Metamaterial energized phased array transducer and method for three-dimensionally regulating and controlling focus

Abstract

The invention provides a metamaterial energized phased array transducer and a method for three-dimensionally regulating and controlling a focus, the transducer comprises a phased array for outputting ultrasonic waves, a rotatable metamaterial acoustic lens is arranged at the ultrasonic wave output end of the phased array, the metamaterial acoustic lens comprises a plurality of dielectric layers, and the dielectric layers are arranged on the phased array. The ultrasonic focus sound pressure of the transducer is improved by focusing ultrasonic waves through the metamaterial acoustic lens, and when the ultrasonic focus of the transducer deflects, the focus position of the metamaterial acoustic lens moves along with the ultrasonic focus of the transducer through rotation of the metamaterial acoustic lens. According to the invention, the improvement of the focus sound pressure can be realized without increasing the side lobe sound pressure when the sound focus deflects.

Description

TECHNICAL FIELD

[0001] The present application relates to, in particular, a metamaterial powered phased array transducer and a method for three-dimensional control of focal points. BACKGROUND

[0002] Acoustic focusing is a technology that focuses acoustic energy in a local space to form a high acoustic energy density area. Common acoustic focusing methods include acoustic lens focusing, spherical self-focusing, and phased array focusing. Spherical self-focusing and traditional acoustic lens focusing are similar to the principles of concave mirror focusing and convex lens focusing in optics. Once shaped, the focal point position is fixed and cannot be changed, and the focal point position can only be changed by moving mechanical devices or replacing acoustic lenses. Existing phased array focusing transducers mostly use piston sound sources. When the size of the transducer is large, the acoustic energy is relatively dispersed, so the focal point acoustic energy is insufficient, and when the focal point is deflected, large sidelobes appear around the main lobe. These sidelobes will form pseudo focal points, reducing the accuracy of treatment, and long-term use may even cause damage in non-target areas.

[0003] The present application provides a solution to the above problems. SUMMARY

[0004] The present application provides a metamaterial powered phased array transducer and a method for three-dimensional control of focal points, which can improve the focal point acoustic pressure without increasing the sidelobe acoustic pressure when the acoustic focal point is deflected.

[0005] The present application adopts the following technical solutions.

[0006] A metamaterial powered phased array transducer, the transducer comprising a phased array for outputting ultrasonic waves, a rotatable metamaterial acoustic lens being provided at the ultrasonic wave output end of the phased array, the metamaterial acoustic lens comprising a plurality of dielectric layers, the metamaterial acoustic lens improving the ultrasonic wave focal point acoustic pressure of the transducer through focusing of ultrasonic waves, when the ultrasonic wave focal point of the transducer is deflected, the focal point position of the metamaterial acoustic lens is moved to follow the ultrasonic wave focal point of the transducer through rotation of the metamaterial acoustic lens, thereby improving the focal point acoustic pressure without increasing the sidelobe acoustic pressure when the acoustic focal point is deflected.

[0007] The phased array is a piezoelectric ceramic phased array, comprising piezoelectric ceramic pieces arranged in a predetermined manner, all transmitting units of the piezoelectric ceramic phased array transmitting ultrasonic waves at the same frequency to ensure the accuracy of beam synthesis.

[0008] The metamaterial acoustic lens comprises a silicone rubber dielectric layer and a polystyrene dielectric layer arranged above and below as phase control media.

[0009] The silicone rubber dielectric layer is a silicone rubber lens (1), and the polystyrene dielectric layer is a polystyrene lens (2).

[0010] The silicon rubber lens and the polystyrene lens are both eccentric Fresnel lenses.

[0011] The silicon rubber lens and the polystyrene lens are placed above the base of the phased array,

[0012] The metamaterial acoustic lens is assembled and connected with the sealing cover structure, the height of the lower sealing cover of the sealing cover structure is greater than the height of the acoustic lens, the top of the sealing cover structure is provided with a positioning groove for mounting the silicon rubber lens, and the positioning groove is tightly combined with the silicon rubber lens; the bottom of the sealing cover structure is provided with a positioning groove for mounting the transducer, and the transducer is tightly combined with the acoustic lens.

