The present disclosure generally relates to sensor electrodes, and more particularly relates to planar electrodes for invasive biosensors.
Biosensors may employ sensor wires that are inserted into a wearer's skin to detect the presence of an analyte, such as glucose, and provide an electrical signal indicating the amount or concentration of the analyte present. Such sensor wires may have diameters on the order of 100 microns, making them somewhat fragile. Thus, in some cases a wearer may apply a biosensor by first puncturing the wearer's skin with a needle and inserting the sensor wire through the puncture, and then affixing, e.g., adhering, the biosensor to the wearer's skin.
Various examples are described for planar electrodes for invasive biosensors. For example, one example device includes a housing attachable to a wearer's skin; an electrode assembly holder disposed within the housing, the electrode assembly holder comprising: a printed circuit board (“PCB”); a plurality of electrical contacts formed on the PCB; and an electrode assembly physically coupled to the PCB, the electrode assembly having a planar surface and having an invasive end and a device end, the electrode assembly comprising: a stack of alternating insulating and electrode layers, each layer screen-printed on a previous layer, and the stack formed on a substrate layer; a first chemical sensing material disposed on an invasive end of a first electrode layer of the electrode layers, a second chemical sensing material disposed on an invasive end of a second electrode layer of the electrode layers, the second chemical sensing material different from the first chemical sensing material; a polymer coating covering at least a portion of the invasive end of the electrode assembly; and wherein: the invasive end of the electrode assembly is insertable beneath the wearer's skin to sense multiple different analyte materials in the wearer's interstitial fluid; a device end of each electrode of the electrode assembly is electrically coupled to one of the electrical contacts; and the invasive end of the electrode assembly extends outside of the housing.
One example method includes providing a substrate material, the substrate material comprising a non-conductive material; screen-printing an electrode on the substrate material using a conductive material, the electrode having first and second ends opposite each other; applying a chemical sensing material to the first end of the electrode; and applying a polymer coating to at least an invasive end of the electrode.
One example electrode assembly includes a screen-printed electrode having first and second ends; a chemical sensing material disposed on the first end of the electrode; and a polymer coating covering at least a portion of an invasive end of the screen-printed electrode and the chemical sensing material.
Another example device includes a housing attachable to a wearer's skin; a electrode assembly holder disposed within the housing, the electrode assembly holder comprising: a substrate; a plurality of electrical contacts formed on the substrate; and an electrode assembly electrically coupled to the plurality of electrical contacts, the electrode assembly having a planar surface and comprising: a first screen-printed electrode having first and second ends; a chemical sensing material disposed on the first end of the electrode; and a polymer coating applied to the electrode; and wherein the first end of the screen-printed electrode extends outside of the housing and wherein a second end of each electrode is electrically coupled to one electrical contact of the plurality of electrical contacts.
These illustrative examples are mentioned not to limit or define the scope of this disclosure, but rather to provide examples to aid understanding thereof. Illustrative examples are discussed in the Detailed Description, which provides further description. Advantages offered by various examples may be further understood by examining this specification.
The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more certain examples and, together with the description of the example, serve to explain the principles and implementations of the certain examples.
Examples are described herein in the context of planar electrodes for invasive biosensors. Those of ordinary skill in the art will realize that the following description is illustrative only and is not intended to be in any way limiting. Reference will now be made in detail to implementations of examples as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following description to refer to the same or like items.
In the interest of clarity, not all of the routine features of the examples described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer's specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another.
An example wearable biosensor according to this disclosure, such as a continuous glucose monitor, may include one or more electrodes to be inserted into a wearer's skin or otherwise into the wearer's body, and thus are generally referred to as invasive electrodes. However, rather than the example electrode having a generally cylindrical shape with a substantially circular cross-section (in a plane orthogonal to the length of the electrode), the example biosensor employs a planar electrode.
A planar electrode refers to an electrode that has at least one substantially planar surface running the length of the electrode. Thus, rather than having a substantially circular cross-section, as described above, a cross-section of a planar electrode may be substantially rectangular (or polygonal) or may have one substantially planar surface that adjoins to a curved or other non-planar surface, e.g., in a half-moon cross-section.
