High-intensity and high-frequency air-coupled ultrasonic transducer and method for manufacturing same

Abstract

An air-coupled ultrasonic transducer is disclosed. The air-coupled ultrasonic transducer may comprise: an acoustic metastructure including a plate having through-holes formed therein, a plurality of wires disposed in linear-shaped grooves formed in the through-holes, and two supports attached to the plurality of wires; a matching layer bonded to one surface of the acoustic metastructure and made of a porous material in the form of a membrane having micro-scale fine holes formed therein; a piezoelectric layer bonded to one surface of the matching layer and made of a piezoelectric composite including a piezoelectric element and epoxy; and a rear layer bonded to one surface of the piezoelectric layer and made of a material having an acoustic impedance value smaller than that of the piezoelectric layer.

Description

High-intensity high-frequency air-coupled ultrasonic transducer and method for manufacturing the same

[0001] The present invention relates to an air-coupled ultrasonic transducer that generates high-intensity and high-frequency air-coupled ultrasonic waves and a method for manufacturing the same. More specifically, the invention relates to a structure of an air-coupled ultrasonic transducer capable of increasing the intensity and frequency of ultrasonic waves transmitted and received in the air, and a method for manufacturing the same.

[0002] Generally, ultrasound can be used in two main ways: contact and non-contact. Non-contact ultrasound transducers are referred to as air-coupled ultrasound transducers. Currently, most high-frequency (e.g., megahertz) ultrasound transducers used for medical diagnosis are employed in a manner where they come into direct contact with the target. This is because the attenuation of ultrasound signals by the intermediate medium increases with higher frequencies. Even in contact-type methods, mediating materials such as gel are used between the transducer and the target to improve transmission and reception performance and avoid the influence of air, which has a very high attenuation coefficient. However, there are many human diseases that require non-contact ultrasound diagnosis and treatment due to structural issues or concerns about infection. For instance, there is a continuing demand for non-contact air-coupled ultrasound transducers that utilize air as the medium, particularly in the diagnosis of hearing and skin diseases, as well as in emergency fields such as skin burns.

[0003] The background description of the invention is provided to facilitate a better understanding of the present invention. The matters described in the background description should not be construed as an acknowledgment that they exist as prior art.

[0004] Generally, for ultrasound to be used for medical diagnosis, the signal intensity and frequency must be above a certain level. However, due to the significant attenuation of ultrasound signals in air, not only is the transmitted and received energy greatly reduced, but this attenuation becomes even more severe as the frequency increases. Consequently, non-contact air-coupled ultrasound transducers suitable for medical use have not yet been developed domestically or internationally.

[0005] Since existing ultrasonic transducer manufacturing technology has not been able to overcome the aforementioned problems, the inventor of the present invention has come to invent a new high-intensity, high-frequency air-coupled ultrasonic transducer capable of non-contact ultrasonic diagnosis and treatment, and a method for manufacturing the same.

[0006] Accordingly, the problem to be solved by the present invention is to provide a high-intensity, high-frequency air-coupled ultrasonic transducer applicable to single and multi-frequency, single-element, and array-type ultrasonic transducers.

[0007] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0008] To solve the problem described above, an air-coupled ultrasonic transducer according to an embodiment of the present invention is provided. The air-coupled ultrasonic transducer may include an acoustic metastructure configured to include a plate having a through hole, a plurality of wires disposed in straight grooves formed in the through hole, and two supports attached to the plurality of wires; a matching layer formed of a porous material in the form of a membrane having micro-sized holes formed therein, bonded to one surface of the acoustic metastructure; a piezoelectric layer formed of a piezoelectric composite comprising a piezoelectric element and epoxy, bonded to one surface of the matching layer; and a back layer formed of a material having an acoustic impedance value smaller than that of the piezoelectric layer, bonded to one surface of the piezoelectric layer.

[0009] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the through hole may have the same shape and size as the ultrasonic transducer aperture.

[0010] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the plurality of wires are plated with metal or composed of metal, and the diameter of the plurality of wires, the spacing between the plurality of wires, or the air gap between the plurality of wires and the surface of the ultrasonic transducer aperture may be determined according to the frequency.

[0011] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the acoustic metastructure may be planar, spherical, or cylindrical depending on the shape of the air-coupled ultrasonic transducer.

[0012] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the acoustic metastructure may be configured to further include a height adjustment member attached to one surface of the plate.

[0013] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the thickness of the plate, the thickness of the two supports, or the thickness of the height adjustment member may have a value that is a multiple of λ / 2, and λ may be the wavelength when ultrasonic waves propagate in air.

[0014] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the plurality of wires and the air gap are determined as multiples of λ / 2 by adjusting a housing including a screw thread, and λ may be the wavelength when ultrasonic waves propagate in air.

[0015] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the acoustic metastructure may be detachable and mountable.