[0013] The sealing cover seals the metamaterial acoustic lens to reduce the temperature of the contact surface during long-term use, and water is injected into the cavity gap in the sealing cover to form a water layer at the positions of the silicon rubber lens and the polystyrene lens, and the water layer serves as a background environmental medium.

[0014] The material of the sealing shell structure is nylon material, and the sealing shell structure is marked with scale lines from 0° to 360°.

[0015] The method for three-dimensional regulation and control of the focal point of the metamaterial-enabled phased array transducer, using the metamaterial-enabled phased array transducer described above, combines metamaterials and ultrasonic phased arrays to achieve flexible and accurate positioning of the focal point in three-dimensional space with low system complexity. Specifically, during the use of the transducer, the polystyrene lens is fixed and the rotation angle of the silicon rubber lens is adjusted to change the total phase gradient of the silicon rubber lens and the polystyrene lens, thereby changing the position of the focal point in the horizontal plane. By independently connecting each phased array element to a driving circuit and adjusting the delay phase of the phased array elements, the focal point depth is continuously adjustable. At the same time, by adjusting the phase of the silicon rubber lens and the polystyrene lens, phase superposition is generated at the focal point position of the metamaterial acoustic lens, and the focal point sound energy is improved through the interference effect of sound waves to achieve ultrasonic focusing, thereby converging sound energy in front of the transducer and generating a focal point in front of the transducer.

[0016] When controlling the lateral deviation of the focal point of the silicon rubber lens and the polystyrene lens in the horizontal plane of the Euclidean coordinate system, the method used is as follows:

[0017] Two eccentric Fresnel lens phase profiles are designed in the Euclidean coordinate system, and the formula is as follows:

[0018] Formula 1: Φ1 = -a[(x-b) 2 +y 2 ]

[0019] Formula 2: Φ2 = a[(x+b) 2 +y 2 ]

[0020] where a and b are constants;

[0021] The phase value Φ of different positions is calculated by formula 1 and formula 2, and the filled material medium height is calculated by formula 3, and each position has a corresponding medium filling height h;

[0022] Formula 3 Where f is the frequency of the ultrasonic transducer, c0 is the sound speed of the background environment medium, c is the sound speed of the lens filling medium, and h is the height of the filling medium; The filling medium height corresponding to the transverse plane is determined by combining formula 1, formula 2 and formula 3;

[0023] Suppose lens 1 rotates And lens 2 rotates The rotation matrix is represented as

[0024]

[0025] Apply this rotation to the coordinates (x, y) to get the rotated coordinates (x', y')

[0026]

[0027] The phase curve of the rotated lens

[0028]

[0029] The total phase shift φ of the ultrasonic wave passing through the two rotated lenses total is:

[0030] Formula 4: The total phase distribution presents a form of gradient phase;

[0031] During the use of the transducer, change the clockwise rotation angle of the lens around the z axis And Adjust the gradient phase of the lens to control the shift of the focal point in the transverse plane, and conversely, the rotation angle of the lens can be calculated according to the position of the pre-focus point in the transverse plane;

[0032] Based on the principle of phased array focusing, the phase delay Φ of each phased array transmitting unit of the transducer i，j satisfies:

[0033] Formula 5:

[0034] Where (x i,j , y i,j ) is the center coordinate of the phased array element, z f is the target focusing depth, and λ is the wavelength.

[0035] In the Euclidean coordinate system, the silicon rubber lens and the polystyrene lens are prepared by 3D printing, the super surface is divided into multiple annular regions after the eccentricity b of the silicon rubber lens and the polystyrene lens is determined and the super surface is divided according to a predetermined radius distance (such as one fourth of the radius of the transducer), and the x and y values of the annular region at the average value of the radii of two adjacent annular regions are selected as the x and y values of the annular region,

[0036] The x and y values of each annular region are different, the rotation angle of the lens is changed according to formula 4 after the focal point position is set, the phase difference is generated after the phases of the two lenses are superimposed, and the ultrasonic wave emitted by the phased array forms an ultrasonic focusing region at the focal point.

