Method and apparatus configured for transmitting data in a continuous analyte monitor - Patent Application 20070122997

Abstract

In one or more embodiments, a base unit of a wearable device for continuous analyte monitoring may include a sensor memory circuit and a sensor assembly. The sensor memory circuit stores information (data) of at least one parameter of at least one component of the base unit, such as the sensor assembly. The base unit is coupled to a transmitter unit of the wearable device and configured to communicate the information to the transmitter unit. An analyte determination is made at least in part based on the information. Numerous other embodiments are provided.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This claims priority to U.S. Provisional Patent Application No. 63 / 033,825, filed June 2, 2020, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0002] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to continuous analyte monitoring methods and devices. [Background technology]

[0003] Continuous analyte monitoring in in vivo samples, such as continuous glucose monitoring (CGM), has become a routine detection operation, particularly in diabetes care. By providing real-time glucose concentrations, therapeutic interventions may be applied in a more timely manner and glycemic conditions may be better controlled.

[0004] During CGM operation, the biosensor in the CGM device is typically inserted subcutaneously and operates continuously in an environment surrounded by tissue and interstitial fluid. The subcutaneously inserted biosensor provides a signal to the CGM device's wireless CGM transmitter, 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 predetermined intervals).

[0005] The wireless CGM transmitter can be attached to the external surface of the user's skin, such as the abdomen or back of the upper arm, while the biosensor is inserted through the skin to contact the interstitial fluid. The biosensor interacts with the interstitial fluid and generates electrical signals proportional to the amount of glucose present. These electrical signals are communicated to the CGM transmitter for use in determining glucose levels.

[0006] Manufacturing a CGM assembly of a CGM transmitter and biosensor that is comfortable for the patient and cost-effective remains a challenge. Improved CGM devices and methods are desirable. Summary of the Invention

[0007] In some embodiments, a base unit of a wearable device for use during continuous analyte monitoring is provided, the base unit comprising: a sensor assembly including at least one biosensor configured to be placed subcutaneously; and a sensor memory circuit configured to store information (data) relating to at least one parameter of at least one component of the base unit, the base unit configured to be coupled to a transmitter unit of the wearable device, the information being communicable to the transmitter unit.

[0008] In some embodiments, a transmitter unit of a wearable device for use during continuous analyte monitoring is provided, the transmitter unit including electronic components configured to receive information (data) stored in a sensor memory circuit of a base unit of the wearable device in response to the transmitter unit and the base unit being coupled, the information including at least one parameter of at least one component of the base unit.

[0009] In some embodiments, a wearable device for use during continuous analyte monitoring is provided, the wearable device comprising: a base unit, a sensor assembly located within the base unit and configured to measure an analyte in interstitial fluid, a sensor memory circuit located within the base unit and configured to store information (data) of one or more parameters of one or more components within the base unit, and a transmitter unit configured to physically couple to the base unit, such that information can be transmitted from the sensor memory circuit when the base unit and the transmitter unit are coupled.

[0010] In some embodiments, a method of manufacturing a base unit for a stationary analyte monitor is provided, the method including assembling a sensor assembly to a base plate, assembling a sensor memory circuit to the base plate, determining one or more parameters of one or more components of the base unit, and storing information (data) of the one or more parameters in the sensor memory circuit.

[0011] In some embodiments, a method for monitoring an analyte is provided that includes inserting a biosensor extending from a base unit of a wearable device into subcutaneous interstitial fluid, coupling the base unit and a transmitter unit of the wearable device, transmitting information (data) stored in a sensor memory circuit of the base unit to the transmitter unit, the information including at least one parameter of at least one component of the base unit, measuring a current passing through the biosensor, and determining an analyte concentration based at least in part on the current and the information.

[0012] Other features, aspects, and advantages of embodiments according to the present disclosure will become more fully apparent from the summary of the invention, the claims, and the accompanying drawings illustrating many exemplary embodiments, by describing many exemplary embodiments and implementations. Various embodiments according to the present disclosure are also capable of other and different applications, and their several details may be modified in various respects without departing from the scope of the claims and their equivalents. Accordingly, the drawings and descriptions should be regarded as illustrative in nature, and not as restrictive. [Brief explanation of the drawings]

[0013] [Figure 1A] The drawings described below are for illustrative purposes and are not necessarily drawn to scale. The drawings are not intended to limit the scope of the invention in any way. Accordingly, the drawings should be regarded as illustrative in nature and not as limiting.

[0014] FIG. 1A shows a side view of a wearable device including a transmitter unit and a base unit configured for use during continuous analyte monitoring according to embodiments provided herein.

[0015] [Figure 1B] FIG. 1B illustrates a top view of the wearable device of FIG. 1A according to one or more embodiments provided herein.

[0016] [Figure 1C] FIG. 1C shows a cross-sectional side view of the wearable device of FIG. 1A including a base unit and a transmitter unit, according to one or more embodiments provided herein.

[0017] [Figure 1D] FIG. 1D shows a cross-sectional side exploded view of the wearable device of FIG. 1C with the transmitter unit separated from the base unit, according to one or more embodiments provided herein.

[0018] [Figure 2A] FIG. 2A shows an exploded perspective view of a base unit of a wearable device according to one or more embodiments provided herein.

[0019] [Figure 2B] FIG. 2B shows an exploded perspective view of the sensor memory circuit, conductors, and printed circuit board of the wearable device of FIG. 2A according to embodiments provided herein.

[0020] [Figure 3] FIG. 3 shows a schematic diagram illustrating the electrical circuitry of the wearable device of FIG. 1C and the connections therebetween, according to one or more embodiments provided herein.

[0021] [Figure 4A]FIG. 4A shows a schematic diagram illustrating an analyte monitoring system including a wearable device and an external device, according to one or more embodiments provided herein.

[0022] [Figure 4B] FIG. 4B shows a schematic diagram illustrating another analyte monitoring system including a wearable device and an external device according to one or more embodiments provided herein.

[0023] [Figure 5] FIG. 5 shows a flowchart of a method for manufacturing a base unit of a wearable device of a continuous analyte monitoring system according to one or more embodiments provided herein.

[0024] [Figure 6] FIG. 6 shows a flowchart of a method for continuous analyte monitoring using a wearable device including a base unit and a transmitter unit, according to one or more embodiments provided herein.

[0025] [Figure 7] FIG. 7 shows a flowchart of a method for manufacturing a base unit of a stationary analyte monitor according to one or more embodiments provided herein.

[0026] [Figure 8] FIG. 8 shows a flowchart of a method for subcutaneously monitoring an analyte according to one or more embodiments provided herein. DETAILED DESCRIPTION OF THE INVENTION

[0027] To more closely monitor a person's analyte levels (e.g., glucose concentrations) and detect changes in analyte levels, methods and devices for continuous analyte monitoring (e.g., continuous glucose monitoring (CGM)) have been developed. While CGM systems "continuously" generate a glucose signal, such as a continuous electrochemical signal, the measurement of the generated analyte (e.g., glucose) is typically not truly continuous but rather performed every few minutes. While the following description pertains to continuous glucose monitoring, the devices and methods described below may be readily adapted to monitor other analytes in other continuous analyte monitoring systems, such as, for example, lactate.

[0028] CGM systems typically have a wearable portion (wearable device) that is worn on the body and can communicate (e.g., wirelessly) with an external device, such as a handheld receiver, or another portable device, such as a smartphone with an appropriate application software program (app). The wearable device may be worn for several days or weeks (e.g., 1-2 weeks) before being removed and replaced. The wearable device includes a biosensor that is inserted subcutaneously (implanted). The wearable device may also include analog circuitry coupled to the biosensor and configured to energize the biosensor and measure a current signal generated by the implanted biosensor. The wearable device may also include processing circuitry for determining an analyte (e.g., glucose) level based on the measured current signal, as well as electronic transmitter circuitry for communicating the analyte (e.g., glucose) level to an external receiving device. The wearable device may be attached (e.g., glued) to the external surface of the skin, such as the abdomen, the back of the upper arm, or another suitable location. CGM systems measure analyte concentrations (e.g., glucose levels) in interstitial fluid or indirect capillary blood samples.

