Application of anisotropic materials in flexible printed capacitive sensors

Abstract

Disclosed embodiments include a flexible sensor having a flexible capacitive sensing region and at least one motion limiter that prevents bending along a limiting axis in at least a portion of the flexible capacitive sensing region.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Patent Application No. 63 / 379,979, filed October 18, 2022, entitled "Anisotropic Materials Applications In Printed Flexible Capacitive Sensors," the contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to compliance sensor systems and methods for sensors that undergo bending, flexion, extension, torsion, etc. due to measurement, force, strain, stress, etc. More particularly, the present disclosure relates to compliance sensor systems and methods for sensors configured to have anisotropic kinematic behavior. [Background technology]

[0003] Flexible sensors are known. For example, U.S. Patent Nos. 8,941,392, 9,222,764, 9,476,692, 9,612,102, 9,874,431, 10,551,917, 10,823,546, 10,959,644, and U.S. Patent Application Publication No. 2022 / 0034692 disclose flexible sensors, the contents of which are incorporated herein by reference. However, there are also cases where a defined directional measurement or comparison is required using a flexible sensor. Existing flexible sensors typically exhibit an isotropic response to a given range of bending or strain, typically providing a magnitude but not a direction for a given measurement.

[0004] In theory, if the undesired axis dimension (i.e., the direction in which measurement is not desired) were reduced to an infinitesimally small value, the integral of the strain recorded by the sensor would be dominated by the desired axis (i.e., the direction in which measurement is desired). In practice, this approach does not work, particularly due to the high resistivity of the sensor's conductive layer. Current systems and methods also have other drawbacks, inconveniences, inefficiencies, and challenges. Summary of the Invention [Problem to be solved by the invention]

[0005] Thus, the disclosed embodiments address these and other drawbacks, inconveniences, inefficiencies, and problems that exist in current systems and methods. The disclosed systems and methods also offer other advantages and efficiencies. [Means for solving the problem]

[0006] As used herein, the terms "flexible," "extensible," "compliant," "deformable," etc. are used somewhat interchangeably and all mean that there is some degree of bending, stretching, compression, twisting, curvature, etc. to the embodiment being described.

[0007] As used herein, the terms "undesired axis," "restricted axis," "unmeasured axis," etc., all refer to a direction in which a sensor measurement or reading is undesired. Similarly, as used herein, the terms "desired axis," "unrestricted axis," "measured axis," etc., all refer to a direction in which a sensor measurement or reading is desired.

[0008] As used herein, it is understood that the terms "vertical," "horizontal," "lateral," "upper," "lower," "top," "bottom," "left," "right," "inner," "outer," etc. may refer to the relative orientation or location of features in the disclosed devices and / or assemblies shown in the figures. For example, "upper" or "uppermost" may refer to one feature being located closer to the top of the page than another feature. However, these terms are intended to be broadly interpreted to include devices and / or assemblies having other orientations, such as inverted or tilted orientations, in which top / bottom, upper / lower, above / below, top / bottom, and left / right are interchangeable depending on the orientation.

[0009] An exemplary embodiment of the disclosure includes a compliance sensor having a non-stretchable fiber parallel to the non-measurement axis. The fiber physically resists the force induced by the deformation source up to the point of breakage of the fiber. In this way, the signal from the constrained, non-measurement axis is filtered out, leaving only the measurement from the non-constrained axis. Other embodiments also exist. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of stack layers that make up a compliance sensor system according to a disclosed embodiment. FIG. [Figure 2] FIG. 1 illustrates a multi-zone angular displacement sensor according to an embodiment of the disclosure. [Figure 3] 1A-1C illustrate a schematic example of a deformable isotropic flexible printed capacitive sensor system according to an embodiment of the disclosure. [Figure 4] 1A-1C illustrate a schematic example of a deformable anisotropic flexible printed capacitive sensor system according to an embodiment of the disclosure. [Figure 5] FIG. 1 is a schematic representation of an anisotropic sensor system with a motion limiter in the signal trace, according to an embodiment of the disclosure. [Figure 7] FIG. 1 is a schematic representation of an anisotropic sensor system embedded in an adhesive, according to an embodiment of the disclosure. [Figure 6A] FIG. 1 is a schematic diagram of an anisotropic sensor system according to an embodiment of the disclosure. [Figure 6B] FIG. 1 is a schematic diagram of an anisotropic sensor system according to an embodiment of the disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are herein described in detail. It is to be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0012] 1 is a schematic cross-sectional view of a stack of layers 200 that make up a compliance sensor system. As shown, a dielectric layer 12 is located between a top electrode layer 2 and a signal electrode layer 16. Also shown schematically is a peripheral electrode 140 that electrically connects the top electrode layer 2 and the signal electrode layer 16. Other configurations are also possible.

