Phononic crystal structure and design method thereof

Abstract

The invention relates to the technical field of photonic crystal design, and discloses a photonic crystal structure and a design method thereof. The design method comprises the following steps: setting a first section size and a target thickness size of a photonic crystal unit, wherein the photonic crystal unit comprises a solid scatterer and a matrix; setting a preset range of second section sizes of the scatterer, and selecting a plurality of different second section sizes in the preset range; obtaining dispersion relation curve graphs corresponding to different second section sizes to obtain a plurality of complete band gaps, and comparing the widths of the plurality of complete band gaps to obtain a target complete band gap; obtaining a target section size of the scatterer according to the target complete band gap; and performing array arrangement on the plurality of phononic crystal units to form the phononic crystal structure. Starting from the phononic crystal unit of the phononic crystal structure, the invention provides a design process of the phononic crystal unit based on material and boundary size determination and with the cross section size of a scatterer as a variable, and obtains the phononic crystal unit and the phononic crystal structure with optimal band gap characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of phononic crystal design, and in particular to a phononic crystal structure and a design method thereof. Background Art

[0002] The Bragg phononic crystal structure can theoretically achieve a gain in the resonator quality factor (Q value) by designing a band gap in the dispersion relation. In the phononic crystal structure, materials with different parameters such as density and elastic modulus related to elastic wave propagation are periodically fused together according to the structure. The materials distributed on the lattice and not connected to each other are called scatterers, and the background medium material that is connected as a whole is called the matrix. The most prominent feature of the phononic crystal structure is its band gap characteristic, that is, elastic waves in the full band gap frequency range will be suppressed when propagating in the phononic crystal, while elastic waves at other frequencies can propagate.

[0003] In the related art, the phononic crystal structure usually has an air phase scatterer, which is in the form of a through-hole structure. However, when the phononic crystal structure with air scatterers is used to detect liquid media, the through-hole scatterers will introduce the liquid to be tested, thereby affecting the dispersion curve and band gap range, and bringing more complex liquid circuit packaging and other problems. Based on this, if a solid medium is selected as a phononic crystal structure with a scatterer, then how to design a phononic crystal structure with excellent band gap characteristics is one of the problems that need to be solved urgently. Summary of the invention

[0004] In view of this, the present invention provides a phononic crystal structure and a design method thereof to solve the problem that there is currently no effective design method for the phononic crystal structure of a solid scatterer.

[0005] In a first aspect, the present invention provides a method for designing a phononic crystal structure, the design method comprising:

[0006] Setting a first cross-sectional dimension of the phononic crystal unit in a first direction and a target thickness dimension of the phononic crystal unit in a second direction perpendicular to the first direction, wherein the phononic crystal unit comprises a scatterer and a substrate coated on a side end of the scatterer, and the scatterer is a solid material;

[0007] Setting a preset range of a second cross-sectional size of the scatterer in the first direction, and selecting a plurality of different second cross-sectional sizes within the preset range;

[0008] Obtaining a dispersion relation curve diagram corresponding to the phononic crystal unit under different second cross-sectional dimensions;

[0009] A plurality of complete band gaps are obtained according to a plurality of dispersion relation curves, and a target complete band gap is obtained by comparing the widths of the plurality of complete band gaps;

[0010] According to the second cross-sectional dimension corresponding to the target complete band gap, the target cross-sectional dimension of the scatterer is obtained to determine the finalized structure of the phononic crystal unit;

[0011] A plurality of phononic crystal units with a fixed structure are arranged in an array to form a phononic crystal structure.

[0012] Beneficial effect: The design method of the phononic crystal structure of the present invention starts from a single phononic crystal unit of the phononic crystal structure, and provides a design process of the phononic crystal unit based on material determination and boundary size determination, but the cross-sectional size of the scatterer is a variable. The second cross-sectional size of different values ​​is selected within a set preset range, and the dispersion relationship curve diagram under different second cross-sectional sizes is constructed to compare and obtain the target complete band gap with the maximum forbidden width, and then the corresponding target cross-sectional size of the scatterer is obtained to obtain a qualitative structure of the phononic crystal unit with the best band gap characteristics. Finally, the phononic crystal unit array is arranged to obtain the phononic crystal structure, so as to achieve effective Q value gain when used in acoustic devices and detection of liquid media.

[0013] In an optional embodiment, in the step of obtaining the dispersion relation graph corresponding to the phononic crystal unit at different second cross-sectional sizes, a model of setting the phononic crystal unit at different second cross-sectional sizes is obtained by a two-dimensional finite element calculation method to obtain the dispersion relation graph.

[0014] Beneficial effects: The finite element method is used and the finite element analysis software is used for calculation, which is suitable for nonlinear and inhomogeneous problems and can efficiently achieve the ideal analysis of phononic crystal structures with complex geometric shapes and boundary conditions.