[0016] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the matching layer is composed of a porous material in the form of a membrane in which micro-sized micro-holes are formed, the thickness of the matching layer is L / 4, and L may be the wavelength when the ultrasonic waves propagate through the matching layer.

[0017] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the piezoelectric composite is formed by mixing the piezoelectric element and the epoxy and arranging them alternately, the thickness of the piezoelectric composite is an odd multiple of P / 2, and P may be the wavelength when the ultrasonic wave propagates through the piezoelectric composite.

[0018] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the piezoelectric layer is a multi-piezoelectric layer having a plurality of piezoelectric layers, and the piezoelectric composite is a stacked structure in which the piezoelectric element and the epoxy are mixed and arranged alternately, and the poling direction of the multi-piezoelectric layer is opposite for each alternating layer, and the signal line of the multi-piezoelectric layer and ground can be applied alternately to the cross-section of each alternating layer.

[0019] In an air-coupled ultrasonic transducer according to one embodiment of the present invention, the piezoelectric elements included in each of the two or more piezoelectric layers may be of the same type or different types, and may be in the form of an annular, ring, or array.

[0020] To solve the problem described above, an air-coupled ultrasonic transducer for multiple frequencies according to another embodiment of the present invention is provided. The above-described multi-frequency air-coupled ultrasonic transducer comprises: a first acoustic metastructure for a first frequency configured to include a first plate having a first through hole, a plurality of first wires disposed in straight grooves formed in the first through hole, and two first supports attached to the plurality of first wires; a second acoustic metastructure for a second frequency configured to include a second plate having a first through hole, a plurality of second wires disposed in straight grooves formed in the second through hole, and two second supports attached to the plurality of second wires; a first transducer for the first frequency bonded to one surface of the first acoustic metastructure and comprising a first matching layer, a first piezoelectric layer, and a first back layer; and a second transducer for the second frequency bonded to one surface of the second acoustic metastructure and comprising a second matching layer, a second piezoelectric layer, and a second back layer, wherein the diameters of the first wires and the diameters of the second wires are different, and the first The spacing between the wires and the spacing between the second wires are different, and the air gap between the plurality of first wires of the first acoustic metastructure and the surface of the first ultrasonic transducer aperture and the air gap between the plurality of second wires of the second acoustic metastructure and the surface of the second ultrasonic transducer aperture may be different.

[0021] To solve the problem described above, a method for manufacturing an air-coupled ultrasonic transducer according to another embodiment of the present invention is provided. The method for manufacturing the air-coupled ultrasonic transducer may include the steps of: creating a through hole in a plate that is identical in shape and size to the diameter of the ultrasonic transducer, wherein the plate is included in an acoustic metastructure; creating a predetermined number of straight grooves in the through hole; coupling a plurality of wires to the straight grooves; and fixing the plurality of wires using a plurality of supports. At this time, the plurality of supports are configured such that the thickness of the plurality of supports can be varied in multiples of λ / 2, and λ may be the wavelength when the ultrasonic wave propagates in air.

[0022] Specific details of other embodiments are included in the detailed description and drawings.

[0023] According to the present invention, by adjusting the physical properties, size, arrangement spacing, air gap, etc., of the wires and plates of the acoustic metastructure, and by efficiently designing and combining a matching layer based on a lightweight porous material in the form of a membrane suitable for air-coupled ultrasound, a piezoelectric layer composed of a piezoelectric composite, and a lightweight back layer, the intensity of non-contact air-coupled ultrasound energy can be significantly improved and the frequency can be increased up to the megahertz band. The manufacturing process of the acoustic metastructure of the air-coupled ultrasound transducer of the present invention is suitable for mass production.

[0024] In addition, the air-coupled ultrasonic transducer of the present invention can be applied to single and multi-frequency, single-element, and array-type ultrasonic transducers.

[0025] In addition, the air-coupled ultrasonic transducer of the present invention can be applied to various medical fields requiring diagnosis and treatment via a non-contact ultrasonic method, such as the diagnosis of hearing and skin diseases and skin burns. Furthermore, it can also be applied to various fields other than the medical field, such as the industrial sector, where the presence or absence of a target and structural problems must be detected via a non-contact method.

[0026] The effects according to the present invention are not limited to those exemplified above, and various other effects are included in this specification.

[0027] FIG. 1 is a diagram showing the configuration of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0028] FIG. 2 is a diagram showing the configuration of a single-frequency or multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0029] FIG. 3 is a diagram showing the fabrication process of an air-coupled ultrasonic transducer acoustic metastructure according to one embodiment of the present invention.

[0030] FIG. 4 is a diagram illustrating a method for precisely adjusting the air gap between the wires of an acoustic metastructure and the aperture surface of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0031] FIG. 5 is a diagram showing an air-coupled ultrasonic transducer structure composed of a single piezoelectric layer and multiple piezoelectric layers according to one embodiment of the present invention.

[0032] Figure 6 is a graph showing the experimental performance evaluation results of an air-coupled ultrasonic transducer manufactured according to one embodiment of the present invention.

