Patent Publication Number: US-2022225899-A1

Title: Subcutaneous Analyte Sensor Applicator and Continuous Monitoring System

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to continuous analyte monitoring. More particularly, the present invention relates to an analyte monitoring system having a subcutaneous insertable analyte sensor, an inserter assembly and reader. 
     2. Description of the Prior Art 
     Continuous analyte monitoring devices have been developed for implanting into a patient&#39;s skin. Continuous monitoring systems typically use a tiny implantable sensor that is inserted under the skin, or into the subcutaneous fat layer to check analyte levels in the tissue fluid. A transmitter sends information about the analyte levels by way of, for example, a wire to a monitor or wirelessly by radio waves from the sensor to a wireless monitor. These devices are typically implanted for three to seven days of use to monitor in real-time a patient&#39;s glucose level. 
     One such device is disclosed in PCT International Application Publication No. WO 2018/118061 to Thomas H. Peterson et al. A continuous glucose monitoring system and method is disclosed and has an inserter assembly for inserting a sensor through the skin and into subcutaneous tissue where an inserter housing with the sensor remains on the skin after insertion, a sensor housing cover attachable to the sensor housing after insertion where the sensor housing cover has an electronic module and a battery, and an electronic device equipped with wireless communication for communicating with the electronic module of the sensor housing cover assembly, the electronic device configured for receiving input signals from the sensor, converting the input signals to analyte date, displaying the analyte data on a user interface of the electronic device, storing the data for recall, and creating and/or sending reports of the data. 
     U.S. Patent Application Publication No. 2018/0235520 to Vivek Rao et al. Systems, devices and methods are provided for inserting at least a portion of an in vivo analyte sensor, such as a dermal sensor, for sensing an analyte level in a bodily fluid of a subject. An applicator is positioned against a skin surface and a force is applied to the applicator causing at least a portion of a sharp and an in vivo analyte sensor to be positioned in the body of the subject. In particular, disclosed herein are embodiments of applicators designed to prevent premature sharp withdrawal and/or reduce the likelihood of improper sensor insertion. Also disclosed are embodiments of applicators including sharp modules having an angled sharp which can be configured to create an insertion path for a sensor. 
     U.S. Patent Application Publication No. 2016/0058344 to Vivek Rao et al. Systems, devices, and methods are provided for the assembly and subsequent delivery of an in vivo analyte sensor. An applicator with sensor electronics is inserted into a tray containing an assembly that includes a sharp and an analyte sensor. The insertion causes the assembly to couple with the sensor electronics and form a deliverable sensor control device retained within the applicator, which can then be placed in position on a body of a user to monitor that user&#39;s analyte levels. 
     U.S. Patent Application Publication No. 2016/0058344 to Thomas H. Peterson et al. The device is an apparatus for the subcutaneous implantation of in-vivo sensors. The device is an inserter assembly for continuous glucose monitoring with medication delivery capability where the assembly has a deployment button containing a needle deployment mechanism having a sharp held in a pre-release position, a housing body in which the deployment button is movably received within a top end of the housing body where the housing body has a sensor deployment assembly containing a lumen and a sensor disposed within the lumen and extending out of the lumen to a circuit board that is part of the sensor deployment assembly. The sensor deployment assembly matingly connects to the sharp where the sharp extends beyond the sensor deployment assembly and contains the sensor not fixedly attached to the sharp, and a sensor housing releasably received within a lower end of the housing body. The sharp extends into a sensor deployment assembly recess within the sensor housing and directly above a sensor opening in a bottom of the sensor housing. 
     U.S. Pat. No. 10,213,139 to Vivek Rao et al. discloses systems, devices, and methods for the assembly and subsequent delivery of an in vivo analyte sensor. An applicator with sensor electronics is inserted into a tray containing an assembly that includes a sharp and an analyte sensor. The insertion causes the assembly to couple with the sensor electronics and form a deliverable sensor control device retained within the applicator, which can then be placed in position on a body of a user to monitor that user&#39;s analyte levels. 
     U.S. Pat. No. 10,010,280 to Manuel L. Donnay et al. discloses an apparatus for insertion of a medical device in the skin of a subject is provided, as well as methods of inserting medical devices. Embodiments include removing a substantially cylindrical cap from an inserter to expose a substantially cylindrical sleeve, removing a cover from a substantially cylindrical container holding sensor components, and fitting the sensor components into the inserter. 
     U.S. Pat. No. 9,788,771 to Gary A. Stafford discloses an automatic sensor inserter for placing a transcutaneous sensor into the skin of a living body. According to aspects of the invention, characteristics of the insertion such as sensor insertion speed may be varied by a user. In some embodiments, insertion speed may be varied by changing an amount of drive spring compression. The amount of spring compression may be selected from a continuous range of settings and/or it may be selected from a finite number of discrete settings. Methods associated with the use of the automatic inserter are also covered. 
     U.S. Pat. No. 9,750,444 to Gary A. Stafford discloses systems and methods for providing a compressible interconnect for allowing electrical communication between an electronics unit and an analyte sensor in an on-body analyte monitoring device. In other embodiments, systems and methods are provided for reducing the Z-height of an on-body analyte monitoring device by utilizing novel interconnects. 
     U.S. Pat. No. 9,402,570 to Louis Pace et al. discloses devices associated with on-body analyte sensor units are disclosed. These devices include any of packaging and/or loading systems, applicators and elements of the on-body sensor units themselves. Also, various approaches to connecting electrochemical analyte sensors to and/or within associated on-body analyte sensor units are disclosed. The connector approaches variously involve the use of unique sensor and ancillary element arrangements to facilitate assembly of separate electronics assemblies and sensor elements that are kept apart until the end user brings them together. 
     U.S. Pat. No. 5,299,571 to John Mastrototaro discloses a device for implantation of in-vivo sensors. The apparatus includes a housing, a dual-lumen tube extending therefrom, and an in-vivo sensor received within one of the lumens of the tube. A needle is received within the other lumen of the tube, and is used to insert the tube through the skin. After implantation, the needle is removed, and the flexible tube and sensor remain beneath the skin. 
     U.S. Patent Application Publication 2010/0022863 (2010, Mogensen et al.) discloses an inserter for a transcutaneous sensor. The inserter includes a needle unit and a sensor housing. The needle unit includes a needle hub and a carrier body. The sensor housing and the needle hub are releasably connected and when they are connected, the insertion needle is placed along the sensor (e.g. surrounding the sensor wholly or partly). The carrier body guides the movement relative to the housing between a retracted and an advanced position. When released, the needle unit and the sensor housing are forced by a spring unit to an advanced position where the needle and sensor are placed subcutaneously. Upwardly-bent parts on the leg of the housing set the insertion angle of about 30° into the skin of the patient. 
     U.S. Patent Application Publication 2012/0226122 (2012, Meuniot et al.) discloses an inserter device for an analyte sensor. The device includes a housing that is positioned above the subcutaneous fat layer, a blade shuttle, and a sensor shuttle. A spring is compressed between the blade shuttle and the sensor shuttle. The blade shuttle and sensor shuttle move towards the subcutaneous fat layer. When a spring force is released by the spring, the blade shuttle moves towards and pierces into the subcutaneous fat layer creating a pathway into the subcutaneous fat layer. The analyte sensor is implanted by the sensor shuttle by following the blade shuttle into the pathway created by the blade shuttle. The blade shuttle is then retracted from the subcutaneous fat layer, leaving the analyte sensor in the fat layer. 
     U.S. Patent Application Publication 2013/0256289 (2013, Hardvary et al.) discloses a diagnostic device. The diagnostic device has partially retractable hollow guide needles for the intradermal placement of diagnostic elements fixedly connected to measuring means within this device. This obviates the need to remove the guide needle and to connect the diagnostic elements to the measuring means after placement into the skin. 
     SUMMARY OF THE INVENTION 
     In the present disclosure, the term “substantially simultaneously” means that the individual actions that occur within a subcutaneous sensor insertion applicator of the present invention when the insertion applicator is activated by a user/patient to insert a sensor subcutaneously in the skin of a patient (i.e. to assemble the sensor module as a single unit, to insert the sensor subcutaneously, to retract the needle assembly, to turn on the power switch to the electro-sensor assembly, to release the sensor module from the applicator module, and to release the applicator module from the surface of the skin) cannot be perceived by a human during the sensor insertion process. 
     It is an object of the present invention to provide an all-inclusive, single use, continuous analyte monitoring system. 
     The present invention achieves these and other objectives by providing continuous analyte monitoring system and method that includes an applicator module for inserting a sensor through the skin and into subcutaneous tissue where a sensor module remains on the skin after insertion and an electronic display device such as, for example, a smart phone and the like that is equipped with wireless communication for communicating with the sensor module, the electronic display device configured for receiving input signals from the sensor, converting the input signals to analyte data, displaying the analyte data on a user interface of the electronic device, storing the data for recall, and creating and/or sending reports of the data. Various sensors, needles and electronic display devices are disclosed in PCT Patent Application Publication No. WO 2018/118061 to Thomas H. Peterson et al., which publication is herein incorporated by reference in its entirety. 
     In one embodiment, there is disclosed an all-inclusive, single-use, subcutaneous analyte sensor applicator and monitoring system. The system includes an inserter module and a sensor module. The inserter module includes an applicator housing, a deployment button where the applicator housing is partially received within a button chamber, and a pre-loaded insertion assembly completely disposed and secured within the button chamber and partially disposed within the applicator housing chamber when the deployment button is in an initial, loaded position. The pre-loaded insertion assembly includes an assembly housing, a biasing element disposed within an assembly housing chamber, and a needle assembly disposed within the assembly housing chamber where the biasing element is in a compressed state between the needle assembly and an assembly housing bottom. The sensor module includes a sensor lower housing releasably connected to the applicator housing, a sensor upper housing removably retained against the insertion assembly housing and spaced from the sensor lower housing, and an electro-sensor assembly disposed within the sensor upper housing where (a) the electro-sensor assembly has an electronic circuit with a power switch and a sensor electrically coupled to the electronic circuit and (b) where the sensor is temporarily disposed within a needle of the needle assembly when the applicator system is in the initial pre-loaded position. 
     In another aspect of the invention, the applicator housing has an applicator elongated body defining the applicator housing chamber, a proximal internal body flange portion and an applicator housing retaining arm adjacent a proximal applicator housing end. 
     In another embodiment, the deployment button has a button elongated body defining the button chamber, a closed button distal end and a button retaining arm extends within the button chamber from the closed button distal end toward an open button proximal end a predefined distance. 
     In one embodiment, the assembly housing has an assembly housing body having an assembly circumferential wall defining the assembly housing chamber, a closed housing proximal end, a recessed housing bottom at the closed housing proximal end, an open housing distal end, an assembly housing retaining arm formed in the assembly circumferential wall and extending toward the closed housing proximal end, a plurality of housing retaining fingers formed in the assembly circumferential wall and extending toward and beyond the closed housing proximal end and having an inward-facing housing finger hook surface, an assembly housing locking slot that interacts with the button retaining arm to secure the pre-loaded insertion assembly within the button chamber, and a needle assembly locking slot that interacts with the needle body retaining arm. 
     In one embodiment, the biasing element is positioned on one end against a recessed housing bottom of the assembly housing. 
     In one embodiment, the needle assembly has a needle body with a needle body circumferential wall, a closed needle body distal end forming a needle body top, an open needle body proximal end where the needle body retaining arm is formed in the needle body circumferential wall to thereby position an outward-facing needle retaining arm hook surface adjacent to the closed needle body distal end, and a needle receiving portion formed in the needle body top where a needle is secured adjacent a needle distal end and extends parallel to the needle body circumferential wall a predefined distance beyond the open needle body proximal end and where the biasing element is positioned against the closed needle body distal end through the open needle body proximal end. The outward-facing needle is offset from a central axis of the insertion applicator. 
