WO2019239258A1

WO2019239258A1 - Flexible ultra low profile transcutaneous continuous monitoring sensor

Info

Publication number: WO2019239258A1
Application number: PCT/IB2019/054697
Authority: WO
Inventors: Thomas A.J. MAYER, Jr.; Cameron M. YOUNG; Jennifer L. GASS; Eugene R. Prais
Original assignee: Ascensia Diabetes Care Holdings Ag
Priority date: 2018-06-12
Filing date: 2019-06-06
Publication date: 2019-12-19
Also published as: TW202000135A

Abstract

A flexible monitoring system for continuous monitoring of a fluid in a user is disclosed. The flexible monitoring system includes a transmitter support assembly and a sensor assembly. The transmitter support assembly includes a base substrate layer having a first surface for contact with the skin of the user. A circuit board layer is located on an opposite second surface of the base substrate layer. A cover layer is placed over the circuit board and the base substrate layer. The sensor assembly is supported by the transmitter support assembly and includes a sensor extending through the base substrate layer. The sensor is insertable in the skin when the first surface of the base is placed in contacts with the skin.

Description

FLEXIBLE ULTRA LOW PROFILE TRANSCUTANEOUS CONTINUOUS

MONITORING SENSOR

PRIORITY CLAIM

[0001] The present application claims priority to U.S. Provisional Patent Application No. 62/683,967 filed on June 12, 2018. The contents of that application are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates generally to a flexible sensor for analytes (e.g., blood glucose) and more specifically a flexible skin-mounted continuous blood glucose monitor.

BACKGROUND

[0003] The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological conditions. For example, persons with diabetes (PWDs) frequently check the glucose level in their bodily fluids. The results of such tests can be used to regulate the glucose intake in their diets and/or to determine whether insulin or other medication needs to be administered. A PWD typically uses a measurement device (e.g., a blood glucose meter) that calculates the glucose concentration in a fluid sample from the PWD, where the fluid sample is collected on a test sensor that is received by the measurement device. The failure to take corrective action may have serious medical implications for that person.

[0004] One method of monitoring the blood glucose level of a PWD is with a portable testing device. The portable nature of these devices enables users to conveniently test their blood glucose levels at different locations. One type of device utilizes an electrochemical test sensor to analyze the blood sample. A user employs a lancet to obtain a blood sample for the test sensor. The electrochemical test sensor typically includes electrodes that, when mated with the meter, electrically measures the reaction of the blood sample to determine an analyte concentration. A special meter device must therefore be carried by the user to determine the blood sample analysis.

[0005] Traditional test sensors and meters suffer from the reliance on the PWD to perform the testing. Further, since such testing is performed only periodically, sudden changes in glucose levels cannot be detected immediately. In order to provide continuous monitoring, a number of solutions have been proposed for a continuous glucose monitor. Such sensors currently are implanted in a patient and thus are cumbersome. Further, such devices are not easily replaced. Other continuous sensors have been designed for attachment to a patient’s skin. Current skin-mounted sensors either have a hard disk, or have a rigid baseplate and modular transmitter.

[0006] Such current body sensors for continuous glucose monitoring thus suffer from lacking one or more of the following: they do not ensure that they can be worn comfortably under clothing; they do not have a low profile and avoid impact; they do not present a soft flexible feel and appearance; they do not contour and move with the dynamics of tissue flex, expansion and contraction; they do not protect the sensor site and internal hardware from fluid ingress and other use hazards; or they do not provide breathability/ air flow at skin adhesive area.

[0007] Thus, there exists a need for a skin-mounted continuous glucose monitoring system that may be comfortably worn on the skin. There is also another need for a continuous glucose monitoring system that has sufficient flexibility to move with the dynamics of tissue flex, expansion and contraction. There is also a need for a skin-mounted continuous glucose monitoring system that is low profile but provides long operating life.

SUMMARY

[0008] According to one example, a flexible sensor system for continuous monitoring of a user is disclosed. The sensor system includes a base substrate layer configured for contacting the skin of the user. A circuit board layer is located adjacent the base substrate layer. A sensor extends through the base substrate layer. The sensor is insertable in the skin. A cover layer encases the circuit board layer.

[0009] Another example is a support assembly for a skin attached, continuous monitoring system. The support assembly includes a base substrate layer having a surface for adherence to the skin. A circuit board layer is located over an opposite surface of the base substrate layer. A cover layer encapsulates the flexible circuit board layer. An aperture is formed by the base substrate layer and cover layer for holding a sensor introducer module.

[0010] Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 A is a side cutaway view of a flexible continuous monitoring system having a sensor assembly and a transmitter support assembly manufactured with a layering process according to one embodiment;

[0012] FIG. 1B is a side cutaway view of the transmitter support assembly of the sensor system in FIG. 1A;

[0013] FIG. 2A is a side cutaway view of the sensor assembly in FIG. 1 A;

[0014] FIG. 2B is a perspective view of the sensor assembly in FIG. 1 A;

[0015] FIG. 3A is a side cutaway view of a flexible continuous monitoring sensor system with a transmitter support assembly manufactured with a potted manufacturing process according to another embodiment;

[0016] FIG. 3B is an opposite side cutaway view of the sensor system shown in FIG. 3 A;

[0017] FIG. 3C is a top perspective cutaway view of the sensor system shown in FIG.