[0015] In an optional embodiment, after obtaining the target cross-sectional size of the scatterer based on the second cross-sectional size corresponding to the target complete band gap, and before arranging a plurality of phononic crystal units with a fixed structure into an array to form a phononic crystal structure, it also includes: obtaining the target filling rate of the scatterer in the phononic crystal unit based on the target cross-sectional size and the first cross-sectional size.

[0016] Beneficial effect: Different dispersion relation graphs are constructed according to different second cross-sectional dimensions to obtain complete band gaps with different widths. The filling rate can then be directly calculated according to the second cross-sectional dimensions corresponding to different band gaps to obtain the widths of the complete band gaps corresponding to different filling rates. This can then be verified in turn with the width of the complete band gap obtained from the previous dispersion relation graph to further accurately obtain the width of the target complete band gap.

[0017] In an optional implementation, the scatterer is configured to be cylindrical, and a cross section of the scatterer in the first direction is circular.

[0018] Beneficial effects: The circular structure is easy to prepare and convenient for obtaining dispersion relation curves and complete band gaps.

[0019] In an optional embodiment, the second cross-sectional dimension is the cross-sectional radius of the scatterer in the first direction; based on the preset range of the second cross-sectional dimension and the first cross-sectional dimension, the filling rate of the scatterer in the phononic crystal unit is obtained in the range of 0.785% to 63.6%.

[0020] Beneficial effect: By selecting a suitable second cross-sectional size within a limited preset range and then calculating it according to the area ratio, the filling rate of the scatterer in the phononic crystal unit can be obtained, which can not only ensure the integrity of the scatterer structure, but also provide enough different second cross-sectional sizes for selection.

[0021] In an optional embodiment, the scatterer includes a polyparaxylene solid material.

[0022] Beneficial effects: Parylene is a biocompatible material, and the processes of thin-film coating and patterning are stable and mature. Moreover, compared with metal Au, Pb, etc., the material density, elastic modulus, lattice form, etc. of the Lamb wave resonator matrix are more different, which helps to enhance the scattering effect of the incident wave and makes it easier to produce a complete band gap.

[0023] In an optional embodiment, the matrix in the phononic crystal unit is composed of a plurality of dielectric layers.

[0024] Beneficial effects: The matrix of the phononic crystal unit is composed of a multi-layer structure, the material of any dielectric layer is different from that of other dielectric layers, and the scatterer is a solid material that vertically penetrates the matrix along the stacking direction of the dielectric layer. The phononic crystal structure composed of the composite phononic crystal unit has a high reflectivity for sound waves and can effectively reduce the transmission loss of sound wave energy.

[0025] In an optional embodiment, after arranging a plurality of phononic crystal units with a fixed structure in an array to form a phononic crystal structure, the method further includes: obtaining a transmission loss curve of the phononic crystal structure within a target full band gap range.

[0026] Beneficial effect: By conducting an elastic wave blocking loss test on the overall phononic crystal structure composed of a plurality of phononic crystal unit arrays, the transmission loss of elastic waves in the phononic crystal structure at different frequencies is tested, and it is confirmed that the frequency corresponding to the maximum loss interval in the transmission loss curve is basically consistent with the width range of the target complete band gap, that is, the phononic crystal structure composed of phononic crystal units with the target complete band gap also has an effective blocking effect on sound waves.

[0027] In an optional embodiment, after obtaining the transmission loss curve of the phononic crystal structure within the target full band gap range, it also includes: selecting a test frequency within the target full band gap range, and performing an elastic wave test on the phononic crystal structure with the test frequency along the plane where the first direction is located, so as to obtain an elastic wave transmission spectrum in the two-dimensional plane of the phononic crystal structure.

[0028] Beneficial effect: By selecting a certain frequency in the target complete band gap, the phononic crystal structure arranged in the phononic crystal unit array at this frequency is constructed as the supporting boundary of the two-dimensional model, and the transmission state of the sound wave is observed in the plane of the two-dimensional model, it is found that the intensity of elastic waves such as sound waves is significantly reduced when passing through the phononic crystal structure on the right side of the supporting boundary. Therefore, the phononic crystal structure with a frequency within the target complete band gap range can effectively block the elastic waves.

[0029] In a second aspect, the present invention also provides a phononic crystal structure, which is obtained by adopting the above-mentioned design method of the phononic crystal structure. The phononic crystal structure includes a plurality of phononic crystal units arranged in an array, and any phononic crystal unit includes: a scatterer and a matrix, the scatterer includes a solid material, and the scatterer has a target thickness dimension and a target cross-sectional dimension; the matrix is ​​coated on the side end of the scatterer, and the matrix has a target thickness dimension and a first cross-sectional dimension.

