A stretchable oriented porous array piezoelectric ceramic sensor and preparation and application thereof

Abstract

The application belongs to the field of piezoelectric ceramic devices, and particularly relates to a stretchable orientation porous array type piezoelectric ceramic sensor, characterized in that the sensor comprises a bottom film, a ceramic array layer arranged on the bottom film, and a composite packaging material for packaging and compounding the ceramic array layer on the bottom film; the composite packaging material comprises PDMS Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1-2:1-2; the ceramic array layer comprises a plurality of polarized ceramic particles with oriented holes and sputtered with conductive metal at both ends, and each ceramic particle is conductively connected along the polarization direction through the conductive material arranged on the surface of the bottom film. The application further comprises a preparation method of the sensor and application thereof. The process can realize synergy and unexpectedly obtain excellent synergistic effect.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramics technology, and more specifically to the field of stretchable oriented porous array piezoelectric ceramic sensors. Background Technology

[0002] Stretchable, self-powered sensors offer flexibility, comfort, and energy autonomy that are difficult to achieve with traditional rigid sensors, and have shown great potential in various deformable electronic products, such as electronic skin, wearable smart devices, implantable devices, and human-computer interaction systems. Among them, stretchable sensors based on the piezoelectric effect have attracted much attention because they can convert minute body movements into electrical signals, thereby enabling long-term, continuous, and sensitive monitoring of physiological information.

[0003] Incorporating piezoelectric ceramic powder into an elastic polymer matrix to combine the high electromechanical coupling properties of ceramics with the flexibility of polymers is a common strategy for developing stretchable piezoelectric sensors. However, this strategy still faces several significant challenges. First, the large difference in dielectric constant between ceramic particles and the polymer matrix leads to unfavorable electric field distribution, making it difficult to effectively polarize the ceramic powder. Second, the modulus mismatch between ceramic and polymer results in poor interfacial adhesion in the composite structure, which hinders stress transfer and reduces durability. Third, the lack of connectivity between randomly dispersed piezoelectric particles hinders charge transport and significantly reduces electrical performance. As a key functional component of piezoelectric energy devices, the most common flexibility strategy for piezoelectric ceramic matrix composites is to combine piezoelectric ceramics with organic polymers. However, compared to pure ceramics, this approach reduces the overall piezoelectric performance of the device, resulting in lower output voltage and current. Therefore, structural design of piezoelectric materials that maintains high stretchability while achieving high piezoelectric output performance is of great importance. Summary of the Invention

[0004] To address the problems of poor durability and unsatisfactory piezoelectric output performance of existing stretchable piezoelectric sensors, the primary objective of this invention is to provide a stretchable oriented multi-hole array piezoelectric sensor, which aims to provide a piezoelectric ceramic sensor that balances stretchability with high voltage and current output capabilities and stretching output stability.

[0005] The second objective of this invention is to provide a method for fabricating the stretchable oriented porous array piezoelectric ceramic sensor, aiming to prepare the piezoelectric ceramic power generation device that combines excellent flexibility and high voltage output capability.

[0006] The third objective of this invention is to provide the application of the stretchable oriented porous array piezoelectric ceramic sensor in fields requiring stretch sensing, such as healthcare.

[0007] To address the problems in current development strategies for stretchable piezoelectric sensors based on nanoparticle-incorporated elastic polymer matrices, such as poor interfacial adhesion, unsatisfactory stretchability, difficulty in discharging generated piezoelectric charges, and increased susceptibility to interfacial debonding, making it difficult to achieve devices that balance stretchability and high piezoelectric performance, this invention provides the following solution:

[0008] A stretchable oriented porous array piezoelectric ceramic sensor includes a base film, a ceramic array layer disposed on the base film, and a composite encapsulation material for encapsulating the ceramic array layer and bonding it to the base film; the composite encapsulation material includes PDMS Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1-2:1-2.

[0009] The ceramic array layer includes a plurality of polarized ceramic particles with orientation holes and conductive metal sputtered at both ends, and each ceramic particle is electrically connected along the polarization direction by a conductive material disposed on the surface of the base film.

[0010] To address the significant difference in Young's modulus between oriented porous ceramics and polymers, and the difficulty for common flexible polymers to simultaneously achieve high tensile strength and strong ceramic viscosity, this invention innovatively employs an array of oriented porous ceramic particles, combined with sputtered conductive metal and the aforementioned special composite encapsulation material. This synergistic effect unexpectedly achieves a better interface compatibility between ceramic materials and organic materials based on a mechanical interlocking mechanism, thereby endowing the device with excellent stretchability. Furthermore, it also helps to improve its output performance.

[0011] In this invention, the combination of the orientation holes of the ceramic particles, the conductive metal constructed by sputtering, and the composite packaging material with special type and proportion control is the key to synergistically solving the problems of difficult interface and composite due to the mismatch of modulus between organic and ceramic materials, as well as the unsatisfactory output effect.

[0012] In this invention, the ceramic particles can be made of conventional piezoelectric ceramic materials, such as at least one of barium zirconate titanate, lead zirconate titanate, barium titanate, and potassium sodium niobate; preferably at least one of PZT-5A, PZT-5H, BCZT, and BTO.

