Piezoelectric Energy Harvester

Abstract

A piezoelectric composite energy harvester (100) is disclosed, comprising a piezoelectric element (102) and an elastic cover layer (110). The piezoelectric element comprises a first electrode (104), a second electrode (106), and a piezoelectric layer (108), the piezoelectric layer (108) comprising a cross-linked silicone elastomer matrix and piezoelectric particles dispersed within the cross-linked silicone elastomer matrix. The elastic cover layer (110) is disposed over the exterior of the second electrode (106). The piezoelectric composite energy harvester is configured to bend, expand, contract, rotate, tilt, and / or move in any spatial direction.

Description

[Technical Field]

[0001] Inventors: Zhang Yiling and Matsukuma Daisuke

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 478,909, filed January 6, 2023, which is incorporated by reference in its entirety. [Background technology]

[0003] Unless otherwise stated in this disclosure, the details described in this disclosure are not prior art to the claims of this application and are not admitted to be prior art by inclusion in the background art.

[0004] The piezoelectric effect, which induces an electric charge in response to applied mechanical strain, can be used to convert mechanical energy into electrical energy. As a result, piezoelectric materials are widely used to harvest energy from the environment or object motion and to power personal electronics, nanodevices, wireless sensors, and more. High mechanical flexibility is often desirable to expand the application range of piezoelectric materials. However, bulk piezoelectric ceramics such as PZT have a high piezoelectric coefficient but low flexibility, while piezoelectric polymers such as polyvinylidene fluoride (PVDF) have high flexibility but a relatively low piezoelectric coefficient. PVDF has a limitation: its lack of elasticity makes it difficult to conform to three-dimensional curved surfaces. In addition, PVDF-based piezoelectric harvesters are prone to peeling or lifting from their mounting surfaces due to repeated deformation. This can be particularly challenging when the target surface is constantly bending, such as the inner surface of an inflatable vehicle tire. Piezoelectric composites based on polydimethylsiloxane (PDMS or silicone) can exhibit high compliance and deformation resistance, but generate significantly less power.

[0005] Therefore, there is a need for piezoelectric harvesters for non-planar substrates that provide increased flexibility without sacrificing power generation. Summary of the Invention

[0006] SUMMARY OF THE INVENTION Embodiments of the present disclosure address the above-mentioned problems and generally relate to a laminate structure for a piezoelectric composite energy harvester that generates power in non-planar environments.

[0007] Some embodiments include a piezoelectric composite energy harvester comprising a piezoelectric element. In some embodiments, the piezoelectric element may comprise a first electrode, a second electrode, and a piezoelectric layer comprising a cross-linked silicone elastomer matrix and piezoelectric particles, with the piezoelectric particles dispersed within the cross-linked silicone elastomer matrix in the piezoelectric layer. In some embodiments, the first electrode and the second electrode are disposed on a first side of the piezoelectric layer and a second side of the piezoelectric layer, respectively. In some embodiments, the first electrode and the second electrode may comprise a conductive material and silicone. In some embodiments, the conductive material may comprise conductive particles. In some embodiments, the conductive particles may comprise carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, and / or graphene oxide. In some embodiments, the piezoelectric composite energy harvester may be configured to bend, expand, contract, rotate, tilt, and / or move in any spatial direction upon exposure to mechanical stress.

[0008] In some embodiments, the piezoelectric energy harvester may include an elastic cover layer. In some embodiments, the elastic cover layer may be contiguous with the second electrode. In some embodiments, the elastic cover layer may be disposed to cover an outer side of the second electrode. In some embodiments, the elastic modulus of the elastic cover layer is less than the elastic modulus of the piezoelectric element. In some embodiments, the elastic cover layer may include silicone.

[0009] In some embodiments, the thickness ratio of the elastic cover layer to the piezoelectric element is about 0.01 or greater. In some embodiments, the thickness ratio of the elastic cover layer to the piezoelectric element is greater than about 0.01 and less than about 2. In some embodiments, the piezoelectric composite energy harvester has a tensile stress at 20% elongation of about 1.5 to about 4 MPa. In some embodiments, the piezoelectric composite energy harvester has a tensile stress at 35% elongation of about 1.5 to about 4 MPa. In some embodiments, the piezoelectric composite energy harvester has a tensile stress at 40% elongation of about 1.5 to about 4 MPa. In some embodiments, the piezoelectric composite energy harvester has a tensile stress at 45% elongation of about 2 to about 4.5 MPa. In some embodiments, the piezoelectric composite energy harvester has a tensile stress at 50% elongation of about 2 to about 4.5 MPa. In some embodiments, the piezoelectric layer has a thickness between about 5 μm and about 500 μm.

[0010] In some embodiments, the crosslinked elastomer may be formed from a reactive silicone oligomer having a hardness of 5 to 90 Shore A. In some embodiments, the fraction of reactive functional units in the reactive elastomer may be 5 mol % or more. In some embodiments, the elastomeric matrix may comprise a doped polyalkylsiloxane matrix and piezoelectric particles dispersed within the polyalkylsiloxane matrix. In some embodiments, the elastomeric matrix may comprise a reactive oligomer having reactive functional groups selected from hydroxyl groups, vinyl groups, alkoxy groups, and hydride groups. In some embodiments, the dopant may be platinum (Pt). In some embodiments, the polyalkylsiloxane may comprise polydimethylsiloxane. In some embodiments, the volume fraction of the piezoelectric particles in the piezoelectric layer may be 35 to 65%. In some embodiments, the crosslinked elastomer may comprise a volume fraction of silicone of 65% to 35%. In some embodiments, the elastic electrode may comprise carbon as a conductive element.

[0011] In some embodiments, a tire comprises the piezoelectric composite energy harvester described above.

