A flexible piezoelectric ultrasonic fiber transducer and a preparation method and application thereof

Abstract

The application relates to the field of flexible sensing fabric, and discloses a flexible piezoelectric ultrasonic fiber transducer and a preparation method and application thereof, the preparation method comprising the following steps: laminating two films A and B in the order of ABABA, wherein A is a non-conductive high polymer film, and B is a conductive high polymer film; laminating the films through hot pressing to obtain a hot-stretching preform which is internally coated with a piezoelectric ultrasonic circuit structure; fixing the hot-stretching preform in a low-temperature polymer drawing tower, feeding a wire through hot stretching to obtain the flexible piezoelectric ultrasonic fiber transducer. The flexible piezoelectric ultrasonic fiber transducer is prepared by coating a piezoelectric ultrasonic circuit system with a flexible non-conductive high polymer film, the non-conductive high polymer film can be used as a matching layer and a backing layer of the ultrasonic transducer system while serving as a coating layer, is non-toxic and harmless, has certain flexibility and stretchability, is wear-resistant, has good elasticity, and is easy to process and prepare.

Description

Technical Field

[0001] This invention relates to the field of flexible sensing fabrics, specifically to a flexible piezoelectric ultrasonic fiber transducer, its preparation method, and its application. Background Technology

[0002] With the continuous expansion of ultrasonic applications, research on piezoelectric materials and their applications is constantly evolving. Ultrasonic transducers, fabricated using piezoelectric materials as the core, combined with backing layers, matching layers, and conductive wires, can be applied in industries such as manufacturing, medicine, military, and clothing. Currently, ultrasonic sensors used in practical applications are generally rigid sensors, which are large, rigid, and cannot be bent. Rigid sensors cannot achieve complete coupling when used at workpiece angles or human joints, leading to errors in the detection results. Intelligent flexible ultrasonic transducers are flexible, small in size, and flexible, allowing for significant bending and stretching to perfectly conform to the workpiece or human body structure, minimizing interference signals. Therefore, developing a low-cost, continuously producible, and integrated ultrasonic transceiver fiber piezoelectric ceramic transducer while ensuring stable and excellent sensing performance has become a major research challenge.

[0003] Styrene-ethylene-butene-styrene block copolymer (SEBS) is a thermoplastic elastomer that can be used to modify plastics or blended into thermoplastic rubbers. SEBS exhibits excellent aging resistance, possessing both plasticity and high elasticity. It can be processed and used without vulcanization, and scraps can be reused. It is widely used in the production of high-grade elastomers, plastic modification, adhesives, lubricant tackifiers, and fillers and sheathing materials for wires and cables. It is also a suitable material for flexible wearable fiber coatings and is widely used in flexible wearable strain sensors, smart clothing, and other fields.

[0004] Carbon-doped polyethylene (CPE) is a carbon-doped polymer material that combines the heat resistance, corrosion resistance, thermoplasticity, and excellent electrical conductivity of polymer materials. In recent years, CPE has been widely used in optical sensing, brain-computer interfaces, ultrasonic transducers, and other applications. It is a widely used flexible electrode material in flexible wearable systems.

[0005] Yoel Fink et al. reported a flexible piezoelectric ultrasonic transducer fiber in their article "Multimaterial piezoelectric fibres" published in Nature Materials (Nature Materials, 2010, 9(8): 643-648). The fiber uses PC as the cladding layer, P(VDF-TrFE) as the piezoelectric ultrasonic material, and CPC and Indium as the conductive materials. It possesses a certain degree of flexibility and can be continuously fabricated. However, the PC and CPC materials used in the cladding layer and conductive polymer layer are somewhat brittle, making large-angle bending impossible. Furthermore, the piezoelectric fiber prepared by this method exhibits good performance in the audible sound range but relatively poor performance in the ultrasonic range.