[0013] In this invention, the porosity of the ceramic particles is 30-65%, and more preferably 50-60%.

[0014] In this invention, the orientation holes of the ceramic particles can be exposed on their upper surface. Furthermore, the angle between the orientation hole direction of the ceramic particles and the plane direction of the bottom film is between 70° and 120°, preferably between 80° and 100°.

[0015] In this invention, the ceramic particles can be small ceramic blocks of any shape, for example, their cross-section can be square, rectangular, circular or elliptical. For ease of processing, they can be conventional ceramic blocks such as cubes, cuboids, spheres, hemispheres, etc.

[0016] In this invention, the size of the ceramic particles can be adjusted according to the final application scenario of the device. For example, the height of the ceramic particles is 1 to 10 mm, and more preferably 1 to 5 mm.

[0017] The size of the contact surface between the ceramic particles and the substrate can be, for example, 1 to 10 mm, more preferably 1 to 5 mm;

[0018] In this invention, the number of ceramic particles in the ceramic array layer can be controlled according to the application scenario and sensing requirements of the device. For example, it can be more than 2, and further, it can be 5 to 30.

[0019] In this invention, there are no special requirements for the arrangement of the ceramic array. Considering the ease of preparation, it can be arranged in a rectangular array. In order to make the isopolarized ends of each ceramic particle conductively connected, the conductive material can be laid in a serpentine manner.

[0020] In this invention, there are no particular requirements on the number of ceramic particles arranged longitudinally and laterally in the rectangular ceramic array. For example, the number of ceramic particles arranged laterally can be 2 to 5, and the number of ceramic particles arranged longitudinally can be 3 to 10. The longitudinal and transverse spacing between each ceramic particle can be adjusted as needed, for example, it can be 0.5 to 5 mm, further can be 1 to 4 mm, and further can be 1 to 3 mm.

[0021] In this invention, the electrodes on the ceramic particles are composited using magnetron sputtering, and the magnetron sputtering conditions can be conventional. This invention demonstrates that constructing the electrodes using magnetron sputtering successfully achieves synergistic adaptation between organic materials and ceramics based on a mechanical interlocking mechanism, thereby endowing the fabricated device with excellent stretchability and sensing output performance.

[0022] In this invention, the angle between the direction of magnetron sputtering and the direction of the orientation aperture of the ceramic particles is between -20° and +20°. Furthermore, during the sputtering process, the target material can be positioned above the orientation aperture.

[0023] In this invention, the sputtering electrode method for the ceramic particles can be conventional. For example, one end of the ceramic particle (e.g., the side near the bottom edge in contact with the base film) and its opposite end are sputtered with conductive metal, and the conductive metals at both ends do not contact each other. For example, one end of the ceramic particle can be any edge region of the ceramic particle, and the opposite end can be the far end of that edge region. For example, when the ceramic particle is a cuboid or rectangular prism, conductive metal can be sputtered on the edge of its surface with orientation holes (e.g., near the edge in the width direction), and conductive metal can also be sputtered on the opposite end, while no conductive metal is sputtered in the middle. After polarization treatment, a polarized ceramic with a p-end and an n-end is formed. As another example, when the ceramic particle is a hemisphere, conductive metal can be sputtered on the bottom edge region and the far edge region of the bottom of the hemisphere, respectively.

[0024] In this invention, the conductive metal can be any metal that is conductive and capable of sputtering, such as gold.

[0025] Preferably, in the ceramic array, the p-ends of each polarized ceramic particle are connected in series, and the n-ends are also connected in series. In this invention, the conductive circuits connecting the p-ends of each ceramic particle in series and the conductive circuits connecting the n-ends of each ceramic particle in series do not contact each other, and are preferably arranged in a nearly parallel manner.

[0026] Preferably, the conductive material is a wire or a conductive liquid metal or its alloy, and more preferably at least one of copper, gallium-indium alloy, and gallium-indium-tin alloy.

[0027] In this invention, the bottom film is a polymer film, and more preferably a mixture of PDM Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1-2:1-2.

[0028] The thickness of the base film can be adjusted as needed, for example, it can be 0.1mm to 1mm.

[0029] The present invention also provides a method for preparing the stretchable oriented porous array piezoelectric ceramic sensor, wherein ceramic particles with oriented holes are prepared; conductive metal is sputtered onto both ends of the ceramic particles, and then polarized to obtain polarized ceramic particles.

[0030] Polarized ceramic particles are placed on a base film pre-laid with conductive material, so that each polarized ceramic particle is electrically connected along the polarization direction through the conductive material. Then, the composite encapsulation material is used for encapsulation to obtain the final product.

[0031] In this invention, conductive metal electrodes are constructed on ceramic particles by sputtering, and then polarized and arrayed along the polarization pattern for conductive connection. This is further combined with the synergistic combination of the composite encapsulation material in a special ratio. This unexpected synergy can solve the problem of interface compatibility caused by the incompatibility of modulus between ceramic materials and organic materials based on the mechanical interlocking mechanism, thereby obtaining a device with excellent stretchability and sensing performance.

[0032] In this invention, the method for preparing the oriented holes can be conventional. For example, the ceramic particles with the oriented holes can be prepared by freeze casting.

