A self-absorbing flexible ultrasonic patch

Abstract

This invention provides a self-adhesive flexible ultrasonic patch, solving the problems of unstable probe fixation and poor adhesion in existing pipeline inspection methods. The patch includes a flexible ultrasonic transducer assembly, which is composed of an 8*16 unit array and a multi-layer composite structure consisting of a matching layer, a piezoelectric layer, a backing layer, and an encapsulation layer. The matching layer is a composite material of PDMS-doped graphene and tungsten powder; the piezoelectric layer is a PZT-5H piezoelectric column array; the backing layer is a magnetic sound-absorbing composite material of PDMS-doped tungsten powder, porous graphene, and neodymium iron boron nanoparticles; and the encapsulation layer is a pure PDMS integrated encapsulation. This invention integrates magnetic adsorption functionality into the backing layer, enabling rapid, non-destructive installation and stable contact between the patch and the pipeline. Utilizing a flexible multi-layer structure to adapt to pipeline curvature, it combines excellent surface adaptability with ultrasonic testing performance, making it suitable for wall thickness detection and long-term monitoring of metal pipelines. It is easy to install and highly stable.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic sensor technology, and more specifically to a self-absorbing flexible ultrasonic patch. Background Technology

[0002] An ultrasonic transducer is a core component for converting acoustic energy into electrical energy. When a piezoelectric material is excited by an electrical signal, it generates mechanical vibration and radiates ultrasonic waves outward. Conversely, when ultrasonic waves act on a piezoelectric material, they generate electrical signal output.

[0003] Ultrasonic testing, with its advantages of being non-radioactive, non-destructive, and widely applicable, has extremely high application value in pipe wall thickness measurement, pipe defect detection, and weld quality assessment. Currently, handheld probes are more commonly used in pipe measurement. However, handheld probes rely on manual operation, have poor stability, low detection efficiency, and are difficult to use for long-term monitoring.

[0004] To address the issue of ultrasonic transducer fixation and achieve reliable installation and long-term monitoring, some existing technologies employ magnetic adsorption and mechanical fixing methods such as straps. The former utilizes the magnetic attraction between the transducer and the pipe to achieve non-destructive installation, removal, and fixation. However, this approach typically uses a rigid shell structure, preventing pipe bending and resulting in mostly point contact with the pipe wall. This makes it difficult to achieve a tight fit to the curved surface and stable acoustic coupling, leading to low detection efficiency.

[0005] The mechanical fastening method using straps involves wrapping the strap around the tube once and adjusting the tightness to achieve repeated installation and removal. However, in practical applications, the tube-wrapping operation is cumbersome, and the binding force is difficult to control precisely, leading to poor coupling. Summary of the Invention

[0006] To address the problems of unstable fixation, poor fit, and low acoustic coupling efficiency of ultrasonic probes in existing pipeline monitoring systems, this invention proposes a self-absorbing flexible ultrasonic patch and its preparation method. By combining new materials and processes, the acoustic performance of the ultrasonic patch is improved.

[0007] The self-priming flexible ultrasonic patch includes a flexible ultrasonic transducer assembly. The flexible ultrasonic transducer is composed of multiple independent transducer units arranged in an array. Each transducer unit employs a multi-layer composite structure, consisting of a matching layer (A), a piezoelectric layer (B), a backing layer (C), and an encapsulation layer (D). To adapt to the curved surfaces of pipes, all functional layers in the transducer are constructed based on flexible polymer materials.

[0008] The matching layer (A) is disposed on the outermost side of the patch and is used to contact the outer wall of the pipe to achieve acoustic impedance matching. The matching layer (A) is composed of a composite material of polydimethylsiloxane (PDMS) doped with graphene and tungsten powder. PDMS serves as a flexible matrix to ensure the patch's flexibility; graphene is used to adjust acoustic properties and improve the uniformity of filler dispersion in the PDMS matrix; and tungsten powder is used to adjust the acoustic impedance, regulate the acoustic impedance matching between the piezoelectric material and the pipe, and ensure the transmission efficiency of sound waves.