[0006] The article "Flexible Piezoelectric Fibers for Acoustic Sensing and Positioning" published by Wei et al. in the journal Advanced Electronic Materials (Adv ElectMaterials, 2017, 3(3): 1600449.) describes a flexible piezoelectric ultrasonic fiber transducer for acoustic sensing and positioning, and its fabrication method. The transducer uses polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] as the piezoelectric element, sandwiching a P(VDF-TrFE) film between two layers of carbon-supported polyethylene (CPE) to ensure a large active area between the piezoelectric and conductive materials. A eutectic alloy bismuth-tin (BiSn) is selected as the metal electrode for connection to the external circuit. The entire structure is encapsulated between two rectangular polycarbonate (PC) blocks and hot-stretched into a preform. The flexible piezoelectric ultrasonic fiber transducer is fabricated by heating and stretching the preform using a low-temperature polymer drawing tower. The resulting fiber is both flexible and continuously processable, but its piezoelectric element is a piezoelectric polymer material, whose piezoelectric performance is inferior to that of piezoelectric ceramics and piezoelectric single crystal materials, which affects the ultrasonic transceiver performance. Summary of the Invention

[0007] Based on this, the present invention provides a method for fabricating a flexible piezoelectric ultrasonic fiber transducer. Addressing the application bottleneck of poor ultrasonic emission and sensing performance due to the low piezoelectric constant of the piezoelectric material within traditional polymer piezoelectric fibers, this invention develops a piezoelectric fiber device based on piezoelectric ceramics. The thermal drawing technique can integrate functional materials with different thermal, acoustic, electrical, and mechanical properties into a single fine fiber through a simple one-step thermal drawing process, and precisely control the material's intricate multi-scale structure, making it ideally suited for the integrated, large-scale fabrication of ultrasonic fibers.

[0008] To achieve the above objectives, the present invention provides a method for fabricating a flexible piezoelectric ultrasonic fiber transducer, comprising the following steps:

[0009] S1. Two types of films, A and B, are stacked in the order ABABA, where A is a non-conductive polymer film and B is a conductive polymer film. At the center of the non-conductive polymer film in the middle layer, several piezoelectric element grooves with through holes are arranged at intervals along its length. Piezoelectric elements are placed in the piezoelectric element grooves. The positive and negative electrodes of the piezoelectric elements are respectively attached to the conductive polymer films on both sides. Teflon wires are embedded in the conductive polymer films along the arrangement direction of the piezoelectric element grooves.

[0010] S2. After hot pressing, the Teflon wire is extracted from the preform to obtain a hot-stretched preform with an internal piezoelectric ultrasonic circuit structure and metal wire through holes.

[0011] S3. Fix the hot-stretched preform obtained in step S2 in a low-temperature polymer drawing tower, and feed the metal wire into the metal wire through hole through hot stretching to obtain a flexible piezoelectric ultrasonic fiber transducer.

[0012] As a further preferred embodiment of the present invention, the piezoelectric element is a piezoelectric ceramic material such as lead-containing piezoelectric ceramic (lead zirconate titanate, barium titanate, or lead titanate), lead-free piezoelectric ceramic (zinc oxide or barium strontium titanate), or a piezoelectric single crystal material such as binary piezoelectric single crystal (PMN-PT, PZN-PT), ternary piezoelectric single crystal (PMN-PIN-PT, PMN-PZ-PT), and the center frequency of the piezoelectric element is 1kHz-10MHz. The piezoelectric elements are arranged in single or multiple rows with a spacing of 0.1-10mm, and the size of the piezoelectric element is 0.0025cm. 2 -1 cm 2 More preferably, the length and width dimensions of the piezoelectric element range from 0.1 to 5 mm, and the height dimension is designed according to the required center frequency. Specifically: when the element width is less than 0.1 mm, the circuit system is prone to short circuits or open circuits due to the small size. After the element is encapsulated by polymer, the ultrasonic transmission and reception performance decreases, making it unsuitable for practical applications. Moreover, when the width is less than 0.1 mm, the ultrasonic half-wavelength is too small, and the spacing between piezoelectric elements needs to be controlled within a very small range to fully utilize its piezoelectric performance. When the element length is greater than 5 mm, although the ultrasonic signal will be greatly improved, due to the rigidity of the piezoelectric element, the excessively long element cannot take into account the flexible characteristics. In addition, its large half-wavelength will cause signals in several planes to be received and superimposed, reducing the detection quality.