[0037] The application aims at the problem of ultrasonic focusing, and designs a sound lens phased array transducer with a composite structure. The transducer is composed of a metamaterial sound lens with two dielectric layers and a piezoelectric ceramic phased array, and is an equipment for realizing ultrasonic focusing. The new transducer is improved on the basis of the traditional ordinary ultrasonic phased array transducer, and the metamaterial sound lens is attached to the phased array transducer to improve the sound pressure at the sound focus. Meanwhile, since the metamaterial sound lens can be rotated, when the focus of the ultrasonic phased array transducer is deflected, the position of the focus can be changed by rotating the metamaterial sound lens, so that the sound pressure at the focus is improved without increasing the side lobe sound pressure when the sound focus is deflected.

[0038] The application combines metamaterials and ultrasonic phased arrays to realize flexible and accurate positioning of the focus in three-dimensional space with low system complexity, and solves the problems of fixed focus position of ultrasonic focusing or only relying on mechanical devices to change the focus position, insufficient focus sound energy, and large side lobe sound pressure around the main lobe when the focus is deflected.

[0039] Compared with the traditional technical method without attaching the metamaterial lens, the application can generate higher sound energy at the focus, and by combining the metamaterial lens with the phased array, when the focus of the ultrasonic phased array transducer is deflected, the position of the focus can be changed by rotating the metamaterial sound lens, so that the sound pressure at the focus is improved without increasing the side lobe sound pressure when the sound focus is deflected. A water layer is arranged above the silicon rubber lens, below the polystyrene lens and between the two lenses to reduce the problem of heating of the contact surface during long-term use.

[0040] The application has the advantages of effectively improving the sound energy at the focus position, controlling the position change of the focus by changing the rotation angle of the lens, effectively improving the main lobe sound pressure and reducing the side lobe sound pressure when the sound focus is deflected in space, and the structure of the metamaterial lens is small, light and easy to install. The application is suitable for high intensity focused ultrasound (HIFU) treatment, acoustic particle manipulation and ultrasonic physiotherapy. BRIEF DESCRIPTION OF DRAWINGS

[0041] The application will be described in further detail below in connection with the accompanying drawings and detailed description:

[0042] Figure 1 is a schematic diagram of a metamaterial-enabled phased array transducer (without a sealing cover); Figure 1 Figure 2 is a schematic diagram of a metamaterial-enabled phased array transducer structure (with a sealing cover);

[0043] Figure 3 is a schematic diagram of a metamaterial-enabled phased array transducer (top view); Figure 2 Figure 4 is a schematic diagram of a metamaterial-enabled phased array transducer structure (with a sealing cover);

[0044] Figure 5 is a schematic diagram of a metamaterial-enabled phased array transducer (A-A cross-sectional view when the focal point transverse plane is (0, 0) (without a sealing cover)); Figure 3 Figure 6 is a schematic diagram of a metamaterial-enabled phased array transducer (A-A cross-sectional view when the focal point transverse plane is (0, 0) (with a sealing cover));

[0045] Figure 4 Figure 7 is a schematic diagram of an upper sealing cover structure for a metamaterial lens;

[0046] Figure 8 is a schematic diagram of a lower sealing cover structure for a metamaterial lens; Figure 5 Figure 9 is a schematic diagram of a substrate structure for placing a transducer array;

[0047] Figure 6 Figure 10 is a comparison diagram of the influence of the presence or absence of a lens on the acoustic energy at the focal point (in the figure, (a) focal point transverse plane (0, 0) (b) focal point transverse plane (10, -10));

[0048] Figure 11 is a schematic diagram of a metamaterial-enabled phased array transducer (without a sealing cover); Figure 7 Figure 12 is a schematic diagram of a metamaterial-enabled phased array transducer structure (with a sealing cover);

[0049] Figure 8 Figure 13 is a schematic diagram of a metamaterial-enabled phased array transducer (top view);

[0050] Figure 14 is a schematic diagram of a metamaterial-enabled phased array transducer (A-A cross-sectional view when the focal point transverse plane is (0, 0) (without a sealing cover)); Figure 9 Figure 15 is a schematic diagram of a metamaterial-enabled phased array transducer (A-A cross-sectional view when the focal point transverse plane is (0, 0) (with a sealing cover));