     In one embodiment, the sensor lower housing has a plurality of lower housing locking elements extending upward a predefined distance from a lower housing bottom into the applicator housing chamber. 
     In one embodiment, the sensor lower housing has a lower housing locking recess in a lower housing wall where the applicator housing retaining arm engages the lower housing locking recess when the deployment button is in the initial pre-loaded position. 
     In one embodiment, the sensor upper housing has an upper housing circumferential wall extending from the upper housing top forming a housing top flange portion in a perimeter of the upper housing top. The upper housing circumferential wall has a plurality of upper housing locking recesses adapted for mating connection to a plurality of locking elements of the sensor lower housing. 
     In one embodiment, the electro-sensor assembly includes a power source coupled between the electronic circuit and the power switch. 
     In another embodiment of the inserter assembly, the bottom surface of the sensor housing is configured to adhere to the patient during implantation of the sensor. In one embodiment, for example, the sensor deployment locking mechanism includes one or more bores with a resilient deployment catch extending upward from an inside bottom surface of the sensor housing, where the resilient deployment catch is biased to engage a deployment catch surface of the one or more bores in the sensor deployment assembly. 
     In another embodiment of the inserter assembly, the sensor, when implanted subcutaneously in the patient, has a working electrode of an electrode system on the sensor extending into the patient by about 4 mm to about 7 mm. In another embodiment, the sensor, when implanted subcutaneously in the patient, has a working electrode of an electrode system on the sensor extending into the patient by about 2 mm to about 10 mm. 
     Another aspect of the present invention is directed to a multi-layer, thin-film substrate assembly for use in forming a subcutaneous analyte sensor. In one embodiment, the substrate assembly has a base layer made of an electrically-insulating material, where the base layer has a base layer substrate with a base layer proximal end portion, a base layer distal end portion, and a base layer middle portion extending longitudinally between the base layer proximal end portion and the base layer distal end portion. 
     A first metallized layer is disposed on the base layer substrate and defines at least one circuit extending longitudinally along the base layer substrate. Each circuit has an electrically-conductive contact pad formed at each of the base layer proximal end portion and the base layer distal end portion with an electrically-conductive trace electrically coupling the electrically-conductive contact pad at the base layer proximal end portion with the electrically-conductive pad at the base layer distal end portion. 
     A middle layer is disposed over the base layer, where the middle layer has a middle layer substrate made of an electrically-insulating material with a second proximal end portion, a second distal end portion, and a second middle portion. The middle layer is aligned with the base layer and has a plurality of middle layer through openings with side walls. Each of the middle layer through openings is in communication with a respective one of the electrically-conductive contact pad of the circuit(s) of the base layer. 
     A second metallized layer is disposed on the middle layer and the side walls of the through openings. The second metallized layer defines at least two circuits, where each of the circuits of the second metallized layer has an electrically-conductive contact pad formed at the second proximal end portion and at the second distal end portion with an electrically-conductive trace electrically coupling the electrically-conductive contact pad at the middle layer second proximal end portion with the electrically-conductive pad at the middle layer distal end portion. One of the circuits is electrically coupled to the circuit(s) of the base layer by way of the plurality of middle layer through openings. 
     A top layer made of an electrically-insulating material is disposed over the middle layer. The top layer has a plurality of contact openings that coincide with each electrically-conductive contact pad of the middle layer proximal end portion and a plurality of sensor openings that coincide with each electrically-conductive contact pad of the middle layer distal end portion, thereby creating a substrate assembly with an substrate proximal end portion, an substrate distal end portion and an assembly middle portion extending longitudinally between the substrate proximal end portion and the substrate distal end portion. Each electrically-conductive contact pad at the second distal end portion is adapted to receive an electrode reagent to form a respective electrode and each electrically-conductive contact pad at the second proximal end portion is adapted to receive an electrical contact. 
     In another embodiment, the multi-layer, thin-film substrate assembly has multiple middle layers. 
     In another embodiment, the base layer, the circuit(s) of the first metallized layer, the middle layer, the middle layer circuits, and the top layer together impart an arcuate shape to the substrate assembly from the substrate proximal end portion to the substrate distal end portion. 
     In another embodiment of the substrate assembly, the electrically insulating material of each of the base layer, the middle layer, and the top layer is polyimide that is spun-formed and thermally cured. 
     In one embodiment of the substrate assembly, for example, the base layer and the middle layer have a thickness of about 10 microns. In another embodiment of the substrate assembly, the top layer has a thickness about five times the thickness of the middle layer. In another embodiment of the substrate assembly, the top layer has a thickness of about 55 microns. In another embodiment of the substrate assembly, the sensor assembly has a thickness of about 75 microns. In yet another embodiment, each of the substrate distal end portion and the assembly middle portion has a width of about 279 microns. 
     In another embodiment of the substrate assembly, the first metallized layer has a thickness in the range of about 900 Angstroms to about 1,500 Angstroms. 
     In another embodiment of the substrate assembly, the first metallized layer and the second metallized layer each includes gold. In another embodiment, the first metallized layer and the second metallized layer each includes a layer of chromium disposed against the base layer substrate and the middle layer substrate, respectively, and a layer of gold disposed on top of the layer of chromium. In another embodiment, the second metallized layer includes a layer of chromium disposed against the middle layer substrate, a layer of gold disposed on top of the layer of chromium, and a layer of platinum disposed on top of the layer of gold. 
     In another embodiment of the substrate assembly, the base layer has at least two circuits with respective electrically-conductive pads for each circuit at the base layer proximal end portion and the base layer distal end portion. The middle layer has at least two second-layer circuits with electrically-conductive pads for each second-layer circuit at the middle layer proximal end portion and the middle layer distal end portion. In one embodiment, for example, the first metallized layer of the base layer includes at least two additional electrically-conductive contact pads at the base layer distal end portion that aligns and coincides with the electrically-conductive pads at the middle layer distal end portion. 
     Another aspect of the present invention is directed to an electrochemical sensor assembly for use as a subcutaneous analyte sensor. In one embodiment, the electrode assembly has a base layer with a base layer substrate of electrically-insulating material that defines a base layer proximal end portion, a base layer distal end portion, and a base layer middle portion between the base layer proximal end portion and the base layer distal end portion. The base layer also has a first metallized layer disposed on the base layer substrate and defining at least one circuit extending longitudinally along the base layer substrate. Each circuit has an electrically-conductive contact pad formed at each of the base layer proximal end portion and the base layer distal end portion. An electrically-conductive trace electrically couples the electrically-conductive contact pad at the base layer proximal end portion with the electrically-conductive pad at the base layer distal end portion. 
     A middle layer is disposed over the base layer and has a middle layer substrate of electrically-insulating material. The middle layer substrate has a middle layer proximal end portion, a middle layer distal end portion, and a middle layer middle portion, where the middle layer is aligned with the base layer and has a plurality of second-layer through openings with side walls. Each of the plurality of second-layer through openings is in communication with a respective one of the electrically-conductive contact pad of the at least one circuit of the base layer. A second metallized layer is disposed on the middle layer substrate and the side walls of the second-layer through openings. The second metallized layer defines at least two circuits, where each of the second-layer circuits has an electrically-conductive contact pad formed at each of the middle layer proximal end portion and the middle layer distal end portion with an electrically-conductive trace electrically coupling the electrically-conductive contact pad at the middle layer proximal end portion with the electrically-conductive pad at the middle layer distal end portion. One of the at least two second-layer circuits is electrically coupled to the at least one circuit of the base layer by way of the plurality of second-layer through openings. 
     A top layer of electrically-insulating material is disposed over the middle layer. The top layer has a plurality of contact openings that coincide with each electrically-conductive contact pad of the middle layer proximal end portion and a plurality of sensor wells that coincide with each of the electrically-conductive contact pad of the middle layer distal end portion, thereby creating a substrate assembly with an substrate proximal end portion, an substrate distal end portion and an assembly middle portion extending longitudinally between the substrate proximal end portion and the substrate distal end portion. 
     A sensing layer is disposed on at least one electrically-conductive contact pad formed at the middle layer distal end portion to form at least a first working electrode. A reference layer is disposed on at least one electrically-conductive contact pad formed at the middle layer distal end portion forming a reference electrode. In another embodiment, there is further included a counter electrode and at least a second working electrode (also called a blank electrode because it is used to measure background current caused by interferents in the sample and not to measure a specific analyte). In still other embodiments, there are one or more additional working electrodes adapted to measure other specific analytes. In one embodiment, the at least first working electrode is a glucose measuring electrode. 
     In one embodiment, sensing layer includes three coating layers. A base coating later disposed directly on the metallized pad use to form a working electrode that contains PHEMA and glucose oxidase and/or glucose dehydrogenase, a second coating layer disposed directly on the base coating layer that contains PHEMA and a plurality of microspheres made of a material having substantially no or little permeability to glucose but a substantially high permeability to oxygen, and a third coating layer over the second coating layer, the third coating layer containing PHEMA and a material that prevents release of hydrogen peroxide from the sensing layer. In one embodiment, the microspheres are made from polydimethylsiloxane. In one embodiment, the third coating layer contains catalase. 
     In another embodiment, the base coating layer contains PHEMA, glucose oxidase and/or glucose dehydrogenase and a quantity of microspheres that is less that the quantity of microspheres in the second coating layer. 
     In another embodiment of the electrochemical sensor assembly, the base layer, the at least one circuit, the middle layer, the at least second-layer one circuit, and the top layer together impart an arcuate shape to the substrate assembly from the substrate proximal end portion to the substrate distal end portion. 
     In another embodiment of the electrochemical sensor assembly, each of the base layer substrate, the middle layer substrate, and the top layer substrate are polyimide that is spun-formed and thermally cured. 
     In another embodiment of the electrochemical sensor assembly, the base layer substrate and the middle layer substrate each have a thickness of about 10 microns. In another embodiment, the top layer has a thickness about five times the thickness of the middle layer substrate. In another embodiment, the top layer has a thickness of about 55 microns. In another embodiment, the sensor assembly has a thickness of about 75 microns. In another embodiment, each of the substrate distal end portion and the assembly middle portion has a width of about 279 microns. 
     In another embodiment of the electrochemical sensor assembly, the first metallized layer has a thickness in the range of about 900 Angstroms to about 1,500 Angstroms. In one embodiment, the first metallized layer and the second metallized layer each includes gold. In another embodiment, the first metallized layer and the second metallized layer each includes a layer of chromium disposed against the base layer substrate and the middle layer substrate, respectively, and a layer of gold disposed on top of the layer of chromium. 
     In another embodiment of the electrochemical sensor assembly, the second metallized layer includes a layer of chromium disposed against the middle layer substrate, a layer of gold disposed on top of the layer of chromium, and a layer of platinum disposed on top of the layer of gold. 
     In another embodiment of the electrochemical sensor assembly, the base layer includes at least two circuits, where one electrically-conductive pad with the sensing layer at the middle layer distal end portion forms a working electrode circuit, and where a second electrically-conductive pad at the middle layer distal end portion forms a blank electrode. 
     In another embodiment of the electrochemical sensor assembly, the base layer has at least two circuits and the middle layer has at least 2 circuits with respective electrically-conductive pads for each circuit at the respective distal end portion and the proximal end portion. In another embodiment, the first metallized layer of the base layer includes at least two additional electrically-conductive contact pads at the base layer distal end portion that align and coincide with the electrically-conductive pads at the middle layer distal end portion. 