[0009] The piezoelectric layer (B) is embedded between the matching layer (A) and the backing layer (C) to achieve the conversion between electrical energy and acoustic energy. The piezoelectric layer (B) is composed of lead zirconate titanate piezoelectric ceramic (PZT-5H). PZT-5H is known for its extremely high piezoelectric coefficient, excellent electromechanical coupling efficiency, and superior sensitivity. To maintain overall flexibility, the piezoelectric layer (B) employs a multi-piezoelectric pillar array structure, ensuring a high piezoelectric constant while reducing bending stiffness.

[0010] The backing layer (C) is located above the piezoelectric layer (B). It suppresses the residual vibration of the piezoelectric element through high damping, shortens the ultrasonic pulse width, and improves axial resolution. Simultaneously, it absorbs acoustic wave energy radiated towards the back, preventing interference artifacts. The backing layer (C) is composed of a magnetic sound-absorbing composite material, including polydimethylsiloxane (PDMS), tungsten powder, porous graphene, and neodymium iron boron nanoparticles dispersed in the matrix. The PDMS serves as a flexible matrix, ensuring the patch's flexibility; the tungsten powder achieves acoustic impedance matching with the piezoelectric layer (B), reducing acoustic wave interface reflection; the porous graphene has a porous structure, improving the uniformity of filler dispersion in the matrix and enhancing the multiple scattering and attenuation effect of acoustic waves within the composite material; the neodymium iron boron nanoparticles, as magnetic functional fillers, are uniformly dispersed in the matrix, giving the backing layer (C) magnetism and generating magnetic attraction. The magnetic attraction force enables the patch to be self-adhesive and fixed, providing initial contact pressure between the patch and the pipe surface, compensating for the gaps caused by the curved surface fitting, and achieving good acoustic coupling.

[0011] The encapsulation layer (D) covers the outer surface of the backing layer (C) and provides electrical insulation, mechanical protection and environmental sealing; the encapsulation layer (D) is made of pure polydimethylsiloxane (PDMS) to ensure good flexibility and biocompatibility.

[0012] In the array arrangement, the transducers are arranged in an 8*16 configuration, totaling 128 units. Gaps are maintained between each transducer unit to ensure that the units can move without interference when the transducers are operating on non-curved pipes.

[0013] The self-absorbing flexible ultrasonic patch of the present invention employs the following process in its fabrication: a layer-by-layer molding and composite process is used in each functional layer. In the matching layer (A) and the backing layer (C) containing high-density fillers, ultrasonic dispersion is used to pretreat the mixed slurry, ensuring uniform dispersion of graphene, tungsten powder, porous graphene, and NdFeB nanoparticles within their respective PDMS flexible substrates. During the curing process of the backing layer (C), an external magnetic field perpendicular to the plane is applied, causing the NdFeB nanoparticles to align along the thickness direction.

[0014] This invention is used to detect pipe wall thickness. Its working principle is as follows: The operator holds the ultrasonic patch close to the outer wall of the pipe. Under the magnetic attraction of the magnetic adsorption unit, the ultrasonic patch is automatically adsorbed and adheres tightly to the pipe surface. Due to the overall flexibility of the patch, the entire patch completely conforms to the pipe, achieving efficient sound energy transmission. During detection, the piezoelectric layer (B) is excited by an electrical signal to generate ultrasonic waves, which are incident on the pipe wall through the matching layer (A). The waves are reflected back to the piezoelectric layer (B) and converted into an electrical signal. The pipe wall thickness is calculated based on the echo time.

[0015] In summary, compared with the prior art, this application includes at least one of the following beneficial technical effects: 1. The magnetic adsorption function is integrated into the backing layer (C) material, so that the backing layer (C) has both sound absorption and magnetic adsorption functions. The magnetic force provides stable contact pressure for the patch, replacing hand operation, solving the pain point of traditional flexible patches relying on adhesive or external clamps, simplifying the device structure and improving the flexibility of the transducer. 2. By constructing a matching layer (A) and a backing layer (C) using PDMS matrix doped with functional fillers, the entire patch can bend and conform to pipes of different diameters, while also possessing excellent surface adaptability and acoustic performance. The doping of graphene and tungsten powder in the matching layer (A) achieves good acoustic impedance matching, ensuring sufficient sound wave transmission efficiency; the addition of tungsten powder, porous graphene, and neodymium iron boron nanoparticles in the backing layer (C) enhances sound attenuation while providing magnetic attraction. Attached Figure Description

[0016] Figure 1 This is an exploded view of the overall structure of the present invention.

