Ultrasonic vibrator and ultrasonic treatment device having the same

Abstract

The device comprises an oscillator body (11) and an oscillator cover (12). The radiating surface of the oscillator body (11) is curved. The oscillator body (11) generates ultrasonic waves. The oscillator cover (12) covers the radiating surface of the oscillator body (11) and serves as an acoustic matching layer. The shape of the oscillator cover (12) extends along the radiating surface (11a) of the oscillator body (11). This provides an ultrasonic oscillator with high durability and the ability to transmit sound waves more stably to deep locations.

Description

Technical Field

[0001] The present invention relates to an ultrasonic transducer and an ultrasonic therapy device having the ultrasonic transducer, wherein the transducer body that generates ultrasonic waves is covered by a transducer cover. Background Technology

[0002] Previously, a device for treating dementia was known, comprising: a plurality of ultrasound probes; an ultrasound transducer disposed on the ultrasound probes and transmitting unfocused ultrasound energy to the brain; and an ultrasound generating device connected to the ultrasound probes (for example, see Patent Document 1).

[0003] The device is configured to enhance the expression of endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) by irradiating diseased areas such as the brain and heart with LIPUS (Low-Intensity Pulsed Ultrasound), thereby promoting angiogenesis and neurogenesis.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018 / 181991 Summary of the Invention

[0007] -The technical problem the invention aims to solve-

[0008] However, although conventional ultrasound transducers can irradiate the entire brain and heart as targets using one or more transducers, the sound waves irradiated from their radiating surface are difficult to reach deep into the brain with constant pressure due to vibration patterns and interference from the sound waves.

[0009] Previous ultrasonic transducers had the following problems: due to the special shape of the radiating surface, they had poor impact resistance, and the protective film for waterproofing that was pasted on the surface was easily peeled off due to heat and impact.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide an ultrasonic transducer with high durability and capable of transmitting sound waves to deep parts more stably.

[0011] - Technical solutions used to solve technical problems -

[0012] To achieve the above objective, in this invention, the radiating surface of the oscillator body is covered by a cover that extends along the curved shape of the oscillator body.

[0013] Specifically, in the first aspect of the invention, it includes an oscillator body and an oscillator cover, wherein the radiating surface of the oscillator body is curved, and the oscillator body generates ultrasonic waves.

[0014] The oscillator cover covers the radiating surface of the oscillator body and serves as an acoustic matching layer.

[0015] The oscillator cover has a shape that extends along the radial surface of the oscillator body.

[0016] According to the above configuration, since the radiating surface of the oscillator body is curved, the irradiated waveform spreads and advances simultaneously. Furthermore, the sound propagation within the oscillator cover is determined by Snell's law; however, since the oscillator cover is typically made of a solid material such as molded resin, the speed of sound is faster than that of water or a living body, resulting in a higher refractive index. Consequently, in terms of the irradiation range from the oscillator cover, irradiation occurs over a larger area compared to the case without the oscillator cover. This allows for more consistent irradiation. Moreover, since the distance from the oscillator body (which acts as a heat source) to the living body can be maintained using the oscillator cover, the problem of surface temperature rise can be mitigated.

[0017] The second aspect of the invention is based on the first aspect, wherein the radiating surface of the oscillator body is convex spherical.

[0018] It is generally believed that the waves emanating from the radiating surface of the oscillator are a collection of point light sources with the radiating surface as the reference. If the radiating surface is a convex sphere, there will be areas where the sound from the point light sources interferes with each other, weakening or strengthening each other, ultimately failing to create a constant sound field. However, according to the above configuration, by covering the radiating surface with an oscillator cover, a more constant illumination can be achieved from a larger surface.

[0019] The third aspect of the invention is based on the first aspect, wherein the thickness of the oscillator cover is constant.

[0020] Based on the above configuration, there is no need to make fine adjustments to the thickness of the lid, making it easy to manufacture.

[0021] The fourth aspect of the invention is based on the third aspect, wherein when the wavelength of the material of the oscillator cover is λ, the thickness of the oscillator cover is λ / 8 or more and 3λ or less, excluding the ranges of λ / 8 ± λ / 40, λ / 4 ± λ / 40 and λ / 2 ± λ / 40.