[0030] Beneficial effect: Based on the design method of the above-mentioned phononic crystal structure, a phononic crystal unit with a first cross-sectional size and a target thickness size, a phononic crystal unit with a first cross-sectional size, and a scatterer with a target cross-sectional size are obtained, and a phononic crystal unit with a target complete band gap is obtained, thereby forming a phononic crystal structure with excellent band gap characteristics, which can achieve effective blocking of elastic waves and can be widely used as a supporting boundary of acoustic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a schematic flow chart of a method for designing a phononic crystal structure according to an embodiment of the present invention;

[0033] Figure 2 is a schematic structural diagram of a phononic crystal structure according to an embodiment of the present invention;

[0034] Figure 3 is a schematic structural diagram of a phononic crystal unit according to an embodiment of the present invention;

[0035] Figure 4 is a schematic structural diagram of an acoustic device according to an embodiment of the present invention;

[0036] Figure 5 is a cross-sectional schematic diagram of an acoustic device according to an embodiment of the present invention;

[0037] Figure 6 is a dispersion relation curve diagram of a phononic crystal unit with a target complete band gap according to an embodiment of the present invention;

[0038] Figure 7 is a schematic diagram of different complete band gaps corresponding to different filling rates in an embodiment of the present invention;

[0039] Figure 8 is a schematic diagram of transmission loss of elastic waves in phononic crystal structures of different frequencies according to an embodiment of the present invention;

[0040] Fig. 9 is a schematic diagram of the transmission of an elastic wave through the surface of a phononic crystal structure having a frequency within a target complete band gap according to an embodiment of the present invention;

[0041] Fig.10 It is a schematic diagram of the transmission of elastic waves through the surface of a phononic crystal structure having a frequency outside the target complete band gap according to an embodiment of the present invention.

[0042] Description of reference numerals:

[0043] 100, acoustic device; 101, substrate; 1011, substrate layer; 1012, insulating layer; 1013, top silicon layer; 1014, ground electrode layer; 1015, piezoelectric layer; 1016, groove; 1017, supporting boundary; 102, interdigital electrode; 103, ground electrode;

[0044] 10. Phononic crystal structure; 11. Phononic crystal unit; 111. Scatterer; 112. Matrix. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only some structures related to the present invention are shown in the accompanying drawings, rather than all structures. In the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified for the purpose of clear expression, and some details may be omitted. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary, and may be deviated due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. In addition, if one layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0046] The phononic crystal structure is composed of materials of different densities arranged periodically, and its basic characteristic is that it prohibits the propagation of sound waves or elastic waves within a certain frequency range. In the full band gap frequency range, the phononic crystal structure has the characteristics of low transmittance and high reflectivity for elastic waves. In the related art, the phononic crystal structure with band gap characteristics has a wide range of application value in the acoustic resonator of micro-electromechanical systems. The present invention is explained by taking the Lamb wave (hereinafter referred to as Lamb wave) resonator with a phononic crystal structure in an acoustic device as an example. At present, when the phononic crystal structure in the Lamb wave resonator is used as a supporting boundary, its scatterer is air, which is manifested as a structural form of opening a through hole on the substrate. The air scatterer forms a forbidden band to achieve the blocking effect on the sound wave, but when used for testing liquid media, the liquid medium can flow in the through hole, which will cause the destruction of the band gap characteristics of the original air scatterer. Therefore, it is urgent to design a phononic crystal structure with a solid scatterer, and ensure that the solid scatterer has an optimal filling ratio and the best band gap characteristics in the matrix of the phononic crystal structure.

[0047] Based on this, see Figures 1 to 10 As shown, this embodiment provides a design method for a phononic crystal structure. Figure 1 The following is a flow chart of the design method, which includes the following steps:

[0048] Step S101, setting a first cross-sectional dimension of the phononic crystal unit 11 in a first direction and a target thickness dimension of the phononic crystal unit 11 in a second direction perpendicular to the first direction, wherein the phononic crystal unit 11 includes a scatterer 111 and a substrate 112 coated on a side end of the scatterer 111, and the scatterer 111 is a solid material.

[0049] See also Figure 2 and Figure 3 In this embodiment, the extension direction of the xy plane is taken as the first direction, and the direction of the z axis is taken as the second direction for reference. The phononic crystal structure 10 includes a plurality of phononic crystal units 11. Therefore, in this embodiment, a single phononic crystal unit 11 is first designed: first, the first cross-sectional dimension of the single phononic crystal unit 11 in the xy plane is set, that is, the boundary dimension of the substrate 112 is set; the cross-sectional dimension described in this embodiment is the necessary dimension for calculating the cross-sectional area. The cross-sectional shape of the phononic crystal unit 11 in the xy plane can be a square, a rhombus, a hexagon or other different shapes, which are not limited here. In this embodiment, the cross-sectional shape of the phononic crystal unit 11 in the xy plane is set to be a square, and the side length of the square is set to 40 μm, which is used as the first cross-sectional dimension of the phononic crystal unit 11; secondly, the target thickness dimension of the phononic crystal unit 11 in the z-axis direction is set, and the target thickness dimension is set to 4.2 μm in this embodiment; at the same time, a certain solid material is selected as the scatterer 111 filled in the substrate 112, and in addition, it also includes selecting a certain substrate 112 material. It should be known that the specific dimensional values ​​and materials set above can be changed according to the material of the phononic crystal structure 10 and different application requirements. In this step, only a certain value and a certain material are required to provide a basis for subsequent design.

