CN107863097B - Method for focusing sound wave based on patterned cutting technology - Google Patents
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/18—Methods or devices for transmitting, conducting or directing sound
- G10K11/26—Sound-focusing or directing, e.g. scanning
- G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses
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Abstract
The invention discloses a method for focusing sound waves based on a patterned cutting technology, which comprises the following steps: determining a phase control film, wherein the phase control film can change the phase of the sound wave transmitted by the phase control film by 180 degrees; and cutting the phase control film to enable the sound wave plane transmitted by the cut phase control film to focus on a focus or to spatially focus on the focus, wherein the wave path difference between the sound wave after passing through the cutting area and the sound wave after passing through the adjacent non-cutting area to reach the focus is half of the wave length of the sound wave by controlling the cutting size. The present invention is based on thin films and specific patterning design rules that can change the transmission phase by 180 degrees to achieve acoustic focusing. The obtained sound focusing point can be used for ultrasonic lithotripsy and the like, and has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of sound waves, and particularly relates to a method for focusing sound waves based on a patterned cutting technology.
Background
The focusing of the sound waves has important significance for ultrasonic imaging, shock wave lithotripsy, sound energy weapons and the like and has great practical value in production and life. In the prior art, as a method for focusing an acoustic wave using a planar device, there are an active phased array method, a passive waveguide cavity stack, and the like. The phase elements at different positions on the plane have different phases, so that the focusing is realized by meeting the relationship of phase length to a focus in the plane of the whole passing device.
The active phased array utilizes current to control the delay phase; while passive waveguide cavities utilize a designed twisted acoustic channel within a finite distance metal waveguide to achieve large phase changes. The two methods respectively utilize the methods of stacking the waveguide cavity and etching the metal plate to regulate and control the sound wave so as to realize sound focusing.
However, the thickness of the devices in the two modes is more than centimeter level, the whole device is very large and heavy, the cost is high, and the application range of the device is limited. And the two methods of stacking phase units have limited precision of specific effects because the unit volume cannot be ignored, and particularly, the sound wave with the wavelength smaller than the unit size is difficult to focus. In addition, the active method requires a power supply and a control system, so that the whole system is bulky and difficult to integrate into a handheld device.
Disclosure of Invention
In view of the above defects or improvement requirements of the prior art, the present invention provides a method and an apparatus for focusing an acoustic wave based on a patterned clipping technique, so as to solve the technical problems of limited focusing precision, large apparatus, high cost, etc. of the existing acoustic wave focusing apparatus.
To achieve the above object, the present invention provides a method for focusing an acoustic wave based on a patterned cropping technique, comprising:
determining a phase control film, wherein the phase control film can change the phase of the sound wave transmitted by the phase control film by 180 degrees; and cutting the phase control film to enable the sound wave plane transmitted by the cut phase control film to focus on a focus or to spatially focus on the focus, wherein the wave path difference between the sound wave after passing through the cutting area and the sound wave after passing through the non-cutting area adjacent to the sound wave after passing through the cutting area to reach the focus is half of the wave length of the sound wave by controlling the cutting size.
Optionally, when the acoustic wave plane transmitted by the cut phase control film is focused on a focal point, cutting the phase control film includes:
cutting the phase control film into strip-shaped structures which are symmetrically distributed, wherein the width l from the nth line of the symmetric center to the symmetric center is equal to the width l of the symmetric centernSatisfies the following conditions:
wherein f iscFor the designed focal length, λ is the acoustic wavelength, and N is the number of bus bars on one side of the bar structure.
Optionally, when the sound wave transmitted by the cut phase control film is focused on a focal point in space, cutting the phase control film includes:
cutting the phase control film into a symmetrically distributed annular structure, wherein the ring radius r of the nth loop linenSatisfies the following conditions:
wherein f iscFor the designed focal length, λ is the acoustic wavelength, and N is the total number of loops of the ring structure.
Optionally, determining a phase modulating film comprises:
uniformly mixing metal particles or non-metal particles with any density larger than that of the fiber material and a high polymer material or soft material solution with any modulus smaller than that of the particles to obtain a mixed solution;
and (3) taking the mixed solution as a raw material, obtaining electrostatic spinning fibers with particles by utilizing an electrostatic spinning technology, and further forming an electrostatic spinning film by stacking the electrostatic spinning fibers, wherein the electrostatic spinning film is the phase control film.