[0033] FIG. 7 is a flowchart illustrating a method for manufacturing an air-coupled ultrasonic transducer manufactured according to one embodiment of the present invention.

[0034] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. In connection with the description of the drawings, similar reference numerals may be used for similar components.

[0035] In this document, expressions such as "have," "can have," "include," or "can include" refer to the existence of the relevant feature (e.g., numerical values, functions, actions, or components, etc.) and do not exclude the existence of additional features.

[0036] In this document, expressions such as “A or B,” “at least one of A or / and B,” or “one or more of A or / and B” may include all possible combinations of items listed together. For example, “A or B,” “at least one of A and B,” or “at least one of A or B” may refer to cases including (1) at least one A, (2) at least one B, or (3) both at least one A and at least one B.

[0037] Expressions such as "first," "second," "first," or "second" used in this document may modify various components regardless of order and / or importance, and are used merely to distinguish one component from another without limiting such components. For example, the first user device and the second user device may represent different user devices regardless of order or importance. For example, without departing from the scope of rights set forth in this document, the first component may be named the second component, and similarly, the second component may be renamed the first component.

[0038] Where it is stated that a certain component (e.g., a first component) is "(operatively or communicatively) coupled with" or "connected to" another component (e.g., a second component), it should be understood that the said certain component may be directly connected to the said other component or connected through another component (e.g., a third component). On the other hand, where it is stated that a certain component (e.g., a first component) is "directly connected" or "directly connected" to another component (e.g., a second component), it may be understood that no other component (e.g., a third component) exists between the said certain component and the said other component.

[0039] As used in this document, the expression “configured to” may be replaced, depending on the context, with, for example, “suitable for,” “having the capacity to,” “designed to,” “adapted to,” “made to,” or “capable of.” The term “configured to” does not necessarily mean only that which is “specifically designed to” in hardware. Instead, in some situations, the expression “device configured to” may mean that the device is “capable of” in conjunction with other devices or components. For example, the phrase “processor configured to perform A, B, and C” may mean a dedicated processor for performing those operations (e.g., an embedded processor), or a generic-purpose processor (e.g., a CPU or application processor) capable of performing those operations by executing one or more software programs stored in a memory device.

[0040] The terms used in this document are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this document. Terms used in this document that are defined in general dictionaries may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this document. In some cases, even terms defined in this document may not be interpreted to exclude the embodiments of this document.

[0041] The features of each of the various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and as will be fully understood by those skilled in the art, various technical interlocking and operation are possible, and each embodiment may be implemented independently of one another or together in an interlocking relationship.

[0042] Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention with reference to the attached drawings.

[0043] FIG. 1 is a diagram showing the configuration of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0044] Referring to FIG. 1, an air-coupled ultrasonic transducer according to one embodiment of the present invention may include an acoustic metastructure (100) and / or a transducer. The transducer may include a matching layer (200), a piezoelectric layer (300), and / or a back layer (400).

[0045] The acoustic metastructure (100) may be an artificial structure having special acoustic properties that do not exist naturally. According to an embodiment, the acoustic metastructure (100) may generate high-intensity, high-frequency air-coupled ultrasound.

[0046] An acoustic metastructure (100) according to one embodiment of the present invention may include at least one plate (101), a support (102), and / or a wire (103) and a through hole (104) provided in at least one plate (101). The plate (100) may be provided with a through hole (104) in the center of the plate (101) that is identical or similar in shape and size to the ultrasonic transducer aperture so that the energy of the air-coupled ultrasonic waves can be directly transmitted and received into the air. Here, the 'ultrasonic transducer aperture' refers to the effective diameter of the ultrasonic beam or the size of the area where ultrasonic energy is effectively transmitted, and may be determined according to the design and characteristics of the ultrasonic transducer.

[0047] A wire (103) according to one embodiment of the present invention may be placed between through holes (104). The wire (103) may be plated with metal or composed of solid materials having a high reflection coefficient with air, such as metal. It can transmit and receive ultrasonic waves. At this time, the material constituting the wire (103), the diameter of the wire (103), the spacing between the wires (103), and / or the air gap between the wire (103) and the surface of the ultrasonic transducer aperture may be determined by the Fabry-Perot resonant cavity conditions and resonance principles. By adjusting the characteristic(s) of the wire (103) described above, the ultrasonic intensity and frequency can be increased. The structure of the acoustic metastructure (100) according to an embodiment of the present invention is easy to mass-produce because the manufacturing process is simple and efficient.

[0048] A matching layer (200) according to one embodiment of the present invention may be composed of a light porous material in the form of a membrane with low density and velocity, rather than a general porous material, in order to minimize the acoustic impedance difference with air and increase the energy transfer effect. Here, 'light' means using a material with low density and velocity to lower the acoustic impedance value. In one embodiment, the matching layer (200) must have a thickness corresponding to approximately λ / 4. Here, λ represents the wavelength when ultrasound propagates through the matching layer, i.e., the wavelength of the matching layer.