For example, referring to
In this example, the planar electrode 120 is formed on a substrate 110 using a screen-printing process. Specifically, the planar electrode 120 is screen printed on the substrate in the shape shown using a platinized carbon ink The perimeter of the planar electrode 120 is designed, in this example, to provide a wider portion at one end 122, where the electrode 120 will be physically or electrically coupled to a sensor device (referred to as the “device end”), and a narrower portion at the other end 124, which will be inserted into the wearer's skin (referred to as the “invasive end”).
In this example, the electrode 120 is the entirety of an invasive sensor wire to be used with an invasive biosensor; however, as will described in more detail below, an invasive sensor wire may include multiple electrodes formed in a stack on top of each other, separated by insulation layers, thereby providing a single electrode assembly that provides multiple discrete electrodes. Such sensor wire assemblies may enable sensing of multiple different analytes with a single sensor wire. Screen printing the electrode may enable manufacturing the electrodes in different shapes or sizes according to different application requirements. In addition, it may facilitate creating a single electrode assembly that includes multiple different electrodes having sensing chemicals.
Further, because the fabrication of the electrode assembly may be performed entirely using screen printing techniques (described below), formation and handling of the sensor wire during the sensor manufacturing process may be easier than provided by conventional techniques. For example, due to the size and shape of the sensor wire assemblies, high-volume manufacturing processes, e.g., automated processes that may include robotic components, may have difficulty picking up, grasping, or otherwise handling the sensor wires without damaging them. However, because some examples according to this disclosure are screen printed on substrate backings, the robot may be able to grasp the substrate and avoid contact with the electrode assembly itself. Thus, in addition to providing a different electrode assembly configuration, the screen printing process may also facilitate the manufacture of the sensor device itself.
In some examples, an electrode assembly with a stack of alternating electrode and insulation layers that have been screen-printed on a planar substrate, where multiple electrode layers have a sensing chemical (in any desirable combination), and where none of the electrode layers provide a working or counter electrode, may provide a desirable analyte sensor implementation. Such an electrode assembly may be easily constructed using screen-printing techniques, may be easily handled and manipulated during the manufacturing process due to the planar substrate material (on which the electrode assembly is formed), and may enable sensing multiple different analytes by the same wearable sensor at substantially the same location within the wearer's skin. Thus, such a monolithic electrode assembly provides advantages in construction of electrode assemblies and manufacture of wearable biosensors.
Further, because a single electrode assembly can sense multiple different analytes via single insertion point into a wearer's skin, other advantages may be realized. For example, one of the electrode layers may not have a sensing chemical and thus may provide a “blank” electrode that provides information about signal interference at the sensing location, which may be usable with respect to each different sensed analyte. Further, because the invasive portion of the electrode assembly is inserted through the same insertion point, the wearer only needs to puncture their skin once and wear a single biosensor, which may reduce discomfort and impact on the wearer when the biosensor is applied. In addition, a monolithic sensor assembly that lacks a counter electrode and a reference electrode may reduce the overall size of the electrode assembly, reduce the complexity of design and manufacture of the assembly, and may enable the use of non-invasive counter or reference electrodes.
In addition, some example electrode assemblies may include one or more working electrodes, but may not include either or both of a counter electrode or a reference electrode. For example, one or both of a counter or reference electrodes may be provided via a non-invasive electrode(s), such as an electrode attached to the wearer's skin. One advantage of some such arrangements may be that the electrode assembly may be substantially planar and cause less discomfort to the wearer upon insertion or while it is worn. Further, in examples where the electrode assembly lacks either or both of a counter or reference electrode, the electrode assembly may be thin enough to stack multiple working electrodes in the same electrode assembly, rather than devoting one or more layers to a working or counter electrode. Still further advantages according to this disclosure may be realized according to different examples.
This illustrative example is given to introduce the reader to the general subject matter discussed herein and the disclosure is not limited to this example. The following sections describe various additional non-limiting examples and examples of planar electrodes for invasive biosensors.
Referring now to
Beginning with
One or more planar electrodes 220a-d may then be screen printed on the substrate material 210, separated from adjacent electrodes by a suitable gap, such as 1-2 millimeters (“mm”) or more. In some examples, the distance between discrete electrodes may be set based on a midline of each electrode. For example, electrodes may be formed such that the midline of one electrode is spaced 10 mm from the midline of each adjacent electrode.
