A flexible piezoelectric ultrasonic transducer and a method of manufacturing the same

Abstract

The application discloses a flexible piezoelectric ultrasonic transducer, which comprises a flexible electrode and a 1-3 type composite piezoelectric element, and the flexible electrode is arranged on the upper surface and the lower surface of the piezoelectric element; wherein the 1-3 type composite piezoelectric element is made of 1-3 type composite piezoelectric material formed by a first flexible base material and piezoelectric ceramic; wherein the piezoelectric ceramic is periodically arranged and embedded on the first flexible base material to form a plurality of piezoelectric columns; the flexible electrode is led out through a conductive cable and combined with an external active control program through a connector, and the focal point position of a focused sound beam and the sound field form can be dynamically changed by dynamically adjusting the form curvature of the flexible ultrasonic transducer. The flexible piezoelectric ultrasonic transducer can form various focused sound field forms by dynamically adjusting the form curvature of the flexible ultrasonic transducer, highlights the advantage of the flexible piezoelectric ultrasonic transducer in flexible sound field regulation, and realizes active and efficient modulation of an ultrasonic sound field.

Description

Technical Field

[0001] This invention belongs to the field of acoustic technology, specifically relating to a flexible piezoelectric ultrasonic transducer and its preparation method. Background Technology

[0002] Underwater acoustic field manipulation technology is central to many ultrasound applications, such as medical imaging, ultrasound therapy, industrial inspection, and marine science. As a core component of ultrasound processing equipment, the performance of the ultrasonic transducer directly determines the effectiveness of power ultrasound applications.

[0003] Traditional ultrasonic transducers can only produce a single type of sound field. However, diverse applications require ultrasonic transducers to produce specific sound field distributions as needed.

[0004] Currently, passive sound field control methods mainly rely on lens design. However, existing acoustic lenses are limited by low transmission efficiency and manufacturing precision, failing to meet the demands of sound field control. While arrays are currently the primary method for active sound field control, their drawbacks include complex structure and high cost. Therefore, in the face of diverse sound field distribution requirements, designing an ultrasonic transducer capable of flexibly controlling the sound field is a pressing issue that needs to be addressed. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a flexible piezoelectric ultrasonic transducer and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] A first aspect of the present invention provides a flexible piezoelectric ultrasonic transducer, comprising a flexible electrode and a type 1-3 composite piezoelectric element, wherein the flexible electrode is disposed on the upper and lower surfaces of the piezoelectric element;

[0007] The type 1-3 composite piezoelectric element is made of a type 1-3 composite piezoelectric material formed by a first flexible substrate material and piezoelectric ceramics; wherein the piezoelectric ceramics are periodically arranged and embedded in the first flexible substrate material to form a plurality of piezoelectric pillars;

[0008] The flexible electrode is led out through a conductive cable and connected to an external active control program through a connector. By dynamically adjusting the shape and curvature of the flexible ultrasonic transducer, the focal position of the focused sound beam and the shape of the sound field can be dynamically changed.

[0009] In one embodiment of the present invention, both the type 1-3 composite piezoelectric element and the flexible electrode are annular.

[0010] In one embodiment of the present invention, in the type 1-3 composite piezoelectric material formed by the first flexible substrate material and the piezoelectric ceramic, the width of the piezoelectric pillar is 200um-700um, the spacing between the piezoelectric pillars is 50um-200um, and the volume fraction of the piezoelectric phase is 30%-70%.

[0011] In one embodiment of the present invention, the first flexible substrate material comprises PDMS, and the piezoelectric ceramic material comprises PZT8.

[0012] In one embodiment of the present invention, the flexible electrode is made of a second flexible substrate material doped with metal powder particles. The metal powder particles include micron-sized silver powder particles, and the silver powder particles are spherically monodisperse; the second flexible substrate material includes PDMS.

[0013] In one embodiment of the present invention, the acoustic impedance of the flexible electrode satisfies:

[0014]

[0015] In the formula, Z b Z represents the acoustic impedance of the flexible electrode. l Z represents the acoustic impedance of the front-end load. p This represents the acoustic impedance of the composite piezoelectric material.

[0016] In one embodiment of the present invention, the volume fraction of silver powder particles in the flexible electrode is 23.4%.

[0017] A second aspect of the present invention provides a method for fabricating a flexible piezoelectric ultrasonic transducer, comprising the following steps:

[0018] Step 1: Prepare a piezoelectric ceramic sheet and use a high-precision cutting machine to cut slits with consistent spacing and groove depth along the x-axis and y-axis directions on the piezoelectric ceramic sheet to form periodically arranged piezoelectric columns.

