Sterile reusable wearable device for continuous analyte monitoring and method of forming a wearable device - Patent Application 20070122997

Abstract

In one or more embodiments, a continuous analyte monitoring wearable device includes a disposable base unit having a power source and an analyte sensor, and a reusable transmitter unit including electronic circuitry configured to bias the analyte sensor, measure current through the analyte sensor, and also calculate an analyte value based on the measured current through the analyte sensor. The disposable base unit is coupled to the reusable transmitter unit and configured to power the electronic circuitry of the reusable transmitter unit for continuous analyte monitoring. Numerous other embodiments are also provided.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 965,682, entitled "METHODS AND APPARATUS FOR REUSING TRANSMITTER ELECTRONICS OF A CONTINUOUS ANALYTE MONITORING DEVICE," filed January 24, 2020, and U.S. Provisional Patent Application No. 63 / 111,347, entitled "STERILIZED REUSABLE WEARABLE DEVICES AND WEARABLE DEVICE FORMING METHODS IN CONTINUOUS ANALYTE MONITORING," filed November 9, 2020, each of which is incorporated herein by reference in its entirety for all purposes.

[0002] SUMMARY The present disclosure relates to continuous analyte monitoring methods, devices, and systems. [Background technology]

[0003] In vivo continuous analyte monitoring (CAM), such as continuous glucose monitoring (CGM), has become a routine detection operation, especially in diabetes care. By providing real-time glucose concentration monitoring, therapeutic / clinical actions can be applied in a more timely manner, leading to better control of glycemic conditions.

[0004] During CGM operation, the biosensor in the CGM wearable device, typically inserted subcutaneously, operates continuously in an environment surrounded by tissue and interstitial fluid. The subcutaneously inserted biosensor provides a signal to the wireless CGM transmitter in the CGM wearable device, which indicates the user's blood glucose level. These measurements may be taken automatically multiple times throughout the day (e.g., every few minutes or at other suitable intervals).

[0005] The CGM wearable device can be attached to the external surface of the user's skin, such as the abdomen or the back of the upper arm, while the biosensor is inserted through the skin to contact interstitial fluid. The biosensor interacts with the interstitial fluid and generates an electrical signal proportional to the amount of glucose present in the interstitial fluid. These electrical signals can be communicated to a CGM transmitter and further communicated to an external device, such as a CGM reader device or a smartphone containing a software application, which can be used to determine glucose levels and display / communicate the glucose measurements in various desired formats.

[0006] Creating wearable CGM devices that are comfortable for patients and cost-effective remains a challenge, and improved wearable CGM devices, systems, and methods are desirable. Summary of the Invention

[0007] In some embodiments, a continuous analyte monitoring wearable device is provided, the continuous analyte monitoring wearable device including: a base unit including a base, at least one power source, and an analyte sensor assembly; and an enclosure extending over the base and the at least one power source to form the enclosed base, the enclosed base including an attachment area configured to allow a reusable transmitter unit to be coupled to and separated from the enclosed base, the enclosed base, the at least one power source, and the analyte sensor forming a disposable unit, and the disposable unit is sterilized.

[0008] In a further embodiment, a method of forming a continuous analyte monitoring wearable device is provided, the method including: providing a base having a power source support location, a sensor assembly support location, and a transmitter unit support location; disposing at least one power source at the power source support location; disposing a sensor assembly including an analyte sensor at the sensor assembly support location; providing an encapsulation layer over the at least one power source, at least a portion of the sensor assembly, and at least a portion of the base to form a sealed disposable unit, the sealed disposable unit configured to allow the transmitter unit to be attached to and removed from the transmitter unit support location; and sterilizing the sealed disposable unit.

[0009] In some additional embodiments, a method of forming a wearable device configured for use in continuous analyte monitoring is provided, the method including providing a base having a transmitter unit support location, a power source support location, and a sensor assembly support location, disposing at least one power source at the power source support location, disposing a sensor assembly including an analyte sensor at the sensor assembly support location, providing an enclosure portion having an opening, disposing the base within the opening of the enclosure portion such that the base and the enclosure portion form a sealed disposable base unit, the sealed disposable base unit configured to allow the transmitter unit to be attached to and removed from the transmitter unit support location, and sterilizing the sealed disposable unit.

[0010] Other features, aspects, and advantages of embodiments according to the present disclosure will become more fully apparent from the summary, claims, and accompanying drawings, which set forth a number of exemplary embodiments and implementations. Various embodiments according to the present disclosure are also capable of other and different applications, and their several details can be modified in various respects, all without departing from the scope of the present disclosure. [Brief explanation of the drawings]

[0011] The drawings described below are for illustrative purposes and are not necessarily drawn to scale. Accordingly, the drawings and detailed description should be regarded as illustrative in nature and not as restrictive. The drawings are not intended to limit the scope of the present disclosure in any way.

[0012] [Figure 1A] 1A and 1B show a top perspective view and a side view, respectively, of a continuous analyte monitoring wearable device configured for use in a CAM system, according to embodiments provided herein. [Figure 1B] Same as above.

[0013] [Figure 1C] FIG. 1C shows an exploded perspective view of a first exemplary embodiment of a wearable device with a disposable base unit and a reusable transmitter unit, with the enclosures shown as separate elements, as provided herein.

[0014] [Figure 1D] FIG. 1D shows an enlarged perspective view of the base and transmitter unit of FIG. 1C that can be coupled and detached therefrom as provided herein.

[0015] [Figure 1E] FIG. 1E shows an enlarged perspective view of the base and transmitter unit of FIG. 1C with the transmitter unit positioned within the transmitter unit support location of the base and the power supply positioned within the power supply support location of the base, respectively, as provided herein.

[0016] [Figure 1F] FIG. 1F shows a different side perspective view of a sensor coupled to a connector as provided herein, as the sensor passes through a sensor opening at a sensor assembly support location.

[0017] [Figure 1G] FIG. 1G shows an exploded view of an alternative embodiment of a wearable device including a disposable base unit and a reusable transmitter unit as provided herein.

[0018] [Figure 1H] 1H and 1I show side views of an alternative embodiment of a wearable device in which a transmitter unit can be attached to a disposable base unit at an attachment area of ​​an encapsulation layer, according to an embodiment as provided herein, with FIG. 1H showing the transmitter unit in a detached state and FIG. 1I showing the transmitter unit in an attached state. [Figure 1I] Same as above.

[0019] [Figure 2] FIG. 2 shows an exploded view of an exemplary transmitter unit and base according to embodiments provided herein.

[0020] [Figure 3A] FIG. 3A shows a cross-sectional side view of a wearable device before inserting the transmitter unit into the base unit, according to some embodiments.

[0021] [Figure 3B] FIG. 3B shows a cross-sectional side view of the wearable device after the transmitter unit has been inserted into the base unit, according to some embodiments.

[0022] [Figure 4A] 4A and 4B show a top perspective view and an exploded side perspective view, respectively, of another exemplary wearable device provided herein. [Figure 4B] Same as above.

[0023] [Figure 4C] FIG. 4C shows a bottom perspective view of another wearable device provided herein.

[0024] [Figure 4D] FIG. 4D shows a bottom perspective view of an alternative embodiment of a wearable device in which a single microneedle is used, according to embodiments provided herein.

[0025] [Figure 4E] FIG. 4E illustrates an enlarged cross-sectional view of a portion of the wearable device of FIG. 4A showing the transmitter unit inserted into the base unit, according to an embodiment provided herein.

[0026] [Figure 5] FIG. 5 shows a flowchart of an exemplary method for continuous analyte monitoring according to embodiments provided herein.

[0027] [Figure 6] FIG. 6 shows a flowchart of another exemplary method for continuous analyte monitoring according to embodiments provided herein.

[0028] [Figure 7] FIG. 7 shows a flowchart of an exemplary method for forming a wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0029] [Figure 8] FIG. 8 shows a flowchart of another exemplary method for forming a wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0030] [Figure 9] FIG. 9 shows a flowchart of another exemplary method for forming a wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0031] [Figure 10A]FIG. 10A shows a high-level block diagram of an exemplary CGM system according to embodiments provided herein.

[0032] [Figure 10B] FIG. 10B illustrates an exemplary CGM system similar to the embodiment shown in FIG. 10A, but with a different division of components, according to embodiments provided herein.

[0033] [Figure 11] FIG. 11 is an exploded bottom view of a wearable device according to some embodiments provided herein, wherein the base unit has an opening that allows the transmitter unit to be inserted into or removed from the base unit.

[0034] [Figure 12A] FIG. 12A shows a top perspective view of another wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0035] [Figure 12B] FIG. 12B is a top view of the base unit of 12A without the insertion device, transmitter unit, or power supply, according to embodiments provided herein.

[0036] [Figure 12C] FIG. 12C is a cross-sectional side view of a portion of the wearable device of FIG. 12A according to embodiments provided herein.

[0037] [Figure 13A] 13A and 13B are top views of another example of a disposable base unit according to embodiments provided herein. [Figure 13B] Same as above.

[0038] [Figure 14]FIG. 14 shows a flowchart of a method for forming a wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0039] [Figure 15] FIG. 15 shows a flowchart of another method of forming a wearable device for use during continuous analyte monitoring according to embodiments provided herein.

[0040] [Figure 16] 16 and 17 show packaging for a continuous analyte monitoring wearable device according to embodiments provided herein. [Figure 17] Same as above.