[0017] Figure 2 This is a side view of the transducer unit structure of the present invention.

[0018] Figure 3 This is a schematic diagram illustrating the magnetic field orientation principle of the backing layer of the present invention.

[0019] Figure 4 This is a schematic diagram of the measurement process according to the present invention.

[0020] Reference numerals: A - Matching layer; B - Piezoelectric layer; C - Backing layer; D - Encapsulation layer. Detailed Implementation

[0021] To make the technical means, inventive features, and achieved objectives and effects of the present invention easier to understand, the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the accompanying drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0022] For reference Figure 1 As shown, this embodiment provides a flexible ultrasonic patch for measuring pipe wall thickness, including a flexible ultrasonic transducer assembly.

[0023] The flexible ultrasonic transducer consists of multiple independent transducer units arranged in an array. Each transducer unit employs a multi-layer composite structure, consisting of an encapsulation layer (D), a backing layer (C), a piezoelectric layer (B), and a matching layer (A) stacked from top to bottom. The layers are tightly bonded together through a curing process, forming a single, flexible sheet-like structure capable of adapting to the curved surface of the pipe wall. In this example, the transducer units are arranged in an 8-row x 16-column configuration, totaling 128 units, ensuring that the patch can move relatively independently when bent.

[0024] The transducer unit structure of the present invention is as follows: Figure 2 As shown.

[0025] The matching layer (A) is located at the bottom of the patch and comes into direct contact with the outer wall of the pipe during use. In this example, the matching layer (A) is composed of a composite material of polydimethylsiloxane (PDMS) matrix doped with graphene and tungsten powder. PDMS acts as a flexible matrix, giving the matching layer (A) good flexibility to adapt to changes in the curvature of the pipe surface; the addition of graphene improves the acoustic properties of the material and enhances the uniformity of filler dispersion within the PDMS matrix; while tungsten powder is used to increase the material density and improve the acoustic impedance. DOS is Dow Corning Sylgard 184; the tungsten powder is spherical; and the graphene is multilayer nanosheets.

[0026] Appropriate acoustic impedance adjustment is the core of the matching layer (A) design. To achieve acoustic impedance adjustment, the acoustic impedance of the matching layer (A) should be between that of PZT-5H (approximately 30 M Nayl) and that of the pipe steel (approximately 45 M Nayl), maintaining flexibility as much as possible while reducing interface reflection. The perfect acoustic impedance of the matching layer (A) is approximately 36.7 M Nayl, which requires the addition of a large amount of tungsten powder. However, a large amount of tungsten powder will severely reduce the material's flexibility and its ability to conform to curved surfaces.

[0027] While ensuring sufficient sound transmission efficiency, the volume fraction of tungsten powder used in this invention results in a slightly lower acoustic impedance value for the matching layer (A) than the theoretical value, but it still maintains a certain degree of flexibility to adapt to pipe surfaces with different curvatures. Simultaneously, the stable contact provided by magnetic attraction compensates for the loss of acoustic performance, ensuring a tight fit between the matching layer (A) and the pipe surface, eliminating air gaps, and achieving a coupling effect.

[0028] In the preparation process, the PDMS main agent and curing agent are first mixed and stirred evenly at a mass ratio of 10:1. Then, a certain amount of tungsten powder and graphene are added in sequence, and the mixed slurry is treated by ultrasonic dispersion process. After being evenly dispersed in the PDMS matrix, vacuum degassing is performed, and the mixture is pre-cured to a semi-solid state for later use.

[0029] The piezoelectric layer (B), embedded between the matching layer (A) and the backing layer (C), is the core transducer component of this invention. In this example, the piezoelectric layer (B) is made of lead zirconate titanate piezoelectric ceramic material (PZT-5H), which has an extremely high piezoelectric coefficient, excellent electromechanical coupling efficiency, and superior sensitivity, and is one of the most widely used materials in current ultrasonic transducers.

[0030] Since PZT-5H is rigid, in order to maintain high piezoelectric performance while conforming to pipe surfaces with different curvatures, the piezoelectric layer (B) adopts a micro-piezoelectric column array structure. Each piezoelectric element remains independent, thereby achieving extremely low bending stiffness and maintaining a high piezoelectric constant. The upper and lower surfaces of the piezoelectric layer (B) of the transducer unit are connected by electrode leads to achieve excitation and signal acquisition.