3 A;

[0018] FIG. 3D is a side cutaway view of the transmitter support assembly shown in FIG. 3 A;

[0019] FIG. 3E is a bottom view of an alternate potted transmitter support assembly;

[0020] FIG. 3F is a side cutaway view of another alternate transmitter support assembly with a separate base assembly;

[0021] FIG. 4A shows a first step in the process of attaching the sensor system shown in FIGs. 3 A-3C to the skin of a patient;

[0022] FIG. 4B shows a second step in the process of attaching the sensor system shown in FIGs. 3A-3C to the skin of a patient;

[0023] FIG. 4C shows a third step in the process of attaching the sensor system shown in FIGs. 3 A-3C to the skin of a patient;

[0024] FIG. 4D shows a fourth step in the process of attaching the sensor system shown in FIGs. 3A-3C to the skin of a patient;

[0025] FIG. 5A is a block diagram of the transmitter module of the sensor system in FIGs. 3A-3C;

[0026] FIG. 5B is a block diagram of the transmitter of the transmitter module in FIG. 5A;

[0027] FIG. 6A is a perspective view of a first different shape of a transmitter support assemblies that is skin-mounted and can support the sensor module in FIG. 2A-2B; [0028] FIG. 6B is a perspective view of a second different shape of a transmitter support assemblies that is skin-mounted and can support the sensor module in FIG. 2A-2B;

[0029] FIG. 6C is a perspective view of a third different shape of a transmitter support assemblies that is skin-mounted and can support the sensor module in FIG. 2A-2B;

[0030] FIG. 6D is a perspective view of a fourth different shape of a transmitter support assemblies that is skin-mounted and can support the sensor module in FIG. 2A-2B;

[0031] FIG. 6E is a perspective view of a fifth different shape of a transmitter support assemblies that is skin-mounted and can support the sensor module in FIG. 2A-2B;

[0032] FIG. 7A is a perspective view of an example flexible support mesh for the transmitter support assemblies in FIGs. 1B and 2C according to one embodiment;

[0033] FIG. 7B is a perspective view of another example flexible support mesh for the transmitter support assemblies in FIGs. 1B and 2C according to another embodiment;

[0034] FIG. 8 is a perspective view of a three-lobe shaped transmitter support assembly for a sensor system that allows greater battery storage;

[0035] FIG. 9A is a side cutaway view of an integrated transmitter support assembly and sensor according to one embodiment;

[0036] FIG. 9B is a side cutaway view of an insertable sensor and another example of a transmitter support assembly according to another embodiment; and

[0037] FIG. 9C is a side cutaway view of the assembled sensor and the transmitter support assembly in FIG. 9B.

[0038] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

[0039] FIG. 1A shows a flexible and ultra-low profile continuous glucose monitoring system 100 according to one embodiment. As will be explained, the monitoring system 100 in FIG. 1A is one example of a skin based continuous analyte monitoring system. The principles described below may be incorporated in a number of different ways including various construction methods and design elements. The system 100 includes a sterile module 102 and a transmitter support assembly 104. The sterile module 102 includes a protective cover for a sensor that is inserted in the skin as will be explained below. In this example, the transmitter support assembly 104 is constructed using a layer type of construction. A potted type of transmitter support assembly may also be used as will be explained below in reference to FIGs. 3A-3B.

[0040] Each of the two types of construction methods (layered and potted) may be employed to create transmitter assemblies of various shapes such as circular, rectangular/strip, oval, three lobed, or four lobed. Additionally, the transmitter support assembly may include a flexible support mesh to assist in the stability of the structure.

[0041] FIG. 1B is a side view of the transmitter support assembly 104 of the flexible monitoring assembly 100 that may be attached to the skin of a patient. FIG. 1B shows the removal of the protective cover and an insertion member, leaving a sensor 150 ready for insertion in the skin. As explained above, the transmitter support assembly 104 in FIG. 1B is constructed using the layered method of construction. The transmitter support assembly 104 includes a skin adhesive base substrate layer 110, a base layer 112, a flexible circuit board layer 114, a foam layer 116 and a top cover layer 118. A donut member 120 is mounted in an aperture 122 formed by the layers 110, 112, 114, 116 and 118. As shown in FIG. 1A, the donut member 120 holds the sterile module 102. In this example, the base substrate layer 110 is a non-woven fabric like material such as the 3M 1776 single sided polyester non-woven medical tape.

[0042] The skin adhesive substrate layer 110 has a bottom base surface that is coated with a skin adhesive 130 and an opposite top surface that is coated with a base adhesive 132 that joins the skin adhesive base substrate layer 110 with the bottom surface of the base layer 112. The opposite top surface of the base layer 112 includes a flex circuit adhesive 134 that joins the flexible circuit board layer 114 with the base layer 112. Thus, in order from the top to the bottom of the transmitter assembly 104 in FIG. 1B is as follows. The donut 120 will adhere to the top cover layer 118 and the base layer 112. The top cover and base layers 118 and 112 will also adhere to each other at opposing ends. The base layer 112 will adhere to the skin adhesive substrate 110. The skin adhesive substrate 110 contains the skin adhesive that will adhere to the skin of the patient when the glucose monitoring system 100 is attached to the patient.

[0043] The flexible circuit board layer 114 supports electronic components, such as an analog front end circuit, a transmitter module 140 and a battery 142. The flexible circuit board layer 114 may be fabricated from materials such copper, kapton, polyester (PET), polyethylene naphthalate (PEN), polymides, fiberglass and acrylic adhesives. The flexible circuit board layer 114 includes electronic components in the form of a printed circuit and electronic components. The printed circuit serves to connect all electrical and transmitter components, the battery 142, and the sensor 150 inserted through the sensor assembly 102. As will be explained below, the transmitter module 140 operates the measurement and analysis functions and may include an internal memory for sensed data as well as an internal transmitter.