[0051] Figure 16 is a schematic diagram of a metamaterial-enabled phased array transducer (without a sealing cover);

[0052] ​​​​As shown in the figure, a metamaterial-enabled phased array transducer, the transducer comprising a phased array 3 for outputting ultrasonic waves, a rotatable metamaterial acoustic lens is arranged at the ultrasonic wave output end of the phased array, the metamaterial acoustic lens comprises a plurality of dielectric layers, the metamaterial acoustic lens improves the ultrasonic focal point sound pressure of the transducer through focusing of the ultrasonic waves, when the ultrasonic focal point of the transducer is deflected, the focal point position of the metamaterial acoustic lens is made to follow the movement of the ultrasonic focal point of the transducer through rotation of the metamaterial acoustic lens, so as to realize improvement of the focal point sound pressure without increasing the sidelobe sound pressure when the acoustic focal point is deflected.

[0053] The phased array is a piezoelectric ceramic phased array, comprising piezoelectric ceramic pieces arranged in a preset manner, all transmitting units of the piezoelectric ceramic phased array transmit ultrasonic waves at the same frequency to ensure the accuracy of beam synthesis.

[0054] The metamaterial acoustic lens comprises a silicone rubber dielectric layer and a polystyrene dielectric layer arranged above and below as phase control media.

[0055] The silicone rubber dielectric layer is a silicone rubber lens 1, and the polystyrene dielectric layer is a polystyrene lens 2.

[0056] The silicone rubber lens and the polystyrene lens are both eccentric Fresnel lenses.

[0057] The silicone rubber lens and the polystyrene lens are placed above the base 6 on which the phased array is placed,

[0058] The metamaterial acoustic lens is assembled and connected with the sealing cover structure, the height of the lower sealing cover 5 of the sealing cover structure is greater than the height of the acoustic lens, the top of the sealing cover structure is provided with a positioning groove for mounting the upper sealing cover 4 of the silicone rubber lens, the positioning groove is tightly fitted with the silicone rubber lens; the bottom of the sealing cover structure is provided with a positioning groove for mounting the transducer, and the transducer is tightly fitted with the acoustic lens;

[0059] The sealing cover seals the metamaterial acoustic lens to reduce the temperature of the contact surface during long-term use, and water is injected into the cavity gap in the sealing cover to form a water layer 7 at the silicone rubber lens and the polystyrene lens, and the water layer serves as a background environmental medium.

[0060] The material of the sealing shell structure is nylon material, and the sealing shell structure is marked with scale lines from 0° to 360°.

[0061] The method for three-dimensional regulation of focal points of metamaterial-enabled phased array transducers uses the metamaterial-enabled phased array transducers described above, and the metamaterial-enabled phased array transducers combine metamaterials and ultrasonic phased arrays to achieve flexible and accurate positioning of focal points in three-dimensional space with low system complexity. Specifically, during the use of the transducer, the polystyrene lens is fixed and not moved, the rotation angle of the silicone rubber lens is adjusted, the total phase gradient of the silicone rubber lens and the polystyrene lens is changed, and then the position of the focal point in the horizontal plane is changed. Each phased array element is independently connected to a driving circuit, the delay phase of the phased array element is adjusted, the focal point depth is continuously adjustable, and the phase of the silicone rubber lens and the polystyrene lens is adjusted to produce phase superposition at the focal point position of the metamaterial acoustic lens. The interference effect of sound waves is used to improve the focal point acoustic energy and achieve ultrasonic focusing, so that the sound energy is concentrated in front of the transducer, and a focal point is generated in front of the transducer.

[0062] When controlling the lateral deviation of the focal point of the silicone rubber lens and the polystyrene lens in the horizontal plane of the Euclidean coordinate system, the method used is as follows:

[0063] Two eccentric Fresnel lens phase profiles are designed in the Euclidean coordinate system, and the formula is as follows:

[0064] Formula 1: Phi1 = -a[(x-b) 2 +y 2 ]

[0065] Formula 2: Phi2 = a[(x+b) 2 +y 2 ]

[0066] where a and b are constants;

[0067] The phase values Phi at different positions are calculated by formula 1 and formula 2, and the filled material medium height is calculated by formula 3. Each position has a corresponding medium filling height h.

