herein may reduce the frequency or severity of delamination of sensor flex internals 860 during this step. Sensor flex internals 860 of sensor flex 840 of monitor 800 may result (1332). Sensor flex internals 860 may be included in sensor flex 840 for insertion into a patient (112, FIG. 1).

[0124] The following describes examples that may be used alone or in combination.

[0125] Example 1 : A device includes a monitor includes a sensor flex extending from a first axial end to a second axial end, the sensor flex defining a front side and a back side opposite the front side; a first electrode disposed on the front side of the sensor flex; and a second electrode disposed on the back side of the sensor flex, wherein the first electrode and the second electrode form an electrode pair configured to react to the analyte and generate the electrical signal in response to the reaction, and wherein the second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

[0126] Example 2: The device of example 1, wherein the second electrode defines a non-uniform thickness.

[0127] Example 3: The device of example 1 or example 2, wherein the second electrode comprises at least one of gold, silver, platinum, or copper.

[0128] Example 4: The device of any of examples 1-3, wherein: the sensor flex houses a base layer extending from a connection portion adjacent to the first axial end of the sensor flex and a sensing portion disposed adjacent to the second axial end of the sensor flex, the base layer is disposed between the first electrode and the second electrode, and the base layer defines a front side facing the front side of the sensor flex and a back side facing the back side of the sensor flex.Docket No.: A0011989W001 / 1277-126W001

[0129] Example 5: The device of example 4, wherein the base layer comprises a chemicalresistant, dimensionally-stable, and electrically-insulative polymeric material.

[0130] Example 6: The device of example 5, wherein the polymeric material is polyimide.

[0131] Example 7: The device of any of examples 4-6, further comprising an insulation layer disposed adjacent to the base layer.

[0132] Example 8: The device of any of examples 4-7, wherein the insulation layer comprises a different chemical-resistant, dimensionally-stable, and electrically-insulative polymeric material than the base layer.

[0133] Example 9: The device of any of examples 4-8, further comprising one or more pillars disposed on the back side of the base layer, the one or more pillars configured to reduce or eliminate delamination of the second electrode from the base layer during fabrication or operation of the device.

[0134] Example 10: The device of example 9, wherein at least one of the one or more pillars is disposed at an interface of the second electrode and the base layer.

[0135] Example 11 : The device of any of examples 9 or 10, wherein at least one of the one or more pillars defines an axial edge of the second electrode.

[0136] Example 12: The device of any of examples 9-11, wherein at least one of the one or more pillars defines a pillar thickness of between about 1 micrometer and about 5 micrometers.

[0137] Example 13: The device of any of examples 9-12, wherein at least one of the one or more pillars comprises titanium.

[0138] Example 14: The device of any of examples 4-13, further comprising a bond layer disposed between the second electrode and the base layer.

[0139] Example 15: The device of example 14, wherein the bond layer comprises titanium.

[0140] Example 16: The device of any of examples 4-15, further comprising a hardmask material disposed on the back side of the base layer.

[0141] Example 17: The device of example 16, wherein the hardmask material comprises at least one of a titanium nitride, a tantalum nitride, or an amorphous carbon.

[0142] Example 18: The device of any of examples 1-17, further comprising a third electrode, wherein the third electrode is displaced from the second electrode and disposed on the back side of the sensor flex.

[0143] Example 19: The device of example 18, further comprising a fourth electrode, wherein the fourth electrode is displaced from the third electrode and the second electrode and disposed on the back side of the sensor flex.

[0144] Example 20: The device of any of examples 1-19, wherein the sensor is a first sensor includes a second sensor disposed on the sensor flex, the second sensor includes a secondDocket No.: A0011989W001 / 1277-126W001 working electrode displaced from the first working electrode and disposed on the front side of the sensor flex; and a second counter electrode displaced from the first counter electrode on the back side of the sensor flex.

[0145] Example 21 : The device of example 20, wherein the second sensor is configured to sense a different analyte than the first sensor.

[0146] Example 22: The device of example 20 or example 21, further includes a third working electrode displaced from the first working electrode and the second working electrode disposed on the front side of the sensor flex; and a third counter electrode displaced from the first counter electrode and the second counter electrode on the back side of the sensor flex.

[0147] Example 23 : A method for fabricating a sensor of a medical device includes fabricating a sensor flex extending from a first axial end to a second axial end, the sensor flex defining front side and a back side opposite the front side: positioning a first electrode on the front side of the sensor flex; and positioning a second electrode on the back side of the sensor flex, wherein the second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

[0148] Example 24: The method of example 23, further comprising a method for performing techniques of any of examples 2-22.

[0149] Example 25: A method includes reacting an electrode pair which includes a first electrode and a second electrode with an analyte of a patient, wherein: the electrode pair is part of a sensor, the sensor includes a sensor flex extending from a first axial end to a second axial end, the sensor flex defining a front side and a back side opposite the front side, the sensor is part of a monitor, the first electrode is disposed on the front side of the sensor flex and the second electrode is disposed on the back side of the sensor flex, and the second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex, generating an electrical signal indicative of an analyte level of the analyte between the first electrode and the second electrode in response to the reaction with the analyte, and outputting, from the sensor, an electrical signal indicative of the analyte level of the analyte of the patient.

[0150] Example 26: A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, configure a processor to: react an electrode pair which includes a first electrode and a second electrode with an analyte of a patient, wherein: the electrode pair is part of a sensor, the sensor includes a sensor flex extending from a first axial end to a second axial end, the sensor flex defines a front side and a back side opposite the front side the sensor is part of a monitor, the first electrode is disposed on the front side of the sensor flex and the second electrode is disposed on the back side of the sensor flex, and the second electrodeDocket No.: A0011989W001 / 1277-126W001 defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex, generate an electrical signal indicative of an analyte level of the analyte between the first electrode and the second electrode in response to the reaction with the analyte, and output, from the sensor, an electrical signal indicative of the analyte level of the analyte of the patient.