[0033] In this invention, conductive metal is constructed on ceramic particles by sputtering, which can unexpectedly combine with the composite packaging material. This can unexpectedly improve the interface compatibility between the composite organic material and the ceramic based on the mechanical interlocking mechanism, thereby synergistically endowing the device with stretchability and improving its stretchability and output performance.

[0034] In this invention, the middle part of the ceramic particles can be shielded with a material, and then magnetron sputtering can be performed to sputter conductive metal into the exposed areas at both ends.

[0035] In this invention, during the magnetron sputtering process, the target material can be placed at the top of the orientation hole direction of the ceramic material.

[0036] In this invention, after magnetron sputtering is completed, polarization treatment can be performed using existing methods, such as using corona treatment to polarize the obtained ceramic particles.

[0037] In this invention, conductive materials can be laminated onto a base film. For example, conductive channels can be formed on the base film, and the conductive material can be disposed in the conductive channels.

[0038] In this invention, two parallel conductive materials can be disposed on the base film, and the distance between them can be matched with the size of the polarization electrode distance of the ceramic particles.

[0039] In this invention, the polarized ceramic particles are arranged in an array such that the p-ends are arranged in parallel and electrically connected, and the n-ends are arranged in parallel and electrically connected.

[0040] The present invention also provides an application of the aforementioned flexible oriented porous array piezoelectric ceramic power generation device, which is used to prepare a low-frequency energy harvesting device.

[0041] In this invention, the flexible oriented porous array piezoelectric ceramic power generation device can be further used in sensing fields where there are requirements for tensile applications, such as wearable devices; preferably, it can be used to prepare patches; more preferably, it can be used to prepare patches based on the piezoelectric ceramic sensor for non-invasive monitoring of the progression of knee osteoarthritis.

[0042] Beneficial effects

[0043] (1) This invention provides a novel stretchable device that innovatively employs an array of oriented bore ceramic particles, combined with sputtered conductive metal and the aforementioned special composite encapsulation material. This synergistic effect unexpectedly improves the interface compatibility between the ceramic material and the organic material based on a mechanical interlocking mechanism, thereby endowing the device with excellent stretchability. Moreover, it also helps to improve its output performance. Furthermore, this invention also shows that setting the ceramic particles into a hemispherical shape with oriented bores, combined with the aforementioned composite encapsulation material and the electrode construction concept of magnetron sputtering, can further synergize and improve the stretch output stability of the prepared device.

[0044] (2) The material preparation method of this device is simple, the arraying process is simple, the cost is low, and it can be prepared on a large scale. Attached Figure Description

[0045] Figure 1 Digital photographs of device A under different stretching conditions are shown. (a) is a digital photograph of device A without stretching; (b) is a digital photograph of device A stretched to 120% of its original length; (c) is a digital photograph of device A stretched to 140% of its original length; and (d) is a digital photograph of device A stretched to 160% of its original length. The scale is 2 mm. The hemispherical ceramics are arranged in a horizontal row of 3 and a vertical row of 6, with the column spacing being 2 mm.

[0046] Figure 2 The stress-strain curves of devices A, B, and E were obtained from tensile tests conducted on a universal testing machine. Blue represents the stress-strain curve of device E; green represents the stress-strain curve of device A; and gray represents the stress-strain curve of device B.

[0047] Figure 3 These are microscopic images of the electrode surfaces of gold-sprayed ceramic (corresponding to device A) and silver-coated ceramic (corresponding to device B) obtained by scanning electron microscopy.

[0048] Figure 4 The stress-strain curves of devices A, C, and D were obtained from tensile tests conducted on a universal testing machine. Blue represents the stress-strain curve of device D; green represents the stress-strain curve of device A; and gray represents the stress-strain curve of device C.

[0049] Figure 5Digital images and contact angles of the three polymers on a porous ceramic surface with a porosity of 55% were observed using an optical water contact angle meter after PE (1:1, corresponding to device A), PDMS Sylgard 184 (corresponding to device C) and Ecoflex 00-30 (corresponding to device D) were dropped onto the surface of the porous ceramic surface with a porosity of 55% for 7 minutes. The scale bar is 50 μm.

[0050] Figure 6 The voltage-force curves of device A were measured at 2 Hz with applied stresses of 2 N, 4 N, 8 N, 10 N, 12 N, 14 N, and 16 N, after the device was placed on a longitudinal force-applying device.

[0051] Figure 7 The voltage-strain curves were measured at 2 Hz with tensile strain values ​​of 10%, 20%, 30%, 40%, 50%, and 60% when device A was placed on a transverse tensile device. Detailed Implementation

[0052] The present invention will be further described below with reference to specific embodiments. These embodiments should be understood as being for illustrative purposes only.

[0053] This invention is not intended to limit the scope of protection of the invention. Any modifications or alterations made to this invention based on its principles after reading the description herein also fall within the scope defined by the claims.

[0054] This invention provides a stretchable, oriented, porous array piezoelectric ceramic sensor, comprising a base film, a ceramic array layer disposed on the base film, and a composite encapsulation material for encapsulating the ceramic array layer and bonding it to the base film. The composite encapsulation material comprises PDMS Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1–2:1–2. Both PDMS Sylgard 184 and Ecoflex 00-30 are common commercial products in the industry. For example, PDMS Sylgard 184 is formulated by mixing agent A and agent B in a weight ratio of 9–11:1 (10:1 in this case) as per its commercial guidelines. Ecoflex 00-30 is formulated by mixing agent A and agent B in a ratio of 1:0.5–1.5 (1:1 in this case).