     In another embodiment of the present invention, there is discloses a continuous glucose monitoring system. The system has an inserter assembly, a sensor housing cover assembly, and an electronic device. The inserter assembly has an inserter housing, a deployment button disposed within the inserter housing such that the deployment button is slidable from a first position to a second position only for deployment of a subcutaneous sensor into subcutaneous tissue through the skin, and a sensor housing for receiving and capturing a sensor deployment assembly from the deployment button where the sensor deployment assembly has a subcutaneous sensor. The sensor housing cover assembly configured for attachment to the sensor housing after insertion of the subcutaneous sensor where the cover assembly has an electronic module positioned for electronic coupling to the subcutaneous sensor and capable of storing and transmitting calculated data based on the input signals from the sensor. The electronic device is equipped with wireless communication for communicating with the electronic module of the sensor housing cover assembly. The electronic device having electronic circuits and software for receiving input signals from the sensor, converting the input signals to analyte data, displaying the analyte data on a user interface of the electronic device, storing the data for recall, and creating and/or sending reports of the data. 
     In another embodiment, the sensor of the continuous glucose monitoring system has a base layer with a base electrical circuit, a middle layer with middle electrical circuit where the middle layer has openings to the base layer electrically connecting portions of the middle electrical circuit with portions of the base electrical circuit. 
     In another embodiment, a method of inserting a sensor subcutaneously is disclosed. The method includes providing an all-inclusive, single-use, subcutaneous analyte sensor applicator and monitoring system containing an inserter module coupled with a sensor module where the system is preassembled, pre-loaded and ready to use because no assembly of any portion of the system is required by the user before placement of the system on the skin of a patient and no other manipulation of the system is required by the user to power an electronic circuit within the sensor module either before or after activation of the system and insertion of the sensor subcutaneously, placing the system against a skin of a patient, and actuating the inserter assembly where the actuating step causes the applicator system to perform the following at substantially the same time: to assemble the sensor module as a single unit, to insert the sensor subcutaneously, to retract the needle assembly, to turn on the power switch to the electro-sensor assembly, to release the sensor module from the applicator module, and to release the applicator module from the surface of the skin automatically. assembling of the sensor module as a single unit against the skin of the patient, implanting the sensor subcutaneously, automatically powering the electronic circuit, and automatically separating the inserter module from the assembled sensor module. 
     In one embodiment, the providing step includes removing an adhesive tape cover from a bottom of the applicator housing before the placing step. 
     In one embodiment, the actuating step includes pushing a deployment button from an initial loaded position on an applicator housing toward the skin of the animal such that a needle containing a sensor penetrates the skin and inserts the sensor leaving the sensor deployed while the needle completely retracts into an assembly housing located within the deployment button while the deployment button locks into a second position on the application housing and the applicator housing separates from the lower sensor housing. 
     In another embodiment, the providing step includes attaching a double-sided adhesive pad having a pad opening to an open proximal body end of an applicator housing of the inserter module before the placing step such that the pad opening of the adhesive pad is aligned with a needle axis of the needle. 
     In another embodiment, a method of making an all-inclusive, single-use, subcutaneous analyte sensor applicator and monitoring system is disclosed. The method includes forming each of the following: (a) an applicator housing defining an applicator housing chamber and an applicator housing retaining arm, (b) a deployment button defining a button chamber and a button retaining arm, (c) an assembly housing defining an assembly housing chamber, an assembly housing retaining arm formed in the assembly housing and having an outward-facing housing arm hook surface, (d) a biasing element, (e) a needle assembly having a needle body and a needle fixedly attached to the needle body where the needle extends a predefined distance beyond the needle body defining a needle axis, (f) a sensor lower housing having a power actuator and a lower housing opening adapted for receiving the needle, (g) a sensor upper housing having an upper housing top with a housing top opening, and (h) an electro-sensor assembly having an electronic circuit with a power switch and a sensor electrically coupled to the electronic circuit, followed by disposing the biasing element within the assembly housing chamber of the assembly housing, inserting the needle assembly within the assembly housing chamber so that the needle body contacts the biasing element and then pushing the needle body into the assembly housing chamber to compress the biasing element until a needle body retaining arm locks into a needle assembly locking slot of the assembly housing such that the needle extends beyond a closed housing proximal end and through a housing proximal end opening, inserting the combined needle assembly, the biasing element and the assembly housing into the button chamber of the deployment button until the button retaining arm of the deployment button locks into an assembly housing locking slot of the assembly housing, attaching the sensor upper housing to the assembly housing containing the needle assembly and the biasing element such that a needle of the needle assembly extends through an upper housing top opening of the sensor upper housing, inserting the electro-sensor assembly into the sensor upper housing such that the sensor is positioned within the needle where the assembly housing, the biasing element, the needle assembly, the sensor upper housing, and the electro-sensor assembly form a pre-loaded insertion assembly, attaching the sensor lower housing to an open proximal body end of the applicator housing, and inserting a portion of the applicator housing into the button chamber a predefined distance such that an applicator body circumferential wall at an open distal body end of the applicator housing slides between the assembly housing and the deployment button until an assembly housing retaining arm catches into a distal applicator housing notch in applicator body circumferential wall. 
     In one embodiment, the method further includes attaching a double-sided adhesive pad having a pad opening to the open proximal body end of applicator housing such that the pad opening of the adhesive pad is aligned with the needle axis and the adhesive material facing the bottom of the applicator housing only covers and attaches to the sensor lower housing and not to the applicator housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of one embodiment of the present invention showing a ready-to-use subcutaneous sensor applicator. 
         FIG. 1B  is a bottom perspective view of the applicator of  FIG. 1  showing the adhesive pad. 
         FIG. 2  is a front plan view of the applicator of  FIG. 1 . 
         FIG. 3  is a left side plan view of the applicator of  FIG. 1 . 
         FIG. 4  is an exploded view of the applicator of  FIG. 1 . 
         FIG. 5  is a front perspective view of one embodiment of a deployment button of the applicator. 
         FIG. 6  is a front plan view of the deployment button of  FIG. 5 . 
         FIG. 7  is a cross-sectional view of the deployment button of  FIG. 5  taken along line F 7 -F 7 . 
         FIG. 8  is a cross-sectional view of the deployment button of  FIG. 5  taken along line F 8 -F 8 . 
         FIG. 9  is a top view of the deployment button of  FIG. 5 . 
         FIG. 10  is a bottom view of the deployment button of  FIG. 5 . 
         FIG. 11  is a front perspective view of one embodiment of an applicator housing of the applicator in  FIG. 4 . 
         FIG. 12  is a front plan view of the applicator housing of  FIG. 11 . 
         FIG. 13  is a cross-sectional view of the applicator housing of  FIG. 11  taken along line F 13 -F 13 . 
         FIG. 13A  is an enlarged view of one embodiment of a cam wall surface of  FIG. 13 . 
         FIG. 13B  is an enlarged view of the needle assembly housing stop  38  of  FIG. 13   
         FIG. 14  is a cross-sectional view of the applicator housing of  FIG. 11  taken along line F 14 -F 14 . 
         FIG. 15  is a top view of the applicator housing of  FIG. 11 . 
         FIG. 16  is a bottom view of the applicator housing of  FIG. 11 . 
         FIG. 17  is a front perspective view of one embodiment of a sensor lower housing of the applicator in  FIG. 4 . 
         FIG. 18  is a front plan view of the sensor lower housing of  FIG. 17 . 
         FIG. 19  is a cross-sectional view of the sensor lower housing of  FIG. 17  taken along line F 19 -F 19 . 
         FIG. 20  is a cross-sectional view of the sensor lower housing of  FIG. 17  taken along line F 20 -F 20 . 
         FIG. 20A  is an angled perspective view of the inside bottom of the sensor lower housing showing one embodiment of the power activator shown in  FIG. 20 . 
         FIG. 21  is a top view of the sensor lower housing of  FIG. 17 . 
         FIG. 22  is a bottom view of the sensor lower housing of  FIG. 17 . 
         FIG. 23  is a front perspective view of one embodiment of an insertion assembly housing of the applicator of  FIG. 4 . 
         FIG. 24  is a front plan view of the insertion assembly housing of  FIG. 23 . 
         FIG. 25  is a cross-sectional view of the insertion assembly housing of  FIG. 23  taken along line F 25 -F 25 . 
         FIG. 26  is a cross-sectional view of the insertion assembly housing of  FIG. 23  taken along line F 26 -F 26 . 
         FIG. 27  is a top view of the insertion assembly housing of  FIG. 23 . 
         FIG. 28  is a bottom view of the insertion assembly housing of  FIG. 23 . 
         FIG. 29  is a bottom perspective view of the insertion assembly housing of  FIG. 23 . 
         FIG. 30  is a front perspective view of one embodiment of a needle assembly of the applicator. 
         FIG. 31  is a front plan view of the needle assembly of  FIG. 30 . 
         FIG. 32  is a cross-sectional view of the needle assembly of  FIG. 30  taken along line F 32 -F 32 . 
         FIG. 33  is a cross-sectional view of the needle assembly of  FIG. 30  taken along line F 33 -F 33 . 
         FIG. 34  is a top view of the needle assembly of  FIG. 30 . 
         FIG. 35  is a bottom view of the needle assembly of  FIG. 30 . 
         FIG. 36  is a front, top, perspective view of one embodiment of a sensor upper housing containing one embodiment of an electro-sensor assembly. 
         FIG. 36A  is an exploded view of the inserter assembly of  FIG. 36 . 
         FIG. 37  is a rear, bottom, perspective view of the sensor upper housing and the electro-sensor assembly of  FIG. 36 . 
         FIG. 38  is a front, top, perspective view of the sensor upper housing of  FIG. 36 . 
         FIG. 38A  is an enlarged view of an upper housing retaining recess. 
         FIG. 39  is a front plan view of the sensor upper housing of  FIG. 38 . 
         FIG. 40  is a cross-sectional view of the sensor upper housing of  FIG. 38  taken along line F 40 -F 40 . 
         FIG. 41  is a cross-sectional view of the sensor upper housing of  FIG. 38  taken along line F 41 -F 41 . 
         FIG. 42  is a rear, perspective, bottom view of one embodiment of the electronic circuit of the electro-sensor assembly shown in  FIG. 37 . 
         FIG. 43  is a front, perspective, top view of the electronic circuit shown in  FIG. 42 . 
         FIG. 44  is an enlarged, perspective, bottom view of the electronic circuit of  FIG. 42  in the area delineates as F 44  showing a power switch. 
         FIG. 45  is a rear, perspective view of one embodiment of a sensor of the electro-sensor assembly. 
         FIG. 46  is a front, perspective view of the sensor of  FIG. 45 . 
         FIG. 47  is an enlarged, front view of the sensor of  FIG. 46 . 
         FIG. 48  is a left-side, cross-sectional view of the applicator system of  FIG. 1  taken along line F 48 -F 48  in  FIG. 1  showing the applicator system is a ready-to-use state. 
         FIG. 49  is a front, cross-sectional view of the applicator system of  FIG. 1  taken along line F 49 -F 49  in  FIG. 1 . 
         FIG. 50A  is an enlarged view of the applicator system of  FIG. 49  within an area delineated as F 50 A showing an outward-facing button retaining arm engaged in an insertion assembly housing locking slot. 
         FIG. 50B  is an enlarged view of the applicator system of  FIG. 49  within the area delineated as F 50 B. 
         FIG. 51  is a left-side, cross-sectional view of the applicator system of  FIG. 48  showing the applicator system partially deployed just before releasing contact of the various retaining arms. 
         FIG. 52  is an enlarged, cross-sectional view of the applicator system of  FIG. 51  within an area delineated as F 52  showing an outward-facing needle retaining arm hook surface immediately before full deployment and needle body release. 
         FIG. 53  is a front, cross-sectional view of the application system of  FIG. 51 . 
         FIG. 54  is an enlarged, cross-sectional view of the applicator system of  FIG. 53  within an area delineated as F 54  showing an inward-facing applicator housing retaining arm immediately before full deployment and sensor module release. 