[0050] The phononic crystal structure 10 of this embodiment can be arranged as follows Figure 4 and Figure 5 In the acoustic device 100 shown, for example, a support boundary 1017 for a lamb wave resonator, the specific structure of the acoustic device 100 will be described in detail later.

[0051] Step S102 : setting a preset range of a second cross-sectional size of the scatterer 111 in the first direction, and selecting a plurality of different second cross-sectional sizes within the preset range.

[0052] A scatterer 111 is arranged within the boundary of the substrate 112 and penetrates along the second direction, i.e., the z-axis. The cross-sectional shape of the scatterer 111 in the first direction, i.e., the plane where the xy is located, may be a single circle, multiple circles, a ring, or other different shapes. In this embodiment, the cross-sectional figure of the scatterer 111 in the plane where the xy is located is a circle, and the second cross-sectional size is the radius of the circle. Therefore, a radius range of the circular cross-section is preset within the boundary of the substrate 112, for example, a radius range of 1μm to 10μm, or 5μm to 15μm, or 10μm to 18μm, etc., is set as a preset range of the second cross-sectional size, and then multiple different values ​​are selected within the preset range as the second cross-sectional size to be used, for example, 2μm, 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, etc., are selected as different second cross-sectional sizes.

[0053] Step S103 , obtaining a dispersion relation curve diagram corresponding to the phononic crystal unit 11 at different second cross-sectional sizes.

[0054] According to the above-mentioned settings, the first cross-sectional dimension of the phononic crystal unit 11, the target thickness dimension and the scatterer 111 of the determined material, the scatterer 111 of the determined material has a determined density value, and on this basis, combined with different second cross-sectional dimensions, the dispersion relationship curve graphs corresponding to the second cross-sectional dimensions of different numerical values ​​are obtained, and then a plurality of different dispersion relationship curve graphs corresponding to different second cross-sectional dimensions are obtained.

[0055] Step S104, obtaining a plurality of complete band gaps according to a plurality of dispersion relation curves, and comparing the widths of the plurality of complete band gaps to obtain a target complete band gap.

[0056] Figure 6 After comparing multiple dispersion relation graphs, the dispersion relation graph with the target complete band gap is obtained. In this embodiment, the target complete band gap is the one with the largest band gap range among the multiple complete band gaps. The complete band gap is also the forbidden band, and the complete band gap width is also the forbidden band width. Figure 6 Take as an example, the dotted part is the frequency change curve of different elastic waves, such as sound waves during transmission, such as Figure 6 It can be seen that there is a large gap between the frequency change curves of different sound waves ( Figure 6 The black part in the figure is the complete band gap corresponding to the second cross-sectional size selected above. By comparing the widths of multiple complete band gaps corresponding to different second cross-sectional sizes, the target complete band gap with the largest band gap width is obtained. Of course, the other complete band gap parameters obtained can also be used for other purposes.

[0057] The complete bandgap characteristics can be obtained by using different numerical calculation methods, such as plane wave expansion method, finite difference time domain method, multiple scattering theory, DtN map method, finite element method, concentrated mass method, etc.

[0058] Step S105 , obtaining a target cross-sectional dimension of the scatterer 111 according to the second cross-sectional dimension corresponding to the target complete band gap, so as to determine a finalized structure of the phononic crystal unit 11 .

[0059] As described above, according to the comparison, the target complete band gap with the largest width is obtained, and the second cross-sectional dimension selected when the target complete band gap is obtained is used as the target cross-sectional dimension of the scatterer 111 of the phononic crystal unit 11 in this embodiment. At this time, the first cross-sectional dimension of the phononic crystal unit 11, that is, the boundary dimension of the substrate 112, the target thickness dimension of the phononic crystal unit 11, and the second cross-sectional dimension of the scatterer 111 are known, so the complete structural dimension of the single phononic crystal unit 11, that is, the stereotyped structure of the phononic crystal unit 11, can be obtained, such as Figure 2 shown.

[0060] Step S106 , arranging a plurality of phononic crystal units 11 with a fixed structure into an array to form a phononic crystal structure 10 .

