Patch type ultrasonic transducer for deep tissue imaging and acoustic material preparation method

Abstract

The invention relates to the field of high-end ultrasonic transducer manufacturing, and particularly discloses a patch type ultrasonic transducer for deep tissue imaging and an acoustic material preparation method, and a backing preparation method comprises the following steps: weighing an adhesive, a metal filler and a non-metal additive according to a mass ratio of 15: 55-75: 2; fully and uniformly mixing the weighed raw materials, and putting the mixed sample into a molding mold capable of demolding; the pressure is maintained for 10-30 min under the conditions that the pressure is larger than 10 MPa and the plasticizing temperature of the adhesive is reached, then the heating function is turned off, when the temperature is reduced to 120 DEG C, the pressure is rapidly reduced to 0 MPa at the moment, the adhesive is taken out when the adhesive is naturally cooled to the room temperature, and the backing is obtained. The problems of high sound attenuation, low sound impedance and low sound velocity preparation of the backing are solved, the dilemma problem of low sound impedance and ultrahigh sound attenuation is effectively solved, and the problem that the ultrathin design of the wearable patch type ultrasonic transducer conflicts with the maintenance of excellent acoustic performance due to insufficient sound attenuation of the existing backing is effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of high-end ultrasonic transducer manufacturing, and particularly relates to a patch-type ultrasonic transducer for deep tissue imaging and an acoustic material preparation method. Background Art

[0002] In recent years, patch-type ultrasonic transducers for ultrasonic imaging have received increasing attention due to their potential for continuous imaging monitoring of deep tissues, such as cardiac ultrasonic imaging monitoring, bladder volume imaging monitoring, and transcranial volume imaging monitoring. In these continuous imaging monitoring applications, the patch-type ultrasonic transducer must provide high-quality imaging while remaining thin, light, and comfortable to wear. However, for patch-type ultrasonic transducers, it is still a major challenge to achieve an ultra-thin structure while maintaining sufficient tissue penetration depth, sensitivity, bandwidth, and axial resolution.

[0003] The basic structure of a patch-type ultrasonic transducer for deep tissue ultrasonic imaging mainly consists of a piezoelectric layer, a matching layer, and a backing layer. In terms of acoustic performance, a matching layer with a high sound velocity and a piezoelectric material with a high electromechanical coupling coefficient are more conducive to improving the performance of the transducer such as bandwidth and sensitivity. The thickness changes of both are relatively small in the ultra-thin patch design, usually in the order of dozens of micrometers. The thickness of the backing layer is mainly determined by sound attenuation. However, the sound attenuation of these backing materials is still relatively limited, especially in the ultra-thin design of low-frequency wearable patch-type ultrasonic transducers. Due to the limitation of sound attenuation, traditional backing materials with high sound attenuation also need to be several millimeters thick to meet the requirements of high-quality imaging. This significantly increases the overall thickness, thereby reducing the wearability of the patch-type ultrasonic transducer. Therefore, an ultra-thin backing layer with high attenuation and a matching layer material with a high sound velocity are crucial for achieving an ultra-thin and high-performance wearable patch-type ultrasonic transducer.

[0004] Currently, the manufacturing methods of traditional high acoustic attenuation backing materials mainly mix liquid epoxy resin with metal powders or polymer materials. For example, particles such as tungsten powder, silver powder, alumina powder, glass powder, rubber, and polyurethane will cause scattering. To manufacture high attenuation backing materials, the particle radius is usually close to the order of magnitude of the wavelength: a) It is difficult to uniformly mix large-sized metal or polymer materials, making it difficult to prepare high attenuation backing materials; b) When the particle volume fraction exceeds a certain level, the acoustic attenuation decreases with the increase in the volume fraction of particle fillers; c) The acoustic impedance of the backing material increases with the increase in the volume fraction of tungsten powder fillers (>10 MRayl), and most of the acoustic energy enters the backing layer and is attenuated, resulting in a decrease in transducer sensitivity. d) When the acoustic impedance is too low (<3.5 MRayl), sound waves cannot effectively enter the backing layer, which will cause undamped vibration and thus prolong the pulse duration, reducing the axial resolution. e) To balance the acoustic impedance and acoustic attenuation, the acoustic attenuation of existing traditional high acoustic attenuation materials at 5 MHz is only 120 dB / cm. Therefore, in the design of ultra-thin transducers, the thickness usually needs to be increased, which conflicts with the design requirement of ultra-thin wearables for patch-type ultrasonic transducers. Developing an ultra-thin flexible backing layer with high acoustic attenuation and low impedance remains a key challenge in the design of wearable patch-type ultrasonic transducers.