According to the invention, different particles and different high polymer materials or soft material solutions are mixed to obtain a mixed solution, so that electrostatic spinning films with different diameters and distribution can be prepared, and due to the vibration of the particles in the films, the phase of sound waves with different frequency ranges is changed by 180 degrees, wherein the more the particles are, the lower the response frequency is; the thicker the film (less than 1 mm), the lower the response frequency.
Optionally, the metal or non-metal particles of any density greater than the fibrous material are copper, iron, gold, silver, platinum, cobalt, nickel, lead, and their corresponding oxides.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
1. the invention can realize high-efficiency acoustic focusing and can be used for acoustic application occasions requiring precise control of high energy concentration, such as medical ultrasonic lithotripsy, acoustic positioning heating, acoustic weapons and the like.
2. The size is reduced. Compared with the design of any similar function, the invention utilizes the combined action of two partial areas with 180-degree difference of initial phases, and can reduce the area of the device by half in both the x direction and the y direction, so that the total area of the film can be reduced by 3/4 (the z direction is the incident wave direction, and the xy direction is vertical to the z direction).
3. The energy utilization rate is higher. The invention is based on a full transmission structure, utilizes the energy of the whole plane and has higher energy utilization rate. The invention is a passive device, and has great advantages in energy consumption, volume and portability.
Drawings
FIG. 1 is a schematic flow chart of a method for focusing sound waves based on a patterned clipping technique according to the present invention;
FIG. 2 is a schematic diagram of the cutting of a focusing pattern of a stripe structure according to the present invention;
FIG. 3 is a schematic diagram illustrating the calculation of the transmission integration field according to the present invention;
FIG. 4 is a schematic diagram of the focusing path of the acoustic wave provided by the present invention;
FIG. 5 is a simulated transmission field pattern (xz plane) for a bar structure provided by the present invention;
FIG. 6 is a transmission field diagram (xz plane) for experimental test of a stripe structure provided by the present invention;
FIG. 7 is a schematic diagram of the ring-shaped focus pattern clipping provided by the present invention;
FIG. 8 is a simulated transmission field pattern (xy plane) for a ring structure provided by the present invention;
FIG. 9 is a simulated transmission field pattern (yz plane) for a toroidal structure provided by the present invention;
FIG. 10 is a graph showing a simulation relationship of the focal point energy enhancement factor according to the present invention with the number of fringes and the number of rings N increased;
FIG. 11 is a scanning electron micrograph of a fiber film obtained according to the method of the present invention, wherein the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 8;
FIG. 12 is a scanning electron micrograph of a fiber film obtained according to the method of the present invention, wherein the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 4;
FIG. 13 is a scanning electron micrograph of a fibrous film obtained according to the method of the present invention, wherein the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 2;
FIG. 14 is a scanning electron micrograph of a fiber film obtained according to the method of the present invention, wherein the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 1;
FIG. 15 is a graph showing the results of a sound wave transmission test performed on a fiber film obtained when the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 8;
FIG. 16 is a graph showing the results of a sound wave transmission test performed on a fiber film obtained when the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 4;
FIG. 17 is a graph showing the results of a sound wave transmission test performed on a fiber film obtained when the mass ratio of copper particles to polyvinyl alcohol provided by the present invention is 1: 2;
fig. 18 is a graph showing the results of a sound wave transmission test performed on a fiber film obtained when the mass of copper particles and polyvinyl alcohol provided by the present invention is 1: 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In response to the above deficiencies of the prior art or needs for improvement, the present invention is based on a thin film capable of changing the transmission phase by 180 degrees and specific patterning design rules to achieve acoustic focusing. The film is cut into designed patterns by laser cutting or other cutting means, sound waves with different frequencies can be focused, and the focal length can be adjusted according to the patterns. The flexible film is very convenient to cut, the whole device is light, the cost is low, and the flexible film is beneficial to large-scale production and manufacturing. This approach is also passive, with advantages in power consumption and portability.
Fig. 1 is a schematic flow chart of a method for focusing an acoustic wave based on a patterned cropping technique according to the present invention, as shown in fig. 1, including steps S101 to S102.
S101, determining a phase control film, wherein the phase control film can change the phase of the transmitted sound wave by 180 degrees.