[0041] [Figure 18] FIG. 18 illustrates a method of forming a continuous analyte monitoring wearable device according to embodiments provided herein. DETAILED DESCRIPTION OF THE INVENTION

[0042] To more closely monitor a person's glucose levels and detect any changes in glucose levels, continuous glucose monitoring (CGM) methods, devices, and systems have been developed. Although CGM systems generate a glucose signal "continuously" during operation, such as a continuous electrochemically generated signal, measurements of the generated glucose signal are not truly continuous, but are typically taken every few minutes.

[0043] CGM systems generally have a wearable portion (wearable device) that wirelessly communicates with an external device, such as a handheld monitor or reader, smartphone, or other computing device. The wearable device can be worn for several days before being removed and replaced (e.g., after seven days or more). The wearable device includes a sensor inserted to be positioned under the skin. The wearable device also includes circuitry (e.g., analog circuitry) configured to bias the sensor and measure a current signal generated by the sensor upon contact with interstitial fluid. The wearable device further includes processing circuitry configured to process the current signal, such as to determine a glucose level based on the measured current signal and to transmit the glucose level to an external device of the CGM system. A CGM system is composed of the wearable device and the external device. The wearable device can be attached to the external surface of the skin, such as the abdomen, the back of the upper arm, or another suitable body location. Unlike blood glucose monitoring (BGM) systems, which measure glucose levels in blood, CGM systems measure glucose levels in interstitial fluid (including indirect capillary blood).

[0044] CGM systems may provide frequent measurements of a person's glucose levels without the need to involve the collection of a blood sample, such as by finger prick, for each such measurement. CGM systems may still employ finger pricks and the use of a BGM system, such as the Contour NEXT One® by Ascensia Diabetes Care AG of Basel, Switzerland, for calibration of the CGM system in some cases.

[0045] Wearable devices in continuous analyte monitoring systems are typically worn for seven or more days, ten or more days, or fourteen or more days, after which they are removed and replaced with new wearable devices. Having to replace wearable devices in continuous analyte monitoring systems every seven days or more frequently increases the cost of implementing continuous analyte monitoring.

[0046] Therefore, in view of the problems of the prior art, embodiments described herein provide a wearable device for use with an external device during continuous analyte monitoring that includes a disposable portion and a reusable portion. The disposable portion includes the wearable device and a power source for the analyte sensor, while the reusable portion includes electronic circuitry used, for example, to provide a bias to the analyte sensor, measure a current signal through the analyte sensor, and / or transmit signals and / or information to the external device. The electronic circuitry of the reusable portion of the wearable device can further calculate an analyte concentration value, such as a glucose concentration value, based on the measured current signal. In some embodiments, these analyte concentration values ​​can be transmitted to the external device.

[0047] The reusable portion is also referred to herein as a reusable transmitter unit. Exemplary circuitry within the transmitter unit can include an analog front end configured to bias the analyte sensor and detect current passing through the analyte sensor. The front end can include one or more operational amplifiers, current detection circuitry, etc. Other circuitry within the transmitter unit can include processing circuitry such as an analog-to-digital converter for digitizing the current signal, memory for storing the digitized current signal, a controller such as a microcontroller or microprocessor for calculating an analyte concentration value based on the measured current signal, etc., and transmitter circuitry for transmitting the signal and / or the analyte concentration value to an external device.

[0048] The electronic circuitry is typically the most expensive part of a wearable device and can last significantly longer than the period the wearable device is employed for - for example, wearable devices are typically discarded after about seven days, while the circuitry within the transmitter unit can potentially last indefinitely.

[0049] The two components that are most likely to need to be replaced in a wearable device used for continuous analyte monitoring are the power source (e.g., one or more batteries that power the electrical components of the wearable device) and the analyte sensor. By placing the power source (e.g., battery) and sensor in a disposable portion of the wearable device (also referred to as a disposable base unit), the two components that would need to be replaced after every use can be replaced, while the reusable transmitter unit that houses the electronics of the wearable device can be reused 10, 20, 50, 100, or even more than 100 times.

[0050] For example, in some embodiments, a wearable device for use during continuous analyte monitoring may include a disposable base unit having a sensor assembly and a power source, and a reusable transmitter unit configured to mate with the disposable base unit and receive power from the disposable base unit's power source. The disposable base unit is configured to be discarded after a single analyte monitoring period (e.g., 7-14 days after initiation of use), and the reusable transmitter unit is configured to be detached from the disposable base unit after the single analyte monitoring period and reused with another disposable base unit. As used herein, an analyte monitoring period is the elapsed time during which a sensor in the disposable unit is operable to monitor an analyte. These and other wearable device embodiments, continuous analyte monitoring systems, and methods for making and / or using such wearable devices are described below with reference to FIGS. 1A-15.

[0051] 1A and 1B show a top perspective view and a side view, respectively, of a wearable device 100 configured to be used during continuous analyte monitoring according to embodiments provided herein. With reference to FIG. 1A, the wearable device 100 includes a disposable base unit 102 and a reusable transmitter unit 104 that mates with the disposable base unit 102. The reusable transmitter unit 104 may be configured to receive power from a power source disposed within the disposable base unit 102 and receive electrical signals from an analyte sensor associated with the disposable base unit 102, as described further below. In some embodiments, the disposable base unit 102 is configured to be discarded after a single analyte monitoring period (e.g., 7 days, 10 days, 14 days, or other suitably long period), while the reusable transmitter unit 104 is configured to be detached from the disposable base unit 102 after the single analyte monitoring period and reused with a new disposable base unit. For example, the transmitter unit 104 may be reused 2 times, 5 times, 10 times, 50 times, 100 times, or even more than 100 times. Example embodiments of the disposable base unit 102 and the transmitter unit 104 are described below.

[0052] FIGURE 1C shows an exploded perspective view of a first exemplary embodiment of a disposable base unit 102, as provided herein, and also shows a reusable transmitter unit 104 shown in perspective. Referring to FIGURE 1C, the disposable base unit 102 includes a base 106 having one or more power supply support locations 108a-108b, a transmitter unit support location 110, and a sensor assembly support location 112. FIGURE 1D shows an enlarged perspective view of the base 106 and transmitter unit 104 of FIGURE 1C.

[0053] In some embodiments, the base 106 may be formed from a plastic resin, such as, but not limited to, acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, acetal, polyphthalamide (PPA), polysulfone, polyethersulfone, polyetheretherketone (PEEK), polypropylene, high density polyethylene (HDPE), and low density polyethylene (LDPE). Other materials may be used.

[0054] The power supply support locations 108a-108b provide locations for supporting one or more power supplies used to power the transmitter unit 104. For example, one or more power supplies 114a-114b may be positioned at the power supply support locations 108a, 108b. The power supply support locations 108a, 108b may be any suitable shape in top view (e.g., rectangular, square, round, etc.) and may include any suitable configuration of electrical contacts configured to electrically contact respective poles of the one or more power supplies 114a-114b, such as the multi-pole connector shown. Such a multi-pole connector may be formed of any conductive material, such as, for example, metal or metal tape. Furthermore, the support locations 108a, 108b may include any suitable configuration of conductive electrical contact traces that enable power connection from the electrical contacts to the connector 122 to the transmitter unit 104.

[0055] FIG. 1E further illustrates an enlarged perspective view of the base 106 and transmitter unit 104 of FIG. 1C with the transmitter unit 104 positioned in the transmitter unit support location 110 and the power sources 114a and 114b positioned in the power source support locations 108a and 108b, respectively, of the base 106 (FIG. 1D). In some embodiments, the power sources 114a or 114b may be batteries, storage capacitors, solar cells, generators, or the like. While two battery power sources 114a, 114b are shown in FIGS. 1C and 1E, it will be understood that fewer, more, and / or different power sources may be used. Furthermore, any suitable configuration of electrical contacts for securing and connecting the power sources 114a and 114b may be used.

[0056] The transmitter unit support location 110 is configured to hold the transmitter unit 104 coupled or otherwise attached to the disposable base unit 102 during continuous analyte monitoring. In some embodiments, the transmitter unit support location 110 may include one or more retention features 116a-116d that mate with and / or press against the transmitter unit 104 to maintain the connection between the transmitter unit 104 and the base 106, as shown, for example, in FIG. 1E . Fewer, more, and / or different retention features may be used to secure the transmitter unit 104 to the base 106. The retention features 116a-116d may include, for example, protrusions that engage openings in the transmitter unit 104, openings that engage protrusions in the transmitter unit 104, magnets, Velcro, adhesive-bearing surfaces, or any other suitable coupling mechanism. Optionally, a protrusion may be formed on the transmitter unit 104 and may be received within an opening formed in the transmitter unit support location 110 of the base.

[0057] In some embodiments, the transmitter unit support locations 110 may include tear locations 118 (FIGS. 1C, 1D, and 1E), such as channels, grooves, scribe lines, etc., that allow the base 106 to bend and / or break so that the retention features 116a-116d can be removed from and / or release the transmitter unit 104 when the transmitter unit 104 is removed from the disposable base unit 102 / base 106 for reuse with another disposable base unit. Other release and / or tear locations or mechanisms may be used.

[0058] A substrate 120, such as a circuit board, a flexible circuit board, or the like, may be located at least partially within the transmitter unit support location 110 and may include a connector 122 that provides an electrical interface for connecting to the transmitter unit 104. For example, the connector 122 may be electrically connected to the power sources 114a, 114b via conductive paths (not shown), allowing the power sources 114a, 114b to provide power to the transmitter unit 104 when the transmitter unit 104 is positioned within the transmitter unit support location 110. Such conductive paths may be formed in part on the substrate 120 and / or on the base 106.