[0029] A CGM system may provide frequent measurements of a user's analyte (e.g., glucose) levels without each such measurement having to involve the drawing of a blood sample, such as a fingertip draw. A CGM system may still employ occasional fingertip draws and the use of a blood glucose measurement (BGM) system, such as the Contour NEXT One® by Ascensia Diabetes Care AG of Basel, Switzerland, for calibration of the CGM system.

[0030] As discussed above, the wearable device of a CGM system is typically worn for up to two weeks, after which it is removed and replaced with a new wearable device. Having to replace the wearable device of a CGM system every few weeks significantly increases the cost associated with implementing such continuous analyte monitoring. For example, according to embodiments of the present disclosure, the biosensor may need to be replaced, while other components can be reused.

[0031] The embodiments provided herein provide a wearable device for use during continuous analyte (e.g., glucose) monitoring. The wearable device described herein includes a base unit (e.g., a disposable portion) and a transmitter unit (e.g., a reusable portion). The base unit may include a sensor assembly including a biosensor configured to monitor a specific analyte and a sensor memory circuit that electronically stores information (data) associated with and / or specific to the individual base unit, such as the biosensor assembly. For example, the sensor memory circuit may store at least one parameter of at least one component of the base unit. The sensor memory circuit may include, for example, PROM, EEPROM, SRAM, SDRAM, and NOR and NAND flash memory. Other types of sensor memory circuits may also be used.

[0032] In particular, the sensor memory circuit may include radiation-hardened (radiation-hard) memory, i.e., the sensor memory circuit, and in particular the radiation-hard memory, retains information (data) and remains functional even after exposure to a dose of radiation high enough to sterilize the base unit, such as ionizing radiation (such as gamma (γ) radiation) and / or electron beam (E-beam) radiation. In some embodiments, the sensor memory circuit may be disposed within a radiation-hard package. In some embodiments, the radiation-hard package or radiation-hard memory reduces the total ionizing dose (TID) received by the sensor memory circuit relative to a TID environment outside the sensor memory circuit. In some embodiments, the reduction in TID received by the sensor memory circuit may be several orders of magnitude. The radiation-hard sensor memory circuit and / or radiation-hard package allows the sensor memory circuit and / or base unit to be sterilized by exposure to radiation without erasing or damaging the sensor memory of the sensor memory circuit. Thus, the completed base unit may be placed in a container for shipping to a user. The base unit is then sterilized using radiation without erasing or damaging the sensor memory circuit.

[0033] The transmitter unit may include electronic circuitry used, for example, to provide a bias to the sensor assembly, to measure a current signal through the sensor assembly (or its associated biosensor), to calculate an analyte concentration value (e.g., a glucose concentration value) based on the measured current signal, and to transmit the analyte concentration value and / or related information to an external device, such as an external receiving device or an external transceiver device. In some embodiments, raw measurements and / or data generated by the biosensor may be transmitted, and the analyte concentration value may then be calculated by the external device.

[0034] Exemplary circuitry within the transmitter unit may include an analog front end configured to bias the sensor assembly and sense the current passing through the sensor assembly at appropriate time increments. The circuitry may include operational amplifiers, current sources, current detection circuitry, comparators, etc. Other circuits and components within the transmitter unit may 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 microprocessor, a microcontroller or the like configured to calculate an analyte concentration level based on the measured current signal, and transmitter circuitry for transmitting the analyte concentration level to an external device.

[0035] The transmitter unit may also include circuitry and / or components that cause the sensor memory circuit in the base unit to transmit information (e.g., data) stored therein and circuitry and / or components that receive information. The information may be data stored and transmitted via data storage and transmission technology. For example, the transmitter unit and base unit may be electrically coupled when physically coupled. The electrical coupling may cause the transmitter unit to transmit information stored in the sensor memory circuit. The information may be used by the circuitry of the transmitter unit and / or an external receiving device to calculate analyte concentration and for other functions, such as data display (e.g., displaying analyte concentration values ​​and / or trends).

[0036] The electronic circuitry is typically the most expensive part of a wearable device and, as designed, can last significantly longer than the period the wearable device is employed. The base unit contains components, such as biosensors, that penetrate the skin and need to be replaced frequently. For example, wearable devices are typically discarded after about two weeks, while the circuitry within the transmitter unit can possibly last indefinitely. In some embodiments, a reusable transmitter unit may be reused with two or more, three or more, four or more, five or more, ten or more, twenty or more, thirty or more, forty or more, fifty or more, or even one hundred or more base unit replacements.

[0037] In some embodiments, a wearable device for use during continuous analyte monitoring may include a base unit (e.g., a disposable base unit) including at least a sensor assembly and a sensor memory circuit. The wearable device may also include a reusable transmitter unit configured to mate with the base unit and receive information stored in the sensor memory circuit of the base unit. In some embodiments, the base unit may be configured to be disposed of after a single analyte monitoring period (e.g., 10-14 days), and the transmitter unit may be configured to be detached from the base unit after the single analyte monitoring period and reused (e.g., reattached) with another new base unit. These and other embodiments, as well as methods for making and / or using such wearable devices, are described below with reference to FIGS. 1A-8.

[0038] 1A-1D, referenced herein, show various views of a wearable device 100 (e.g., a continuous analyte monitor) for use during continuous analyte monitoring (e.g., continuous glucose monitoring) according to one or more embodiments provided herein. The wearable device 100 is illustrated as being at least partially dome-shaped and at least a portion thereof. The wearable device 100 is not limited to the dome shape illustrated herein and may have other shapes. The base unit 102 and transmitter unit 104 may have any suitable shape (e.g., circular, oval, square, rectangular, etc.) in top view. For example, the wearable device 100 may have a primarily rectangular shape and may be sized and shaped to resemble a medical bandage. In such an embodiment, the base unit 102 may be rectangular in plan view.

[0039] The base unit 102 may be a disposable unit, the transmitter unit 104 may be a reusable unit, and the transmitter unit 104 and the base unit 102 are configured to be coupled together. In some embodiments, the base unit 102 and the transmitter unit 104 are also configured to be detachable from one another. For example, the transmitter unit 104 and the base unit 102 may be physically coupled to form the wearable device 100, as shown in FIGS. 1A and 1B . Any suitable mechanical mechanism configured to enable coupling of the transmitter unit 104 to the base unit 102 may be used. When physically coupled, the transmitter unit 104 and the base unit 102 may also be electrically coupled such that data signals and / or electrical current may be communicated and passed between the electrical components of the transmitter unit 104 and the base unit 102. This communication may, in some embodiments, be responsive to the transmitter unit 104 and the base unit 102 being physically coupled. In other embodiments, communication may be initiated by a command, such as a start command.

[0040] As mentioned above, both the transmitter unit 104 and the base unit 102 may be sealed units (e.g., waterproof), with only the electrical contacts of the transmitter unit 104 and base unit 102 remaining exposed, as described below. Once the transmitter unit 104 and base unit 102 are physically coupled, the electrical contacts may also be sealed from the external environment, such as by use of a sealing member.

[0041] The biosensor 108 (e.g., the portion inserted through the user's skin 118) may extend from the base unit 102 and may be configured to be positioned at least partially in the interstitial fluid of the subcutaneous region, as described herein. The biosensor 108 may be or include an analyte sensor or portion of an analyte sensor, such as at or near the tip 108T. The biosensor 108 may be inserted with an insertion device (not shown) having a sharp tip that penetrates the skin to introduce the biosensor 108 into the subcutaneous region of the user. Any suitable insertion device may be used. A sensor circuit coupled to the biosensor 108 may include a device that applies at least one bias voltage to the analyte sensor portion of the biosensor 108 within the interstitial fluid, and another device that measures the resulting current flow proportional to the analyte being monitored.