[0031] The PZT-5H piezoelectric ceramic preform is cut into a micro piezoelectric column array. Each piezoelectric column is independent and has a uniform spacing. Metal electrodes are plated on the upper and lower surfaces. After the electrode leads are led out, the piezoelectric column array is embedded in the reserved position between the semi-solid matching layer (A) and the backing layer (C). Pressure is applied and the column is then cured.

[0032] A backing layer (C) covers the piezoelectric layer (B). In this example, the backing layer (C) has both sound absorption and magnetic adsorption functions. The backing layer (C) is composed of a composite material of polydimethylsiloxane (PDMS) matrix doped with tungsten powder, porous graphene, and neodymium iron boron nanoparticles. The PDMS is also Dow Corning Sylgard 184, the tungsten powder is spherical, and the porous graphene is graphene powder with a nanoscale pore structure on its surface.

[0033] The tungsten powder in the backing layer (C) can improve the material density and acoustic attenuation characteristics, effectively absorb the acoustic wave energy radiated from the piezoelectric layer (B) and suppress residual vibrations, thus shortening the ultrasonic pulse width. The addition of porous graphene can ensure sufficient acoustic attenuation. Neodymium iron boron nanopowder dispersed in the matrix can generate magnetic attraction to the outer wall of the pipe, realizing the adsorption and fixation of the patch and providing a stable initial contact pressure. At the same time, because each transducer unit is small in size, it can have good bending ability; the units remain separated and move independently; with PDMS as a flexible matrix, the backing layer (C) can maintain good surface adaptability.

[0034] In the preparation process, PDMS main agent and curing agent are first mixed and stirred evenly at a mass ratio of 10:1. Then, tungsten powder porous graphene and NdFeB nanoparticles are added sequentially. Due to the high density of the filler and the tendency of the nanoparticles to agglomerate, an ultrasonic dispersion process is used to treat the mixed slurry. The cavitation effect is used to break up the filler agglomerates, so that the various additives are uniformly and stably suspended in the PDMS matrix. Subsequently, vacuum degassing is performed to remove air bubbles from the mixture, and the mixture is poured into a pre-set mold using a casting molding process. During the curing process, an external magnetic field is applied to the plane perpendicular to the backing layer (C) to align the NdFeB nanoparticles along the thickness direction. After pre-curing to a semi-solid state, it is bonded and cured with the piezoelectric layer (B) to complete the composite of the backing layer (C) and the piezoelectric layer (B).

[0035] The schematic diagram of the magnetic field orientation principle of the backing layer of the present invention is as follows: Figure 3 As shown.

[0036] The encapsulation layer (D) covers the outermost layer of the backing layer (C) and is an integrated encapsulation of the entire array. In this example, the encapsulation layer (D) is made of pure polydimethylsiloxane (PDMS) material, covering all transducer units to form a continuous, monolithic encapsulation layer (D). PDMS has good flexibility and biocompatibility. Its main functions are to provide electrical insulation, mechanical protection, and environmental sealing. It can effectively prevent moisture and dust from entering the internal circuitry, avoiding moisture or corrosion. At the same time, the encapsulation layer (D) can also protect and buffer the internal structure, dispersing stress and protecting it from damage.

[0037] After mixing and stirring the PDMS evenly and degassing it under vacuum, the mixture is evenly poured onto the composite transducer unit array to ensure that the mixture fully covers all structures without gaps, and then cured at room temperature.

[0038] This invention is used in conjunction with a 128-phase array detector. In use, the patch electrode leads are connected to the corresponding channel of the detector. The operator holds the patch close to the outer wall of the pipe; under magnetic attraction, the patch is automatically adsorbed onto the pipe surface. The transducer receives a high-voltage pulse signal, which excites the piezoelectric layer (B) to generate ultrasonic waves. The ultrasonic waves are incident on the pipe wall through the matching layer (A), reflected by the inner wall, and transmitted back to the transducer unit. The transducer receives the signal and converts it into an electrical signal. Based on the acquired waveform, the echo time is extracted, and the wall thickness is calculated using the formula d=(v*t) / 2.