[0013] In some embodiments, the top electrode layer 2 may comprise an elastomer layer (e.g., silicone) incorporating conductive particles (e.g., nanoparticles such as carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, graphene oxide, etc.). Although shown as a continuous layer in FIG. 2, the top electrode layer 2 may be "hatched" or discontinuous. The top electrode layer 2 may also include a printed circuit board (PCB) interface and a number of conductive trace pads for attaching the PCB, sensor traces, or other electronics for operation and control of the sensor system.

[0014] In some embodiments, dielectric layer 12 may comprise an elastomeric material (e.g., silicone) and may optionally incorporate some conductive material, depending on, among other things, the desired dielectric constant, etc. Although not drawn to scale in Figure 1, in some embodiments, dielectric layer 12 is sized slightly smaller than top electrode layer 2 so that the periphery of top electrode layer 2 is not covered by dielectric layer 12, allowing electrical contact with peripheral electrode 140 as disclosed below.

[0015] In some embodiments, the signal electrode layer 16 may include an elastomeric material (e.g., silicone) with a conductive material (e.g., nanoparticles such as carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, graphene oxide, etc.) limited to the sensor regions, traces, and perimeter electrode 140. Many sensor regions 20 (labeled "sensing regions" in FIG. 3 and used interchangeably herein with "sensor regions") may be distributed throughout this layer 116 (see, e.g., FIG. 3). The sensor regions 20 may include regions of conductive material. The sensor regions 20 are in electrical communication with traces 22 (labeled "signal trace lines" in FIG. 3 and used interchangeably herein with "trace"). As shown, embodiments of the signal electrode layer 16 may include a perimeter electrode 140 electrically connected to the top electrode layer 2 to, among other things, provide electrical isolation for the entire sensor system. Other configurations are also possible.

[0016] FIG. 2 illustrates a multi-region angular displacement sensor 800, according to a disclosed embodiment. As shown, embodiments of sensor systems 200, such as those disclosed in FIG. 1, may be coupled together to form angular displacement sensor 800. For example, angular displacement sensor 800 (single-region, multi-region, etc.) may be achieved by coupling sensor system 200A to a second sensor system 200b through an elastomeric connector 802. Additional disclosure regarding the construction, operation, and implementation of such displacement sensor systems 800 can be found in U.S. Pat. No. 10,551,917, entitled "Compliant Multi-Region Angular Displacement And Strain Sensors," the entire disclosure of which is incorporated herein by reference.

[0017] As will be understood by those skilled in the art having the benefit of this disclosure, angular displacement sensor 800 may be expanded to any desired number of regions, as illustrated by additional elastomeric connectors 802 and sensor system 200N. Other configurations are also possible.

[0018] 3 is a schematic illustration of a deformable isotropic flexible printed capacitive sensor system 300 according to a disclosed embodiment. As shown, at least one sensing region 20 is included in an elastomeric material and may include one or more signal traces 22 for electronic communication with other system circuits and components. Other configurations are possible.

[0019] 4 is a schematic illustration of a deformable anisotropic flexible printed capacitive sensor system 400 according to a disclosed embodiment. As shown, the anisotropic sensor system 400 includes a motion limiter 24 in the sensing region 20 that limits or prevents bending or stretching along a limiting axis. In some embodiments, the motion limiter 24 may include carbon fiber, polyparaphenylene terephthalamide (e.g., Kevlar®) fiber, woven fiber, glass fiber, non-stretch film, epoxy, or the like. Additionally, the motion limiter 24 may be conductive or non-conductive as desired.

[0020] As shown schematically in FIG. 4, an anisotropic sensor system 400 allows for measurement of bending or stretch in the "vertical" (up and down the page) direction while limiting measurement of bending or stretch in the "horizontal" (left and right of the page) direction. Generally, a motion limiter 24 may be printed, mounted, or included in the sensor 400 parallel to the preferred limiting direction, allowing measurement of bending or stretch in a direction perpendicular to the alignment of the motion limiter 24. Of course, those skilled in the art, having the benefit of this disclosure, will understand that any measurement direction can be achieved by appropriately selecting the presence or absence of a motion limiter 24. For example, with reference to FIG. 4, a "diagonal" pattern of motion limiters 24 would allow measurement of bending or stretch in a 45° (or other angle) direction (e.g., from the bottom left corner to the top right corner of the page). Additionally, the motion limiters 24 may be oriented in more than one axis (e.g., a cross-hatch pattern) to prevent measurement of bending or stretch in more than one direction at a time. Other embodiments are also possible.

[0021] Additionally, the spacing of the motion limiters 24 can vary as desired. For example, this spacing can depend on the desired minimum deformation body size. Generally, the contact area between the deformation body and the sensing region 20 should be greater than the spacing of the motion limiters 24 so as to contact at least one limiter 24. Other embodiments are also possible.