[0013] As a further preferred embodiment of the present invention, the polymer material of the non-conductive polymer film is styrene-ethylene-butene-styrene block copolymer (SEBS), polycarbonate (PC), polymethyl methacrylate (PMMA), or polyetherimide (PEI). Since styrene-ethylene-butene-styrene block copolymer is a thermoplastic elastomer with excellent aging resistance, plasticity, and high elasticity, and can be processed and used without vulcanization, it can provide excellent elasticity, flexibility, and tensile cycle performance as the matching layer and backing layer of a piezoelectric ultrasonic system. Furthermore, other materials with good elasticity or flexibility, such as polycarbonate, polymethyl methacrylate, or polyetherimide, can be used as substitutes.

[0014] As a further preferred embodiment of the present invention, the polymer material of the conductive polymer film is carbon-doped polyethylene (CPE) or carbon-doped polycarbonate (CPC). Carbon-doped polyethylene is a carbon-doped polymer material that combines the heat resistance, corrosion resistance, thermoplasticity, and excellent conductivity of polymer materials, making it suitable as a flexible electrode in fibers. In addition, other conductive polymers, such as carbon-doped polycarbonate, can be used as alternatives.

[0015] As a further preferred embodiment of the present invention, the conductor is made of carbon fiber, copper wire, silver wire or tungsten wire, and even more preferably the conductor diameter is 20 to 50 μm.

[0016] As a further preferred technical solution of the present invention, the polymer raw material for preparing the film in step S1 needs to be dried before film formation, the drying time is 5 to 10 days, and the drying temperature is 60°C; the hot pressing temperature in step S2 is 105 to 160°C; and the thickness of the hot-stretched preform obtained in step S2 is 7 to 12 mm.

[0017] As a further preferred technical solution of the present invention, in step S3, the low-temperature polymer drawing tower is divided into three temperature zones. The hot-stretched preform is sequentially hot-stretched in the three temperature zones. The upper and lower temperature zones are controlled according to the physical properties of the preform and the surrounding environment, and the temperature of the middle temperature zone is set to 130-160℃. Specifically, when the temperature of the middle temperature zone is below 130℃, the preform cannot reach the softening temperature, and the polymer cannot be transformed into a viscous flow state for hot stretching and elongation to prepare fibers. When the temperature of the middle temperature zone is above 160℃, the preform is subjected to excessively high temperatures, resulting in reduced viscosity and making it impossible to stably prepare uniform fibers. This can easily lead to premature fiber breakage. Furthermore, excessively high temperatures can cause the piezoelectric constant (d33) and other properties of the ultrasonic element to degrade, which has a certain impact on the ultrasonic transmission and reception performance of the finally prepared flexible piezoelectric ultrasonic fiber transducer. Through experiments using different materials at different temperatures, it was finally found that a uniformly distributed and high-performance flexible piezoelectric ultrasonic fiber transducer can be obtained within the temperature range of 130-160℃.

[0018] As a further preferred technical solution of the present invention, in order to cover the interior of the hot-stretched preform with a conductive polymer film without exposing it, and to make the surface of the hot-stretched preform smooth after hot pressing, in step S1, conductive medium grooves adapted to the conductive polymer film (meaning the length, width and height dimensions are the same) are respectively opened on the non-conductive polymer film located in the middle layer and one of the non-conductive polymer films located on the outer layer, and the two conductive polymer films are respectively embedded in the conductive medium grooves; the conductive polymer film is also provided with metal wire grooves adapted to the wires, and the Teflon wire is embedded in the metal wire grooves before the hot-stretched preform is hot-pressed.

[0019] According to another aspect of the present invention, a flexible piezoelectric ultrasonic fiber transducer is also provided, which is prepared by the above-described method.

[0020] According to another aspect of the invention, the invention also provides an application of a flexible piezoelectric ultrasonic fiber transducer as a flexible sensing fabric, which is used to simultaneously transmit and receive ultrasonic waves at a fixed frequency. Specifically, the fiber transducer is woven into a fabric of appropriate size using a weaving method, thereby serving as an ultrasonic transducer fabric capable of real-time transmission and reception of ultrasonic signals for detecting defects in industrial workpieces, imaging human tissue, and non-invasive treatment.