         FIG. 55  is a left-side, cross-sectional view of the applicator system of  FIG. 48  showing the applicator system fully deployed with the needle assembly retracted within the insertion assembly housing. 
         FIG. 56  is an enlarged, cross-sectional view of the applicator system of  FIG. 55  within an area delineated F 56  showing the needle body against the closed button distal end. 
         FIG. 57  is a front, cross-sectional view of the applicator system of  FIG. 55  fully deployed. 
         FIG. 58  is an enlarged, cross-sectional view of the applicator system of  FIG. 57  within an area delineated as F 58  showing the inward-facing applicator housing retaining arm fully released from the sensor lower housing locking recess. 
         FIG. 59  is an enlarged cross-sectional view of the ready-to-use orientation of the assembly housing retaining arm and the elongated cam wall surface of the applicator housing. 
         FIG. 60  is an enlarged cross-sectional view of the fully deployed orientation of the assembly housing retaining arm and the elongated cam wall surface of the applicator housing. 
         FIG. 61  is right-side plan view of the fully deployed sensor applicator system showing the sensor module deployed and separated from the applicator module. 
         FIG. 62  is a front plan view of the fully deployed sensor applicator of  FIG. 61 . 
         FIG. 63  is a perspective view of one embodiment of a sharp of the present invention showing the sharp tip, a sharp open region, and a portion of the sharp body. 
         FIG. 64  is an end perspective view of the sharp of  FIG. 64  showing the concave well defined by the sharp open region. 
         FIG. 65  is a perspective view of one embodiment of a continuous monitoring system of the present invention showing a sensor applicator and display modules. 
         FIG. 66  is a schematic illustration of the continuous monitoring system of the present invention in use. 
         FIG. 67  is a perspective view of one embodiment of a multi-layer sensor. 
         FIG. 68  is an exploded perspective view of the multi-layer sensor of  FIG. 67  showing a base layer, a middle layer and a top layer. 
         FIG. 69  is a plan view of the sensor of  FIG. 67  showing the base layer only with an electrical contact portion and a sensor end portion circled. 
         FIG. 70  is an enlarged view of the electrical contact portion of  FIG. 69 . 
         FIG. 71  is an enlarged view of the sensor end portion of  FIG. 69 . 
         FIG. 72  is a plan view of the sensor of  FIG. 67  showing the middle layer only with an electrical contact portion and a sensor end portion circled. 
         FIG. 73  is an enlarged view of the electrical contact portion of  FIG. 72 . 
         FIG. 74  is an enlarged view of the sensor end portion of  FIG. 72 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This disclosure is not limited to the particular embodiment(s) described herein, which embodiments may vary, and the terminology used to describe these particular embodiments is not intended to be limiting. 
     The present invention is illustrated in  FIGS. 1-74 .  FIG. 1  is a front perspective view of one embodiment of a ready-to-use subcutaneous sensor applicator  10 .  FIG. 1B  is a bottom perspective view of applicator  10  showing a single-sided adhesive pad  14  with an adhesive pad cover  12 . As shown, the adhesive pad cover  12  is clear only for the purpose of showing the location of an adhesive layer  13 , but adhesive pad cover  12  may be opaque. As illustrated, an adhesive layer  13  of adhesive pad  14  aligns with an external housing flange portion  27  of applicator housing  21  and an adhesive pad opening  14   a  that aligns with a needle axis L 2  (shown in  FIGS. 32-33 ). The non-adhesive side of the single-sided adhesive pad  14  is bonded to lower housing bottom  172  (shown in  FIG. 22 ) of a sensor lower housing  170  by welding.  FIGS. 2 and 3  are front plan and left side plan views of the applicator  10 , respectively, showing a vertical axis L 1  that extends through the middle of sensor applicator  10 . The ready-to-use subcutaneous sensor applicator  10  includes an applicator housing assembly  20  and a deployment button assembly  40 . A unique feature of the present invention over other similar devices is that the ready-to-use subcutaneous sensor applicator  10  is fully assembled where a user does not need to combine any structural components before use. The user simply removes the ready-to-use subcutaneous sensor applicator  10  from its packaging, removes the adhesive tape cover  12  from the adhesive tape  14  on the bottom of the applicator housing  20  exposing the adhesive that is aligned with the proximal external body flange portion  27 , positions the subcutaneous sensor applicator in a pre-selected location onto the user&#39;s skin or the skin of a patient, and pushes the deployment button assembly  40 . The single push of the deployment button assembly  40  causes a sensor module  160  (not shown; see  FIGS. 3 and 61-62 ) to be deployed onto the skin with an analyte sensor deployed subcutaneously in the skin and the power to the electronic circuit to be turned on automatically. The user is not required to assemble a sensor module to the applicator, or manipulate structure on the applicator to remove the deployment button assembly from the sensor module, or to perform any other task to power up the electronic circuit within the sensor module after subcutaneous insertion of the sensor. 
     Turning now to  FIG. 4 , there is illustrated an exploded, front, perspective view of the applicator  10 . Applicator  10  includes an applicator module  15  and an unassembled sensor module  160 . The applicator module  15  includes the button deployment assembly  40 , which includes a pre-loaded insertion assembly  100 , and the applicator housing assembly  20 . 
     The pre-loaded insertion assembly  100  includes an insertion assembly housing  110 , a needle assembly  140 , a biasing element  149  and an electro-sensor assembly  220 . The needle assembly  140  and the biasing element  149  are disposed within the insertion assembly housing  110  with the biasing element  149  compressed into a tensioned orientation such that the needle assembly  140  is in a ready or cocked position, and the insertion assembly housing  110  being locked within the deployment button  50 . The electro-sensor assembly  220  is captured by the insertion assembly housing  110  at a lower or proximal end of the insertion assembly housing  110  such that a portion of sensor  250  is removably positioned within the needle  155  of the needle assembly  140  when the needle assembly  140  is in the ready or cocked position. 
     The applicator housing assembly  20  includes an applicator housing  21  and a sensor lower housing  170  captured by the applicator housing  21 , which sensor lower housing  170  is released from the applicator housing  21  when the sensor applicator system is deployed. As shown in  FIGS. 1-3 , the deployment button assembly  40  is coupled to the applicator housing assembly  20  such that a portion of the insertion assembly housing  110  is within the applicator housing  21  and a portion of the applicator housing  21  is within the deployment button  50 . The various assembled structural components will now be described individually. 
     Turning now to  FIGS. 5-10 , there is illustrated various views of deployment button  50 .  FIG. 5  is a front, left-side, perspective view of deployment button  50 . Deployment button  50  has a button elongated body  52 , a closed button distal end  53  and an optional button body flange  56  disposed at an open button proximal end  54 . The button elongated body  52  has a circumferential wall  57  that defines a button chamber  58 .  FIG. 6  is a front plan view of the deployment button of  FIG. 5 . As can be seen from  FIGS. 5-10 , button elongated body  52  has a length BL that is longer than a width BW. The length BL is about 1.5 inches (3.8 cm) but this dimension is not limiting. The width BW is about 1.25 inches (3.2 cm) but this dimension is not limiting. The button chamber has a depth BD of about 1.4 inches (3.5 cm) but this dimension is not limiting. As shown in  FIGS. 5-6 and 8 , the sides of button elongated body  52  may include ridges or grooves  59  to provide better gripping of the deployment button  50  by the fingers and thumb of the user when placing on the skin of the user/patient. 
       FIG. 7  is a cross-sectional view of the deployment button of  FIG. 5  taken along line F 7 -F 7 . Within button chamber  58 , a plurality of optional elongated spacers  70  extend a predefined distance from closed button distal end  53  toward open button proximal end  54 . Also within button chamber  58 , there is an optional spacer wall  72  that extends a predefined distance from closed button distal end  53  toward open button proximal end  54  along the inside of circumferential wall  57 . Spacer wall  72  is located within button chamber  58  such that a space is created between the plurality of elongated spacers  70  and spacer wall  72 , which this space is only provided for ease of assembly during manufacturing. 
       FIG. 8  is a cross-sectional view of the deployment button of  FIG. 5  taken along line F 8 -F 8 . In addition to the plurality of optional elongated spacers  70  and the optional spacer wall  72  are at least a pair of outward-facing button retaining arms  60 . Button retaining arms  60  are connected to closed button distal end  53  and extend within button chamber  58  a predefined distance in the space created between the plurality of elongated spacers  70  and spacer wall  72 . Button retaining arms  60  are resilient such that they can be bent toward a center of the button chamber  58  and return back to their original position. At the retaining arm&#39;s end is a button retaining arm hook structure  61 . As shown in  FIGS. 7 and 8 , closed button distal end  53  has an optional recess  53   a  in an outside surface for placement of an index finger, if so desired, when activating the subcutaneous analyte sensor applicator system  10 . 
       FIG. 9  is a top view of deployment button  50 . In this view, a pair of optional closed end ports  53   b  is illustrated and looking down through the optional closed end ports  53   b,  one can see the hook structure  61  of the button retaining arms  60 . The openings  53   b  are a result of the molds used when injection molding the part. 
       FIG. 10  is a bottom view of deployment button  50 . In this view, the relationship of the plurality of elongated spacers  70  and spacer wall  72  is more clearly shown including the button retaining arms  60  and the optional button flange  56 . 
     Turning now to  FIGS. 11-16 , the structure of the applicator housing  21  will now be discussed.  FIG. 11  is a front, left-side, perspective view of applicator housing  21  and  FIG. 12  is a front plan view of applicator housing  21 . Application housing  21  has an applicator elongated body  22  formed by an applicator circumferential wall  25  that defines an applicator housing chamber  28 , an open distal body end  23 , an open proximal body end  24 , a proximal internal body flange portion  26  (shown in  FIG. 15 ), and a proximal external body flange portion  27 . The proximal external body flange portion  27  is an important feature of the applicator  10 . The purpose of the flange is that it passively applies solid even pressure on the adhesive tape using the deployment force of the mechanism. The resultant force of the 3-5 lbs. of deployment force is intentionally used to solidly set the pressure sensitive adhesive (PSA) of the adhesive tape on the skin of the user/patient. This is an important aspect of the present invention that achieves the entire integrated passiveness of the mechanism for the user. The user does not have to apply pressure to the adhesive tape to secure it to the skin of the user/patient after the sensor and applicator are simultaneously inserted and released, respectively. Applicator housing  21  also includes an inwardly-facing applicator housing retaining arms  30  formed in the applicator circumferential wall  25  where the applicator housing retaining arm  30  extend at a predefined angle from the applicator circumferential wall  25  into the applicator housing chamber  28  and terminate adjacent the open proximal body end  24 . Applicator housing retaining arm  30  is sufficiently resilient so that the arm  30  can be forced back toward the circumferential wall  25 . A plurality of spacer slots  39  extend from open distal body end  23  of the applicator elongate body  22  a predefined distance sufficient to accommodate the plurality of elongated spacers  70  of the deployment button  50 . 
       FIG. 13  is a cross-sectional view of the applicator housing of  FIG. 11  taken along line F 13 -F 13 . Besides the inward-facing applicator housing retaining arm  30 , there are two other features along the inside surface of the applicator circumferential wall  25 . These features include an elongated cam wall surface  32  and an applicator assembly housing stop  38 .  FIG. 13A  is an enlarged view of the cam wall surface  32  delineated by area F 13 A. As can be seen, an upper surface portion  32   a  has as a first surface portion recess  33 , a first sloping surface  34   a  that extends along the cam wall surface  32  away from surface portion recess  33  and slopes toward the applicator housing chamber  28 , a second sloping surface  34   b  that extends along cam wall surface  32  away from first sloping surface  34   a  and slopes away from the applicator housing chamber  28 . A cam surface  36  extends along middle surface portion  32   b  and away from second sloping surface  34   a  and slopes further away from the applicator housing chamber  28  where cam surface  36  terminates at a lower surface portion  32   c  that has a second surface portion recess  35 .  FIG. 13B  is an enlarged view of the insertion assembly housing stop  38  delineated by area F 13 B. Insertion assembly housing stop  38  is located to create an endpoint for the movement of deployment housing assembly  40  when deployment button  50  is activated.  FIG. 14  is a cross-sectional view of applicator housing of  FIG. 11  taken along line F 14 -F 14 . This view illustrates the inward-facing applicator housing retaining arms  30  with their retaining arm hook ends  30   a  and shows the retaining arms  30  as they extend at a predefined angle toward open proximal body end  24 . 
