ULTRASONIC TRANSDUCER AND MANUFACTURING METHOD THEREFOR

Abstract

Provided is an ultrasonic transducer and a preparation method thereof. The ultrasonic transducer includes a housing. A piezoelectric layer is disposed in the housing and includes at least two piezoelectric array elements. A frequency interval between the piezoelectric array elements is 50 kHz to 1.2 MHz. An acoustic lens is disposed at a front end of the piezoelectric layer and is used for ensuring that the piezoelectric array elements having different frequencies have a common focus.

Claims

1. An ultrasonic transducer, comprising a housing, wherein a piezoelectric layer is disposed in the housing and comprises at least two piezoelectric array elements having different frequencies, and a frequency interval between the piezoelectric array elements is 50 kHz to 1.2 MHz.

2. The ultrasonic transducer of claim 1, wherein the piezoelectric layer comprises a low-frequency piezoelectric array element and a high-frequency piezoelectric array element, and the frequency interval between the low-frequency piezoelectric array element and the high-frequency piezoelectric array element is 50 kHz to 1.2 MHz.

3. The ultrasonic transducer of claim 1, wherein the piezoelectric layer comprises a low-frequency piezoelectric array element, an intermediate-frequency piezoelectric array element and a high-frequency piezoelectric array element, and the frequency interval among the low-frequency piezoelectric array element, the intermediate-frequency piezoelectric array element and the high-frequency piezoelectric array element is 50 kHz to 1.2 MHz.

4. The ultrasonic transducer of claim 1, wherein the piezoelectric array elements are planar or concave.

5. The ultrasonic transducer of claim 1, wherein the piezoelectric array elements are arranged symmetrically with respect to a circular center axis or arranged in a linear array.

6. The ultrasonic transducer of claim 1, wherein an axial cross section of the piezoelectric layer is circular, triangular or square.

7. The ultrasonic transducer of claim 1, wherein at least one matching layer is disposed on a front end of the piezoelectric layer, and an acoustic lens is disposed on a front end of the matching layer and is used for ensuring that the piezoelectric array elements having different frequencies have a common focus.

8. The ultrasonic transducer of claim 1, wherein a backing layer is disposed on a back end of the piezoelectric layer; and electrodes on upper and lower surfaces of each of the piezoelectric elements of the piezoelectric layer are respectively connected to a positive electrode and a negative electrode of a cable.

9. An ultrasonic transducer preparation method, comprising: step S1: bonding side surfaces of at least two piezoelectric array elements to form a piezoelectric layer; step S2: depositing electrodes on upper and lower surfaces of each of the piezoelectric array elements, and connecting the electrodes to a positive electrode and a negative electrode of a cable; step S3: fixing the piezoelectric layer connected to the cable to an inner side of a housing, and depositing a backing material on a lower surface of the piezoelectric layer to form a backing layer fixed to the inner side of the housing; step S4: depositing a matching material on an upper surface of the piezoelectric layer to form a matching layer fixed to the inner side of the housing; and step S5: forming a layer of acoustic lens over an upper surface of the matching layer, wherein the acoustic lens is used for ensuring that the piezoelectric array elements having different frequencies have a common focus, propagation time of a sound wave of each of the piezoelectric array elements is calculated through a radius of curvature and a speed of sound of the layer of acoustic lens, and excitation time of the each of the piezoelectric array elements is adjusted to overlap focuses of the piezoelectric array elements.

10. The ultrasonic transducer preparation method of claim 9, wherein in the step S2, the electrodes are deposited on the upper and lower surfaces of each of the piezoelectric array elements to form an array element positive electrode and an array element negative electrode, wherein the array element positive electrode is connected to the positive electrode of the cable; the array element negative electrode is connected to the negative electrode of the cable, or the array element negative electrode is connected to a metal housing via a conductive material and the metal housing is connected to the negative electrode of the cable.

11. The ultrasonic transducer preparation method of claim 10, wherein the backing material is epoxide resin with filler, and the matching material is the epoxide resin with the filler

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] For a better understanding of the present disclosure, reference may be made to the following drawings for illustrating the related art or the embodiments. The drawings will briefly show a part of products or methods involved in the embodiments or in the related art. The basic information of the drawings is as follows.

