Singulated wire sensor with improved response

Abstract

A device includes a first conductive layer comprising a working electrode, wherein the working electrode is configured to generate a signal indicative of the concentration. The device further includes a second conductive layer comprising a reference electrode and / or a counter electrode, a distal tip comprising an exposed portion of the first conductive layer and the second conductive layer and characterized by anon-planer surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis, and an electrically insulating material covering the at least a portion of distal tip, wherein the analyte sensor has a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding analyte sensor differing only in that a distal tip of the corresponding analyte sensor is free of electrically insulating material.

Description

SINGULATED WIRE SENSOR WITH IMPROVED RESPONSECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Senal No. 63 / 738.949 entitled “SINGULATED WIRE SENSOR WITH IMPROVED RESPONSE,” filed December 26, 2024, the disclosure of which is incorporated herein in its entirety by reference.BACKGROUND

[0002] Diabetes is a metabolic condition relating to the production or use of insulin by the body. Insulin is a hormone that allows the body to use glucose for energy, or store glucose as fat.

[0003] When a person eats a meal that contains carbohydrates, the food is processed by the digestive system, which produces glucose in the person’s blood. Blood glucose can be used for energy or stored as fat. The body normally maintains blood glucose levels in a range that provides sufficient energy to support bodily functions and avoids problems that can arise when glucose levels are too high, or too low. Regulation of blood glucose levels depends on the production and use of insulin, which regulates the movement of blood glucose into cells.

[0004] When the body does not produce enough insulin, or when the body is unable to effectively use insulin that is present, blood sugar levels can elevate beyond normal ranges. The state of having a higher than normal blood sugar level is called “hyperglycemia.” Chronic hyperglycemia can lead to a number of health problems, such as cardiovascular disease, cataract and other eye problems, nerve damage (neuropathy), and kidney damage. Hyperglycemia can also lead to acute problems, such as diabetic ketoacidosis - a state in which the body becomes excessively acidic due to the presence of blood glucose and ketones, which are produced when the body cannot use glucose. The state of having lower than normal blood glucose levels is called “hypoglycemia.” Severe hypoglycemia can lead to acute crises that can result in seizures or death.Atty. Dkt. No. 4855.148 WO 1 1 Client Reference No. 0966-PCT01

[0005] A diabetes patient can receive insulin to manage blood glucose levels. Insulin can be received, for example, through a manual injection with a needle. Wearable insulin pumps are also available. Diet and exercise also affect blood glucose levels. A glucose sensor can provide an estimated glucose concentration level, which can be used as guidance by a patient or caregiver.

[0006] Diabetes conditions are sometimes referred to as ‘‘Type 1” and ‘"Type 2.” A Type 1 diabetes patient is typically able to use insulin when it is present, but the body is unable to produce sufficient amounts of insulin, because of a problem with the insulin-producing beta cells of the pancreas. A Type 2 diabetes patient may produce some insulin, but the patient has become “insulin resistant” due to a reduced sensitivity to insulin. The result is that even though insulin is present in the body, the insulin is not sufficiently used by the patient’s body to effectively regulate blood sugar levels.

[0007] Blood sugar concentration levels may be monitored with an analyte sensor, such as a continuous glucose monitor. A continuous glucose monitor is used by a host (e.g., patient) to provide information, such as an estimated blood glucose value or a trend of estimated blood glucose levels.SUMMARY

[0008] In some aspects, the techniques described herein relate to an analyte sensor configured for insertion into a host for measuring a concentration of an analyte in the host, the analyte sensor including: a first conductive layer including a working electrode, wherein the working electrode is configured to generate a signal indicative of the concentration; a second conductive layer including a reference electrode and / or a counter electrode, the first conductive layer and the second conductive layer being substantially coaxial along a longitudinal axis, a distal tip including an exposed portion of the first conductive layer and the second conductive layer and characterized by a non-planer surface including at least one projection extending from a plane perpendicular to the longitudinal axis, and an electrically insulating material covering the atAtty. Dkt. No. 4855.148 WO 1 2 Client Reference No. 0966-PCT01least a portion of distal tip, wherein the analyte sensor has a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding analyte sensor differing in that a distal tip of the corresponding analyte sensor is free of electrically insulating material.

[0009] In some aspects, the techniques described herein relate to a method of forming a tip passivation layer on an analyte sensor, the method including: contacting a distal tip of an analytical sensor with a passivation material; and removing the distal tip of the analytical sensor from contact with the passivation material after the analytical sensor has traveled a predetermined distance.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments described in the present document.

[0011] FIG. 1 is a diagram showing one example of an environment including an analyte sensor system.

[0012] FIG. 2 is a schematic illustration of an example analyte sensor system, which may for example, be the system shown in FIG. 1.

[0013] FIG. 3 is a diagram showing one example of a medical device system including the analyte sensor system of FIG. 1.

[0014] FIG. 4 is an illustration of an example analyte sensor.

[0015] FIG. 5 is an illustration of another example analy te sensor.

[0016] FIG. 6 is an enlarged view of an example analyte sensor portion.

[0017] FIG. 7 is a cross-sectional view of the analyte sensor of FIGS. 4-6.

[0018] FIG. 8 is a perspective view of a distal tip of the analyte sensor of FIGS.4-7.

[0019] FIG. 9 is a schematic illustration of the analyte sensor of FIGS. 4-8 including an electrically insulating material disposed over the distal tip.Atty. Dkt. No. 4855.148 WO 1 3 Client Reference No. 0966-PCT01

[0020] FIG. 10 is a perspective view of an assembly for applying an electrically insulating material to the distal tip.

[0021] FIG. 11 is a schematic illustration of a circuit that represents the behavior of an example analyte sensor.

[0022] FIG. 12 is a perspective view of a test analyte sensor.

[0023] FIG. 13 is a graph showing signal generation for series of test analyte sensors with ant without capped distal tips.DETAILED DESCRIPTION

[0024] Various examples described herein are directed to analyte sensor systems and methods for using analyte sensor systems. An analyte sensor system includes an analyte sensor that is placed in contact with a bodily fluid of a host to measure a concentration of an analyte, such as glucose, in the bodily fluid. In some examples, the analyte sensor is inserted into the host to contact the bodily fluid in vivo. In some examples, the analyte sensor is inserted subcutaneously to contact interstitial fluid below the host’s skin.

[0025] When the analyte sensor is exposed to analyte in the host’s bodily fluid, an electrochemical reaction between the analyte sensor and the analyte causes the analyte sensor to generate a raw sensor signal that is indicative of the analyte concentration in the bodily fluid. For example, the analyte sensor may include two or more electrodes.

[0026] FIG. 1 is a diagram showing one example of an environment 100 including an analyte sensor system 102. The analyte sensor system 102 is coupled to a host 101, which may be a human patient. In some examples, the host is subject to a temporary or permanent diabetes condition or other health condition that makes analyte monitoring useful.

[0027] The analyte sensor system 102 includes an analyte sensor 104. In some examples, the analyte sensor 104 is or includes a glucose sensor configured to measure a glucose concentration in the host 101. The analyte sensor 104 can be exposed to analyte at the host 101 in any suitable way. In some examples, the analyte sensor 104 is fully implantable under the skin of the host 101. In other examples, the analyte sensor 104 is wearable on the body of the host 101 (e.g., on the body butAtty. Dkt. No. 4855.148 WO 1 4 Client Reference No. 0966-PCT01not under the skin). Also, in some examples, the analyte sensor 104 is a transcutaneous device (e.g., with a sensor residing at least partially under or in the skin of a host). It should be understood that the devices and methods described herein can be applied to any device capable of detecting a concentration of an analyte, such as glucose, and providing an output signal that represents the concentration of the analyte.

[0028] In the example of FIG. I, the analyte sensor system 102 also includes sensor electronics 106. In some examples, the sensor electronics 106 and analyte sensor 104 are provided in a single integrated enclosure (See FIG.4). In other examples, the analyte sensor 104 and sensor electronics 106 are provided as separate components or modules (See FIG. 5). For example, the analyte sensor system 102 may include a disposable (e.g., single-use) sensor mounting unit that may include the analyte sensor 104, a component for attaching the sensor 104 to a host (e.g., an adhesive pad), and / or a mounting structure configured to receive a sensor electronics unit including some or all of the sensor electronics 106 shown in FIGS.2 and 3. The sensor electronics 106 may be reusable.

[0029] The analyte sensor 104 may use any known method, including invasive, minimally-invasive, or non-invasive sensing techniques (e.g., optically excited fluorescence, microneedle, transdermal monitoring of glucose), to provide a raw sensor signal indicative of the concentration of the analyte in the host 101. The raw sensor signal may be converted into calibrated and / or filtered analyte concentration data used to provide a useful value of the analyte concentration (e.g., estimated blood glucose concentration level) to a user, such as the host or a caretaker (e.g., a parent, a relative, a guardian, a teacher, a doctor, a nurse, or any other individual that has an interest in the wellbeing of the host 101).

[0030] In some examples, the analyte sensor 104 is or includes a continuous glucose sensor. A continuous glucose sensor can be or include a subcutaneous, transdermal (e.g., transcutaneous), and / or intravascular device. In some embodiments, such a sensor or device may recurrently (e.g.. periodically, or intermittently) analyze sensor data. The glucose sensor may use any method of glucose measurement, including enzymatic, chemical, physical, electrochemical, spectrophotometric,Atty. Dkt. No. 4855.148 WO 1 5 Client Reference No. 0966-PCT01polarimetric, calorimetric, iontophoretic, radiometric, immunochemical, and the like. In various examples, the analyte sensor system 102 may be or include a continuous glucose monitor sensor available from DexCom™, (e.g., the DexCom G5™ sensor, Dexcom G6™ sensor, the DexCom G7™ sensor, or any variation thereof), from Abbott™ (e.g., the Libre™ sensor), or from Medtronic™ (e.g., the Enlite™ sensor).