[0005] The manufacturing methods of traditional matching layer materials with high sound velocity and high acoustic impedance are similar to those of the backing. They are mainly prepared by mixing liquid epoxy resin with metal powders or polymer materials. a) The sound velocity is usually low (<3000 m / s). To reduce acoustic attenuation, the particle size of the metal powder used is usually 1 - 5 μm, resulting in a limited volume fraction of metal powder filling. b) Adding too much metal powder material, although the density of the prepared matching layer composite material is increased, the sound velocity also decreases. Therefore, the acoustic impedance = sound velocity × density, and it is also difficult to increase (<10 MRayl), making it difficult to obtain an acoustic matching layer material with high sound velocity, high impedance, and low acoustic attenuation. Summary of the Invention

[0006] The purpose of the present invention is to prepare an ultra-thin flexible backing material with high acoustic attenuation, low sound velocity, and low acoustic impedance, a matching layer material with low acoustic attenuation, high sound velocity, and high acoustic impedance, as well as a manufacturing method and process for an ultra-thin wearable patch-type ultrasonic transducer, and to prepare a high-performance ultra-thin wearable patch-type ultrasonic transducer suitable for ultrasonic imaging, reducing the size of existing wearable or traditional invasive micro ultrasonic transducers.

[0007] The present invention adopts the following technical solutions:

[0008] A preparation method for a flexible backing material, comprising the following steps:

[0009] Weigh the adhesive, metal filler and non-metallic additive according to the mass ratio for use, wherein the mass ratio of the adhesive, metal filler and non-metallic additive is 15:55-75:2;

[0010] The weighed raw materials are thoroughly mixed in a centrifugal mixer, and the mixed sample is placed in a demoulding mold;

[0011] Maintain the pressure for 10-30 minutes at a pressure greater than 10 MPa and at the plasticizing temperature of the adhesive (>150°C). Then, turn off the heating function. When the temperature drops to 120°C, quickly reduce the pressure to 0 MPa to allow external air to enter the mixture and cause expansion, which is conducive to the formation of a non-dense microporous structure. Wait until it cools naturally to room temperature and then take it out to obtain the backing.

[0012] Preferably, the adhesive is selected from rubber-type chlorinated polyethylene (CPE) and polypropylene, high and low pressure polyethylene and acrylonitrile-butadiene-styrene plastics.

[0013] Preferably, the metal filler is selected from one or more of tungsten powder, ferroferric oxide, iron-manganese-zinc ferrite, copper oxide powder and iron powder.

[0014] Preferably, the non-metallic additive is selected from two of talc, zinc stearate and nitrile rubber powder.

[0015] Another object of the present invention is to provide a method for preparing a matching layer material, comprising the following steps:

[0016] Two-component epoxy resin material with good liquid fluidity is used as adhesive, high-density metal material (>8g / cm 3 ) is used to increase the density of the matching layer. High-acoustic-velocity non-metallic materials (>10,000 m / s) are used to increase the acoustic velocity of the matching layer, and the acoustic impedance of the matching layer is thereby increased through appropriate proportions. The raw materials for the matching layer are obtained as follows: a two-component epoxy resin selected from one of EPO-TEK 301 and E51; a high-density metal filler selected from one or more of tungsten powder, nickel powder, and copper powder; and a high-acoustic-velocity non-metallic material selected from boron nitride powder, boron carbide powder, diamond powder, and silicon carbide powder. The raw materials are weighed according to the mass ratio and set aside. The two-component epoxy resin is composed of epoxy resin (Component A) and curing agent (Component B).