[0033] FIG. 1 is a schematic diagram of an ultrasonic transducer according to an embodiment;

[0034] FIG. 2 is a cross-sectional view of an ultrasonic transducer according to an embodiment;

[0035] FIG. 3 is an exploded view of an ultrasonic transducer according to an embodiment;

[0036] FIG. 4 is an arrangement diagram of piezoelectric array elements having two frequencies according to an embodiment; and

[0037] FIG. 5 is an arrangement diagram of piezoelectric array elements having three frequencies according to an embodiment.

[0038] 1Matching layer, 2Acoustic lens, 3Piezoelectric layer, 31Low-frequency piezoelectric array element, 32High-frequency piezoelectric array element, 33Intermediate-frequency piezoelectric array element, 4Backing layer, 5Housing, 6Cable.

DETAILED DESCRIPTION

[0039] The present disclosure will be further described. It is obvious that the described embodiments are only part, not all, of embodiments of the present disclosure.

[0040] As shown in FIG. 1 to FIG. 3, the present example provides an ultrasonic transducer including a housing 5. A piezoelectric layer 3 is disposed in the housing 5 and includes at least two piezoelectric array elements having different frequencies, and a frequency interval between the piezoelectric array elements is 50 kHz to 1.2 MHz. In another embodiment, the frequency interval between the piezoelectric array elements may be 50 kHz to 1 MHz; and the frequency interval between the piezoelectric array elements may further be 50 kHz to 0.8 MHz. The piezoelectric array elements are concave. In another embodiment, the piezoelectric array elements may be planar. Compared with the concave wafer nesting structure in the related art, in the embodiment, the combination of planar piezoelectric array elements having two or more different frequencies and the use of focusing acoustic lens can more easily ensure the common focus and reduce the preparation difficulty of the ultrasonic transducer. The piezoelectric array elements are arranged symmetrically with respect to a circular center axis. In another embodiment, the piezoelectric array elements may be arranged in a linear array. An axial cross section of the piezoelectric layer 3 is circular. In another embodiment, the axial cross section of the piezoelectric layer 3 may be triangular or square. Correspondingly, the housing 5 may be configured to be circular, triangular or square.

[0041] Specifically, the ultrasonic transducer includes the housing 5. The piezoelectric layer 3 is disposed in the housing 5. The piezoelectric layer includes a low-frequency piezoelectric array element 31 and a high-frequency piezoelectric array element 32. The frequency interval between the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 is 50 kHz to 1.2 MHz. An acoustic lens 2 is disposed on the piezoelectric layer 3 and is used for ensuring that the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 have a common focus. In an embodiment, the focal length is 5 cm to 10 cm. In the embodiment, the frequency of each of the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 is 0.5 MHz to 2 MHz.

[0042] In the embodiment, at least one matching layer 1 is disposed on a front end of the piezoelectric layer 3, and has a main function of improving the sound propagation efficiency of the transducer. One or more matching layers are provided. The acoustic lens 2 is disposed on a front end of the matching layer. A backing layer 4 is disposed on a back end of the piezoelectric layer 3.

[0043] Electrodes on upper and lower surfaces of each of the piezoelectric elements of the piezoelectric layer 3 are respectively connected to a core wire and a ground wire of a cable 6. Each piezoelectric array element of the ultrasonic transducer is led out through a coaxial cable. In an embodiment, the ultrasonic transducer is a dual-frequency transducer, includes a low-frequency piezoelectric array element 31 and a high-frequency piezoelectric array element 32, and therefore has two coaxial cables. The core wire and the negative ground wire of each coaxial cable are connected to upper and lower surfaces of respective one of the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32. Specifically, the positive electrodes of the two cables 6 are connected to the respective positive electrodes of the two piezoelectric array elements, and the negative electrodes of the two cables 6 are connected to the respective negative electrodes of the two piezoelectric array elements.

[0044] Specifically, as shown in FIG. 2 and FIG. 3, a matching layer 1 is disposed on the upper surface of the piezoelectric layer 3. The acoustic lens 2 is disposed over the upper surface of the matching layer 1 and is used for ensuring that the piezoelectric array elements having different frequencies have a common focus. The backing layer 4 is disposed on the lower surface of the piezoelectric layer 3. Electrodes on upper and lower surfaces of each of the piezoelectric elements of the piezoelectric layer 3 are respectively connected to a positive electrode and a negative electrode of the cable 6. One end of the cable 6 is connected to the piezoelectric layer 3, and the other end of the cable 6 passes through the backing layer 4 and extends to the outside of the housing 5.