[0019] Step 2: Prepare a mixture of the first flexible substrate material;

[0020] Step 3: The mixture of the first flexible substrate material is poured into the cut slit of the piezoelectric ceramic sheet by siphon method and cured to form a flexible substrate, thereby obtaining a type 1-3 composite piezoelectric element;

[0021] Step 4: Prepare flexible electrodes on the upper and lower surfaces of the type 1-3 composite piezoelectric material to obtain a type 1-3 composite piezoelectric element with flexible electrodes.

[0022] In one embodiment of the present invention, step 4 includes:

[0023] Step 4: Incorporate metal powder particles into the mixture of the second flexible substrate material, stir thoroughly, and then evenly coat the mixture onto the upper and lower surfaces of the type 1-3 composite piezoelectric element. Curing is then performed to print flexible electrodes onto the upper and lower surfaces of the type 1-3 composite piezoelectric element, thereby obtaining a type 1-3 composite piezoelectric element with flexible electrodes.

[0024] The beneficial effects of this invention are:

[0025] The flexible piezoelectric ultrasonic transducer provided by this invention introduces a 1-3 piezoelectric composite element and flexible material into the design of the ultrasonic transducer. Combining the high electromechanical coupling factor of the 1-3 piezoelectric composite element and the acoustic impedance matching characteristics of the flexible electrode, a highly efficient acoustic energy transmission effect is achieved. At the same time, by combining the designed flexible piezoelectric ultrasonic transducer with an external active control program, various focused sound field forms can be formed by dynamically adjusting the shape curvature of the flexible ultrasonic transducer. This highlights the advantages of the flexible piezoelectric ultrasonic transducer in flexible sound field control, realizing active and efficient modulation of the ultrasonic sound field, and opening up new prospects for active high-frequency sound field modulation and dynamic high-resolution ultrasonic applications.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a flexible piezoelectric ultrasonic transducer provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the type 1-3 composite piezoelectric material provided in the embodiments of the present invention;

[0029] Figure 3 This is a schematic flowchart of a method for fabricating a flexible piezoelectric ultrasonic transducer provided in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the manufacturing method of the type 1-3 composite piezoelectric element provided in the embodiments of the present invention;

[0031] Figure 5 This is a simulation diagram of the sound field patterns formed by the transducer undergoing different curvature deformations according to the embodiments of the present invention;

[0032] Figure 6 This is a test diagram of the sound field patterns formed by the transducer undergoing different curvature deformations according to an embodiment of the present invention;

[0033] Explanation of reference numerals in the attached figures:

[0034] 11-Flexible electrode, 12-Type 1-3 composite piezoelectric element, 13-Conductive cable, 14-Connector, 15-Protective film. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0036] Example 1

[0037] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a flexible piezoelectric ultrasonic transducer provided in an embodiment of the present invention, including a flexible electrode 11 and a 1-3 type composite piezoelectric element 12, wherein the flexible electrode 11 is disposed on the upper surface and the lower surface of the piezoelectric element 12;

[0038] Among them, the 1-3 type composite piezoelectric element 12 is made of a 1-3 type composite piezoelectric material formed by a first flexible substrate material and piezoelectric ceramics; wherein, the piezoelectric ceramics are periodically arranged and embedded on the first flexible substrate material to form a plurality of piezoelectric pillars;

[0039] The flexible electrode 11 is led out through the conductive cable 13 and combined with the external active control program through the connector 14. By dynamically adjusting the shape and curvature of the flexible ultrasonic transducer, a variety of focused sound field forms can be formed.

[0040] Optionally, as an implementation, the type 1-3 composite piezoelectric element 12 and flexible electrode 11 in this embodiment can be designed as a ring, wherein the outer diameter of the ring is 30mm and the inner diameter is 13mm.

[0041] In this embodiment, a type 1-3 composite piezoelectric element with a circular ring shape is selected to facilitate deformation in subsequent bending experiments.

[0042] Specifically, in this embodiment, the center frequency of the flexible piezoelectric ultrasonic transducer is designed to be 1.5MHz. Based on this design frequency, the composite structure parameters of the 1-3 type composite piezoelectric material formed by the first flexible substrate material and the piezoelectric ceramic are further designed as follows: the width of the piezoelectric column is 200um-700um, the spacing between the piezoelectric columns is 50um-200um, and the volume fraction of the piezoelectric phase is 30%-70%.

[0043] Preferably, in this embodiment, the width of the piezoelectric post is designed to be 500 μm, and the spacing between the piezoelectric posts is designed to be 200 μm. Figure 2 As shown, the volume fraction of the piezoelectric phase is designed to be 50% based on empirical values.