[0031] In some examples, analyte sensor 104 includes an implantable glucose sensor, such as described with reference to U.S. Patent 6,001,067 and U.S. Patent Publication No. US-2005-0027463-A1, which are incorporated by reference. In some examples, analyte sensor 104 includes a transcutaneous glucose sensor, such as described with reference to U.S. Patent Publication No. US-2006-0020187-Al, which is incorporated by reference. In some examples, analyte sensor 104 may be configured to be implanted in a host vessel or extracorporeally, such as is described in U.S. Patent Publication No. US-2007-0027385-A1, copending U.S. Patent Publication No. US-2008-0119703-Al filed October 4, 2006, U.S. Patent Publication No. US-2008-0108942-Al filed on March 26, 2007, and U.S. Patent Application No. US-2007-0197890-A1 filed on February 14, 2007, all of which are incorporated by reference. In some examples, the continuous glucose sensor may include a transcutaneous sensor such as described in U.S. Patent 6,565,509 to Say et al., which is incorporated by reference. In some examples, analyte sensor 104 may include a continuous glucose sensor that includes a subcutaneous sensor such as described with reference to U.S. Patent 6,579,690 to Bonnecaze et al. or U.S. Patent 6,484,046 to Say et al., which are incorporated by reference. In some examples, the continuous glucose sensor may include a refillable subcutaneous sensor such as described with reference to U.S. Patent 6,512,939 to Colvin et al., which is incorporated by reference. The continuous glucose sensor may include an intravascular sensor such as described with reference to U.S. Patent 6,477,395 to Schulman et al., which is incorporated by reference. The continuous glucose sensor may include an intravascular sensor such as described with reference to U.S. Patent 6.424,847 to Mastrototaro et al., which is incorporated by reference.Atty. Dkt. No. 4855.148 WO 1 6 Client Reference No. 0966-PCT01

[0032] The environment 100 may also include various other external devices including, for example, a medical device 108. The medical device 108 may be or include a drug delivery device such as an insulin pump or an insulin pen. In some examples, the medical device 108 includes one or more sensors, such as another analyte sensor, a heart rate sensor, a respiration sensor, a motion sensor (e.g., accelerometer), posture sensor (e.g., 3-axis accelerometer), acoustic sensor (e.g., to capture ambient sound or sounds inside the body). The medical device 108 may be wearable, e.g., on a watch, glasses, contact lens, patch, wristband, ankle band, or another wearable item, or may be incorporated into a handheld device (e.g.. a smartphone). In some examples, the medical device 108 includes a multi-sensor patch that may, for example, detect one or more of an analyte levels (e.g., glucose, lactate, insulin, or other substance), heart rate, respiration (e.g., using impedance), activity (e.g., using an accelerometer), posture (e.g., using an accelerometer), galvanic skin response, tissue fluid levels (e.g.. using impedance or pressure).

[0033] In some examples, the analyte sensor system 102 and the medical device 108 communicate with one another. Communication between the analyte sensor system 102 and medical device 108 may occur over any suitable wired connection and / or via a wireless communication signal 110. For example, the analyte sensor system 102 (e g., the sensor electronics 106 thereof) may be configured to establish a communication connection with the medical device 108 using a suitable short-range communications medium such as. for example, a radio frequency medium (e.g., Bluetooth, Medical Implant Communication System (MICS), Wi-Fi, near field communication (NFC), radio frequency identification (RFID), Zigbee, Z-Wave or other communication protocols), an optical medium (e.g., infrared), a sonic medium (e.g., ultrasonic), a cellular protocol-based medium (e.g.. Code Division Multiple Access (CDMA) or Global System for Mobiles (GSM)), and / or the like.

[0034] In some examples, the environment 100 also includes other external devices such as, for example, awearable sensor 130. The wearable sensor 130 can include a sensor circuit (e.g., a sensor circuit configured to detect a glucose concentration or other analyte concentration) and aAtty. Dkt. No. 4855.148 WO 1 7 Client Reference No. 0966-PCT01communication circuit, which may, for example, be an NFC circuit. In some examples, information from the wearable sensor 130 may be retrieved from the wearable sensor 130 using a user computing device 132, such as a smart phone, that is configured to communicate with the wearable sensor 130 via the wearable sensor’s communication circuit, for example, when the user device 132 is placed near the wearable sensor 130. For example, swiping the user device 132 over the sensor 130 may retrieve sensor data from the wearable sensor 130 using NFC or other suitable wireless communication.

[0035] The use of NFC communication may reduce power consumption by the wearable sensor 130, which may reduce the size of a power source (e.g., battery' or capacitor) in the wearable sensor 130 or extend the usable life of the power source. In some examples, the wearable sensor 130 may be wearable on an upper arm as shown. In some examples, a wearable sensor 130 may additionally or alternatively be on the upper torso of the patient (e.g., over the heart or over a lung), which may, for example, facilitate detecting heart rate, respiration, or posture. A wearable sensor 136 may also be on the lower body (e.g., on a leg) or other part of the body (e.g., on the abdomen).

[0036] In some examples, an array or network of sensors may be associated with the patient. For example, one or more of the analyte sensor system 102, and / or external devices, such as the medical device 108, wearable device 120 such as a watch, an additional wearable sensor 130 and / or the like, may communicate with one another via a short-range communication medium (e.g., Bluetooth, MICS, NFC, or any of the other options described above,). The additional wearable sensor 130 may be any of the examples described above with respect to medical device 108. The analyte sensor system 102, medical device 108, and additional sensor 130 on the host 101 are provided for illustration and description and are not necessarily drawn to scale.

[0037] The environment 100 may also include one or more other external devices such as a hand-held smart device (e.g., smart phone) 112, tablet 114, smart pen 116 (e.g., insulin delivery pen with processing and communication capability), computer 118, a wearable device 120 suchAtty. Dkt. No. 4855.148 WO 1 8 Client Reference No. 0966-PCT01as a watch, or peripheral medical device 122 (which may be a proprietary device such as a proprietary user device available from DexCom™), any of which may communicate with the analyte sensor system 102 via a short-range communication medium, such as indicated by wireless communication signal 110, and may also communicate over a network 124 with a server system (e.g., remote data center) or with a remote terminal 128 to facilitate communication with a remote user (not shown) such as a technical support staff member or a clinician.

[0038] The wearable device 120 may include an activity' sensor, a heart rate monitor (e g., light-based sensor or electrode-based sensor), a respiration sensor (e.g., acoustic- or electrode-based), a location sensor (e.g., GPS), or other sensors.

[0039] In some examples, the environment 100 includes a sen- er system 126.The ser er system 126 can include one or more computing devices, such as one or more server computing devices. In some examples, the server system 126 is used to collect analyte data from the analyte sensor system 102 and / or analyte or other data from the plurality of other devices, and to perform analytics on collected data, generate, or apply universal or individualized models for glucose levels, and communicate such analytics, models, or information based thereon back to one or more of the devices in the environment 100. In some examples, the server system 126 gathers inter-host and / or intra-host break-in data to generate one or more break-in characteristics, as described herein.

[0040] The environment 100 may also include a wireless access point (WAP) 138 used to communicatively couple one or more of analyte sensor system 102, network 124, server system 126, medical device 108 or any of the peripheral devices described above. For example, WAP 138 may- pro vide Wi-Fi and / or cellular connectivity within environment 100. Other communication protocols, such as NFC or Bluetooth, may also be used among devices of the environment 100.

[0041] FIG. 2 is a schematic illustration of an example analyte sensor system 200, which may for example, be the system 102 shown in FIG. 1. The analyte sensor system may include an analyte sensor 202. The analyte sensor 202 may be configured to measure glucose or another suitableAtty. Dkt. No. 4855.148 WO 1 9 Client Reference No. 0966-PCT01analyte. The analyte sensor system 200 may also comprise one or more temperature sensors 204. a processor 210, and a memory 206. The processor 210 may receive a signal indicative of an analyte concentration level from the analyte sensor 202 and receive a temperature signal indicative of a temperature parameter (e.g. absolute or relative temperature, or a temperature gradient) from the temperature sensor 204. The signal indicative of the analyte concentration may be a raw sensor signal or a processed sensor signal. The sensor system 200 may also include one or more additional sensors 208, which may include, for example, a heart rate sensor, activity sensor (e.g. accelerometer), or a pressure gauge (e.g. to measure compression of the sensor against a host).

[0042] The processor 210 may determine a temperature-compensated analyte concentration level based on the temperature sensor signal and optionally also based on one or more signals from additional sensor(s) 208. The processor 210 may determine a specific temperature-compensated sensitivity value (e.g., analyte sensor sensitivity value based on the temperature), or may determine a compensated estimated glucose value. The signal from the temperature sensor 204 may be used as an approximation of a temperature at an analyte sensor, or the signal from the temperature sensor 204 may be processed (e.g., using methods described in detail below) to determine an estimated analyte temperature sensor based on the signal from the temperature sensor 204.

[0043] In some examples, the processor 210 may retrieve instructions or information from a memory 206 to determine temperature-compensated analyte concentration level. For example, the processor may access a look-up table, or apply an algorithm based on the signal indicative of analyte concentration and temperature sensor signal or apply the signal indicative of analyte concentration and temperature signal to a model (e.g., use a state model or neural network).

[0044] In some examples, the processor may retrieve executable instructions from the memory 206 (or a separate memory that may be operatively coupled to or integrated into the processor.) In some examples, the processor may include, or be part of. an application-specific integrated circuit (ASIC) that may be configured to determine a temperature-Atty. Dkt. No. 4855.148 WO 1 10 Client Reference No. 0966-PCT01compensated glucose concentration level. In various examples, any one or more of the methods described herein may be executed by the processor 210 or temperature-compensated glucose sensor, either alone, or in combination with other processors or devices.

[0045] FIG. 3 is a diagram showing one example of a medical device system 300 including the analyte sensor system 102 of FIG. 1. In the example of FIG. 3, the analyte sensor system 102 includes sensor electronics 106 and an example sensor mounting unit 390, although in some examples, it will be appreciated that the analyte sensor 104 and sensor electronics 106 may be included in a common enclosure. While a specific example of division of components between the sensor mounting unit 390 and sensor electronics 106 is shown, it is understood that some examples may include additional components in the sensor mounting unit 390 or in the sensor electronics 106, and that some of the components (e.g., a battery or supercapacitor) that are shown in the sensor electronics 106 may be alternatively or additionally (e.g., redundantly) provided in the sensor mounting unit 390.