[0055] The ceramic array layer includes a plurality of polarized ceramic particles with orientation holes and conductive metal sputtered at both ends facing each other. Each ceramic particle is electrically connected along the polarization direction by a conductive material disposed on the surface of the bottom film (including two conductive circuits, wherein the first conductive circuit is a circuit formed by connecting the p ends of each ceramic particle in series, and the second conductive circuit is a circuit formed by connecting the p ends of each ceramic particle in series, which is a circuit formed by connecting the n ends of each ceramic particle in series).

[0056] In this invention, there are no special requirements for the particle shape of the ceramic material. For example, unless otherwise stated, hemispherical ceramic particles can be used as typical examples in the following cases.

[0057] In this invention, the ceramic particles are provided with orientation holes along their height, and the content of the orientation holes can be 30-65%.

[0058] In this invention, the shape of the ceramic material is not particularly required, and the method for constructing the orientation holes can also be based on conventional freeze casting processes.

[0059] For example, in this invention, hemispherical oriented hole ceramics can be formed by hydrophobic droplet freeze casting process, and square or other regular oriented hole ceramics can be obtained by mold casting freeze forming process.

[0060] In this invention, taking hemispherical oriented hole ceramic as an example, the preparation process is as follows: obtaining a ceramic slurry dispersed with piezoelectric ceramic particles, additives, binders, and solvents (specifically, water); wherein the additives in the ceramic slurry include at least one of Aisen 3000 and AG165; the solid content of the piezoelectric ceramic particles is 10-40%, the content of the additives is 10-25%, and the content of the binder is less than 10 wt.%;

[0061] The ceramic slurry is dropped onto a hydrophobic surface modified with a hydrophobic agent, forming ceramic droplets based on hydrophobic tension. It is then frozen to temperature T at a freezing rate of 1.5–4 °C / min and held at that temperature for 10–40 min. After that, it is freeze-dried to obtain a dry blank. The dry blank is then calcined to obtain the final product.

[0062] The temperature of T is below -75°C;

[0063] The hydrophobic agent mentioned above includes Naroco NC319.

[0064] The ceramic slurry contains 30-40% piezoelectric ceramic particles (solid content), 15-20% additives, and 0.5-5 wt% binder. The freezing rate is 2-4 °C / min. The temperature T is -170 to -90 °C. The freeze-drying time is at least 10 hours, preferably 30-60 hours. The calcination temperature is 1000-1500 °C. The calcination time is 1-5 hours, more preferably 2-4 hours.

[0065] In this invention, there are no special requirements for the size of the ceramic particles. In addition, conductive metal particles can be composited on both sides of the ceramic particles based on known sputtering methods, and polarized based on known methods to construct p-segments and n-segments.

[0066] For example, taking the ceramic material as a hemisphere (or an ellipsoid close to a hemisphere) as an example, conductive metal is pre-sputtered on a certain edge region of the bottom hemisphere (which can be named region A) and its opposite distal edge region (which can be named region B), and the conductive metals of region A and region B are not connected. Subsequently, they are polarized, and region A and region B are polarized to p-ends or n-ends.

[0067] In this invention, the array arrangement can be matrix-like, and the isopolarized ends (e.g., pp; nn) of each ceramic particle are arranged side by side and connected by a conductive material.

[0068] In this invention, after the array is set up, it is encapsulated based on the composite encapsulation material.

[0069] In this invention, taking the ceramic material as a hemisphere as an example, the fabrication steps of the device formed therefrom may include the following steps:

[0070] Step (1):

[0071] A hemispherical piezoelectric ceramic with oriented through-holes along the height direction of the protrusions was prepared by the ice template method; the porosity of the porous piezoelectric ceramic was 30-65%.

[0072] Step (2):

[0073] Liquid metal is injected into a syringe, and then liquid metal circuits (a first conductive liquid metal circuit and a second conductive liquid metal circuit, which are nearly parallel) are drawn on a polymer thin film substrate.

[0074] The middle of the hemispherical ceramic is covered with a thin adhesive tape (the middle hemisphere is covered in a direction perpendicular to the bottom surface). Gold is sputtered on the target in a magnetron sputtering instrument (with the orientation hole facing upwards) to form a two-half structure with gold electrodes on the left and right sides and no electrode in the middle. The structure is then polarized under a corona polarization instrument to form a structure with one side as the p end and the other as the n end. The p end and the n end do not contact each other and are not electrically connected throughout the ceramic body.

[0075] Step (3):

[0076] Hemispherical piezoelectric ceramics with oriented through holes are arranged in a designed array and polarization direction between a first conductive circuit (which can be a conductive liquid metal circuit) and a second conductive circuit (which can be a liquid metal circuit). The gold electrode (p end) on one side of each hemispherical piezoelectric ceramic is connected to the first conductive liquid metal circuit, and the gold electrode (n end) on the other side is connected to the second conductive liquid metal circuit. Then, the array gaps are encapsulated with encapsulation material to obtain the stretchable oriented porous array piezoelectric ceramic sensor.