[0012] In some embodiments, a method for preparing a piezoelectric composite harvesting composite includes providing a silicone oligomer having a hardness of about 5 to about 90 Shore A after curing, providing a mixture comprising piezoelectric particles dispersed within the silicone oligomer, casting the mixture to form a composite sheet, curing the composite sheet, poling the piezoelectric particles in the composite sheet, fabricating a first electrode from a conductive material, the conductive material being formed on a first side of the composite sheet, fabricating a second electrode from a conductive material, the conductive material being formed on a second side of the composite sheet, and fabricating an elastomeric cover layer from silicone, the silicone being formed on the first electrode or the second electrode.

[0013] In some embodiments, fabricating the first electrode and the second electrode may comprise forming the conductive material by a printing method, a casting method, and / or a coating method. In some embodiments, the printing method may comprise screen printing. In some embodiments, fabricating the elastic cover layer may comprise forming the conductive material by a printing method, a casting method, and / or a coating method. In some embodiments, the printing method may comprise screen printing.

[0014] These and other embodiments are described in further detail below. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an embodiment of a piezoelectric energy harvester. [Figure 2] FIG. 2 is a schematic diagram illustrating a sensor module that may be included in an embodiment of a piezoelectric energy harvester. [Figure 3] FIG. 3 is a schematic diagram of an exemplary energy generation circuit that may be included in embodiments described herein. [Figure 4] FIG. 4 is a graph illustrating tensile stress for an embodiment of a piezoelectric energy harvester. [Figure 5] FIG. 5 is a graph illustrating tensile stress for an embodiment of a piezoelectric energy harvester. [Figure 6] FIG. 6 is a graph illustrating tensile stress for an embodiment of a piezoelectric energy harvester. [Figure 7] FIG. 7 is a graph illustrating tensile stress for an embodiment of a piezoelectric energy harvester. [Figure 8] FIG. 8 is a graph illustrating tensile stress for an embodiment of a piezoelectric energy harvester. [Figure 9] FIG. 9 is a graph illustrating the piezoelectric energy generation of one embodiment of a piezoelectric energy harvester.

[0016] The present disclosure relates to a piezoelectric composite energy harvester. To facilitate understanding of the present disclosure, reference will be made to the following embodiments and specific descriptions will be used. However, this is not intended to limit the scope of the present disclosure, and various changes and further modifications to the subject matter described, as well as further applications of the principles described in the present disclosure, will be apparent to those skilled in the art to which the present disclosure pertains.

[0017] In some applications, piezoelectric sensors are provided with elastic protective layers to improve sensitivity. However, elastic protective layers placed in front of and behind the piezoelectric sensor degrade the functionality of the piezoelectric sensor. If the thickness of the elastic protective layer is less than twice that of the piezoelectric layer, the flexibility of the piezoelectric sensor decreases, and if the thickness of the elastic protective layer is more than 10 times that of the piezoelectric layer, the sensitivity of the sensor decreases. Furthermore, interposing an elastic protective layer between a piezoelectric energy harvester and a substrate, such as a non-planar surface, reduces the piezoelectric energy harvester's ability to efficiently generate power. In other applications, the protective layer reduces the piezoelectric sensor's exposure to mechanical stress, resulting in reduced power generation.

[0018] The present disclosure relates generally to piezoelectric power generating systems that can include a resilient protective cover layer that provides increased flexibility without sacrificing piezoelectricity, thereby enabling sufficient power generation and sufficient toughness for durability in conditions compatible with use inside a vehicle tire. This disclosure describes a piezoelectric energy harvester.

[0019] As shown in FIG. 1 , a piezoelectric energy harvester, such as piezoelectric energy harvester 100, may include a piezoelectric element, such as piezoelectric element 102, and an elastic cover layer, such as cover layer 110. In some embodiments, the piezoelectric energy harvester relies on mechanical stress, such as the simple rotation of a tire and / or the tire's natural vibrations, and converts this mechanical energy into electrical energy. In some embodiments, the piezoelectric energy harvester is flexible and can conform to uneven surfaces. In some embodiments, the piezoelectric energy harvester can conform to flat surfaces.

[0020] In some embodiments, the piezoelectric element may include a first electrode, such as electrode 104, a second electrode, such as electrode 106, and a piezoelectric layer, such as piezoelectric layer 108. In some embodiments, the first electrode may be disposed on a first side of the piezoelectric layer and the second electrode may be disposed on a second side of the piezoelectric layer.

[0021] In some embodiments, the piezoelectric layer may comprise an elastomeric matrix and piezoelectric particles. In some embodiments, the piezoelectric particles may be dispersed within the elastomeric matrix. In some embodiments, the elastomeric matrix may comprise a reactive oligomer and piezoelectric particles. In some embodiments, the elastomeric matrix may comprise a cross-linked silicone. In some embodiments, the piezoelectric particles may be polarized (i.e., the dipole moments of the piezoelectric particles may be aligned).

[0022] In some embodiments, each of the first electrode and the second electrode may comprise a flexible material or an elastomeric substrate. In some embodiments, the flexible material may comprise a conductive material, such as silicone. When the piezoelectric energy harvester is used in combination with a tire, silicone is softer than the tire and highly flexible, preventing the capture of mechanical stresses or vibrations from the tire. Non-limiting examples of silicones that can be used for the first electrode and the second electrode include LS-8941 (NuSil Technology, California) or Sylgard 182 (Dow Chemical, Michigan). In some embodiments, the conductive material may comprise nanoparticles, such as carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, or graphene oxide. The conductive particles of the first electrode and the second electrode may be uniformly distributed throughout the respective flexible material or elastomeric substrate and / or may be arranged in a hatched or mesh-like pattern or structure on or within the flexible material or elastomeric substrate.

[0023] 4-8 are graphs illustrating the effect of an elastic cover layer on the tensile stress of a piezoelectric energy harvester. Generally, the graphs demonstrate the unexpected result of improved tensile stress for the piezoelectric energy harvesters described herein. In some embodiments, the piezoelectric energy harvester may have a device tensile stress at 20% elongation of about 0.5 MPa to about 5 MPa, about 1.5-4 MPa, about 0.5-1 MPa, about 1.5-2 MPa, about 2-2.5 MPa, about 2.5-3 MPa, about 3-3.5 MPa, about 3.5-4 MPa, about 4-4.5 MPa, about 4.5-5 MPa, or about 0.5 MPa, about 1 MPa, about 1.5 MPa, about 2 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5 MPa, or within a range bounded by any of these values.