S102, cutting the phase control film to enable the sound wave plane transmitted by the cut phase control film to focus on a focus or to spatially focus on the focus, wherein the wave path difference between the sound wave after passing through the cutting area and the sound wave after passing through the non-cutting area adjacent to the sound wave after passing through the cutting area to reach the focus is half of the wave length of the sound wave by controlling the cutting size.
Optionally, when the acoustic wave plane transmitted by the cut phase control film is focused on a focal point, cutting the phase control film includes:
cutting the phase-adjusting film into symmetrically distributed strip structures, as shown in FIG. 2, with a distance l from the nth line of the symmetry center to the symmetry centernSatisfies the following conditions:
wherein f iscFor the designed focal length, λ is the acoustic wavelength, and N is the number of bus bars on one side of the bar structure.
As shown in fig. 2, according to an embodiment of the present invention, a body is composed of a film 1 to be cut and a cutting pattern 2. And cutting the film according to the method of fig. 2, and calculating the corresponding transmission field distribution according to a Rayleigh-Sophia diffraction formula when the planar sound wave is normally incident to the surface of the cut film.
The formation of the transmission field is illustrated in particular in fig. 3: fig. 3, a and b, are discussed in terms of a rectangular coordinate system and a cylindrical coordinate system, respectively, and the two cases are similar, and are mainly described herein as a rectangular coordinate system. The plane where XOY is located represents a sub sound source plane, the plane where the point S is located is any one of the target transmission planes that we are interested in being parallel to the sound source plane, and P represents sound pressure. The sound pressure (including the amplitude and phase of the sound pressure) at any point of the target plane is the result of the superposition of the sub-sound waves emitted from all the source points on the sound source plane at the target point. From the rayleigh-solifife diffraction integral equation, the sound pressure at a point on the target surface can be expressed as (the portion without the thin film contributes to the transmission field):
wherein,
ω is the angular frequency of the incident wave and k is the wavevector of the incident wave. RhoairIs the density of the air and is,
is a source point (x) under a rectangular coordinate systemS,yS,zS) And the distance, Ω, between the target point (x, y, z)1The integration interval without the thin film portion (cut portion) is shown.
For the part with the film, since the film has a 180-degree phase change to the incident sound wave, which is equivalent to the initial phase of the part is increased by 180 degrees, the expression in the formula is:
wherein omega2The integration interval with the thin film portion is shown.
Further, for the bar structure, the specific integration interval is substituted into the formula, and we can obtain the following expression through simplification:
in a cylindrical coordinate system, the following are similar:
wherein,
is a source point (r) in a cylindrical coordinate systemS,θS,zS) And a target point (r, θ, z).
Fig. 4 is a schematic diagram of the focusing path of the sound wave provided by the present invention, and is shown in fig. 4, in which the black portion (uncut portion) represents that the initial phase is 180 degrees, and the blank portion (cut portion) represents that the initial phase is 0. According to the principle of phase length, the difference of the wave path from two adjacent source points to the focal point should be half of the wavelength, i.e. the phase length
Where π to the left of the equal sign indicates the initial phase 180 degrees different between the film and film-free portions, so that if the left of the equal sign is made equal to π as a whole, the phase difference from the adjacent source to the focus is justPreferably 2 pi, such fields completely overlap without canceling out the part.
Width l of the stripe patternnHas been marked in the figure, n denotes the number of lines to the centre, fcIs the designed focal length, and λ is the acoustic wavelength that needs to be adjusted and controlled correspondingly. Due to l0When the value is 0, we can obtain
The stripe width can be expressed as:
specifically, the larger the maximum value N of N is, the stronger the focusing intensity is, and the larger the corresponding entire image area is, and N designed in fig. 2 is described as an example of 6. f. ofcIs the designed focal length, which can be specified according to the requirements, then lnAnd will vary accordingly.
Fig. 5 and 6 are graphs of simulation and experimental test effects of a specific focusing effect, respectively, in which a plane acoustic wave is normally incident on a patterned device surface, a 180-degree phase change occurs in an acoustic wave incident on a shadow portion (uncut portion) of the device, and no phase change occurs in an acoustic wave incident on a blank portion (cut portion). Each point in the plane is used as a sub sound source to be mutually interfered and superposed, and finally, the point is gathered at the designed focus. From the intensity distributions of fig. 5 and 6, we can see that there is a clear bright spot in the middle, which is the focus of the design, thus showing that the experimental and simulation results are well matched.