[0061] refer to Figure 1 , a plurality of shaped phononic crystal units 11 are closely arranged to form an array-arranged phononic crystal structure 10. In other embodiments, a thin film layer having the same composition and equal thickness as the matrix 112 can also be formed according to the shaped structure of the phononic crystal unit 11 obtained above, and then the range of the plurality of phononic crystal units 11 is divided on the surface of the thin film layer according to the first cross-sectional size, and then the range of the scatterer 111 is determined according to the second cross-sectional size, and a scatterer 111 penetrating the thin film layer is formed within the range, so that the obtained thin film layer having the phononic crystal structure 10 can be used as the support boundary 1017 of the acoustic device 100.

[0062] In this embodiment, the design of the phononic crystal structure 10 is firstly carried out from a unit cell constituting the phononic crystal structure 10, that is, the phononic crystal unit 11. The design of the phononic crystal unit 11 includes: determining the plane boundary range and thickness of the phononic crystal unit 11 as a whole, that is, setting the first cross-sectional dimension and target thickness dimension of the phononic crystal unit 11, and determining the material selection of the substrate 112 and the scatterer 111 in the phononic crystal unit 11; then, within the boundary dimension range of the phononic crystal unit 11, presetting the range of the second cross-sectional dimension of the scatterer 111, and selecting a plurality of different The second cross-sectional size of the value; then obtain different dispersion relation curves according to different second cross-sectional sizes, compare the complete band gaps in multiple dispersion relation curves, and obtain the target complete band gap with the largest required band gap width. The larger the band gap width, the more effective the blocking of sound waves in a wider range can be achieved; then obtain the target cross-sectional size of the scatterer 111 according to the target complete band gap, and then obtain the first cross-sectional size, target thickness size and second cross-sectional size required for the molding of the phononic crystal unit 11, so as to obtain the phononic crystal unit 11 with the best band gap characteristics; finally, according to the obtained phononic crystal unit 11. Prepare a phononic crystal structure 10 with multiple phononic crystal units 11, and complete the design of the phononic crystal structure 10 with the best band gap characteristics.

[0063] In summary, the design method of the phononic crystal structure of the present embodiment starts from a single phononic crystal unit 11 of the phononic crystal structure 10, and provides a design process of the phononic crystal unit 11 based on material determination and boundary size determination, but the cross-sectional size of the scatterer 111 is a variable. A second cross-sectional size with different values ​​is selected within a set preset range, and a dispersion relationship curve diagram under different second cross-sectional sizes is constructed to compare and obtain the target complete band gap with the maximum forbidden width, and then the corresponding target cross-sectional size of the scatterer 111 is obtained to obtain a qualitative structure of the phononic crystal unit 11 with the best band gap characteristics. Finally, the phononic crystal units 11 are arranged in an array to obtain the phononic crystal structure 10, so as to achieve the effective Q value gain when used in the acoustic device 100 and the detection of the liquid medium.

[0064] In one embodiment, in the step S103 of obtaining the dispersion relation graph corresponding to the phononic crystal unit 11 at different second cross-sectional sizes, a model of the phononic crystal unit 11 at different second cross-sectional sizes is obtained by a two-dimensional finite element calculation method to obtain the dispersion relation graph.

[0065] In this embodiment, the finite element method is used to perform calculations with the aid of finite element analysis software, which is suitable for nonlinear and inhomogeneous problems and can efficiently achieve an ideal analysis of the phononic crystal structure 10 with complex geometric shapes and boundary conditions.

[0066] On the basis of the above scheme, in this embodiment, after step S105 of obtaining the target cross-sectional size of the scatterer 111 according to the second cross-sectional size corresponding to the target complete band gap, and before step S106 of arranging a plurality of phononic crystal units 11 with a fixed structure in an array to form a phononic crystal structure 10, it also includes: obtaining the target filling rate of the scatterer 111 in the phononic crystal unit 11 according to the target cross-sectional size and the first cross-sectional size.

[0067] Specifically, the cross-sectional area of ​​the phononic crystal unit 11 perpendicular to the z-axis direction can be obtained according to the first cross-sectional size. Similarly, the cross-sectional area of ​​the scatterer 111 perpendicular to the z-axis direction can be obtained according to the target cross-sectional size. The ratio of the cross-sectional area of ​​the scatterer 111 to the cross-sectional area of ​​the phononic crystal unit 11 as a whole is the target filling rate of the scatterer 111 in the phononic crystal unit 11 with the maximum complete band gap width, and the optimal filling rate is obtained. Specifically, different dispersion relation curves are constructed according to different second cross-sectional sizes to obtain complete band gaps with different widths. After that, the filling rate can also be directly calculated according to the second cross-sectional sizes corresponding to different band gaps, and the filling rate is obtained as shown in the following figure. Figure 7 The width of the complete band gap corresponding to the different filling rates shown can be verified in turn with the width of the complete band gap obtained in the previous dispersion relation curve diagram to further accurately obtain the target complete band gap width.