[0059] The sensor assembly support location 112 provides a mounting and support location for an analyte sensor assembly, which may include, for example, an insertion device 124 and an insertion device cap 126. The insertion device 124 may include, for example, an insertion portion 128 coupled to a handle portion 130. The insertion portion 128 of the insertion device 124 has a sharpened end 131 (FIG. 1C) that pierces the skin to introduce the analyte sensor 132 into the subcutaneous region of the user, as described further below. The insertion portion 128 may also be referred to as an insertion shaft, needle, trocar, sharp, etc.

[0060] The insert portion 128 of the insert device 124 can be made from a metal, such as stainless steel, or a non-metal, such as plastic. Other materials may be used. In some embodiments, the insert portion 128 may be, but is not limited to, a round C-channel tube, a round U-channel tube, a pressed sheet metal part folded into a square U-shape, a molded / cast U-channel shape, a laser cut or machined metal part, or a solid metal cylinder with a square U-channel etched or polished into it. Other insert portion shapes may be used.

[0061] In some embodiments, the handle portion 130 of the insertion device 124 may be formed from a molded polymer (e.g., plastic), such as, but not limited to, acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, acetal, polyphthalamide (PPA), polysulfone, polyethersulfone, polyetheretherketone (PEEK), polypropylene, high density polyethylene (HDPE), low density polyethylene (LDPE), etc. Other suitable materials may be used.

[0062] The handle portion 130 may reside on an upper surface of the sensor assembly support location 112 of the base 106, while the insertion portion 128 may, for example, pass through a sensor opening 134 ( FIG. 1 ) in the sensor assembly support location 112 of the base 106. The analyte sensor 132 is electrically connected to the connector 122 of the transmitter unit support location 110, thereby electrically connecting the analyte sensor 132 to any transmitter units 104 positioned at the transmitter unit support location 110. The conductive path coupled to the connector 122 may further connect to the power sources 104 a, 104 b.

[0063] 1F shows an alternative side perspective view of the sensor 132 coupled to the connector 122 as the sensor 132 passes through the sensor opening 134 at the sensor assembly support location 112. As shown, a slot 135 may be provided in the sensor assembly support location 112 to facilitate connection of the sensor 132 to the connector 122. The connector 122 may be any suitable connector, such as an elastomeric connector having metal contacts or another connector type that electrically couples the analyte sensor 132 as well as the electrical conductors 123a, 123b that provide power from the power sources 104a, 104b.

[0064] 1A-1C, in some embodiments, the base 106 is sealed. For example, an encapsulation layer 136 (shown separately in FIG. 1C) may be formed over the base 106 and power sources 114a, 114b, as shown in FIGS. 1A-1B. In some embodiments, the encapsulation layer 136 may include an opening 138 formed therein through which the transmitter unit 104 can be attached and / or detached from the transmitter unit support location 110 of the base 106. In other embodiments, the transmitter unit 104 may sit on top of (or otherwise attached to) the encapsulation layer 136, as further described in FIGS. 1H-1I. In some embodiments, the encapsulation layer 136 forms a watertight seal around the base 106 and its internal components and seals against the sensor assembly support location 112 (leaving an opening 140 (FIG. 1C) for the insert device 124 to penetrate the base 106 and enter the insert device cap 126). The connector 122 may remain exposed within the transmitter unit support position 110 and the transmitter unit 104 may be electrically connected to the power sources 114a, 114b and the sensor 132 to provide power and a current signal from the sensor 132 to the transmitter unit 104, respectively.

[0065] The encapsulating layer 136 may be formed from a single layer or multiple layers. For example, the encapsulating layer 136 may be formed from one or more layers of liquid silicone rubber (LSR), thermoplastic elastomer (TPE), or the like. Other suitable casting or molding materials may be used. In some embodiments, the encapsulating layer 136 may be formed at temperatures below 100°C, and in some embodiments, below 80°C. In the embodiment of FIGS. 1A-C, the encapsulating layer 136 may be formed from two layers. For example, a bottom, pre-formed encapsulating layer 142 is provided, upon which the base 106 is positioned. The substrate 120 may be positioned in the transmitter unit support position 110 with the connector 122, and the sensor assembly components, such as the insertion device 124 and the sensor 132 (with the sensor 132 connected to the connector 122), may be positioned in the sensor assembly position 112. The power sources 114a and / or 114b may be positioned in the power source support positions 108a and / or 108b. An upper encapsulation layer 144 may then be formed over the base 106 and power supplies 114a, 114b, while leaving an opening 138 (or another mounting area) that allows the transmitter unit 104 to be attached to, detached from, inserted into, and / or removed from the base 106. Additional methods of assembling the disposable base unit 102 are further described below with reference to Figures 7-9.

[0066] 1G illustrates an alternative embodiment of the base 106 and transmitter unit 104 provided herein. In the embodiment of FIG. 1G, the transmitter unit 104 includes two retention features (only retention feature 150 is shown) that mate with corresponding retention features (only retention feature 152 is shown) on the base 106. Other numbers, types, and / or locations of retention features may be used.

[0067] The retention mechanism described herein secures the reusable transmitter unit 104 within the disposable base unit 102 during continuous analyte monitoring, while allowing the transmitter unit 104 to be removed and reused after the continuous analyte monitoring period. For example, the reusable transmitter unit 104 can be configured to mate with the disposable base unit 102 to receive power from the power supplies 114a and / or 114b of the disposable base unit 102. The disposable base unit 102 can be configured to be discarded after a single analyte monitoring period, while the reusable transmitter unit 104 can be configured to be removed from the disposable base unit 102 after a single analyte monitoring period and reused with another disposable base unit. In some embodiments, the single analyte monitoring period can be at least 7-10 days (e.g., up to 14 days or more). The transmitter unit 104 can be removed from the disposable base unit 102 and reused (e.g., 5, 10, 20, 50, 100 or more times) with a new disposable base unit, each time including a new sensor and a new power supply.

[0068] 1H and 1I show side views of an alternative embodiment of the wearable device 100 with the transmitter unit 104 attached to the disposable base unit 102 at an attachment area 154 of the encapsulation layer 136, according to embodiments provided herein. In such an embodiment, the transmitter unit 104 may be present, for example, on top of the encapsulation layer 136. In other embodiments, the transmitter unit 136 may be attached to an attachment area (not shown) on the bottom of the encapsulation layer 136.

[0069] 2 is an exploded view of an exemplary transmitter unit 104 according to embodiments provided herein. Referring to FIG. 2, the transmitter unit 104 may include a substrate 202 that couples to a top cover 204 before forming a bottom cover 206 (which may be, for example, an overmolded part) to cover and encapsulate the substrate 202 and any electrical or electronic components coupled or formed thereon. The substrate 202 may be a circuit board, a flexible circuit board, or another mounting location for electronic circuitry used within the transmitter unit 104.

[0070] In some embodiments, the transmitter unit 104 may include an analog front end 208 configured to apply a voltage to the analyte sensor 132 and detect a current through the analyte sensor 132. The transmitter unit 104 may also include a processing circuit 210 for processing the current signal detected by the analog front end 208 and transmitting the signal and / or information to an external device. For example, in some embodiments, the processing circuit 210 may convert the analog current signal to a digital current signal, store the current signal, calculate an analyte concentration value based on the current signal, transmit the current signal and / or the analyte concentration information to an external device (e.g., an external CGM device), etc. In some embodiments, the processing circuit 210 may include a processor such as a microcontroller or microprocessor, memory, an analog-to-digital converter, transmitter circuitry, etc. The analog front end 208 and the processing circuit 210 may perform other, fewer, and / or more functions.

[0071] In one exemplary CGM embodiment, processor circuit 210 may include a processor, memory coupled to the processor, and transmitter circuitry coupled to the processor. The memory may include computer program code stored therein that, when executed by the processor, causes transmitter unit 104 and wearable device 100 to (a) measure glucose signals using a glucose sensor; (b) calculate glucose values ​​from the measured glucose signals; and (c) cause wearable device 100 to communicate the glucose values ​​to a communicatively coupled external device, such as via Bluetooth or other wireless communication protocol. For example, a current detection circuit in transmitter unit 104 coupled to sensor 132 through connector 122 (and interface 212, described below) may measure a glucose (current) signal generated by sensor 132. A sampling circuit may be coupled to the current detection circuit and configured to generate digitized glucose signals from the measured glucose signals. These digitized glucose signals may then be used to determine glucose values ​​that are transmitted to the external CGM device for communication (e.g., display) to the user. Optionally, a raw signal can be transmitted and the external CGM device can generate a digitized glucose signal from the transmitted signal.

[0072] The substrate 202 may also include an interface 212 configured to mate with the connector 122 of the base unit 102 when the transmitter unit 104 is positioned in the transmitter unit support location 110 of the base 106. An opening 214 in the bottom cover 206 may be provided, for example, to allow the interface 212 to couple with the connector 122 of the base unit 102. In some embodiments, the analog front end 208 may be coupled to the sensor 132 through the interface 212 and the connector 122 of the base unit 102. Similarly, the analog front end 208 and the processing circuitry 210 may receive power from the power supplies 114a and / or 114b of the base unit 102 through the connector 122 and the interface 212.

[0073] In some embodiments, the top cover 204 may be a pre-formed base into which the substrate 202 is positioned prior to the formation (e.g., by a molding process) of the bottom cover 206. Alternatively, the bottom cover 206 may be a pre-formed base into which the substrate 202 is positioned prior to the formation or addition of the top cover 204. Other assembly processes may be used.