As can be seen from fig. 5 and 6, after the phase control film is cut into the strip-shaped structure, the transmitted sound wave focuses the sound wave on the focal point, which illustrates that the sound wave can be focused on the plane by using the cutting method based on the film provided by the present invention.
Optionally, when the sound wave transmitted by the cut phase control film is focused on a focal point in space, cutting the phase control film includes:
cutting the phase control film into a symmetrically distributed annular structure with the nth loop lineRadius r of the ringnSatisfies the following conditions:
wherein f iscFor the designed focal length, λ is the acoustic wavelength, and N is the total number of loops of the ring structure.
FIG. 7 is a schematic diagram of a ring-shaped focusing pattern design, similar to the principle of the bar structure, and accordingly, FIG. 7 shows 1 a film to be cut and 2 a cutting mode, which is analyzed by referring to the focusing theory of the bar structure, in which the ring radius r of the n-th ring barnSatisfy the requirement of
The ring structure has a focusing effect in both dimensions, as opposed to a focusing in only one direction for the strips.
It should be noted that, because the strip-shaped structure and the ring-shaped structure provided by the present invention make the principle of focusing sound waves consistent, the same symbol N may be used to refer to the serial number of the strip-shaped structure lines or the serial number of the ring-shaped structure rings, and N refers to the total number of the strip-shaped structure lines or the total number of the ring-shaped structure rings.
Fig. 8 and 9 are simulation diagrams of focusing effect of the corresponding ring structure, fig. 8 is an xy-section intensity distribution, and fig. 9 is an xz-plane intensity distribution. It can be seen that the energy is mostly concentrated at the central focus and there is focus in both the xy, xz planes.
As can be seen from fig. 8 and 9, after the phase control film is cut into the annular structure, the transmitted sound wave focuses the space on the focal point, which illustrates that the sound wave can be focused by using the cutting method based on the film provided by the present invention.
Fig. 10 is a simulated focal center energy enhancement factor (expressed in dB), and the legend in fig. 10 indicates that the triangle and the square represent the case where the cropping pattern is a stripe and a loop structure, respectively, and it can be seen from fig. 10 that the energy at the focal center increases as the number of stripes (or the number of loop stripes) increases. Their laws are similar, with the energy enhancement factor being positively correlated to the number of fringes, except that the enhancement factor is greater for the annular structure.
The film with the transmission phase changed by 180 degrees is cut into specific patterns, so that the passive regulation and control of the sound wave are realized. For example, cutting the film into a striped pattern (fig. 2) can be used to focus the acoustic waves perpendicular to the stripe direction. If the film is cut into a circular pattern (fig. 7), which can be used to focus in-plane perpendicular to the direction of sound propagation, the corresponding focal intensity will be stronger.
Optionally, determining a phase modulating film comprises: uniformly mixing metal particles or non-metal particles with any density larger than that of the fiber material and a high polymer material or soft material solution with any modulus smaller than that of the particles to obtain a mixed solution; and (3) taking the mixed solution as a raw material, obtaining electrostatic spinning fibers with particles by utilizing an electrostatic spinning technology, and further forming an electrostatic spinning film by stacking the electrostatic spinning fibers, wherein the electrostatic spinning film is the phase control film.
According to the invention, different particles and different high polymer materials or soft material solutions are mixed to obtain a mixed solution, so that electrostatic spinning films with different diameters and distribution can be prepared, and due to the vibration of the particles in the films, the phase of sound waves with different frequency ranges is changed by 180 degrees, wherein the more the particles are, the lower the response frequency is; the thicker the film (less than 1 mm), the lower the response frequency.
Optionally, any metallic or non-metallic particles having a density greater than the fibrous material are copper, iron, gold, silver, platinum, cobalt, nickel, lead, and their corresponding oxides.
Alternatively, the area of the electrospun film is related to the movement range of the injector for spinning in the plane perpendicular to the spinning direction, the larger the movement range, the larger the area of the electrospun film. The thickness of the electrospun film is related to the spinning time, the longer the spinning time, the thicker the thickness of the electrospun film. The diameter of the electrospun fiber is related to the spinning voltage, the larger the spinning voltage, the smaller the diameter of the electrospun fiber. The number of particles in the electrospun film is related to the mass ratio of the particles to the solution of the high molecular material or the soft material, and the larger the mass ratio, the larger the number of particles contained in the electrospun film.