[0044] In this example, the battery 142 is a thin, flexible battery and powers the electronic components on the flexible circuit board layer 114. Other types of batteries may be used such as a small coin cell battery that conforms to the dimensions of the transmitter support assembly 104. Example coin cell batteries may be Lithium Manganese, Silver Oxide, and Alkaline coin batteries such as CR 2032, SR516, and LR60 type coin batteries, respectively It is desirable to minimize the height of the battery 142 to allow for a low overall height of the transmitter support assembly 104. In this manner, once the system 100 is attached to the skin, it is unobtrusive. The battery 142 is envisioned to be of various shapes and sizes to accommodate various transmitter shapes. In addition, multiple batteries may be connected together to constitute a single power unit to provide flexibility for the overall sensor system.

[0045] The sensor 150 is assembled with the flexible printed circuit formed on the flexible circuit board layer 114 and will remain assembled throughout its useful life. The sensor 150 includes a support member 152 and a sensor member 154 that will be inserted through the skin of the user as will be explained below.

[0046] In this example, the sensor member 154 is designed for insertion subcutaneously. The sensor member 154 therefore will be in contact with, for example, interstitial fluid when the sensor member 154 is inserted in the user. The sensor 150 in this example is a glucose sensor having a series of electrodes on the sensor member 154 that are coated with an enzyme that reacts with glucose in the interstitial fluid. An electrical input signal is applied to the electrodes on the sensor 150 to provide an output signal that is indicative of the analyte concentration in the interstitial fluid.

[0047] Examples of the types of analytes that may be collected include glucose, lipid profiles (e.g., cholesterol, triglycerides, LDL and HDL), microalbumin, hemoglobin Ale, fructose, lactate, or bilirubin. It is contemplated that other analyte concentrations may also be determined. It is also contemplated that more than one analyte may be determined. The analytes may be in, for example, a whole blood sample, a blood serum sample, a blood plasma sample, other body fluids like urine, and non-body fluids. As used within this application, the term “concentration” refers to an analyte concentration, activity (e.g., enzymes and electrolytes), titers (e.g., antibodies), or any other measure concentration used to measure the desired analyte.

[0048] The sensor 150 may be made from one or more sheets, including a substrate layer such as a vinyl polymer with subsequent layers of gold, silver, silver chloride, polyimide, and/or various coatings and enzymes suitable for the sensor’s use in determining blood glucose levels. Other sensor materials may be used.

[0049] As explained above, the sensor 150 is inserted under the skin and provides an output signal to the components on the flexible circuit board layer 114 in response to an input signal. The output signal is indicative of the blood glucose level of the user. These measurements may be made automatically many times throughout the day (e.g., every 10 seconds, 30 seconds, 1 minutes, 5 minutes or at some other interval).

[0050] The flexible transmitter assembly may be attached to the skin and the sensor 150 may be inserted under the skin using previously disclosed inserter approaches. One particular accommodation would be that the transmitter support assembly 104 that carries the transmitter (e.g., transmitter module 140) potentially consists of a softer, conformable layer such as the foam layer 116. The body of the transmitter is fixed in some way to the transmitter support assembly that drives the transmitter towards the surface of the skin. The needle/introducer in the sterile module 102 is also driven into the skin by the inserter as will be explained below. The soft conformable layer is placed between the transmitter support assembly and the transmitter component. Similar to a cushion, this layer protects the surface of the transmitter component from direct pressure of the transmitter support assembly 104 pressing down on the transmitter.

[0051] The layered method of construction employs layers of thin films of varying materials that are adhered together to create the transmitter support assembly 104. The top cover layer 118 serves to encase the flexible circuit board layer 114, the transmitter module 140, and the battery 142. The top cover layer 118 protects the electronic components on the flexible circuit board layer 114 against liquid and dust ingress. The foam layer 116 is located on the inside surface of the top layer 118 to provide additional insulation against compressive forces against the top cover layer 118. The top cover layer 118 is preferably constructed of a soft and flexible material, such as thermoplastic polyurethane (TPU), that is comfortable to the user. The foam layer 116 is constructed of TPU foam in this example. The layered construction method relies upon a lamination method or a type of sealing process to adhere each layer to the others. Such methods may include adhesives, RF/ultrasonic welding, or heat sealing.

[0052] FIG. 2A is a side cutaway view and FIG. 2B is a perspective view of the sterile module 102 in FIG. 1A. The sterile module 102 includes the donut member 120 and the sensor 150. The sterile module 102 is a sub-assembly that contains a sensor holder 210, an introducer 212, an introducer cover 214, and a capsule shaped central body 216 to contain the aforementioned components. The sterile module 200 undergoes a sterilization process prior to the assembly with the transmitter support assembly. For example, all components within the sterile module 200, such as the sensor 150, the sensor holder 210, and the introducer 212, may be sterilized (e.g., using an electron beam, a gamma beam, or the like). The sterile module 200 is thus designed such that the sensor 150 and the introducer 212 maintain their sterility, but prevents the electronic components in the transmitter support assembly from being damaged in the sterilization process.

