Elastic wave focusing device using elastic bound state in continuum based on acousto-elastic coupling effect and manufacturing method therefor

Abstract

The present invention relates to an elastic wave focusing device, comprising: an elastic bar which extends in a first direction by a first length; and a sealed cavity which is formed in the elastic bar, wherein the cavity is filled with a first fluid, and if vibration is applied to an end portion of the elastic bar, elastic waves are focused on the elastic bar between the end portion and the center of the cavity.

Description

Elastic wave focusing device and its manufacturing method through elastic binding state due to acoustic-elastic coupling effect

[0001] The present invention relates to an elastic wave focusing device capable of focusing elastic waves of high quality factor by utilizing the acoustic-elastic coupling effect.

[0002] A bound state refers to a physical system in which two or more particles or components remain bound together without an energy input exceeding a certain energy threshold. A bound state is a state in which particles or components are held together by strong forces or interactions, preventing them from moving independently. Bound states are generally stable and can exist at least within a certain energy range. They can persist for long periods of time unless sufficient energy is supplied. For example, atoms remain stable until they absorb or release energy, changing their energy levels or causing ionization.

[0003] For a long time, bound states were believed to be unable to exist within the energy bands of propagating waves. However, in 1929, von Neumann and Wigner first discovered that bound states exist within the energy bands of propagating waves as special solutions to the Schrödinger equation. These states, bound in this special way, are called bound states in the continuum (BIC), and have recently been extensively studied not only in the field of quantum mechanics where they were first discovered, but also in various fields such as optics, semiconductors, and nano-optics.

[0004] Bound states within a continuum can have infinitely diverging quality factors (Q-factors), which can be exploited to create highly focused states. However, resonators with infinitely diverging Q-factors are impossible to realize in reality. Therefore, perturbations are introduced to bound states within a continuum to intentionally lower their Q-factors. This is called a quasi-bound state within the continuum (Q-BIC).

[0005] Although a system that focuses elastic waves by combining elasticity and acoustics using the above-described confinement state within a continuous level has not previously existed, a system and method for efficiently focusing elastic waves can be proposed using this.

[0006] (Patent Document 1) KR 10-2020-0105493 (August 21, 2020)

[0007] The present invention is intended to solve the above problems, and provides a device for focusing elastic waves using a state confined within a continuous level through an elastic-acoustic coupled system, and a method for manufacturing the same.

[0008] In order to achieve the above-mentioned purpose, the present invention provides an elastic wave focusing device and a method for manufacturing an elastic wave focusing device formed as follows.

[0009] An elastic wave focusing device according to one embodiment of the present invention comprises an elastic bar extending in a first direction, a sealed cavity formed inside the elastic bar, the cavity being filled with a first fluid, and when vibration is applied to an end of the elastic bar, elastic waves are focused between the end and the center of the cavity.

[0010] Additionally, the Fabry-Perot resonance frequency of the elastic wave propagating in the first direction at the end of the elastic bar may be the local resonance frequency of the cavity and the frequency at which perturbation occurs. Additionally, the first fluid may be air.

[0011] In addition, a neck portion penetrating the elastic bar may be formed, and an auxiliary material for sealing the neck portion may be further included.

[0012] Additionally, the elastic bar may have a columnar shape with a length longer in the first direction than in the second direction perpendicular to the first direction.

[0013] In addition, the device further includes a vibrator that applies vibration to an end of the elastic bar, and the vibration applied by the vibrator can be focused on the elastic bar within the second distance as an elastic wave.

[0014] A method for manufacturing an elastic wave focusing device according to one embodiment of the present invention includes a first step of calculating a first frequency, which is an eigenmode of an elastic bar formed of an elastic material and having a cavity positioned therein, and a second step of determining a volume at which a first fluid injected into the cavity resonates at the first frequency.

[0015] The present invention can be utilized to implement a quasi-bound state within a continuous level with a very high quality factor (Q-factor) through the above structure and to apply it to an elastic focusing system or elastic energy harvesting.