[0049] A piezoelectric layer (300) according to one embodiment of the present invention may be a structure of a piezoelectric composite for improving the performance of the matching layer (200) by minimizing the difference in acoustic impedance with air. A piezoelectric layer (300) according to one embodiment of the present invention may be composed of a mixture of epoxy (302) and a piezoelectric element (303). A piezoelectric layer (300) according to one embodiment of the present invention may be manufactured in a 2-2 or 1-3 structure mixed in a grid shape for ease of the manufacturing process. In a piezoelectric composite, a 2-2 or 1-3 structure refers to a classification based on the geometric arrangement of a piezoelectric element, which is a piezoelectric material, and epoxy, which is a non-piezoelectric material. A 2-2 structure refers to a structure in which the piezoelectric material and the non-piezoelectric material are alternately arranged in a plate shape parallel to each other, and a 1-3 structure refers to a structure in which the piezoelectric material has one-dimensional continuity in the vertical direction and the non-piezoelectric material fills it to have three-dimensional continuity. According to an embodiment, the piezoelectric layer (300) may be a multilayer piezoelectric element structure capable of further increasing the transmitted and received ultrasonic energy.

[0050] A back layer (400) according to one embodiment of the present invention may be a lightweight back layer having an acoustic impedance value smaller than that of a piezoelectric layer (300) to increase the intensity of ultrasonic waves transmitted and received in an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0051] Each component included in an air-coupled ultrasonic transducer according to one embodiment of the present invention operates organically with one another, thereby enabling the transmission and reception of high-intensity ultrasonic waves of megahertz or higher.

[0052] FIG. 2 is a diagram showing the configuration of a single-frequency or multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0053] FIG. 2(a) shows a single-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention. The acoustic metastructure (10_1) of FIG. 2(a) can be applied to the acoustic metastructure (100) of FIG. 1.

[0054] Referring to FIG. 2(a), a single-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention may include an acoustic metastructure (10_1), a matching layer (30_1), a piezoelectric layer (50_1), and a back layer (60_1).

[0055] The acoustic metastructure (10_1) may include at least one plate (1), a support (2), and / or a wire (3) and a through hole (4) provided in at least one plate (1). In the plate (1) provided with the through hole (4), the wire (3) and the through hole (4) may be arranged side by side in the same direction. The structure of the wire (3) and the through hole (4) can amplify the intensity of the ultrasound. In the drawings, the elements included in the air-coupled ultrasonic transducer are depicted as being square, but the shapes of the plate (1) and the through hole may each be circular or triangular, and the shapes of the elements included in the air-coupled ultrasonic transducer do not limit the scope of the invention.

[0056] The acoustic metastructure (100) may be fabricated to have a predetermined diameter (d) of the wire (3), a spacing (s) between the wires (3), and / or an air gap (g) between the wires of the acoustic metastructure (10_1) and the ultrasonic transducer aperture surface. The diameter (d) of the wire (3), the spacing (s) between the wires (3), and / or the air gap (g) between the wire (3) and the ultrasonic transducer aperture surface may be determined according to Fabry-Perot resonant cavity conditions. The diameter (d) of the wire (3), the spacing (s) between the wires (3), and / or the air gap (g) between the wires (10_1) of the acoustic metastructure and the ultrasonic transducer aperture surface are associated with the center frequency of the ultrasound. Details regarding this are described later in FIG. 6.

[0057] FIG. 2(b) shows a multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention. The acoustic metastructure (10_2) of FIG. 2(b) can be applied to the acoustic metastructure (100) of FIG. 1.

[0058] Referring to FIG. 2(b), a multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention may include an acoustic metastructure (10_2), a matching layer (30_2), a piezoelectric layer (50_2), and a back layer (60_2).

[0059] A multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention may be manufactured by varying the diameter and spacing of the wires according to the target frequency. Referring to FIG. 2(b), for a high frequency (f1), the diameter of the wires, the spacing between the wires, and the air gap between the wires and the surface of the ultrasonic transducer aperture may be d1, s1, and g1, respectively. For a low frequency (f2), the diameter of the wires, the spacing between the wires, and the air gap between the wires and the surface of the ultrasonic transducer aperture may be d2, s2, and g2, respectively. The acoustic metastructure portion and the transducer portion for the f1 frequency may be referred to as the first acoustic metastructure and the first transducer, respectively, and the acoustic metastructure portion and the transducer portion for the f2 frequency may be referred to as the second acoustic metastructure and the second transducer, respectively. The first transducer may include a first matching layer, a first piezoelectric layer, and a first back layer. The second transducer may include a second matching layer, a second piezoelectric layer, and a second back layer.