[0074] In some embodiments, the top cover 204 and / or the bottom cover 206 may be formed from a single layer or multiple layers. For example, the top cover 204 and / or the bottom cover 206 may be formed from one or more layers of liquid silicone rubber (LSR), thermoplastic elastomer (TPE), or the like. Other materials may be used, including, but not limited to, acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, acetal, polyphthalamide (PPA), polysulfone, polyethersulfone, polyetheretherketone (PEEK), polypropylene, high-density polyethylene (HDPE), and low-density polyethylene (LDPE). Other suitable materials may be used.

[0075] To avoid thereby damaging the electronics therein, in some embodiments, top cover 204 and / or bottom cover 206 may be formed at a temperature below 100° C., and in some embodiments, below 80° C. Top cover 204 and bottom cover 206 may encapsulate substrate 202, analog front end 208, and processing circuitry 210 (e.g., so that transmitter unit 104 is waterproof and only interface 212 is exposed).

[0076] In some embodiments, the bottom cover 206 may include a sealing member 216, such as a lip or similar feature, configured to seal against the sidewall of the opening 138 in the base unit 102 (see also FIG. 4E below), such that the transmitter unit 104 and the base unit 102 form a sealed unit when the transmitter unit 104 is positioned within the base unit 102. In some embodiments, the top cover 204 may include one or more retention features 218a-218d configured to mate with retention features (e.g., one or more of the retention features 116a-116d) in the transmitter unit support location 110. Such retention features securely couple and retain the transmitter unit 104 to the base unit 102 during use, maintaining the connector 122 in contact with the interface 212. In other embodiments, the top cover 204 may include a sealing member and / or the bottom cover 206 may include one or more retention features.

[0077] 3A is a cross-sectional side view of the wearable device 100 before inserting the transmitter unit 104 into the base unit 102, according to some embodiments. FIG. 3B is a cross-sectional side view of the wearable device 100 after inserting the transmitter unit 104 into the base unit 102, according to some embodiments. As mentioned above, both the transmitter unit 104 and the base unit 102 may be sealed units (e.g., waterproof), leaving only the interface 212 of the transmitter unit 104 and the connector 122 of the base unit 102 exposed. Once the transmitter unit 104 is inserted into the base unit 102, the connector 122 and the interface 212 may be sealed from any external environment, such as by a sealing member 216.

[0078] The transmitter unit 104 does not require a separate power source because it can receive power from the base unit 102 (through connector 122 and interface 212). Thus, when the disposable base unit 102 is replaced at the end of the analyte monitoring period, the transmitter unit 104 can be removed and reused with another new disposable base unit.

[0079] The base unit 102 and / or the transmitter unit 104 may be any suitable shape (e.g., circular, oval, square, rectangular, etc.). For example, FIGS. 4A and 4B show a top perspective view and an exploded perspective view, respectively, of an exemplary wearable device 400 provided herein. The wearable device 400 has a primarily rectangular shape and is sized and shaped similarly to a medical bandage. In this case, the base unit 102 is rectangular. The transmitter unit 104 may be any suitable shape. As with other embodiments described herein, the base unit 102 is disposable and the transmitter unit 104 is reusable. That is, in some embodiments, the base unit 102 is configured to be discarded after a single analyte monitoring period, while the transmitter unit 104 is configured to be detached from the base unit 102 and reused multiple times with another (new) base unit, which may be an exact copy of the base unit 102.

[0080] 4A and 4B, in some embodiments, a wearable device 400 may employ a sensor assembly 402 including one or more microneedles, such as the series of microneedles shown. Fewer or more microneedles may be used. The wearable device 400 includes a base member 404 having openings 405 through which the microneedles extend. The base member 404 may be formed from any suitable material, such as liquid silicone rubber (LSR), thermoplastic elastomer (TPE), acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, acetal, polyphthalamide (PPA), polysulfone, polyethersulfone, polyetheretherketone (PEEK), polypropylene, high-density polyethylene (HDPE), or low-density polyethylene (LDPE). Other suitable materials may be used. The base member 404 may include an adhesive, such as a pressure-sensitive adhesive 439 (see FIG. 4D), used to secure the wearable device 400 to the user's skin.

[0081] The sensor assembly 402, including the microneedle array, may be formed on a suitable substrate 406, such as plastic or a similar substrate, and may be attached to and electrically coupled to a circuit board 408 (e.g., a flexible circuit board) and the bottom member 404 by any suitable means, such as an adhesive. The power sources 114a and / or 114b may be coupled to the circuit board 408 via the base 106 and fittings 122, and may include suitable electrical contacts thereon configured to secure the power sources 114a and / or 114b and provide power to the circuit board 408. The base 106 may be received in an opening 440, as shown in FIG. 4E.

[0082] The circuit board 408 may include a connector 122 coupled to the microneedle array 402 and also coupled to the power sources 114a and / or 114b. The connector 122 is further configured to mate with the interface 212 of the transmitter unit 104 to provide power to the transmitter unit 104 when the transmitter unit 104 is installed in the base unit 102. Additionally, the connector 122 enables the transmitter unit 104 to bias the microneedle array 402 and detect current through one or more microneedles. The transmitter unit 104 may use the detected current to calculate the analyte level in the interstitial fluid, as described above.

[0083] Figure 4C shows a bottom perspective view of a wearable device 400 according to embodiments provided herein. Figure 4D shows a bottom view of an alternative embodiment of the wearable device 400 in which a single microneedle 412 is used and clear tape 439 is applied which is used to secure the wearable device to the user's skin. Figure 4E shows an enlarged portion of the wearable device 400 showing the transmitter unit 104 inserted into the base unit 102 and including the microneedle array 402 according to embodiments provided herein.

[0084] 4E, in some embodiments, the transmitter unit 104 may include a sealing member 216 (e.g., a sealing bead or lip) that interfaces with a receiving surface 414, such as a groove or similar feature, on the sidewall of the opening 138 in the base unit 102 (FIGS. 1C and 4E). In this manner, the base unit 102 and the transmitter unit 104 may form a sealed unit (e.g., protecting the connector 122 and / or interface 212 from liquids).

[0085] FIG. 4E also shows a cross-sectional side view illustrating how the retention features 416 on the base unit 102 can mate with corresponding retention features 418 on the transmitter unit 104 to securely hold the transmitter unit 104 within the opening 138 of the base unit 102. The retention features 416 and / or 418 shown can also ensure that the connector 122 is securely held within the interface 212 during use. Fewer or more retention features (e.g., two, three, four, or more, such as the aforementioned retention features 116a-116d) can be used. In some embodiments, the transmitter unit 104 can be used with base units having different shapes. For example, the transmitter unit 104 can be used with a circular base unit at one time and then reused with a rectangular base unit, or vice versa. FIG. 1E also shows that the base 106 is received within an opening 440 below the opening 138 and secured therein by the circuit board 408.

[0086] 5 is a flowchart of an exemplary method 500 for continuous analyte monitoring according to embodiments provided herein. Referring to FIG. 5, method 500 begins at block 502, in which a wearable device is provided having a disposable portion including a sensor and a power source, and a reusable portion coupled to the disposable portion, the reusable portion including a transmitter unit that receives power from the disposable portion. For example, wearable device 100 or 400 may be provided in which a disposable base unit 102 includes a sensor (e.g., an analyte sensor, microneedles, a microneedle array, etc.) and a power source (e.g., a battery or other power source). A reusable transmitter unit 104 may mate with and receive power from the disposable base unit 102.

[0087] In block 504, the sensor, power source, and transmitter unit are employed to monitor the user's analyte level. For example, after sensor 132 is inserted into the user, sensor 132, power sources 114a and / or 114b, and transmitter unit 104 may be employed to monitor the user's analyte level during a continuous analyte monitoring process (e.g., approximately 7-21 days). After analyte monitoring, the wearable device, including analyte sensor 132, may be removed from the user. In block 506, the reusable portion of the wearable device is detached from the disposable portion of the wearable device. For example, transmitter unit 104 may be detached from base unit 102, and the base unit 102 may be discarded. Generally, transmitter unit 104 may be detached from base unit 102 before or after base unit 102 is detached from the user. Thereafter, in block 508, the reusable portion of the wearable device is connected to a new disposable portion. For example, the transmitter unit 104 may be disconnected from the base unit 102 and inserted into or otherwise coupled to a new base unit 102 (e.g., having a new power supply and a new analyte sensor). In block 510, the new disposable portion's sensors and power supply and transmitter unit may be employed to monitor the user's analyte level. In some embodiments, the transmitter unit 104 may be used with at least 10 different sensors and power supplies. The transmitter unit 104 may be coupled to the base unit 102 before or after the base unit 102 is attached to the user.

[0088] FIG. 6 is a flowchart of another exemplary method 600 for continuous analyte monitoring according to embodiments provided herein. Referring to FIG. 6, method 600 begins at block 602, where a disposable base unit having a sensor and a power source (e.g., disposable base unit 102 having sensor 132) is provided. Then, at block 604, the sensor is inserted into a user's interstitial fluid region, and at block 606, the base unit is attached to the user (e.g., via adhesive on the bottom of the wearable device). At block 608, a reusable transmitter unit is coupled to the disposable base unit such that the reusable transmitter unit receives power from the power source and is coupled to the sensor (e.g., reusable transmitter unit 104 is attached to disposable base unit 102 and receives power and sensor signals through connector 122). The reusable transmitter unit 104 may be attached to the disposable base unit 102 before or after sensor 132 is inserted into the user's interstitial fluid region. In block 610, the transmitter unit and sensor are employed to monitor an analyte level in a user for a first predetermined period of time. For example, the transmitter unit 104 and sensor 132 may be used to monitor glucose or another analyte level for 7 days, 10 days, 14 days, or another number of days.