[0151] Example 27: A method for manufacturing an analyte sensing apparatus includes depositing a back side electrode in a pattern on a substrate, the back side electrode having a first metal composition having an electroactive surface; applying a base layer to the back side electrode, the base layer defining a first side facing away from the back side electrode and a second side adjacent to the back side electrode, and depositing a front side electrode on the first side of the base layer, the front side electrode having a second metal composition having an electroactive surface.

[0152] Example 28: The method of example 27, further comprising applying an analyte sensing layer on the front side electrode, wherein the analyte sensing layer detectably alters electrical current at the front side electrode in a presence of an analyte.

[0153] Example 29: The method of example 27 or example 28, further includes electrically connecting a first contact pad of the connection portion to the back side electrode, and electrically connecting a second contact pad of the connection portion to the front side electrode.

[0154] Example 30: The method of any of examples 27-29, further comprising peeling, subsequent to at least depositing the back side electrode in a pattern on the substrate and applying the base layer to the back side electrode, the base layer from the substrate.

[0155] Example 31 : The method of any of examples 27-30, wherein depositing the counter electrode in a pattern comprises forming one or more void areas such that the back side electrode covers less than all of the substrate.

[0156] Example 32: The method of any of examples 27-31, wherein depositing the back side electrode in a pattern comprises depositing a non-uniform thickness of the first metal composition.

[0157] Example 33: The method of any of examples 27-32, further comprising, prior to depositing the back side electrode, depositing one or more pillars, the one or more pillars configured to reduce or eliminate delamination of the back side electrode from the base layer when the base layer is removed from the substrate.

[0158] Example 34: The method of example 33, wherein the one or more pillars includes at least one pillar deposited at an axial edge of the back side electrode.Docket No.: A0011989W001 / 1277-126W001

[0159] Example 35: The method of any of examples 27-34, wherein the back side electrode is a first back side electrode, and wherein the method further comprises: depositing a second back side electrode on the substrate displaced from the first back side electrode.

[0160] Example 36: The method of example 35, further comprising depositing a third back side electrode on the substrate displaced from the first back side electrode and the second back side electrode

[0161] The techniques described in this disclosure may also be embodied or encoded in a computer-readable medium, such as a computer-readable storage medium, containing instructions. Instructions embedded or encoded in a computer-readable medium may cause a programmable processor, or other processor, to perform the method, e.g., when the instructions are executed. Computer-readable media may include non-transitory computer-readable storage media and transient communication media. Computer readable storage media, which is tangible and non-transitory, may include random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, magnetic media, optical media, or other computer-readable storage media. It should be understood that the term “computer-readable storage media” refers to physical storage media, and not signals, carrier waves, or other transient media.

[0162] Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, modules or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0163] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

Docket No.: A0011989W001 / 1277-126W001 WHAT IS CLAIMED IS:

1. A device comprising:a monitor comprising at least one sensor configured to sense an electrical signal indicative of an analyte level of an analyte of a patient, wherein the sensor comprises:a sensor flex extending from a first axial end to a second axial end, the sensor flex defining a front side and a back side opposite the front side;a first electrode disposed on the front side of the sensor flex; anda second electrode disposed on the back side of the sensor flex,wherein the first electrode and the second electrode form an electrode pair configured to react to the analyte and generate the electrical signal in response to the reaction, and wherein the second electrode defines a pattern such that the second electrode covers less than all of the surface area on the back side of the sensor flex.

2. The device of claim 1, wherein the second electrode defines a non-uniform thickness.

3. The device of claim 1 or claim 2, wherein the second electrode comprises at least one of gold, silver, platinum, or copper.

4. The device of any of claims 1-3, wherein:the sensor flex houses a base layer extending from a connection portion adjacent to the first axial end of the sensor flex and a sensing portion disposed adjacent to the second axial end of the sensor flex,the base layer is disposed between the first electrode and the second electrode, and the base layer defines a front side facing the front side of the sensor flex and a back side facing the back side of the sensor flex.

5. The device of claim 4, wherein the base layer comprises a chemical-resistant, dimensionally-stable, and electrically-insulative polymeric material.

6. The device of claim 5, wherein the polymeric material is polyimide.

7. The device of any of claims 4-6, further comprising an insulation layer disposed adjacent to the base layer.Docket No.: A0011989W001 / 1277-126W001 8. The device of any of claims 4-7, wherein the insulation layer comprises a different chemi cal -resistant, dimensionally-stable, and electrically-insulative polymeric material than the base layer.

9. The device of any of claims 4-8, further comprising one or more pillars disposed on the back side of the base layer, the one or more pillars configured to reduce or eliminate delamination of the second electrode from the base layer during fabrication or operation of the device.

10. The device of claim 9, wherein at least one of the one or more pillars is disposed at an interface of the second electrode and the base layer.

11. The device of any of claims 9 or 10, wherein at least one of the one or more pillars defines an axial edge of the second electrode.

12. The device of any of claims 9-11, wherein at least one of the one or more pillars defines a pillar thickness of between about 1 micrometer and about 5 micrometers.

13. The device of any of claims 9-12, wherein at least one of the one or more pillars comprises titanium.

14. The device of any of claims 4-13, further comprising a bond layer disposed between the second electrode and the base layer.

15. The device of any of claims 1-14, further comprising a third electrode,wherein the third electrode is displaced from the second electrode and disposed on the back side of the sensor flex.

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