[0024] In some embodiments, the piezoelectric energy harvester may have a device tensile stress at 35% elongation of about 0.5 MPa to about 5 MPa, about 1.5 to 4 MPa, about 0.5 to 1 MPa, about 1.5 to 2 MPa, about 2 to 2.5 MPa, about 2.5 to 3 MPa, about 3 to 3.5 MPa, about 3.5 to 4 MPa, about 4 to 4.5 MPa, about 4.5 to 5 MPa, or about 0.5 MPa, about 1 MPa, about 1.5 MPa, about 2 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5 MPa, or within a range bounded by any of these values.

[0025] In some embodiments, the piezoelectric energy harvester may have a device tensile stress at 40% elongation of about 0.5 MPa to about 5 MPa, about 1.5 to 4 MPa, about 0.5 to 1 MPa, about 1.5 to 2 MPa, about 2 to 2.5 MPa, about 2.5 to 3 MPa, about 3 to 3.5 MPa, about 3.5 to 4 MPa, about 4 to 4.5 MPa, about 4.5 to 5 MPa, or about 0.5 MPa, about 1 MPa, about 1.5 MPa, about 2 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5 MPa, or a range bounded by any of these values.

[0026] In some embodiments, the piezoelectric energy harvester may have a device tensile stress at 45% elongation of about 0.5 MPa to about 6 MPa, about 1.5 to 4 MPa, about 0.5 to 1 MPa, about 1.5 to 2 MPa, about 2 to 2.5 MPa, about 2.5 to 3 MPa, about 3 to 3.5 MPa, about 3.5 to 4 MPa, about 4 to 4.5 MPa, about 4.5 to 5 MPa, about 5 to 5.5 MPa, about 5.5 to 6 MPa, or about 0.5 MPa, about 1 MPa, about 1.5 MPa, about 2 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5 MPa, about 5.5 MPa, about 6 MPa, or within a range bounded by any of these values. In some embodiments, the piezoelectric energy harvester may have a device tensile stress at 50% elongation of about 0.5 MPa to about 6 MPa, about 1.5 to 4 MPa, about 0.5 to 1 MPa, about 1.5 to 2 MPa, about 2 to 2.5 MPa, about 2.5 to 3 MPa, about 3 to 3.5 MPa, about 3.5 to 4 MPa, about 4 to 4.5 MPa, about 4.5 to 5 MPa, about 5 to 5.5 MPa, about 5.5 to 6 MPa, or about 0.5 MPa, about 1 MPa, about 1.5 MPa, about 2 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5 MPa, about 5.5 MPa, about 6 MPa, or within a range bounded by any of these values.

[0027] In some embodiments, the silicone used to form the crosslinked elastomeric matrix may have a hardness ranging from about 5 to about 90, as measured on the Shore Hardness Scale Type A (hereinafter referred to as Shore A). In some examples, the silicone used to form the crosslinked elastomeric matrix may comprise about 75% silicone, about 80% silicone, about 85% silicone, about 90% silicone, about 95% silicone, about 99% silicone, about 99.5% silicone, and / or about 99.9% silicone. In some embodiments, the silicone may be essentially pure silicone. Non-limiting examples of silicones that can be used in the piezoelectric layer include LS-8941 (NuSil Technology, California) or Sylgard 182 (Dow Chemical, Michigan). It is believed that the specific silicone polymer, dopant, and / or crosslinker can contribute to the balance of hardness, flexibility, and power generation due to the piezoelectric function of the piezoelectric material. Any suitable means for measuring hardness may be used, such as ASTM D2240 Type A (a hardened steel rod 1.1-1.4 mm in diameter with a 0.79 mm diameter 35° truncated cone, exerting a force of approximately 8.064 Newtons (N) with an applied mass of approximately 0.822 kg). Any suitable means for measuring the tensile strength of a material may be used, such as a tensile tester utilizing a stroke rate of 5 mm / min.

[0028] Some embodiments include a piezoelectric layer comprising a crosslinked elastomeric matrix. In some embodiments, the crosslinked elastomeric matrix may comprise a silicone elastomer. In other embodiments, the silicone elastomer may comprise a polyalkylsiloxane. In some embodiments, the polyalkylsiloxane may comprise polydimethylsiloxane (PDMS). The type of silicone crosslinking reaction is not limited to those catalyzed by noble metals and may include all other types of silicone crosslinking reactions. In some embodiments, the polyalkylsiloxane may be doped with a noble metal. In some embodiments, the dopant may comprise Ag, Au, Pd, Ni, Pt, or any combination thereof. It is believed that Pt may catalyze the crosslinking reaction. In some embodiments, the noble metal may be platinum (Pt). In some embodiments, the PDMS elastomer may be doped with a noble metal, such as Pt, at 0.001 wt% to about 5 wt%, about 0.001-0.05 wt%, about 0.05-0.1 wt%, about 0.1-0.5 wt%, about 0.5-1 wt%, about 1-1.5 wt%, about 1.5-2 wt%, about 2-2.5 wt%, about 2.5-3 wt%, about 3-3.5 wt%, about 3.5-4 wt%, about 4-4.5 wt%, or about 4.5-5 wt%, or within a range bounded by any of these values. Doping of the silicone elastomer is believed to contribute to the curing of the elastomer, such as by contributing to achieving hardness levels of 5-90 Shore A. In some embodiments, the presence of a dopant may affect the catalytic crosslinking of the metal, for example, as described above.