[0068] As a preferred implementation, the scatterer 111 of this embodiment is set to be cylindrical, and the cross section of the scatterer 111 in the first direction is circular. The circular structure is easy to prepare and is convenient for obtaining the dispersion relation curve and the complete band gap.

[0069] Based on this, the second cross-sectional dimension is the cross-sectional radius of the scatterer 111 in the first direction, and the preset range of the cross-sectional radius is set to 2μm to 18μm; according to the preset range of the second cross-sectional dimension and the first cross-sectional dimension, the filling rate of the scatterer 111 in the phononic crystal unit 11 is obtained in the range of 0.785% to 63.6%.

[0070] For example, the second cross-sectional size of the scatterer 111, i.e., the cross-sectional radius, can be selected from different sizes such as 2μm, 4μm, 5μm, 7μm, 8μm, 10μm, 13μm, 15μm, 18μm, etc. Select a suitable second cross-sectional size within the preset range defined above, and then calculate the filling rate of the scatterer 111 in the phononic crystal unit 11 according to the area ratio. Specifically, by multiplying π by the square of the cross-sectional radius of the scatterer 111 and then dividing by the cross-sectional area of ​​the substrate 112, that is, by the formula The filling rate of the scatterer 111 in the phononic crystal unit 11 limited by the above numerical range is in the range of 0.785% to 63.6%, which can ensure the integrity of the structure of the scatterer 111 and provide enough different second cross-sectional sizes for selection.

[0071] In one embodiment, the scatterer 111 is a solid polyparaxylene material. Polyparaxylene is also known as Parylene. In this embodiment, Parylene-C is selected as the material of the scatterer 111. Parylene is a biocompatible material, and the processes of thin film coating and patterning are stable and mature. Moreover, compared with metal Au, Pb, etc., Parylene has greater differences in material density, elastic modulus, lattice form, etc. from the Lamb wave resonator matrix 112. The greater the difference in component material parameters (also called contrast) between the scatterer 111 and the matrix 112 of the phononic crystal structure 10, the stronger the scattering effect of the incident wave, and the easier it is to produce a complete band gap.

[0072] In this embodiment, the target cross-sectional size of the scatterer 111, i.e., the cross-sectional radius, is 6 μm, and the first cross-sectional size of the phononic crystal unit 11, i.e., the side length, is 40 μm. According to the area ratio of the phononic crystal unit 11, the target filling rate of the scatterer 111 in this embodiment is 7.065%. Figure 7 As shown. Whether the radius of the scatterer 111 is smaller or larger, the width of the complete band gap is less than this value. When the radius of the scatterer 111 is 2μm, the width of the complete band gap is 9.753MHz; when the radius exceeds 6μm, the band gap width decreases, and when the radius of the scatterer 111 is 18μm, the band gap width is only 4.621MHz, after which the scatterer 111 of the Parylene material no longer has a complete band gap.

[0073] In this embodiment, the lower bandgap frequency of the target complete bandgap obtained in step S104 is 50.50 MHz, and the upper bandgap frequency is 102.08 MHz, that is, the width of the target complete bandgap is 51.58 MHz.

[0074] That is, the phononic crystal unit 11 with a cross-sectional radius of 6 μm and a side length of 40 μm of the scatterer 111 obtained by the design method of this embodiment has a target complete band gap of 50.50 MHz to 102.08 MHz and a width of up to 51.58 MHz, and has excellent band gap characteristics.

[0075] In this embodiment, the matrix 112 in the phononic crystal unit 11 is composed of multiple dielectric layers, the material of any dielectric layer is different from that of other dielectric layers, and the scatterer 111 is a solid material that vertically penetrates the matrix 112 along the stacking direction of the dielectric layer. The phononic crystal structure 10 composed of the composite phononic crystal unit 11 has a high reflectivity for sound waves and can effectively reduce the transmission loss of sound wave energy.

[0076] In one embodiment, after the step S106 of arranging a plurality of phononic crystal units 11 having a fixed structure into an array to form a phononic crystal structure 10, the method further includes:

[0077] Step S107 , obtaining a transmission loss curve of the phononic crystal structure 10 within the target full band gap range.