[0017] To ensure that the two powders are evenly mixed, the high-density metal filler and the high-sonic-velocity non-metallic material are first mixed evenly using a centrifugal mixer;

[0018] To prevent the epoxy resin from prematurely cross-linking and curing during the centrifugal stirring process, first pour the epoxy resin of component A and mix it evenly again using a centrifugal mixer, then add the curing agent of component B and mix it evenly using a centrifugal mixer;

[0019] It is necessary to strictly control the mass ratio of liquid epoxy. Excessive epoxy will cause the powder to overflow from the mold during the pressing and curing process. The prepared mixture is exactly in a semi-wet and semi-powdery state to ensure that there is no overflow during the pressing and curing process.

[0020] Place it into a molding die, carry out pressing and curing. The heating temperature is determined according to the curing temperature of the epoxy resin (60 °C and above), the holding pressure is greater than 10 MPa. According to the material properties of the epoxy resin, adjust the curing time, and the curing time is 2 hours and above. After cooling to room temperature, take it out to complete the preparation and obtain the matching layer.

[0021] Preferably, the two-component epoxy resin is two-component EPO-TEK 301-1, and the mass ratio between the epoxy resin of component A and the curing agent of component B is 4:1.

[0022] Preferably, the mass ratio of the raw materials of the matching layer material is: two-component epoxy resin: metal material: non-metal material = 1:4:3.

[0023] Another object of the present invention is to provide a patch-type ultrasonic transducer for deep tissue imaging, which includes a matching layer, a piezoelectric material, a backing, and a flexible circuit board. Among them, the backing is prepared according to the preparation method of a flexible backing material described in Claim 1. The matching layer includes three layers. When the ultrasonic transducer is prepared, the first matching layer is prepared according to the preparation method of a matching layer material described in Claim 7. The second matching layer is prepared from raw materials with a mass ratio of epoxy resin Epo-Tek 301-1: copper powder: graphite = 5:2:3, mixed evenly by a vacuum centrifugal mixer, poured into a self-made mold, and placed in an oven for curing to complete the preparation. The third matching layer is prepared by mixing pure epoxy resin Epo-Tek 301-1 evenly by a vacuum centrifugal mixer, then pouring it into a self-made mold and placing it in an oven for curing. Before bonding, all the matching layers are polished to the designed thickness by a high-precision grinding machine, and the surfaces of the matching layer and the piezoelectric material to be bonded are cleaned with a lint-free cloth using 95% alcohol. The piezoelectric material is immersed in a fluorocarbon surfactant for 15 minutes for surface treatment to increase wettability. After cleaning, it needs to be placed in a Plasma vacuum plasma treatment instrument to treat the surfaces of the matching layer and the piezoelectric material again. The bonding of each layer uses a two-component epoxy resin Epo-Tek 301-2 glue, and the mass ratio between component A and component B is 1:0.35. A protective film is used to cover and fix one side of the surface of the treated third matching layer, and the prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on the other side. After the second matching layer is aligned with the third matching layer, it is placed above the third matching layer. The prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on one side of the second matching layer. The first matching layer is placed in the same way as the second matching layer. The positive electrode of the piezoelectric layer is covered with a protective film to prevent the glue from overflowing onto the positive electrode surface, and then it is bonded to the first matching layer in the same way. Finally, the bonded acoustic stack, including the first, second, and third matching layers and the piezoelectric material, is placed in a precision pressing mold for bonding with a pressure of 30 kg and placed in an oven for curing. The bonded acoustic stack material and the prepared backing are placed in a precision pressing mold for bonding with a pressure of 15 kg and placed in an oven for curing. Subsequently, the power signal line and the ground line are led out and connected to the flexible circuit board FPCB to complete the production.