[0046] In the example shown in FIG. 3, the sensor mounting unit 390 includes the analyte sensor 104 and a battery 392. In some examples, the sensor mounting unit 390 may be replaceable, and the sensor electronics 106 may include a debouncing circuit (e.g., gate with hysteresis or delay) to avoid, for example, recurrent execution of a power-up or power down process when a battery is repeatedly connected and disconnected or avoid processing of noise signal associated with removal or replacement of a battery.

[0047] The sensor electronics 106 may include electronics components that are configured to process sensor information, such as raw sensor signals, and generate corresponding analyte concentration values. The sensor electronics 106 may, for example, include electronic circuitry associated with measuring, processing, storing, or communicating continuous analyte sensor data, including prospective algorithms associated with processing and calibration of the raw' sensor signal. The sensor electronics 106 may include hardware, firmware, and / or software that enables measurement of levels of the analyte via a glucose sensor.Atty. Dkt. No. 4855.148 WO 1 11 Client Reference No. 0966-PCT01Electronic components may be affixed to a printed circuit board (PCB), or the like, and can take a variety of forms. For example, the electronic components may take the form of an integrated circuit (IC), such as an Application-Specific Integrated Circuit (ASIC), a microcontroller, and / or a processor.

[0048] In the example of FIG. 3. the sensor electronics 106 include a measurement circuit 302 (e.g., potentiostat) coupled to the analyte sensor 104 and configured to recurrently obtain analyte sensor readings using the analyte sensor 104. For example, the measurement circuit 302 may continuously or recurrently sample a raw sensor signal indicating a current flow at the analyte sensor 104 between a working electrode and a reference electrode. The sensor electronics 106 may include a gate circuit 394, which may be used to gate the connection between the measurement circuit 302 and the analyte sensor 104. For example, the analyte sensor 104 may accumulate charge over an accumulation period. After the accumulation period, the gate circuit 394 is opened so that the measurement circuit 302 can sample the accumulated charge. Gating the analyte sensor 104 may improve the performance of the sensor system 102 by creating a larger signal to noise or interference ratio (e g., because charge accumulates from an analyte reaction, but sources of interference, such as the presence of acetaminophen near a glucose sensor, do not accumulate, or accumulate less than the charge from the analyte reaction).

[0049] The sensor electronics 106 may also include a processor 304. The processor 304 is configured to retrieve instructions 306 from memory 308 and execute the instructions 306 to control various operations in the analyte sensor system 102. For example, the processor 304 may be programmed to control application of bias potentials to the analyte sensor 104 via a potentiostat at the measurement circuit 302, interpret raw sensor signals from the analyte sensor 104, and / or compensate for environmental factors.

[0050] The processor 304 may also save information in data storage memory 310 or retrieve information from data storage memory 310. In various examples, data storage memory 310 may be integrated with memory 308,Atty. Dkt. No. 4855.148 WO 1 12 Client Reference No. 0966-PCT01or may be a separate memory circuit, such as a non-volatile memory circuit (e.g., flash RAM). Examples of systems and methods for processing sensor analyte data are described in more detail herein and in U.S. Patent Nos. 7,310,544 and 6,931,327.

[0051] The sensor electronics 106 may also include one or more sensors, such as the sensor 312, which may be coupled to the processor 304. The sensor 312 may be a temperature sensor, accelerometer, or another suitable sensor. The sensor electronics 106 may also include a power source such as a capacitor or battery 314, which may be integrated into the sensor electronics 106, or may be removable, or part of a separate electronics unit. The battery 314 (or other power storage component, e.g., capacitor) may optionally be rechargeable via a wired or wireless (e.g., inductive or ultrasound) recharging system 316. The recharging system 316 may harvest energy' or may receive energy from an external source or onboard source. In various examples, the recharge circuit may include a triboelectric charging circuit, a piezoelectric charging circuit, an RF charging circuit, a light charging circuit, an ultrasonic charging circuit, a heat charging circuit, a heat harvesting circuit, or a circuit that harvests energy from the communication circuit. In some examples, the recharging circuit may recharge the rechargeable battery using power supplied from a replaceable battery (e g., a battery supplied with a base component).

[0052] The sensor electronics 106 may also include one or more supercapacitors in the sensor electronics unit (as shown), or in the sensor mounting unit 390. For example, the supercapacitor may allow energy to be drawn from the battery' 314 in a highly consistent manner to extend the life of the battery 314. The battery' 314 may recharge the supercapacitor after the supercapacitor delivers energy to the communication circuit or to the processor 304, so that the supercapacitor is prepared for delivery of energy^ during a subsequent high-load period. In some examples, the supercapacitor may be configured in parallel with the battery' 314. A device may be configured to preferentially draw energy' from the supercapacitor, as opposed to the battery 314. In some examples, a supercapacitor may be configured to receive energy' from a rechargeableAtty. Dkt. No. 4855.148 WO 1 13 Client Reference No. 0966-PCT01batery for short-term storage and transfer energy to the rechargeable batery for long-term storage.

[0053] The supercapacitor may extend an operational life of the battery 314 by reducing the strain on the batery 314 during the high-load period. In some examples, a supercapacitor removes at least 10% of the strain off the batery during high-load events. In some examples, a supercapacitor removes at least 30% of the strain off the batery during high-load events. In some examples, a supercapacitor removes at least 30% of the strain off the batery' during high-load events. In some examples, a supercapacitor removes at least 50% of the strain off the batery during high-load events.

[0054] The sensor electronics 106 may also include a wireless communication circuit 318, which may for example include a wireless transceiver operatively coupled to an antenna. The wireless communication circuit 318 may be operatively coupled to the processor 304 and may be configured to wirelessly communicate with one or more peripheral devices or other medical devices, such as an insulin pump or smart insulin pen.

[0055] In the example of FIG. 3, the medical device system 300 also includes optional external devices including, for example, a peripheral device 350. The peripheral device 350 may be any suitable user computing device such as, for example, a wearable device (e.g., activity monitor), such as a w earable device 120. In other examples, the peripheral device 350 may be a hand-held smart device (e.g., smartphone or other device such as a proprietary handheld device available from Dexcom), a tablet 114, a smart pen 116, or special-purpose computer 118 shown in FIG. 1.

[0056] The peripheral device 350 may include a UI 352, a memory' circuit 354, a processor 356, a wireless communication circuit 358, a sensor 360, or any combination thereof. The peripheral device 350 may not necessarily include all the components shown in FIG. 3. The peripheral device 350 may also include a pow er source, such as a batery'.

[0057] The UI 352 may, for example, be provided using any suitable input / output device or devices of the peripheral device 350 such as. for example, a touch-screen interface, a microphone (e.g., to receive voiceAtty. Dkt. No. 4855.148 WO 1 14 Client Reference No. 0966-PCT01commands), or a speaker, a vibration circuit, or any combination thereof. The UI 352 may receive information from the host or another user (e.g., instructions, glucose values). The UI 352 may also deliver information to the host or other user, for example, by displaying UI elements at the UI 352. For example, UI elements can indicate glucose or other analyte concentration values, glucose or other analyte trends, glucose, or other analyte alerts, etc. Trends can be indicated by UI elements such as arrows, graphs, charts, etc.

[0058] The processor 356 may be configured to present information to a user, or receive input from a user, via the UI 352. The processor 356 may also be configured to store and retrieve information, such as communication information (e.g., pairing information or data center access information), user information, sensor data or trends, or other information in the memory circuit 354. The wireless communication circuit 358 may include a transceiver and antenna configured to communicate via a wireless protocol, such as any of the wireless protocols described herein. The sensor 360 may, for example, include an accelerometer, a temperature sensor, a location sensor, biometric sensor, or blood glucose sensor, blood pressure sensor, heart rate sensor, respiration sensor, or another physiologic sensor.

[0059] The peripheral device 350 may be configured to receive and display sensor information that may be transmitted by sensor electronics 106 (e.g., in a customized data package that is transmitted to the display devices based on their respective preferences). Sensor information (e.g., blood glucose concentration level) or an alert or notification (e.g., “high glucose level”, “low glucose level” or “fall rate alert” may be communicated via the UI 352 (e.g., via visual display, sound, or vibration). In some examples, the peripheral device 350 may be configured to display or otherwise communicate the sensor information as it is communicated from the sensor electronics 106 (e.g., in a data package that is transmitted to respective display devices). For example, the peripheral device 350 may transmit data that has been processed (e.g., an estimated analyte concentration level that may be determined by processing raw sensor data), so that a device that receives the data mayAtty. Dkt. No. 4855.148 WO 1 15 Client Reference No. 0966-PCT01not be required to further process the data to determine usable information (such as the estimated analyte concentration level). In other examples, the peripheral device 350 may process or interpret the received information (e.g., to declare an alert based on glucose values or a glucose trend). In various examples, the peripheral device 350 may receive information directly from sensor electronics 106, or over a network (e.g., via a cellular or Wi-Fi network that receives information from the sensor electronics 106 or from a device that is communicatively coupled to the sensor electronics 106).

[0060] In the example of FIG. 3, the medical device system 300 includes an optional medical device 370. For example, the medical device 370 may be an external device used in addition to or instead of the peripheral device 350. The medical device 370 may be or include any suitable type of medical or other computing device including, for example, the medical device 108, peripheral medical device 122, wearable device 120, wearable sensor 130, or wearable sensor 136 shown in FIG. 1. The medical device 370 may include a UI 372, a memory circuit 374, a processor 376, a wireless communication circuit 378, a sensor 380, a therapy circuit 382, or any combination thereof.