[0053] In this example, the sensor holder 210 extends from the bottom of the introducer cover 214 and supports the sensor member 154 over its length. The introducer 212 is at the end of the sensor holder 210 and may have a blade shape to assist in penetrating the skin. The introducer cover 214 includes a handle 218 extending from the top of the introducer cover 214. As will be explained below, when the sensor system is applied, the capsule shaped central body 216 is removed to expose the sensor holder 210, the introducer 212, and the sensor member 154. The sensor holder 210 and introducer 212 is inserted in the skin of the patient. The introducer cover 214 is then pulled out with the attached sensor holder 210 and introducer 212, and discarded, leaving the sensor member 154 inserted in the skin of the patient.

[0054] In this example, the introducer cover 214 and central body 216 may be made from acrylonitrile butadiene styrene (ABS), polycarbonate, nylon, acetal, polyphthalamide (PPA), polysulfone, polyethersulfone, polyetheretherketone (peek), polypropylene, highdensity polyethylene (HDPE), low density polyethelene (LDPE) or a similar material. Other materials may be used.

[0055] In this example, the sensor holder 210 and introducer 212 may be made from a metal such as stainless steel or from another suitable material such as rigid plastic. In some embodiments, the sensor holder 210 and the introducer 212 may be, but are not limited to, a round C-channel tube, a round EG-channel tube, a stamped sheet metal part folded into a square Eί-profile, a molded/cast metal part with a square U-channel profile, or a solid metal cylinder with an etched or ground square EG-channel. The sensor holder 210 and the introducer 212 may be implemented as stamped sheet metal folded into a square U-profile, the inner width and height may be in a range from about 400pm to about 700pm, with a wall thickness in a range from about lOOpm to about 250pm. The sensor holder 210 and introducer 212 may be implemented as a molded or cast metal part. Other introducer and/or cover configurations, sizes and/or materials may be used.

[0056] As described above, the donut member 120 is a small cylindrical tube with a top surface to interface with the base of the introducer cover 214 from where the sensor support 210 extends. As shown in FIG. 2 A, the sensor support 210 and the introducer 212 extend through the body of the donut member 120. The donut member 120 serves several important functions. First, the donut member 120 serves as the carrier of the sterile module 200 and receives the sterile module 200 during the assembly process of joining the sterile module 102 to the transmitter support assembly 104. The donut member 120 also serves as a molding shutoff surface (both top and bottom) in the potted assembly process explained below is used or a fixturing surface if a layered construction process is chosen. Finally, the donut member 120 helps to keep the flexible circuit board layer 114, and an optional flexible support mesh in place as these components are assembled around the main axis of the donut member 120. Alternatively, the donut member 120 may include a mesh skirt as part of a one piece molding. It is to be understood that other similar support members may be used for the donut member 120 depending on the shape of the aperture and the shape of the inserted sensor. For example, a similar support member may be a square shape, an oval shape, a triangular shape and may have a center aperture having different shapes.

[0057] FIG. 2B shows the connection between the sterile module 200 and a contact tab 220 that is connected to the flexible circuit board layer 114. The contact tab 220 is preferably fabricated as part of the sensor 150 and is preferably the same insulator material. The electrodes of the sensor 150 are connected to corresponding electrical traces on the contact tab 220. The contact tab 220 is connected to the flexible circuit board layer 114 and is assembled with the battery 142, the sensor 150, and the donut member 120. The flexible circuit may have regions where a thin stiffener plate is used for protection of components and connection. For example, a stiffener plate may be provided to support integrated circuits such as the microprocessor.

[0058] FIG. 3A shows a side view of a flexible continuous monitoring system 300 according to another embodiment. The flexible continuous monitoring system 300 includes the sterile module 102 in FIG. 2A-2B and a transmitter support assembly 310. In this example, the transmitter support assembly 310 is formed by a potted assembly method and supports the donut member 120 of the sterile module 102. FIG. 3B shows the opposite side view of the flexible continuous monitoring system 300. FIG. 3C shows a top perspective cutaway view of the potted support structure 310 and installed sterile module 102. FIG. 3D shows a side cutaway view of the potted transmitter support assembly 310 in FIG. 3 A.

[0059] The potted transmitter support assembly 310 includes a base substrate layer 320, a potted cover layer 322, the donut member 120, and a flexible circuit board layer 324. In this example, the base substrate layer 320 is a non-woven fabric like material such as the 3M 1776 single sided polyester non-woven medical tape. In this example, the potted cover layer 322 may be an elastic material such as liquid silicone rubber (LSR) or thermoplastic elastomer (TPE), urethane, silicone rubber, or a like material. The base substrate layer 320 may be fabricated from materials such as polyurethane, polyolefin, and polyester. These and other flexible materials would be used in thin sheets/films. The cover layer 322 has a flat bottom surface that is attached to the top surface of the base substrate layer 320 via an adhesive 330. The cover layer 322 has a generally dome shaped outer surface 326. The cover layer 322 includes a center aperture 328 that holds the donut member 120. As with the layered support structure 110 in FIGs. 1A-1B, the donut 120 supports the sensor 150 for insertion under the skin of the patient.

[0060] The cover layer 322 encases and protects electronic components mounted on the flexible circuit board layer 324. One set of such components includes a transmitter module 340, a battery 342 and a contact interface 344. The contact interface 344 is connected to the contact tab 220 of the sensor 150. In this example the transmitter module 340 includes a processor, an internal memory, an internal transmitter, and an internal antenna. One non limiting example of a transmitter may be a Bluetooth Low Energy (BLE) transmitter. One non limiting example of a suitable microprocessor with internal components is a MBN52832 BLE transmitter module, manufactured by Murata, having a Nordic BLE chip and an ARM Cortex processor. Of course other types of transmitters may be used including NFC or RF transmitters. The shape and overall area of the transmitter assembly can vary considerably and can be optimized to promote a better user experience. Further, the circuit components, such as the memory and the transmitter, may be separate components from the microprocessor. The overall thickness of the transmitter support assembly is less than about 2.5mm and preferably less than 2mm. However, different dimensioned transmitter support assemblies may be used. The battery 342 is attached to the flexible circuit board layer 324 via a battery adhesive 346. [0061] As explained above, the top surface of the base substrate layer 320 is attached to the flat bottom surface of the cover 322 via the adhesive 330. The opposite bottom surface is coated with a skin adhesive 350 that adheres the assembly 300 to the skin surface of a user.