[0060] The first matching layer and the second matching layer are bonded to one surface of the first acoustic metastructure and the second acoustic metastructure, respectively, and may be composed of a porous material in the form of a membrane in which micro-sized holes are formed. The first piezoelectric layer and the second piezoelectric layer are bonded to one surface of the first matching layer and the second matching layer, respectively, and may be composed of a piezoelectric composite containing a piezoelectric element and epoxy. The first back layer and the second back layer may be composed of a material having an acoustic impedance value smaller than that of the first piezoelectric layer and the second piezoelectric layer, respectively. d1 and d2 may have different values, s1 and s2 may have different values, and g1 and g2 may have different values. At this time, each element included in the multi-frequency air-coupled ultrasonic transducer according to one embodiment of the present invention may operate separately or simultaneously depending on the frequency. Accordingly, ultrasonic energy having f1 frequency and f2 frequency as center frequencies may be amplified simultaneously or separately.

[0061] FIG. 3 is a diagram showing the process of fabricating an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0062] By using an acoustic metastructure fabricated according to the method for fabricating an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention illustrated in FIG. 3, a device that satisfies the essential design conditions of an acoustic metastructure required for transmitting and receiving high-frequency ultrasonic waves can be fabricated.

[0063] Referring to FIG. 3(a), a method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention may include the step of creating a through hole (104) in a plate (101) that is identical or similar in shape and size to the ultrasonic transducer aperture.

[0064] Referring to FIG. 3(b), a method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention may include the step of creating a number of straight grooves in a through hole (104) using a micro-cutting saw (102). Depending on the embodiment, the grooves may be created using a 3D printer, and the method of creating straight grooves does not limit the scope of the present invention.

[0065] Referring to FIG. 3(c), a method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention may include the step of coupling solid materials having a large reflection coefficient with selected air, such as metal-plated wires or metal wires (103), into a straight groove inside a through hole (104).

[0066] Referring to FIG. 3(d), a method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention may include the step of fixing metal wires (103) using a support (102).

[0067] Referring to FIG. 3(e), a method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention may include, after the step of fixing metal wires (103) using a support (102), a step of deforming the acoustic metastructure (100) into a curved shape, such as a spherical or cylindrical shape, according to the shape of the air-coupled ultrasonic transducer (600) in order to obtain more focused energy.

[0068] Referring to FIG. 3 (f), an acoustic metastructure is shown that has been completed according to the method for manufacturing an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0069] In order for the frequency of an air-coupled ultrasonic transducer to increase to units of megahertz or higher, the diameter of the wires and the width between the wires must be reduced to units of hundreds to tens of micrometers. Conventional technologies such as 3D printers have technical limitations in fabricating such microstructures. However, the method for fabricating an acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention enables the fabrication of an acoustic metastructure even when the diameter and spacing of the wires must be very small, facilitates the alignment of the wires, and simplifies the overall fabrication process, making it suitable for mass production.

[0070] FIG. 4 is a diagram illustrating a method for precisely adjusting the air gap between the wires of an acoustic metastructure and the aperture surface of an air-coupled ultrasonic transducer according to one embodiment of the present invention.

[0071] Referring to FIG. 4(a), a method for precisely adjusting the air gap between the wires of an acoustic metastructure and the aperture surface of an air-coupled ultrasonic transducer according to one embodiment of the present invention may be a method of precisely adjusting the air gap (g) to a multiple of λ by rotating a housing (30) having screw threads (20) relative to each other. Here, λ represents the wavelength when ultrasound propagates in air, i.e., the air wavelength.

[0072] Referring to FIG. 4(b), a method for precisely adjusting the air gap between the wires of an acoustic metastructure and the surface of an air-coupled ultrasonic transducer aperture according to one embodiment of the present invention may be a method of adjusting the thickness of the plate itself or a method of providing a height adjustment member (40) on one side of the plate to precisely adjust the air gap (g) by a multiple of λ. Here, λ represents the air wavelength. In another embodiment, when the top of the plate faces the ultrasonic transducer aperture, a method for precisely adjusting the air gap between the wires of an acoustic metastructure and the surface of an air-coupled ultrasonic transducer aperture according to one embodiment of the present invention may be a method of precisely adjusting the air gap (g) by changing the thickness of an attached support member (12) by a multiple of λ.

[0073] In FIG. 4, the position of the screw thread (20), the position and shape of the part where the height adjustment bracket (40) is mounted, etc., can be applied in various ways, and this does not limit the scope of the invention. In addition to the methods of FIG. 4, other methods can be applied in which a very fine gap can be maintained between the wires of the acoustic metastructure and the aperture of the ultrasonic transducer.

[0074] In this specification, the acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention can be detached and replaced depending on the purpose of use. In other words, that is, when the acoustic metastructure is combined with a piezoelectric element and other parts, when thickness adjustment of the support and height adjustment member of the acoustic metastructure is required, or when repair is required, the acoustic metastructure of an air-coupled ultrasonic transducer according to one embodiment of the present invention can be detached and replaced.