[0029] In some embodiments, the crosslinked elastomeric matrix may comprise a reactive silicone oligomer. In some embodiments, the reactive oligomer may comprise a reactive functionalized silicone monomer. In some embodiments, the reactive functionalized silicone monomer may comprise a reactive hydrogen group (silicone hydride), a reactive vinyl group, a reactive hydroxyl group, or a reactive alkoxy group. In some embodiments, the reactive elastomer may comprise a silicone hydride (a silicone-reactive functional group) and / or a polysilicone vinyl (another silicone-reactive functional group). In some embodiments, the fraction of reactive functional units in the reactive elastomer, i.e., the ratio of the number of reactive monomeric units to the total number of monomeric units, may be 5 mol% or greater (e.g., one silicone hydride-containing silicone monomer combined with 19 non-reactive silicone monomers yields a reactive functional unit fraction of 5 mol%). In some embodiments, the fraction of reactive functional units in the reactive elastomer may be 6% or greater. In some embodiments, the fraction of reactive functional units in the reactive elastomer may be 7.5 mol% or greater.

[0030] In some embodiments, the piezoelectric energy harvester may comprise piezoelectric particles dispersed or disposed within a crosslinked silicone elastomer matrix. In some embodiments, the volume fraction of the piezoelectric particles in the piezoelectric layer may be between about 35% and about 65%. In some embodiments, a volume fraction of the piezoelectric particles in the piezoelectric layer of between about 40% and about 65% may improve power generation. In some embodiments, a volume fraction of the piezoelectric particles in the piezoelectric layer of between about 40% and about 55% may improve toughness. In some embodiments, the first elastic electrode and / or the second elastic electrode may comprise carbon as a conductive filler element. The conductive filler may be dispersed within the elastomer matrix. A conductive filler is a compound introduced into a medium to generate a current in the medium in the presence of an electric current. The conductive filler may be graphitized or partially graphitized carbon black, also known as conductive black. These conductive blacks have, for example, a specific surface area (BET, measured according to standard ASTM D3037) of 770 m 2 / g, or Timcal's "Ensaco 350G" with a specific surface area of ​​70 m 2 In some embodiments, the conductive filler may be "Ensaco 260G" having a 65 m 2 / g or greater than 100m 2 / g and / or 500m 2The conductive filler may be a conductive or graphitized carbon black having a specific surface area (BET, measured according to standard ASTM D3037) greater than 1 / g. In some embodiments, the amount of conductive filler in the elastomeric matrix composition may be in the range of about 35% to about 65% by volume. Suitable examples of conductive black include, but are not limited to, Timcal's "Ensaco 260G" or Timcal's conductive carbon black "Ensaco 350G." The size of the conductive filler preferably ranges from about 50 nm (nanometers) to about 500 μm (microns or micrometers). In some embodiments, the piezoelectric material may have a dipole moment that is aligned by an external electric field. In some embodiments, the volume fraction of the piezoelectric particles may be about 40% to about 65%.

[0031] In some embodiments, the piezoelectric energy harvester may include a resilient cover layer, such as cover layer 110 shown in FIG. 1 . In some embodiments, the resilient cover layer may be contiguous with the second electrode. In some embodiments, the resilient cover layer may be contiguous with the first electrode. In some embodiments, the resilient cover layer is disposed over the exterior of the piezoelectric element. In some embodiments, the resilient cover layer is disposed over the exterior of the second electrode. In some embodiments, the exterior of the piezoelectric element may comprise the outer top surface of the second electrode. In some embodiments, the exterior of the piezoelectric element may comprise the outer top surface of the first electrode. In some embodiments, the exterior of the piezoelectric element is partially covered by the resilient cover layer. In some embodiments, the resilient cover layer covers about 70% to about 100%, about 100%, about 99.999%, about 99.99%, about 99.9%, about 99%, about 98%, about 97%, about 96%, about 95%, about 90%, about 85%, about 80%, about 75%, about 70%, or any percentage within a range bounded by any of these values ​​of the exterior of the piezoelectric element. In some embodiments, the resilient cover layer does not extend to the sides of the piezoelectric composite energy harvester. In some embodiments, the resilient cover layer does not contact the substrate or the tire.

[0032] Covering or partially covering the outer top side of the piezoelectric element with an elastic cover layer, but not sealing or insulating the piezoelectric element, is believed to improve flexibility and durability without limiting the piezoelectric element's exposure to mechanical stress, improving flexibility without sacrificing piezoelectric energy generation. For example, Figure 9 is a graph showing the effect of an elastic cover layer on a piezoelectric element. Generally, this graph shows the unexpected result that the piezoelectric energy harvester maintains piezoelectric energy generation even as the thickness of the elastic cover layer increases.

[0033] In some embodiments, the elastic cover layer may comprise silicone. In some embodiments, the silicone used to form the elastic cover layer may comprise about 75% silicone, about 80% silicone, about 85% silicone, about 90% silicone, about 95% silicone, about 99% silicone, about 99.5% silicone, and / or about 99.9% silicone. In some embodiments, the silicone may be essentially pure silicone. Any suitable silicone may be used in the elastic cover layer, including, but not limited to, LS-8941 (NuSil Technology, California), R-2188 (NuSil Technology, California), or Sylgard 182 (Dow Chemical, Michigan).

[0034] In some embodiments, the elastic modulus of the elastic cover layer is less than the elastic modulus of the piezoelectric element. In some embodiments, the elastic modulus of the elastic cover layer is less than the elastic modulus of the piezoelectric layer. In some embodiments, the elastic cover layer has a tensile stress at 1% elongation of about 0.01 to about 5 MPa. In some embodiments, the piezoelectric element has a tensile stress at 1% elongation of about 0.5 to about 5 MPa.

[0035] In some embodiments, the piezoelectric layer has a thickness of about 5 μm to about 500 μm, about 5 μm to 50 μm, about 50 μm to 100 μm, about 100 μm to 150 μm, about 150 μm to 200 μm, about 200 μm to 250 μm, about 250 μm to 300 μm, about 300 μm to 350 μm, about 300 μm to 450 μm, about 350 μm to 400 μm, about 400 μm to 450 μm, about 450 μm to 500 μm, or any thickness within a range bounded by any of these values.