[0077] In this invention, the hemispherical porous piezoelectric ceramic has a relatively flat bottom surface and an arched top surface, and has through holes in the height direction, wherein the height direction refers to the direction from the bottom surface to the top surface.

[0078] In this invention, the porosity of the porous piezoelectric ceramic block is 30-65%. This invention has found that at this preferred porosity, the problem of modulus mismatch between rigid ceramics and flexible polymers can be further solved, enabling the successful preparation of porous array materials. These materials possess good flexibility and torsional stability, and unexpectedly, the piezoelectric voltage-current output effect of the porous ceramic array material can be synergistically improved.

[0079] The present invention also includes the application of the stretchable oriented porous array piezoelectric ceramic sensor described above, to fabricate a low-frequency self-powered sensor.

[0080] Part One:

[0081] Example 1 (labeled as Device A):

[0082] Step (1) Preparation of hemispherical oriented porous BCZT ceramics with a porosity of 55%:

[0083] Step (1-A):

[0084] BCZT powder was prepared using analytically pure BaCO3 (99% purity), CaCO3 (99% purity), TiO2 (99% purity), and ZrO2 (99% purity) as raw materials via a solid-state reaction method. The steps were as follows: the stoichiometrically mixed raw material powders were ball-milled for 12 hours, then calcined in a box furnace (air atmosphere) at 1300°C for 3 hours. Further ball milling in alcohol for 24 hours, followed by drying and sieving, yielded BCZT powder suitable for preparing cryogenic casting slurries.

[0085] BCZT powder, water, Aisen 3000 as an additive, and polyvinyl alcohol (PVA-124) as a binder were mixed and ball-milled for 12 hours to obtain a ceramic slurry. In the ceramic slurry, the solid content of BCZT was 30 wt.%, the content of the additive was 15 wt%, and the content of PVA-124 was 1 wt%.

[0086] Step (1-B):

[0087] Apply Naroko NC319 evenly to a clean, smooth glass slide using a coater, and dry it in an oven (for example, for 5 minutes). Once completely dry, a thin superhydrophobic coating will be formed on the glass slide surface.

[0088] Step (1-C): Preparation of Oriented Porous BCZT Ceramic Droplets

[0089] Using an eight-channel pipette, droplets of the BCZT slurry from step 1-A were placed onto a glass slide coated with a superhydrophobic layer in step 1-B. The slide was then cooled from 5°C to -100°C on a hot-cold plate at a rate of 3°C / min and held at that temperature for 20 minutes. The frozen droplets were then transferred to a freeze dryer and freeze-dried for 48 hours.

[0090] The dried blank was then removed and calcined at 1350℃ (in air atmosphere) for 3 hours to obtain hemispherical ceramic particles with oriented porosity along the height direction. The pore volume fraction of these droplet-shaped porous ceramic particles was measured to be approximately 55% (specifically 50-57%) using Archimedes' displacement method. The bottom dimension was 2.5 mm, and the height was 1.3 mm.

[0091] Step (2) Electrode preparation and polarization of hemispherical oriented porous BCZT ceramic

[0092] The ceramic particles obtained in step 1 are then subjected to batch sputtering and polarization, as follows:

[0093] The ceramic particles with their protrusions facing upwards were arranged side-by-side, and the center of each protrusion was sealed with aluminum adhesive. A gold target was then placed on top of the ceramic particles, and sputtering was performed for 5 minutes in an argon atmosphere using a magnetron sputtering system to create the gold electrode on the ceramic. The aluminum adhesive used as a mask was removed, resulting in a hemispherical layered ceramic with gold electrodes on both sides (divided longitudinally into an Au layer, a BCZT layer (the shielded area), and another Au layer). Then, a corona polarization process was used to induce piezoelectric activity in the ceramic (piezoelectric coefficient approximately 320 pC / N).

[0094] Step (3) Fabrication of the stretchable circuit for the stretchable oriented porous array piezoelectric ceramic sensor

[0095] Liquid metal was injected into a syringe, and then a liquid metal pattern was drawn on a polymer thin film substrate (PDMS Sylgard184 and Ecoflex 00-30 in a 1:1 weight ratio). The linewidth of the liquid metal circuit was 200 μm, and conductivity was tested using a multimeter to ensure good continuity of the electrode structure. Excess portions in the electrode lines were erased to form two parallel serpentine structures. Subsequently, polarized hemispherical porous ceramics were carefully placed in a customized arc-shaped electrode pattern, with the gold electrode on one side of the hemispherical piezoelectric ceramic connected to the first conductive liquid metal circuit and the gold electrode on the other side connected to the second conductive liquid metal circuit. The array was a 3*6 rectangular array, in which the hemispherical ceramics were arranged in 3 horizontal rows and 6 vertical rows, with 2 mm intervals between the columns horizontally and vertically.