[0075] FIG. 5 is a diagram showing an air-coupled ultrasonic transducer structure composed of a single piezoelectric layer and multiple piezoelectric layers according to one embodiment of the present invention.

[0076] The air-coupled ultrasonic transducer structure according to the embodiment of Fig. 5 can be applied not only to single-element type but also to various array-type ultrasonic transducers such as annular type, ring type, linear and phase array type.

[0077] Figure 5(a) shows a single piezoelectric layer air-coupled ultrasonic transducer structure, and Figures 5(b), (c), and (d) show multiple multi-piezoelectric layer air-coupled ultrasonic transducer structures.

[0078] The matching layer (200) serves to reduce the difference in impedance values ​​between the ultrasonic piezoelectric element and air, and can be designed to have the characteristic of maintaining the shape of the transmitted ultrasonic waves as much as possible. In particular, since the acoustic impedance value must be very small, the matching layer (200) may be a lightweight porous material in the form of a membrane having micro-sized fine holes.

[0079] In the case of the piezoelectric layer (300), generally, if a single piezoelectric element (303) is used, the difference in acoustic impedance with the medium is very large, so the transmitted and received ultrasonic energy is greatly reduced. Therefore, a piezoelectric composite (piezo-composite) is used in which the piezoelectric element (303) is cut and epoxy (302) is poured to fill the gap. FIG. 5 (a) shows the configuration of such a piezoelectric layer. This allows the overall acoustic impedance value to be lowered because the acoustic impedance value of the epoxy is low.

[0080] In a multi-piezoelectric layer air-coupled ultrasonic transducer structure, the polling direction and ground of the piezoelectric element (303) and the signal line position can be set as in (b), (c), or (d) of FIG. 5. Specifically, the piezoelectric layer (300) according to FIG. 5 (b), (c), or (d) is a multi-piezoelectric layer having a plurality of piezoelectric layers. It may have a stacked structure in which a piezoelectric element and an epoxy are mixed and arranged alternately.

[0081] For example, according to FIG. 5(c), the multi-piezoelectric layer (300) may include a first piezoelectric layer (31), a second piezoelectric layer (32), and a third piezoelectric layer (33). The polling direction of the first piezoelectric layer (31) and the second piezoelectric layer (32) is opposite, and the polling direction of the second piezoelectric layer (32) and the third piezoelectric layer (33) is opposite. Since the polling direction of adjacent piezoelectric layers is opposite, the plurality of piezoelectric layers included in the multi-piezoelectric layer (300) may be referred to as alternating layers. In other words, the polling direction of the multi-piezoelectric layer may be opposite for each alternating layer. The signal line and ground of the multi-piezoelectric layer may be applied alternately to the cross-section of each alternating layer.

[0082] For example, according to FIG. 5(d), the multi-piezoelectric layer (300) may include a fourth piezoelectric layer (34), a fifth piezoelectric layer (35), a sixth piezoelectric layer (36), and a seventh piezoelectric layer (37). The poling directions of the fourth piezoelectric layer (34) and the fifth piezoelectric layer (35) are opposite, the poling directions of the fifth piezoelectric layer (35) and the sixth piezoelectric layer (36) are opposite, and the poling directions of the sixth piezoelectric layer (36) and the seventh piezoelectric layer (37) are opposite. That is, the poling directions of the multi-piezoelectric layer may be opposite for each alternating layer. The signal lines and ground of the multi-piezoelectric layer may be applied alternately to the cross-section of each alternating layer.

[0083] The piezoelectric elements (303) of each piezoelectric layer may be of the same type or different types, and may be annular, ring-shaped, or array-shaped. In this multi-piezoelectric layer air-coupled ultrasonic transducer structure, the transmitted and received energy can be further increased.

[0084] For the back layer (400), a lightweight back layer with a low acoustic impedance value may be used to increase the intensity of the transmitted and received ultrasonic waves. For the back layer (400), a material with low density and velocity is suitable.

[0085] Figure 6 is a graph showing the experimental performance evaluation results of an air-coupled ultrasonic transducer manufactured according to one embodiment of the present invention.

[0086] Figure 6 (a) is a graph showing the magnitude of the ultrasonic signal according to time and frequency when the air-coupled ultrasonic transducer has no acoustic metastructure, and Figure 6 (b) is a graph showing the magnitude of the ultrasonic signal according to time and frequency when the air-coupled ultrasonic transducer has an acoustic metastructure.

[0087] The air gap (g) between the wires of the acoustic metastructure determining the amplification rate and the surface of the ultrasonic transducer aperture can be determined by a multiple of λ / 2. Here, λ represents the air wavelength.

[0088] In one embodiment, when d ≈ 100 μm, s ≈ 30 μm, and g ≈ 161 μm, the air-coupled ultrasonic transducer according to one embodiment of the present invention can amplify ultrasound having a center frequency of about 1 MHz. Here, d represents the diameter of the wire, s represents the spacing between the wires, and g represents the air gap between the wires of the acoustic metastructure and the aperture surface of the ultrasonic transducer.