[0022] Based on the above configuration, a resonant structure is formed. By intentionally deviating from the thickness near the maximum transmission thickness (λ / 8, λ / 4, and λ / 2), a vibrator cover that serves as an acoustic matching layer with small irradiation deviation as an ultrasonic transducer can be obtained. This is because: if the thickness is slightly deviated from the maximum amplitude, the problem of drastic changes in irradiation energy can be avoided. If the thickness of the vibrator cover is too thin, the diffusion effect caused by refraction becomes smaller. Furthermore, considering not only acoustic performance but also manufacturability and the durability of the vibrator cover, the thickness of the vibrator cover is preferably thicker than λ / 8. If the thickness is greater than 3λ, the attenuation becomes too large, making it difficult to use practically.

[0023] The fifth aspect of the invention is based on the first aspect, wherein the thickness of the oscillator cover is not constant but varies.

[0024] According to the above configuration, by making the thickness of the oscillator cover not constant but varying, it is possible to control the expansion to an appropriate extent.

[0025] In the sixth aspect of the invention, the vibrator cover is formed of a material having an elastic modulus of 2000 MPa or more and 10000 MPa or less, and an inherent acoustic impedance of 1.5 MPa·s / m or more and 10 MPa·s / m or less.

[0026] According to the above configuration, the elastic modulus of the material of the oscillator cover is kept at an appropriate level, and the sound speed is faster than that of water and living bodies, so the refractive index increases and the range of irradiation from the oscillator cover becomes larger.

[0027] The ultrasound therapy device of the seventh invention has an ultrasound transducer as described in any one of the first to sixth aspects of the invention, and a system for supplying energy to the ultrasound transducer for performing ultrasound vibrations.

[0028] According to the above configuration, for example, in an ultrasound therapy device that can treat angina pectoris or dementia by enhancing the expression of eNOS and VEGF, a constant sound pressure can be delivered to a deeper location, and the durability of the ultrasound transducer can be improved.

[0029] -The effects of the invention-

[0030] As described above, according to the present invention, by covering the radiating surface of the oscillator body with an oscillator cover having a shape extending along the radiating surface and serving as an acoustic matching layer, it is possible to obtain an ultrasonic oscillator with high durability and the ability to transmit sound waves more stably to deep locations. Attached Figure Description

[0031] Figure 1 This is a block diagram illustrating the general layout of an ultrasonic therapy apparatus having an ultrasonic transducer according to an embodiment of the present invention.

[0032] Figure 2 This is an enlarged cross-sectional view of an ultrasonic transducer.

[0033] Figure 3 This is a cross-sectional view of the oscillator body and oscillator cover. Figure 3 (a) shows the case where the thickness of the oscillator cover is constant. Figure 3 (b) shows the case where the thickness of the oscillator cover is thinner in the center. Figure 3 (c) shows the case where the thickness of the center of the oscillator cover is relatively thick.

[0034] Figure 4 This is a graph showing the simulation results of the sound pressure level without a cover.

[0035] Figure 5 middle, Figure 5 (a) to (c) show the relationship with Figure 3 Figures showing the simulation results of the sound pressure levels corresponding to (a) to (c).

[0036] Figure 6 middle, Figure 6 (a) shows the simulation results without a lid. Figure 6 (b) shows the simulation results when the wavelength of the cover material is λ / 8. Figure 6 (c) shows the simulation results when the wavelength of the cover material is λ / 3.4, where the wavelength of the cover material is set to λ.

[0037] Figure 7 middle, Figure 7 (a) and (b) are figures showing the simulation results when covers with thicknesses of λ / 4 and λ / 3.4 are installed, respectively. Detailed Implementation

[0038] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0039] Figure 1 The general layout of an ultrasound therapy device 20 having an ultrasound transducer 10 according to an embodiment of the present invention is shown. The use of the ultrasound transducer 10 is not limited to the ultrasound therapy device 20 configured to enhance the expression of eNOS and VEGF by transmitting frequencies within the ultrasound frequency range and irradiating the heart and brain using LIPUS, thereby enabling the treatment of angina pectoris, heart failure with preserved ejection fraction (HFpEF), or dementia.