[0096] Step (4) Packaging of the stretchable oriented porous array piezoelectric ceramic sensor (composite packaging, also known as PE packaging)

[0097] PDMS Sylgard 184 and Ecoflex 00-30 were mixed thoroughly at a 1:1 mass ratio. After thorough mixing, the mixture was placed in a vacuum drying oven and subjected to repeated vacuuming / degassing three times to completely remove air bubbles. The blend of PDMS Sylgard 184 and Ecoflex 00-30 was designated PE (1:1). PE was then rapidly infiltrated into the rich pores of the oriented porous ceramic as an encapsulation material to form a mechanical interlock with the ceramic, and allowed to cure overnight (labeled Device A).

[0098] Depend on Figure 1 As can be seen from (a)-(d), the stretchable oriented porous array piezoelectric ceramic sensor obtained in step (4) has excellent stretchability and can be stretched up to 160% of its original length.

[0099] Comparative Example 1 (labeled as Device B):

[0100] Compared to Example 1, the only difference is that magnetron sputtering was not used to form the conductive electrode. Instead, a silver electrode was coated on a similar area of ​​the Au metal in Example 1. That is, the method of preparing the ceramic surface electrode in step (2) was changed to using a thin aluminum tape to string the hemispherical ceramic together. Instead of sputtering gold electrodes using a magnetron sputtering instrument, a thin layer of silver paste was coated on the left and right sides of the ceramic. After drying at 100°C for 5 minutes, the aluminum tape was removed, and finally a surface electrode structure with silver electrodes on the left and right sides was obtained. Other operations and parameters were the same as in Example 1, and a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device B) was obtained.

[0101] Comparative Example 2 (labeled as Device C):

[0102] Compared to Example 1, the only difference is that in control step (4), a PDMS Sylgard 184 package of the same quality is used instead of a composite package. Other operations and parameters are the same as in Example 1, resulting in a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device C).

[0103] Comparative Example 3 (labeled as Device D):

[0104] Compared to Example 1, the only difference is that in control step (4), instead of using a composite package, an Ecoflex 00-30 package of the same quality is used. Other operations and parameters are the same as in Example 1, resulting in a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device D).

[0105] Comparative Example 4 (labeled as Device E):

[0106] Compared with Example 1, the only difference is that in control step (2), gold sputtering is not performed, and the ceramic surface is left without electrodes. Other operations and parameters are the same as in Example 1, and a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device E) is obtained.

[0107] Comparative Example 5 (labeled as Device F):

[0108] Compared with Example 1, the only difference is that in control step (4), PDMS Sylgard 184 and Ecoflex 00-30 are not mixed again at a mass ratio of 1:1, but at a ratio of 1:3. Other operations and parameters are the same as in Example 1, and a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device F, PE (1:3)) is obtained.

[0109] Comparative Example 6 (labeled as Device G):

[0110] Compared with Example 1, the only difference is that in control step (4), PDMS Sylgard 184 and Ecoflex 00-30 are not mixed again at a mass ratio of 1:1, but at a ratio of 3:1. Other operations and parameters are the same as in Example 1, and a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device G, PE (3:1)) is obtained.

[0111] Comparative Example 7 (labeled as Device H):

[0112] Compared to Example 1, the only difference is that in control step (4), instead of using PDMS Sylgard184 and Ecoflex 00-30 packages with a mass ratio of 1:1, Dragon Skin 10NV is used for packaging. Other operations and parameters are the same as in Example 1, resulting in a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device H).

[0113] Example 2 (labeled as Device I):

[0114] Compared with Example 1, the only difference is that in control step (1), the hydrophobic spheroidization steps 1-B and 1-C are missing. Instead, after obtaining the BCZT ceramic slurry in 1-A, it is frozen in a 3*3*3cm silicone mold to obtain a dry blank, which is then sintered and cut into square ceramic cylinders of the same volume. Other operations and parameters are the same as in Example 1, and a stretchable oriented porous array piezoelectric ceramic sensor (labeled as device I) is obtained. The other ceramic electrodes, ceramic arrays, etc., are the same as in Example 1.

[0115] Comparative Example 8 (labeled as Device J):

[0116] Compared to Example 2, the only difference is that instead of using a freeze-casting method to form oriented porous ceramics, BCZT powder was directly pressed into 3*3*3cm ceramic sheets, sintered, and then cut into dense square ceramic cylinders of the same volume. Other operations and parameters were the same as in Example 1, resulting in a stretchable dense ceramic array piezoelectric ceramic sensor (labeled as device J).

[0117] Part Two: Stretchability Testing of Stretchable Oriented Porous Array Piezoelectric Ceramic Sensors

[0118] 2.1: Comparison of the stretchability of stretchable oriented porous array piezoelectric ceramic sensors with different electrode materials

[0119] Sensors (devices A, B, and E) with gold-sprayed and silver-coated electrodes on their left and right sides, respectively, of the fabricated oriented porous hemispherical piezoelectric ceramics were subjected to tensile tests on a universal testing machine. Tensile tests were performed at a speed of 10 mm / min, and the stress-strain curves of the devices were obtained. The test results are shown below. Figure 2 :

[0120] from Figure 2 The results show that the gold-plated ceramic device A has a fracture elongation of 152% and a fracture stress of 179 kPa. The silver-coated ceramic device B has a fracture elongation of 36% and a fracture stress of 41 kPa. The fracture elongation and fracture stress of the gold-plated ceramic device A are 4.2 times and 4.4 times that of the silver-coated device B, respectively. The electrodeless ceramic device E has a fracture elongation of 153% and a fracture stress of 199 kPa. The fracture elongation and fracture stress of the gold-plated ceramic device A are very close to those of the electrodeless device E. This indicates that the process of the present invention can solve the problem of tensile influence faced in the construction process of orientation hole ceramic electrodes.