[0021] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0022] 1) This invention uses a flexible, non-conductive polymer film to coat the fiber of the piezoelectric ultrasonic circuit system. The non-conductive polymer film can also serve as a matching layer and backing layer for the ultrasonic transducer system. It is non-toxic and harmless, has a certain degree of flexibility and extensibility, is wear-resistant, has good elasticity, and is easy to process and prepare.

[0023] 2) The flexible piezoelectric ultrasonic fiber transducer prepared by the present invention has a stable structure, good flexibility, can achieve large-angle bending, and can simultaneously transmit and receive ultrasonic signals in real time. It has a wide range of applications, such as as a flexible sensing fabric.

[0024] 3) The flexible piezoelectric ultrasonic fiber transducer prepared by this invention adopts a conventional hot stretching process, which is cost-controllable, mature, and can be industrialized for continuous production. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a schematic diagram of the structure of the hot-drawn preform of the flexible piezoelectric ultrasonic fiber transducer of the present invention before hot pressing.

[0027] Figure 1 In the middle: 1. Matching layer; 2. Teflon wire; 3. Conductive medium; 4. Piezoelectric element; 5. Insulating layer; 6. Backing layer; 7. Conductive medium groove; 8. Metal wire groove; 9. Ultrasonic element groove.

[0028] Figure 2 A physical image (a) and an enlarged image (b) of the flexible piezoelectric ultrasonic fiber transducer prepared in Example 1.

[0029] Figure 3 The image shows the ultrasonic emission performance test results of the flexible piezoelectric ultrasonic fiber transducer prepared in Example 1.

[0030] Figure 4 The image shows the ultrasonic receiving performance test results of the flexible piezoelectric ultrasonic fiber transducer prepared in Example 1.

[0031] Figure 5 The ultrasonic emission spectrum of the flexible piezoelectric ultrasonic fiber transducer prepared in Example 1.

[0032] Figure 6 The piezoelectric constants of 1-3PZT piezoelectric ceramics were tested after heating at different temperatures for 30 minutes.

[0033] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0036] The following explanation and implementation will use 1-3PZT piezoelectric ceramic (Japan Fine Geramigs Go.LTO PZT-Pb(Zr·Ti)O3-C-201), copper wire (Cu, Goodfellow CU00-WR-000115), carbon-doped polyethylene (CPE, Hillas LAD 5710), and styrene-ethylene-butene-styrene block copolymer (SEBS, Karton G1657) as preferred raw materials.

[0037] like Figure 1As shown, the following embodiment uses 1-3PZT piezoelectric ceramic as the piezoelectric element 4. It has a high piezoelectric constant and a rigid structural characteristic, exhibiting excellent piezoelectric ultrasonic performance. The 1-3 composite structure formed with epoxy resin can achieve impedance matching with the coupling agent, making it a commonly used piezoelectric ceramic material in ultrasonic transducers. The 1-3PZT piezoelectric ceramic is embedded in a SEBS film serving as the insulating layer 5. Carbon-doped polyethylene (CPE) is used as the conductive medium 3 to completely bond the positive and negative electrodes of the piezoelectric element 4, ensuring stable reception of ultrasonic electrical signals. Copper wires are embedded in a conductive polymer as conductors to ensure electrical signal transmission. Finally, two SEBS films are used to cover the front and back sides as a matching layer 1 and a backing layer 6, completely covering the conductive medium 3. In practical applications, encapsulation layers can also be laminated on the outside of the matching layer 1 and the backing layer 6 for encapsulation. The encapsulation layer material can be a film of SEBS, PC, PMMA, or PEI.

[0038] A thermo-stretched preform was prepared using 1-3PZT piezoelectric ceramic as the piezoelectric element, SEBS film as the insulating layer 5, matching layer 1, and backing layer 6, CPE as the conductive medium 3, and copper wire as the conductor. Figure 1 After being heated by a low-temperature polymer drawing tower and stretched, CPE and copper wire are tightly bonded to the piezoelectric element through stretching to obtain a complete current path. SEBS is stretched to tightly wrap the ultrasonic circuit system, and finally a flexible piezoelectric ultrasonic fiber transducer is obtained. By leading out circuits at both ends of the fiber and connecting them to signal generators and waveform generators, ultrasonic signals can be emitted and received through the fiber.