       FIG. 15  is a top view of applicator housing  21 . This view shows the retaining arm hook ends  30   a  as well as the proximal internal body flange portion  26 . In  FIG. 16 , proximal internal body flange portion  26  has a flange portion recess  26   a.  This recess is designed to accommodate the sensor lower housing  200  for the purpose of presenting coplanar surfaces between open proximal body end  24  and sensor lower housing  200  while inward-facing applicator housing retaining arms  30  hold sensor lower housing  200  until the subcutaneous analyte sensor applicator system is deployed. 
     Turning now to  FIGS. 17-22 , there is illustrated various views of one embodiment of sensor lower housing  170 .  FIGS. 17 and 18  are a front, left, perspective view and a front plan view of sensor lower housing  170 , respectively. Sensor lower housing  170  has a lower housing bottom  172 , a lower housing wall  173  that extends upward from lower housing bottom  172  defining a lower housing chamber  184 , and a circumferential bottom flange  171  that extends perpendicularly away from lower housing wall  173 . In at least two, opposed locations in lower housing wall  173 , there is a lower housing locking element  174  that is inwardly facing and used to retain sensor upper housing  200  and electro-sensor assembly  220  after deployment of the applicator system  10 . Also in at least two, opposed locations in lower housing wall  173 , there is a lower housing retainer recess  178  for receiving applicator housing retaining arm  30  for holding sensor lower housing  170  at open proximal body end  24  of applicator housing  21  prior to deployment of the applicator system  10 . Also shown are a plurality of optional flange notches  182  in circumferential bottom flange  171 , which are not required, and used only for ease of assembly of sensor lower housing  170  to applicator housing  21  and is not an essential aspect of the present invention. Extending into lower housing chamber  184  from lower housing bottom  172  is a power actuator  175  that contacts a power switch on the electro-sensor assembly  220  when sensor upper and lower housings  170 ,  200  are joined together when the sensor applicator system  10  is deployed. In this embodiment, power actuator  175  is resilient such that it has a bowed cross-sectional shape from lower housing bottom  172  into lower housing chamber  184 . This is shown in  FIG. 20A . The bowed shape provides a biasing tension by the power actuator  175  to the power switch  240  (shown in  FIG. 44 ) on electronic circuit  230  when the sensor applicator system is deployed such that the joining of sensor upper and lower housings  170 ,  200  causes the power switch  240  to depress power activator  175 , which, in turn, maintains a biasing force against power switch  240 . 
       FIGS. 19 and 20  are a cross-sectional view of sensor lower housing  170  of  FIG. 17  taken along line F 19 -F 19  and a cross-sectional view of sensor lower housing  170  of  FIG. 17  taken along line F 20 -F 20 . These views provide a more clear view of the inwardly-facing lower housing locking elements  174 , the lower housing retaining recess  178  and the power actuator  175 . 
       FIGS. 21 and 22  are a top plan view and a bottom plan view of lower sensor housing  170 , respectively. In this embodiment, there are three openings  176  references as vent openings  176   a,    176   b  and sensor opening  176   c.  Sensor opening  176   c  is for accommodating the subcutaneous sensor  250  when the sensor applicator system is deployed. Openings  176   a  and  176   b  are optional and may provide ventilation to the patient&#39;s skin to allow trapped moisture to wick out of the sensor housing  170 . 
     Turning now to  FIGS. 23-29 , there are illustrated various views of one embodiment of the insertion assembly housing  110 .  FIGS. 23 and 24  are a front perspective view and a front plan view of the insertion assembly housing  110 . Insertion assembly housing  110  includes an assembly housing body  112 , an open housing distal end  113 , a closed housing proximal end  114 , an assembly housing bottom  115 , and an assembly circumferential wall  111  defining an assembly housing chamber  118 . Assembly circumferential wall  111  includes an assembly housing locking slot  130  spaced from open housing distal end  113  that receives outwardly facing button retaining arm  60  when insertion assembly housing  110  is assembled into deployment button  50 . Once insertion assembly housing  110  is inserted and retained within deployment button  50 , it remains locked within deployment button  50  and always moves with the deployment button  50 . 
     Assembly circumferential wall  111  also includes a plurality of assembly housing retaining arms  120  where each of the retaining arms  120  have an outward-facing housing arm hook surface  121 . The retaining arms  120  reside in first surface portion recess  33  of the elongated cam wall surface  32  and lock insertion assembly housing  110  within applicator housing  21 , which effectively locks deployment button  50  to applicator housing  21  by way of the button retaining arms  60  of deployment button  50  being locked into assembly housing locking slot  130  of the assembly circumferential wall  111  of insertion assembly housing  110 . During deployment of the sensor applicator system, each assembly housing retaining arm  120  slides along the elongated cam wall surface from the first surface portion recess  33  when in the ready-to-use orientation to the second surface portion recess  35  when in the deployed orientation. 
     Another aspect of assembly circumferential wall  111  includes a plurality of housing retaining fingers  124  where each retaining finger  124  has an inward-facing finger hook surface  125 . Each retaining finger  124  extends below assembly housing bottom  115  and holds sensor upper housing  200  when the sensor applicator system  10  is in the ready-to-use orientation. Circumferential wall  111  also includes a needle assembly locking slot  132  that extends a predefined distance from closed housing proximal end  114  toward open housing distal end  113 . Needle assembly locking slot  132  is to accommodate the applicator assembly housing stop  38  of applicator housing  21 , which will interact with needle assembly  140  (to be discussed later) when sensor applicator system  10  is deployed to insert subcutaneous sensor  250 . 
     Turning now to  FIGS. 25 and 26 , there are illustrated a cross-sectional view of insertional assembly housing  110  taken along ling F 25 -F 25  and F 26 -F 26 , respectively. As shown in these figures, assembly housing bottom  115  is recessed to accommodate sensor upper housing  200  while the plurality of housing retaining fingers  124  hold sensor upper housing  200  within the recessed housing bottom  115  until released by activation of the sensor applicator system  10 . 
       FIGS. 27 and 28  illustrate a top view and a bottom view of insertion assembly housing  110 . In these views, it is clearly shown that outward-facing housing arm hook surface  121  of assembly housing retaining arm  120  extend beyond the perimeter of assembly circumferential wall  111  for engagement with elongated cam wall surface  32  of applicator housing  21  and the existence of a housing proximal end opening  116  to accommodate the needle  155  of the needle assembly  140 . Also shown is at least one optional assembly housing rail  117  that also extends along a major portion of assembly circumferential wall  111  between open housing distal end  113  and closed housing proximal end  114 , and beyond the perimeter of assembly circumferential wall  111 . This optional rail  117 , if included, would be disposed within a corresponding applicator housing channel  29  to facilitate alignment of insertion assembly housing  110  within applicator housing  21 .  FIG. 29  is a bottom perspective view of the insertion assembly housing  110  to provide a visual of the structural relationship of the assembly housing bottom  115 , the assembly housing retaining arm  120 , the housing retaining finger  124 , and needle assembly locking slot  132 . 
     Turning now to  FIGS. 30-35 , there is illustrated various views of one embodiment of a needle assembly  140 .  FIGS. 30 and 31  are a front perspective view and a front plan view of needle assembly  140 . Needle assembly  140  includes a needle body  142  and a tubular needle  155  with a needle wall  155   a  (not shown) fixedly attached to needle body  142  where the tubular needle  155  defines a needle axis L 2  (shown in  FIGS. 32, 32 ). 
       FIGS. 32 and 33  illustrate a cross-sectional view of the needle assembly of  FIG. 30  taken along line  32 - 32  and a cross-sectional view of the needle assembly of  FIG. 30  taken along line  33 - 33 , respectively. Needle  155  is located to align with housing proximal end opening  116  of insertion assembly housing  110 . Needle body  142  has a closed needle body distal end  143 , an open needle body proximal end  144 , a needle body top  145 , a needle body retaining arm  150 , and a needle-receiving portion  154 . Needle  155  has a needle wall  155   a  that forms a needle body  156  with a needle distal end  157  and a needle proximal end  158 . Needle distal end  157  is fixedly secured to needle-receiving portion  154  of needle body  142 . More specifically, the needle is fixated to the needle-receiving portion  154  with tight tolerance. A usable securing material is UV epoxy. This fixation is important because the portion of the needle wall that&#39;s removed must align closely with sensor  250 . Needle proximal end  158  includes a needle sharp  159 . Needle  155  includes a needle open region  156   a  where a portion of the needle wall  155   a  is removed. Needle open region  156   a  extends from needle proximal end  158  for a predefined distance. Needle open region  156   a  is needed to accommodate sensor  150  and to allow retraction of needle  155  after deployment of sensor  150  subcutaneously.  FIG. 32  shows the structure of needle body retaining arm  150  where retaining arm  150  has an outward-facing needle retaining arm hook surface  151  that extends beyond the needle body circumferential wall  141  when needle body retaining arm  150  is in a relaxed state. Needle body retaining arm  150  is resilient and configured such that it may be compressed toward and into needle body circumferential wall  141 .  FIG. 33  shows one embodiment of needle receiving portion  154  of needle body  142 . Needle receiving portion  154  is configured to delineate an area around which biasing element  149  resides between closed needle body distal end  143  and closed housing proximal end  114  of the insertion assembly housing  110 . When needle assembly  140  is assembled inside of assembly housing chamber  118  of the insertion assembly housing  110 , biasing element  149  is in a compressed state and needle body retaining arm  150  is located within and held by needle assembly locking slot  132  of insertion assembly housing  110  until released by interference with applicator assembly housing stop  38  of applicator housing  21  when deployment button assembly  40  is deployed to insert sensor  250  subcutaneously. When applicator assembly housing stop  38  forces needle body retaining arm  150  into needle body  142 , biasing element  149  moves to a less compressed state causing needle assembly  140  to slide toward open housing distal end  113  causing needle  155  to retract away from upper sensor housing  200 . 
       FIGS. 34 and 35  are a top view and a bottom view of needle assembly  140 . These views show the position of the needle body retaining arm  150  relative to the needle body  142 . Also shown are needle body side slots  146  that are included for two reasons: (a) to prevent any inadvertent disconnection of outwardly-facing button retaining arm  60  of the deployment button  50  from the assembly housing locking slot  130  and (b) to prevent possible interference with needle body  142  as it slides up toward deployment button top  55  after implanting sensor  250  into subcutaneous tissue. In the bottom view, an outline  149   a  of the biasing element  149  is provided to show the relative position of the biasing element  149  against the inside top surface of the needle body top  145 . 
     Turning now to  FIGS. 36 and 37 , there is illustrated a front, top, perspective view and a rear, bottom, perspective view of one embodiment of a sensor upper housing  200  containing an electro-sensor assembly  220 . The electro-sensor assembly  220  includes an electronic circuit  230  and a sensor  250 .  FIG. 36  shows a subcutaneous sensor  250  extending a predefined distance below sensor upper housing  200 .  FIG. 37  shows electro-sensor assembly  220  residing within sensor upper housing  200 . After the electro-sensor assembly  220  is assembled within sensor upper housing  200 , a potting compound  215  is applied by an automatic dispensing machine (not shown) to the sensor upper housing  200 . The potting compound  215  seeps down under the electronic circuit  230  and is filled until the potting compound  215  is just even with the base of the activation switch  240  (shown in  FIG. 44 ) and flows out to the inner circumference to the sensor upper housing  200  and the electronic circuit retainer  209 . The potting compound is typically a waterproof material, preferably a  2 -part fast-curing material.  FIG. 36A  is an exploded view of  FIG. 36  showing electro-sensor assembly  220  and sensor upper housing  200 . 