[0024] Preferably, the piezoelectric material is selected from one of PZT-5H and single crystal materials. Among them, PZT-5H is a kind of lead zirconate titanate (Pb(Zr,Ti)O3) piezoelectric ceramic.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) The acoustic impedance range of the prepared backing material is 2 - 6 MRayl, the sound velocity is < 1500 m / s, and the measured acoustic attenuation range at a frequency of 3 MHz is 150 dB / cm to 420 dB / cm, which is much higher than existing research and preparation methods. In the design of a low-frequency (3 MHz) wearable patch-type ultrasonic transducer, the thickness of the backing is only 0.7 mm, approximately two wavelengths. While ensuring the integrity of the acoustic structure, this breakthrough new backing material and manufacturing method greatly reduce the overall thickness of the ultrasonic transducer. The low acoustic impedance design causes some sound waves to be reflected back to the piezoelectric layer, which is beneficial to improving the sensitivity of the transducer. It solves the problems of preparing a backing with high acoustic attenuation, low acoustic impedance, and low sound velocity, effectively resolves the dilemma of low acoustic impedance and ultra-high acoustic attenuation, and also resolves the conflict between the ultra-thin design of the patch-type ultrasonic transducer due to insufficient acoustic attenuation of the existing backing and maintaining excellent acoustic performance.

[0027] 2) The acoustic impedance range of the prepared matching layer material is 10 - 13 MRayl, the sound velocity is > 3500 m / s, and the measured acoustic attenuation range at a frequency of 3 MHz is 2 dB / cm to 10 dB / cm. The acoustic impedance and sound velocity are much higher than existing matching layer preparation methods. The matching layer material with high acoustic impedance can be used in three-layer and multi-layer acoustic matching designs to reduce sound energy loss and further improve the acoustic performance such as the bandwidth and sensitivity of the ultra-thin wearable patch-type ultrasonic transducer.

[0028] 3) The prepared flexible backing and matching layer materials are not limited to the design of wearable patch-type ultrasonic transducers, but can also be used in the design of invasive and other micro ultrasonic probes, showing excellent market application prospects. It has been verified in the design of a 3 MHz low-frequency wearable patch-type ultrasonic transducer. The total thickness of the prepared low-frequency wearable patch-type ultrasonic transducer is 2.2 mm, and the backing thickness is only about two wavelengths, 0.7 mm, accounting for 32% of the overall thickness. It effectively solves the problem of the difficulty in miniaturizing existing wearable ultrasonic transducers and traditional ultrasonic transducers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flowchart of the preparation method of the flexible backing material according to an embodiment of the present invention.

[0030] Figure 2 It is a flowchart of the preparation method of the matching layer material according to an embodiment of the present invention.

[0031] Figure 3 It is a flowchart of the ultrasonic patch production in an embodiment of the present invention.

[0032] Figure 4 It is a schematic structural diagram of the patch-type ultrasonic transducer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following describes the technical solutions in the embodiments of the present invention clearly and completely in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0034] Example 1.

[0035] Please refer to Figure 1 , this embodiment provides a preparation method of a flexible backing material, including the following steps:

[0036] Weigh the binder, metal filler and non-metal additive for standby according to the mass ratio. In this embodiment, the binder is CPE with a particle size of 150 μm, the metal filler is tungsten powder with a particle size of 3 - 5 μm, the non-metal additives are talc powder (30 μm) and zinc stearate (20 μm), and the mass ratio between the raw materials is CPE: tungsten powder: talc powder: zinc stearate = 15:75:1:1;

[0037] Use a centrifugal mixer to fully mix the weighed raw materials evenly. Set the rotation speed to 1500 revolutions per minute, stir forward and reverse for 2 minutes each, and place the mixed sample into a demoldable forming mold;

[0038] Through a vulcanization instrument or other equipment that can heat and pressurize, keep the pressure for 10 minutes under high pressure (20 MPa) and high temperature (170 °C). Then, turn off the heating function. When the temperature drops to 120 °C, at this time, quickly reduce the pressure from 20 MPa to 0 MPa, so that external air can enter the mixture and expand, which is conducive to the formation of a non-dense microporous structure. Wait until it cools naturally to room temperature and take it out to obtain the backing.