[0089] In addition, the first amplification may occur when g is approximately 161 μm, corresponding to λ / 2, and the second amplification may occur when g is approximately 322 μm, corresponding to λ.

[0090] Referring to Figures 6 (a) and (b), it can be seen that when the air-coupled ultrasonic transducer has an acoustic metastructure, the magnitude of the ultrasonic signal at 1 MHz increases by more than 100% when the gap is 161 μm and 322 μm compared to when the air-coupled ultrasonic transducer does not have an acoustic metastructure.

[0091] Referring to Fig. 6(b), it can be seen that there is a difference in amplification rate when the air gap (g) between the wires of the acoustic metastructure and the surface of the ultrasonic transducer aperture is 161 μm and when it is 322 μm.

[0092] FIG. 7 is a flowchart illustrating a method for manufacturing an air-coupled ultrasonic transducer manufactured according to one embodiment of the present invention.

[0093] A method for manufacturing an air-coupled ultrasonic transducer according to one embodiment of the present invention includes the step (S700) of creating a through hole in a plate that is identical in shape and size to the ultrasonic transducer diameter. Here, the plate is a component included in an acoustic metastructure.

[0094] A method for manufacturing an air-coupled ultrasonic transducer according to one embodiment of the present invention includes the step (S702) of creating a predetermined number of straight grooves in a through hole.

[0095] A method for manufacturing an air-coupled ultrasonic transducer according to one embodiment of the present invention includes the step (S704) of coupling a plurality of wires into straight grooves. The plurality of wires may have the same material, shape, diameter, and length. A plurality of supports may be configured so that the thickness of the plurality of supports can be varied by a multiple of λ / 2. Here, λ is the wavelength when the ultrasound propagates in air.

[0096] A method for manufacturing an air-coupled ultrasonic transducer according to one embodiment of the present invention includes a step (S706) of fixing a plurality of wires using a plurality of supports. After the step S706 of fixing a plurality of wires using a plurality of supports, the method may further include a step of transforming an acoustic metastructure from a planar shape to a spherical shape or a cylindrical shape according to the shape of the air-coupled ultrasonic transducer.

[0097]

[0098] [National R&D projects that supported this invention]

[0099] [Project ID] 2710000053

[0100] [Assignment No.] 00141273

[0101] [Ministry Name] Ministry of Science and ICT

[0102] [Project Management (Specialized) Agency Name] Pan-Governmental Medical Device Research & Development Project Group

[0103] [Research Project Name] Pan-Governmental Full-Cycle Medical Device Research and Development (Ministry of Science and ICT)

[0104] [Research Project Title] High-performance air-coupled ultrasound for non-invasive hearing function improvement

[0105] Probe Module Development

[0106] [Name of Project Performing Organization] Dongguk University Industry-Academic Cooperation Foundation

[0107] [Research Period] 2024.01.01 ~ 2024.12.31

[0108]

[0109] [Project ID] 2710005541

[0110] [Assignment No.] 00357960

[0111] [Ministry Name] Ministry of Science and ICT

[0112] [Name of Project Management (Specialized) Agency] National Research Foundation of Korea

[0113] [Research Project Name] Individual Basic Research (Ministry of Science and ICT)

[0114] [Project Title] Development of Core Technology for Skin Burn Diagnosis Using Non-Contact Air-Coupled Ultrasound

[0115] [Name of Project Performing Organization] Dongguk University Industry-Academic Cooperation Foundation

[0116] [Research Period] May 1, 2024 – April 30, 2025

Claims

1. An acoustic metastructure configured to include a plate having a through hole, a plurality of wires disposed in straight grooves formed in the through hole, and two supports attached to the plurality of wires; A matching layer bonded to one surface of the above acoustic metastructure and composed of a membrane-shaped porous material having micro-sized fine holes formed therein; A piezoelectric layer bonded to one surface of the above-mentioned matching layer and composed of a piezoelectric composite including a piezoelectric element and epoxy; A back layer comprising a material bonded to one surface of the piezoelectric layer and having an acoustic impedance value smaller than that of the piezoelectric layer. Air-coupled ultrasonic transducer.

2. In Paragraph 1, The above-mentioned through hole is identical in shape and size to the diameter of the ultrasonic transducer, Air-coupled ultrasonic transducer.

3. In Paragraph 1, The above plurality of wires are plated with metal or composed of metal, and The diameter of the plurality of wires, the spacing between the plurality of wires, or the air gap between the plurality of wires and the surface of the ultrasonic transducer aperture is determined according to the frequency. Air-coupled ultrasonic transducer.

4. In Paragraph 1, The acoustic metastructure is planar, spherical, or cylindrical depending on the shape of the air-coupled ultrasonic transducer. Air-coupled ultrasonic transducer.