[0016] In addition, it can be commercially used for various purposes because it can implement a bound state without being limited to specific materials and specific structures.

[0017] FIG. 1 is a perspective view of an elastic wave focusing device according to an embodiment of the present invention.

[0018] Figure 2 is a perspective view of an elastic wave focusing device according to another embodiment of the present invention.

[0019] Figure 3 is a partial diagram of an elastic wave focusing device according to one embodiment of the present invention.

[0020] Figure 4 is a cross-sectional view of an elastic wave focusing device according to an embodiment of the present invention.

[0021] FIG. 5 is a graph showing energy splitting of superimposed modes into three frequencies due to the acoustic-elastic coupling effect in the resonance mode of an elastic wave focusing device according to one embodiment of the present invention.

[0022] Fig. 6 is at the frequency f1 of Fig. 5. shows the displacement distribution at f1 along the X, Y, and Z axes, and p shows the pressure distribution at f1.

[0023] FIG. 7 shows a dimensionless representation of a second distance (l), which is a distance from one of the elastic bar ends to the cavity according to one embodiment of the present invention, and the transmittance by frequency according to the second distance.

[0024] Figure 8 shows the spectrum of transmittance according to frequency.

[0025] FIG. 9 illustrates eigenmodes indicating a quasi-bound state (Q-BIC) within a continuous level confirmed through eigenmode analysis of an elastic wave focusing device according to an embodiment of the present invention.

[0026] Figure 10 shows the quality factor (Q-factor) according to distance (l) observed through eigenmode analysis.

[0027] Figure 11 shows the results of an elastic wave transmission measurement experiment of an elastic wave focusing device according to one embodiment of the present invention as a graph of frequency and acceleration.

[0028] Figure 12 shows a graph of frequency and elastic wave transmittance.

[0029] * Explanation of symbols *

[0030] 1, 1A: Elastic wave focusing device 100, 100A: Elastic bar

[0031] 110, 110A: End of elastic bar 120, 120A: Other end of elastic bar

[0032] 200, 200A: Common part 300, 300A: Wood part

[0033] 400, 400A: Auxiliary material L1: 1st distance

[0034] L2: Second distance C: Center of the common area

[0035] S: empty space l: dimensionless distance

[0036] Hereinafter, specific embodiments of the present invention will be described with reference to the attached drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention will be able to easily propose other regressive inventions or other embodiments included within the scope of the spirit of the present invention by adding, modifying, or deleting other components within the scope of the same spirit. However, this will also be considered to be included within the scope of the spirit of the present invention.

[0037]

[0038] A bound state in the continuum (BIC) manifests itself as a non-decaying resonance, and a commonly used method for forming such a state is the method of using mirror symmetry mismatch. This method is that when the mode shape of the traveling wave and the resonant mode shape inside the resonator are formed to be mirror-symmetrical to each other, the reflectivity of the resonator approaches 1, and the resonator is formed as if it were a Fabry-Perot resonator with an infinite quality factor. Through this method, a structure with an infinite quality factor can be realized.

[0039] The present invention relates to an elastic wave focusing device that forms a local resonator and a Fabry-Perot resonator by forming an acoustic cavity in an elastic bar using the acoustic-elastic coupling effect, and can focus elastic waves with a high quality factor (Q-factor) through their interaction.

[0040]

[0041] FIG. 1 is a perspective view of an elastic wave focusing device according to an embodiment of the present invention.

[0042] An elastic wave focusing device (1) according to one embodiment of the present invention includes an elastic bar (100) and a cavity (200).

[0043] For example, an elastic bar (100) is formed extending in a first direction (X direction), and a sealed cavity (200) is formed inside the elastic bar (100), the cavity (200) is filled with a first fluid, and when vibration is applied to an end (110) of the elastic bar (100), elastic waves can be focused between the end (110) and the center (C) of the cavity (200) of the elastic bar (100).