[0089] After a first predetermined time, the method 600 includes removing the disposable base unit with the sensor from the user (block 612) and disconnecting (detaching) the reusable transmitter unit from the disposable base unit (block 614). For example, the transmitter unit 104 can be disconnected from the base unit 102, and the base unit 102 can be discarded. The reusable transmitter unit 104 can be disconnected from the disposable base unit 102 before or after the disposable base unit 102 and sensor 132 are removed from the user. In block 616, the sensor of a new disposable base unit can be inserted into the interstitial fluid region of the user. In block 618, the new disposable base unit can be attached to the user. In block 620, the reusable transmitter unit can be coupled to a new disposable base unit such that the transmitter unit receives power from the new disposable base unit and is coupled to the sensor of the new disposable base unit. The reusable transmitter unit 104 may be attached to a new disposable base unit 102 before or after the sensor 132 is inserted into the user's interstitial fluid region. In block 622, the transmitter unit and sensor of the new disposable base unit may be employed to monitor analyte levels in the user for a second predetermined period of time. For example, the transmitter unit 104 and new disposable base unit 102 may be used for an additional 7, 10, 14, or other number of days. As described above, the transmitter unit 104 may be used 10, 20, 50, 100, or more times (each time with a new disposable base unit).

[0090] FIG. 7 is a flowchart of one exemplary method 700 for forming a wearable device for use during continuous analyte monitoring, as provided herein. Referring to FIG. 7 , in block 702, a pre-formed portion is provided (e.g., a pre-formed encapsulation layer 142). For example, liquid silicone rubber (LSR), thermoplastic elastomer (TPE), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM), polycarbonate, high durometer silicone, or another suitable material may be placed within a molding tool. The pre-formed portion 142 may be employed to secure or otherwise support components of the wearable device in place prior to molding (e.g., overmolding). In block 704, a base is placed on the pre-formed portion, the base having a transmitter unit support location and a sensor assembly support location. For example, the base 106 may be placed on the pre-formed portion 142. At block 706, at least one power source is placed on the pre-molded portion. In some embodiments, power sources 114a and / or 114b may be placed directly on pre-molded portion 142, while in other embodiments, power sources 114a and / or 114b may be placed on power source support locations 108a and / or 108b of base 106. In some embodiments, at block 708, a sensor assembly including an analyte sensor may be placed in the sensor assembly support location. In other embodiments, a dummy insertion device shaped similarly to insertion device 124 may be placed in the sensor assembly support location (before molding) to protect the sensor and ensure that opening 140 in insertion device 124 is properly formed. If a dummy insertion device is employed, it may be removed after molding, and insertion device 124 may be placed in opening 140. Placing the sensor assembly in sensor assembly support location 112 may include placing connector 122 in transmitter unit support location 110 and connecting connector 122 to sensor 132. The connector 122 may also be connected to the power sources 114a and / or 114b, as previously described.

[0091] At block 710, an encapsulation layer is formed that extends over the base and at least one power source, sealing it against the pre-molded part. During encapsulation layer formation, mounting areas (e.g., openings 138, mounting areas 154) are provided that allow transmitter units to be mounted and removed from transmitter unit support locations on the base in the mounting areas of the encapsulation layer. This may be accomplished, for example, by using a dummy transmitter unit placed in transmitter unit support location 110 on base 106 prior to molding.

[0092] In some embodiments, the encapsulating layer may be formed at a temperature of less than 100° C., and in some embodiments, less than 80° C. Exemplary polymeric materials for the encapsulating layer may include, for example, liquid silicone rubber (LSR), thermoplastic elastomer (TPE), and the like.

[0093] An encapsulating layer (e.g., encapsulating layer 136) forms a sealed disposable base unit (base unit 102) that can receive the transmitter unit 104 prior to use. After the encapsulating layer is formed, an adhesive layer is provided on the bottom of the pre-formed portion and is used to secure the base unit 102 to a user during continuous analyte monitoring with the wearable device. The disposable base unit 102, including the insertion device and sensor assembly, can then be sterilized and packaged for use (e.g., separated from the transmitter unit 104). For example, e-beam sterilization or another sterilization method can be used to sterilize the various components of the disposable base unit 102, such as the sensor 132, insertion device 124, and insertion device cap 126. An example packaging 1650 can include a plastic housing 1650H with a removable plastic or foil seal, or other sealing cover 1650C as shown in FIG. 16, to seal the sterilized disposable base unit 102, although any suitable sterile packaging can be used. In another example, a sterilized disposable base unit 102 may be received and sealed in a housing of laminated foil and plastic sheet 1750, as shown in Figure 17. The wearable device may be employed by removing the sterilized base unit from its sterile packaging, inserting the reusable transmitter unit 104 into the base unit 102, removing the adhesive strip from the bottom of the base unit 102, and inserting the sensor 132 into the user while attaching the base unit 102 to the user's skin. Any suitable insertion device may be used to insert the sensor 132 into the interstitial fluid region of the user.

[0094] FIG. 8 is a flowchart of another exemplary method 800 of forming a wearable device for use during continuous analyte monitoring provided herein. Referring to FIG. 8 , in block 802, at least one power source and sensor assembly is coupled to a connector (e.g., power sources 114a and / or 114b can be coupled to connector 122, as can sensor 132). In block 804, the at least one power source, sensor assembly, and connector are placed within a molding tool. In some embodiments, a sensor assembly including an insertion device and an analyte sensor can be placed in a sensor assembly support position of base 106. In other embodiments, a dummy insertion device shaped similarly to insertion device 124 can be placed within the sensor assembly support position (before molding) to protect sensor 132 and ensure that opening 140 in insertion device 124 is properly formed. If a dummy insertion device is employed, the dummy insertion device can be removed after molding, and insertion device 124 can be placed within opening 140.

[0095] At block 806, the base, at least one power source, and at least a portion of the sensor assembly are encapsulated using a molding tool to form a sealed unit. Such encapsulation includes forming mounting areas (e.g., 138) within the sealed unit that allow the transmitter unit 104 to be attached to and removed from the transmitter unit support location 110 of the base 106. This may be accomplished, for example, by using a dummy transmitter unit placed at the transmitter unit support location 110 of the base 106 during molding.

[0096] In some embodiments, encapsulating the base 106 and the at least one power source 114a, 114b may be performed at temperatures below 100° C., and in some embodiments, below 80° C. Exemplary materials for encapsulating the base 106 and the at least one power source 114a, 114b include liquid silicone rubber (LSR), thermoplastic elastomer (TPE), etc. Other suitable encapsulating materials may be used.

[0097] Encapsulating the base 106 and power sources 114a, 114b forms a sealed disposable base unit (e.g., base unit 102) that can receive the transmitter unit 104 prior to use. After formation of the disposable base unit 102, an adhesive layer is provided on the bottom of the base unit 102 and can be used to secure the base unit 102 to a user during continuous analyte monitoring with the wearable device. The disposable base unit can then be sterilized and packaged for use (e.g., separately from the transmitter unit) as described above.

[0098] FIG. 9 is a flowchart of another exemplary method 900 of forming a wearable device for use during continuous analyte monitoring provided herein. Referring to FIG. 9 at block 902, a base (see, e.g., base 106 in FIGS. 3A-3B ) has a transmitter unit support location (e.g., transmitter unit support location 110), a power source support location (e.g., power source support locations 108a, 108b), and a sensor assembly support location (e.g., sensor assembly support location 112). In block 904, at least one power source (e.g., power source 114a, 114b) is disposed in the power source support location (e.g., power source support location 108a, 108b) of the base (e.g., base 106). In block 906, a sensor assembly including an analyte sensor (e.g., analyte sensor 132) and / or an insertion device (e.g., insertion device 124) can be disposed in the sensor assembly support location (e.g., sensor assembly support location 112). Placing the sensor assembly in the sensor assembly support location 112 may include placing the connector 122 in the transmitter unit support location 110 and connecting the connector 122 to the sensor 132. The connector 122 may also be connected to the power sources 114a and / or 114b as described herein.

[0099] In block 908, an encapsulating portion (e.g., encapsulating portion 136) is provided having an opening (e.g., opening 340) in base 106. For example, a liquid silicone rubber (LSR), thermoplastic elastomer (TPE), thermoset or thermoplastic polymer, or similar encapsulating portion 136 is provided and includes opening 440 formed therein, thereby allowing base 106 to be inserted into opening 440 of encapsulating portion 136. At least one power source (e.g., power sources 114a, 114b) and / or sensor assembly (e.g., 132) may be coupled to base 106.

[0100] In block 910, the base (e.g., the base 106 having at least one power source 114a, 114b, and the sensor assembly 132 coupled thereto) is placed within the opening 340 of the encapsulating portion 136. In this embodiment, the base 106 may be sealed to the opening 340, and an edge of the base 106 may be sealed to the encapsulating portion 136 such that the base 106 and the encapsulating portion 136 form a sealed disposable unit. The sealed disposable unit is configured so that the transmitter unit 104 can be attached to and removed from the transmitter unit support location 110 of the base 106. In some embodiments, the insertion device 124 and / or insertion device cap 126 can be coupled to the base unit 102 after the base is inserted into a pre-molded portion including the encapsulating portion 136.