The electrodes 220a-d may be screen printed using any suitable conductive material. For example, platinized carbon ink, a conductive carbon ink, or any other suitable conductive ink may be employed according to some examples. The electrodes 220a-d may be screen printed with a predetermined thickness, such as 5 microns or greater.
In this example, the planar electrodes 220a-d each include an electrode assembly having only a single electrode having a thickness of between substantially 1 to 15 microns. However, as will be discussed in more detail below with respect to
Referring now to
In
For example,
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As can be seen in
The thickness (shown in
For example, referring to
Referring now to
In addition, a portion of the device end of each electrode is also exposed, e.g., 526b. Such a configuration may enable a physical or electrical connection between each electrode 522-528 and a sensor printed circuit board (“PCB”) or other mounting structure. Thus, to the device end of each exposed electrode portion, a coupling device, such as a metal clip or crimp, may be used to physically grip the electrode and to provide an electrical connection to other electronics within the sensor device. In some examples, portions of one or more insulation layers may be exposed to provide additional or alternate locations to physically couple the electrode assembly to a sensor device without a corresponding electrical coupling. In one such example, electrical couplings may be applied to each exposed device portion of each electrode 522-528, and a physical coupling may be applied to each exposed device portion of each insulation layer 530-534.
After the electrode assembly 520 has been screen printed and sensor chemicals 540 have been applied to one or more of the electrodes 522-528, the electrode assembly 520 may have a polymer coating 550 applied to it, such as by dipping the invasive end 525 of the electrode assembly 520 into a bath of a suitable liquid polymer solution.
Referring now to
The electrode assembly 620 has been physically coupled to the PCB by three clamps 632. In this example, the clamps 632 have two halves that are each physically coupled to the PCB 610 and have been bent closed over the exposed portions of the insulation layers 630 of the sensor assembly 620. And while this example employs clamps, other examples may use different means for physically coupling the electrode assembly 620 to the PCB 610, including clasps, leaf springs, etc.
The electrode assembly 620 is also electrically coupled to the PCB 610 via four electrical contacts 640. Each electrode 622-628 is electrically coupled to a different one of the electrical contacts 640 to provide individual electrical connections between the respective electrode and the PCB 610. Each electrical contact 640 in this example runs from the respective electrode 622-628 to a corresponding via, which provides an electrical coupling to other electronics within a suitable sensor device. In this example, each electrical contact 640 includes a leaf spring is coupled to the PCB 610 and presses against the respective electrode 622-628 to provide an electrical coupling. However, it should be understood that any suitable means for electrically coupling an electrode 622-628 may be employed according to different examples, including clamps, crimps, clasps, solder, etc. Further, it should be appreciated that the means for electrically coupling may also provide a physically coupling. Similarly, one or more of the means for physically coupling may be also provide an electrical coupling. For example, the clamps 632 in some examples may be omitted and the electrical contact 640 may provide both a physical and an electrical coupling of the electrode assembly 620 to the PCB 610. In one such example, the electrode assembly may be not provide exposed portions of insulation layers, and instead, may only expose the different electrodes to provide for both physical and electrical coupling, such as shown in
While the example shown in
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In the example shown in
The example shown in
Referring now to
At block 710, substrate material 310 is provided. Suitable substrate materials, such as those described above, include PET, polyimide, or any other suitable plastic or otherwise non-conductive material.
At block 720, a first electrode 322 is screen printed on the substrate material 310. As discussed above, any suitable conductive ink may be employed to screen print the electrode 322, including a platinized carbon ink, a conductive carbon ink, etc. The first electrode 322 may be screen printed in any suitable shape. For example, referring to
The first electrode 322 may be screen printed with any suitable thickness. A thickness of the first electrode 322 may be established by screen printing the first electrode in layers such that the first electrode has multiple layers of conductive ink to form the first electrode. In some examples the first electrode may be screen printed in a single layer of a predetermined thickness. Suitable thicknesses may range from 1 to 15 microns or more.