[0044] Additionally, the Fabry-Perot resonance frequency of the elastic wave propagating in the first direction (X direction) at the end (110) of the elastic bar (100) may be the local resonance frequency of the cavity (200) and the frequency at which perturbation occurs.

[0045] The elastic bar (100) extends in a first direction (X direction) to a first distance (L1) and is formed of an elastic material that is a material through which elastic waves can be transmitted.

[0046] For example, the elastic bar (100) is formed of an elastic material. For example, the elastic bar (100) may be formed by including at least one of metal, glass, or plastic. The elastic bar (100) may be formed as a medium capable of efficiently transmitting elastic waves. As an example of the plastic, it may be manufactured from polymethyl methacrylate (PMMA).

[0047] The elastic bar (100) is formed by being filled with an elastic material, and has a shape in which the length in the second direction (Y direction) perpendicular to the first direction is shorter than the first distance (L1).

[0048] For example, the elastic bar (100) may be a columnar shape having a length in the first direction longer than in the second direction perpendicular to the first direction. The cross-sectional shape of the column is not particularly limited.

[0049] The elastic bar (100) receives vibrations from an exciter (not shown) at one of the two ends (110, 120). At this time, it can be assumed that the elastic waves are incident as longitudinal waves.

[0050] The cavity (200) is located inside the elastic bar (100), and the first fluid is filled in the internal empty space (S, see FIG. 3), and the first fluid is formed to be sealed with the outside of the elastic bar (100). The volume of the cavity (200) is defined as the first volume, and the following will be described.

[0051] The common portion (200) can be positioned at a second distance (L2) in the first direction from one of the two ends (110, 120) of the elastic bar (100) to the center (C) of the common portion (200).

[0052] For example, the cavity (200) may be formed in a regular hexagon. The shape of the cavity (200) is not specific, but it may be formed in a regular hexahedron and may be formed as an empty space so that the first fluid is filled therein.

[0053] For example, the first fluid may be air.

[0054] The type of the first fluid is not limited, but for convenience of production and maintenance, the first fluid may be air. Furthermore, the elastic bar (100) may be formed of a material including at least one of metal, glass, or plastic. Furthermore, the elastic bar (100) may transmit elastic waves at a faster rate than the first fluid.

[0055] According to one embodiment of the present invention, the distance from the end (110) of the elastic bar (100) to the center (C) of the hollow portion (200) is a second distance (L2), and when vibration is applied to the end (110) of the elastic bar (100), elastic waves are focused between the end (110) and the point at the second distance (L2) of the elastic bar (100).

[0056] In addition, when the frequency of the elastic wave propagating in the first direction (X direction) from the end (110) of the elastic bar (100) is the same as the resonant frequency of the cavity (200), a state of confinement within the continuum level occurs, and the Fabry-Perot resonant frequency of the elastic wave propagating in the first direction (X direction) from the end (110) of the elastic bar (100) is the frequency at which perturbation occurs with the local resonant frequency of the cavity (200). The frequency at which perturbation occurs may be selected as one of the natural frequencies of the natural mode of the elastic bar (100).

[0057] In order to implement a bound state within a continuum level, if the local resonance frequency of the cavity (200) and the Fabry-Perot interferometer resonance frequency of the elastic bar (100) up to the second distance (L2), which is the distance from the end (110) of the elastic bar (100) to the center (C) of the cavity (200), are the same, the wave can be focused within the length of the elastic bar (100) up to the second distance (L2).

[0058] According to the Fabry-Perot resonance structure, a medium is inserted between two mirrors having high reflectivity. In the present invention, the cavity (100) functions as a mirror, and the surface of the end portion (110) of the elastic bar (100) can function as another mirror and reflect. Therefore, light can be focused between the end portion (110), which is a part of the elastic bar (100), and the second distance (L2), which is the distance from the center of the cavity.