[0062] The potted method employs the use of a potting material for the cover layer 322, such as liquid silicone rubber (LSR), thermoplastic elastomer (TPE), Urethane, or Thermoplastic Urethane (TPU) to completely encapsulate all components to protect against liquid and dust ingress, while still maintaining flexibility of the transmitter support assembly 310. The potted construction method requires tooling in which LSR can be injected into a cavity containing the donut 120, flexible circuit board layer 324, electrical components, and the battery. The sterile module 200 in FIGs. 2A-2B may also be assembled when molding the cover layer 322. The mold may include features that result in specific surface patterns on the finished cover layer 322.

[0063] The potted silicone or other material could be overlaid with a thin skin-like material or applied coating to improve natural feel to the touch. Alternatively, the potted material could be textured to provide a more natural feel.

[0064] Although this example has a two-piece construction of the base substrate layer 320 and the cover layer 322, a single piece cover may be molded around the flexible circuit board layer 324. In such a construction, the cover layer would also have a flat bottom surface for holding the skin adhesive and therefore omit the base substrate layer 320. In such a construction, the potted material may also include contours to assist in flexibility when the transmitter support assembly is attached to the skin surface. FIG. 3E shows the bottom view of a potted one-piece cover layer 350. The cover layer 350 includes a center aperture 352 for holding the donut 120 and sterile module 102 in FIG. 2A-2B. The cover layer 350 has a largely flat bottom 354. A series of contours 360 are formed between the center aperture 352 and the edges of the cover layer 350. The contours 360 provide additional flexibility for the cover layer 350. The contours 360 also improve the breathability of the cover layer 350 by acting as a path for sweat and other bodily fluids to drain and exit the area of the sensor. It is to be understood that the contours may also be used for the base substrate layer 320 in FIGs. 3A-3D or the skin substrate layer 110 in FIG. 1 A.

[0065] FIG. 3F shows a cross section view of an alternative transmitter support assembly 370. Like components of the transmitter assembly 370 identical to components in relation to the transmitter assembly 310 in FIG. 3D are labeled with identical numerical references. The transmitter support assembly 370 includes a separate base support layer 380. The base support layer 380 has a surface that supports the flexible circuit board 324. The opposite surface of the separate base support layer 380 is attached to the skin adhesive substrate 320 via the adhesive 330. In this example, the base support layer 380 may be fabricated from materials such as silicone, urethane, TPE, or TPU.

[0066] FIGs. 4A-4D show the application process of the sensor systems described above such as the sensor system 300 in FIGs. 3A-3D. As shown in FIG. 4A, a user first removes the central body 216 of the sterile module 102. The sensor support 210, the introducer 212 and the sensor 150 extend from the bottom of the system 300 and are thus exposed.

[0067] FIG. 4B shows the attachment of the sensor system 300 to a patient 400. The sensor support 210 and the sensor 150 are inserted into the patient 400. The introducer 212 at the end of the support 210 assists in penetrating a skin surface 410. The skin surface 410 surrounding the point of insertion is in contact with the skin adhesive applied to the bottom surface of the base substrate layer 320.

[0068] After the base substrate layer 320 is attached to the skin surface 410 via the skin adhesive 350, the inserter cover 214 is pulled out of the donut 120 via the handle 218 as shown in FIG. 4C. The cover 214 and the sensor support 210 are thus removed from the donut 120 and discarded. As shown in FIG. 4D, the sensor 150 remains inserted in the patient 400 and continuous sensing of glucose levels from interstitial fluid in contact with the sensor 150 may be initiated through the transmitter module 340 and the other electronics on the flexible circuit board layer 324.

[0069] FIG. 5A shows a block diagram of the electrical components mounted on the circuit board 314 in FIGs. 3A-3D. FIG. 5A shows the sensor 150, the connector 344, the battery 342, and the transmitter module 340. The sensor 150 includes three electrodes, a working electrode, a reference electrode, and a counter electrode, that are coated with enzymes that react with glucose. An electrical input signal is input through the electrodes and an output signal is received through the connector 344 via the contact tab 220 shown in FIGs. 2A-2B. The signals from the connector 344 are connected to an analog front end circuit 510. The analog front end circuit 510 applies a precision bias to relative to the reference electrode and measures sensor current from the working electrode. In this example, the analog front end circuit 510 may make a precision bias current measurement with a 16-bit analog to digital converter (ADC) as well as performing electrochemical impedance spectroscopy (EIS). The electronics in the analog front end circuit 510 are designed to provide analog measurement capability at low operating power to be compatible with battery powered devices. A serial peripheral interface (SPI) allows access to the internal registers to program the analog front end circuit 510 as well as read the sensor data, and system voltages. [0070] The analog front end circuit 510 includes a system ADC that has a single-ended analog voltage input and a 12-bit binary digital word output. The ADC has four multiplexed external inputs and up to 22 multiplexed internal inputs. The internal inputs include sensor voltages and supply voltages. The input reference is programmable based on an input voltage supplied to a pin on the analog front end circuit 510. The analog front end circuit 510 includes an ADC dedicated to each sensor channel and measures a unipolar current out of the working electrode. A digital-to-analog converter (DAC) is shared by working and counter amplifiers for each sensor channel and between sensor channels for the 2 and 4-channel versions. The DACs are used to provide a DC bias to the sensors and can also be used to generate a sine wave to drive onto the sensor to measure the complex impedance of the sensor typically between the working and counter electrodes. Each sensor channel can bias and measure current in 2- and 3 -terminal electrochemical sensors. The analog front circuit end circuit 510 also includes an input coupled to a temperature sensor 512 for internal monitoring purposes.