[0039] Example 2.

[0040] The difference between this Example 2 and Example 1 is that CPE (150 μm): tungsten powder (3 - 5 μm): talc powder (30 μm): zinc stearate (20 μm) = 15:60:1:1.

[0041] Example 3.

[0042] The difference between this Example 3 and Example 1 is that the metal filler is iron powder with a particle size of 50 μm, and CPE (150 μm): iron powder (50 μm): talc powder (30 μm): zinc stearate (20 μm) = 15:60:1:1.

[0043] Example 4.

[0044] This Example 4 is different from Example 1 in that the metal filler is a mixture of tungsten powder and iron powder, and the ratio of CPE (150μm): tungsten powder (3 - 5μm): iron powder (50μm): talc powder (30μm): zinc stearate (20μm) = 15:45:10:1:1.

[0045] The test performance results of the flexible backing materials prepared in the above Examples 1 - 4 are shown in Table 1:

[0046] Table 1

[0047]

[0048] Example 5.

[0049] Please refer to Figure 2 , the present invention provides a preparation method of a matching layer material, including the following steps:

[0050] Weigh a two - component epoxy resin, a high - density metal filler and a spare high - sound - velocity non - metal material according to the mass ratio. Among them, the two - component epoxy resin consists of component A epoxy resin and component B curing agent; in this example, the two - component epoxy resin is EPO - TEK 301 (hereinafter referred to as epoxy 301), the high - density metal filler is copper powder with a particle size of 1μm, and the high - sound - velocity non - metal material is boron carbide powder with a particle size of 1μm; the mass ratio between the raw materials is epoxy 301: copper powder: boron carbide = 1:4:3;

[0051] To ensure the uniform mixing of the two powders, first use a centrifugal mixer to mix the high - density metal filler and the high - sound - velocity non - metal material evenly, set the rotation speed to 1500 revolutions per minute, and stir in both forward and reverse directions for 2 minutes each;

[0052] To prevent the premature cross - linking and curing of the epoxy resin during the centrifugal mixing process, first pour in component A of the epoxy resin and use the centrifugal mixer to mix it evenly again, then add component B of the curing agent and use the centrifugal mixer to mix it evenly. Among them, the rotation speed of the centrifugal mixer is set to 1500 revolutions per minute, and stir in both forward and reverse directions for 2 minutes each;

[0053] It is necessary to strictly control the mass ratio of the liquid epoxy. Excessive epoxy will cause the powder to overflow from the mold during the pressing and curing process. The prepared mixture is exactly in a semi - wet and semi - powder state to ensure that it will not overflow during the pressing and curing process.

[0054] Place it into a molding mold, and use a vulcanizer that can apply pressure and heat for pressing and curing, or add a vacuum device on this basis to achieve vacuum heating and pressurization. The required pressure is 20MPa, the temperature is 60°, keep the pressure at 20MPa, cure for 2 hours, take it out after cooling to room temperature, and complete the preparation to obtain the matching layer.

[0055] Example 6.

[0056] The difference between this Example 6 and Example 5 is that the high-density metal filler is nickel powder with a particle size of 1 μm, and the mass ratio between the raw materials is Epoxy 301: nickel powder (1 μm): boron carbide (1 μm) = 1:4:3.

[0057] Example 7.

[0058] The difference between this Example 7 and Example 5 is that the high-density metal filler is nickel powder with a particle size of 1 μm, and the high-sound-speed non-metallic material is diamond with a particle size of 1 μm, and the mass ratio between the raw materials is Epoxy 301: nickel powder (1 μm): diamond (1 μm) = 1:4:3.

[0059] Example 8.