[0039] Example 1

[0040] The fabrication method of the flexible piezoelectric ultrasonic fiber transducer in this embodiment is as follows:

[0041] Step 1: Preparation of hot-stretched preforms:

[0042] 1) The SEBS raw material was vacuum dried in an oven at 60℃ for 7 days, and then hot-pressed at 160℃ to obtain a 2mm thick SEBS film. This film was then cut into three 20×200mm rectangular films. Ten square ultrasonic element grooves with dimensions of 0.5×0.5mm, a depth of 0.4mm, and a spacing of 1mm were engraved along the length of one SEBS film. A rectangular conductive dielectric groove with dimensions of 8×180mm and a depth of 1.6mm was engraved at the center of the back of the film. This SEBS film serves as the insulating layer. A rectangular conductive dielectric groove with dimensions of 8×180mm and a depth of 1.6mm was engraved along the length of another SEBS film. This SEBS film serves as the matching layer. The remaining SEBS film serves as the backing layer.

[0043] 2) The CPE raw material was vacuum dried in an oven at 60℃ for 7 days, and then hot-pressed at 105℃ to obtain a CPE film with a thickness of 1.6mm. The film was cut into two rectangular films of 8×180mm as conductive medium. A rectangular metal wire groove with a length and width of 1×180mm and a depth of 1mm was engraved in the center of the film along the length direction.

[0044] 3) The conductive medium 3 is embedded in a rectangular conductive medium groove 7, the piezoelectric element 4 (0.4×0.4×0.28mm) is embedded in a square ultrasonic element groove 9, and the 1mm diameter Teflon wire 2 is embedded in a rectangular metal wire groove 8. The SEBS film and CPE film are stacked in an ABABA configuration (A is the SEBS film, B is the CPE film). The outermost two SEBS films are the matching layer 1 and the backing layer 6, respectively, and the middle SEBS film is the insulating layer. Then, it is pressed in a hot press at 105°C. The specific structure is as follows. Figure 1 As shown, the Teflon wire 2 is finally pulled out to obtain a hot-drawn preform (also known as a preform rod). Pulling out the Teflon wire 2 creates through-holes in the hot-drawn preform for subsequent wire feeding.

[0045] Step 2: High-temperature hot stretching to prepare fibers

[0046] A hot-stretched preform was fixed in a low-temperature polymer drawing tower. The upper temperature zone was set at 120℃, the middle temperature zone at 215℃, and the lower temperature zone at 60℃. After heating for 18 minutes, the preform transformed into a viscous flow state and underwent stretching and thinning. By setting the bar feeding speed to 1 mm / min and the traction speed to 0.4 m / min, a hot-stretch ratio of 1:20 was achieved. Simultaneously, copper wire was fed into the metal wire through-hole along with the fiber stretching process, ultimately resulting in a flexible piezoelectric ultrasonic fiber transducer. The fiber's morphology is as follows: Figure 2 As shown.

[0047] It should be noted that the copper wire is fed into the final fiber transducer during the hot-drawing process of the hot-drawn preform; this operation is a conventional technique and will not be described in detail here. In this invention, embedding a 1mm diameter Teflon wire into the metal wire groove during hot pressing is to prevent the metal wire groove from collapsing during hot pressing. After hot pressing, the Teflon wire can be pulled out, resulting in a through-hole for the metal wire at the location of the metal wire groove.

[0048] In this embodiment, a commercial ultrasonic probe (Olympus 5MHz) was used as the transmitting or receiving module in the test system for the flexible piezoelectric ultrasonic fiber transducer. A signal generator (Keysight 33500B) was used to provide electrical signals to the piezoelectric ultrasonic fiber or the commercial ultrasonic probe. A broadband amplifier (Aigtek ATA-1200C) and a digital oscilloscope (SiglentSDS1202X-E) were used to characterize the ultrasonic signals received by the piezoelectric ultrasonic fiber or the commercial ultrasonic probe. The results are as follows:

[0049] (1) The flexible piezoelectric ultrasonic fiber transducer and the commercial ultrasonic probe were completely immersed in deionized water to achieve coupling between the fiber and the probe. The fiber was excited with a 5MHz AC signal to emit ultrasonic waves. The distance between the fiber and the commercial probe was maintained at 5mm. The output voltage of the signal generator was 5Vpp, which was then applied to the fiber after passing through a widescreen amplifier with a gain of 20dB. The ultrasonic signal received by the commercial probe was characterized using a digital oscilloscope, such as... Figure 3 This indicates that the flexible ultrasonic piezoelectric fiber transducer has good ultrasonic emission performance and can be applied in practical scenarios through structural weaving.