[0078] In the above scheme, a phononic crystal unit 11 with the best band gap characteristics is obtained, and now the elastic wave blocking loss test is performed on the entire phononic crystal structure 10 composed of a plurality of phononic crystal units 11 arranged in an array. Specifically, the transmission loss of elastic waves in the phononic crystal structure 10 at different frequencies is tested, and the following is obtained: Figure 8 The elastic wave transmission loss curve diagram shown in FIG. 1 is a schematic diagram of an elastic wave transmission loss curve. The elastic wave in this embodiment is an acoustic wave. Figure 8 It can be seen that the frequency corresponding to the first maximum loss interval in the transmission loss curve is basically consistent with the width range of the above-mentioned target complete band gap, and the maximum transmission loss of the sound wave can reach 270dB. Therefore, it can be seen that the phononic crystal structure 10 composed of the phononic crystal unit 11 with the target complete band gap still has an effective blocking effect on sound waves.

[0079] On the basis of the above scheme, after step S107 of obtaining the transmission loss curve of the phononic crystal structure 10 within the target full band gap range, the method further includes:

[0080] Step S108 , selecting a test frequency within the target complete band gap range, and performing an elastic wave test on the phononic crystal structure 10 having the test frequency along the plane where the first direction is located, so as to obtain an elastic wave transmission spectrum in the two-dimensional plane of the phononic crystal structure 10 .

[0081] A certain frequency is selected from the target complete band gap obtained above, and the phononic crystal structure 10 with the phononic crystal units 11 arrayed at this frequency is constructed as the support boundary 1017 of the two-dimensional model, and the transmission state of the sound wave is observed in the plane of the two-dimensional model. In this embodiment, the test frequency is selected as 78MHz, and the Fig. 9 It can be seen that the intensity of elastic waves such as sound waves decreases significantly when passing through the phononic crystal structure 10 on the right side of the support boundary 1017. Therefore, the phononic crystal structure 10 with a frequency of 78 MHz can effectively block the elastic waves.

[0082] On the contrary, similarly, a certain frequency is selected outside the target full band gap, and the phononic crystal structure 10 with the phononic crystal units 11 arrayed at this frequency is constructed as the support boundary 1017 of the two-dimensional model, and the transmission state of the sound wave is observed in the plane of the two-dimensional model. In this embodiment, the test frequency is selected as 132MHz, and the Fig.10It can be seen that when elastic waves such as sound waves pass through the phononic crystal structure 10 on the right side of the support boundary 1017, the intensity is basically not weakened. Therefore, when the frequency selection is not within the target band gap range, the phononic crystal structure 10 cannot effectively block the elastic waves.

[0083] The present embodiment also provides a phononic crystal structure 10, which is obtained by adopting the above-mentioned design method of the phononic crystal structure. The phononic crystal structure 10 includes a plurality of phononic crystal units 11 arranged in an array, and any phononic crystal unit 11 includes a scatterer 111 and a matrix 112. The scatterer 111 includes a solid material and has a target thickness dimension and a target cross-sectional dimension; the matrix 112 is coated on the side end of the scatterer 111 and has a target thickness dimension and a first cross-sectional dimension.

[0084] Exemplarily, the above-mentioned scatterer 111 can be made of polyparaxylene solid material, the thickness of the substrate 112 is equal to that of the scatterer 111, the substrate 112 includes a stacked top silicon 1013, a ground electrode layer 1014 and a piezoelectric layer 1015, the thickness of the top silicon 1013 can be set to 2μm; the ground electrode layer 1014 can be a metal molybdenum (Mo) with a thickness of 0.2μm; the piezoelectric layer 1015 can be an aluminum nitride (AlN) with a thickness of 2μm, then the thickness of the scatterer 111 and the substrate 112 are both 4.2μm, that is, the target thickness dimension of the phononic crystal unit 11 is set to 4.2μm, at this time, the phononic crystal unit 11 with the widest band gap and the phononic crystal structure 10 are obtained, and effective reflection of sound waves in a wide frequency range is achieved. In addition, exemplarily, the cross-sectional shape of the phononic crystal unit 11 of this embodiment is selected as a square, then the first cross-sectional dimension is the side length of the square, set to 40μm.

[0085] According to the design method of the phononic crystal structure, the target cross-sectional size of the scatterer 111 is 6 μm. Based on the phononic crystal unit 11 with a thickness of 4.2 μm, the phononic crystal unit 11 with a cross-sectional side length of 40 μm, and the scatterer 111 with a cross-sectional radius of 6 μm, a phononic crystal unit 11 with a target full band gap of 50.50 MHz to 102.08 MHz is obtained, thereby forming a phononic crystal structure 10 with excellent band gap characteristics, which can effectively block elastic waves and is widely used in the support boundary 1017 of the acoustic device 100.

[0086] The phononic crystal structure 10 obtained above can be used in an acoustic device 100 injected into a lamb wave resonator.