       FIGS. 38, 38A and 39  are a front, perspective view, an enlarged view of an upper housing retaining recess and a front plan view, respectively, of sensor upper housing  200 . Sensor upper housing  200  has an upper housing top  205 , an upper housing top opening  206 , a circumferential upper housing wall  207  that extends transversely away from upper housing top  205  and defines an upper housing chamber  212  (shown in  FIGS. 40, 41 ), and a housing top flange portion  208  that extends from upper housing top  205  transversely beyond circumferential upper housing wall  207 . Circumferential upper housing wall  207  also includes an upper housing locking recess  210  adjacent housing top flange portion  208 . Upper housing locking recess  210  is located for locking engagement with a corresponding lower housing locking element  174  when joined together to form sensor module  160  is deployed on a user&#39;s skin. On the inside of circumferential upper housing wall  207  is at least one electronic circuit retainer  209  that holds the electronic circuit  230  within upper housing chamber  212 . 
       FIGS. 40 and 41  are a cross-sectional view of the sensor upper housing of  FIG. 38  taken along line F 40 -F 40  and a cross-sectional view of the sensor upper housing of  FIG. 38  taken along line F 41 -F 41 , respectively. Descending from upper housing top opening  206  is a tubular upper housing needle guide  211 . Upper housing needle guide  211  has a guide distal end  211   a  and a guide proximal end  211   b.  Furthermore, the needle guide  211  extends a predefined distance such that, when sensor upper housing  200  is coupled with sensor lower housing  170 , guide proximal end  211   b  of upper housing needle guide  211  extends no further than lower housing bottom  172 . Guide proximal end  211   b  has a portion  211   c  removed to accommodate sensor  250 , which has a bend that is positioned within portion  211   c  and where a portion of sensor  250  is positioned within the needle open region of needle  155 .  FIG. 41  is a cross-sectional view of the sensor upper housing of  FIG. 38  taken along line F 41 -F 41  showing the upper housing locking recess  210 . 
     Turning now to  FIGS. 42 and 43 , there is illustrated the electronic circuit  230  without sensor  250 .  FIG. 42  is a bottom perspective view and  FIG. 43  is a top perspective view.  FIG. 43  clearly shows the battery  235  that powers electronic circuit  230 .  FIG. 42  shows a circuit power switch  240  that is in a normally off position.  FIG. 44  is an enlarge view area F 44  delineated in  FIG. 42 . Circuit power switch  240  is a frusto-conical shape above adjacent electronic components of the electronic circuit  230 . Circuit power switch  240  is positioned on electronic circuit  230  to couple with the power actuator  175  of sensor lower housing  170  when sensor upper housing  200  and sensor lower housing  170  are coupled together during sensor applicator system activation and deployment. When coupled together, power actuator  175  pushes against circuit power switch  240  which then connects power from battery  232  to electronic circuit  230  and sensor  250 . The sensor module  160  is automatically powered on when this action occurs. In other words, this action automatically occurs when the sensor applicator system  10  is deployed and the sensor module  160  deployed on the skin of the user with the sensor implanted subcutaneously. Electronic circuit  230  also includes electronic components such as, for example, a transmitter (not shown) for wireless communication of sensor and other data with an electronic device  902  such as those devices described later. 
       FIGS. 45 and 46  are front and rear views of one embodiment of sensor  250 , respectively. Sensor  250  has a sensor distal end  260 , a sensor middle portion  270  and a sensor proximal portion  280 . Sensor distal end  260  has a plurality of contact pads  262  that electrically couples to electronic circuit  230 . Sensor proximal portion  280  along with a portion of sensor middle portion  270  is implanted subcutaneously within the skin of the user/patient. A plurality of electrodes  282  are exposed at sensor proximal portion  280  where at least one of the plurality of electrodes  282  is configured to measure an analyte, such as, for example, glucose. More than one analyte may be measured provided that other of the plurality of electrodes  282  are so configured. In this embodiment, sensor  250  has a bend such that sensor proximal portion  280  is transverse, and preferably perpendicular, to sensor distal end  260 . 
       FIG. 47  is an enlarged, rear view of sensor  250  showing sensor proximal portion  280  and the plurality of electrodes  282  with sensor distal portion  260  extending away from the viewer and into the plane of the drawing. As seen, this embodiment of sensor  250  has one or more friction surfaces  284  that appear as bumps along the side of sensor proximal portion  280 . These “bumps” contact the inside surface of needle wall  155   a  in needle open region  156   a.  The frictional contact between sensor proximal portion  280 , needle wall  155   a  and the size of sensor  250  allow needle  155  to penetrate the skin of the user and implant sensor proximal portion  280  subcutaneously without damaging sensor proximal portion  280  or any portion of sensor  250  and then withdraw needle  155  leaving sensor proximal portion  280  implanted. 
     Turning now to  FIGS. 48-62 , there will be discussed the operation of the all-inclusive, ready-to-use sensor applicator system  10 .  FIGS. 48 and 49  are cross-sectional views of the applicator system  10  in a ready-to-use state.  FIG. 48  is a left-side, cross-sectional view of the applicator system  10  of  FIG. 1  taken along line F 48 -F 48  in  FIG. 1  showing the applicator system is a ready-to-use state. As illustrated, sensor applicator system  10  is packaged as ready-to-use and is all-inclusive, meaning that the user does not need to assemble a “sensor module” to an inserter or to physically connect a power source to the sensor module to operate the sensor module (i.e. to power the electronic circuit and sensor). In this all-inclusive, ready-to-use position, the needle assembly  140  is coupled inside of the insertion assembly housing  110  with the biasing element  149  in a compressed state storing potential energy used for retracting the needle  155  once deployed. The sensor upper housing  200  is retained at the closed housing proximal end  114  of the insertion assembly housing  110 . Needle  155  extends through upper housing needle guide  211  toward sensor lower housing  170  where needle proximal end  158  is position directly aligned with and adjacent the sensor opening  176   c  of sensor lower housing  170 .  FIG. 49  is a front, cross-sectional view of the applicator system of  FIG. 1  taken along line F 49 -F 49  in  FIG. 1 . This view shows outwardly-facing button retaining arms of deployment button  50  engaged in assembly housing locking slot  130  of insertion assembly housing  110 . This is more clearly shown in  FIG. 50A , which is an enlarged view within the area delineated by F 50 A in  FIG. 549 . This view also shows inwardly-facing applicator housing retaining arm  30  coupled to lower housing locking recess  178  to retain sensor lower housing  170  to application housing  21 . This is more clearly shown in  FIG. 50B , which is an enlarged view within the area delineated by F 50 B in  FIG. 49 . 
       FIGS. 51 and 53  are cross-sectional views of the applicator system  10  in a deployed orientation just before completion of the implantation of sensor  250  before needle  155  is retracted and the sensor upper and lower housings  170 ,  200  are joined to each other. The purpose is to show the spatial relationship of the relevant retaining arms and corresponding locking recesses of the various components where substantially simultaneously, the sensor module  160  is about to be completed, the needle  155  and sensor  250  are within the subcutaneous tissue of the user, the needle assembly  140  is about to be automatically retracted, and the sensor module  160  is about to be released from the applicator housing  21 .  FIG. 51  a left-side, cross-sectional view of the applicator system of  FIG. 48  showing the applicator system partially deployed just short of full deployment.  FIG. 52  is an enlarged view within the area delineated by F 52  in  FIG. 51  showing that the needle body retaining arm  150  is about to make contact with applicator assembly housing stop  38 .  FIG. 53  is a front, cross-sectional view of the application system of  FIG. 51  showing the closed housing proximal end  114  of the insertion assembly housing  110  about to make contact with the inwardly-facing applicator housing retaining arm  30 .  FIG. 54  is an enlarged view within the area delineated by F 54  in  FIG. 53 . 
       FIGS. 55 and 57  are cross-sectional views of the applicator system  10  in a deployed orientation upon completion of the implantation of sensor  250 .  FIG. 55  is a left-side, cross-sectional view of the applicator system of  FIG. 48  showing the applicator system  10  fully deployed with the needle assembly  140  retracted within the insertion assembly housing  110 . As shown, sensor upper housing  170  is coupled with sensor lower housing  200  and needle assembly  140  has been moved by the kinetic energy of released biasing element  149  where the needle body top  145  is in contact with deployment button top  55 .  FIG. 56  is an enlarged view within the area delineated by F 56  in  FIG. 55 .  FIG. 55  more clearly shows the contact between needle body top  145  and deployment button top  55 .  FIG. 57  is a front, cross-sectional view of the applicator system  10  of  FIG. 55  fully deployed. In this view, closed housing proximal end  114  had made contact with inwardly-facing applicator housing retaining arm  30  and, at its furthest most travel, has completely pushed retaining arm  30  away from sensor lower housing  170 , which releases the now formed sensor module  160  from the applicator module  15 .  FIG. 58  is an enlarged view within the area delineated by F 58  in  FIG. 57  to more clearly show how the retaining arm  30  is released from sensor lower housing  170 . 
     Turning now to  FIGS. 59 and 60  are cross-sectional views of the ready-to-use orientation and the fully deployed orientation of the assembly housing retaining arm  120  and the elongated cam wall surface  32  of the applicator housing  21 . At the ready-to-use orientation, a sufficient force against the deployment button  50  is required to overcome the resistance created by the first sloping surface  34   a  of the cam wall surface  32 , which sloping surface  34   a  causes the assembly housing retaining arm  120  to push and bias the arm  120  toward the assembly housing chamber  118  (i.e. by riding/sliding along sloping surface  34   a ) until the assembly housing retaining arm  120  reaches second sloping surface  34   b  of the cam wall surface  32 . The initial force applied against the deployment button  50  coupled with the force of the biased arm  120  causes the deployment button to continue to move without additional force required to its fully deployed position as the assembly housing retaining arm  120  follows along the second sloping surface  34   b  and the cam surface  36  which continues to slope away (i.e. outwardly) applicator housing chamber  28  until assembly housing retaining arm  120  reaches second surface portion recess  35  of the elongated cam wall surface  32 . At this point downward movement of deployment button assembly  40  ceases since the sensor module  160  is fully deployed. 
       FIGS. 61 and 62  are a right-side plan view and a front plan view of the fully deployed sensor applicator system  10  showing the sensor module  160  deployed and separated from the applicator module  15  with sensor  250  deployed subcutaneously within the skin of the user/patient. 
     Needle/sharp 
       FIGS. 63 and 64  illustrate perspective views of one embodiment of a needle/sharp  300  of the present invention. Needle/sharp  300  includes a sharp body  302 , a sharp open region  304 , and a sharp tip  306 . Sharp body  302  is an annular section of sharp  300  that extends longitudinally and defines an enclosed conduit  301  therethrough. 
     A wire EDM machining operation or a laser operation is used to remove a portion of the tubing wall  303  along sharp  300  a predefined distance to define sharp open region  304 , thereby reducing the overall height  310  of sharp  300 . Both the wire EDM machining operation and the laser operation can be performed on cylindrical tubing or on flattened, oval tubing. Sharp open region  304  is a section of an annulus that extends longitudinally with the tubing wall  303  along the length of sharp open region  304  defining an unenclosed concave well  314  from sharp tip  306  to sharp body  302 . Concave well  214  is sized to receive a continuous monitoring sensor  250 . 