The phase control film provided by the invention is described in detail by combining the following specific embodiments:
example 1:
copper particles with the diameter of 0.5 to 1.5 microns and polyvinyl alcohol (PVA 124) aqueous solution are uniformly mixed, the concentration of the adopted polyvinyl alcohol aqueous solution is 7 to 12 percent, and the mass ratio of the copper particles to the polyvinyl alcohol is specifically adjusted according to actual requirements.
The concentration of the polyvinyl alcohol solution in the embodiment of the present invention may be other concentrations with stable dissolution.
Copper particles are given in the examples of the invention: the polyvinyl alcohol is 1:1, 1:2, 1:4 and 1: 8. The mixed solution is used as a raw material, electrostatic spinning fibers with particles with the diameter of 0.5-1.5 microns can be obtained by using an electrostatic spinning technology, and electrostatic spinning films are formed by stacking the electrostatic spinning fibers.
According to the mixed liquid with different mass ratios of the copper particles and the polyvinyl alcohol, which is prepared by the invention, after the uniformly mixed copper particle/polyvinyl alcohol mixed liquid is obtained, the mixed liquid can be used as a raw material for electrostatic spinning. In the embodiment of the invention, the electrostatic spinning films with different diameters and distributions can be obtained by changing parameters such as receiving distance, spinning voltage, injection speed and the like. In a certain range, the larger the spinning voltage, the smaller the fiber diameter. The speed of the bolus injection needs to be coordinated with the speed of the spinning (mainly the speed of the filament after balancing the electric field force, the surface tension and the like). The recommended spinning conditions are: the environmental temperature is 25 ℃, the humidity is 30-45%, the spinning voltage is 9.7-11.7 kV, and the injection speed is 0.02-0.03 mL/s. Scanning electron micrographs of the surface of the prepared film are shown in fig. 11 to 14, and the mass ratio of the copper particles to the polyvinyl alcohol in the preparation of the electrostatic spinning film is 1:8, 1:4, 1:2 and 1:1, respectively. It can be seen from the figure that the different concentrations are significantly different than the number of particles. Fig. 15 to 18 are results of the acoustic wave transmission test performed on the films of the above-described proportions, respectively. We can see that they are all able to have a 180 degree phase change at the corresponding frequency range (grey areas as shown in fig. 15-18) and maintain a high transmission (greater than 80%). And as the particle fraction increases, the frequency range gradually shifts to lower frequencies, so that these films cover the frequency range from 3.8kHz to 24 kHz.
Example 2:
lead oxide particles with the diameter of 0.5-1.5 microns and Dimethylformamide (DMF) solution (PAN is insoluble in water and soluble in organic solvent such as DMF) of Polyacrylonitrile (PAN) are uniformly mixed, the concentration of the DMF solution of the adopted polyacrylonitrile is 8-12%, and the mass ratio of the lead oxide particles to the polyacrylonitrile is specifically adjusted according to actual requirements.
The concentration of the polyacrylonitrile solution in the embodiment of the present invention may also be other concentrations with stable dissolution.
Lead oxide particles are given in the examples of the invention: polyacrylonitrile is in four cases of 1:1, 1:4, 1:8 and 1: 16. The mixed solution is used as a raw material, electrostatic spinning fibers with particles with the diameter of 0.5-1.5 microns can be obtained by using an electrostatic spinning technology, and electrostatic spinning films are formed by stacking the electrostatic spinning fibers.
According to the mixed liquid with different mass ratios of the lead oxide particles and the polyacrylonitrile, the uniformly mixed lead oxide particle/polyacrylonitrile mixed liquid is obtained, and then the mixed liquid can be used as a raw material for electrostatic spinning. In the embodiment of the invention, the electrostatic spinning films with different diameters and distributions can be obtained by changing parameters such as receiving distance, spinning voltage, injection speed and the like. In a certain range, the larger the spinning voltage, the smaller the fiber diameter. The speed of the bolus injection needs to be coordinated with the speed of the spinning (mainly the speed of the filament after balancing the electric field force, the surface tension and the like). The recommended spinning conditions are: the environmental temperature is 25 ℃, the humidity is 30-45%, the spinning voltage is 8.7-10.7 kV, and the injection speed is 0.03-0.04 mL/s.