[0060] The difference between this Example 7 and Example 5 is that the high-density metal filler is nickel powder with a particle size of 1 μm, and the high-sound-speed non-metallic material is boron nitride with a particle size of 1 μm, and the mass ratio between the raw materials is Epoxy 301: nickel powder (1 μm): boron nitride (1 μm) = 1:4:3.

[0061] For the matching layer materials prepared in the above Examples 5 - 8, the performance test results are shown in Table 2:

[0062] Table 2

[0063]

[0064]

[0065] Example 9.

[0066] Please refer to Figures 3 to 4, another object of the present invention is to provide a patch-type ultrasonic transducer for deep tissue imaging, including a matching layer, a piezoelectric material, a backing, and a flexible circuit board. Among them, the backing is prepared by the preparation method of the above-mentioned flexible backing material. The matching layer includes three layers. When the ultrasonic transducer is prepared, the first-layer matching layer is prepared by the preparation method of the above-mentioned matching layer material. The second-layer matching layer is prepared from raw materials with a mass ratio of epoxy resin Epo-Tek 301-1: copper powder: graphite = 5:2:3, mixed evenly by a vacuum centrifugal mixer, with the rotation speed set at 1500 revolutions per minute, and stirred forward and backward for 2 minutes each, poured into a self-made mold, and placed in an oven at 60 °C for 2 h to complete the preparation. The third-layer matching layer is prepared by mixing pure epoxy resin Epo-Tek 301-1 evenly by a vacuum centrifugal mixer, with the rotation speed set at 1500 revolutions per minute, and stirred forward and backward for 2 minutes each, poured into a self-made mold, and placed in an oven at 60 °C for 2 h. Before bonding, all the matching layers are polished to the designed thickness by a high-precision grinding machine, and the surfaces of the matching layers and the piezoelectric material to be bonded are cleaned with a dust-free cloth using 95% alcohol. The piezoelectric material is immersed in a fluorocarbon surfactant for 15 minutes for surface treatment to increase wettability. After cleaning, it needs to be placed in a Plasma vacuum plasma treatment instrument with a radio frequency power of 30 W and a model of PDC-002, with an oxygen flow rate of 20 mL / min, and the surfaces of the matching layers and the piezoelectric material are treated again for 1 minute. The bonding of each layer uses a two-component epoxy resin Epo-Tek 301-2 glue, and the mass ratio between component A and component B is 1:0.35. The surface of the treated third-layer matching layer is covered and fixed with a protective film on one side, and the prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on the other side. After the second-layer matching layer is aligned with the third-layer matching layer, it is placed above the third-layer matching layer. The prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on one side of the second-layer matching layer. The first-layer matching layer is placed in the same way as the second-layer matching layer. The positive electrode of the piezoelectric layer is covered with a protective film to prevent the glue from overflowing onto the positive electrode surface, and then it is bonded to the first-layer matching layer in the same way. Finally, the bonded acoustic stack, including the first, second, and third-layer matching layers and the piezoelectric material, is placed in a precision pressing mold for bonding, with a pressure of 30 kg, and placed in an oven at 60 °C for 8 hours. The bonded acoustic stack material and the prepared backing are placed in a precision pressing mold for bonding, with a pressure of 15 kg, and placed in an oven at 45 °C for 12 hours. Subsequently, the power signal line and the ground wire are led out and connected to the flexible circuit board FPCB to complete the production. The design rules for the thickness of each layer are as follows: The matching layer is designed according to a quarter wavelength, the piezoelectric material is determined according to the designed operating frequency and the frequency constant in the thickness direction, and the backing is appropriately adjusted according to the sound attenuation and the operating frequency of the transducer.For example, the operating frequency of the transducer is 3 MHz, the thickness of the piezoelectric material used is 0.61 mm, the acoustic impedance of the first matching layer is 13.5 MRayl, the sound velocity is 3500 m / s, and the thickness is 0.290 mm. The acoustic impedance of the second layer is 4 MRayl, the sound velocity is 2900 m / s, and the thickness is 0.240 mm. The acoustic impedance of the third matching layer is 2.6 MRayl, the sound velocity is 2600 m / s, and the thickness is 0.215 mm. The acoustic impedance of the backing is 5.6 MRayl, the sound velocity is 1000 m / s, and the acoustic attenuation at 3 MHz is 350 dB / cm, and the thickness is 0.7 mm.