[0101] Placing the base 106, sensor 132, and power sources 114a, 114b within the encapsulation portion 136 forms a sealed disposable base unit (e.g., base unit 102) that can receive the transmitter unit 104 prior to use. After forming the disposable base unit 102, an adhesive layer is provided on the bottom of the base unit 102 and can be used to secure the base unit 102 to a user during continuous analyte monitoring with the wearable device 100. Thereafter, in block 912, the disposable unit (e.g., base unit 102) can be sterilized and packaged for use (e.g., separately from the transmitter unit) as described above.

[0102] The wearable devices described herein can be used to monitor the analyte concentration of any desired analyte. Exemplary analytes that can be detected include glucose, cholesterol, lactate, uric acid, alcohol, and the like. In some embodiments, the sensor 132 and / or sensor assembly 402 (e.g., a microneedle array) can be continuously operated at a constant potential relative to a reference electrode, such as an Ag / AgCl electrode or a composite reference counter electrode. The sensor 132 and / or sensor assembly 402 can operate with two working electrodes, one dedicated to measuring a specific point-of-interest analyte, such as glucose, using a glucose-specific enzyme such as glucose oxidase. The other electrode is dedicated to measuring background signals resulting from interfering species, such as uric acid, acetaminophen, or the like. In this dual-electrode operating scheme, the interfering signal can be continuously subtracted from the main signal of the point-of-interest analyte by either simple subtraction or another algorithmic method.

[0103] 10A shows a high-level block diagram of an exemplary continuous analyte monitoring (CAM) device 1000 according to embodiments provided herein. While not shown in FIG. 10A , it will be understood that various electronic components and / or circuits are configured to couple to a power source, such as, but not limited to, a battery. The CAM device 1000 includes a bias circuit 1002 that can be configured to couple to a CAM sensor 1004. The bias circuit 1002 can be configured to apply a bias voltage, such as a continuous DC bias, to the analyte-containing fluid through the CAM sensor 1004. In this exemplary embodiment, the analyte-containing fluid can be human interstitial fluid, and the bias voltage can be applied to one or more electrodes 1005 (e.g., a working electrode, a background electrode, etc.) of the CGM sensor 1004.

[0104] In some embodiments, the CAM sensor 1004 may include two electrodes, and a bias voltage may be applied across the pair of electrodes. In such cases, a current may be measured through the CAM sensor 1004. In other embodiments, the CAM sensor 1004 may include three electrodes, such as a working electrode, a counter electrode, and a reference electrode. In such cases, a bias voltage may be applied between the working electrode and the reference electrode, and a current may be measured, for example, through the working electrode. The CAM sensor 1004 may include chemicals that react with an analyte (e.g., glucose) in a reduction-oxidation reaction, affecting the concentration of charge carriers and the time-dependent impedance of the CAM sensor 1004. Exemplary chemicals for glucose reactions include glucose oxidase, glucose dehydrogenase, etc. In some embodiments, mediators such as ferricyanide or ferrocene for glucose reactions may be employed. In some embodiments, the CAM sensor 1004 may include a sensor assembly including a microneedle or a plurality of microneedles, such as a microneedle array.

[0105] The bias voltage generated and / or applied by bias circuit 1002 may be, for example, in the range of about 0.1 to 1 volt relative to a reference electrode. Other bias voltages may be used.

[0106] The current flowing through the CAM sensor 1004 in the analyte-containing fluid in response to the bias voltage is measured as a current (I meas) circuit 1006 (also referred to as a current detection circuit). The current measurement circuit 1006 may be configured to detect and / or record (e.g., using a suitable current-to-voltage converter (CVC), etc.) an amperometric signal having a magnitude indicative of the magnitude of the current transmitted from the CAM sensor 1004. In some embodiments, the current measurement circuit 1006 may include a resistor having a known nominal value and a known nominal accuracy (e.g., in some embodiments, 0.1% to 5%, or even less than 0.1%) through which the current transmitted from the CAM sensor 1004 passes. The voltage developed across the resistor in the current measurement circuit 1006 represents the magnitude of the current and is used to generate an amperometric signal (or raw analyte (e.g., glucose) signal Signal Raw )

[0107] In some embodiments, sample circuit 1008 may be coupled to current measurement circuit 1006 and configured to sample the current measurement signal to generate digitized time-domain sample data representing the current measurement signal (e.g., a digitized glucose signal). For example, sample circuit 1008 may be any suitable A / D converter circuit configured to receive the analog current measurement signal and convert it into a digital signal having a desired number of bits as an output. In some embodiments, the number of bits output by sample circuit 1008 may be 16 bits, although more or fewer bits may be used in other embodiments. In some embodiments, sample circuit 1008 may sample the current measurement signal at a sampling rate in the range of about 10 samples per second to 1000 samples per second. Faster or slower sampling rates may be used. For example, a sampling rate of about 10 kHz to 100 kHz may be used to downsample and further reduce the signal-to-noise ratio. Any suitable sampling circuit may be employed.

[0108] 10A , the processor 1010 may be coupled to the sample circuit 1008 and may further be coupled to a memory 1012. In some embodiments, the processor 1010 and the sample circuit 1008 are configured to communicate directly with each other via a wired path (e.g., via a serial or parallel connection). In other embodiments, the coupling between the processor 1010 and the sample circuit 1008 may be by way of the memory 1012. In this arrangement, the sample circuit 1008 writes digital data to the memory 1012, and the processor 1010 reads digital data from the memory 1012.

[0109] The memory 1012 may store therein one or more gain functions 1014 for use in determining a corrected glucose value based on the raw glucose signal (from the current measurement circuit 1006 and / or the sample circuit 1008). For example, in some embodiments, three or more gain functions may be stored in the memory 1012 for use with data collected at the CAM for different segments (periods). The memory 1012 may also store a plurality of instructions therein. In various embodiments, the processor 1010 may be a computational resource such as, but not limited to, a microprocessor, a microcontroller, an embedded microcontroller, a digital signal processor (DSP), a field programmable gate array (FPGA) configured to operate as a microcontroller, or the like.

[0110] In some embodiments, the instructions stored in memory 1012 include instructions that, when executed by processor 1010, cause processor 1010 to (a) cause CAM device 1000 to measure an analyte signal (e.g., a current signal) from interstitial fluid (via bias circuit 1002, CAM sensor 1004, current measurement circuit 1006, and / or sample circuit 1008); (b) store the analyte signal in memory 1012; (c) calculate an analyte value (e.g., concentration) based on the measured and / or stored analyte signal; and (e) communicate the analyte value to a user.

[0111] The memory 1012 may be any suitable type of memory, such as, but not limited to, one or more of volatile memory and / or nonvolatile memory. Volatile memory may include, but is not limited to, static random access memory (SRAM) or dynamic random access memory (DRAM). Nonvolatile memory may include, but is not limited to, electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory (e.g., EEPROM types in either NOR or NAND configurations, and / or in either stacked or planar arrangements, and / or in either single-level cell (SLC), multi-level cell (MLC), or combined SLC / MLC arrangements), resistive memory, filamentary memory, metal oxide memory, phase-change memory (e.g., chalcogenide memory), or magnetic memory. The memory 1012 may be packaged, for example, as a single chip or as multiple chips. In some embodiments, memory 1012 may be incorporated with one or more other circuits in an integrated circuit, such as, for example, an application specific integrated circuit (ASIC).

[0112] As mentioned above, memory 1012 may have a plurality of instructions stored therein that, when executed by processor 1010, cause processor 1010 to perform various operations specified by one or more of the stored instructions. Memory 1012 may further have a portion reserved for one or more "scratchpad" storage areas that may be used for read or write operations by processor 1010 responsive to execution of one or more of the instructions.

[0113] 10A , bias circuit 1002, CAM sensor 1004, current measurement circuit 1006, sample circuit 1008, processor 1010, and memory 1012 may be located within a wearable sensor portion 1016 of CAM device 1000 (e.g., wearable device 100 or 400 described above). In some embodiments, wearable sensor portion 1016 may include a display 1017 for displaying information such as analyte concentration information (e.g., without the use of an external device). Display 1017 may be any suitable type of motion-sensitive display, such as, but not limited to, a liquid crystal display (LCD), a light-emitting diode (LED) display, or an organic light-emitting diode (OLED) display.

[0114] In some embodiments, all of the electronic circuitry in the CAM device 1000 may be housed within a reusable transmitter unit (e.g., reusable transmitter unit 104) described herein, such as bias circuit 1002, current measurement circuit 1006, sample circuit 1008, processor 1010, memory 1012, transmitter / receiver circuit 1024a and / or display 1017. The CAM sensor 1004 and any power source may be located within a disposable base unit (e.g., disposable base unit 102).

[0115] 10A , the CAM device 1000 may further include a portable user equipment portion 1018. The processor 1020 and the display 1022 may be disposed within the portable user equipment portion 1018. The display 1022 may be coupled to the processor 1020. The processor 1020 may control text or images shown by the display 1022. The wearable sensor portion 1016 and the portable user equipment portion 1018 may be communicatively coupled. In some embodiments, the communicative coupling of the wearable sensor portion 1016 and the portable user equipment portion 1018 may be by wireless communication via transmitter circuitry and / or receiver circuitry, such as, for example, transmit / receive circuit TxRx 1024a of the wearable sensor portion 1016 and transmit / receive circuit TxRx 1024b of the portable user equipment portion 1018. Such wireless communication may be by any suitable means, including, but not limited to, a standards-based communication protocol such as the Bluetooth® communication protocol. In various embodiments, wireless communication between the wearable sensor portion 1016 and the portable user device portion 1018 may alternatively be by near field communication (NFC), radio frequency (RF) communication, infrared (IR) communication, or optical communication. In some embodiments, the wearable sensor portion 1016 and the portable user device portion 1018 may be connected by one or more wires.