[0044] Furthermore, in this embodiment, the first flexible substrate material can be an epoxy resin material, such as PDMS (polydimethylsiloxane), and the piezoelectric ceramic material can be a PZT (lead zirconate titanate) series piezoelectric ceramic, such as PZT8.

[0045] It should be noted that when preparing PDMS, the ratio of prepolymer A to crosslinking agent B is 10:1.

[0046] The 1-3 type composite piezoelectric element designed in this embodiment can realize the mutual conversion of mechanical energy and electrical energy based on the piezoelectric effect. The introduced 1-3 type composite structure can also effectively improve the electromechanical coupling factor of the device, so that the electromechanical coupling factor designed in this invention can reach 0.77.

[0047] Furthermore, the flexible electrode 11 is made of a second flexible substrate material doped with metal powder particles.

[0048] In this embodiment, the metal powder particles can be common copper powder, aluminum powder, or tungsten powder, etc.

[0049] Preferably, this embodiment selects ultrafine silver powder particles; wherein the silver powder particles are spherical and monodisperse, at the micron level, thereby giving the prepared flexible electrode good conductivity. The second flexible substrate material can also be various epoxy resins; in this embodiment, commonly used PDMS material is preferred.

[0050] It should be noted that the volume ratio of the flexible electrode 11 is determined by comprehensively considering both conductivity and acoustic impedance matching effect. Its acoustic impedance is calculated based on Desilets theory and must satisfy the following formula:

[0051]

[0052] In the formula, Z b Z represents the acoustic impedance of the flexible electrode. l Z represents the acoustic impedance of the front-end load. p This represents the acoustic impedance of the composite piezoelectric material.

[0053] Specifically, the material parameters designed in this embodiment are shown in Table 1 below:

[0054] Acoustic properties of the materials listed in Table 1

[0055] speed of sound m / s <![CDATA[Density g / cm 3 > Acoustic impedance MRayls piezoelectric phase materials PZT8 4560 7600 34.66 Backend load water 1500 1000 1.50 polymer phase materials PDMS 1030 1050 1.08

[0056] Based on the acoustic impedance of the piezoelectric material, the optimal acoustic impedance of the flexible electrode designed in this embodiment is 3.35 MRayls, corresponding to a volume fraction of 23.4% for silver powder particles.

[0057] For further details, please continue to see Figure 1 The flexible electrode 11 and the type 1-3 composite piezoelectric element 12 are further provided with a protective film 15. The flexible electrode 11 is externally connected to the connector 14 via a conductive cable 13. The connector 14 can be an SMA converter head, which can be combined with an external active control program to realize the electrical connection of the transducer.

[0058] The flexible piezoelectric ultrasonic transducer designed in this embodiment can be shaped by applying external force to create a diverse and continuously variable focused sound field. By using a continuous wave as the excitation signal and dynamically changing the radius of curvature of the flexible transducer, the focal position of the focused sound beam and the shape of the sound field can be dynamically changed.

[0059] The flexible piezoelectric ultrasonic transducer provided by this invention introduces a 1-3 piezoelectric composite element and flexible material into the design of the ultrasonic transducer. Combining the high electromechanical coupling factor of the 1-3 piezoelectric composite element and the acoustic impedance matching characteristics of the flexible electrode, a highly efficient acoustic energy transmission effect is achieved. At the same time, by combining the designed flexible piezoelectric ultrasonic transducer with an external active control program, the shape curvature of the flexible ultrasonic transducer can be dynamically adjusted to form various focused sound field forms, highlighting the advantages of the flexible piezoelectric ultrasonic transducer in flexible sound field control. It realizes active and efficient modulation of the ultrasonic sound field, opening up new prospects for active high-frequency sound field modulation and dynamic high-resolution ultrasonic applications.

[0060] Example 2

[0061] This embodiment provides a method for fabricating a flexible piezoelectric ultrasonic transducer, used to prepare the flexible piezoelectric ultrasonic transducer provided in Embodiment 1 above. Please refer to... Figure 3 , Figure 3 This is a schematic flowchart of a method for fabricating a flexible piezoelectric ultrasonic transducer according to an embodiment of the present invention. The method mainly includes the following steps:

[0062] Step 1: Prepare a piezoelectric ceramic sheet and use a high-precision cutting machine to cut slits with consistent spacing and groove depth along the x-axis and y-axis directions on the piezoelectric ceramic sheet to form periodically arranged piezoelectric columns.