[0045] In the embodiment, the piezoelectric layer 3 includes the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32. The frequency interval between the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 is 50 kHz to 1.2 MHz. The high frequency and the low frequency are relative, and the difference between the high frequency and the low frequency may be small. As shown in FIG. 4, the ultrasonic transducer is a dual-frequency ultrasonic transducer, includes two semi-circular piezoelectric array elements having different frequencies. The two semi-circular piezoelectric array elements form a circular piezoelectric layer 3. The low-frequency piezoelectric array element 31 has a frequency of 650 kHz, and the high-frequency piezoelectric array element 32 has a frequency of 1 MHz. Two piezoelectric array elements having different frequencies are combined in one plane, and the sound field of the dual-frequency transducer is focused to the same position through the acoustic lens 2, thereby improving the sound field intensity at the focus position.

[0046] In the related art, a technical scheme of stacking up and down piezoelectric elements having different frequencies is often used; while in the embodiment, different piezoelectric wafers are ensured to have the common focus through the combination of multiple piezoelectric wafers having different frequencies and the use of the acoustic lens. In practical applications, the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 may not be arranged in the same plane, and the combination manner of the piezoelectric array elements may be specifically designed according to the design of the acoustic lens.

[0047] In the ultrasonic thrombolysis application, the 650 kHz sinusoidal signal and the 1 MHz sinusoidal signal are respectively used and combined to excite the dual-frequency ultrasonic transducer of the embodiment. As a control group, a single-frequency group uses the 650 kHz sinusoidal signal or the 1 MHz sinusoidal signal to excite a common ultrasonic transducer. The parameters of the dual-frequency group and the single-frequency group are respectively configured, and the parameters such as the action time, the pulse repetition frequency, the duty ratio of the excitation signal, the power are configured to be the same.

[0048] The experimental results show that the dual-frequency stimulation can reduce the cavitation threshold of ultrasound thrombolysis in the application of ultrasound thrombolysis, achieving the thrombolysis efficiency double that of the single-frequency case. In other words, on the premise of the same thrombolysis efficiency, the treatment time of the dual-frequency thrombolysis can be shortened to half of the treatment time of single-frequency thrombolysis. The dual-frequency ultrasonic transducer can increase the sound pressure generated by the common ultrasonic transducer by 30%, which can further reduce the energy for exciting the ultrasonic transducer device. This can reduce the accumulation of heat and reduce the risk of heat build-up for the transcranial ultrasound application. Compared with the related art, in the embodiment, the difference between the high frequency and the low frequency is small, the cavitation effect of the ultrasound can be improved without increasing the power loss of the excitation system, and the thrombolysis effect is good.