[0036] In some embodiments, the piezoelectric energy harvester has a thickness of about 5 μm to about 5 mm, about 5 μm to 50 μm, about 50 μm to 100 μm, about 100 μm to 150 μm, about 150 μm to 200 μm, about 200 μm to 250 μm, about 250 μm to 300 μm, about 300 μm to 350 μm, about 300 μm to 450 μm, about 350 μm to 400 μm, about 400 μm to 450 μm, about 450 to 500 μm, about 500 μm to about 1 mm, about 1 mm to 2 mm, about 2 mm to 3 mm, about 3 mm to 4 mm, about 4 mm to 5 mm, or any thickness within a range bounded by any of these values.

[0037] In some embodiments, the piezoelectric energy harvester may comprise a mounting surface. The mounting surface may be configured to be attached to the surface of a tire or other object or substrate. Alternatively, or in addition, the mounting surface may include an adhesive thereon for adhering the piezoelectric energy harvester to a desired location within a cavity (e.g., cavity 120 as shown in FIG. 1 ) or outside of an inner tube of the tire (or other substrate). The adhesive may comprise a thermoplastic adhesive or any other suitable adhesive.

[0038] In some embodiments, the piezoelectric energy harvester may be exposed to mechanical stress or multi-directional forces, such as roll (Z-axis), pitch (Y-axis), and / or yaw (X-axis) forces. In some embodiments, the piezoelectric energy harvester is configured to bend, expand, contract, rotate, tilt, and / or move in any spatial direction upon exposure to mechanical stress. In some embodiments, the piezoelectric elements are configured to bend, expand, contract, rotate, tilt, and / or move in any spatial direction upon exposure to mechanical stress. In some embodiments, the elastic cover layer covers only the outside of the piezoelectric elements and does not extend down to the tire (or other substrate), allowing the piezoelectric elements to bend, expand, contract, rotate, tilt, and / or move in any spatial direction. This configuration is believed to increase the piezoelectric elements' exposure to mechanical stress because only the outside of the piezoelectric elements is covered or partially covered by the elastic cover layer, resulting in increased piezoelectric energy generation while providing greater flexibility.

[0039] In some embodiments, a tire of a vehicle (such as an automobile, truck, or tractor) may include the piezoelectric energy harvester described above. In some embodiments, the piezoelectric energy harvester may include a plurality of piezoelectric elements selectively positioned at desired locations on the tire. In some embodiments, the piezoelectric energy harvester may be positioned in a tread portion, a shoulder portion, and / or a sidewall portion of the tire. In some embodiments, the tire may be a tubeless tire and may have a tire carcass with an inner surface that forms an airtight seal with the wheel and defines a reservoir for receiving a gas, typically air, therein. The tire carcass may have tire beads that interact with the wheel to form an airtight seal. In some embodiments, the tire is used with an inner tube disposed within the reservoir to hold a gas, such as air, but in this case the tire does not need to form an airtight seal with the wheel. The tire carcass may include a tread portion, a shoulder portion, and a sidewall portion.

[0040] The piezoelectric energy harvesters described herein are useful in combination with the capacitive tire sensors described in Patent Cooperation Treaty Application WO 2021 / 0168286, filed February 19, 2021, and published August 26, 2021, which is incorporated herein for its description of tire sensors and piezoelectric generators. As shown in FIG. 2 , a sensor module, such as sensor module 200, may generally include a detector patch, such as detector patch 202, an electronic unit, such as electronic unit 204, and, optionally, a power source, such as power source 206. In some embodiments, the piezoelectric energy harvester 100 of FIG. 1 is suitable as a power source. In some examples, the piezoelectric harvester may include an electronic unit and a power source connected to the detector patch. In some embodiments, the power source may include a piezoelectric energy harvester system described herein.

[0041] The detector patch may include a mounting surface, such as mounting surface 208, and one or more sensor regions, such as sensor region 210. The mounting surface may be configured to be attached to the surface of a tire or other object and / or may include the underside or bottom surface of the detection patch. Alternatively, or in addition, the mounting surface may include an adhesive, such as adhesive 212, disposed thereon to adhere the detector patch to a desired location within the tire cavity of the tire or outside the inner tube. The adhesive may include a thermoplastic adhesive or any other suitable adhesive. The sensor region may generally include a capacitor. In some embodiments, the capacitor and / or sensor region may be flexible, stretchable, expandable, deformable, layered, and / or lamellar. Alternatively, or in addition, the sensor region may be at least partially covered, bonded to, and / or surrounded by one or more protective layers, such as protective layer 214, as part of the detector patch. The protective layer may include an elastomeric material, such as silicone. The power source may include a battery, an energy generation circuit, an energy harvesting system (EHS) module, a dielectric elastomer power generating material, a piezoelectric harvester as described herein, and / or a receiving coil and circuit of an inductive charging unit. The electronic unit may be in electrical communication with each of the detector patch and the power source via one or more corresponding electrical connectors, such as connector 216. Alternatively, or in addition, the electronic unit and the power source may be mechanically coupled by epoxy and / or disposed within an encapsulant, such as a housing or encapsulant, that is mechanically coupled to the detector patch.

[0042] In some embodiments, a capacitive tire sensor may include an energy generation circuit and / or element. As shown in FIG. 3 , an energy generation circuit, such as energy generation circuit 300, may include an energy generation element, such as energy generation element 302, an EHS module, such as EHS module 304, an energy storage circuit, such as energy storage circuit 306, and / or a battery, such as battery 308. In some embodiments, the piezoelectric energy harvester 100 of FIG. 1 is suitable as the energy generation element. The EHS module may be electrically coupled to the energy generation element, the energy storage circuit, and / or the battery. In some embodiments, the energy generation element may include a dielectric power generation material, a piezoelectric power generation material, or other material, system, or device, or combination thereof, that generates electricity in response to movement, mechanical stress, or other input. In some embodiments, the energy generation element may be a piezoelectric energy harvester as described herein. In some embodiments, for example, bending of an energy generation element implemented as a piezoelectric energy harvester as described herein and / or a portion of a detector patch having such a material may generate an electric charge on the surface of the energy generation element. In some embodiments, the energy-generating elements may be positioned proximate the tread, shoulder, and / or sidewall portions of the tire.