[0063] For details, please see Figure 4 , Figure 4 This is a schematic diagram of the manufacturing method of the type 1-3 composite piezoelectric element provided in the embodiments of the present invention.

[0064] First, prepare a 1.5mm thick PZT8 annular piezoelectric ceramic sheet. Use a high-precision cutting machine to cut slits with consistent spacing and groove depth along the x-axis on the piezoelectric ceramic sheet. The blade width is 200μm, the cutting step is 500μm, and the groove depth is 1.3mm. Repeat the above operation along the y-axis to form periodically arranged piezoelectric columns.

[0065] Step 2: Prepare a mixture of the first flexible substrate material.

[0066] Specifically, in this embodiment, PDMS is selected as the first flexible substrate material. Component A and component B of PDMS are thoroughly mixed in a ratio of 10:1 and vacuumed to remove air bubbles, so as to form a mixture of the first flexible substrate material.

[0067] Step 3: The mixture is poured into the cut slit of the piezoelectric ceramic sheet using a siphon method and cured to form a flexible substrate, thereby obtaining a type 1-3 composite piezoelectric element.

[0068] Specifically, the PDMS mixture is siphoned into the cut slit of the piezoelectric ceramic sheet, then placed in a high-temperature oven at 100°C and left to stand for 20 minutes to cure the sample, forming a type 1-3 composite piezoelectric material, and thus obtaining a type 1-3 composite piezoelectric element.

[0069] Step 4: Prepare flexible electrodes on the upper and lower surfaces of the type 1-3 composite piezoelectric element to obtain a type 1-3 composite piezoelectric element with flexible electrodes.

[0070] Specifically, metal powder particles are incorporated into a mixture of the second flexible substrate material. After thorough stirring, the mixture is evenly applied to the upper and lower surfaces of the type 1-3 composite piezoelectric element and then cured to print flexible electrodes on the upper and lower surfaces of the type 1-3 composite piezoelectric element, thus obtaining a type 1-3 composite piezoelectric element with flexible electrodes.

[0071] Preferably, in this embodiment, silver powder and PDMS are selected for the preparation of the flexible electrode.

[0072] Specifically, silver powder particles with a volume fraction of 23.4% are first incorporated into the PDMS mixture. After thorough stirring, Ag-PDMS conductive silver paste is obtained and evenly applied to the upper and lower surfaces of the piezoelectric element, and then smoothed with a scraper.

[0073] Then, the piezoelectric element coated with flexible electrodes is placed in a high-temperature oven at 100°C and left to stand for 20 minutes to cure the sample, so as to form flexible electrodes with the same shape as the piezoelectric ceramic sheet on the upper and lower surfaces of the 1-3 type composite piezoelectric element, thereby obtaining the 1-3 type composite piezoelectric element with flexible electrodes.

[0074] Understandably, after obtaining the type 1-3 composite piezoelectric element with flexible electrodes, it is necessary to manually peel off the excess PDMS cured material on the surface and around the piezoelectric ceramic sheet along its outer periphery.

[0075] After the above steps, a flexible piezoelectric element of type 1-3 with flexible electrodes is prepared. Its upper and lower electrodes are connected to the SMA converter head by cable to complete the electrical connection of the transducer. A hydrophobic protective film is sputtered on its surface to realize the preparation of the flexible piezoelectric ultrasonic transducer.

[0076] The flexible piezoelectric ultrasonic transducer prepared by the method provided in this embodiment can form a variety of focused sound field forms by dynamically adjusting its curvature, highlighting the advantages of the flexible piezoelectric ultrasonic transducer in flexible sound field control. It realizes active and efficient modulation of the ultrasonic sound field, opening up new prospects for active high-frequency sound field modulation and dynamic high-resolution ultrasonic applications.

[0077] Example 3

[0078] The following design scheme and related data provided in Embodiment 1 above were used to design a 1.5MHz high-performance flexible piezoelectric ultrasonic transducer with adjustable deformation curvature using Comsol software, and the performance of the flexible piezoelectric ultrasonic transducer was simulated.

[0079] First, the sound field patterns formed by the flexible transducer at curvature radii of 17.5 mm and 30 mm were simulated respectively. Based on the self-built hydrophone test system, the ultrasonic sound field formed by the transducer under the above two curvature radius deformations was characterized.

[0080] Specifically, a finite element simulation model is established, and through frequency domain simulation, two-dimensional cross-sections of the xy and xz planes within the focal region are extracted to represent the three-dimensional sound field formed under this state. The simulation results are as follows: Figure 5 As shown.