[0067] The piezoelectric material is selected from one of PZT-5H and single crystal materials. Among them, PZT-5H is a kind of lead zirconate titanate (Pb(Zr,Ti)O3) piezoelectric ceramic. In this embodiment, the piezoelectric material is piezoelectric ceramic.

[0068] In summary: Under the condition of ensuring the integrity of the acoustic structure, the breakthrough new backing material and manufacturing method of the present invention greatly reduce the overall thickness of the ultrasonic transducer. The design of low acoustic impedance causes some sound waves to be reflected back to the piezoelectric layer, which is beneficial to improving the sensitivity of the transducer. It solves the problems of high acoustic attenuation, low acoustic impedance, and low sound velocity preparation of the backing, effectively solves the dilemma of low acoustic impedance and ultra-high acoustic attenuation, and the problem that the insufficient acoustic attenuation of the existing backing conflicts with the ultra-thin design of the wearable patch-type ultrasonic transducer and maintaining excellent acoustic performance.

[0069] The matching layer material of the present invention can be used for three-layer and multi-layer acoustic matching designs to reduce sound energy loss and further improve the acoustic performance such as the bandwidth and sensitivity of the ultra-thin wearable patch-type ultrasonic transducer.

[0070] The above process flow realizes the design and manufacture of the low-frequency ultra-thin wearable patch-type ultrasonic transducer. The prepared flexible backing and matching layer materials are not limited to the design of the wearable patch-type ultrasonic transducer, but can also be used in the design of interventional and other micro ultrasonic probes, and have excellent market application prospects. It has been verified in the design of the 3 MHz low-frequency wearable patch-type ultrasonic transducer. The total thickness of the prepared low-frequency wearable patch-type ultrasonic transducer is 2.2 mm, and the thickness of the backing is only about two wavelengths, 0.7 mm, accounting for 32% of the overall thickness. It effectively solves the problem of difficult miniaturization of existing wearable ultrasonic transducers and traditional ultrasonic transducers.

[0071] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

[0072] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of a flexible backing material, characterized in that, It includes the following steps: Weigh the adhesive, metal filler and non-metal additive according to the mass ratio for standby. The mass ratio among the adhesive, metal filler and non-metal additive is 15:55 - 75:

2. Fully mix the weighed raw materials evenly in a centrifugal mixer, and place the mixed sample into a demoldable molding die. Keep the pressure for 10 - 30 minutes under the conditions of greater than 10 MPa and reaching the plasticizing temperature of the adhesive. Then, turn off the heating function. When the temperature drops to 120 °C, at this time, quickly reduce the pressure to 0 MPa to allow the outside air to enter the mixture and expand, which is conducive to forming a non-dense microporous structure. Wait until it cools naturally to room temperature and then take it out to obtain the backing.

2. The preparation method of a flexible backing material according to claim 1, characterized in that, The adhesive is selected from rubber-type chlorinated polyethylene and polypropylene, high- and low-pressure polyethylene, and acrylonitrile-butadiene-styrene plastic.

3. The preparation method of a flexible backing material according to claim 1, characterized in that, The metal filler is selected from one or more of tungsten powder, iron trioxide, iron-manganese-zinc ferrite, copper oxide powder, and iron powder.

4. The preparation method of a flexible backing material according to claim 1, characterized in that, The non-metal additive is selected from two of talc powder, zinc stearate, and nitrile rubber powder.