[0040] The general structure of the ultrasound therapy device 20 is described below. In the ultrasound therapy device 20, the control unit 4, which serves as the protocol management system within the device, transmits treatment information input by the operator 1, such as the treatment site 2 and patient information 3, as signals. The transmission condition control unit 5 controls the transmission waveform, and the treatment protocol control unit 6 controls the treatment protocol. The signal is then transmitted from the transmission unit 7 and irradiated onto the brain via the ultrasound transducer 10 through the treatment site 2 (e.g., the head). The control unit 4, the transmission condition control unit 5, and the treatment protocol control unit 6 are, for example, composed of one or more microcomputers built into the ultrasound therapy device 20.

[0041] When there are two or more ultrasonic transducers 10, the ultrasonic transducers 10 are branched into multiple branches in the transmitting section 7, and each ultrasonic transducer 10 is irradiated. For example, when the ultrasonic transducers 10 are used in headphones, a pair of left and right ultrasonic transducers 10 are required.

[0042] Information from the ultrasound therapy device 20 is displayed to the operator 1 via the display 8. Input to the ultrasound therapy device 20 is made via external input methods such as a keyboard or mouse, touch input when the display 8 is a touch screen, or by inserting a USB memory device.

[0043] like Figure 2 As shown in the enlarged view, the ultrasonic transducer 10 used includes a transducer body 11, which is a diffuser transducer with a curved radiating surface 11a. Because the radiating surface 11a of the transducer body 11 is curved, the emitted waveform diffuses and advances simultaneously.

[0044] As a result, the entire treatment site 2 can be irradiated. For example, in the case of the brain, it is preferable that the irradiation range is extended at an angle of 77 degrees or more.

[0045] The ultrasonic transducer 10 has a transducer cover 12, which is used to ensure biological safety and protect the transducer body 11 from impact damage. On the back side of the transducer cover 12 are a transducer housing 13 covering the transducer body 11 and a transducer cable 14 for supplying power to the transducer body 11. The transducer housing 13 can be integrated with the transducer cover 12 or it can be separate from the transducer cover 12.

[0046] The main body 11 of the oscillator can be, for example, a piezoelectric (PZT) element, a piezoelectric element made of homopolymer of vinylidene fluoride (VdF), a fluoropolymer, barium titanate (BaTiO3), a relaxor piezoelectric single crystal (PIN-PmN-PT), etc., a component known as a capacitive micromachined ultrasonic transducer (CMUT), a piezoelectric micromachined ultrasonic transducer (PMUT), or a component manufactured using semiconductor technology.

[0047] The frequency (cycle number) of the ultrasonic wave applied to the transducer body 11 corresponds to the frequency of the transducer body 11. Its wave number is 1 cycle or more and 64 cycles or less, preferably 24 cycles or more and 40 cycles or less. The average intensity (Ispta, Spatial Peak Temporal Average Intensity) within the pulse width is not specifically specified, but is 720 mW / cm². 2 The preferred value is 150mW / cm. 2 the following.

[0048] The frequency of the oscillator body 11 (the frequency near the resonant or anti-resonant point) is, for example, above 100 kHz and below 10 MHz. The shape of the oscillator body 11 is a convex spherical surface. For example, Figure 2 The radius R of the sphere shown is 10 mm or more and 30 mm or less, and the opening diameter D is 10 mm or more and 50 mm or less. Furthermore, a backing made of air, oil, or a solid is provided on the back side of the transducer body 11. It should be noted that the backing refers to a component arranged on the back side of the transducer body 11 that suppresses the rearward propagation of ultrasonic waves and helps to shorten the pulse width.

[0049] The material used for the vibrator cover 12 is preferably a material with an elastic modulus of 2000 MPa or more and 10000 MPa or less, and an inherent acoustic impedance of 1.5 MPa·s / m or more and 10 MPa·s / m or less.

[0050] Furthermore, if the wavelength of the material of the oscillator cover 12 is set to λ, the oscillator cover 12 preferably has a thickness of λ / 8 or more and 3λ or less, excluding the ranges of λ / 8 ± λ / 40, λ / 4 ± λ / 40, and λ / 2 ± λ / 40.

[0051] The shape of the oscillator cover 12 is preferably an extension of the radial surface of the oscillator body 11.