[0042] In some embodiments, the base unit 102 is configured to be disposed of after a single analyte monitoring period (e.g., 7 days, 10 days, 14 days, or some other suitable period). In some embodiments, the transmitter unit 104 is configured to be removed (detached) from the base unit 102 after a single analyte monitoring period and reused with another new base unit.

[0043] As shown in FIGS. 1C and 1D, the base unit 102 may include a base plate 110 having a sensor assembly support location 112 and a memory circuit location 114. The base plate 110 may have a first surface 110A and an opposing second surface 110B. The first surface 110A may be configured to be adjacent to or located adjacent to a corresponding surface 116A of the transmitter unit 104. The second surface 110B may be configured to be adjacent to and / or interconnected with a user's skin surface 118S (FIG. 1A). The first surface 110A may include a recess 110C, such as a groove, configured to receive a gasket 120, such as an O-ring. For example, the recess 110C may be a peripheral groove or the like that receives the gasket 120 to seal the periphery between the transmitter unit 104 and the base unit 102. In some embodiments, the base plate 110 may be formed from a 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), and low density polyethylene (LDPE). Other suitable materials may also be used for the base plate 110.

[0044] An adhesive layer 122, such as double-sided tape or a pressure-sensitive adhesive, may be attached (e.g., glued) to the second surface 110B of the base plate 110 and may adhere the base unit 102 to the user's skin surface 118S. The adhesive layer 122 may include a first side 122A and a second side 122B opposite the first side 122A. The first side 122A may be adhered to the second surface 110B of the base plate 110. The second side 122B of the adhesive layer 122 may be configured to adhere to the user's skin surface 118S so as to adhere the base unit 102 to the skin surface 118S.

[0045] 2A , an exploded isometric view of an embodiment of the base unit 102 is shown. The sensor assembly support position 112 may provide a support position for a sensor assembly 126 used to measure or sense an analyte in subcutaneous tissue, such as a user's interstitial fluid. For example, the sensor assembly 126 may be configured to measure an analyte (e.g., glucose) in subcutaneous tissue. The sensor assembly support position 112 may be any suitable shape (e.g., rectangular, square, circular, etc.) that supports and / or retains the sensor assembly 126 on or within the base unit 102. The sensor assembly 126 may be electrically and physically coupled to the biosensor 108. In some embodiments, the sensor assembly 126 may be integrally formed with the biosensor 108. The sensor assembly 126 may facilitate transmission of electrical signals to and from the tip 108T of the biosensor 108 and / or other portions of the biosensor 108.

[0046] The biosensor 108 may include an active area containing one or more catalytic agents and / or reagents configured to sense the presence and concentration level of a particular analyte, such as glucose. The base plate 110 may include a hole 130 through which the biosensor 108 may pass. A gasket 132 (e.g., an O-ring—see also FIGS. 1C and 1D ) may be at least partially located within the hole 130 and may prevent contaminants from passing through the hole 130 after insertion of the biosensor 108. For example, the gasket 132 may form a seal between the biosensor 108 and the hole 130 to prevent contaminants (e.g., blood) from entering the base unit 102. The gasket 132 may also prevent other contaminants from contacting the user's skin surface 118S.

[0047] The sensor assembly 126 may include a number of conductive contact pads 134 that electrically couple the sensor assembly 126 to other components, and ultimately to the transmitter unit 104. In the embodiment described herein, the sensor assembly 126 includes four contact pads 134. In other embodiments, the sensor assembly 126 may include more or fewer contact pads 134.

[0048] The connector 136 may be electrically coupled to (e.g., in contact with) the contact pads 134 and may electrically couple the contact pads 134 to the sensor pads 140A of the transmitter unit 104. In some embodiments, the connector 136 may be an elastomeric connector, which may be referred to as a zebra strip. In some embodiments, the connector 136 may be a dot connector or a dot elastomeric connector. In some embodiments, the connector 136 conducts only in the z-direction, for example, along the z-axis ( FIG. 1D ). Thus, the connector 136 may be a single device that may be positioned over all of the contact pads 134 or that passes current only to locations directly above the contact pads 134. In such an embodiment, the connector 136 may electrically couple the contact pads 134 to the sensor pads 140A of the transmitter unit 104 when the transmitter unit 104 and the base unit 102 are physically coupled.

[0049] The base unit 102 includes a sensor memory circuit 142, which may be packaged as a memory device. In some embodiments, the memory circuit and / or memory device may be a single memory component. The sensor memory circuit 142 may be secured within the memory circuit location 114 by an adhesive 145, such as double-sided tape or epoxy adhesive. Other securing configurations may be used to secure the sensor memory circuit 142 within the memory circuit location 114 or elsewhere within the base unit 102. The sensor memory circuit 142 may include radiation-hardened memory (radiation-hard memory) or may be located within a radiation-hard package. Radiation-hard memory includes packaging and / or circuitry that retains information (e.g., data) stored therein when the packaging and / or circuitry is exposed to radiation used to sterilize the base unit 102. The sensor memory circuit 142 may include programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), and / or NOR and NAND flash memory. Other types of sensor memory circuits may also be used for the sensor memory circuit 142 .

[0050] During manufacturing of the base unit 102 and / or the wearable device 100, the base unit 102 and / or the wearable device 100 may be sterilized using radiation, such as ionizing radiation, gamma (γ) radiation, and / or electron beam (E-beam) radiation. In some embodiments, the base unit 102 is manufactured separately from the transmitter unit 104, and only the base unit 102 is sterilized using radiation. In some embodiments, the transmitter unit 104 may not be sterilized using radiation. For example, the base unit 102 may be exposed to radiation to sterilize all components therein.

[0051] Conventional memory devices and other electronic components may be damaged by the radiation used during sterilization. For example, components within conventional memory devices may be damaged or conventional memory may be erased by the radiation. The sensor memory circuit 142 may be packaged in radiation-hard and / or radiation-resistant packaging. A radiation-hard sensor memory circuit 142 or a sensor memory circuit packaged in a radiation-hard package provides that the sensor memory circuit 142 can be exposed to a total ionizing dose (TID) of the radiation used for sterilization without erasing the information (data) stored therein.

[0052] In some embodiments, radiation-hardened (radiation-tolerant) packaging or radiation-hard memory reduces the total ionizing dose (TID) received by the sensor memory circuit 142 within the package compared to the total ionizing dose environment outside the package. In some embodiments, the reduction in TID is several orders of magnitude. The radiation-hard sensor memory circuit 142 allows the sensor memory circuit 142 and base unit 102 to be sterilized using radiation without erasing and / or damaging the sensor memory circuit 142. For example, the base unit 102 may be assembled with the sensor memory circuit 142 secured therein. The base unit 102 with the sensor memory circuit 142 secured therein may then be sterilized using radiation.

[0053] In some embodiments, the sensor memory circuit 142 may have a single-wire interface that utilizes a voltage-based digital system that operates with only two contacts, data and ground, for half-duplex, bidirectional communication. Referring to FIG. 2B , an exploded view of an embodiment of the sensor memory circuit 142 and a portion of the alternative connector 136A is shown. The embodiment of the sensor memory circuit 142 has two contacts (e.g., two external nodes): a data contact pad 144A (e.g., a data node) and a ground contact pad 144B (e.g., a ground node). In some embodiments, these two contacts are the only contact pads or external nodes for the sensor memory circuit 142. The single-wire sensor memory circuit 142 may be implemented for use in a momentary contact environment. For example, either disconnecting the voltage from the sensor memory circuit 142 or a loss of voltage to the power supply causes the sensor memory circuit 142 to enter a defined reset state. When voltage is returned to the sensor memory circuit 142, the sensor memory circuit 142 may wake up and signal its presence. As described below, the sensor memory circuit 142 may then transmit the information stored therein, such as to the transmitter unit 104. Other types of memory circuits may be used in the sensor memory circuit 142. For example, the sensor memory circuit 142 may include an inter-integrated circuit communication (I2C) or serial peripheral interface (SPI) architecture.