5. In Paragraph 3, The above acoustic metastructure is configured to further include a height adjustment member attached to one side of the plate, Air-coupled ultrasonic transducer.

6. In Paragraph 5, The air gap is determined as a multiple of λ / 2 by adjusting at least one of the thickness of the plate, the thickness of the two supports, or the thickness of the height adjuster, and The above λ is the wavelength when ultrasound propagates in air, Air-coupled ultrasonic transducer.

7. In Paragraph 3, By adjusting the housing including the screw threads, the plurality of wires and the air gap are determined to be a multiple of λ / 2, and The above λ is the wavelength when ultrasound propagates in air, Air-coupled ultrasonic transducer.

8. In Paragraph 1, The above acoustic metastructure is detachable and mountable. Air-coupled ultrasonic transducer.

9. In Paragraph 1, The above-mentioned matching layer is composed of a porous material in the form of a membrane in which micro-scale micro-holes are formed, and the thickness of the above-mentioned matching layer is L / 4, and The above L is the wavelength when the ultrasound propagates through the matching layer, Air-coupled ultrasonic transducer.

10. In Paragraph 1, The above piezoelectric composite is formed by mixing the piezoelectric element and the epoxy and arranging them alternately, and The thickness of the above piezoelectric composite is an odd multiple of P / 2, and The above P is the wavelength when the ultrasound propagates through the piezoelectric composite, Air-coupled ultrasonic transducer.

11. In Paragraph 1, The above piezoelectric layer is a multi-piezoelectric layer having a plurality of piezoelectric layers, and The above piezoelectric composite is a laminated structure in which the piezoelectric element and the epoxy are mixed and arranged alternately, and The poling direction of the above multi-piezoelectric layer is opposite for each alternating layer, and The signal lines and ground of the above-mentioned multi-piezoelectric layers are alternately applied to the cross-section of each alternating layer, Air-coupled ultrasonic transducer.

12. In Paragraph 11, The piezoelectric element included in each of the above multiple piezoelectric layers is of the same or different type and is an ultrasonic transducer that is annular, ring-shaped, or array-shaped.

13. A first acoustic metastructure for a first frequency configured to include a first plate having a first through hole formed therein, a plurality of first wires disposed in straight grooves formed in the first through hole, and two first supports attached to the plurality of first wires; A second acoustic metastructure for a second frequency configured to include a second plate having a first through hole, a plurality of second wires disposed in straight grooves formed in the second through hole, and two second supports attached to the plurality of second wires; A first transducer for the first frequency, bonded to one surface of the first acoustic metastructure and comprising a first matching layer, a first piezoelectric layer, and a first back layer; and A second transducer for the second frequency, which is bonded to one surface of the second acoustic metastructure and includes a second matching layer, a second piezoelectric layer, and a second back layer; The diameters of the first wires and the second wires are different, and The spacing between the first wires and the spacing between the second wires are different, and The air gap between the plurality of first wires of the first acoustic metastructure and the surface of the first ultrasonic transducer aperture and the air gap between the plurality of second wires of the second acoustic metastructure and the surface of the second ultrasonic transducer aperture are different. Air-coupled ultrasonic transducer for multiple frequencies.

14. In Paragraph 13, The first matching layer and the second matching layer are each bonded to one surface of the first acoustic metastructure and the second acoustic metastructure, and are composed of a porous material in the form of a membrane in which micro-sized micro-holes are formed. The first piezoelectric layer and the second piezoelectric layer are each bonded to one surface of the first matching layer and the second matching layer, respectively, and are composed of a piezoelectric composite including a piezoelectric element and epoxy. The first back layer and the second back layer are composed of a material having an acoustic impedance value smaller than that of the first piezoelectric layer and the second piezoelectric layer, respectively. Air-coupled ultrasonic transducer for multiple frequencies.

15. In Paragraph 13, The first frequency has a value different from the second frequency, Ultrasonic energy having the first frequency and the second frequency as center frequencies is amplified simultaneously or at different times, Air-coupled ultrasonic transducer for multiple frequencies.

16. A method for manufacturing an air-coupled ultrasonic transducer, A step of creating a through hole in a plate that is identical in shape and size to the ultrasonic transducer aperture, wherein the plate is included in an acoustic metastructure; A step of creating a predetermined number of straight grooves in the above-mentioned through hole; A step of joining a plurality of wires to the straight grooves; and The method includes the step of fixing the plurality of wires using a plurality of supports; The plurality of supports are configured so that the thickness of the plurality of supports can be varied as a multiple of λ / 2, and The above λ is the wavelength when ultrasound propagates in air, method.

17. In Paragraph 16, After the step of fixing the plurality of wires using the plurality of supports, The method further comprises the step of transforming the acoustic metastructure into a spherical or cylindrical shape according to the shape of the air-coupled ultrasonic transducer. method.

18. In Paragraph 16, Multiple of the above wires are identical in material, shape, diameter, and length, method.

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