[0116] Display 1022 may be any suitable type of human-sensitive display, such as, but not limited to, a liquid crystal display (LCD), a light-emitting diode (LED) display, or an organic light-emitting diode (OLED) display.

[0117] 10B, an exemplary CAM device 1050 is shown that is similar to the embodiment shown in FIG. 10A but has a different division of components. In CAM device 1050, wearable sensor portion 1016 includes bias circuit 1002 coupled to CAM sensor 1004 and current measurement circuit 1006 coupled to CAM sensor 1004. Portable user device portion 1018 of CAM device 1050 includes sample circuit 1008 coupled to processor 1020 and display 1022 coupled to processor 1020. Processor 1020 is further coupled to memory 1012 having gain function 1014 stored therein. In some embodiments, processor 1020 in CAM device 1050 may also perform the functions described above, for example, performed by processor 1010 of CAM device 1000 of FIG. 10A. The wearable sensor portion 1016 of the CAM device 1050 may be smaller, lighter, and therefore less invasive than the CAM device 1000 of FIG. 10A because it does not include the sample circuit 1008, processor 1010, memory 1012, etc. Other component configurations may be employed. For example, as a variation of the CAM device 1050 of FIG. 10B, the sample circuit 1008 may remain on the wearable sensor portion 1016 (such that a portable user device 1018 receives the digitized analyte (e.g., glucose) signal from the wearable sensor portion 1016).

[0118] While in some embodiments, the transmitter unit 104 is shown as being removable and / or insertable into the top surface of the base unit 102, it will be understood that in other embodiments, the transmitter unit 104 is removable and / or insertable into other surfaces of the base unit 102. For example, FIG. 11 shows a bottom perspective view of the base unit 102 having an opening 1102 that allows the transmitter unit 104 to be inserted into or removed from the base unit 102, according to some embodiments, as described above. The transmitter unit 104, in some embodiments, may receive power and analyte signals (e.g., analyte current signals) from the base unit 102. An adhesive layer 1104 may be provided on the bottom of the base unit 102 so that the wearable device 100 formed by the base unit 102 and the transmitter unit 104 can be secured to the user's skin. An opening 1106 in the adhesive layer 1104 allows the transmitter unit 104 to be inserted into and removed from the base unit 102.

[0119] Figure 12A shows a top perspective view of another embodiment of a wearable device 100 for use during continuous analyte monitoring according to embodiments provided herein. Figure 12B shows a top view of the base unit 102 of Figure 12A without the insertion device 124, transmitter unit 104, or power sources 114a and 114b installed according to embodiments provided herein. Figure 12C shows a perspective side view of the wearable device 100 of Figure 12A according to embodiments provided herein.

[0120] 12A and 12B, the wearable device 100 may be formed by placing the base 106 (not specifically shown) on a pre-formed encapsulating layer 142 and forming a top encapsulating layer 144 on the base 106. FIG. 12B illustrates that during the formation of the top encapsulating layer 144, e.g., by molding, an opening 138 is formed in the transmitter unit 104, an opening 140 is formed in the insert device 124, openings 1202a and 1202b are formed for the power sources 114a and 114b, respectively, and recesses 1204 are formed in the cover 1206 for the power sources 114a and 114b (see FIG. 12C). In some embodiments, the cover 1206 may couple to and / or become part of the transmitter unit 104 and snap, pivot, and / or hinge into the recesses 1204 when the transmitter unit 104 is placed in the opening 138 of the disposable base unit 102. In other embodiments, cover 1206 may be separate from transmitter 104. Cover 1206, when positioned over power supplies 114a and 114b, may form part of encapsulation layer 136 (e.g., along with pre-formed encapsulation layer 142 and upper encapsulation layer 144). Cover 1206 may be formed from, for example, liquid silicone rubber (LSR), thermoplastic elastomer (TPE), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyoxymethylene (POM), polycarbonate, high durometer silicone, or another suitable material.

[0121] After forming the base unit 102 having openings 138, 140, openings 1202a and 1202b, and recess 1204, power supplies 114a and 114b can be attached to openings 1202a and 1202b, and the insert device 124 can be attached to opening 140. The base unit 102 can then be sterilized, such as by using e-beam sterilization, for use with the transmitter unit 104 during continuous analyte monitoring, as described above. The dummy transmitter unit, insert device 124, power supplies 114a and 114b, and / or cover 1206 can be employed, such as provided as mold inserts, during formation of the upper encapsulation layer 144, such that openings 138, 140, 1202a and 1202b, and recess 1204 are formed.

[0122] In some embodiments, openings 1202a and 1202b may include electrical connections 1208a, 1208b that couple power sources 114a and 114b to connector 122 provided in opening 138 to provide power to transmitter unit 104 inserted into opening 138. Connector 122 may also include electrical connection 1208c configured to couple to an analyte sensor inserted by insertion device 124 during use of wearable device 100, as described above.

[0123] 13A and 13B are top views of another example of a disposable base unit 102 according to embodiments provided herein. Referring to FIG. 13A, as previously described, the disposable base unit 102 includes a mounting area 1310 configured to couple and detach the transmitter unit 104 to and from the disposable base unit 102 (for receiving power and connecting to the analyte sensors). The mounting area 1310 includes a connector position 1312 where the connector 122 (FIG. 13B) may be located, and power supply positions 1314a, 1314b where one or more power sources, such as one or more batteries, may be located. As shown in FIG. 13B, the connector 122 (FIG. 13) and power supplies 114a, 114b may be located in the connector position 1312 and power supply positions 1214a, 1214b, respectively. When the transmitter unit 104 is positioned in the mounting area 1310, it may form a watertight seal with the base unit 102 such that the connector 122 and power supplies 114a, 114b are hermetically sealed and / or encapsulated.

[0124] 13A and 13B, the wearable device 100 (FIG. 13B) may be formed by providing a pre-formed encapsulation layer 142 and forming an upper encapsulation layer 144 having a connector location 1312 and power supply areas 1314a, 1314b (as well as an attachment location 1310, such as an opening or recess) formed therein. As shown in FIG. 13A, during the formation of the upper encapsulation layer 144, the attachment area 1310 is formed for the transmitter unit 104, the opening 140 is formed to receive the insertion device 124, the connector location 1310 is formed for the connector 122, and the openings 1314a and 1314b are formed to receive the power sources 114a and 114b.

[0125] After forming base unit 102 having mounting area 1310, connector position 1312, opening 140, and power supply positions 1314a and 1314b, connector 122 can be placed in connector position 1312, power supplies 114a and 114b can be attached to power supply positions 1314a and 1314b, and insertion device 124 can be attached to opening 140. Power supplies 114a, 114b can be coupled to connector 122, with an analyte sensor (e.g., sensor 132 shown in dotted lines) extending into opening 140 and coupling with insertion device 124.

[0126] The base unit 102 may then be sterilized for use with the transmitter unit 104 during continuous analyte monitoring as described above. A die plug or insert or dummy transmitter unit, insertion device, power supply, and / or inserter may be used during formation (e.g., molding) of the upper encapsulation layer 144 so that the mounting locations 1310, connector locations 1312, openings 140, and power supply locations 1314a and 1314b are properly formed.

[0127] 14, a method 1400 of forming a wearable device adapted for use in continuous analyte monitoring (e.g., wearable device 100) includes, at block 1402, forming an encapsulation layer (e.g., encapsulation layer 136) having a connector location, at least one power source location, and an inserter opening formed therein (e.g., connector location 1312, power source locations 1314a, 1314b, and opening 140). Method 1400 further includes, at block 1404, disposing a connector (e.g., connector 122) in the connector location, and, at block 1406, disposing at least one power source (e.g., power source 114a and / or 114b); in the at least one power source location (e.g., power source locations 1314a, 1314b). Disposing connector 122 may be by any suitable method for achieving electrical connection to the at least one power source (e.g., power source 114a and / or 114b), and may include a pin connector and / or a solder connection. At block 1408, method 1400 includes coupling at least one power source (e.g., power source 114a and / or 114b) to the connector (e.g., connector 122), such as through an electrical connection between connector 122 and the at least one power source (e.g., power source 114a and / or 114b). Method 1400 includes coupling an analyte sensor (e.g., sensor 132, shown in dotted lines) to the connector (e.g., connector 122), at block 1410. Coupling connector 122 may be by any suitable method for achieving an electrical connection between connector 122 and the analyte sensor (e.g., sensor 132, shown in dotted lines), and may include a pin connector and / or a solder connection. The encapsulation layer (e.g., encapsulation layer 136), the connector (e.g., connector 122), at least one power source (e.g., power source locations 114a, 114b), and the analyte sensor (e.g., sensor 132) form a disposable unit configured to mate with a reusable transmitter unit (e.g., reusable transmitter unit 104) to form a sealed unit (e.g., the sealed unit of base unit 102 and reusable transmitter unit 104 in FIG. 13B).

[0128] In some embodiments, a method 1500 is provided for forming a wearable device (e.g., wearable device 100 of FIGS. 12A-12C) configured for use in continuous analyte monitoring, for example, as shown in the flowchart of FIG. 15. The method 1500 includes, at block 1502, providing a pre-formed part (e.g., pre-formed encapsulating layer 142); at block 1504, placing a base (e.g., base 106) on the pre-formed part, the base having a transmitter unit support position (e.g., transmitter unit support position 1210) and a sensor assembly support position (e.g., sensor assembly support position 112); and, at block 1506, placing a sensor assembly including an analyte sensor (e.g., sensor 132) at the sensor assembly support position (e.g., sensor support position 112); and, at block 1508, forming an encapsulating layer (e.g., encapsulating layer 144) extending over the base (e.g., base 106) and sealing it to the pre-formed part (pre-formed encapsulating layer 142).