[0054] Connector 136A may be used in place of connector 136. Connector 136A may be an elastomeric connector, such as a z-connector, having alternating layers of conductors and insulators. Thus, connector 136A conducts in the z-direction as described above.

[0055] Each sensor memory circuit may store sensor information specific to an individual base unit and / or components therein. For example, each sensor memory circuit may store at least one parameter of at least one component of the base unit in which it is located. Thus, sensor memory circuit 142 may store information specific to base unit 102 and / or at least one component thereof. The sensor information may include one or more parameters, including: a. Electrode sensitivity gradient b.Manufacturing date c. Batch or lot number d.Security code e.EEPROM version f.Serial number

[0056] The sensitivity information may include sensitivity gradients of the electrodes of the biosensor 108 and / or the sensor assembly 126. In embodiments in which the base unit 102 includes multiple biosensors, the sensitivity information may include data such as the sensitivity gradient of each of the biosensors.

[0057] The sensitivity information may include one or more mathematical functions or coefficients, which may be obtained, for example, by testing the sensor assembly 126. Each biosensor and / or sensor assembly may be unique with respect to at least its respective sensitivity, and thus the information may include specific parameters associated with the biosensors 108 and / or sensor assemblies 126 located within the same base unit 102. The transmitter unit 104 or other components processing the data generated by the sensor assembly 126 may use the sensitivity information or parameters associated with the other components to accurately calculate and determine the analyte level.

[0058] In some embodiments, one or more parameters (e.g., sensor information) may include the manufacturing date of one or more components within the base unit 102. For example, the sensor information may include the manufacturing date of the sensor assembly 126, the biosensor 108, and / or the sensor memory circuit 142. The sensor information may be used to determine whether components within the base unit 102 are out of date. For example, some components within the base unit 102 may have a limited shelf life. If an attempt is made to use the base unit 102 and it has one or more components with an expired shelf life, an indication may be provided to the user. In some embodiments, if the base unit 102 includes multiple biosensors, the sensor information may include the manufacturing date of the biosensor 108 or multiple biosensors. A device that analyzes the analyte level determined by the biosensor 108 may provide an indication of whether the age of the biosensor 108 is greater than a predetermined age.

[0059] In some embodiments, the sensor information may include at least one unique identifier of one or more components of the base unit 102, which may distinguish (e.g., identify) the base unit 102 and / or its components from other base units. The at least one unique identifier may be, for example, a serial number and / or a lot number. In some embodiments, the unique identifier may include the serial number and / or lot number of the base unit 102, the sensor assembly 126, the sensor memory circuit 142, and / or one or more other components of the base unit 102. A device that analyzes analyte levels may use the one or more unique identifiers, for example, to determine whether any components have been recalled or identified as possibly defective. The device may also base its calculations or determinations of analytes on the base unit 102 and / or the actual components of the base unit 102 as determined by their unique identifiers.

[0060] In some embodiments, the sensor information may include one or more model numbers or other identifications of components within the base unit 102, or an identification of the base unit 102. In some embodiments, the sensor information may include the model of the sensor memory circuit 142, the sensor assembly 126, the base unit 102, and / or other components of the base unit 102. The model number and / or general identification may be used in processing data generated by the base unit 102. For example, a particular model of biosensor 108 may have different parameters than another model of the biosensor.

[0061] In some embodiments, the sensor information may include one or more security codes used to access components of the base unit 102 or the transmitter unit 104. For example, another component that processes data generated by the transmitter unit 104 or the base unit 102 may require a security code stored in the sensor memory circuit 142 to enable communication therewith. Use of a security code may prevent illegal or unauthorized base units from communicating with the transmitter unit 104 or other devices. Thus, the security code may prevent the wearable device 100 from reporting potentially erroneous analyte levels due to the use of an improper base unit or may improve security.

[0062] During manufacture and / or assembly of base unit 102, sensor assembly 126 may be placed in sensor assembly support location 112 and sensor memory circuit 142 may be placed in memory circuit location 114. The above-described sensor information may be programmed into sensor memory circuit 142 before or after sensor memory circuit 142 is placed in base unit 102, as further described below.

[0063] In some embodiments, the connector 136 may include one or more electrodes 214 that may be electrically coupled to at least some components within the base unit 102 and the transmitter unit 104 (FIGS. 1A-1D). The electrodes 214 are axially movable (in the Z direction) within the body of the connector 136 and may be biased against the connector 136 to make electrical contact with components (e.g., contact pads) within the base unit 102 and / or the transmitter unit 104. In some embodiments, the number of electrodes 214 may equal the number of contact pads on the components within the base unit 102 and / or the transmitter unit 104. In the example of FIGS. 2A and 2B, the sensor assembly 126 may include four contact pads 134, and the sensor memory circuit 142 may include two contact pads 144, a data contact pad 144A, and a ground contact pad 144B (e.g., a node), such that the connector 136 includes six electrodes 214 formed therein.

[0064] One or more electrodes 214 may be arranged in a plane, which may group the electrodes according to the electrical components that the electrodes 214 contact and are configured to energize together. For example, four sensor electrodes 214A may be configured to electrically contact a plate-shaped sensor pad 140A on the transmitter unit 104, and the four sensor electrodes 214A may also contact four contact pads 134 of the sensor assembly 126. Similarly, two memory electrodes 214B of the connector 136 may be configured to contact two contact pads 144 of the sensor memory circuit 142 and memory pad 140B of the transmitter unit 104.

[0065] Thus, when the transmitter unit 104 and the base unit 102 are physically coupled, the contact pad 140 includes a sensor pad 140A that is electrically coupled to the sensor assembly 126 via the sensor electrode 214A by energizing the sensor electrode 214A (downward as shown in FIG. 1D ) and contacting the contact pad 134. Similarly, when the transmitter unit 104 and the base unit 102 are physically coupled, the contact pad 140 includes a memory pad 140B that is electrically coupled to the sensor memory circuit 142 via the memory electrode 214B by energizing the sensor electrode 214A (downward as shown in FIG. 1D ) and contacting the contact pad 144. The sensor pad 140A may be electrically coupled to one or more components within the transmitter unit 104 that receive and / or process data from the sensor assembly 126 and / or transmit signals, including bias voltages and currents, to the sensor assembly 126. The memory pad 140B may be electrically coupled to one or more components within the transmitter unit 104 that transmit signals to and / or receive signals from the sensor memory circuit 142.

[0066] 2A may include a sensor plate 216A and a memory plate 216B. The sensor plate 216A may include the sensor electrode 214A, and the memory plate 216B may include the memory electrode 214B. The connector 136 may include other plates and / or other electrodes.

[0067] The wearable device 100 (FIGS. 1A-1D) may include a power source (not shown in FIGS. 1A-2B), such as a battery (312—FIGS. 3 and 4A-4B), configured to provide power to the components of the wearable device 100. In some embodiments, the power source may be a battery, a storage capacitor, a solar cell, a generator, or the like. In some embodiments, the power source may provide power to the sensor memory circuit 142 when the transmitter unit 104 and the base unit 102 are physically coupled. In some embodiments, the power source may be located within the base unit 102, and in other embodiments, the power source may be located within the transmitter unit 104. In some embodiments, at least one of the sensor assembly 126 and the sensor memory circuit 142 is configured to receive power in response to coupling of the transmitter unit 104 to the base unit 102. In embodiments in which the power source has a long life, the power source may be located within the transmitter unit 104. In embodiments where the power supply has a short lifespan, the power supply may be located within the base unit 102 since the base unit 102 also has a short lifespan, after which both may be replaced at the same time. In some embodiments, the transmitter unit 104 and the base unit 102 may each have a power supply.