[0061] Similar to the UI 352, the UI 372 may be provided using any suitable input / output device or devices of the medical device 370 such as, for example, a touch-screen interface, a microphone, or a speaker, a vibration circuit, or any combination thereof. The UI 372 may receive information from the host or another user (e.g., glucose values, alert preferences, calibration coding). The UI 372 may also deliver information to the host or other user, for example, by displaying UI elements at the UI 352. For example, UI elements can indicate glucose or other analyte concentration values, glucose or other analyte trends, glucose, or other analyte alerts, etc. Trends can be indicated by UI elements such as arrows, graphs, charts, etc.

[0062] The processor 376 may be configured to present information to a user, or receive input from a user, via the UI 372. The processor 376 may also be configured to store and retrieve information, such as communication information (e.g., pairing information or data center access information),Atty. Dkt. No. 4855.148 WO 1 16 Client Reference No. 0966-PCT01user information, sensor data or trends, or other information in the memory circuit 374. The wireless communication circuit 378 may include a transceiver and antenna configured communicate via a wireless protocol, such as any of the wireless protocols described herein.

[0063] The sensor 380 may, for example, include an accelerometer, a temperature sensor, a location sensor, biometric sensor, or blood glucose sensor, blood pressure sensor, heart rate sensor, respiration sensor, or another physiologic sensor. The medical device 370 may include two or more sensors (or memories or other components), even though only one sensor 380 is shown in the example in FIG. 3. In various examples, the medical device 370 may be a smart handheld glucose sensor (e.g., blood glucose meter), drug pump (e.g., insulin pump), or other physiologic sensor device, therapy device, or combination thereof.

[0064] In examples where medical device 370 is or includes an insulin pump, the pump and analyte sensor system 102 may be in two-way communication (e.g., so the pump can request a change to an analyte transmission protocol, e.g., request a data point or request data on a more frequent schedule), or the pump and analyte sensor system 102 may communicate using one-way communication (e.g., the pump may receive analyte concentration level information from the analyte sensor system). In one-way communication, a glucose value may be incorporated in an advertisement message, which may be encrypted with a previously shared key. In a two-way communication, a pump may request a value, which the analyte sensor system 102 may share, or obtain and share, in response to the request from the pump, and any or all of these communications may be encrypted using one or more previously shared keys. An insulin pump may receive and track analyte (e.g., glucose) values transmitted from analyte sensor system 102 using one-way communication to the pump for one or more of a variety of reasons. For example, an insulin pump may suspend or activate insulin administration based on a glucose value being below or above a threshold value.

[0065] In some examples, the medical device system 300 includes two or more peripheral devices and / or medical devices that each receive information directly or indirectly from the analyte sensor system 102. BecauseAtty. Dkt. No. 4855.148 WO 1 17 Client Reference No. 0966-PCT01different display devices provide many different user interfaces, the content of the data packages (e.g.. amount, format, and / or type of data to be displayed, alarms, and the like) may be customized (e.g., programmed differently by the manufacturer and / or by an end user) for each device. For example, referring now to the example of FIG. 1, a plurality of different peripheral devices may be in direct wireless communication with sensor electronics 106 (e.g., such as an sensor electronics 106 that are on-skin and physically connected to the continuous analyte sensor 104) during a sensor session to enable a plurality' of different types and / or levels of display and / or functionality associated with the displayable sensor information, or, to save battery power in the sensor system 102, one or more specified devices may communicate with the analyte sensor system 102 and relay (i.e., share) information to other devices directly or through a server system (e.g., a network-connected data center) 126.

[0066] FIG. 4 is a side view of an example analyte sensor 434 that may be implanted into a host. An enclosure 402 may be adhered to the host’s skin using an adhesive pad 408. The adhesive pad 408 may be formed from an extensible material, which may be removably attached to the skin using an adhesive. Sensor electronics may be positioned within the enclosure 402. The sensor 434 may extend from the enclosure 402 and under the skin of a host, as shown.

[0067] FIG. 5 is a side view of another example analyte sensor 534 in an arrangement including a mounting unit 514 and an electronics unit 518. The mounting unit 514 may be adhered to the host's skin using an adhesive pad 508, which may be like the adhesive pad 408 described herein. The electronics unit 518 comprises an enclosure 502 that may have sensor electronics positioned thereon. In some examples, the electronics unit 518 and mounting unit 514 are arranged in a manner like the sensor electronics 106 and sensor mounting unit 390 shown in FIGS.1 and 4. For example, the sensor 534 may extend from the enclosure 502 via the mounting unit 514.

[0068] FIG. 6 is an enlarged view of a distal portion of an analyte sensor 634.The analyte sensor 634 illustrates one example arrangement that may be used to implement the analyte sensors described herein, such as, forAtty. Dkt. No. 4855.148 WO 1 18 Client Reference No. 0966-PCT01example, the analyte sensors 104, 434, 534. The analyte sensor 634 may be adapted for insertion under the host’s skin and may be mechanically coupled to an enclosure, such as the enclosures 502, and / or to a mounting unit 514, such as the mounting unit 514. The analyte sensor 634 may be electrically coupled to sensor electronics, which may be positioned within the enclosure 402, 502.

[0069] The example analyte sensor 634 shown in FIG. 6 includes an elongated conductive body 641. The elongated conductive body 641 can include a core 651 (show n in FIG. 7) with various layers positioned thereon. A first layer 638 that at least partially surrounds the core and includes a working electrode, for example, located in window 639). The core 651 is a metal such as tantalum, stainless steel, nickel, titanium, nitinol, or a combination thereof, clad with a material such as platinum, gold, carbon, or a combination thereof. A membrane system 632 is located over the working electrode and may cover other layers and / or electrodes of the sensor 634, as described herein.

[0070] The first layer 638 may be formed of a conductive material. The working electrode (at window' 639) is an exposed portion of the surface of the first layer 638. Accordingly, the first layer 638 is formed of a material configured to provide a suitable electroactive surface for the working electrode. Examples of suitable materials include, but are not limited to, platinum, platinum-iridium, gold, palladium, iridium, graphite, carbon, a conductive polymer, an alloy, and / or the like.

[0071] A second layer 640 surrounds at least a portion of the first layer 638, thereby defining boundaries of the working electrode. In some examples, the second layer 640 serves as an insulator and is formed of an insulating material, such as polyimide, polyurethane, parylene, or any other suitable insulating material or materials. In some examples, the second layer 640 is configured such that the working electrode (of the layer 638) is exposed via the window' 639.

[0072] In some examples, the sensor 634 further includes a third layer 643 comprising a conductive material. The third layer 643 may include a reference electrode. In some examples, the third layer 643, including the reference electrode, is formed of a silver-containing material that isAtty. Dkt. No. 4855.148 WO 1 19 Client Reference No. 0966-PCT01applied onto the second layer 640 (e.g., an insulator). The silver- containing material may include various materials and be in various forms such as, Ag / AgCl-polymer pasts, paints, polymer-based conducting mixtures, inks, etc.

[0073] The analyte sensor 634 may include two (or more) electrodes, e.g., a working electrode at the layer 638 and exposed at window 639 and at least one additional electrode, such as a reference electrode of the layer 643. In the example arrangement of FIGS. 6-7, the reference electrode also functions as a counter electrode, although other arrangements can include a separate counter electrode. While the analyte sensor 634 may be used with a mounting unit in some examples, in other examples, the analyte sensor 634 may be used with other types of sensor systems. For example, the analyte sensor 634 may be part of a system that includes a battery and sensor in a single package, and may optionally include, for example, anear-field communication (NFC) circuit.

[0074] FIG. 7 is a cross-sectional view through the sensor 634 of FIG. 6 on plane 2-2 illustrating a membrane system 632. The membrane system 632 may include a number of domains (e.g., layers). In an example, the membrane system 632 may include an enzyme domain 642, a diffusion resistance domain 644. and a bioprotective domain 646 located around the working electrode. In some examples, a unitary diffusion resistance domain and bioprotective domain may be included in the membrane system 632 (e.g., wherein the functionality of both the diffusion resistance domain and bioprotective domain are incorporated into one domain).

[0075] In some examples, the membrane system 632 also includes an electrode layer 647. The electrode layer 647 may be arranged to provide an environment between the surfaces of the working electrode and the reference electrode that facilitates the electrochemical reaction between the electrodes. For example, the electrode layer 647 may include a coating that maintains a layer of water at the electrochemically reactive surfaces of the sensor 634.

[0076] In some examples, the sensor 634 may be configured for short-term implantation (e.g.. from about 1 to 30 days). However, it is understood that the membrane system 632 can be modified for use in other devices,Atty. Dkt. No. 4855.148 WO 1 20 Client Reference No. 0966-PCT01for example, by including only one or more of the domains, or additional domains. For example, a membrane system 632 may include a plurality of resistance layers, or a plurality of enzyme layers. In some examples, the resistance domain 644 may include a plurality of resistance layers, or the enzyme domain 642 may include a plurality of enz me layers.

[0077] The diffusion resistance domain 644 may include a semipermeable membrane that controls the flux of oxygen and glucose to the underlying enzyme domain 642. As a result, the upper limit of linearity of glucose measurement is extended to a much higher value than that which is achieved without the diffusion resistance domain 644.

[0078] In some examples, the membrane system 632 may include a bioprotective domain 646, also referred to as a domain or biointerface domain, including a base polymer. However, the membrane system 632 of some examples can also include a plurality of domains or layers including, for example, an electrode domain, an interference domain, or a cell disruptive domain, such as described in more detail elsewhere herein and in U.S. Patent Nos. 7,494,465, 8,682,608, and 9,044,199, which are incorporated herein by reference in their entirety.

[0079] It is to be understood that sensing membranes modified for other sensors, for example, may include fewer or additional layers. For example, the membrane system 632 may include one electrode layer, one enzyme layer, and two bioprotective layers, but in other examples, the membrane system 632 may include one electrode layer, two enzy me layers, and one bioprotective layer. In some examples, the bioprotective layer may be configured to function as the diffusion resistance domain 644 and control the flux of the analyte (e.g., glucose) to the underlying membrane layers.