[0129] Forming the top encapsulation layer 144 may include forming an attachment region (e.g., opening 138 or region 154) that allows a transmitter unit (e.g., transmitter unit 104 of FIG. 12A ) to be attached to and detached from the transmitter unit support position 1210 of the base 106, such as being attached to and detached from the transmitter unit support position 1210 (and connector 122). Forming the top encapsulation layer 144 may include forming an opening (e.g., openings 1202a and / or 1202b) for at least one power source (inserted into the top encapsulation layer 144 to provide power to the transmitter unit 104 attached to the transmitter unit support position 1210). Method 1500 may also include forming a connector (e.g., connector 122) in the transmitter unit support position 1210 and coupling an analyte sensor (e.g., analyte sensor 132) to the connector (e.g., connector 122). The encapsulation layer, the connector, the at least one power source 114a, 114b, and the analyte sensor 132 form a disposable unit 102 configured to mate with a reusable transmitter unit to form the sealed wearable device 100.

[0130] In some embodiments, wearable devices for use during continuous analyte monitoring are formed at temperatures below 100° C., and in some embodiments, below 80° C. The wearable device may include a disposable base unit having a power source and a reusable transmitter unit having electronics for the wearable device. The transmitter unit receives power only from the disposable base unit to which it is coupled and may not have a separate power source.

[0131] In some embodiments, thumbnail grooves, tabs, or other gripping or prying mechanisms may be provided on the transmitter unit 104 and / or base unit 102 to facilitate removal of the transmitter unit 104 .

[0132] In one or more embodiments, a wearable device for continuous analyte monitoring (e.g., wearable device 100 or 400) may include a disposable base unit (e.g., base unit 102) that mates with a reusable transmitter unit (e.g., transmitter unit 104). The disposable base unit may include a power source and an analyte sensor and may be configured to receive the reusable transmitter unit. The reusable transmitter unit may include all electronic circuitry for biasing the analyte sensor, measuring current through the analyte sensor, calculating an analyte value based on the measured current through the analyte sensor, and communicating the analyte value to a user (directly or via an external device). The disposable base unit may be configured to receive the reusable transmitter unit and provide power to the electronic circuitry of the reusable transmitter unit. The disposable base unit may be sterilized and packaged separately from the reusable transmitter unit.

[0133] The sensor assembly may include one or more of a sensor, electrical leads extending from the sensor, and / or an insertion device used to insert the sensor (e.g., a sensor, a sensor and electrical leads, a sensor and insertion device, a sensor, electrical leads and an insertion device, etc.).

[0134] According to the present disclosure, a method for forming a wearable continuous analyte monitoring device is provided, as best shown in FIG. 18 . Method 1800 includes, at block 1802, providing a base having a power source support location, a sensor assembly support location, and a transmitter unit support location, and, at block 1804, positioning at least one power source at the power source support location. Method 1800 further includes, at block 1806, placing a sensor assembly including an analyte sensor at the sensor assembly support location. At block 1808, method 1800 includes providing an encapsulation layer over the at least one power source, at least a portion of the sensor assembly, and at least a portion of the base to form a sealed disposable unit, the sealed disposable unit configured to allow the transmitter unit to be attached to and detached from the transmitter unit support location. Finally, method 1800 includes, at block 1810, sterilizing the sealed disposable unit. Sterilization may be achieved as disclosed herein.

[0135] The embodiments provided herein enable flexible, ultra-thin continuous analyte monitoring systems. In some embodiments, the system height can be less than about 2.5 mm. This reduction in overall height can reduce contact with clothing, making it more discreet and improving the overall system fit. Flexible structures and components allow the sensor system to conform to the user's body during various activities, helping to enhance overall user comfort. Critical components can be supported by rigid reinforcements in specific locations while maintaining overall flexibility. The power source used can be formed from thin, bendable materials, such as multiple batteries arranged in parallel.

[0136] In some embodiments, the materials used (e.g., LSR), flexible circuit boards, etc. provide a device that can be comfortably worn under clothing, is thin, avoids impact, presents a soft, flexible feel and appearance, and conforms and moves with the dynamics of tissue flexion, expansion, and contraction. The disclosed devices also protect the sensor site and internal hardware from fluid intrusion and other usage hazards, are easy and comfortable to apply, provide breathability / airflow in the skin-adhering areas, and generally create a more user-friendly experience.

[0137] Flexible circuit boards can be used to support electronic components such as analog front-end circuits and transmitter modules. Flexible circuit boards can be made from materials such as copper, Kapton, polyester (PET), polyethylene naphthalate (PEN), polyimide, fiberglass, acrylic adhesives, etc. Flexible circuit boards can include electronic components in the form of printed circuits and electronic components.

[0138] Exemplary power sources include coin cells such as flexible lithium polymer batteries, lithium manganese, silver oxide, and alkaline coin cells (e.g., CR2032, SR516, and LR60 type coin cells). Other circuit board and / or power source types may be used.

[0139] The foregoing description discloses only exemplary embodiments. Modifications of the above-disclosed apparatus and methods that fall within the scope of this disclosure will be readily apparent to those of ordinary skill in the art.

Claims

1. 1. A continuous analyte monitoring wearable device comprising: A base unit comprising: a base, at least one power source, and an analyte sensor assembly; and a base unit including an enclosure extending over the base and the at least one power source to form an enclosed base, the enclosure including a mounting area configured to allow a reusable transmitter unit to be coupled to and detached from the enclosed base; the reusable transmitter unit is configured to receive power from the at least one power source and to connect to the analyte sensor assembly when coupled to the mounting region; the base includes a transmitter unit support location configured to receive the reusable transmitter unit; the base includes a base opening configured to receive the reusable transmitter unit in the transmitter unit support location through the base opening; A continuous analyte monitoring wearable device, wherein the base opening is provided on a surface configured to be adjacent to a user's skin in use.

2. The continuous analyte monitoring wearable device of claim 1 , wherein the base includes a sensor assembly support location configured to receive the analyte sensor assembly.

3. The continuous analyte monitoring wearable device of claim 1 , wherein the base includes a power source support location configured to receive the at least one power source.

4. The continuous analyte monitoring wearable device of claim 1 , wherein the attachment area has the reusable transmitter unit coupled thereto.

5. The continuous analyte monitoring wearable device of claim 1 , wherein the base unit includes a connector configured to electrically connect to and power the reusable transmitter unit when positioned in the mounting area.

6. The continuous analyte monitoring wearable device of claim 1 , wherein the base unit includes a connector configured to provide an electrical connection between the reusable transmitter unit and the at least one power source.

7. 10. The continuous analyte monitoring wearable device of claim 1, wherein the analyte sensor assembly includes an analyte sensor configured to detect an analyte concentration in interstitial fluid.

8. 10. The continuous analyte monitoring wearable device of claim 1, wherein the attachment area is configured to allow the reusable transmitter unit to removably couple and seal to a connector.

9. 1. A method of forming a continuous analyte monitoring wearable device, comprising: providing a base having a power supply support location, a sensor assembly support location, and a transmitter unit support location; placing at least one power source at the power source support location, the at least one power source configured to contact one or more electrical contacts mounted at the power source support location; placing a sensor assembly including an analyte sensor at the sensor assembly support location; providing an encapsulation layer including an opening over the at least one power source, at least a portion of the sensor assembly, and at least a portion of the base to form a sealed disposable unit, the sealed disposable unit being configured to allow a transmitter unit to be attached to and detached from the transmitter unit support location on the base; providing the transmitter unit in the transmitter unit support location on the base through a base opening, the base opening being provided on a surface configured to be adjacent to a user's skin in use; and sterilizing the sealed disposable unit.

10. 10. The method of claim 9, wherein the encapsulation layer includes a mounting area, and the transmitter unit is first coupled to the transmitter unit support location and then separated therefrom.

11. 10. The method of claim 9, wherein sterilizing the sealed disposable unit comprises subjecting the sealed disposable unit to electron beam radiation.

12. 12. The method of claim 11, wherein sterilizing the sealed disposable unit comprises irradiating the sealed disposable unit with 18 kGy to 25 kGy of electron beam radiation.

13. The method of claim 9 , wherein providing the encapsulation layer comprises forming the encapsulation layer at a temperature less than 100° C.

14. 10. The method of claim 9, comprising packaging the sealed disposable unit in a plastic housing having a sealing cover or sealing in a laminated foil and plastic sheet enclosure.

15. 1. A method of forming a wearable device configured for use in continuous analyte monitoring, comprising: providing a base having a transmitter unit support location, a power supply support location, and a sensor assembly support location; placing at least one power source at the power source support location, the at least one power source configured to contact one or more electrical contacts mounted at the power source support location; placing a sensor assembly including an analyte sensor at the sensor assembly support location; providing an enclosure having an opening; placing the base within the opening of the enclosing portion such that the base and enclosing portion form a sealed disposable base unit, the sealed disposable base unit configured to allow a transmitter unit to be attached to and detached from the transmitter unit support location on the base; providing the transmitter unit in the transmitter unit support location on the base through a base opening, the base opening being provided on a surface configured to be adjacent to a user's skin in use; and sterilizing the sealed disposable unit.

16. 16. The method of claim 15, wherein the analyte sensor is configured to sense an analyte concentration in interstitial fluid.

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