[0043] In some embodiments, a method for preparing a piezoelectric composite energy harvester may include providing a silicone oligomer having a hardness of about 5 to about 90 Shore A after curing; providing a mixture comprising the silicone oligomer and piezoelectric particles dispersed within the silicone oligomer; casting the mixture to form a composite sheet; curing the composite sheet; polarizing the piezoelectric particles in the composite sheet; fabricating a first electrode from a conductive material, the fabrication comprising forming the conductive material on a first side of the composite sheet; fabricating a second electrode from a conductive material, the fabrication comprising forming the conductive material on a second side of the composite sheet; and fabricating an elastomeric cover layer from silicone, the fabrication comprising forming the silicone on the first electrode or the second electrode.

[0044] In some embodiments, fabricating the first electrode and the second electrode may comprise forming the conductive material by a printing method, a casting method, and / or a coating method. In some embodiments, the printing method may comprise screen printing. In some embodiments, fabricating the elastic cover layer may comprise forming the conductive material by a printing method, a casting method, and / or a coating method. In some embodiments, the printing method may comprise screen printing.

[0045] In some embodiments, the step of fabricating the elastomeric cover layer from silicone may further comprise mixing the silicone with a solvent. In some embodiments, the solvent may comprise toluene.

[0046] The embodiments and methods are described in more detail below.

[0047] Embodiment 1. A piezoelectric composite energy harvester comprising: a piezoelectric element comprising a first electrode, a second electrode, and a piezoelectric layer comprising a cross-linked silicone elastomer matrix and piezoelectric particles dispersed in the cross-linked silicone elastomer matrix, the first electrode disposed on a first side of the piezoelectric layer and the second electrode disposed on a second side of the piezoelectric layer; an elastic cover layer continuous with the second electrode, the elastic cover layer being arranged to cover the outside of the second electrode, and the elastic modulus of the elastic cover layer being lower than the elastic modulus of the piezoelectric element; Equipped with A piezoelectric composite energy harvester, wherein the piezoelectric composite energy harvester is configured to bend, expand, contract, rotate, tilt, and / or move in any spatial direction.

[0048] Embodiment 2. The piezoelectric composite energy harvester of embodiment 1, wherein the thickness ratio of the elastic cover layer to the piezoelectric element is about 0.01 or greater.

[0049] Embodiment 3. The piezoelectric composite energy harvester of embodiment 1, wherein the thickness ratio of the elastomeric cover layer to the piezoelectric element is greater than about 0.01 and less than about 2.

[0050] Embodiment 4. The piezoelectric composite energy harvester of embodiment 1, wherein the tensile stress of the piezoelectric composite energy harvester at 20% elongation is about 1.5 MPa to about 4 MPa.

[0051] Embodiment 5. The piezoelectric composite energy harvester of embodiment 1, wherein the tensile stress of the piezoelectric composite energy harvester at 35% elongation is about 1.5 MPa to about 4 MPa.

[0052] Embodiment 6. The piezoelectric composite energy harvester of embodiment 1, wherein the tensile stress of the piezoelectric composite energy harvester at 40% elongation is about 1.5 MPa to about 4 MPa.

[0053] Embodiment 7. The piezoelectric composite energy harvester of embodiment 1, wherein the tensile stress of the piezoelectric composite energy harvester at 45% elongation is about 2 MPa to about 4.5 MPa.

[0054] Embodiment 8. The piezoelectric composite energy harvester of embodiment 1, wherein the tensile stress of the piezoelectric composite energy harvester at 50% elongation is about 2 MPa to about 4.5 MPa.

[0055] Embodiment 9. The piezoelectric composite energy harvester of embodiment 1, wherein the piezoelectric layer has a thickness between about 5 μm and about 500 μm.

[0056] Embodiment 10. The piezoelectric composite energy harvester of embodiment 1, wherein the elastic cover layer comprises silicone.

[0057] Embodiment 11. The piezoelectric composite energy harvester of embodiment 1, wherein the first electrode and the second electrode comprise a conductive material and silicone.

[0058] Embodiment 12. The piezoelectric composite energy harvester of embodiment 11, wherein the conductive material comprises conductive particles comprising carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, and / or graphene oxide.

[0059] Embodiment 13. A tire equipped with the piezoelectric composite energy harvester of any one of embodiments 1 to 12.

[0060] Embodiment 14. A method for manufacturing the piezoelectric composite energy harvester of any one of embodiments 1 to 12, comprising: providing a silicone oligomer having a hardness of from about 5 Shore A to about 90 Shore A after curing; providing a mixture comprising the piezoelectric particles and the silicone oligomer, wherein the piezoelectric particles are dispersed within the silicone oligomer; the mixture is cast to form a composite sheet; The composite sheet is cured, polarizing the piezoelectric particles in the composite sheet; fabricating a first electrode from a conductive material, the fabrication comprising forming the conductive material on a first side of the composite sheet; fabricating a second electrode from a conductive material, the fabrication comprising forming the conductive material on a second side of the composite sheet; fabricating an elastic cover layer from silicone, the fabrication comprising forming the silicone on the first electrode or the second electrode; Prepare for this. Manufacturing method.

[0061] Embodiment 15. The method of embodiment 14, wherein the step of fabricating the first electrode and the second electrode comprises forming the conductive material by a printing method, a casting method, and / or a coating method.

[0062] Embodiment 16. The method of embodiment 15, wherein the printing method comprises screen printing.

[0063] Embodiment 17. The method of embodiment 14, wherein the step of forming the elastic cover layer comprises forming the conductive material by a printing method, a casting method, and / or a coating method.

[0064] Embodiment 18. The method of embodiment 17, wherein the printing method comprises a screen printing method. [Example]

[0065] It should be understood that the following examples are for illustrative purposes and are not intended to be construed as limiting the subject matter disclosed herein to only the embodiments disclosed in these examples.