     CGM System 
     Referring now to  FIGS. 65 and 66 , there is illustrated one embodiment of the CGM system  1000  of the present invention. CGM system  1000  includes subcutaneous analyte sensor applicator  10 , and an electronic device  900 ,  902  that is equipped for wireless communication. An adhesive pad  14 , which is welded only to a bottom of the sensor lower housing  170  also has an adhesive layer on an opposite side of the adhesive pad  14  where the adhesive layer coincides with the bottom of proximal external body flange portion  27  of applicator housing  21  for adhesively attaching the applicator module  15  to the skin of a patient. This is shown in  FIG. 1B . 
       FIG. 66  shows one embodiment of system  1000  in use after insertion of sensor  250  into the subcutaneous tissue. As shown,  FIG. 66  shows examples of electronic device  902 ,  902 ′, a transmitter  1004  (which is sensor module  160  containing sensor lower housing  170 , sensor upper housing  200  and electro-sensor assembly  220 ) on the patient&#39;s arm, where transmitter  1004  communicates analyte measurement data from continuous monitoring sensor  250  (deployed subcutaneously into the patient) to electronic device  902 , where the data is displayed to the user on a user interface  918 . 
     System  1000  also includes system software installed on an electronic device  902  equipped for wireless communication with transmitter  1004 . Optionally, system  1000  utilizes an analyte strip reader  906  (not shown) for calibration that is capable of wireless communication with electronic device  902 . Although a smartphone with software is illustrated, it is understood that the electronic device could be a dedicated reader/meter that is the size of a smartphone or it could be an integrated meter that includes a dedicated continuous glucose monitoring meter integrated with a blood glucose meter for calibration. Examples of electronic device  902  include a computer, a tablet computer, a smartphone, a data logger, a watch, an automobile information/entertainment system, or other electronic device. Wireless communication may be via radio frequency (RF) communication, Wi-Fi, BlueTooth, near-field communication (NFC), a sensor radio, mobile body area networks (MBAN) or other wireless communication protocol. In the embodiment employing a strip reader  906 , strip reader  906  has integrated BLE (BlueTooth low energy) and will send calibration data wirelessly to electronic device  902  and query the patient regarding the patient&#39;s intention to use the new calibration data point. 
     In one embodiment, transmitter  1004  communicates to the electronic device  902  using a wireless personal area network (WPAN), such as Bluetooth Low Energy (BLE). In other embodiments, other wireless communication protocols may be used with communication generally effective within a range of a few centimeters to a few meters. In some embodiments, for example, the system software is configured to communicate with Android and/or Apple software platforms installed on mobile phones and the like and has a range of up to thirty feet (about 9.2 meters). 
     In one embodiment, transmitter  1004  is designed to conserve power and operates via standard Bluetooth BLE protocol. For example, sensor readings from continuous monitoring sensor  250  are transmitted from transmitter  1004  every five minutes and the sensor reading is promptly displayed to the user after being received by the user&#39;s electronic device  902 . Typically, transmitter  1004  will successfully connect with the electronic device  902  after one or two attempts. 
     In one embodiment, system  1000  uses universally unique identifier (UUID) filtering to prevent unwanted communication from another device. It is expected that multiple devices may be present and discoverable in proximity to electronic device  902 , particularly when the user is in a densely populated area as in a subway, concerts, or other public locations. 
     In one embodiment, system  1000  utilizes calibration data obtained wirelessly from a separate strip reader. For example, a finger strip reading for glucose is taken and then either manually or automatically entered in system  1000  for calibration. In one embodiment, the system  1000  software application has a means for the user to manually enter a one-point calibration value taken from any meter. For example, the user uses the interface of the electronic device  902  to enter a calibration reading of 100 mg/dl obtained using a separate strip reader. After entering the calibration data, the user can accept, reject, or manually re-enter the calibration data. In other embodiments, the system software receives BLE calibration information from the external meter. After system  1000  receives the calibration data, the user can accept, reject, or manually re-enter this calibration data into the user interface. 
     The system software provides a user interface  918 , one example of which is a touch-sensitive display screen. In one embodiment, user interface  918  has a main screen  909  with indicators  910   a  for radio strength and battery strength. Another indicator  910   b  displays the analyte concentration (e.g., glucose concentration) in units of mg/dL (milligrams per deciliter) or mmol/L (millimoles per liter). Indicator  910   c  displays a glucose trending arrow to communicate to the user whether the analyte concentration (e.g., glucose) is increasing, decreasing, or unchanged. In one embodiment, indicator  910   c  for the trending arrow also communicates the relative rate of change. 
     In one embodiment, for example, a rate of change having an absolute value equal to or greater than a predefined value (e.g., 3 mg/dL/minute) is displayed as two vertically-oriented arrows (up or down); a rate of change in a second predefined range with an absolute value less than the predefined value (e.g., 2-3 mg/dL/minute is displayed as a single vertically-oriented arrow (up or down); a rate of change in a third predefined range with absolute value less than the second predefined range (e.g., 1-2 mg/dL/minute is displayed as an arrow inclined at 45° to the horizontal (up or down); and a rate of change in a fourth predefined range with an absolute value less than the absolute value of the third predefined range (e.g., 1 mg/dL/minute or less) is displayed as a horizontal arrow to indicate a steady state. In one embodiment, the rate of change is calculated based on five consecutive data points using the following formula: 
     
       
         
           
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     In one embodiment, analyte (e.g., glucose) concentration is updated every one minutes with data from transmitter  1004  and displayed on main screen  909 . Optionally, transmitted data is updated and stored in transmitter  1004  in case electronic device  902  is out of range or unable to receive during that period. In one embodiment, each transmission by transmitter  1004  includes a predefined number of previous data points (e.g., five) to fill in missing data in the event electronic device  902  is unable to receive during that period. 
     Main screen  909  also displays a plot  911  of analyte concentration versus time. In one embodiment, the Y-axis (analyte concentration) is configured to automatically scale with a minimum Y-axis value 10% below the minimum value of plotted data and the maximum Y-axis value 10% above the maximum value of plotted data. The X axis may be configured to display a timeframe of the user&#39;s choosing. 
     Main screen  909  also displays a macro timescale  912  of data that includes data displayed in plot  911 . Part of the data displayed in macro timescale  912  is highlighted and corresponds to the data displayed in plot  911 . For example, macro timescale  912  may be configured to display analyte concentration data over three hours, six hours, twelve hours, twenty-four hours, three days, or one week. Accordingly, data displayed in plot  911  is a subset of data displayed in macro timescale  912 . In one embodiment, highlighted area  913  of macro timescale  912  is an active element on user interface  908 . For example, by touching highlighted area  913  in the center and dragging left or right, the data of plot  911  is selected and moved. Similarly, by touching highlighted area  913  on left edge  913   a  or right edge  913   b  and dragging left or right, highlighted area  913  is expanded or contracted along the time axis. When the size or location of highlighted area  913  is adjusted, plot  911  is automatically updated to display data between the same minimum time and maximum time of highlighted area  913 . Main screen  909  also displays an active service icon  915 . Selecting active service icon  915  displays a service screen with indicators  910  for calibration and customization. For example, the service screen includes indicators  910  for setting upper and lower ranges, alarm limits, displayed units, device pairing settings, time scale, X-axis time domain, and the like. For example, the user accesses the service screen to set the time range of data displayed in macro timescale  912  and plot  911 . Selecting the calibration icon opens a calibration screen used to calibrate analyte data. In some embodiments, the service screen includes instructions for use or a link to access instructions for use. 
     For example, user-set or default values for maximum and minimum concentration/control limits are displayed on plot  911  as dashed lines  916   a,    916   b,  respectively, extending horizontally. In one embodiment, user-set control limits are not alarmed. Default control limits provide upper and lower alert limits and upper and lower reportable range limits. A reading above the maximum  916   a  or below the minimum  916   b  results in an alarm, such as vibration or an audible alert to the user. In one embodiment, maximum concentration limit  916   a  has a default value of 510 mg/dL and minimum concentration limit  916   b  has a default value of 90 mg/dL. 
     In some embodiments, system software is configured to generate reports for health care professionals. For example, touching an icon opens reports and configurations that could be transferred to a Health Care Professional via the cloud, such as the amount of time above and below target ranges; alarm reports, CGM values; estimated A1C and eAG values, and analyte measurements over time. 
     In one embodiment, system  1000  enables the user to manually enter a one-point calibration value taken from a separate glucose strip reader. For example, the user enters 100 mg/dl as obtained from a test strip measurement. After entering calibration data, the patient shall accept, reject, or manually re-enter this calibration data into the user interface. 
     In another embodiment, system  1000  is configured to receive calibration information from strip reader via BLE or other wireless communication protocol. 
     In some embodiments, settings and preferences may be locked and are accessed only by entering a password, biometric information, or other information serving as a key to unlock the settings and preferences menu. 
     In one embodiment, system  1000  performs general data calculations using the following generic variable labels: 
         A 0=( M*X+B )−( N*Y+C )
 
         A 1= A 0+calibration adjustment 
         A 2= A 1/18.018018 
         X= ((&lt;channel 0&gt;*0.000494)−1)*1000
 
         Y= ((&lt;channel 1&gt;*0.000494)−1)*1000
 
     Generic variables are defined as follows:
         A0 is uncalibrated CGM value in mg/dL   A1 is calibrated displayed CGM value in mg/dL   A2 is calibrated displayed CGM value in mmol/L (alternate units)   X is the mV reading output of Channel 0 (the sensor signal channel)   M is the slope correction factor Channel 0   B is offset correction factor for Channel 0   Y is the my reading output of Channel 1 (the blank signal channel)   N is the slope correction factor for channel 1   C is the offset correction factor for channel 1       

     In one embodiment, values for M, B, N, and C variables are stored on electronic device  902 . In one embodiment, values A0, A1, X, and Y are stored to a Sqlite Database along with date timestamp. For example, datetime, channel-0-value, channel-1-value, calculated-glucose value, calculated-glucose-value-with-calibration, and device-id. Optionally, a separate database includes patient-entered calibration data with timestamp, such as datetime, entered-calibration value, and device-id. 
     In one embodiment, values for A1 or A2 (values displayed to the patient in plot  911 ) that are greater than a predefined maximum limit (e.g., 500 mg/dL or 27.7 mmol/L) result in an error message displayed on user interface  918 , such as “Above Reportable Range.” Similarly, values for A1 or A2 of less than a predefined minimum limit (e.g., 40 gm/dL or 2.2 mmol/L) result in an error message displayed to the user, such as “Below Reportable Range.” 
     Communication between transmitter  1004  and electronic device  902  is secure. For example, BLE-supported Security Manager Protocol is utilized between transmitter  1004  and electronic device  902 . SMP defines the procedures and behavior to manage pairing, authentication, and encryption between the devices, including encryption and authentication, pairing and bonding, key generation for device identity resolution, data signing, encryption, pairing method based on the input/output capabilities of transmitter  1004  and electronic device  902 . 
     In one embodiment, electronic device  902  is a watch configured to communicate wirelessly with transmitter  1004 . In such an embodiment, system software includes three screens on the user interface  918  of the electronic device  902 ′ configured as a watch. A first screen displays the most recent analyte concentration and units of measurement. For example, glucose concentration is displayed by indicator  910   b  in mg/dL or mmol/L and is updated every five minutes. A trending arrow indicator  910   c  shows the relative rate of change as discussed above. 
     A second screen displays the most recent glucose concentration and units of measurement. Second screen displays plot  911  with analyte concentration data for the previous one hour, where the Y-axis is glucose concentration and the X-axis is time. Upper and lower limits  916   a,    916   b  are displayed in dashed lines. A third screen displays macro timescale  912  with twenty-four hours of acquired data. 