5. A method for preparing a matching layer material, characterized in that, It includes the following steps: Obtain the raw materials for the matching layer material: two-component epoxy resin, high-density metal filler, and high-sound-speed non-metal material; weigh the raw materials for standby. Among them, the two-component epoxy resin consists of component A epoxy resin and component B curing agent. First, use a centrifugal mixer to mix the high-density metal filler and high-sound-speed non-metal material evenly. To prevent the epoxy resin from cross-linking and curing prematurely during the centrifugal mixing process, first pour in component A epoxy resin and use the centrifugal mixer to mix evenly again, and then add component B curing agent and use the centrifugal mixer to mix evenly. Place it into a molding die, carry out pressing and curing. The heating temperature is 60 °C or above, the holding pressure is greater than 10 MPa, and the curing time is 2 hours or above. Take it out after cooling to room temperature to complete the preparation and obtain the matching layer.

6. The preparation method of a matching layer material according to claim 5, wherein, The two-component epoxy resin is selected from one of EPO-TEK 301 and E51; the high-density metal filler is selected from one or more of tungsten powder, nickel powder, and copper powder; the high-sound-speed non-metal material is selected from boron nitride powder, boron carbide powder, diamond powder, and silicon carbide powder.

7. The preparation method of a matching layer material according to claim 5, characterized in that, The two-component epoxy resin is two-component EPO-TEK 301-1, and the mass ratio between component A epoxy resin and component B curing agent is 4:

1.

8. The preparation method of a matching layer material according to claim 5, wherein The mass ratio of the raw materials for the matching layer material is: two-component epoxy resin: metal material: non-metal material = 1:4:

3.

9. A patch-type ultrasonic transducer for deep tissue imaging, characterized in that, It includes a matching layer, a piezoelectric material, a backing, and a flexible circuit board. Among them, the backing is prepared according to the preparation method of a flexible backing material described in Claim 1. The matching layer includes three layers. When preparing the ultrasonic transducer, the first-layer matching layer is prepared according to the preparation method of a matching layer material described in Claim 7. The second-layer matching layer is prepared from raw materials with a mass ratio of epoxy resin Epo-Tek 301-1: copper powder: graphite = 5:2:

3. It is mixed evenly by a vacuum centrifugal mixer, poured into a self-made mold, and placed in an oven for curing to complete the preparation. The third-layer matching layer is prepared by mixing pure epoxy resin Epo-Tek 301-1 evenly by a vacuum centrifugal mixer, then poured into a self-made mold and placed in an oven for curing. Before bonding, all the matching layers are polished to the designed thickness by a high-precision grinding machine, and the surfaces of the matching layer and the piezoelectric material to be bonded are cleaned with a lint-free cloth using 95% alcohol. The piezoelectric material is soaked in a fluorocarbon surfactant for 15 minutes for surface treatment to increase wettability. After cleaning, it needs to be placed in a Plasma vacuum plasma treatment instrument to treat the surfaces of the matching layer and the piezoelectric material again. The bonding of each layer uses a two-component epoxy resin Epo-Tek 301-2 glue, and the mass ratio between component A and component B is 1:0.

35. A protective film is used to cover and fix one side of the surface of the treated third-layer matching layer, and the prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on the other side. After the second-layer matching layer is aligned with the third-layer matching layer, it is placed above the third-layer matching layer. The prepared epoxy resin Epo-Tek 301-2 glue is evenly brushed on one side of the second-layer matching layer. The first-layer matching layer is placed in the same way as the second-layer matching layer. The positive electrode of the piezoelectric layer is covered with a protective film to prevent the glue from overflowing onto the positive electrode surface, and then it is bonded to the first-layer matching layer in the same way. Finally, the bonded acoustic laminate, including the first, second, and third-layer matching layers and the piezoelectric material, is placed in a precision pressing mold for bonding with a pressure of 30 kg and placed in an oven for curing. The bonded acoustic laminate material and the prepared backing are placed in a precision pressing mold for bonding with a pressure of 15 kg and placed in an oven for curing. Subsequently, the power signal line and the ground line are led out and connected to the flexible circuit board FPCB to complete the production.

10. A patch-type ultrasonic transducer for deep tissue imaging according to claim 9, characterized in that, The piezoelectric material is selected from one of PZT-5H and single crystal materials.

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