[0068] The transmitter unit 104 may include one or more electronic components that communicate with one or more electronic components within the base unit 102 and one or more external devices. Referring again to FIGS. 1A-1D , the transmitter unit 104 may include an encapsulation layer 116 (e.g., a top cover) that may be configured to be positioned relative to or over the base unit 102. The encapsulation layer 116 may include an opening 150 that may be configured to receive at least a portion of the base unit 102. The encapsulation layer 116 may encapsulate the electronic and other components within the transmitter unit 104 to prevent the components from being exposed to contaminants. In some embodiments, the encapsulation layer 116 may be a pre-formed base into which the substrate 152 is positioned prior to formation of the encapsulation layer 116 (e.g., by a molding process).

[0069] As described below, substrate 152 may support components such as electrical components and contact pads 140 located in or on transmitter unit 104. In some embodiments, substrate 152 may be a printed circuit board, such as a flexible printed circuit board, and may be used to support electronic components such as the analog front-end circuitry and transmitter module described herein. Substrate 152 may be made from materials such as copper, Kapton, polyester (PET), polyethylene naphthalate (PEN), polyimide, fiberglass, acrylic adhesive, etc. Substrate 152 may also be made from other materials.

[0070] In some embodiments, the encapsulating layer 116 may be formed from a single layer or multiple layers. For example, the encapsulating layer 116 may be formed from one or more layers of liquid silicone rubber (LSR), thermoplastic elastomer (TPE), or the like. Other materials may be used, such as, but not limited to, ABS, polycarbonate, nylon, acetal, PPA, polysulfone, polyethersulfone, PEEK, polypropylene, HDPE, LDPE, and the like. Other materials may be used. In some embodiments, the encapsulating layer 116 may be formed at a temperature below 100°C, and in some embodiments, below 80°C.

[0071] 1A-1D, substrate 152 may be located within or at least partially accessible through opening 150. Memory pad 140B and sensor pad 140A may be attached to bottom surface 152A of substrate 152 and may be accessible through opening 150. One or more electronic components 154 may be physically and / or electrically coupled to top surface 152B of substrate 152.

[0072] The transmitter unit 104 and the base unit 102 may be configured to be coupled to complete the wearable device 100. For example, the transmitter unit 104 may be configured to be attached to, detached from, inserted into, and / or removed from the base unit 102. Various retention mechanisms may be included on the base unit 102 and the transmitter unit 104 for such coupling. The retention mechanism may allow the transmitter unit 104 to be removably attached to the base unit 102, i.e., it may be removable. With reference to FIG. 2A , the base unit 102 may include a first retention mechanism 220A and a second retention mechanism 220B that mechanically couple to and / or contact corresponding retention mechanisms on the transmitter unit 104. The first retention mechanism 220A and the second retention mechanism 220B allow the transmitter unit 104 and the base unit 102 to be removably coupled together. Other numbers, types, and locations of retention mechanisms may be used. For example, the first and second retention features 220A and 220B may include protrusions that engage with openings, slots, or other features in the transmitter unit 104. Optionally, magnets, Velcro, adhesive surfaces, and the like may be used to enable removal and / or attachment.

[0073] Referring now to FIG. 3 , a schematic diagram of an embodiment of the wearable device 100 is shown. As shown in FIG. 3 , electrical signals can be transmitted between the base unit 102 and the transmitter unit 104 via the connector 136 (or 136A) when the base unit 102 and the transmitter unit 104 are physically coupled. For example, contact pads 144 (e.g., data contact pad 144A and ground contact pad 144B) on the sensor memory circuit 142 are electrically coupled to memory pad 140B of the transmitter unit 104 by the connector 136. Similarly, contact pad 134 on the sensor assembly 126 is electrically coupled to sensor pad 140A in the transmitter unit 104. Thus, power and electronic signals can be transmitted between the transmitter unit 104 and the base unit 102 when the transmitter unit 104 and the base unit 102 are physically coupled.

[0074] In some embodiments, the transmitter unit 104 may include an analog front end 308, which may be configured to drive the sensor assembly 126 and / or process sensor data generated by the sensor assembly 126, including the biosensor 108. The analog front end 308 may be configured to apply a bias voltage to the sensor assembly 126 and measure the resulting current flow through the sensor assembly 126. For example, the analog front end 308 in conjunction with the sensor assembly 126 may apply a bias voltage to the biosensor 108 located in interstitial fluid and measure the resulting current. As described above, the resulting current is proportional to the analyte concentration. The analog front end 308 may perform other, fewer, and / or more functions.

[0075] The transmitter unit 104 may include a microcontroller 310 coupled to the analog front end 308 and / or other circuitry. The microcontroller 310 may include processing circuitry for processing sensor data generated by the sensor assembly 126 and / or the analog front end 308. For example, in some embodiments, the microcontroller 310 may convert analog current signals generated by the sensor assembly 126 to digital current signals, store the current signals, and / or calculate analyte concentration levels based at least in part on the current signals. The microcontroller 310 may also communicate with the sensor memory circuit 142 via an input / output (I / O) port. For example, sensor information may be received via the I / O port.

[0076] In some embodiments, microcontroller 310 may include a processor such as a microcontroller, a microprocessor, processor memory, an analog-to-digital converter, etc. The processor memory may include computer program code stored thereon that, when executed by the processor, causes transmitter unit 104 and wearable device 100 to perform certain functions and / or communicate with one or more external devices, such as an external CGM device or a smartphone capable of containing and executing software programs (e.g., applications or apps), to calculate and / or display analyte data.

[0077] In some embodiments, the microcontroller 310 may transmit the current signal, the analyte concentration information, and / or other information to an external receiving device. In some embodiments, the microcontroller 310 may receive instructions, data, and / or other information from an external device.

[0078] The microcontroller 310 or other circuitry within the transmitter unit 104 may include circuitry configured to electrically couple to the sensor memory circuit 142. In the embodiment of FIG. 3, the microcontroller 310 may include an input / output (I / O) port that electrically couples to the data contact pads 144A of the sensor memory circuit 142 when the base unit 102 and transmitter unit 104 are coupled. The microcontroller 310 may receive data stored in the sensor memory circuit 142 via the I / O port, such as the above-described sensor information associated with one or more parameters of one or more components of the base unit 102. In some embodiments, a signal (e.g., a pull signal) may be sent from the I / O port of the microcontroller 310 to the sensor memory circuit 142, causing the sensor memory circuit 142 to transmit data without user input. Thus, the sensor memory circuit 142 may automatically transmit data to the microcontroller 310 in response to the transmitter unit 104 and its coupled base unit 102. Optionally, transmission of sensor information to the I / O port may be prompted by an external device or the like.

[0079] The microcontroller 310 may store the information transmitted from the sensor memory circuit 142 and may use the information when calculating the analyte concentration and / or performing other functions. In other embodiments, the information may remain in the sensor memory circuit 142 and be accessed as needed by the microcontroller 310 or other circuits during processing. As described above, the information stored in the sensor memory circuit 142 may include sensor information related to the sensitivity of the sensor assembly 126 and / or biosensor 108, which may be used by the microcontroller 310 when calculating the analyte concentration based on at least measurements made by the sensor assembly 126 and / or biosensor 108. In some embodiments, at least some of the information may be transmitted to an external device, which may use the information to calculate the analyte concentration. In some embodiments, the information may be provided to a user of the wearable device 100. For example, the manufacturing date and / or expiration date of the base unit 102 may be provided to the user, allowing the user to decide whether to use the base unit 102. In some embodiments, a security code matching a security code stored in the sensor memory circuit 142 may need to be entered by the user into the external device before communication can begin between the transmitter unit 104 and the base unit 102, or between the wearable device 100 and the external device.