[0059] In addition, Fano-resonance is a phenomenon in which an asymmetrical frequency response curve is obtained by interference between different energy levels, and can provide an effect in which a state of confinement within a continuum level is realized at the point where the frequency according to the sound of the cavity (200) and the elastic coupling mode of the elastic bar (100) meet.

[0060] Accordingly, a state of confinement within a continuous level is implemented in a portion up to the second distance (L2) of the elastic bar (100), so that an elastic wave focusing device (1) having a high quality factor can be implemented.

[0061]

[0062] According to one embodiment of the present invention, a neck member (300) and an auxiliary member (400) may be further included.

[0063] The neck (300) penetrates the elastic bar (100) and is connected to the cavity (200). The neck (300) can provide an effect according to manufacturing convenience in order to form the first fluid to be positioned within the cavity (200) from the outside of the elastic bar (100).

[0064] The auxiliary material (400) is intended to seal the neck (300) by blocking it from the outside, and may be formed of an elastic material. It may be attached to the neck (300) from the outside of the elastic bar (100) to seal it, or it may be configured to be fitted into the neck (300) to seal the outside and the cavity (200).

[0065] For the convenience of manufacturing and deriving experimental values, a shape such as a neck (300) is formed in the first direction and expressed in the drawing to achieve shape symmetry, but this may not perform the same role as the neck (300) mentioned in the present invention.

[0066]

[0067] FIG. 2 is a perspective view of an elastic wave focusing device according to another embodiment of the present invention.

[0068] According to one embodiment of the present invention, an elastic wave focusing device (1A) may have an elastic bar (100A) in the shape of a cylinder having a circular cross-section. In addition, a length from one of the ends (110A, 120A) of the elastic bar (100A) to the center (C) of the hollow portion (200A) may be a second distance (L2), and in this case, the hollow portion (200A) may be formed in a spherical shape. In addition, as in the above embodiment, a neck portion (300A) and an auxiliary material (400A) may be further included.

[0069] As explained above, since the frequency of the eigenmode is different, the volume and position of the elastic bar (100A) and the cavity (200A) and their shape are not important, and therefore they can be manufactured in various shapes, and the shape and material can be designed differently depending on the convenience of manufacturing.

[0070]

[0071] Hereinafter, an elastic wave focusing device (1) having a shape similar to that of Fig. 1 will be described.

[0072]

[0073] Fig. 3 is a partial diagram showing a part of an elastic wave focusing device corresponding to 1 / 4 when cut in the X and Y directions in Fig. 1.

[0074] FIG. 4 illustrates a cross-sectional view taken along the YZ plane including the center of the cavity in an elastic wave focusing device according to an embodiment of the present invention, such as FIG. 1.

[0075] The common part (200) has an empty space (S) formed inside, into which a first fluid can be injected.

[0076] For example, the second distance (L2) can be non-dimensionalized using the length of one side of the elastic bar (Luc).

[0077] The neck (300) connected to the common part (200) is formed by penetrating the elastic bar (100) and is connected to the outside of the elastic bar (100), and the first fluid can be injected into the common part (200) through the neck (300). However, the neck (300) is formed for convenience of work, and it may be more advantageous to form the common part (200) and the fluid to be injected into the common part (200) without the neck (300).

[0078] In addition, after the first fluid is injected, the first fluid present in the cavity (200) must be sealed from the outside, so that the auxiliary material (400) can be combined with the neck (300) to block communication with the outside.

[0079]

[0080] FIG. 5 is a graph of energy showing that the overlapping modes are split into three frequencies due to the acoustic-elastic coupling effect in the resonance mode of an elastic wave focusing device according to one embodiment of the present invention. In FIG. 5, although the modes are split into three frequencies, f2 and f3 are arbitrarily shown separately to show that some of the frequencies may be the same.

[0081] Fig. 6 is u at the frequency f1 of Fig. 5 based on Fig. 1. x , u y , u z shows the displacement distribution at f1 along the X, Y, and Z axes, and p shows the pressure distribution at f1.