It is worth noting that the particles and soft materials used in example 2 can be interchanged with those of example 1, if it is desired that the final film be water insoluble, then a water insoluble polymer such as polyacrylonitrile; if the film is required to have magnetism, magnetic particles such as ferroferric oxide and the like are used.
The electrostatic spinning film based on the invention has controllable thickness, and the longer the spinning time is, the thicker the thickness is; the thickness of the stable film is only 20 microns at the thinnest, which is the controlled wavelength 1/650, which is much thinner than the current level (about 1/250), making it applicable in more scenes. The electrostatic spinning film prepared by the invention is very convenient to cut, the whole device is very light, the cost is lower, and the large-scale production and manufacturing are facilitated. The electrostatic spinning film is adopted to realize the regulation and control of the acoustic wave phase, is passive and has advantages in energy consumption and portability.
The invention is based on the electrostatic spinning technology to manufacture the phase control film. The phase of the transmission of the sound wave is changed by 180 degrees due to the vibration of the particles in the film. The acoustic response frequency of the film is mainly determined by the density of the spun fibers and particles, the modulus ratio, the mass ratio of the total particles to the fiber material, the thickness of the film and the like. And the parameters can be adjusted through the material proportion and the spinning parameters. The film can be continuously manufactured in a large area, and further, the film can be cut by combining with a corresponding cutting technology to manufacture a multifunctional device. The flexible film is very convenient to cut, the whole device is light, the cost is low, and the flexible film is beneficial to large-scale production and manufacturing. This approach is also passive, with advantages in power consumption and portability.
Alternatively, the film capable of changing the transmission phase by 180 degrees may be an electrospun film, or may be any other device or material capable of changing the transmission phase; the portion where no phase change occurs is a portion which is cut (cut), and may be any material which can transmit sound waves completely without changing the transmission phase.
Alternatively, the cutting pattern is not limited to the two schemes described in fig. 2 and fig. 7, the 2 schemes are only representative of focusing patterns, and the method of cutting the film to focus the sound wave falls within the protection scope of the present invention.
Alternatively, such a regulation method is applicable to fluid media, i.e. regulation in air or water or other fluids is applicable.
Optionally, besides the regulation of the acoustic wave, the method is also completely suitable for the regulation of the light wave or the electromagnetic wave, and only the film needs to be replaced by a material capable of changing the transmission phase of the light wave.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (2)
1. A method for focusing an acoustic wave based on a patterned cropping technique, comprising:
determining a phase control film, wherein the phase control film can change the phase of the sound wave transmitted by the phase control film by 180 degrees; the method for determining the phase control film comprises the following steps: uniformly mixing metal particles or non-metal particles with any density larger than that of the fiber material and a high polymer material or soft material solution with any modulus smaller than that of the particles to obtain a mixed solution; taking the mixed solution as a raw material, obtaining electrostatic spinning fibers with particles by using an electrostatic spinning technology, and further forming an electrostatic spinning film by accumulating the electrostatic spinning fibers, wherein the electrostatic spinning film is the phase control film;
cutting the phase control film to enable the sound wave plane transmitted by the cut phase control film to focus on a focus or to spatially focus on the focus, wherein the wave path difference between the sound wave after passing through the cutting area and the sound wave after passing through the non-cutting area adjacent to the sound wave after passing through the cutting area to the focus is half of the wave length of the sound wave by controlling the cutting size; the mode for cutting the phase control film comprises a first mode or a second mode; the first mode is as follows: cutting the phase control film into strip-shaped structures which are symmetrically distributed, wherein the nth cutting line has a width l away from the symmetric centernSatisfies the following conditions:
at this time, fcIn order to design the focal length, lambda is the acoustic wave length, and N is the number of buses on one side of the strip-shaped structure;
the second mode is as follows: cutting the phase control film into a symmetrically distributed annular structure, wherein the ring radius r of the nth loop linenSatisfies the following conditions:
at this time, fcFor the designed focal length, λ is the acoustic wavelength, and N is the total number of loops of the annular structure.
2. The method for focusing acoustic waves based on patterned cutting technology according to claim 1, wherein the metal particles or non-metal particles with the arbitrary density larger than the fiber material are copper, iron, gold, silver, platinum, cobalt, nickel, lead and their corresponding oxides.
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