[0080] In some examples, one or more domains of the sensing membranes may¬ be formed from materials such as silicone, polytetrafluoroethylene, polyethylene-co-tetrafluoroethylene, polyolefin, polyester, polycarbonate, biostable polytetrafluoroethylene, homopolymers, copolymers, terpolymers of polyurethanes, polypropylene (PP), polyvinylchloride (PVC), poly vinylidene fluoride (PVDF), poly butylene terephthalate (PBT), polymethylmethacrylate (PMMA), polyether ether ketone (PEEK), polyurethanes, cellulosic polymers, polyethyleneAtty. Dkt. No. 4855.148 WO 1 21 Client Reference No. 0966-PCT01oxide), polypropylene oxide) and copolymers and blends thereof, poly sulfones and block copolymers thereof including, for example, diblock, tri-block, alternating, random and graft copolymers.

[0081] In some examples, the sensing membrane can be deposited on the electroactive surfaces of the electrode material using known thin or thick film techniques (for example, spraying, electro-depositing, dipping, or the like). The sensing membrane located over the working electrode does not have to have the same structure as the sensing membrane located over the reference electrode; for example, the enzyme domain 642 deposited over the working electrode does not necessarily need to be deposited over the reference or counter electrodes.

[0082] As shown, the analyte sensor 634 includes a distal tip 650. Analyte sensor 634 is formed through a singulation process. The process of singulating the analyte sensor 634 involves physically separating or isolating individual analyte sensors from a group or array of connected sensors. The process can begin with a connected array or sheet of the analyte sensors 634 and can include various mechanical separation techniques such as die cutting, laser cutting, mechanical scoring and breaking, or automated punch systems.

[0083] In some examples, the singulation process can leave the distal tip 650 with an irregular pattern. That pattern can be characterized by a nonplaner surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis. FIG. 8 is a perspective view showing the distal tip 650. As shown, singulation leaves the core 651 and the first conductive layer 638 exposed. Exposure can allow for a signal to emanate from the analyte sensor 634. This is because the analyte and interferents will diffuse through sensor membrane 812 to the tip at a different rate as compared to the working electrode 804. Thus, any analyte and interfered: that diffuses through the sensor membrane 812, and leading to any signal generated at the distal tip 650, can interfere with the signal generated by the working electrode 804 in the window 639. This can affect the accuracy of the analyte sensor 634.

[0084] Electrically insulating material 652 is applied over distal tip 650 to electrically isolate the exposed portion of the core 651 and the firstAtty. Dkt. No. 4855.148 WO 1 22 Client Reference No. 0966-PCT01conductive layer 638. This prevents interaction with any analytes or interferents with those portions as well as prevent electrical cross over between the core 651 and the first conductive layer 638. The electrically insulating material 652 has an average thickness in a range of from about 15 pm to about 35 pm, about 23 pm to about 31 pm, less than, equal to, or greater than about 15 pm. 16, 17, 18, 19, 20, 21, 22, 23, 24, 25. 26, 27 , 28, 29, 30, 31, 32, 33, 34, or about 35 pm. The membrane system 632 is applied over the core 651, the first conductive layer 638, and the electrically insulating material 652.

[0085] The distal tip 650 as a region extends no longer than 15% of the total length of the analyte sensor 634. The electrically insulating material 652 does not extend along the length of the analyte sensor 634 beyond 15% of the total length of the analyte sensor 634. Notably, the electrically insulating material 652 does not extend to window 639, which is a skived section of analyte sensor. If the electrically insulating material 652 was present at window 639, the desired electrical signal from window 639 would be blocked. Window 639 extends from about 15% to about 60% of the total length of analyte sensor 634.

[0086] The electrically insulating material 652 is a biocompatible material. In general, a biocompatible material is a substance that can function in contact with living tissue and / or biological fluids without causing adverse effects or reactions in the host organism. These materials may be engineered or selected to be substantially non-toxic, substantially non- immunogenic, substantially non-carcinogenic, substantially non-irritant, and / or substantially chemically stable when in contact with biological systems. A material’s biocompatibility may be determined by both its inherent properties and its specific interaction within the biological environment where it is used. This can include a consideration of the material’s chemical composition and surface properties, the duration and type of contact with biological tissues, the specific biological response it elicits, and its stability and degradation characteristics in the biological environment.Atty. Dkt. No. 4855.148 WO 1 23 Client Reference No. 0966-PCT01

[0087] In addition to biocompatibility, the material of the electrically insulating material 652 can be a UV-curable material. If the material is UV-curable, it can be easier and quicker to produce the analyte sensor 634.

[0088] The electrically insulating material 652 can be a material having a water absorption of less than about 0.6 wt. %, 0.5 wt. %, 0.4 wt. %, 0.3 wt. %, 0.2 wt. %, of 0.1 wt. %. Low water absorption is advantageous for polymers used in biomedical and other applications for several nonlimiting reasons. For example, when polymers absorb water, it can lead to dimensional changes, degradation of mechanical properties, and potential chemical breakdown of the material. In biomedical applications, water absorption can compromise the structural integrity of the polymer, potentially leading to premature failure of medical devices or implants. Water absorption can also affect the polymer’s biocompatibility by altering its surface properties and potentially releasing unwanted degradation products into the surrounding tissue. Additionally, water absorption can impact the polymer’s stability over time, potentially reducing its service life and reliability in critical applications. The water absorption can be measured using ASTM D570.

[0089] In general, the electrically insulating material 652 will have a volume resistivity in a range of from about 1 x 1013ohm-cm to about 1 x 1019ohm-cm. Volume resistivity, also known as electrical resistivity, is a property7of polymers that measures their ability to resist electrical current flow through the material’s volume. For polymers, a high-volume resistivity indicates strong electrical insulation properties. The volume resistivity of a polymer can be affected by various factors including temperature, humidity7, and the presence of additives or fillers in the polymer matrix. Higher volume resistivity values indicate better electrical insulation properties, while lower values suggest the material is more conductive. In biomedical applications, volume resistivity is particularly important as it affects the polymer’s interaction with biological systems and its suitability for specific medical devices, such the instant analyte sensor 634, which comes into contact with electrical components. The high-volume resistivity of the electrically insulating material 652 allows it to be classified as a non-conductive polymer.Atty. Dkt. No. 4855.148 WO 1 24 Client Reference No. 0966-PCT01

[0090] Particular polymers that meet the aforementioned criteria can include a polyurethane, parylene, a fluorinate polymer, polyethylene terephthalate, polyurethane, polyimide, copolymers thereof, or combinations thereof. Fluorinated polymers, such as PTFE (Polytetrafluoroethylene), may have good chemical resistance and low friction properties. These materials exhibit low water absorption and high volume resistivity.

[0091] Polyurethanes represent a diverse class of polymers characterized by their unique chemical structure containing urethane linkages (-NH-CO- O-). These versatile materials can be engineered to exhibit a wide range of physical and mechanical properties, from soft and flexible elastomers to rigid and durable plastics. The chemistry of polyurethanes can allow for control over their molecular structure through the reaction between diisocyanates and diols or polyols, allowing customization of properties such as hardness, flexibility, and biocompatibility. A suitable polyurethane for use in the electrically insulating material 652 can be a thermoplastic polyurethane polycarbonate silicone polymer.

[0092] The analyte sensor 634 may include more than one insulating material.For example, the analyte sensor 634 may include the aforementioned second layer 640, which can be an insulator. The material of the electrically insulating material 652. can be the same as any other insulating material or it can be different. The materials can be different in that they can be different classes of polymers or, if they are the same class of polymer, they may differ by their weight-average molecular weight.

[0093] The analyte sensor 634 can benefit from application of the electrically insulating material 652, in many ways. As described previously herein, the electrically insulating material 652 effectively blocks an electric signal emanating from the distal tip 650. For example, any signal emanating from the distal tip 650 can be less than 100 pA, 90 pA, 80 pA, 70 pA, 60 pA, 50 pA, 40 pA, 30 pA, 20 pA, 10 pA, or 0 pA. Blocking the electric signal emanating from the distal tip 650 can result in the analyte sensor 634 having a high level of accuracy as characterized, for example, by Mean Absolute Relative Difference (MARD). MARD measures the average difference between a device measurement (or testAtty. Dkt. No. 4855.148 WO 1 25 Client Reference No. 0966-PCT01result) and the reference measurement at normal to high glucose levels. The lower the MARD, the better the agreement between the device and the reference / comparator measurement. Conventionally, good accuracy on the first day, measured by MARD can be about 10% for adults and about 10.7% for pediatrics. Lower values indicate better accuracy.

[0094] The MARD can be measured across a plurality of corresponding (e.g., at least including the electrically insulating material 652 on the distal tip 650), analyte sensors and the MARD over a sensor session of greater than one day that is less than a corresponding analyte sensor differing only in that it is free of the electrically insulating material 652 on the distal tip 650. It is possible for about 95% to about 99.9% of mean absolute relative difference measurements over a sensor session of greater than one day are in a range of from about 8.0% to about 8.5%, about 8.07% to about 8.25%, less than, equal to, or greater than about 8.0%, 8.01, 8.02, 8.03, 8.04. 8.05. 8.06. 8.07. 8.08, 8.09, 8.10, 8.11, 8.12, 8.13, 8.14. 8.15. 8.16.8.17, 8.16, 8.17, 8.18, 8.19, 8.20, 8.21, 8.22, 8.23, 8.24, 8.25, 8.26, 8.27, 8.28, 8.29, 8.30, 8.31, 8.32, 8.33, 8.34, 8.35, 8.36, 8.37, 8.38, 8.39, 8.40, 8.41. 8.42. 8.43, 8.44, 8.45, 8.46, 8.47, 8.48, 8.49, or about 8.50%. The MARD values measured can be either adult or pediatric MARD values and are generally better than the aforementioned conventional values.

[0095] A standard deviation in MARD of the plurality of analyte sensors after one day can be less than about 2. It is possible, for the standard deviation in relative difference area of the plurality of analyte sensors 634 after one day to be improved by about 9% to about 40%, about 20% to about 40%, less than, equal to, or greater than about 9%, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37. 38, 39, or about 40%, compared to the plurality of corresponding analyte sensors.