[0071] The transmitter module 340 includes an internal memory 520 and a transmitter 522 that may be a BLE transmitter in one non limiting embodiment. The transmitter module 340 also includes a microprocessor 524, which is an ARM cortex processor in this example. The memory 520 may store algorithms or programs that control the functions of the microprocessor 524. For example, the microprocessor 524 may be programmed for interpreting the signal provided by the sensor 150, and for storing and/or communicating information regarding the patient’s blood glucose levels.

[0072] The memory 520 stores the readings from the sensor 150 and the transmitter 522 sends out the data to an external device. Such an external device may be used by patients and/or healthcare providers to, among other things, track the patient’s blood glucose level over time.

[0073] FIG. 5B shows a block diagram of the transmitter 522 in FIG. 5 A. The transmitter 522 includes an integrated antenna 540. The antenna 540 is connected to an RF matching circuit 542. A microcontroller 544 operates the transmitter functions for the transmitter 522. The microcontroller 544 is attached to a clocking crystal 546 and an antenna clocking crystal 548. The microcontroller 544 may communicate to other components via a serial bus 560. The microcontroller 544 may also receive input/output signals for an I/O connector 562.

[0074] In this example, input signals are sent to the sensor 150 periodically, such as every 10 second, every 30 seconds, every minute or every five minutes. The resulting output signals are read and converted by a program run by the microprocessor 524 to determine glucose concentration levels. The transmitter module 340 will store the glucose concentration level data in the internal memory 520. The transmitter module 340 will also include hand shaking protocols to an external device to download the glucose concentration level data.

[0075] FIG. 6A-6E show different examples of transmitter support assembly shapes other than the circular shapes of the transmitter support assemblies 104 and 310 in FIGs. 1A and 3 A. The different transmitter support base shapes in FIGs. 6A-6E may be fabricated with the different layered and potted assembly methods described above. FIG. 6A shows a transmitter support assembly 600 that is a three-lobe shape. FIG. 6B shows a transmitter support assembly 610 that also is in a three-lobe shape. FIG. 6C is a transmitter support assembly 620 that has a four lobe shape. FIG. 6D is a transmitter support assembly 630 that is in a rectangular shape. FIG. 6E is a transmitter support assembly 640 that is in an oval shape. Similar to the transmitter support assemblies in FIGs. 1A and 3 A, all of the support assemblies 600, 610, 620, 630, and 640 shown in FIGs. 6A-6E have a center aperture 602 for holding the donut 120 of the sterile module 102 in FIGs. 2A-2B.

[0076] As stated above, the transmitter support assembly footprint shapes have been envisioned to include different shapes such as circular, rectangular/strip, oval, 34obe, and 4- lobe. It is important to note that certain shapes may be advantageous over others in terms of user experience and comfort and that some shapes may require unique flexible circuit board and/or battery configurations. For example, the 3-lobe shaped transmitter support assemblies 600 and 610 in FIGs. 6A-6B could employ a flexible printed circuit board configuration which includes two batteries, each occupying one lobe, and all other electrical components occupying the third lobe. Crease lines or areas of greater flexibility would be designed and located to improve conformity and comfort.

[0077] FIG. 7A and 7B show different mesh designs for support within a transmitter support assembly such as those shown in FIGs. 1A and 3A. FIG. 7A shows a support mesh 700 that includes five arms 702 that each have two extending support members 704 and 706. Each of the arms 702 extends at equal radial intervals from a center member 710. FIG. 7B shows another example support mesh 750 that includes three arms 752 that each have two extending support members 754 and 756. The three arms 752 extend at equal radial intervals from a center member 760. The support mesh components may have different numbers of arms and support members. In addition, different mesh configurations may be employed.

[0078] The flexible support meshes 700 and 750 are a thin structure designed for two tasks. The first is serving as a platform for the assembly of the other components especially within the injection mold tooling cavity. The second purpose of the flexible support mesh 700 or 750 is to provide a ridged structure in some areas of the sensor system to improve structural stability, while allowing flexibility in other areas of the sensor systems. In this example, the mesh designs 700 and 750 may be materials such as nylon, polycarbonate or ABS and the like.

[0079] The battery in the above example is more bendable than totally flexible. The ability to bend is similar to thick aluminum foil which maintains its shape once no force is applied, as opposed to a type of rubber which is more elastic. The overall flexibility/malleability of the sensor system will increase if the larger relatively inelastic components such as the battery is broken up into smaller portions and spaced out on the body of the transmitter support assembly. This would allow the device to bend at specific joints or areas that are not covered by the surface area of the battery. For example, the battery can be split into more than one section in order to increase the flexibility of the device. This may be seen in the 3-lobe transmitter assemblies 600 and 610 shown in FIGs. 6A-6B, where two of the lobes can each hold a smaller size battery, which when wired in parallel, have the same storage capacity as the larger one-piece battery.