[0049] In an embodiment, the piezoelectric layer 3 includes the low-frequency piezoelectric array element 31, an intermediate-frequency piezoelectric array element 33 and the high-frequency piezoelectric array element 32. The frequency interval among the low-frequency piezoelectric array element 31, the intermediate-frequency piezoelectric array element 33 and the high-frequency piezoelectric array element 32 is 50 kHz to 1.2 MHz. The high frequency, the intermediate frequency and the low frequency are relative; and the difference among the high frequency, the intermediate frequency and the low frequency may be small. In the embodiment, the frequency of each of the low-frequency piezoelectric array element 31, the intermediate-frequency piezoelectric array element 33 and the high-frequency piezoelectric array element 32 is 0.5 MHz to 2 MHz. As shown in FIG. 5, the ultrasonic transducer is a triple-frequency ultrasonic transducer, includes three sector-shaped piezoelectric array elements having different frequencies. The three sector-shaped piezoelectric array elements form a circular piezoelectric layer 3, and may be the same or different. In practical applications, the low-frequency piezoelectric array element 31, the intermediate-frequency piezoelectric array element 33 and the high-frequency piezoelectric array element 32 may be disposed in the same plane or not; and the combination manner of the piezoelectric array elements may be specifically designed according to the design of the acoustic lens. The low-frequency piezoelectric array element 31 has a frequency of 1.4 MHz, the intermediate-frequency piezoelectric array element 33 has a frequency of 1.45 MHz, and the high-frequency piezoelectric array element 32 has a frequency of 1.5 MHz. It has been experimentally verified that three frequencies combined in use for excitation can slightly (5%) improve the efficiency compared with dual frequencies in the application of ultrasonic thrombolysis. Compared with the related art, in the embodiment, the difference among the high frequency, the intermediate frequency and the low frequency is small, the cavitation effect of the ultrasound can be improved without increasing the power loss of the excitation system, and the thrombolysis effect is good. In practical applications, the piezoelectric elements are not limited to having two or three different frequencies, and can be set according to actual needs. In the embodiment, piezoelectric array elements having different frequencies are combined to form the ultrasonic transducer having two or more frequencies, and piezoelectric array elements having different frequencies are combined to produce mixed-frequency ultrasound. The dual-frequency or multi-frequency combination transducers can improve the frequency bandwidth of the ultrasonic transducer, reduce the design difficulty of the broadband impedance matching circuit, and facilitate the transmission and reception of ultrasonic signals and post-processing. Two or more piezoelectric array elements having different frequencies are combined in one plane, and the sound field of each of the dual-frequency transducer and the multi-frequency transducer is focused to the same position through the acoustic lens 2, thereby improving the sound field intensity at the focus position.

[0050] The embodiment further provides an ultrasonic transducer preparation method. The method includes steps described below.

[0051] In a step S1, side surfaces of the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 are bonded to form the piezoelectric layer 3. Specifically, the low-frequency piezoelectric array element 31 and the high-frequency piezoelectric array element 32 are bonded via epoxide resin or other bonding materials.

[0052] In a step S2, electrodes are deposited on upper and lower surfaces of each of the piezoelectric array elements, and the electrodes are connected to the positive electrode and the negative electrode of the cable 6.

[0053] Specifically, in the step S2, the electrodes are deposited on the upper and lower surfaces of each of the piezoelectric array elements to form an array element positive electrode and an array element negative electrode. Each array element positive electrode is connected to the positive electrode (core wire) of the cable 6. In the embodiment, the cable 6 is a coaxial cable. Each piezoelectric array element of the ultrasonic transducer is led out through a respective coaxial cable. The negative electrode of the transducer is connected in two manners: each array element negative electrode is connected to the negative electrode (ground wire) of a respective coaxial cable; or each array element negative electrode is connected to the metal housing 5 via a conductive material, and the metal housing 5 is connected to the negative electrode (ground wire) of each coaxial cable. In an embodiment, the conductive material is conductive silver paste.

[0054] In a step S3, the piezoelectric layer 3 connected to the cable 6 is fixed to an inner side of the housing 5, and a backing material is deposited on a lower surface of the piezoelectric layer 3 to form the backing layer 4 fixed to the inner side of the housing 5. In an embodiment, the backing material is epoxide resin with filler.

[0055] In a step S4, a matching material is deposited on an upper surface of the piezoelectric layer 3 to form the matching layer 1 fixed to the inner side of the housing 5. In an embodiment, the matching material is the epoxide resin with the filler.

[0056] In a step S5, a layer of acoustic lens 2 is formed at a front end of the matching layer 1. The acoustic lens is used for ensuring that the piezoelectric array elements having different frequencies have a common focus. The propagation time of a sound wave is calculated through a radius of curvature and a speed of sound of the layer of acoustic lens 2, and excitation time is adjusted to have focuses of the piezoelectric array elements overlapped.

[0057] Specifically, a layer of acoustic lens 2 is formed over an upper surface of the matching layer 1. The acoustic lens is used for ensuring that the piezoelectric array elements having different frequencies have a common focus. The propagation time of a sound wave of each of the piezoelectric array elements is calculated through a radius of curvature and a speed of sound of the layer of acoustic lens 2, and excitation time of the each of the piezoelectric array elements is adjusted to overlap focuses of the piezoelectric array elements. Compared with the focusing through concave wafer nesting in the related art, in the embodiment, the combination of planar piezoelectric array elements having two or more different frequencies and the use of the focusing acoustic lens 2 can reduce the preparation difficulty.