[0096] Another benefit of putting the electrically insulating material 652 on the distal tip 650 is that an algorithm used to process the sample only needs to be optimized for a single signal generation source, rather than multiple sources. Without the electrically insulating material 652, the algorithm would have to account for this tip signal variability and use the best fitAtty. Dkt. No. 4855.148 WO 1 26 Client Reference No. 0966-PCT01model in view of the signals. By eliminating the tip signal, the input for the algorithm is more consistent and the tuning of the algorithm can be optimized for smaller range of inputs.

[0097] The electrically insulating material 652 can be applied in a controlled manner such that the electrically insulating material 652 is only located at the distal tip and is not located at the window 639. The application method can generally include contacting the distal tip 650 with a flowable solution of the electrically insulating material 652. The distal tip 650 is removed from contact with the passivation material after the analytical sensor 634 has traveled a predetermined distance. The predetermined distance can be reached when the distal tip 650 abuts a stop structure.

[0098] FIG. 10 is perspective view of a system 1000 for applying the electrical insulator material 652 to the distal tip 650 of the analyte sensor 634. As shown, the system 1000 includes a reservoir 1010. The reservoir 1010 is filled with the flowable electrically insulating material 1012. The flowable electrically insulating material 1012 (the same material as electrically insulating material 652, but in flowable form) is pumped through the interior of the wall 1014 until it reaches the top and flows over the exterior surface 1016 of the wall 1014. During the contacting operation, the pump is stopped, allowing the flowable electrically insulating material 1012 to form athin film on the exterior surface 1016. An analyte sensor 634 or an array of the analyte sensors are moved via a linear actuator toward the exterior surface 1016. The distal tip 650 or distal tips 650 of the array of analyte sensors are briefly submerged into the film of the flow able electrically insulating material 1012 before the linear actuator reverses direction, withdrawing the tips from the solution. This process can be repeated multiple times. When dipping is completed, the flowable electrically insulating material 1012 can be left to dry on the distal tip 250 or can be cured for example with UV curing or the like.

[0099] The system 1000 facilitates horizontal dipping in that a longitudinal axis passing through the distal tip 650 of the analytical sensor 634 is oriented substantially perpendicular to the flow of the flowable electrically insulating material 1012. In other examples, the flow' of the flowableAtty. Dkt. No. 4855.148 WO 1 27 Client Reference No. 0966-PCT01electrically insulating material 1012 and the longitudinal axis can be rotated about 90 degrees such that the distal tip 650 can be vertically dipped.

[0100] As an alternative, the flowable electrically insulating material 1012 can be located in a reservoir with one or more rollers positioned to contact and be coated with the flowable electorally insulating material 1012. The distal tip 650 can be contacted with the coated rollers to apply the electrically insulating material 652 thereto.

[0101] The disclosed dipping method offers several advantages. For example, the process prevents over-dipping of the electrically insulating material 652 into the window 639 by controlling the total thickness of the electrically insulating material 652 film to not exceed the length of the distal tip 650. Additionally, the exterior surface 101 serves as a physical barrier, preventing analyte sensors 634 that may protrude further than a nominal distance from their fixtures from being over-dipped into the solution. This is helpful when an array of analyte sensors are contacted with the flowable electrical insulating material 1012 in that it is possible for one or more of the analyte sensors 634 to protrude a different length relative to another analyte sensor on the array.

[0102] Although the examples illustrated in FIGS. 6-9 involve circumferentially extending membrane systems, the membranes described herein may be applied to any planar or non-planar surface, for example, the substratebased sensor structure of U.S. Pat. No. 6,565,509 to Say et al., which is incorporated by reference.

[0103] In an example in which the analyte sensor 634 is a glucose sensor, glucose analyte can be detected utilizing glucose oxidase. Glucose oxidase reacts with glucose to produce hydrogen peroxide (H2O2). The hydrogen peroxide reacts with the surface of the working electrode, producing two protons (2H+). two electrons (2e ) and one molecule of oxygen (O2). This produces an electronic current that may be detected by the sensor electronics 106. The amount of current is a function of the glucose concentration level. A calibration curve may be used to provide an estimated glucose concentration level based on a measured current. The amount of current is also a function of the diffusivity of glucoseAtty. Dkt. No. 4855.148 WO 1 28 Client Reference No. 0966-PCT01through the sensor membrane. The glucose diffusivity may change over time, which may cause the sensor glucose sensitivity to change over time, or “drift.”

[0104] FIG. 11 is a schematic illustration of a circuit 800 that represents the behavior of an example analyte sensor, such as the analyte sensor 634 shown in FIGS. 6-9. As described above, the interaction of hydrogen peroxide (generated from the interaction between glucose analyte and glucose oxidase) and working electrode (WE) 804 produces a voltage differential between the working electrode (WE) 804 and reference electrode (RE) 806 which drives a current. The current may make up all or part of a raw sensor signal that is measured by sensor electronics, such as the sensor electronics 106 of FIGS. 1-2, and used to estimate an analyte concentration (e.g., glucose concentration).

[0105] The circuit 800 also includes a double-layer capacitance (Cdl) 808, which occurs at an interface between the working electrode (WE) 804 and the adjacent membrane. The double-layer capacitance (Cdl) may occur at an interface between the working electrode 804 and the adjacent membrane due to the presence of two layers of ions with opposing polarity, as may occur during application of an applied voltage between the working electrode 804 and reference electrode. The equivalent circuit 800 may also include a polarization resistance (Rpol) 810, which may be relatively large, and may be modeled, for example, as a static value (e.g., 100 megaOhms), or as a variable quantity that varies as a function of glucose concentration level.

[0106] An estimated analyte concentration may be determined from a raw sensor signal based upon a measured current (or charge flow) through the analyte sensor membrane 812 when a bias potential is applied to the sensor circuit 800. For example, sensor electronics or another suitable computing device can use the raw sensor signal and a sensitivity of the sensor, which correlates a detected current flow to a glucose concentration level, to generate the estimated analyte concentration. In some examples, the device also uses a break-in characteristic, as described herein.Atty. Dkt. No. 4855.148 WO 1 29 Client Reference No. 0966-PCT01

[0107] With reference to the equivalent circuit 800, when a voltage is applied across the working and reference electrodes 804 and 806, a current may be considered to flow (forward or backward depending on polarity) through the internal electronics of transmitter (represented by R_Tx_intemal) 811; through the reference electrode (RE) 806 and working electrode (WE) 804, which may be designed to have a relatively low resistance; and through the sensor membrane 812 (Rmembr, which is relatively small). Depending on the state of the circuit, current may also flow through, or into, the relatively large polarization resistance 810 (which is indicated as a fixed resistance but may also be a variable resistance that varies with the body's glucose level, where a higher glucose level provides a smaller polarization resistance), or into the double-layer capacitance 808 (i.e., to charge the double-layer membrane capacitor formed at the working electrode 804), or both.

[0108] The impedance (or conductance) of the membrane (Rmembr) 812 is related to electrolyte mobility in the membrane, which is in turn related to glucose diffusivity in the membrane. As the impedance goes down (i.e., conductance goes up, as electrolyte mobility7in the membrane 812 goes up), the glucose sensitivity goes up (i.e., a higher glucose sensitivity means that a particular glucose concentration will produce a larger signal in the form of more current or charge flow). Impedance, glucose diffusivity, and glucose sensitivity are further described in U.S. Patent Publication No. US2012 / 0262298, yvhich is incorporated by reference in its entirety.Examples

[0109] Various embodiments of the present invention can be better understood by reference to the folloyving Examples which are offered by way of illustration. The present invention is not limited to the Examples given herein.

[0110] To verity' the performance of an analyte sensor with the distal tip coated with the electrically insulating material a test analyte sensor 1200 was produced. The test analyte sensor is shown in FIG. 12. As shown, the test analyte sensor 1200 includes a core 1210. The core 1210 includesAtty. Dkt. No. 4855.148 WO 1 30 Client Reference No. 0966-PCT01platinum clad tantalum, with an electrically insulating polyurethane coating 1220 disposed thereon. About half of the analyte sensor 1200 is covered by a reference electrode 1230. A distal tip 1240 is located where core 1210 is exposed by singulation.

[0111] Some test analyte sensors 1200 have the distal tip 1240 coated with an electrically insulating polyurethane coating 1220 (denoted in FIG. 13 as "No TP Non-Skive Wires’") A number of test analyte sensors 1200 do not have the distal tip 1240 coated with electrically insulating polyurethane coating (denoted in FIG. 13 as “TP Non-Skive Wires’’). All of the test analyte sensors 1200 are placed in a solution have a glucose concentration of 250 mg / dL. As shown in FIG. 13, after 14 days, the test analyte sensors 1200 with the distal tip 1240 coated did not generate a signal over a 14 day period. By contrast, the test analyte sensors 1200 without the distal tip 1240 coated did generate a signal over a 14 day period.Exemplary7Aspects.

[0112] The following exemplary aspects are provided, the numbering of which is not to be construed as designating levels of importance:

[0113] Aspect 1 provides an analyte sensor configured for insertion into a host for measuring a concentration of an analyte in the host, the analyte sensor comprising:a first conductive layer comprising a working electrode, wherein the working electrode is configured to generate a signal indicative of the concentration;a second conductive layer comprising a reference electrode and / or a counter electrode, the first conductive layer and the second conductive layer being substantially coaxial along a longitudinal axis,a distal tip comprising an exposed portion of the first conductive layer and the second conductive layer and characterized by a non-planer surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis, andAtty. Dkt. No. 4855.148 WO 1 31 Client Reference No. 0966-PCT01an electrically insulating material covering the at least a portion of distal tip, wherein the analyte sensor has a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding analyte sensor differing in that a distal tip of the corresponding analyte sensor is free of electrically insulating material.

[0114] Aspect 2 provides the analyte sensor of Aspect 1, wherein the electrically insulating material is a first electrically insulating material and the analyte sensor further comprises a second electrically insulating material located coaxially along the second conductive layer.