[0080] FIG. 8 shows a transmitter support assembly 800 according to another embodiment. The transmitter support assembly 800 includes three lobe members 802, 804, and 806. The lobe members 802, 804, and 806 extend from a central body 810. The central body 810 includes an aperture 812 that allows the insertion of a sensor such as that contained in the sterile module 102 shown in FIGs. 2A and 2B.

[0081] The lobe members 802 and 804 each mount a respective thin battery 822 and 824. The batteries 822 and 824 are wired in parallel and provide power to electronic components on the third lobe member 806 via traces 826. The electronic components on the third lobe member 806 may include a micro-processor 830 and an analog front end 832 for receiving signals from the sensor. As explained above, the use of the lobe members 804 and 802 allows for larger batteries and therefore an increase in useful life of the device.

[0082] Other examples of sensor transmitter assemblies may incorporate the disclosed principles herein. FIG. 9A is a side cut away view of a flexible continuous monitoring assembly 900 that has an integrated transmitter support assembly and sensor. The assembly 900 eliminates the separate sterile module containing the sensor as shown in FIGs. 2A-2B. The flexible continuous monitoring assembly 900 includes a base substrate layer 910, a potted cover layer 912, a flexible circuit board layer 914, and an optional base support layer 916. In this example, the base substrate layer 910 is a non-woven fabric like material such as the 3M 1776 single sided polyester non-woven medical tape. In this example, the potted cover layer 912 may be an elastic material such as liquid silicone rubber (LSR) or thermoplastic elastomer (TPE), urethane, silicone rubber, or a like material. The base substrate layer 910 may comprise materials such as polyester (PET), PP, and TREG. These and other flexible plastic materials would be used in thin sheets/films. In this example, the cover layer 912 has a generally dome shaped outer surface 918. It is to be understood, that other shapes may be used for the cover layer 912 such as a mesa shape with a flat top and tapered edges, or having a non-circular base footprints.

[0083] The cover layer 912 encases and protects electronic components mounted on the flexible circuit board layer 914. One set of such components includes a transmitter module 920 and a battery 922. The transmitter module 920 and the battery 922 may be similar to the transmitter and batteries described above in relation to FIGs. 3 A-3D. An upper surface of the base substrate layer 910 is attached to the flat surface of the base support 916 via an adhesive 930. The opposite surface of the base support 916 supports the flexible printed circuit board 914. The opposite lower surface of the base substrate layer 910 is coated with a skin adhesive 932 that adheres the assembly 900 to the skin surface of a user.

[0084] A center aperture 940 is formed through the base substrate layer 910, the cover layer 912, the flexible circuit board layer 914, and the base support layer 916. A sensor 942 extends through the center aperture 940 and out from the base substrate layer 910 for insertion into the skin. A support arm 944 of the sensor 942 is embedded in the cover layer 912. The sensor 942 is thus fixed to the assembly 900. Since the sensor 942 extends from the base substrate 910, the sensor 942 may be inserted in the skin until the base substrate layer 910 contacts the skin surface. The skin adhesive 932 keeps the assembly 900 attached to the skin.

[0085] Another example of an assembly 950 that has an insertable sensor module is shown in FIGs. 9B-9C. FIG. 9B is a side cutaway of the assembly 950 that shows an insertable sensor module 952 removed from a transmitter support assembly 954. FIG. 9C is a side cutaway view of the sensor module 952 assembled with the transmitter support assembly 954.

[0086] The transmitter support assembly 950 includes a base substrate layer 960, a potted cover layer 962, and a flexible circuit board layer 964. The cover layer 962 has a generally dome shaped outer surface 966. A socket member 970 is supported by an opening 972 formed in the center of the cover layer 962. The socket member 970 includes side walls 974 and a bottom plate 976. An aperture 978 is formed in the bottom plate 976 for insertion of the sensor.

[0087] The cover layer 962 encases and protects electronic components mounted on the flexible circuit board layer 964. One set of such components includes a transmitter module 980 and a battery 982. The transmitter module 980 and the battery 982 may be similar to the transmitter and batteries described above in relation to FIGs. 3 A-3D. An upper surface of the base substrate layer 960 is attached to a flat surface of the cover layer 962 via an adhesive 984. The opposite lower surface of the base substrate layer 960 is coated with a skin adhesive 986 that adheres the transmitter support assembly 954 to the skin surface of a user.

[0088] The sensor module 952 includes a support body 990 that is shaped to match the area formed by the walls 974 and the bottom plate 976 of the socket member 970. The support body 990 holds a sensor 992 extends through the center aperture 978 and out from the base substrate layer 960 for insertion into the skin. A support arm 994 of the sensor 992 is embedded in the support body 990.

[0089] The transmitter support assembly 954 is attached via the skin adhesive 986 to an area of the skin. The sensor module 952 is then inserted in the socket member 970. The sensor 992 extends through the aperture 978 and is thus inserted in the skin of the user when the support body 990 is inserted in the socket member 970.

[0090] The flexible and ultra-low profile continuous blood glucose monitor systems described above has several advantages over current sensor systems. The height of the system may be less than about 2.5 mm, and therefore the thin profile height of the system is half the height of certain existing sensor systems. This reduction in overall height will interfere with clothing less, be more discreet, and will improve overall comfort of the system.

[0091] A second advantage is the flexibility of the example sensor systems. The flexible construction and components allows the sensor system to be contoured to a user’s body through a range of motions and serves to increase overall user comfort. Critical components can be supported by rigid stiffeners in specific locations while maintaining overall flexibility. The battery will comprise of a thin, bendable material that allows for the potential splitting of the battery into multiple units in parallel.