[0080] The transmitter unit 104 may include a power source, such as a battery 312, that provides power to both the transmitter unit 104 and the base unit 102. In some embodiments, the power source may be located within the base unit 102, while in other embodiments, the base unit 102 and the transmitter unit 104 may each have their own power source. In the embodiment of FIG. 3, the battery 312 may be located within the transmitter unit 104, such that the base unit 102 does not require a power source. Thus, the cost of components and manufacturing of the base unit 102 is reduced compared to conventional devices. The battery 312 may provide power to the analog front end 308 and the microcontroller 310. When included in the transmitter unit 104, the battery may be rechargeable.

[0081] When the transmitter unit 104 and base unit 102 are coupled, the battery 312 may provide power to the sensor memory circuit 142 and the sensor assembly 126, which in some embodiments may be provided via the analog front end 308. Exemplary batteries 312 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 power sources / battery types may also be used.

[0082] 4A shows a more detailed block diagram of an example analyte monitoring system 400 according to embodiments provided herein. In the embodiment of FIG. 4A, the analog front end 308 may include a bias circuit 444 that may be configured to couple to the sensor assembly 126 via the connector 136 (shown by a dotted line, but as configured in FIGS. 1C, 1D, or 2B). The bias circuit 444 may be configured to apply a bias voltage, such as a continuous DC bias voltage, through the sensor assembly 126 and the biosensor 108 to a sensor portion in contact with the analyte-containing fluid. In this exemplary embodiment, the analyte-containing fluid may be human interstitial fluid, and the bias voltage may be applied to electrodes (not shown), for example, of the biosensor 108 (e.g., working electrode, counter electrode, etc.).

[0083] In some embodiments, the biosensor 108 may include at least two electrodes, and a bias voltage may be applied across the two electrodes. In such cases, the resulting current may be measured through the sensor assembly 126. In other embodiments, the biosensor 108 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 the resulting current may be measured, for example, through the working electrode.

[0084] In embodiments in which the wearable device 100 is a continuous glucose monitor (CGM), the biosensor 108 and / or its electrodes may include reagent chemicals that react with a glucose-containing solution in a reduction-oxidation reaction, which affects the concentration of charge carriers and the time-dependent impedance of the biosensor 108. Exemplary chemicals include glucose oxidase, glucose dehydrogenase, and the like. In some embodiments, mediators such as ferricyanide or ferrocene may be used. In some embodiments, the biosensor 108 may include a microbiosensor or a plurality of microbiosensors, such as a microbiosensor array.

[0085] The bias voltage generated and / or applied by bias circuit 444 can be, for example, in the range of about 0.1 to 1 volt relative to a reference electrode. Other bias voltages may also be used. A current passes through biosensor 108 located in the analyte-containing fluid in response to the bias voltage and the analyte concentration in the analyte-containing fluid and is measured by current measurement circuit 446 (also referred to as a current detection circuit). Current measurement circuit 446 generates a current measurement signal (I) having a magnitude indicative of the magnitude of the current passing through biosensor 108. MEAS ) in the biosensor 108. In some embodiments, the current measurement circuit 446 may be configured to sense and / or measure the current flowing through the biosensor 108. In some embodiments, the current measurement circuit 446 may use, for example, a suitable current-to-voltage converter (CVC). In some embodiments, the current measurement circuit 446 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 biosensor 108 passes. The voltage developed across the resistor of the current measurement circuit 446 represents the magnitude of the current and is used to generate a current measurement signal (I MEAS ) may be output.

[0086] In some embodiments, the sample circuit 448 may be coupled to the current measurement circuit 446 and may generate a current measurement signal I MEAS The sample circuit 448 may be configured to sample the current measurement signal I MEAS For example, the sample circuit 448 may generate digitized time-domain sample data representative of the analyte (e.g., glucose) signal. MEAS The sample circuit 448 may be any suitable analog-to-digital converter configured to receive the current measurement signal I 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 the sample circuit 448 may be 16 bits, although more or fewer bits may be used in other embodiments. In some embodiments, the sample circuit 448 samples the current measurement signal I at a sampling rate in the range of about 10 samples per second to 1,000 samples per second. MEASA faster or slower sampling rate 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. Other suitable sampling circuits may be employed.

[0087] The microcontroller 310 may include a processor 450 that may be coupled to a sample circuit 448 and may further be coupled to a memory 454. In some embodiments, the processor 450 and the sample circuit 448 are configured to communicate directly with each other via a wired path (e.g., via a serial or parallel connection). In other embodiments, the processor 450 and the sample circuit 448 may be coupled by the memory 454. In this configuration, the sample circuit 448 writes data to the memory 454 and the processor 450 reads data from the memory 454.

[0088] The memory 454 may store therein one or more gain functions 456 for use in determining an analyte level (e.g., a glucose level) based on raw signals obtained from the current measurement circuit 446 and / or the sample circuit 448. For example, in some embodiments, three or more gain functions may be stored in the memory 454 for use with different segments (periods) of analyte collected data. The memory 454 may also store therein, by way of example, a gain function for the current measurement signal I MEAS and may store a plurality of instructions that may calculate an analyte level based in part on the sensor information received from sensor memory circuit 142. In various embodiments, processor 450 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.

[0089] Memory 454 may be memory, such as, but not limited to, one or more volatile and / or nonvolatile memories. 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. Memory 454 may be packaged, for example, as a single chip or as multiple chips. In some embodiments, memory 454 may be embedded with one or more other circuits in an integrated circuit, such as, for example, an application-specific integrated circuit (ASIC). In some embodiments, memory 454 may be integral to processor 450 .

[0090] In some embodiments, the instructions stored in memory 454, when executed by processor 450, may include instructions that cause processor 450 to (a) receive sensor information stored in sensor memory circuit 142, (b) cause wearable device 100 to measure a current signal from biosensor 108 (via bias circuit 444, sensor assembly 126, current measurement circuit 446, and / or sample circuit 448), (c) store the current signal in memory 454, (d) calculate an analyte level (e.g., concentration) based on the stored current signal, gain function 456, and / or sensor information from sensor memory circuit 142, and (e) communicate the analyte level to a user. In some embodiments, the analyte level is a glucose level, i.e., a glucose concentration.

[0091] As mentioned above, memory 454 may have instructions stored therein that, when executed by processor 450, cause processor 450 to perform various operations specified by one or more of the stored instructions. Memory 454 may further have a portion reserved for one or more "scratch pad" storage areas that may be used for read or write operations by processor 450 in response to execution of one or more of the instructions.

[0092] 4A , bias circuit 444, sensor assembly 126, current measurement circuit 446, sample circuit 448, processor 450, and memory 454 may be located within transmitter unit 104 of wearable device 100. In some embodiments, transmitter unit 104 may include a local display 460 for displaying information, such as analyte and / or glucose concentration information, without the use of an external device. Local display 460 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.

[0093] 4A , analyte monitoring system 400 may further include an external device 464 (e.g., an external receiving device). Processor 466 and display 468 may be located within external device 464. Display 468 may be coupled to processor 466. Processor 466 may control the text or images shown by display 468. In some embodiments, at least a portion of the sensor information stored in sensor memory circuit 142 may be communicated to external device 464, where the sensor information may be processed by processor 466 and displayed on display 468. In some embodiments, at least a portion of the processing for determining the analyte level may be performed by processor 466 and displayed on display 468. Display 468 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.

[0094] The external device 464 and the transmitter unit 104 may be communicatively coupled. In some embodiments, the communicative coupling of the external device 464 and the transmitter unit 104 may be by wireless communication via transmitter circuitry and / or receiver circuitry, such as, for example, transmit / receive circuitry 470A in the transmitter unit 104 and transmit / receive circuitry 470B in the external device 464. 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 transmitter unit 104 and the external device 464 may alternatively be by near field communication (NFC), radio frequency (RF) communication, infrared (IR) communication, or optical communication. In some embodiments, the transmitter unit 104 and the external device 464 may be connected by one or more wires.