[0082] When a resonance mode is formed in an elastic wave focusing device (1) according to an embodiment of the present invention, energy interaction occurs due to the acoustic-elastic coupling effect. When energy interaction occurs due to the acoustic-elastic coupling effect, one frequency (f) which is the same resonance frequency before the acoustic-elastic coupling i) are separated from the overlapped modes (f1, f2, f3) within the cavity (200). Here, a split mode may occur depending on the degree of symmetry of the energy level due to the stimulus role of the acoustic elastic coupling. For example, according to one embodiment of the present invention, since there is symmetry along the Y-axis and the Z-axis, the frequencies of some of the overlapped modes (f2, f3) may share the same frequency.

[0083] Among the superimposed modes, the mode shape with resonant frequency f1 is u x , u y and u z According to Fig. 6, the eigenmode is concentrated in the cavity (200) in the Y and Z-axis directions, but spreads to the elastic bar (100) as well as the cavity (200) in the X-axis direction. Through this, it can be seen that the eigenmode of the cavity (200) and the eigenmode of the elastic bar (100) interact with each other.

[0084] Looking at the pressure distribution p at f1 of the common part (200), it forms a symmetrical shape in the longitudinal (X-axis) direction, so when elastic waves are propagated in the X-axis direction, they can interact with each other.

[0085] For example, the method proceeds using f1, which is an interacting frequency among the frequencies of the eigenmode, but this frequency may vary depending on the medium and shape of the elastic bar (100) and the shape of the cavity (200), and since there may be multiple frequencies of the eigenmode for an object having a certain shape, one of these may be selected and designed.

[0086]

[0087] Fig. 7 shows a dimensionless distance (l) of a second distance from one end of an elastic bar to a cavity according to an embodiment of the present invention and the transmittance according to the frequency. Fig. 8 shows a spectrum of transmittance according to frequency, and purple in Fig. 7 represents l in a circle in Fig. 8. 6.58, blue in Fig. 7 is a square l in Fig. 8 It shows the spectrum at 2.82.

[0088] The local resonant frequency of the cavity (200) is constant as long as the conditions such as the first fluid and shape do not change. If the length of the elastic bar (100) in the first direction is infinite, the number of singular points shown in Fig. 7 can be infinite. However, since the length of the elastic bar (100) in the first direction is finite, the points where singular points appear are also finite. Figs. 7 and 8 illustrate a case where a cavity (200) exists within an elastic bar (100) having a finite length and has two singular points.

[0089] In order to implement a bound state within a continuum level, as explained above, the cavity (200) and the elastic bar (100) can follow the Fabry-Perot resonance condition at f1. To find this condition, the system can be designed by analyzing the transmission response according to the dimensionless distance (l) and frequency. In this case, the dimensionless distance (l) is the second distance (L2), which is the distance from the end (110) of the elastic bar (100) to the center (C) of the cavity (200), as expressed in Fig. 4, and the length (L) of one side. uc ) can be expressed as a non-dimensional representation.

[0090] Figures 7 and 8 show the system's transmission response as a function of dimensionless distance (l) and frequency. As shown, two regions of high transmission were observed, both of which contained singularities with a transmission value of zero. Referring to the f1 mode in Figure 5, these singularities represent points where the Fabry-Perot resonance condition and the frequency of the acoustic-elastic coupled mode intersect, demonstrating the implementation of a bounded state within the continuum (BIC).

[0091] According to one embodiment of the present invention, the Fabry-Perot resonance frequency of an elastic wave propagating in the first direction (X direction) is similar to the local resonance frequency of the cavity (200), so that perturbation occurs. In this case, the similar range means a range that is slightly deviated from the same range so that perturbation can occur.