At block 730, an insulation layer 330 is screen printed on top of the first electrode 322. In this example, the insulation layer 330 is screen printed using a suitable non-conductive ink, such as a dielectric ink The insulation layer 330 is screen printed to leave a portion of the invasive end of the first electrode 322 exposed without an insulation layer 330 screen printed on it. Such a configuration may allow the first electrode 322 to be exposed to interstitial fluid when inserted into a wearer's skin and to allow a sensor chemical 340 to later be deposited on it. In some examples, a portion of the device end of the first electrode 322 may remain exposed as well, such as may be seen in the example electrode assembly shown in
The thickness of the insulation layer 300 may be established as discussed above with respect to the first electrode, such as by screen printing multiple layers of non-conductive ink or be screen printing a single layer of a suitable thickness. As with the first electrode, suitable thicknesses may range from 1 to 15 microns or more.
At block 740, a second electrode 324 is screen printed on top of the insulation layer 330. The second electrode 324 is screen printed using any suitable conductive ink, such as those discussed above. The second electrode 324 in this example is only screen printed on the insulation layer 330 such that the second electrode 324 is electrically isolated from the first electrode 322. While in some examples it may be desirable to provide an electrical coupling between the first and second electrodes 322, 324, in this example, the two electrodes 322, 324 are electrically isolated by the insulation layer 330. Thus, the second electrode 324 is screen printed on the insulation layer 330. In this example, the second electrode 324 is screen printed such that it is coextensive with the insulation layer 330; however, in some examples, a portion of the insulation layer, at either or both ends of the electrode assembly 320, may remain exposed. An example of one such configuration is shown in
While in this example, only two electrodes 322, 324 are formed, in some examples, more than two electrodes may be formed in a stack by continuing to screen print alternating layers of insulation and electrode material. For example, the example electrode shown in
At block 750, a second insulation layer 332 is screen printed on top of the second electrode 324, generally as discussed above with respect to block 730. After block 750 has been completed, the method 700 may proceed to block 760, or it may return to block 740 to add additional layers of alternating electrodes and insulation layers. Blocks 740-750 may be repeated as many times as needed to create a suitable stack of alternating electrode and insulation layers.
At block 760, the electrode assembly is laser cut to the precise designed dimensions for the electrode assembly. Laser cutting may enable the dimensions of each electrode 322-324 and each insulation layer 330 to be precisely sized and shaped for a particular application. It should be appreciated, however, the laser cutting is optional and the size and shape may be established by the screen printing process.
At block 770, a sensor chemical 340 may be applied to one or more electrodes 322-324 of the electrode assembly 320. Any suitable sensor chemical, such as those described above, may be applied at block 760. In this example, a sensor chemical 340 is applied to the exposed invasive end of the first electrode 322, while no sensor chemical is applied to the second electrode 324. However, sensor chemicals may be applied to any or all electrodes within an electrode assembly. Further, different sensor chemicals may be applied to different electrodes. Such configurations may enable testing of multiple analytes with a single sensor assembly. Alternatively, the same sensor chemical may be applied to multiple electrodes, which may provide multiple sensor signals to sensor electronics for the same analyte, which may provide a more reliable measure of the analyte in the wearer's interstitial fluid. Further, one or more electrodes may not have a sensor chemical applied. In some examples, such electrodes without an applied sensor chemical may provide a reference electrode or another baseline signal to sensor electronics to enable more accurate analyte sensor measurements.
At block 780, a polymer coating 350 is applied to the electrode assembly 320. In this example, the electrode assembly is dipped in a liquid polymer bath. In some examples, however, a liquid polymer may be sprayed onto the electrode assembly 320. For example, the substrate may be used to grasp and dip the electrode assembly into a liquid polymer bath.
After the polymer coating 350 is applied, the electrode assembly 320 may be installed in a sensor device. For example, the electrode assembly 320 may be physically coupled to a PCB or other substrate and electrically coupled to one or more electrical contacts on the PCB or substrate to electrically couple the electrode assembly to sensor electronics within the sensor device.