[0095] 4B, an example of an analyte monitoring system 400A is shown, similar to the analyte monitoring system 400 shown in FIG. 4A, but with a different division of components. In the analyte monitoring system 400A, the transmitter unit 104A includes a bias circuit 444, a current measurement circuit 446 coupled to the sensor assembly 126. The transmitter unit 104A sends and / or receives instructions to and from the bias circuit 444 and generates a current measurement signal I from the current measurement circuit 446. MEAS 4A . Processor 450A may also be configured to receive information stored in sensor memory circuit 142, as described above. Additionally, processor 450A may be configured to receive and / or transmit data via transmit / receive circuit 470A. Processor 450A of transmitter unit 104A of analyte monitoring system 400A need not perform all of the functions of processor 450 of analyte monitoring system 400 of FIG. 4A .

[0096] The analyte monitoring system 400A may include an external device 464A (e.g., an external receiving device) that may perform more analyses than the external device 464 of the analyte monitoring system 400 of FIG. 4A. The analyte monitoring system 400A may function similarly to the analyte monitoring system 400 of FIG. 4A, except that the analyte concentration level may be calculated in the external device 464A. In some embodiments, the external device 464A may include a sample circuit 448 and a gain function 456 that may be stored in a receiver memory 480. A processor 466 may be coupled to the receiver memory 480 and may receive sensor information stored in the sensor memory circuit 142 and store the information in the receiver memory 480. The wearable device 100A of the analyte monitoring system 400A may be smaller, lighter, and therefore more invasive than the wearable device of FIG. 4A because the sample circuit 448 and memory 454 are not included therein. Other component configurations may be employed. For example, in a variation of the transmitter unit 104 of FIG. 4B, an external device 464A may digitally transmit the current measurement signal I from the transmitter unit 104. MEAS The sample circuitry 448 may remain within the transmitter unit 104 so that the sample circuitry 448 may receive the

[0097] FIG. 5 is a flowchart of an example method 500 of manufacturing the base unit 102 of the wearable device 100, 100A according to embodiments provided herein. The method 500 begins at block 502 by assembling the sensor assembly 126 into the base unit 102. In some embodiments, the sensor memory circuit 142 may be assembled to the base unit 102 at this point. In block 504, the sensor assembly 126 and other components of the base unit 102 may be calibrated. In some embodiments, the calibration may include measuring or calculating one or more parameters of the sensor assembly 126 and / or one or more other components of the base unit 102. For example, the calibration may include measuring or calculating sensitivity parameters (e.g., one or more sensitivity slopes) of the biosensor 108 and / or other components of the sensor assembly 126. The sensitivity parameters may include one or more mathematical functions or one or more coefficients that may be obtained, for example, by testing the sensor assembly 126. Each biosensor and / or sensor assembly may be unique with respect to at least their sensitivity and other parameters.

[0098] In block 506, the calibration data and / or other data (sensor information) is written to the sensor memory circuit 142. For example, a computer or similar device is coupled to the contact pads 144 of the sensor memory circuit 142 to write the information to the sensor memory circuit 142. In some embodiments, the information stored in the sensor memory circuit 142 may include a manufacturing date of the biosensor 108. In embodiments including multiple biosensors 108, the sensor information may include a manufacturing date of at least one of the biosensors. In some embodiments, the sensor information stored in the sensor memory circuit 142 may include a manufacturing date of one or more components of the base unit 102. In some embodiments, the sensor information stored in the sensor memory circuit 142 may include at least one unique identifier of one or more components of the base unit 102. The at least one unique identifier may include, for example, a lot number and / or a serial number. In some embodiments, the sensor information stored on the sensor memory circuit 142 may include a security code, such that the base unit 102 and / or components located thereon are only accessible through use of the security code. In some embodiments, the sensor information stored in the sensor memory circuit 142 may include a sensor memory version of the sensor memory circuit 142 .

[0099] In some embodiments, the method 500 may optionally include block 508, in which the sensor information stored in the sensor memory circuit 142 is recorded and stored in a manufacturer's database or another database. Thus, the manufacturer of the base unit 102 may have access to information about each individual base unit 102.

[0100] In block 510, the base unit 102 is sealed and packaged. For example, the base unit 102 may be sealed to prevent contaminants from entering the base unit 102. In some embodiments, sealing may include waterproofing the base unit 102. The base unit 102 may then be packaged in a package that can be shipped to a user of the base unit 102. The base unit may be sterilized as described herein before or after being packaged. In some embodiments, the package may be sealed. Other methods of sealing the package may prevent contaminants, including biological materials, from contacting the base unit 102. In block 512, the base unit 102 may be sterilized, if it is not already sterilized. In embodiments in which the base unit 102 is in a package (e.g., a sealed package), the base unit 102 may be sterilized while the base unit 102 is in the package. Sterilization may include exposing the base unit 102 to radiation. As described above, the sensor memory circuit 142 may be radiation hard so that it is not damaged or erased when exposed to radiation. In some embodiments, the packaging around the sensor memory circuit 142 may provide radiation hardening capabilities.

[0101] In some embodiments, gamma or electron beam sterilization or another sterilization method may be used to sterilize one or more components of the base unit 102, such as the sensor assembly 126 and / or the sensor memory circuit 142. Examples of packaging may include a plastic housing with a removable plastic or foil seal, although any suitable packaging may be used.

[0102] The wearable device 100 may be employed by removing the sterilized base unit 102 from its sterile packaging, coupling the transmitter unit 104, 104A and the base unit 102, removing the adhesive strip from the second side 122B of the adhesive layer 122, and inserting the biosensor 108 into the user using an insertion device (not shown) while attaching the base unit 102 to the surface 118S of the user's skin. Any suitable insertion device may be used to insert the biosensor 108 into the interstitial fluid region of the user.

[0103] Referring now to FIG. 6 , a flowchart of an example method 600 for continuous analyte monitoring is shown, according to embodiments provided herein. The method 600 begins at block 602, where a base unit 102 having a sensor assembly 126 and a sensor memory circuit 142 is attached to a user's skin surface 118S. The biosensor 108 is inserted into the interstitial fluid region, and the base unit 102 may be attached to the user via an adhesive layer 122 attached to the second surface 110B of the base plate 110. For example, the second side 122B of the adhesive layer 122 may be adhered to the user's skin surface 118S, such that the base unit 102 is adhered to the skin surface 118S.

[0104] In block 604, the transmitter unit 104 is coupled to the base unit 102. In block 606, the base unit 102 is powered up. For example, power may be applied to the sensor assembly 126 and / or the sensor memory circuit 142 by the battery 312. In embodiments in which the battery 312 is located within the transmitter unit 104, the base unit 102 may be powered up when the base unit 102 and transmitter unit 104 are coupled. In embodiments in which the battery is located within the base unit 102, coupling the transmitter unit 104 and base unit 102 may cause the battery to power up the base unit 102. Other suitable forms of powering up may also be used, such as receiving a prompt or signal from an external device 464, 464A.

[0105] In block 608, the sensor information stored in the sensor memory circuit 142 is read or output. In some embodiments, the sensor memory circuit 142 may output the information upon power-up of the base unit 102 in block 606. In the example of FIG. 4A, the current measurement signal I MEAS and sensor information related to processing of gain function 456 may be output to memory 454 of transmitter unit 104, where analyte concentration may be at least partially calculated. In the example of FIG. 4B, gain function 456 may be output to processor 466 of external device 464A. Other sensor information such as manufacture date, model number, and the like may be processed and displayed on local display 460 and / or display 468.