     Sensor Construction 
       FIG. 67  shows a perspective illustration of one embodiment of a multi-layer sensor assembly  500  ready for deposition of reagents to create a continuous monitoring sensor  250  having, in this embodiment, a reference electrode  534 , a blank or second working electrode  533 , a counter electrode  532 , and a first working electrode  530 . Electrodes  530 ,  532 ,  533 ,  534  are formed at a substrate distal end portion  502  and communicate electrically through assembly middle portion  530  with electrically-conductive contact pads  503  at a substrate proximal end portion  501 . Multi-layer sensor substrate  500  is useful to form a subcutaneous analyte sensor, such as a glucose monitoring sensor. 
     A sensing layer (not shown) is formed over each of the first and second working electrodes  530 ,  533 . The sensing layer is made up of three coating layers, a base coating layer, a second coating layer and a third or top coating layer. The base coating layer contains poly-2-hydroxyethyl methacrylate (PHEMA) and is the coating that is disposed directly on the exposed metal at the bottom of the respective wells at substrate distal end portion  502 . Specific to the first working electrode where glucose is measured, glucose oxidase and/or glucose dehydrogenase is also included. The second working or blank electrode does not contain any enzyme and is used only for measuring background noise and/or interferents in the sample since the first working electrode will have a total current that include a portion driven by the amount of glucose in the subcutaneous tissue as well as the background noise and/or interefents derived current. Using an algorithm to subtract the current derived from the second working or blank electrode from the first working electrode provides a more accurate glucose measurement. The second coating layer is disposed directly on the base coating layer and contains PHEMA and a plurality of microspheres from polydimethylsiloxane (PDMS). PDMS is a material a material having substantially no or little permeability to glucose but a substantially high permeability to oxygen. The third or top coating layer is disposed directly on the second coating layer and contains PHEMA and catalase. Catalase is a material that prevents release of hydrogen peroxide from the sensing layer into the surrounding environment. In this case, the surrounding subcutaneous tissue. For the reference electrode  534 , a silver-silver chloride (AgCI) layer is created on the metal at the bottom of the well and then the AgCI layer is covered with a hydrogel membrane. The counter electrode  532  has the metal at the bottom of the well covered only with a hydrogel membrane. 
     Referring now to  FIG. 68 , a perspective, exploded illustration shows a base layer  510 , a middle layer  550 , and a top layer  580  that together comprise multi-layer sensor substrate  500 . “Middle layer” herein means the layer adjacent to the top layer  580  without any intervening, electrically-insulating layer when there are other layers between base layer  510  and middle layer  550 . Base layer  510  is electrically insulating and includes a base proximal end portion  514 , a base distal end portion  516 , and a base middle portion  518  between base proximal end portion  514  and base distal end portion  516 . A base metallized layer  520  is disposed on base layer  510  and defines at least one circuit  552  extending longitudinally along base layer  510 . Each circuit  552  has an electrically-conductive contact pad  524  formed at base proximal end portion and an electrically-conductive contact pad  526  formed at base distal end portion  516  with an electrically-conductive trace  528  electrically coupling electrically-conductive contact pad  524  at the base proximal end  514  with electrically-conductive pad  526  at base distal end  516 . 
     Middle layer  550 , also electrically insulating, is disposed over base layer  510  and includes a middle layer proximal end portion  554 , a middle layer distal end portion  556 , and a middle layer middle portion  558 . Middle layer  550  has a size and shape corresponding to base layer  520  and that is aligned with base layer  510 . Middle layer  550  includes electrically-conductive contact pads  560  at middle layer distal end portion  556  adapted to receive an electrode material or reagent to form a respective electrode. Each electrically-conductive contact pad  562  at middle layer proximal end portion  554  is adapted to receive an electrical contact. 
     The top layer  580 , also electrically-insulating, is disposed over middle layer  550 . Top layer  580  has a size and shape corresponding to middle layer  550  and base layer  510 . Top layer  580  has a top layer proximal end portion  582 , a top layer distal end portion  584 , and a top layer middle portion  586 , where top layer  580  aligned with base layer  510  and middle layer  550 . Top layer  580  has a plurality of openings that include contact openings  590  on substrate proximal end portion  501  and sensor wells  592  on substrate distal end portion  502 . Contact openings  590  and sensor wells  592  coincide with electrically-conductive contact pads  560 ,  562 , respectively, of middle layer  550 . Base layer  510 , middle layer  550 , and top layer  580  are manufactured with circuits  552 ,  572  on base layer  510  and middle layer  550  to create multi-layer sensor substrate  500  with substrate proximal end portion  501 , substrate distal end portion  502 , and assembly middle portion  503  extending longitudinally between substrate proximal end portion  501  and substrate distal end portion  502  as shown, for example, in  FIG. 42 . Substrate distal end portion  502  and assembly middle portion  503  each have a width of about  279  microns. 
     Referring now to  FIGS. 69-71 , base layer  510  is shown in a plan view in  FIG. 44 , base proximal end portion  514  is shown enlarged in  FIG. 70 , and base distal end portion  516  is shown enlarged in  FIG. 71 . Base layer  510  has a base layer substrate  512  that is electrically insulating and includes a base proximal end portion  514 , a base distal end portion  516 , and a base middle portion  518  extending between and connecting base proximal end portion  514  and base distal end portion  516 . In one embodiment, base layer substrate  512  is made of polyimide and has a thickness from 7.5 μm to 12.5 μm. For example, base layer substrate  512  has a thickness of about 10 μm. In one embodiment discussed in more detail below, base layer substrate  512  may be formed by spin coating polyimide on a glass plate followed by further lithographic processing. 
     Base metallized layer  520  is disposed directly onto base layer substrate  512  and defines at least one circuit extending longitudinally along base layer substrate  512  from base layer proximal end portion  514  to base layer distal end portion  516 . In one embodiment as shown, base metallized layer  520  defines two circuits  522 , where each circuit  522   a,    522   b  has an electrically-conductive contact pad  524   a,    524   b,  respectively, formed at base proximal end portion  514 . Circuit  522   a  has an electrically-conductive contact pad  526   a   1 - 526   a   2 , formed at base distal end portion  516 . Circuit  522   b  has electrically-conductive contact pad  526   b  at distal end portion  516 . Each circuit  522   a,    522   b  has an electrically-conductive trace  528  ( 528   a  and  528   b ) electrically coupling electrically-conductive contact pad  524   a   1 - 524   a   2 ,  524   b  at the base proximal end portion  514  with the respective electrically-conductive pad  526   a,    526   b  at the base distal end portion  516 . For example, circuit  522   a  is configured for a working electrode  530  of sensor assembly  500  and circuit  522   b  is configured for a blank electrode  533  of sensor assembly  500  (shown in  FIG. 67 ). 
     Contact pads  526   a   1 - 526   a   2  each have a size and shape corresponding to one or more contact pads  562  of middle metallized layer  550 , rather than being sized only for through openings  564  of middle layer substrate  552 . An advantage of this configuration is that contact pads  526   a   1 - 526   a   2  reduce stress induced to contact pads  562  caused by the spin coating process described below, which stress leads to cracking of contact pads  562  in middle metallized layer  570 . In one embodiment, for example, contact pad  526   a   1  is sized and shaped to substantially underlie contact pad  562   a  of middle metallized layer  570 , but not through opening  564   c.  Contact pad  526   a   2  is sized and shaped to substantially underlie contact pads  562   b,    562   c  and through opening  564   d  of middle metallized layer  570 . 
     In one embodiment, base metallized layer  520  has an overall thickness of 1200±300 Å. For example, base metallized layer  520  is formed by depositing a first part of chromium (200 35 150 Å) directly onto and against base layer substrate  512 , a second part of gold (1000±150 Å) disposed directly onto the chromium, and a third part of chromium (200±150 Å) disposed directly onto the gold. In other words, the base metallized layer  520  has a thickness in the range of about 900 Angstroms to about 1,500 Angstroms. Other conductive materials and thicknesses are acceptable for base metallized layer  520  depending on the intended use of sensor assembly  500 . 
     Referring now to  FIGS. 72-74 , middle layer  550  is shown in a plan view in  FIG. 72 , second proximal end portion  554  is shown enlarged in  FIG. 73 , and second distal end portion  556  is shown enlarged in  FIG. 74 . Middle layer  550  has a middle layer substrate  552  that is electrically insulating and defines a plurality of middle layer through openings  564  with side walls extending to base layer  510 , where each middle layer through opening  564  communicates electrically with a respective electrically-conductive contact pad  524 ,  526  of circuit  552  of base layer  510 . In one embodiment, middle layer substrate  552  is made of polyimide that is spin coated onto base layer  510  and base metallized layer  520  as discussed below, for example, in a method  600  of making multi-layer sensor substrate  500 . 
     In one embodiment, middle layer substrate  552  has a thickness from 7.5 μm to 12.5 μm, such as about 10 μm. 
     A middle metallized layer  570  is disposed directly onto middle layer substrate  552  and the side walls of through openings  564  to define at least two middle layer circuits  572 , where each middle layer circuit  572  has electrically-conductive contact pad  560  formed at middle layer proximal end portion  554  and electrically-conductive contact pad  562  formed at middle layer distal end portion  556  with an electrically-conductive trace  574  electrically coupling contact pad  560  at middle layer proximal end portion  554  with electrically-conductive contact pad  562  at middle layer distal end portion  556 , and a least one or more additional electrically conductive pads  560 ,  562  in electrical contact with through openings  564 . The at least one or more additional electrically conductive pads  560 ,  562  electrically coupled to base layer circuit(s)  552  by way of through openings or vias  564 . For example, middle metallized layer  570  is deposited on top surface  550   a,  on the sidewalls of through openings  564 , and onto part of base metallized layer  520  creating electrical continuity between the base metallized layer  520  and the respective contact pads  560 ,  562 . 
     In one embodiment of middle layer proximal end portion  554  as shown in  FIG. 73 , for example, middle layer circuit  572   a  includes contact pad  560   b  and middle layer circuit  572   b  includes contact pad  560   c.  Contact pads  560   a,    560   d  are isolated from middle layer circuits  572   a,    572   b.  Contact pad  560   a  (e.g., for working electrode  130 ) defines two through openings  564   a  and contact pad  560   b  (e.g., for blank electrode  133 ) defines two through openings  564   b,  each of which has electrical continuity to base metallized layer  520  at contact pad  524   a  and contact pad  524   b,  respectively (shown in  FIG. 70 ). 
     In one embodiment of middle layer distal end portion  556  as shown in  FIG. 74 , for example, middle layer circuit  572   a  includes contact pad  562   a  and middle layer circuit  572   b  includes contact pad  562   c.  Contact pads  562   b,    562   d  are isolated from middle layer circuits  572   a,    572   b.  Middle layer substrate  552  has through opening  564   c  at with contact pad  562   b  (e.g., for blank electrode  133 ) having electrical continuity to base metallized layer  520  at contact pad  526   b  (shown in  FIG. 71 ). Middle layer substrate  552  defines through opening  564   d  with contact pad  562   d  having electrical continuity with contact pad  526   a   2  (shown in  FIG. 71 ). Contact pads  562   d  and  562   b  are isolated from middle layer circuits  572   a,    572   b.  Contact pad  562   a  (i.e. the reference electrode  134 ) is segmented into 3 contact pad portions  562   a   1 ,  562   a   2  and  562   a   3 . The reference electrode  534  is segmented to prevent cracking of the Ag/AgCI and delamination from contact pad  562   a,  which is a definite advantage where sensor  500  is implanted subcutaneously in a patient. 
     An advantage of the multi-layer sensor assembly  500  is the ability to construct a sensor having a smaller width that penetrates the subcutaneous tissue than is achievable by laying all of the conductive traces side-by-side on a single substrate. The multi-layer sensor assembly  500  uses multiple layers for the traces thus reducing the width by limiting each layer to one or two circuit traces. 
     Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.