[0022] FIG. 5 is a schematic representation of an anisotropic sensor system 500 including a motion limiter 24 for a signal trace 22, according to disclosed embodiments. In some embodiments, anisotropic confinement of a signal trace 22 in a deformable flexible sensor may be desirable, particularly to mitigate undesirable effects of signals generated as a by-product of deformation of the signal trace 22. As shown, one or more signal traces 22 may be in electrical contact with the sensing region 20. As shown in enlarged section "A," a motion limiter 24 may be included for confinement in one direction (up and down the page) and for deformation in a perpendicular direction (left and right of the page). In some embodiments, a two-way confinement may be desirable, as shown in enlarged section "B," where a motion limiter 24A is provided in one direction (left and right of the page) and a motion limiter 24B is provided in a second direction (up and down the page) to simultaneously limit bending or extension in two directions. In multi-directional confinement embodiments, the motion limiter 24 may be a single layer, multiple layers, a woven layer, or the like. Other configurations and embodiments are also possible.

[0023] 6A and 6B are schematic diagrams of anisotropic sensor systems 600A and 600B, according to embodiments of the disclosure. As shown schematically, the motion limiter 24 may be disposed on any layer of the sensor system. For example, as shown in FIG. 6A, the motion limiter 24 may be disposed on a conductive layer (e.g., signal layer 16), or as shown in FIG. 6B, the motion limiter 24 may be disposed on a non-conductive layer (e.g., dielectric layer 12).

[0024] In general, the motion limiter 24 may be conductive and bonded directly onto a given electrode layer (e.g., top electrode 2, signal electrode 16, etc.). This provides the added benefit of making the electrode more conductive if the motion limiter 24 is more conductive than the electrode. Alternatively, in the case of a conductive motion limiter 24, the signal layer 16 may be replaced by the conductive motion limiter 24. Alternatively, the motion limiter 24 may be bonded onto a conductive layer. If included in a signal trace 22, if the motion limiter 24 has a lower resistivity than the electrode layer, the conductor loss of the signal trace 22 will be reduced. Other advantages and embodiments also exist.

[0025] 7 is a schematic representation of an anisotropic sensor system 700 embedded in an adhesive 704, according to disclosed embodiments. For example, an anisotropic element (e.g., carrier layer 706) having an anisotropic motion limiter 24 (not shown in FIG. 7 ) may be embedded in an adhesive (e.g., layer 704) used to bond all or specific portions of the sensor system 700 to a target substrate (e.g., the inside of a tire, etc.). In some embodiments, a liner layer 702 may be provided to, among other things, protect the outer adhesive layer 704. Other configurations and embodiments are also possible.

[0026] While various embodiments have been shown and described above, it is understood that the disclosure is not limited thereto, but includes all such modifications and variations as would become apparent to one skilled in the art.

Claims

1. a flexible capacitive sensing area; at least one motion limiter that prevents bending of at least a portion of the flexible capacitive sensing region along a limiting axis; A flexible sensor comprising:

2. The flexible sensor of claim 1 , wherein the motion limiter further comprises at least one of carbon fiber, polyparaphenylene terephthalamide fiber, woven fiber, glass fiber, a non-stretchable film, or epoxy.

3. The flexible sensor of claim 1 , further comprising one or more signal trace lines in electronic communication with the flexible capacitive sensing region.

4. The flexible sensor of claim 3 , further comprising at least one motion limiter that prevents bending of at least a portion of the one or more signal trace lines along a limiting axis.

5. The flexible sensor of claim 3 , further comprising at least two motion limiters in at least a portion of the one or more signal trace lines that prevent bending along two limiting axes.

6. a flexible capacitive sensing area; one or more signal trace lines in electronic communication with the flexible capacitive sensing area; at least one motion limiter that prevents bending of at least a portion of the one or more signal trace lines along a limiting axis; A flexible sensor comprising:

7. The flexible sensor of claim 6 , wherein the motion limiter further comprises at least one of carbon fiber, polyparaphenylene terephthalamide fiber, woven fiber, glass fiber, a non-stretchable film, or epoxy.

8. The flexible sensor of claim 6 , further comprising at least two motion limiters in at least a portion of the one or more signal trace lines that prevent bending along two limiting axes.

9. an elastomer signal electrode layer; an elastomeric top electrode layer; an elastomer dielectric layer between the signal electrode layer and the top electrode layer; at least one motion limiter that prevents bending along a limiting axis; An anisotropic flexible sensor comprising:

10. 10. The anisotropic flexible sensor of claim 9, wherein at least a portion of said at least one motion limiter is disposed in said dielectric layer.

11. 10. The anisotropic flexible sensor of claim 9, wherein at least a portion of said at least one motion limiter is disposed on at least one of said signal electrode layer or said top electrode layer.

12. 10. The anisotropic flexible sensor of claim 9, wherein the motion limiter further comprises at least one of carbon fiber, polyparaphenylene terephthalamide fiber, woven fiber, glass fiber, a non-stretchable film, or epoxy.

13. 10. The anisotropic flexible sensor of claim 9, further comprising at least one adhesive layer that enables attachment of said anisotropic flexible sensor to a target substrate.

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