[0052] Materials used for the vibrator cover 12 include, for example, synthetic resin materials such as PPE (polyphenylene ether), PBT (polybutylene terephthalate), ABS (acrylonitrile-butadiene-styrene), LDPE (low-density polyethylene), PS (polystyrene), NORYL (registered trademark, modified polyphenylene ether), Valox (Valox), Pebax (polyether block polyamide); composite materials of carbon, graphite, and metals with resins, etc.

[0053] The adhesive used to bond the back of the oscillator cover 12 to the radiating surface 11a of the oscillator body 11 is preferably, for example, an epoxy adhesive, a silicone adhesive, etc.

[0054] The waterproofness of the vibrator cover 12 can be achieved by the material of the vibrator cover 12 itself, or by applying a thin waterproof coating such as Parylene (a series of polymers obtained from paraxylene) within a range that does not affect the acoustics.

[0055] Regarding insulation, the portion of the vibrator cover 12 that comes into contact with the patient requires insulation. For example, since the vibrator body 11 has a GND (grounding) layer on its surface, an additional insulating layer is required if the thickness of the vibrator cover 12 is less than 0.4 mm, or if the withstand voltage is less than 1500 V. Examples of insulating layers include polyvinyl chloride (PVC) coating, fluoropolymer (ETFE) coating, polyethylene coating, nylon coating, epoxy coating, polyphenylene sulfide (PPS) / polyether ether ketone (PEEK) coating, etc.

[0056] - Example -

[0057] Normally, waves irradiated from the radiating surface 11a of the oscillator body 11 are considered as a collection of point light sources with reference to the radiating surface 11a. Due to the spherical convex shape of the oscillator body 11, there will be regions where the sound from the point light sources is weakened or strengthened by each other due to interference caused by the shape, and ultimately will not become a constant sound field.

[0058] In this embodiment, in order to solve this problem, the oscillator cover 12 is installed on the radiating surface 11a of the oscillator body 11.

[0059] By utilizing the effect of the oscillator cover 12, constant sound pressure level illumination can be achieved over a larger area. The propagation of sound within the oscillator cover 12 is determined by Snell's law (the law of refraction), but the speed of sound in the material of the oscillator cover 12, namely resin, is generally faster than that in water or living matter (the speed of sound in water is 1480 m / s at 20°C), thus increasing its refractive index. As a result, in terms of the area illuminated from the oscillator cover 12, illumination occurs over a larger surface area compared to the case without the oscillator cover 12. This allows for more constant illumination.

[0060] Figure 3 An example showing the shape of the oscillator body 11 and the oscillator cover 12 is provided. Figure 3 (a) The oscillator cover 12 has a uniform and constant thickness; Figure 3 (b) The central part of the oscillator cover 12' is thinner; Figure 3 (c) The central part of the oscillator cover 12'' is thicker.

[0061] Here, when the wavelength of the material of the oscillator cover 12 is set to λ, Figure 3 (a) The thickness of the oscillator cover 12 is t = λ / 3.4; Figure 3 (b) The thickness of the center of the oscillator cover 12' is t = λ / 4, and the thickness of both ends is λ / 2; Figure 3 (c) The thickness of the center of the oscillator cover 12” is t=λ×3 / 4, and the thickness of both ends is λ / 2.

[0062] The results of the acoustic analysis are shown below. The acoustic analysis was conducted at an overall size of 80 mm and a frequency of 500 kHz, and the sound pressure level in dB is displayed in color using a linear scale.

[0063] Figure 4 The simulation results of the sound pressure level without a cover are shown. Figure 5 (a) to (c) show the relationship with Figure 3 Simulation results for sound pressure levels (a) to (c) are shown. It can be seen that, compared with... Figure 4 Compared to the case without the oscillator cover 12, in Figure 5 In cases (a) to (c) with vibrator covers 12, 12', and 12”, the sound pressure extends further into the depths and spreads uniformly over a larger area.

[0064] To achieve constant irradiation, the thickness of the oscillator cover 12 needs to be above a constant value. This is because if it is too thin, the diffusion effect caused by refraction will be reduced.