[0087] refer to Figure 4 and Figure 5The acoustic device 100 includes a substrate 112, an interdigitated electrode 102, a ground electrode 103 and the above-mentioned phononic crystal structure 10, wherein the substrate 112 includes a substrate layer 1011, an insulating layer 1012, a top silicon layer 1013, a ground electrode layer 1014 and a piezoelectric layer 1015 stacked along the z-axis, and a groove 1016 is formed on the side of the substrate 101 away from the piezoelectric layer 1015, and the groove 1016 is suitable for arranging a medium to be measured, and the groove 1016 runs through the substrate layer 1011, the insulating layer 1012 and the top silicon layer 1013, and the retained ground electrode layer 1014 and the piezoelectric layer 1015 constitute a support boundary 1017, and the interdigitated electrode 102, the ground electrode 103 and the phononic crystal structure 10 are only arranged in the corresponding support boundary 1017 area above the groove 1016, and the phononic crystal structure 10 is located on both sides of the interdigitated electrode 102.

[0088] The phononic crystal structure 10 is located within the support boundary 1017 corresponding to the groove 1016 , so that the phononic crystal structure 10 is located within the effective resonance region of the acoustic device 100 , thereby forming an efficient reflection of the sound wave energy.

[0089] The further functional description of each of the above modules is the same as that of the above corresponding embodiments and will not be repeated here.

[0090] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0091] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for designing a phononic crystal structure, characterized in that: The design method comprises: Setting a first cross-sectional dimension of a phononic crystal unit in a first direction and a target thickness dimension of the phononic crystal unit in a second direction perpendicular to the first direction, wherein the phononic crystal unit comprises a scatterer and a substrate coated on a side end of the scatterer, and the scatterer is a solid material; Setting a preset range of a second cross-sectional size of the scatterer in the first direction, and selecting a plurality of different second cross-sectional sizes within the preset range; Obtaining a dispersion relation curve graph corresponding to the phononic crystal unit under different second cross-sectional dimensions; Obtaining a plurality of complete band gaps according to the plurality of dispersion relation curves, and comparing the widths of the plurality of complete band gaps to obtain a target complete band gap; Obtaining a target cross-sectional dimension of the scatterer according to the second cross-sectional dimension corresponding to the target complete band gap, so as to determine a finalized structure of the phononic crystal unit; A plurality of the phononic crystal units with a fixed structure are arranged in an array to form a phononic crystal structure.

2. The design method of the phononic crystal unit according to claim 1, characterized in that: In the step of obtaining the dispersion relation graph corresponding to the phononic crystal unit at different second cross-sectional sizes, a model of the phononic crystal unit at different second cross-sectional sizes is obtained by a two-dimensional finite element calculation method to obtain the dispersion relation graph.

3. The design method of the phononic crystal unit according to claim 2, characterized in that: After obtaining the target cross-sectional size of the scatterer according to the second cross-sectional size corresponding to the target complete band gap, and before arranging a plurality of the phononic crystal units having a shaped structure in an array to form a phononic crystal structure, the method further includes: A target filling rate of the scatterer in the phononic crystal unit is obtained according to the target cross-sectional size and the first cross-sectional size.

4. The design method of the phononic crystal unit according to claim 3, characterized in that: The scatterer is configured in a cylindrical shape, and a cross section of the scatterer in the first direction is circular.

5. The method for designing a phononic crystal unit according to claim 4, characterized in that: The second cross-sectional dimension is the cross-sectional radius of the scatterer in the first direction; according to the preset range of the second cross-sectional dimension and the first cross-sectional dimension, the filling rate of the scatterer in the phononic crystal unit is obtained in the range of 0.785% to 63.6%.

6. The method for designing a phononic crystal unit according to claim 5, characterized in that: The scatterer includes a polyparaxylene solid material.

7. The method for designing a phononic crystal unit according to claim 6, characterized in that: The matrix in the phononic crystal unit is composed of multiple dielectric layers.

8. The method for designing a phononic crystal unit according to any one of claims 1 to 7, characterized in that: After arranging a plurality of the phononic crystal units having a fixed structure in an array to form a phononic crystal structure, the method further includes: A transmission loss curve of the phononic crystal structure within the target full bandgap range is obtained.

9. The method for designing a phononic crystal unit according to claim 8, characterized in that: After obtaining the transmission loss curve of the phononic crystal structure within the target full band gap range, the method further includes: A test frequency is selected within the target complete band gap range, and an elastic wave test is performed on the phononic crystal structure having the test frequency along the plane where the first direction is located, so as to obtain an elastic wave transmission spectrum in a two-dimensional plane of the phononic crystal structure.

10. A phononic crystal structure, obtained by the design method of a phononic crystal structure according to any one of claims 1 to 9, characterized in that: The phononic crystal structure includes a plurality of phononic crystal units arranged in an array, and any of the phononic crystal units includes: A scatterer, the scatterer comprising a solid material; the scatterer having a target thickness dimension and a target cross-sectional dimension; A substrate is coated on the side end of the scatterer; the substrate has a target thickness dimension and a first cross-sectional dimension.

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