It should be appreciated that one or more blocks of the method 700 is optional. For example, blocks 730 to 750 may be omitted in examples where an electrode assembly includes only one electrode. Further block 760 may be omitted if laser cutting is not desired or otherwise is not available. Block 780 may be omitted if a polymer coating is not desirable or available. Further, the orderings of the blocks shown in
Referring now to
At block 810, a sheet of substrate material 210 is provided substantially as described above with respect to block 710.
At block 820, multiple first electrodes 220a-d are screen printed on the substrate material 210 substantially as described above with respect to block 720. Each first electrode is screen printed at a pre-defined spacing on the substrate material 210. The pre-defined spacing may enable the electrodes 220a-d to later be singulated without damaging or cutting the electrodes 220a-d themselves.
At block 830, insulation layers are screen printed on each first electrode 220a-d substantially as discussed above with respect to block 730. In this example, an insulation layer is screen printed on each first electrode; however, depending on the configuration of each electrode assembly to be manufactured, an insulation layer may not be screen printed on one or more first electrodes.
At block 840, a second electrode is screen printed on one or more of the electrode assemblies substantially as described above with respect to block 740. As discussed above, the second electrodes are screen printed on the respective insulation layers. Thus, for any first electrodes that did not have an insulation layer applied, a second electrode may not be screen printed. Further, and as described above, blocks 730-740 may be repeated as many times as desired to create an electrode assembly having any suitable number of electrodes with intervening insulation layers. Since each electrode assembly formed on the substrate material 210 may have a different design, adjacent electrode assemblies may have different numbers of electrodes.
At block 850, a second insulation layer is screen printed on top of the second electrode, generally as discussed above with respect to block 830. After block 850 has been completed, the method 800 may proceed to block 860, or it may return to block 840 to add additional alternating electrode and insulation layers. Blocks 840-850 may be repeated as many times as needed to create a suitable stack of alternating electrode and insulation layers.
At block 860, one or more of the electrode assemblies is laser cut substantially as described above with respect to block 750. Further, and as described above, laser cutting is optional and may not be performed in some examples.
At block 870, a sensor chemical is applied to one or more electrodes of each electrode assembly substantially as described above with respect to block 760. Further, because each discrete sensor assembly may be designed for a different purpose, each sensor assembly may have a different sensor chemical (or multiple sensor chemicals) applied to it according to different examples.
At block 880, the electrode assemblies are singulated as shown in
At block 890, a polymer coating is applied to each electrode assembly substantially as described above with respect to block 780.
After the polymer coating has been applied, the electrode assemblies may be installed in sensor devices. For example, the electrode assemblies may be physically coupled to a respective PCB or other substrate and electrically coupled to one or more electrical contacts on the PCB or substrate to electrically couple the respective electrode assembly to sensor electronics within the respective sensor device.
Further, it should be appreciated that one or more blocks of the method 800 is optional. For example, blocks 830 and 840 may be omitted in examples where an electrode assembly includes only one electrode. Further block 860 may be omitted if laser cutting is not desired or otherwise is not available. Block 890 may be omitted if a polymer coating is not desirable or available. Further, the orderings of the blocks shown in
The foregoing description of some examples has been presented only for the purpose of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Numerous modifications and adaptations thereof will be apparent to those skilled in the art without departing from the spirit and scope of the disclosure.
Reference herein to an example or implementation means that a particular feature, structure, operation, or other characteristic described in connection with the example may be included in at least one implementation of the disclosure. The disclosure is not restricted to the particular examples or implementations described as such. The appearance of the phrases “in one example,” “in an example,” “in one implementation,” or “in an implementation,” or variations of the same in various places in the specification does not necessarily refer to the same example or implementation. Any particular feature, structure, operation, or other characteristic described in this specification in relation to one example or implementation may be combined with other features, structures, operations, or other characteristics described in respect of any other example or implementation.
Use herein of the word “or” is intended to cover inclusive and exclusive OR conditions. In other words, A or B or C includes any or all of the following alternative combinations as appropriate for a particular usage: A alone; B alone; C alone; A and B only; A and C only; B and C only; and A and B and C.
This application claims priority to U.S. Provisional Patent Application No. 62/663,092, filed Apr. 26, 2018, titled “Planar Electrodes for Invasive Biosensors,” the entirety of which is hereby incorporated by reference.
Number | Date | Country | |
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62663092 | Apr 2018 | US |