[0065] As a result of acoustic analysis, when the wavelength of the material of the oscillator cover 12 is λ, Figure 6 (a) Shows the case without a lid; Figure 6 (b) shows the case where the wavelength of the cover material is λ / 8; Figure 6 (c) shows the case where the wavelength of the cover material is λ / 3.4. It can be seen that, despite the attenuation caused by the vibrator cover 12, the sound pressure is uniform at deeper depths when the vibrator cover 12 is present. It can also be seen that when using a material with a wavelength greater than... Figure 6 (b) λ / 8 is thicker Figure 6 (c) With a λ / 3.4, higher levels of sound pressure can be applied to deeper locations. Therefore, the thickness of the cover is preferably at least greater than λ / 8.

[0066] If the speed of sound is set to 2200 m / s and the transmission frequency is set to 500 kHz, then λ / 8 = 0.55 mm. Considering not only acoustic performance, but also manufacturability and the durability of the vibrator cover 12, the thickness of the vibrator cover 12 is preferably thicker than λ / 8.

[0067] It can also be considered that, in addition to expanding the sound pressure by utilizing the difference in sound velocity, the vibrator cover 12 also functions as a sound matching layer. If the material used for the vibrator cover 12 is a piezoelectric element, its impedance is approximately 30 MPa·s / m. If the sound velocity of the vibrator cover 12 is set to 2200 m / s and the density of the resin material is set to 1.2 g / cm³, then... 3 The impedance is 2.6 MPa·s / m. In contrast, the impedance of water is 1.44 MPa·s / m; a value between PZT and water should be chosen. It can be considered that by utilizing the oscillator cover 12 to reduce reflections and redundant vibration modes at the interface, more efficient irradiation can be achieved. The result is conducive to constant irradiation.

[0068] In order to improve efficiency, a conventional ultrasonic transducer with an acoustic matching layer is designed with a thickness obtained by dividing the wavelength λ by 2×n (where n is an integer) (e.g., λ / 2, λ / 4, λ / 8, etc.). This is because by designing the conventional ultrasonic transducer with this thickness, the radiation surface of the matching layer becomes open, and the amplitude reaches its maximum.

[0069] However, if the thickness deviates even slightly, a sharp change in the irradiation energy will occur. This indicates that if the thickness, frequency, sound velocity of the cover, etc., change due to manufacturing deviations, deviations will occur as a device.

[0070] In this embodiment, the vibrator cover 12 is configured to serve as a vibrator cover with small irradiation deviation as an ultrasonic vibrator 10 and to act as an acoustic matching layer by deliberately deviating from the thickness at which maximum transmission can be achieved.

[0071] The method involves installing a vibrator cover 12 with a thickness obtained by dividing the wavelength λ of the material of the vibrator cover 12 by 2×n (n is an integer), for example, a thickness that deviates from λ / 2, λ / 4, or λ / 8 by more than λ / 40.

[0072] As an example, Figure 7 (a) and Figure 7(b) Simulation results are shown for covers with thicknesses of λ / 4 and λ / 3.4, respectively. It can be seen that the thickness difference is small, approximately λ / 23, but a significant difference exists in the sound pressure level. This means that since λ / 4 becomes a resonant structure, energy can be irradiated with very high efficiency at this thickness. However, this also means that the sound pressure level changes drastically due to the thickness variation. Furthermore, compared to the thickness of λ / 4, the thickness of λ / 3.4 exhibits a smaller localized sound pressure difference.

[0073] Furthermore, the heat generated by the ultrasonic transducer 10 during the transmission of ultrasonic waves is also a problem. Since the ultrasonic transducer 10 is in contact with the patient, this heat could potentially lead to burns or other complications. Although the upper limit of surface temperature rise is determined according to regulations, the problem of surface temperature rise can be mitigated by maintaining the distance between the heating element (transducer body 11) and the living body through the transducer cover 12.

[0074] Moreover, by making the thickness of the oscillator cover 12 not constant but varied, it is possible to control the expansion appropriately.

[0075] By intentionally making its thickness deviate from the usual design guidelines for acoustic matching layers, namely 1 / 2 wavelength, 1 / 4 wavelength, and 1 / 8 wavelength, the impact of thickness differences caused by manufacturing processes can be minimized.

[0076] Although the oscillator body 11 is prone to breakage when subjected to impact due to its shape, the impact resistance can be improved by attaching oscillator covers 12, 12', 12" made of resin material with high elastic modulus and thickness.