[0115] Aspect 3 provides the analyte sensor of Aspect 2, wherein the first and second electrically insulating materials comprise different materials.

[0116] Aspect 4 provides the analyte sensor of Aspect 2, wherein the first and second electrically insulating materials comprise the same materials.

[0117] Aspect 5 provides the analyte sensor of any of Aspects 1-4, wherein the distal tip comprises a singualated tip.

[0118] Aspect 6 provides the analyte sensor of Aspect 5, wherein the singualated tip is formed by mechanically cutting a wire.

[0119] Aspect 7 provides the analyte sensor of any of Aspects 1-6, wherein the distal tip extends from an end of the sensor to no greater than 15% of a longitudinal length.

[0120] Aspect 8 provides the analyte sensor of any of Aspects 1-7, further comprising a skived section exposing a portion of the first conductive layer located in a range of from about 15% to about 60% of a longitudinal length.

[0121] Aspect 9 provides the analyte sensor of Aspect 8, wherein the electrically insulating material covering the at least a portion of distal tip does not contact the skived section.

[0122] Aspect 10 provides the analyte sensor of any of Aspects 1-9, wherein about 95% to about 99.9% of mean absolute relative difference measurements over a sensor session of greater than one day are in a range of from about 8.0% to about 8.5%.

[0123] Aspect 11 provides the analyte sensor of any of Aspects 1-10, wherein about 95% to about 99.9% of mean absolute relative differenceAtty. Dkt. No. 4855.148 WO 1 32 Client Reference No. 0966-PCT01measurements over a sensor session of greater than one day are in a range of from about 8.07% to about 8.25%.

[0124] Aspect 12 provides the analyte sensor of any of Aspects 1-11, wherein the mean absolute relative difference measurement is an adult mean absolute relative difference or a pediatric mean absolute relative difference measurement.

[0125] Aspect 13 provides the analyte sensor of any of Aspects 1-12, wherein the first conductive layer comprises a noble metal.

[0126] Aspect 14 provides the analyte sensor of any of Aspects 1-13, wherein the first conductive layer comprises platinum, gold, carbon, or a combinations thereof.

[0127] Aspect 15 provides the analyte sensor of any of Aspects 2-14, wherein the second conductive layer comprises carbon, stainless steel, Ir, Pd, Rh, PtRhPd, Pt, Pt / Rh, a modified carbon, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), or combinations thereof..

[0128] Aspect 16 provides the analyte sensor of any of Aspects 1-15, wherein the second conductive layer comprises silver / silver chloride.

[0129] Aspect 17 provides the analyte sensor of any of Aspects 1-15, wherein the first electrically insulating material comprises a biocompatible material.

[0130] Aspect 18 provides the analyte sensor of any of Aspects 1-17, wherein the electrically insulating material comprises a UV-curable material.

[0131] Aspect 19 provides the analyte sensor of any of Aspects 1-18, wherein the electrically insulating material comprises a material having a water absorption of less than about 0.6 wt. %.

[0132] Aspect 20 provides the analyte sensor of any of Aspects 1-19, wherein the electrically insulating material comprises a material having a volume resistivity greater than about 1 x 1013ohm-cm.

[0133] Aspect 21 provides the analyte sensor of any of Aspects 2-20, wherein the first electrically insulating material comprises a non-conductive polymer.

[0134] Aspect 22 provides the analyte sensor of Aspect 21, wherein the non- conductive polymer comprises a polyurethane.Atty. Dkt. No. 4855.148 WO 1 33 Client Reference No. 0966-PCT01

[0135] Aspect 23 provides the analyte sensor of any of Aspects 2-22, wherein the second electrically insulating material comprises a non-conductive polymer.

[0136] Aspect 24 provides the analyte sensor of Aspect 23, wherein the non- conductive polymer comprises parylene, a fluorinate polymer, polyethylene terephthalate, polyurethane, polyimide, copolymers thereof, or combinations thereof.

[0137] Aspect 25 provides the analyte sensor of any of Aspects 2-24, wherein the second electrically insulating material comprises a polyurethane.

[0138] Aspect 26 provides the analyte sensor of any of Aspects 1-25, wherein the electrically insulating material has an average thickness in a range of from about 15 pm to about 35 pm.

[0139] Aspect 27 provides the analyte sensor of any of Aspects 1-26, wherein the electrically insulating material has an average thickness in a range of from about 23 pm to about 31 pm.

[0140] Aspect 28 provides the analyte sensor of any of Aspects 1-27, wherein the analyte sensor is one of a plurality of analyte sensors each having a substantially identical composition and, wherein the each of the plurality7of analyte sensors has a level of accuracy corresponding to a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding plurality of analyte sensors differing only in that they are free of the electrically insulating material and a standard deviation in relative difference area of the plurality7of analyte sensors after one day is less than about 2.

[0141] Aspect 29 provides the analyte sensor of Aspect 28, wherein the standard deviation in relative difference area of the plurality^ of analyte sensors after one day is improved by about 9% to about 40% compared to the plurality of corresponding analyte sensors.

[0142] Aspect 30 provides a method of forming a tip passivation layer on an analyte sensor, the method comprising:contacting a distal tip of an analytical sensor with a passivation material; andAtty. Dkt. No. 4855.148 WO 1 34 Client Reference No. 0966-PCT01removing the distal tip of the analytical sensor from contact with the passivation material after the analytical sensor has traveled a predetermined distance.

[0143] Aspect 31 provides the method of Aspect 30, wherein the predetermined distance is reached when the distal tip abuts a stop structure.

[0144] Aspect 32 provides the method of any of Aspects 30 or 31, wherein the passivation material is a flowing material.

[0145] Aspect 33 provides the method of Aspect 32, wherein a longitudinal axis passing through the distal tip of the analytical sensor is oriented substantially perpendicular to a flow of the passivation material.

[0146] Aspect 34 provides the method of any of Aspects 30-33, wherein the analyte sensor comprises:a first conductive layer comprising a working electrode, wherein the working electrode is configured to generate a signal indicative of a concentration of an analyte;a second conductive layer comprising a reference electrode and / or a counter electrode, the first conductive layer and the second conductive layer being substantially coaxial along a longitudinal axis, wherein the distal tip comprises an exposed portion of the first conductive layer and a second conductive layer and characterized by anon-planer surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis.

[0147] Aspect 35 provides the method of any of Aspects 30-34, wherein the distal tip extends from an end of the sensor to no greater than 15% of a longitudinal length.

[0148] Aspect 36 provides the method of any of Aspects 34 or 35, further comprising a skived section exposing a portion of the first conductive layer located in a range of from about 15% to about 60% of a longitudinal length.

[0149] Aspect 37 provides the method of Aspect 36, wherein the passivation material does not contact the skived section.

[0150] Aspect 38 provides the method of any of Aspects 30-37. wherein about 95% to about 99.9% of mean absolute relative difference measurementsAtty. Dkt. No. 4855.148 WO 1 35 Client Reference No. 0966-PCT01over a sensor session of greater than one day are in a range of from about 8.0% to about 8.5%.

[0151] Aspect 39 provides the method of any of Aspects 34-38, wherein the first conductive layer comprises a noble metal.

[0152] Aspect 40 provides the method of any of Aspects 34-39, wherein the first conductive layer comprises platinum, gold, carbon, or a combinations thereof.

[0153] Aspect 41 provides the method of any of Aspects 34-40, wherein the second conductive layer comprises carbon, stainless steel, Ir, Pd, Rh, PtRhPd, Pt, Pt / Rh, a modified carbon, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), or combinations thereof.

[0154] Aspect 42 provides the method of any of Aspects 34-41, wherein the second conductive layer comprises silver / silver chloride.

[0155] Aspect 43 provides the method of any of Aspects 34-52, wherein the passivation material comprises a biocompatible material.

[0156] Aspect 44 provides the method of any of Aspects 34-43, wherein the passivation material comprises a UV-curable material.

[0157] Aspect 45 provides the method of Aspect 44, further comprising exposing the passivation material to UV-light.

[0158] Aspect 46 provides the method of any of Aspects 34-45, wherein the passivation material comprises a material having a water absorption of less than about 0.6%.

[0159] Aspect 47 provides the method of any of Aspects 34-46, wherein the passivation material comprises a material having a volume resistivity greater than about 1 x 1013ohm-cm.

[0160] Aspect 48 provides the method of any of Aspects 34-47, wherein the passivation material comprises polyurethane.

[0161] Aspect 49 provides the method of any of Aspects 34-48, wherein the passivation material is located on a roller and the distal tip is contacted with the passivation material on the roller.

[0162] Aspect 50 provides the method of any of Aspects 34-49, further comprising singulating the analyte sensor from a bulk analyte sensor material.Atty. Dkt. No. 4855.148 WO 1 36 Client Reference No. 0966-PCT01

[0163] Aspect 51 provides the method of Aspect 50, wherein singulating is performed by mechanically cutting a wire.

[0164] Aspect 52 provides the method of Aspect 50, wherein singulating is performed by laser cutting a wire.

[0165] Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

[0166] Various components are described in the present disclosure as being configured in a particular way. A component may be configured in any suitable manner. For example, a component that is or that includes a computing device may be configured with suitable software instructions that program the computing device. A component may also be configured by virtue of its hardware arrangement or in any other suitable manner.

[0167] The above description is intended to be illustrative, and not restrictive.For example, the above-described examples (or one or more aspects thereof) can be used in combination with others. Other examples can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is to allow the reader to quickly ascertain the nature of the technical disclosure, for example, to comply with 37 C.F.R. § 1.72(b) in the United States of America. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0168] Also, in the above Detailed Description, various features can be grouped together to streamline the disclosure. However, the claims cannot set forth every feature disclosed herein, as examples can feature a subset ofAtty. Dkt. No. 4855.148 WO 1 37 Client Reference No. 0966-PCT01said features. Further, examples can include fewer features than those disclosed in a particular example. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate example. The scope of the examples disclosed herein is to be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0169] Each of these non-limiting examples in any portion of the above description may stand on its own or may be combined in various permutations or combinations with one or more of the other examples.