[0050] (2) The flexible piezoelectric ultrasonic fiber transducer and the commercial ultrasonic probe were completely immersed in deionized water to achieve coupling between the fiber and the probe. A 5MHz AC signal was used to excite the commercial ultrasonic probe, causing it to emit ultrasonic waves. The distance between the fiber and the commercial probe was maintained at 5mm. The output voltage of the signal generator was 6Vpp, which was then applied to the commercial probe after passing through a widescreen amplifier with a gain of 20dB. The ultrasonic signal received by the fiber was characterized using a digital oscilloscope, such as... Figure 4 This indicates that the flexible ultrasonic piezoelectric fiber transducer has good ultrasonic receiving performance and can be applied in practical scenarios through structural weaving.

[0051] (3) The flexible piezoelectric ultrasonic fiber transducer and the commercial ultrasonic probe were bonded to both sides of a standard test block using a coupling agent. The fiber was excited by an AC signal of 3.5-6MHz to emit ultrasonic waves. The thickness of the test block between the fiber and the commercial probe was 50mm, and the input voltage was 60Vpp. Based on the characterization of the fiber's spectral data using a digital oscilloscope, such as... Figure 5 This indicates that the center frequency of the flexible ultrasonic piezoelectric fiber transducer is around 5MHz, and the center frequency did not shift significantly after the piezoelectric element was thermally drawn into the fiber.

[0052] The 1-3PZT piezoelectric ceramic in the flexible ultrasonic piezoelectric fiber transducer prepared in this embodiment exhibits high-temperature resistance, and its high-temperature resistance performance was tested. Figure 6 The piezoelectric constants of 1-3PZT piezoelectric ceramics were measured after heating at different temperatures for 30 min. At room temperature, the d33 of the PZT piezoelectric ceramic sample was 540 × 10⁻⁶. -12 C / N, after heating at 170℃ for 30 min, d33 decreased to 350×10. -12 C / N retains 64.814% of the properties of the raw materials, can withstand the temperature of the preform during hot stretching, and still maintains a high advantage over traditional piezoelectric polymer acoustic fibers.

[0053] Example 2

[0054] The fiber transducer was prepared using a method essentially the same as in Example 1, except that the hot stretching process parameters in step 2 were different. Specifically, the temperature of the low-temperature polymer drawing tower was set to 120°C in the upper zone, 210°C in the middle zone, and 60°C in the lower zone. After heating for 25 minutes, the preform was transformed into a viscous flow state and stretched to become thinner. By setting the bar feeding speed to 1 mm / min and the traction speed to 0.4 m / min, the hot stretching ratio was 1:20. At the same time, copper wire was fed into the fiber along with the fiber stretching process.

[0055] Example 3

[0056] The fiber transducer was prepared using a method essentially the same as in Example 1, except that the hot stretching process parameters in step 2 were different. Specifically, the temperature of the low-temperature polymer drawing tower was set to 110°C in the upper zone, 235°C in the middle zone, and 50°C in the lower zone. After heating for 9 minutes, the preform was transformed into a viscous flow state and stretched to become thinner. By setting the bar feeding speed to 1 mm / min and the traction speed to 0.4 m / min, the hot stretching ratio was 1:20. At the same time, copper wire was fed into the fiber along with the fiber stretching process.

[0057] Example 4

[0058] The fiber transducer was prepared using a method that was basically the same as in Example 1, except that the piezoelectric element in step 1 was different. Specifically, a 1-3PMN-PT piezoelectric single crystal (0.4×0.4×0.28mm) was used as the ultrasonic element to prepare a hot-drawn preform.