[0077] The ultrasound therapy device 20 of the present invention is a device capable of outputting ultrasound waves over a wide area of ​​the target site. By irradiating the brain and heart with a prescribed transmission waveform, it can enhance the expression of eNOS and VEGF, promote angiogenesis and neurogenesis, and treat angina pectoris, heart failure with preserved ejection fraction (HFpEF), or dementia. Ultrasound transducers 10 with convex curved surfaces suffer from inconsistent pressure at deeper locations due to vibration modes and sound wave interference. However, in this embodiment, the transducer cover 12 extends along the shape of the radiating surface 11a, and a resin that can be used as an acoustic matching layer is adhered to the radiating surface 11a. This suppresses unwanted vibration modes, mitigates the effects of interference, and allows for consistent irradiation to deeper locations even with the same output.

[0078] (Other implementation methods)

[0079] The above-described embodiments of the present invention can also adopt the following structure.

[0080] In other words, the above embodiment shows an example of using the ultrasonic transducer 10 in an ultrasonic therapy device 20, but the ultrasonic transducer 10 can also be used in ultrasonic cleaners, ultrasonic humidifiers, ultrasonic dispersion and emulsification machines, etc. The ultrasonic transducer 10 can also be used in fish detectors, ultrasonic diagnostic devices, ultrasonic flow meters, ultrasonic levels, etc.

[0081] In the above embodiment, the shape of the radiating surface 11a is a convex spherical surface that is approximately circular when viewed from above, but it can also be a convex curved surface that is elliptical, oblong, rectangular with rounded corners, square with rounded corners, etc. when viewed from above.

[0082] It should be noted that the above embodiments are merely preferred examples and are not intended to limit the invention, its application objects, or its scope of use.

[0083] - Symbol Explanation -

[0084] 1 Operator

[0085] 2. Treatment site

[0086] 3. Patient Information

[0087] 4. Control Department

[0088] 5. Transmission Condition Control Department

[0089] 6. Treatment Plan Control Department

[0090] 7. Sending Department

[0091] 8 monitors

[0092] 10. Ultrasonic transducer

[0093] 11 Oscillator Main Body

[0094] 11a Radiation surface

[0095] 12, 12', 12” oscillator cover

[0096] 13 Oscillator Housing

[0097] 14. Vibrator Cable

[0098] 20. Ultrasonic therapy device.

Claims

1. An ultrasonic transducer, characterized in that, It includes the oscillator body and the oscillator cover. The radiating surface of the oscillator body is curved, and the oscillator body generates ultrasonic waves. The oscillator cover is made of resin and covers the radiating surface of the oscillator body, serving as an acoustic matching layer. The oscillator cover has a shape that extends along the radial surface of the convex spherical surface of the oscillator body. When the wavelength of the material of the oscillator cover is λ, The thickness of the vibrator cover is constant. The thickness of the vibrator cover is greater than λ / 8 and less than 3λ, excluding the ranges of λ / 8±λ / 40, λ / 4±λ / 40, and λ / 2±λ / 40 where the irradiation energy changes drastically.

2. The ultrasonic transducer according to claim 1, characterized in that, When the thickness of the vibrator cover is less than 0.4 mm, or when the withstand voltage of the vibrator cover is less than 1500 V, an insulating layer is provided on the vibrator cover.

3. The ultrasonic transducer according to claim 1, characterized in that, The radius of the spherical surface of the oscillator body is more than 10 mm and less than 30 mm, and the opening diameter of the spherical surface of the oscillator body is more than 10 mm and less than 50 mm.

4. The ultrasonic transducer according to claim 1, characterized in that, An oscillator housing covering the oscillator body is provided on the back side of the oscillator cover. A backing made of air, oil, or solid is provided on the back side of the oscillator body.

5. The ultrasonic transducer according to claim 4, characterized in that, The vibrator cover and the vibrator housing are integrally formed.

6. The ultrasonic transducer according to claim 1, characterized in that, The vibrator cover is formed of a material with an elastic modulus of 2000 MPa or more and 10000 MPa or less, and an inherent acoustic impedance of 1.5 MPa·s / m or more and 10 MPa·s / m or less.

7. An ultrasonic therapy device, characterized in that, It has an ultrasonic transducer according to any one of claims 1 to 6, and a system for supplying energy to the ultrasonic transducer for ultrasonic vibration.

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