[0066] <Preparation of composite material> Example 1 An electrode ink consisting of a homogeneous mixture of 60.5 g of polydimethylsiloxane (PDMS), 6.3 g of carbon black, and 131.7 g of toluene, prepared by the method described in Sci Rep 9,1 (2019), was applied to a fluoropolymer substrate and then heat-treated in an oven at 80°C for 15 minutes and then at 200°C for 15 minutes to form a thin elastic electrode layer.

[0067] 14 g of piezoelectric (PZT) particles, 2 g of polydimethylsiloxane (PDMS) with a Shore A hardness of 80 and 9.4 mol% reactive units, and 2.8 g of toluene were mixed in a planetary centrifugal mixer for 4 minutes to obtain a uniform slurry. The slurry was then applied to the elastic electrode layer using a film applicator to a thickness of 24 mils. The applied film was then heated in an oven at 80°C for 15 minutes to remove the solvent, and then heated at 200°C for 30 minutes to complete the crosslinking reaction. A composite film was obtained.

[0068] The same electrode ink was applied to the composite film, which was then heat-treated in an oven at 80°C for 15 minutes and then at 200°C for 15 minutes to create a second thin, elastic electrode layer. A three-layer composite structure was obtained.

[0069] The composite structure was then sandwiched between two copper plates on a hot plate set at 130°C. A voltage of 6.0 kV was applied to one of the copper plates, generating an electric field across the composite structure, polarizing the PZT particles dispersed within for 60 minutes. A polarized composite sample was obtained.

[0070] Example 2 Example 2 was prepared in the same manner as Example 1, except that an elastic cover layer was added. An elastic cover layer ink consisting of a homogeneous mixture of 4 g of polydimethylsiloxane (PMDS) with a Shore A hardness of 80 and 9.4 mol% reactive units and 0.4 g of toluene was applied onto the polarized composite structure, followed by heat treatment in an oven at 80°C for 15 minutes and then at 150°C for 20 minutes to obtain the elastic cover layer.

[0071] <Measurement of stress at 1% elongation> 1 x 3 cm from the composite sample 2 A test piece of 1 × 1 cm was cut out from the center of the test piece. 2 The test piece was attached to an AGS-X tensile testing machine (Shimadzu Corporation, Japan) and the central part of the test piece was cut into 1 × 1 cm 2 The specimen was stretched at a stroke rate of 5 mm / min. The stress value at 1% elongation (0.1 mm) was recorded.

[0072] <Measurement of power generation> The composite specimen was fixed to an ACT165DL linear actuator (Aerotech, Pittsburgh, PA). Its elastic electrodes were connected to an oscilloscope with a load resistance R of 1 MΩ. The specimen was subjected to a 3% tensile deformation at a frequency of 20 Hz. The generated power was V rms 2 Calculated using / R.

[0073] <Sample tracking> A 10x10cm patch was placed on the inner liner of a tire whose surface had been polished smooth. 2 The samples were laminated together. If there were no wrinkles, lifting, or cracks, the conformability of the sample was judged to be good. On the other hand, if there were wrinkles, partial lifting, or cracks, the conformability was judged to be poor.

[0074] [Table 1]

[0075] The results in Table 1 above demonstrate the advantage that an improved piezoelectric harvester according to the present disclosure can provide both desirable levels of compliance and power generation at 3% tensile deformation when the piezoelectric generator is configured as described herein.

[0076] Use of the terms "may" or "may be" should be interpreted as shorthand for "is" or "is not," or alternatively "does" or "does not," or "will" or "will not," etc. For example, the statement "The thermally conductive composite may further comprise a backing layer" should be interpreted as "In some embodiments, the thermally conductive composite further comprises a backing layer," or "In some embodiments, the thermally conductive composite does not further comprise a backing layer."

[0077] Unless otherwise indicated, all numerical values ​​expressing quantities of ingredients, properties such as molecular weight, reaction conditions, etc. used in the specification and embodiments are understood to be modified in all instances by the term "about." As used herein, the term "about" can include any numerical value that can be varied without changing the basic function of that value. When used in conjunction with a range, "about" also discloses the range defined by the absolute values ​​of the two endpoints. The term "about" can refer to plus or minus 10% of the indicated numerical value.

[0078] Accordingly, unless otherwise indicated, the numerical parameters set forth in the specification and accompanying embodiments are approximations that may vary depending upon the desired properties sought to be obtained, and at least not as intended by the limiting application of the doctrine of equivalents. Within the scope of the embodiments, each numerical parameter should be construed in light of, at least, the number of reported significant digits and by applying standard rounding techniques.

[0079] The functions performed in the disclosed processes and / or methods may be performed in differing order, as may be indicated by the context. Furthermore, the outlined steps and operations are provided by way of example only, and some of the steps and operations may be optional, combined with fewer steps and operations, or expanded into additional steps and operations.

[0080] In this disclosure, different components may be illustrated as being included in or connected to different other components. Such illustrated configurations are merely examples, and many other configurations may be implemented that achieve the same or similar functionality.

[0081] The terms used in this disclosure and the accompanying embodiments are essentially intended to be "open-ended" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "including, but not limited to," etc.). Furthermore, when a specific number of elements is stated, it can be interpreted as including more than that number, as may be indicated by the context (e.g., when simply stating "two elements" without any modifiers, it includes at least two, or two or more elements). Furthermore, when any alternative words and / or groups of words used in this disclosure indicate two or more alternative items, they should be interpreted as possibly including either one of the terms, either of the terms, or both terms. For example, the expression "A or B" should be interpreted as including all of "A," "B," and "A and B."

[0082] The terms and words used are not limited to their bibliographical meanings, but are used simply to enable a clear and consistent understanding of the present disclosure. The terms "a," "an," "the," and similar reference words used in the context of describing the present disclosure (particularly in the context of the following embodiments) are to be construed as covering both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of any examples or representative language (e.g., "etc.") provided herein is intended merely to better explain the present disclosure and does not limit the scope of any embodiment. No language in the specification should be construed as indicating that any element not present in an embodiment is essential to the practice of the disclosure.