[0059] A comprehensive comparison of the different flexible piezoelectric ultrasonic fiber transducers prepared in the above embodiments is shown in Table 1. Compared with Embodiment 1, Embodiments 2, 3 and 4 also have good ultrasonic wave transmission and reception performance. In addition, the fibers have good flexibility and can also meet the weaving requirements.

[0060] Table 1. Performance comparison of flexible piezoelectric ultrasonic fiber transducers prepared with different parameters

[0061] Example 1 Example 2 Example 3 Example 4 Mid-temperature zone temperature 215℃ 210℃ 235℃ 215℃ Initial heating time 18min 25min 9min 15min Fiber diameter 1.5 mm 3 mm 0.8mm 1mm piezoelectric constant <![CDATA[350×10 -12 C / N]]> <![CDATA[380×10 -12 C / N]]> <![CDATA[300×10 -12 C / N]]> <![CDATA[650×10 -12 C / N]]>

[0062] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for fabricating a flexible piezoelectric ultrasonic fiber transducer, characterized in that, Includes the following steps: S1. Two types of films, A and B, are stacked in the order ABABA, where A is a non-conductive polymer film and B is a conductive polymer film. At the center of the non-conductive polymer film in the middle layer, several piezoelectric element slots with through-hole structures are arranged at intervals along its length. Piezoelectric elements are placed in these slots, and the positive and negative electrodes of the piezoelectric elements are respectively bonded to the conductive polymer films on both sides. Teflon wires are embedded in the conductive polymer films, arranged along the arrangement direction of the piezoelectric element slots. Both the non-conductive polymer film in the middle layer and one of the non-conductive polymer films on the outer layer have conductive medium grooves adapted to the conductive polymer film. The two conductive polymer films are respectively embedded in the conductive medium grooves. The conductive polymer film has metal wire grooves adapted to the wires. Before the hot-stretched preform is hot-pressed, the Teflon wire is embedded in the metal wire grooves. The piezoelectric element is a piezoelectric ceramic material or a piezoelectric single crystal material, and the center frequency of the piezoelectric element is 1 kHz-10 MHz; S2. After hot pressing, the Teflon wire is extracted from the film stacked in step S1 to obtain a hot-stretched preform with an internal piezoelectric ultrasonic circuit structure and metal wire through-holes. S3. Fix the hot-stretched preform obtained in step S2 in a low-temperature polymer drawing tower, and feed the wire into the metal wire through hole through the hot stretching process to obtain a flexible piezoelectric ultrasonic fiber transducer.

2. The method for preparing the flexible piezoelectric ultrasonic fiber transducer according to claim 1, characterized in that, The piezoelectric elements are arranged in single or multiple rows with a spacing of 0.1-10 mm, and the size of the piezoelectric element is 0.0025 cm. 2 -1 cm 2 .

3. The method for preparing the flexible piezoelectric ultrasonic fiber transducer according to claim 1, characterized in that, The polymer material of the non-conductive polymer film is styrene-ethylene-butene-styrene block copolymer, polycarbonate, polymethyl methacrylate or polyetherimide, and the polymer material of the conductive polymer film is carbon-doped polyethylene or carbon-doped polycarbonate.

4. The method for preparing the flexible piezoelectric ultrasonic fiber transducer according to claim 1, characterized in that, The conductor is made of carbon fiber, copper wire, silver wire, or tungsten wire.

5. The method for preparing the flexible piezoelectric ultrasonic fiber transducer according to claim 4, characterized in that, The diameter of the conductor is 20~50 μm.

6. The method for preparing the flexible piezoelectric ultrasonic fiber transducer according to claim 1, characterized in that, In step S3, the low-temperature polymer drawing tower is divided into three temperature zones, and the hot-stretched preform is sequentially hot-stretched in the three temperature zones, with the temperature zone set to 130~160 ℃.

7. A flexible piezoelectric ultrasonic fiber transducer, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the flexible piezoelectric ultrasonic fiber transducer of claim 7 as a flexible sensing fabric, characterized in that, The flexible piezoelectric ultrasonic fiber transducer is used to transmit and receive ultrasonic waves at a fixed frequency.

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