[0068] Formula 3 where f is the frequency of the ultrasonic transducer, c0 is the sound speed of the background environment medium, c is the sound speed of the lens filling medium, and h is the height of the filling medium. The filling medium height corresponding to the horizontal plane is determined by combining formula 1, formula 2, and formula 3.

[0069] Let lens 1 rotate and lens 2 rotate The rotation matrix is represented as

[0070]

[0071] Apply this rotation to the coordinates (x, y) to get the rotated coordinates (x', y')

[0072]

[0073] Rotated lens phase curve

[0074]

[0075] Phase shift sum φ of ultrasonic wave through the two rotated lenses total is:

[0076] Formula 4: The total phase distribution presents the form of gradient phase;

[0077] During the use of the transducer, the lens is rotated clockwise around the z-axis by an angle and Adjust the gradient phase of the lens to control the deflection of the focal point in the transverse plane, and conversely, the rotation angle of the lens can be calculated according to the position of the pre-focus transverse plane;

[0078] Based on the principle of phased array focusing, the phase delay Φ of each phased array element of the transducer i，j satisfies:

[0079] Formula 5:

[0080] Where (x i,j , y i,j ) is the center coordinate of the phased array element, z f is the target focusing depth, and λ is the wavelength.

[0081] In the Euclidean coordinate system, the silicone lens and the polystyrene lens are prepared by 3D printing, and after the eccentricity b of the silicone lens and the polystyrene lens is determined, the metasurface is divided into multiple annular regions according to the predetermined radius distance (such as one fourth of the transducer radius), and the x, y values of the annular region at the average value of the radii of two adjacent annular regions are selected as the x, y values of the annular region,

[0082] The x, y values of each annular region are different, after the focal point position is set, the lens rotation angle is changed according to formula 4, the phase difference is generated after the phase superposition of the two lenses, and the ultrasonic focusing region is formed at the focal point by combining the phased array emission.

[0083] Embodiment:

[0084] The example proposes a composite structure acoustic lens phased array transducer, which is composed of two medium layer metamaterial acoustic lenses and a piezoelectric ceramic phased array, and is an ultrasonic focusing device. The new transducer is improved on the basis of the traditional ordinary ultrasonic phased array transducer, and the metamaterial acoustic lens is attached to the phased array transducer to improve the sound pressure of the acoustic focus; at the same time, since the metamaterial acoustic lens can be rotated, when the focus of the ultrasonic phased array transducer is deflected, the focus position can be changed by rotating the metamaterial acoustic lens, so that the sound pressure of the focus is improved without increasing the side lobe sound pressure when the acoustic focus is deflected.

[0085] In the example, the ultrasonic transducer frequency refers to the natural resonance frequency of the transducer (the core is piezoelectric material) under the excitation of an electrical signal. The ultrasonic wave frequency refers to the mechanical wave frequency radiated into the medium (such as air, water, human tissue) when the transducer vibrates, which is a physical property of the ultrasonic wave, and its size is directly determined by the vibration frequency of the "vibration source (transducer)". In the phased array ultrasonic transducer, all transducers work at the same frequency to ensure the accuracy of beam synthesis. In the normal working state of the ultrasonic transducer without failure, overdrive / drive reduction, the output ultrasonic wave frequency will strictly match the inherent frequency, that is, the ultrasonic transducer frequency is equal to the ultrasonic wave frequency. In practical application, there is only a small deviation, which can be ignored.

[0086] Formula 3

[0087] Where f is the ultrasonic transducer frequency (i.e. ultrasonic wave frequency), c0 is the sound speed of the background environment medium, c is the sound speed of the lens filling medium, and h is the height of the filling medium.

[0088] In the example, the designed metamaterial acoustic lens can change the position of the focus in the transverse plane by controlling the rotation angle of the lens. The metamaterial lens is attached to the ultrasonic physiotherapy transducer, and when the focus of the ultrasonic phased array transducer is deflected, the focus position can be changed by rotating the metamaterial acoustic lens, so that the sound pressure of the focus is improved without increasing the side lobe sound pressure when the acoustic focus is deflected. A water layer is provided in the metamaterial lens to reduce the heating problem of the contact surface of the ultrasonic treatment device during long-term use; the metamaterial lens structure is small, light and easy to install.