[0081] Secondly, to test the ultrasonic sound field generated by the transducer under the aforementioned two curvature radius deformations, the fabricated flexible ultrasonic transducer was attached to a 3D-printed mold, forming a specific bending curvature. A self-built hydrophone testing system was used, with 100μm steps to test the corresponding sound field pattern. The test results can be found in [reference needed]. Figure 6 .

[0082] Figure 5 and Figure 6 The results show that the flexible piezoelectric ultrasonic transducer provided by the present invention can achieve effective sound beam focusing and has good consistency with the simulation results.

[0083] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0084] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0085] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0086] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A flexible piezoelectric ultrasonic transducer, characterized by, The flexible electrode (11) and the 1-3 type composite piezoelectric element (12) are provided on the upper surface and the lower surface of the piezoelectric element (12); the 1-3 type composite piezoelectric element (12) and the flexible electrode (11) are both circular rings; the material of the flexible electrode (11) comprises a second flexible base material doped with metal powder particles; the metal powder particles comprise micron-sized silver powder particles, and the silver powder particles are spherical and single-dispersed; and the second flexible base material comprises PDMS. The 1-3 type composite piezoelectric element (12) is made of a first flexible base material and a 1-3 type composite piezoelectric material formed by cutting process based on piezoelectric ceramic; the piezoelectric ceramic is periodically arranged and embedded in the first flexible base material to form a plurality of piezoelectric columns; the width of the piezoelectric column is 200um-700um, the pitch of the piezoelectric column is 50um-200um, and the volume fraction of the piezoelectric phase is 30%-70%. The flexible electrode (11) is led out through a conductive cable (13) and combined with an external active control program through a connector (14), and the focal point position and the sound field shape of the focused sound beam can be dynamically changed by dynamically adjusting the form and curvature of the flexible piezoelectric ultrasonic transducer.

2. A flexible piezoelectric ultrasonic transducer according to claim 1, wherein, The first flexible base material comprises PDMS, and the material of the piezoelectric ceramic comprises PZT8.

3. A flexible piezoelectric ultrasonic transducer according to claim 1, wherein, The acoustic impedance of the flexible electrode (11) satisfies: wherein Z b represents the acoustic impedance of the flexible electrode, Z l represents the acoustic impedance of the front-end load, Z p represents the acoustic impedance of the composite piezoelectric material.

4. The flexible piezoelectric ultrasonic transducer of claim 1, wherein, The volume fraction of silver powder particles in the flexible electrode is 23.4%.

5. A method of making a flexible piezoelectric ultrasonic transducer, characterized by, The method comprises the following steps: Step 1: Prepare a piezoelectric ceramic sheet, and use a high-precision cutting machine to cut a cutting slot with consistent pitch and consistent groove depth on the piezoelectric ceramic sheet in the x-axis and y-axis directions to form periodically arranged piezoelectric columns; wherein the width of the piezoelectric column is 200um-700um, the pitch of the piezoelectric column is 50um-200um, and the volume fraction of the piezoelectric phase is 30%-70%; Step 2: Prepare a mixed solution of the first flexible base material; Step 3: Fill the mixed solution of the first flexible base material into the cutting slot of the cut piezoelectric ceramic sheet by siphon method, and solidify to form a flexible base, thereby obtaining a 1-3 type composite piezoelectric element; wherein the 1-3 type composite piezoelectric element is a circular ring; Step 4: Prepare a circular ring flexible electrode on the upper surface and the lower surface of the 1-3 type composite piezoelectric element to obtain a 1-3 type composite piezoelectric element with a flexible electrode; the material of the flexible electrode comprises a second flexible base material doped with metal powder particles; the metal powder particles comprise micron-sized silver powder particles, and the silver powder particles are spherical and single-dispersed; and the second flexible base material comprises PDMS; Step 5: Lead out the flexible electrode through a cable and combine it with an external active control program through a connector, thereby realizing the preparation of a flexible piezoelectric ultrasonic transducer; and dynamically changing the focal point position and the sound field shape of the focused sound beam by dynamically adjusting the form and curvature of the flexible piezoelectric ultrasonic transducer.

6. A method of fabricating a flexible piezoelectric ultrasonic transducer according to claim 5, wherein, Step 4 comprises: Step 4: The metal powder particles are doped into a mixture of the second flexible substrate material, after sufficient stirring, uniformly coated on the upper surface and the lower surface of the 1-3 type composite piezoelectric element, and cured to print the flexible electrode on the upper surface and the lower surface of the 1-3 type composite piezoelectric element, to obtain a 1-3 type composite piezoelectric element with a flexible electrode.

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