[0083] Group arrangements of alternative components or embodiments disclosed herein are not to be construed as limiting. Each group element may be referenced and practiced alone or in any combination with other elements of the group or other elements disclosed herein. It is contemplated that one or more elements of a group may be added to or deleted from a group for reasons of convenience and / or patentability. When such additions or deletions are made, the specification shall be deemed to include the modified group and satisfy the written description requirements of all Markush forms used in the accompanying embodiments.

[0084] Certain embodiments have been described herein, including the best mode contemplated by the inventors for carrying out the present disclosure. Of course, variations on these described embodiments will be apparent to those skilled in the art upon reading the foregoing description. The inventors expect that those skilled in the art will adopt such variations as appropriate, and the inventors intend for the present disclosure to be practiced otherwise than as specifically described herein. Accordingly, these embodiments are intended to include all modifications and equivalents of the subject matter described in the embodiments to the extent permitted by applicable law. Furthermore, any combination of the above-described elements, including all possible variations thereof, is construed as being within the scope of the invention unless otherwise stated herein or otherwise clearly contradicted by context. Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments. Other variations that may be employed are within the scope of the embodiments. Thus, by way of example, and not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the embodiments are not limited to only those shown and described.

[0085] The term "substantially" means that the described characteristics, parameters, or numerical values ​​need not be achieved exactly, but that variations and deviations, including tolerances, measurement errors, limits of measurement accuracy, and other factors known to those skilled in the art, may occur to the extent that they do not interfere with the intended effects of the characteristics.

[0086] Each aspect of the present disclosure may be embodied in other forms without departing from its spirit or essential characteristics. The described aspects are illustrative in all respects and should not be construed as limiting. The subject matter of the present disclosure is defined by the accompanying embodiments, not by the foregoing description, and all changes within the meaning and range of equivalence of the embodiments are intended to be embraced within their scope.

Claims

1. 1. A piezoelectric composite energy harvester comprising: a piezoelectric element comprising a piezoelectric layer disposed between a first electrode and a second electrode, the piezoelectric layer comprising piezoelectric particles dispersed in a crosslinked silicone elastomer matrix; an elastic cover layer continuous with the second electrode, the elastic cover layer being disposed so as to cover the outside of the second electrode, and the elastic modulus of the elastic cover layer being lower than the elastic modulus of the piezoelectric element; Equipped with the piezoelectric composite energy harvester is configured to bend, expand, contract, rotate, tilt, or move in any spatial direction; Piezoelectric composite energy harvester.

2. 10. The piezoelectric composite energy harvester of claim 1, wherein the thickness ratio of the elastomeric cover layer to the piezoelectric element is greater than or equal to about 0.

01.

3. 10. The piezoelectric composite energy harvester of claim 1, wherein a thickness ratio of the elastomeric cover layer to the piezoelectric element is greater than about 0.01 and less than about 2.

4. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric composite energy harvester has a tensile stress at 20% elongation of about 1.5 MPa to about 4 MPa.

5. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric composite energy harvester has a tensile stress at 35% elongation of about 1.5 MPa to about 4 MPa.

6. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric composite energy harvester has a tensile stress at 40% elongation of about 1.5 MPa to about 4 MPa.

7. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric composite energy harvester has a tensile stress at 45% elongation of about 2 MPa to about 4.5 MPa.

8. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric composite energy harvester has a tensile stress at 50% elongation of about 2 MPa to about 4.5 MPa.

9. 10. The piezoelectric composite energy harvester of claim 1, wherein the piezoelectric layer has a thickness between about 5 μm and about 500 μm.

10. The piezoelectric composite energy harvester of claim 1 , wherein the resilient cover layer comprises silicone.

11. The piezoelectric composite energy harvester of claim 1 , wherein the first electrode and the second electrode comprise a conductive material and silicone.

12. 12. The piezoelectric composite energy harvester of claim 11, wherein the conductive material comprises conductive particles comprising carbon black, nickel nanostrands, silver nanoparticles, graphene nanoplatelets, graphene oxide, or combinations thereof.

13. A capacitive tire sensor comprising a sensor module, The sensor module is a capacitive tire sensor equipped with a power source.

14. A capacitive tire sensor according to claim 13, wherein the power source comprises a piezoelectric composite energy harvester according to any one of claims 1 to 12.

15. the capacitive tire sensor further comprises an energy generation circuit electrically coupled to the power source; The energy generating circuit comprises a piezoelectric composite energy harvester according to any one of claims 1 to 12.

14. The capacitance type tire sensor of claim 13.

16. A method for manufacturing a piezoelectric composite energy harvester according to any one of claims 1 to 12, comprising the steps of: mixing the mixture of piezoelectric particles with the silicone oligomer such that the piezoelectric particles are dispersed within the silicone oligomer; casting the mixture to form a composite sheet; curing the composite sheet so that the silicone oligomer has a hardness of from about 5 Shore A to about 90 Shore A after curing; polarizing the piezoelectric particles in the composite sheet; fabricating a first electrode from a conductive material, the fabrication comprising forming the conductive material on a first side of the composite sheet; fabricating a second electrode from a conductive material, the fabrication comprising forming the conductive material on a second side of the composite sheet; fabricating an elastic cover layer from silicone, the fabrication comprising forming the silicone on the first electrode or the second electrode; Prepare for this. Manufacturing method.

17. 17. The method of claim 16, wherein fabricating the first electrode and the second electrode comprises forming the conductive material by printing, casting, coating, or a combination thereof.

18. The method of claim 17 , wherein the printing method comprises screen printing.

19. 17. The method of claim 16, wherein the step of creating the resilient cover layer comprises forming the conductive material by printing, casting, painting, or a combination thereof.

20. The method of claim 19 , wherein the printing method comprises a screen printing method.

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