[0092] It is to be understood that the example monitoring system disclosed herein combines novel design elements to provide a device that ensures that it may be worn comfortably under clothing, has a low profile and avoid impacts, presents a soft flexible feel and appearance, contour and moves with the dynamics of tissue flex, expansion and contraction. The disclosed device also protects the sensor site and internal hardware from fluid ingress and other use hazards, is applied easily and comfortably, provides breathability/air flow at skin adhesive area and creates a generally more user-friendly experience.

[0093] As used in this application, the terms“component,”“module,”“system,” or the like, generally refer to a computer-related entity, either hardware (e.g., a circuit), a combination of hardware and software, software, or an entity related to an operational machine with one or more specific functionalities. For example, a component may be, but is not limited to being, a process running on a processor (e.g., digital signal processor), a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a controller, as well as the controller, can be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. Further, a“device” can come in the form of specially designed hardware; generalized hardware made specialized by the execution of software thereon that enables the hardware to perform specific function; software stored on a computer-readable medium; or a combination thereof.

[0094] Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur or be known to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.

Claims

CLAIMS What is claimed is:

1. A flexible sensor system for continuous monitoring of a user, the sensor system comprising:

a base substrate layer for contact with skin of the user;

a circuit board layer located adjacent to the base substrate layer, opposite the skin; a sensor extending through the base substrate layer, the sensor configured to be insertable in the skin; and

a cover layer encasing the circuit board layer.

2. The flexible sensor system of claim 1, wherein the sensor is a glucose sensor and wherein the sensor is configured to contact interstitial fluid when inserted in the skin.

3. The flexible sensor system of claim 1, further comprising a microprocessor operable to receive an input signal from the sensor, the microprocessor mounted on the circuit board layer.

4. The flexible sensor system of claim 3, further comprising a memory to store data from the sensor.

5. The flexible sensor system of claim 4, further comprising a transmitter, the transmitter configured to send the data from the sensor to an external device.

6. The flexible sensor system of claim 1, wherein the base substrate layer and the cover layer form an aperture, the system further comprising a donut-shaped member mounted in the aperture of the base substrate layer and the cover layer.

7. The flexible sensor system of claim 1, further comprising a removable introducer member, the removable introducer member including a sensor support operable to support the sensor.

8. The flexible sensor system of claim 1, wherein the base substrate layer and the cover layer are one of a circular, a rectangular, an oval, a multi-lobed or a triangular shape.

9. The flexible sensor system of claim 1, further comprising a battery to power components on the circuit board layer.

10. The flexible sensor system of claim 9, wherein the battery is flexible.

11. The flexible sensor system of claim 9, wherein the battery is a coin cell battery.

12. The flexible sensor system of claim 1, further comprising a foam layer in contact with the cover layer.

13. The flexible sensor system of claim 1, wherein the base substrate layer, circuit board layer, and cover layer are assembled either by layering assembly or potting assembly.

14. The flexible sensor system of claim 1, wherein the cover layer is one of liquid silicone rubber, thermoplastic elastomer, urethane, silicone rubber, or thermoplastic urethane.

15. The flexible sensor system of claim 1, wherein the cover layer and the substrate base layer are a single component.

16. The flexible sensor system of claim 1, further comprising a support layer between the base substrate layer and the circuit board layer.

17. The flexible sensor system of claim 1, further comprising a skin adhesive coated on the base substrate layer.

18. A support assembly for a skin attached continuous monitoring system, the transmitter support assembly comprising:

a base substrate layer for contact to the skin of a user;

a circuit board layer adjacent the base substrate layer, opposite the skin;

a cover layer encapsulating the circuit board layer; and

an aperture formed by the base substrate layer and the cover layer for holding a sensor introducer module including a sensor.

19. The support assembly of claim 18, further comprising a microprocessor operable to receive an input signal from the sensor, the microprocessor mounted on the circuit board layer.

20. The support assembly of claim 19, further comprising a memory to store data from the sensor.

21. The support assembly of claim 20, further comprising a transmitter, the transmitter configured to send the data from the sensor to an external device.

22. The support assembly of claim 18, further comprising a donut-shaped member mounted in the aperture.

23. The support assembly of claim 18, wherein the base substrate layer and the cover layer are one of a circular, a rectangular, an oval, a multi-lobed or a triangular shape.

24. The support assembly of claim 18, further comprising a battery to power components on the circuit board layer.

25. The support assembly of claim 24, wherein the battery is flexible.

26. The support assembly of claim 24, wherein the battery is a coin cell battery.

27. The support assembly of claim 18, further comprising a foam layer imbedded under the cover layer.

28. The support assembly of claim 18, wherein the base substrate layer, circuit board layer, and cover layer are assembled either by layering assembly or potted assembly.

29. The support assembly of claim 18, wherein the cover layer is one of liquid silicone rubber, thermoplastic elastomer, urethane, silicone rubber, or thermoplastic urethane.

30. The support assembly of claim 18, wherein the base substrate layer has at least two lobes, and wherein a first lobe includes the circuit board layer, and a second lobe supports a battery.

31. The support assembly of claim 18, wherein the cover layer and the substrate base layer are a single component.

32. The support assembly of claim 18, further comprising a support layer between the base substrate layer and the circuit board layer.

33. The support assembly of claim 18, further comprising a skin adhesive coated on the base substrate layer to contact the skin.