[0121] The microstructure of the electrode surfaces of gold-sprayed ceramic in Example 1 and silver-coated ceramic in Comparative Example 1 are shown in the figure. Figure 3 :

[0122] 2.2 Comparison of the stretchability of stretchable oriented porous array piezoelectric ceramic sensors with different encapsulation materials

[0123] Device A (PE (1:1) package), device C (PDMS Sylgard 184 package), and device D (Ecoflex 00-30 package) were subjected to tensile tests on a universal testing machine. Tensile tests were performed at a speed of 10 mm / min, and the stress-strain curves of the devices were obtained. The test results are shown below. Figure 4 :

[0124] from Figure 4It can be seen that when the strain is 71%, the device C in the Sylgard 184 package of PDMS fractured at the PDMS encapsulation layer (fracture stress of 65 kPa). This indicates that although PDMS can form a strong interfacial bond with porous ceramics, its elongation at break is low, making it prone to tearing during stretching. The device D in the Ecoflex 00-30 package failed due to delamination at the bonding interface when stretched to 102% (fracture stress of 44 kPa). This shows that although Ecoflex is an excellent stretchable material, its interfacial bond with porous ceramics is weak. In contrast, the device A in the PE (1:1) package exhibits the highest tensile strain (elongation at break up to 153%) and fracture stress (199 kPa), demonstrating that it possesses both strong interfacial bond and excellent stretchability.

[0125] To achieve strong mechanical interlocking, the polymer must possess good wettability and flowability to spread on the ceramic surface and fully penetrate into the pores. Therefore, the wettability and flowability of PE (1:1), PDMS Sylgard 184, and Ecoflex 00-30, respectively, dropped onto the ceramic surface were observed using an optical water contact angle meter after 7 minutes.

[0126] like Figure 5 As shown, PDMS Sylgard 184, when dropped onto a porous ceramic surface with a porosity of 55%, completely wetted the ceramic after 7 minutes, with a contact angle of approximately 0°, indicating that PDMS Sylgard 184 can quickly penetrate into the pores to form a strong mechanical interlock. In contrast, Ecoflex 00-30 still had a contact angle as high as 42.4° after 7 minutes, indicating that Ecoflex 00-30 had difficulty spreading on the ceramic surface and therefore could not form a strong mechanical interlock. Similar to PDMS Sylgard 184, PE (1:1) had a water contact angle of only 26.9° on the porous ceramic surface, indicating that it could effectively wet the substrate and form a relatively strong mechanical interlock.

[0127] 2.3 Comparison of the stretchability of stretchable oriented porous array piezoelectric ceramic sensors with different encapsulation material ratios

[0128] Device A, packaged using a 1:1 mixture of PDMS Sylgard 184 and Ecoflex 00-30; device F, packaged using a 1:3 mixture of PDMS Sylgard 184 and Ecoflex 00-30; device G, packaged using a 3:1 mixture of PDMS Sylgard 184 and Ecoflex 00-30; and device H, packaged using Dragon Skin 10NV, were subjected to tensile tests on a universal testing machine. Tensile tests were performed at a speed of 10 mm / min, and the stress-strain curves of the devices were obtained. The test results are shown in Table 1.

[0129] Table 1. Fracture elongation and fracture stress of devices A, F and G.

[0130]

[0131] The table shows that PE (1:1) is the optimal packaging ratio.

[0132] 2.4 Comparison of the stretchability of stretchable array piezoelectric ceramic sensors made of dense ceramics and oriented porous ceramics

[0133] Oriented porous ceramic device I and dense ceramic device J were placed on a universal testing machine for tensile testing. Tensile tests were performed at a speed of 10 mm / min, and the stress-strain curves of the devices were obtained.

[0134] The test results are shown in Table 2:

[0135] Table 2

[0136]

[0137] It can be seen that dense ceramic devices cannot form mechanical interlocks with polymers, resulting in weak interfacial bonding. This proves that the abundant pores in oriented porous ceramics play a key role in interfacial bonding.

[0138] Part 3: Electrical Output Performance Testing of Stretchable Oriented Porous Array Piezoelectric Ceramic Sensors

[0139] Devices A and I were placed on a torsion device and connected to a microammeter for electrical performance testing. After 2500 and 5000 cycles at a frequency of 1.5 Hz and a torsion angle of 180°, the voltage values ​​were measured and are shown in Table 3.

[0140] Table 3

[0141]

[0142] Table 3 shows that under 5000 cycles of 180° torsional load, the open-circuit voltage of device A remains almost unchanged, but the voltage of device I drops significantly, indicating that the hemispherical ceramic composite (device A) has higher output stability.