[0039] The measurement schematic diagram of the present invention is shown below. Figure 4 As shown.

[0040] This invention achieves the unity of surface adaptability and ultrasonic testing performance through multi-level collaborative design. The design of "appropriate material optimization + structural flexibility + pressure compensation performance" enables the patch to have both excellent pipe surface fit and good ultrasonic testing performance.

[0041] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A self-absorbing flexible ultrasonic patch, characterized in that, The system includes a flexible ultrasonic transducer assembly, wherein the flexible ultrasonic transducer is composed of multiple independent transducer units arranged in an array, with gaps between each transducer unit to allow each transducer unit to move relatively independently. Each of the transducer units adopts a multi-layer composite structure, including a matching layer (A), a piezoelectric layer (B), a backing layer (C), and an encapsulation layer (D); The matching layer (A) is used to contact the outer wall of the pipe under test to achieve acoustic impedance matching; The piezoelectric layer (B) is used to realize the conversion of electrical energy into acoustic energy; The backing layer (C) has the dual functions of acoustic backing and magnetic adsorption. It is used to absorb the sound waves radiated in the back, suppress residual vibration, and generate magnetic attraction to make the patch adhere to the outer wall of the pipe being tested and provide initial contact pressure. The encapsulation layer (D) is used to provide electrical insulation, mechanical protection and environmental sealing.

2. The self-absorbing flexible ultrasonic patch according to claim 1, characterized in that, The matching layer (A) is composed of a composite material of polydimethylsiloxane doped graphene and tungsten powder; The piezoelectric layer (B) is made of lead zirconate titanate piezoelectric ceramic material and adopts a multiple piezoelectric pillar array structure; The backing layer (C) is composed of a magnetic sound-absorbing composite material of polydimethylsiloxane doped with tungsten powder, porous graphene and neodymium iron boron nanoparticles. The encapsulation layer (D) is made of polydimethylsiloxane material.

3. The self-absorbing flexible ultrasonic patch according to claim 1, characterized in that, The transducer units are arranged in an 8*16 configuration, totaling 128 units.

4. The self-absorbing flexible ultrasonic patch according to claim 1, characterized in that, The piezoelectric layer (B) is made of lead zirconate titanate piezoelectric ceramic PZT-5H, and its surface is provided with electrode leads for excitation and signal acquisition.

5. The self-absorbing flexible ultrasonic patch according to claim 2, characterized in that, The porous graphene in the backing layer (C) has a nanoscale pore structure on its surface, which has a high attenuation effect.

6. The self-absorbing flexible ultrasonic patch according to claim 2, characterized in that, The neodymium iron boron nanopowder in the backing layer (C) is oriented along the thickness of the backing layer under the action of an external magnetic field, forming an ordered chain structure.

7. The self-absorbing flexible ultrasonic patch according to claim 1, characterized in that, The acoustic impedance of the matching layer (A) is between that of the piezoelectric layer and the acoustic impedance of the pipe steel, and the interface coupling loss is compensated by the magnetic attraction pressure provided by the backing layer (C).

8. The self-absorbing flexible ultrasonic patch according to claim 1, characterized in that, The encapsulation layer (E) is a continuous, integrated encapsulation structure that covers all transducer units and provides waterproofing, dustproofing, and stress dispersion.

9. The self-absorbing flexible ultrasonic patch and its preparation method according to claim 1, characterized in that, Includes the following steps: To prepare the matching layer slurry, polydimethylsiloxane was mixed with tungsten powder, and the filler was uniformly dispersed by ultrasonic dispersion and then degassed under vacuum. A piezoelectric layer array is prepared by cutting a PZT-5H piezoelectric ceramic preform to form a piezoelectric pillar array and drawing out electrode leads. To prepare the backing layer slurry, polydimethylsiloxane is mixed with tungsten powder, porous graphene and neodymium iron boron nanoparticles. The filler is uniformly dispersed by ultrasonic dispersion and vacuum degassing is performed. During the curing process, an external magnetic field perpendicular to the plane of the backing layer is applied to orient the neodymium iron boron nanoparticles along the thickness direction. The semi-solidified matching layer and the backing layer are then laminated and left to cure. The outermost layer of encapsulation material is cast to form an integrated encapsulation structure.

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