[0106] Decision block 610 illustrates any queries that may be made regarding the sensor information. In decision block 610, a determination is made as to whether the sensor assembly 126 has expired. For example, a determination may be made as to whether the period between the manufacturing date of the sensor assembly 126 and the current date is greater than a predetermined period. If the sensor assembly 126 has expired, processing proceeds to block 612, where an error code may be generated. The error code may indicate that the sensor assembly 126 has expired. As described herein, other error codes may be displayed in block 612.

[0107] In some embodiments, the sensor information may include the model number of the base unit 102 as described above, and a decision block may determine whether the base unit 102 is the correct model. If the base unit 102 is not the correct model, block 612 may generate an error code. In some embodiments, the sensor information may include a security code as described above. The decision block may compare the security code to known codes, such as codes stored in memory 454 and / or receiver memory 480 and / or codes entered by a user. If the security code and other codes do not match, an error code may be generated. The security code may prevent illegal or unauthorized base units from being used with the wearable device 100.

[0108] If the result of decision block 610 is negative (NO), processing proceeds to block 614, where the transmitter unit 104, 104A and base unit 102 are employed to monitor analyte levels in the user for a first predetermined time period. Analyte monitoring performance may be constant, meaning continuously sensing at a predetermined rate or as directed by the user for a predetermined period of time. For example, the transmitter unit 104, 104A and base unit 102 may be used to monitor glucose or another analyte level for 7, 10, 14, or another number of days. Upon expiration of the period, the base unit 102 may be replaced with a new base unit. The sensor information stored in the new base unit may be read and may replace the sensor information from the previous base unit 102. Thus, analyte level processing will be based on calibration and sensor information specific to the new base unit 102.

[0109] The wearable devices described herein can be used to monitor the analyte concentration of any desired analyte. Exemplary analytes that can be detected and / or monitored include glucose, cholesterol, lactate, uric acid, alcohol, and the like. In some embodiments, the sensor assembly 126 and / or biosensor 108 can operate continuously at a constant potential relative to a reference electrode, such as an Ag / AgCl electrode or a composite reference counter electrode. The sensor assembly 126 and / or biosensor 108 can operate with two working electrodes, one dedicated to measuring a specific analyte of interest, such as glucose, with 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, and the like. In this dual-electrode operating scheme, the interfering signal can be continuously subtracted from the main signal of the analyte of interest by either simple subtraction or another algorithmic method.

[0110] While the transmitter units 104, 104A are shown as being removable and / or attachable to the top surface of the base unit 102, it will be understood that in other embodiments, the transmitter units 104, 104A are removable and / or insertable into other surfaces of the base unit 102. For example, the base unit 102, according to some embodiments, may have an opening that allows the transmitter unit 104 to be inserted into or removed from the bottom or side of the base unit 102. In other embodiments, the base unit 102 may include an opening configured to receive the transmitter unit 104. In such embodiments, a recess may be formed for a cover to cover the opening containing the transmitter unit 104.

[0111] Referring now to FIG. 7 , a flowchart illustrating a method 700 for manufacturing a base unit (e.g., base unit 102) of a stationary analyte monitor (e.g., wearable device 100) is shown. Method 700 includes, at block 702, assembling a sensor assembly (e.g., sensor assembly 126) to a base plate (e.g., base plate 110). Method 700 also includes, at block 704, assembling a sensor memory circuit (e.g., sensor memory circuit 142) to the base plate. The method further includes, at block 706, determining at least one parameter of at least one component of the base unit. Method 700 also includes, at block 708, storing information of the at least one parameter in the sensor memory circuit. In some embodiments, method 700 includes sterilizing the base unit at block 710.

[0112] Referring now to FIG. 8 , a flowchart illustrating a method 800 for subcutaneously monitoring an analyte is shown. Method 800 includes, at block 802, inserting a biosensor (e.g., biosensor 108) extending from a base unit (e.g., base unit 102) of a wearable device (e.g., wearable device 100) into subcutaneous interstitial fluid. Method 800 also includes, at block 804, coupling a transmitter unit (e.g., transmitter unit 104) of the wearable device with the base unit. Method 800 further includes, at block 806, transmitting information stored in a sensor memory circuit (e.g., sensor memory circuit 142) in the base unit to the transmitter unit, the information including at least one parameter of at least one component of the base unit. Method 800 also includes, at block 808, measuring a current passing through the biosensor. Method 800 further includes, at block 810, determining an analyte concentration based at least in part on the current and the information.

[0113] The embodiments provided herein enable flexible, ultra-thin wearable units. In some embodiments, the height of the wearable unit may be less than about 2.5 mm. This reduction in overall height may reduce contact with clothing, making it more discreet and improving the overall fit for the wearer of the wearable unit. The flexible structure and components allow the wearable unit to conform to the user's body during various activities, helping to enhance overall user comfort. Critical components may be supported by rigid reinforcements in specific locations while maintaining overall flexibility.

[0114] The wearable devices described herein further enable accurate analyte monitoring over the life of the transmitter units 104, 104A using transmitter units 104, 104A coupled to multiple different base units 102. By storing information specific to one or more parameters of one or more components of each individual base unit, accurate analyte monitoring is achieved regardless of the base unit coupled to the transmitter unit.

[0115] In some embodiments, the materials used (e.g., LSR), flexible circuit boards (e.g., substrate 152—FIG. 1), etc. provide a wearable device 100 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 device also protects the sensor site and internal hardware from fluid intrusion and other usage hazards, is easy and comfortable to apply, provides breathability / airflow in the skin-adhering areas, and generally creates a more user-friendly experience.

[0116] 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 disposable base unit for a wearable device configured for use during continuous analyte monitoring, the disposable base unit comprising: a sensor assembly including at least one biosensor configured to be subcutaneously placed; and a radiation-hardened sensor memory circuit configured to store information relating to at least one parameter of at least one component of the disposable base unit; the at least one parameter comprises a sensitivity slope of the at least one biosensor; the at least one component includes the at least one biosensor; the disposable base unit is configured to be coupled to a reusable transmitter unit of the wearable device; and the information is automatically transferred to the reusable transmitter unit via a pull signal generated by the reusable transmitter unit in response to physical coupling of the disposable base unit and the reusable transmitter unit; the transfer of information is initiated in response to the pull signal generated by the reusable transmitter unit; A disposable base unit wherein the radiation-hardened sensor memory circuit stores the information and retains the information when exposed to radiation used to sterilize the disposable base unit.

2. The at least one parameter is: a radiation-hardened version of the sensor memory circuit; and a serial number of the at least one component of the disposable base unit; The at least one parameter is a manufacturing date of the at least one component within the disposable base unit; the date of manufacture of said disposable base unit; at least one unique identifier of the at least one component of the disposable base unit; and The disposable base unit of claim 1 , including a security code for enabling association of the reusable transmitter unit with the disposable base unit.

3. 10. The disposable base unit of claim 1, comprising a connector configured to electrically couple the radiation-hardened sensor memory circuit to at least one component of the reusable transmitter unit in response to the disposable base unit and the reusable transmitter unit being physically coupled.

4. 10. The disposable base unit of claim 1, further comprising a connector configured to electrically couple the sensor assembly to at least one component of the reusable transmitter unit in response to the disposable base unit and the reusable transmitter unit being physically coupled.

5. 10. The disposable base unit of claim 1, wherein at least one of the sensor assembly and the radiation-hardened sensor memory circuit is configured to be powered by a power source located within the reusable transmitter unit.

6. 10. The disposable base unit of claim 1, wherein at least one of the sensor assembly and the radiation-hardened sensor memory circuit is configured to receive power in response to the disposable base unit and the reusable transmitter unit being physically coupled.

7. The disposable base unit of claim 1 , wherein the at least one biosensor is configured to measure glucose.

8. 10. The disposable base unit of claim 1, wherein the radiation-hardened sensor memory circuit has two external nodes: a data node and a ground node.

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