[0089] In this example, the sealing shell is made of nylon material as the base, and the sealing shell is marked with 0° to 360° scale lines. Two lens metasurfaces are made of silicone rubber and polystyrene as phase control media. Since the metasurface profile is a decentered Fresnel lens, after determining the decentering distance b, the metasurface is partitioned into multiple annular regions according to a certain radius distance (such as one fourth of the transducer radius). The x, y values of the annular region at the average value of the radii of two adjacent annular regions are selected as the x, y values of the annular region. Since the x, y values of each annular region are different, after setting the focal point position, the lens rotation angle is changed according to formula 4, and the phase difference is generated after the phase superposition of the two lenses. The focused sound wave is formed at the focal point by combining the phased array emission, Figure 3 The white annular region in the above figure is the divided annular region. The height of each annular region is calculated according to the phase profile of the two decentered Fresnel lenses designed above, and 3D printing technology is used to print the height. The printed silicone rubber lens is matched with the upper sealing cover, and the polystyrene lens is matched with the lower sealing cover. The sealing cover is sealed to reduce the temperature of the contact surface during long-term use, and water is injected into the gap as the background medium to form a water layer. The transducer array is installed in the base for placing the transducer array.

[0090] The prepared metamaterial lens is attached to the top of the base for placing the transducer array. After focusing through the artificial acoustic structure lens, the target depth is treated with ultrasound. After the metamaterial lens is assembled with the sealing cover, the height of the lower sealing cover is greater than that of the acoustic lens. At this time, the top positioning groove is used to install the silicone rubber lens, which is tightly attached to the silicone rubber lens; the bottom also has a positioning groove for installing the transducer, which is tightly attached to the acoustic lens. During use, the polystyrene lens can be fixed without moving, and the rotation angle of the silicone rubber lens can be adjusted to change the total phase gradient of the two lenses and change the position of the focal point in the horizontal plane. By connecting each phased array element to a separate driving circuit, the delay phase of the phased array element is adjusted to achieve continuous adjustment of the focal point depth.

Claims

1. A metamaterial-enabled phased array transducer, characterized by: The transducer comprises a phased array for outputting ultrasonic waves, and a rotatable metamaterial acoustic lens is arranged at an ultrasonic wave output end of the phased array, the metamaterial acoustic lens comprises a plurality of dielectric layers, and the metamaterial acoustic lens improves the ultrasonic focal point sound pressure of the transducer through focusing of the ultrasonic waves; when the ultrasonic focal point of the transducer is deflected, the focal point position of the metamaterial acoustic lens is caused to move along with the ultrasonic focal point of the transducer through rotation of the metamaterial acoustic lens.

2. A metamaterial-enabled phased array transducer according to claim 1, characterized in that: The phased array is a piezoelectric ceramic phased array, which comprises piezoelectric ceramic pieces arranged in a preset manner, and all the transmitting units of the piezoelectric ceramic phased array transmit ultrasonic waves at the same frequency to ensure the accuracy of beam synthesis.

3. A metamaterial-enabled phased array transducer according to claim 1, wherein: The metamaterial acoustic lens comprises a silicone rubber dielectric layer and a polystyrene dielectric layer arranged in a vertical manner as phase control media.

4. A metamaterial-enabled phased array transducer according to claim 3, wherein: The silicone rubber dielectric layer is a silicone rubber lens (1), and the polystyrene dielectric layer is a polystyrene lens (2).

5. A metamaterial-enabled phased array transducer according to claim 4, wherein: The silicone rubber lens and the polystyrene lens are both eccentric Fresnel lenses.