[0143] Device A was placed on a longitudinally applied force device and connected to a microammeter for electrical performance testing. Its voltage was measured at a frequency of 2Hz and applied stresses of 2N, 4N, 8N, 10N, 12N, 14N, and 16N. The results are shown below. Figure 6 ;

[0144] Figure 6 It can be seen that under a 2Hz compressive load, the open-circuit voltage of device A is approximately linear with the increase of external force (R). 2 As the voltage increases from 0.99 to 16N, its open-circuit voltage can reach 43V, which is much higher than that of the traditional 0-3 type piezoelectric composite. This indicates that the hemispherical ceramic composite can exhibit excellent output capability under low-frequency pressure stimulation.

[0145] Next, device A was placed on a transverse tensile apparatus and connected to a microammeter for electrical performance testing. Its voltage values ​​were measured at a frequency of 2Hz and tensile strain values ​​of 10%, 20%, 30%, 40%, 50%, and 60%. The results are shown below. Figure 7 ;

[0146] from Figure 7 As can be seen, within the tensile range of 10% to 60%, the open-circuit voltage of device A increases from 1.3V to 5.8V and exhibits high correlation (R0) over a wide strain range of 60%. 2 =0.99).

Claims

1. A stretchable, oriented, porous array piezoelectric ceramic sensor, characterized in that, The invention includes a base film, a ceramic array layer disposed on the base film, and a composite encapsulation material for encapsulating the ceramic array layer and bonding it to the base film; the composite encapsulation material includes PDMS Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1~2:1~2. The ceramic array layer includes a plurality of polarized ceramic particles with orientation holes and conductive metal sputtered at both ends, and each ceramic particle is electrically connected along the polarization direction by a conductive material disposed on the surface of the base film. The ceramic particles are sputtered with conductive metal at one end and the opposite end, and the conductive metals at both ends do not contact each other. The conductive metal is gold; In the ceramic array, the p-ends of each polarized ceramic particle are connected in series and the n-ends are connected in series. The conductive material is a wire or a conductive liquid metal or its alloy.

2. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The porosity of the ceramic particles is 30-65%.

3. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The angle between the orientation hole direction of the ceramic particles and the plane direction of the bottom film is between 70° and 120°.

4. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The ceramic particles are made of at least one of barium zirconate titanate, lead zirconate titanate, barium titanate, and potassium sodium niobate.

5. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 4, characterized in that, The ceramic particles are made of at least one of PZT-5A, PZT-5H, BCZT, and BTO.

6. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The cross-section of the ceramic particles is square, rectangular, circular, or elliptical.

7. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The ceramic particles are hemispherical.

8. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The height of the ceramic particles is 1~10 mm.

9. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 8, characterized in that, The height of the ceramic particles is 1~5 mm.

10. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, In the ceramic array layer, the number of ceramic particles is two or more.

11. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 10, characterized in that, In the ceramic array layer, the number of ceramic particles is 5 to 30.

12. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 10, characterized in that, The spacing between adjacent ceramic particles is 0.5~5 mm.

13. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The conductive material is at least one of copper, gallium-indium alloy, and gallium-indium-tin alloy.

14. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 1, characterized in that, The base film is a polymer film, which is PDMS Sylgard 184 and Ecoflex 00-30 in a weight ratio of 1~2:1~2.

15. The stretchable oriented porous array piezoelectric ceramic sensor as described in claim 14, characterized in that, The thickness of the base film is 0.1 mm to 1 mm.

16. A method for fabricating a stretchable, oriented porous array piezoelectric ceramic sensor according to any one of claims 1 to 15, characterized in that, Ceramic particles with oriented holes were prepared; conductive metal was sputtered onto both ends of the ceramic particles, and then they were polarized to obtain polarized ceramic particles. Polarized ceramic particles are placed on a base film pre-laid with conductive material, so that each polarized ceramic particle is electrically connected along the polarization direction through the conductive material. Then, the composite encapsulation material is used for encapsulation to obtain the final product.

17. The method for fabricating a stretchable, oriented porous array piezoelectric ceramic sensor as described in claim 16, characterized in that, The oriented ceramic particles were prepared by freeze casting.

18. The method for fabricating a stretchable, oriented porous array piezoelectric ceramic sensor as described in claim 16, characterized in that, The middle part of the ceramic particles is shielded with a material, and then magnetron sputtering is performed to sputter conductive metal into the exposed areas at both ends.

19. The method for fabricating a stretchable, oriented porous array piezoelectric ceramic sensor as described in claim 16, characterized in that, The prepared ceramic particles were polarized by corona treatment.

20. The method for fabricating a stretchable, oriented porous array piezoelectric ceramic sensor as described in claim 16, characterized in that, Conductive channels are formed on the base film, and conductive material is disposed in the conductive channels.

21. An application of the stretchable oriented porous array piezoelectric ceramic sensor according to any one of claims 1 to 15, characterized in that, It was used to prepare a low-frequency energy harvesting device.

22. The application of the stretchable oriented porous array piezoelectric ceramic sensor as described in claim 21, characterized in that, It can be used to manufacture wearable devices.

23. The application of the stretchable oriented porous array piezoelectric ceramic sensor as described in claim 22, characterized in that, It is used to prepare patches.

24. The application of the stretchable oriented porous array piezoelectric ceramic sensor as described in claim 23, characterized in that, This was used to prepare a patch for non-invasive monitoring of knee osteoarthritis progression based on the stretchable oriented porous array piezoelectric ceramic sensor.

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