[0170] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the subject matter can be practiced. These embodiments are also referred to herein as “examples."’ Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements show n or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0171] In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

[0172] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms "including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements inAtty. Dkt. No. 4855.148 WO 1 38 Client Reference No. 0966-PCT01addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms ‘'first,” "second." '‘third,” etc., are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0173] Geometric terms, such as “parallel”, “perpendicular"’, “round”, or “square" are not intended to require absolute mathematical precision, unless the context indicates otherwise. Instead, such geometric terms allow for variations due to manufacturing or equivalent functions. For example, if an element is described as “round” or “generally round”, a component that is not precisely circular (e.g., one that is slightly oblong or is a many-sided polygon) is still encompassed by this description.

[0174] Method examples described herein can be machine or computer- implemented at least in part. Some examples can include a computer- readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as descnbed in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to. hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.

[0175] The above description is intended to be illustrative, and not restrictive.For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit theAtty. Dkt. No. 4855.148 WO 1 39 Client Reference No. 0966-PCT01scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the subject matter should be determined with reference to the claims, along with the full scope of equivalents to which such claims are entitled.Atty. Dkt. No. 4855.148 WO 1 40 Client Reference No. 0966-PCT01

Claims

CLAIMSWhat is claimed is:

1. An analyte sensor configured for insertion into a host for measuring a concentration of an analyte in the host, the analyte sensor comprising:a first conductive layer comprising a working electrode, wherein the working electrode is configured to generate a signal indicative of the concentration;a second conductive layer comprising a reference electrode and / or a counter electrode, the first conductive layer and the second conductive layer being substantially coaxial along a longitudinal axis,a distal tip comprising an exposed portion of the first conductive layer and the second conductive layer and characterized by a non-planer surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis, andan electrically insulating material covering the at least a portion of distal tip, wherein the analyte sensor has a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding analyte sensor differing in that a distal tip of the corresponding analyte sensor is free of electrically insulating material.

2. The analyte sensor of claim 1, wherein the electrically insulating material is a first electrically insulating material and the analyte sensor further comprises a second electrically insulating material located coaxially along the second conductive layer.

3. The analyte sensor of claim 2, wherein the first and second electrically insulating materials comprise different materials.

4. The analyte sensor of claim 2, wherein the first and second electrically insulating materials comprise the same materials.Atty. Dkt. No. 4855.148 WO 1 41 Client Reference No. 0966-PCT015. The analyte sensor of any of claims 1-4, wherein the distal tip comprises a singulated tip.

6. The analyte sensor of claim 5, wherein the singulated tip is formed by mechanically cutting a wire.

7. The analyte sensor of any of claims 1-6, wherein the distal tip extends from an end of the sensor to no greater than 15% of a longitudinal length.

8. The analyte sensor of any of claims 1-7, further comprising a skived section exposing a portion of the first conductive layer located in a range of from about 15% to about 60% of a longitudinal length.

9. The analyte sensor of claim 8, wherein the electrically insulating material covering the at least a portion of distal tip does not contact the skived section.

10. The analyte sensor of any of claims 1-9, wherein about 95% to about 99.9% of mean absolute relative difference measurements over a sensor session of greater than one day are in a range of from about 8.0% to about 8.5%.

11. The analyte sensor of any of claims 1-10, wherein about 95% to about 99.9% of mean absolute relative difference measurements over a sensor session of greater than one day are in a range of from about 8.07% to about 8.25%.

12. The analyte sensor of any of claims 1-11, wherein the mean absolute relative difference measurement is an adult mean absolute relative difference or a pediatric mean absolute relative difference measurement.

13. The analyte sensor of any of claims 1-12, wherein the first conductive layer comprises a noble metal.

14. The analyte sensor of any of claims 1-13, wherein the first conductive layer comprises platinum, gold, carbon, or a combinations thereof.Atty. Dkt. No. 4855.148 WO 1 42 Client Reference No. 0966-PCT0115. The analyte sensor of any of claims 2-14, wherein the second conductive layer comprises carbon, stainless steel, Ir, Pd, Rh, PtRhPd, Pt, Pt / Rh, a modified carbon, poly(3,4-ethylenedioxythiophene) polysty rene sulfonate (PEDOTPSS), or combinations thereof.

16. The analyte sensor of any of claims 1-15, wherein the second conductive layer comprises silver / silver chloride.

17. The analyte sensor of any of claims 1-15, wherein the first electrically insulating material comprises a biocompatible material.

18. The analyte sensor of any of claims 1-17, wherein the electrically insulating material comprises a UV-curable material.

19. The analyte sensor of any of claims 1-18, wherein the electrically insulating material comprises a material having a water absorption of less than about 0.6 wt. %.

20. The analyte sensor of any of claims 1-19, wherein the electrically insulating material comprises a material having a volume resistivity greater than about 1 x 1013ohm-cm.

21. The analyte sensor of any of claims 2-20, wherein the first electrically insulating material comprises a non-conductive polymer.

22. The analyte sensor of claim 21, wherein the non-conductive polymer comprises a polyurethane.

23. The analyte sensor of any of claims 2-22, wherein the second electrically insulating material comprises a non-conductive polymer.Atty. Dkt. No. 4855.148 WO 1 43 Client Reference No. 0966-PCT0124. The analyte sensor of claim 23, wherein the non-conductive polymer comprises parylene, a fluorinate polymer, polyethylene terephthalate, polyurethane, polyimide, copolymers thereof, or combinations thereof.

25. The analyte sensor of any of claims 2-24, wherein the second electrically insulating material comprises a polyurethane.

26. The analyte sensor of any of claims 1-25, wherein the electrically insulating material has an average thickness in a range of from about 15 pm to about 35 pm.

27. The analyte sensor of any of claims 1-26, wherein the electrically insulating material has an average thickness in a range of from about 23 pm to about 31 pm.

28. The analyte sensor of any of claims 1-27, wherein the analyte sensor is one of a plurality of analyte sensors each having a substantially identical composition and, wherein the each of the plurality7of analyte sensors has a level of accuracy corresponding to a mean absolute relative difference over a sensor session of greater than one day that is less than a corresponding plurality of analyte sensors differing only in that they are free of the electrically insulating material and a standard deviation in relative difference area of the plurality' of analyte sensors after one day is less than about 2.

29. The analyte sensor of claim 28, wherein the standard deviation in relative difference area of the plurality of analyte sensors after one day is improved by about 9% to about 40% compared to the plurality' of corresponding analyte sensors.Atty. Dkt. No. 4855.148 WO 1 44 Client Reference No. 0966-PCT0130. A method of forming a tip passivation layer on an analyte sensor, the method comprising:contacting a distal tip of an analytical sensor with a passivation material; and removing the distal tip of the analytical sensor from contact with the passivation material after the analytical sensor has traveled a predetermined distance.

31. The method of claim 30, wherein the predetermined distance is reached when the distal tip abuts a stop structure.

32. The method of any of claims 30 or 31, wherein the passivation material is a flowing material.

33. The method of claim 32, wherein a longitudinal axis passing through the distal tip of the analytical sensor is oriented substantially perpendicular to a flow of the passivation material.

34. The method of any of claims 30-33, wherein the analyte sensor comprises:a first conductive layer comprising a working electrode, wherein the working electrode is configured to generate a signal indicative of a concentration of an analyte;a second conductive layer comprising a reference electrode and / or a counter electrode, the first conductive layer and the second conductive layer being substantially coaxial along a longitudinal axis, whereinthe distal tip comprises an exposed portion of the first conductive layer and a second conductive layer and characterized by a non-planer surface comprising at least one projection extending from a plane perpendicular to the longitudinal axis.

35. The method of any of claims 30-34, wherein the distal tip extends from an end of the sensor to no greater than 15% of a longitudinal length.Atty. Dkt. No. 4855.148 WO 1 45 Client Reference No. 0966-PCT0136. The method of any of claims 34 or 35, further comprising a skived section exposing a portion of the first conductive layer located in a range of from about 15% to about 60% of a longitudinal length.

37. The method of claim 36, wherein the passivation material does not contact the skived section.

38. The method of any of claims 30-37, wherein about 95% to about 99.9% of mean absolute relative difference measurements over a sensor session of greater than one day are in a range of from about 8.0% to about 8.5%.

39. The method of any of claims 34-38, wherein the first conductive layer comprises a noble metal.

40. The method of any of claims 34-39, wherein the first conductive layer comprises platinum, gold, carbon, or a combinations thereof.

41. The method of any of claims 34-40, wherein the second conductive layer comprises carbon, stainless steel, Ir, Pd, Rh, PtRhPd, Pt, Pt / Rh, a modified carbon, poly(3.4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). or combinations thereof.

42. The method of any of claims 34-41 , wherein the second conductive layer comprises silver / silver chloride.

43. The method of any of claims 34-42, wherein the passivation material comprises a biocompatible material.

44. The method of any of claims 34-43, wherein the passivation material comprises a UV-curable material.

45. The method of claim 44, further comprising exposing the passivation material to UV-light.Atty. Dkt. No. 4855.148 WO 1 46 Client Reference No. 0966-PCT0146. method of any of claims 34-45, wherein the passivation material comprises a material having a water absorption of less than about 0.6%.

47. The method of any of claims 34-46, wherein the passivation material comprises a material having a volume resistivity greater than about 1 x 1013ohm-cm.

48. The method of any of claims 34-47, wherein the passivation material comprises polyurethane.

49. The method of any of claims 34-48, wherein the passivation material is located on a roller and the distal tip is contacted with the passivation material on the roller.

50. The method of any of claims 34-49, further comprising singulating the analyte sensor from a bulk analyte sensor material.

51. The method of claim 50, wherein singulating is performed by mechanically cutting a wire.

52. The method of claim 50, wherein singulating is performed by laser cutting a wire.Atty. Dkt. No. 4855.148 WO 1 47 Client Reference No. 0966-PCT01

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