6. A metamaterial-enabled phased array transducer according to claim 5, wherein: The silicone rubber lens and the polystyrene lens are arranged above a base body on which the phased array is arranged, The metamaterial acoustic lens is assembled and connected with a sealing cover structure, the height of a lower sealing cover of the sealing cover structure is greater than the height of the acoustic lens, the top of the sealing cover structure is provided with a positioning groove for mounting the silicone rubber lens, and the positioning groove is tightly combined with the silicone rubber lens; the bottom of the sealing cover structure is provided with a positioning groove for mounting the transducer, and the transducer is tightly combined with the acoustic lens; The sealing cover seals the metamaterial acoustic lens to reduce the temperature of the contact surface during long-time use, and water is injected into the gap in the inner cavity of the sealing cover to form a water layer at the silicone rubber lens and the polystyrene lens, and the water layer serves as a background environment medium.

7. A metamaterial-enabled phased array transducer according to claim 5, wherein: The material of the sealing shell structure is nylon material, and the sealing shell structure is marked with scale lines from 0° to 360°.

8. A method for three-dimensionally controlling the focal point of a metamaterial-energized phased array transducer, using the metamaterial-energized phased array transducer as described in claim 4, characterized in that: The metamaterial-enabled phased array transducer combines metamaterials and ultrasonic phased arrays to achieve flexible and accurate positioning of the focal point in three-dimensional space. Specifically, during the use of the transducer, the phase gradient sum of the silicone rubber lens and the polystyrene lens is changed to change the position of the focal point in the horizontal plane. By independently connecting each phased array element to a driving circuit and adjusting the delay phase of the phased array element, the focal point depth is continuously adjustable. At the same time, by adjusting the phase of the silicone rubber lens and the polystyrene lens, a phase superposition is generated at the focal point position of the metamaterial acoustic lens, and the focal point sound energy is improved through the interference effect of sound waves to achieve ultrasonic focusing, thereby converging sound energy in front of the transducer and generating a focal point in front of the transducer.

9. The method of claim 8, wherein the metamaterial-enabled phased array transducer three-dimensional steered focal point is characterized by: When controlling the lateral shift of the focal point of the silicone rubber lens and the polystyrene lens in the horizontal plane of the Euclidean coordinate system, the method used is as follows: Two eccentric Fresnel lens phase profiles are designed in the Euclidean coordinate system, and the formula is as follows: Formula 1: Φ1 = -a[(x-b) 2 +y 2 ] Formula 2: Φ2 = a[(x + b) 2 + y 2 ] wherein a and b are constants; The phase values Φ at different positions are calculated by formula 1 and formula 2, and the height h of the filled material medium is calculated by formula 3, and each position has a corresponding medium filling height h. Wherein f is the frequency of the ultrasonic transducer, c0 is the sound speed of the background environment medium, c is the sound speed of the lens filling medium, h is the height of the filling medium; The filling medium height corresponding to the transverse plane is determined by combining formula 1, formula 2 and formula 3; Let lens 1 rotate and lens 2 rotate The rotation matrix is then given by Apply this rotation to the coordinates (x,y) to get the rotated coordinates (x',y') Rotated lens phase curve The total phase shift φ of the ultrasound waves through the two lenses after rotation total is: The total phase distribution presents the form of gradient phase; During the use of the transducer, the rotation angle of the lens around the z axis is changed clockwise and The gradient phase of the lens is adjusted, and the deflection of the focal point in the transverse plane is controlled. The rotation angle of the lens can also be calculated according to the pre-focal transverse plane position. Based on the principle of phased array focusing, the phase delay Φ of the transmitting units of each phased array of the transducer i，j satisfies: where (x i,j ,y i,j ) are the coordinates of the phase array element center, z f is the target focusing depth, and λ is the wavelength.

10. The method of claim 9, wherein the metamaterial-enabled phased array transducer three-dimensional steered focal point is characterized by: In the Euclidean coordinate system, the silicone lens and the polystyrene lens are prepared by 3D printing, the metasurface is divided into multiple annular regions according to the predetermined radius distance after the eccentricity b of the silicone lens and the polystyrene lens is determined, the x and y values of the annular region at the average value of the radii of the two adjacent annular regions are selected as the x and y values of the annular region, The x and y values of each annular region are different, after the focal point position is set, the phase difference is generated after the phase of the two lenses is superimposed by changing the rotation angle of the lens according to formula 4, and the ultrasonic focusing region is formed at the focal point by the ultrasonic wave emitted by the phased array.

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