[0092] In Figs. 7 and 8, the transmittance spectrum was observed near the singularity in order to implement a quasi-bound state (Q-BIC) by intentionally perturbing the point. In order to intentionally create a perturbation, the position of the cavity (200) must be placed slightly away from the position where the bound state within the continuum level is implemented, and thus, it is formed near the singularity. Near this singularity, the Fano resonance shape, which appears due to the interference between the spectrum of the traveling wave in the elastic bar (100) and the spectrum of the cavity (200), can be observed through the transmittance spectrum.

[0093] For example, if the applied frequency is constant, and the normalized cavity position (l) is 2.89 at the singular point of the continuum-level bound state (BIC), the transmittance (T) in this design exists as a flat value without any change. In the case of a singular point, it is possible to implement a bound state, but since there is no change in the transmittance, the wave theoretically exists infinitely in the front of the cavity and there is no wave escaping, so there is no change when the transmittance is measured. Therefore, there is no way to determine whether this is a bound state based on the transmittance alone.

[0094] Intentionally, the perturbation is a position that deviates from the joint position within a certain range that can be considered similar to the joint position, which is a singularity, and the position of the quasi-bound state (Q-BIC) is l By setting it to 2.82, a rapid change in the transmittance of Fig. 8 can be confirmed.

[0095]

[0096] FIG. 9 illustrates eigenmodes representing a quasi-bound state (Q-BIC) within a continuous level confirmed through eigenmode analysis of some partial states such as FIG. 3 according to one embodiment of the present invention.

[0097] Referring to Fig. 9, the eigenmodes in the quasi-bound state within each continuum level are obtained. It can be seen that the shape of the first eigenmode above is the lowest-order Fabry-Perot mode with two nodes and one doubling. It can be seen that the eigenmode below is the second-order Fabry-Perot mode with three nodes and two doublings. It can be seen that there is almost no leaky wave in the part of the elastic bar (100) that exists beyond the second distance (L2), which is the right part of the cavity (200). That is, the elastic wave is accumulated from one end (110) of the elastic bar (100) to the second distance (L2).

[0098]

[0099] Figure 10 illustrates the quality factor (Q-factor) according to the distance (l) observed through eigenmode analysis. The quality factor that changes as the distance (l) at which the cavity is located in an integrated device such as Figure 1 increases is observed through eigenmode analysis.

[0100] Through Fig. 10, we can observe the diverging quality factor, which is the biggest characteristic of the bound state (BIC) within the continuum level, near the two singular points. It can be confirmed that the area near the singular points is a quasi-bound state (Q-BIC) within the continuum level and has a finite quality factor value. Therefore, if the structure is manufactured according to the present method, an elastic wave focusing device (1) having a high quality factor can be implemented. At this time, the elastic wave is strongly focused from the end (110) of the elastic bar (100) to the second distance (L2).

[0101]

[0102] FIG. 11 shows the results of an elastic wave transmission measurement experiment of an elastic wave focusing device according to one embodiment of the present invention as a graph of frequency and acceleration, and FIG. 12 shows the results as a graph of frequency and elastic wave transmittance.

[0103] The results of an elastic wave experiment to verify the acoustic-elastic coupling effect and interaction are illustrated. It was manufactured in the same shape as Fig. 1, the elastic bar (100) is made of PMMA, and the first fluid is air. The results of the elastic wave transmission measurement of the elastic wave focusing device (1) under the above conditions are shown, and the results are measured using a shaker and an accelerometer. In Fig. 11, the solid line is the data obtained from the measurement, and the dotted line is the fitting line for measuring the quality factor. In addition, Fig. 12 is a spectrum for the transmittance of elastic waves derived by processing the acceleration measurement data as in Fig. 11. It can be confirmed through Fig. 12 that the transmission spectrum exhibits a Fano resonance shape, and through this, it can be seen that the acoustic-elastic coupling effect and elastic wave focusing are well performed.

[0104] An elastic wave focusing device (1) according to an embodiment of the present invention is formed by arranging a cavity (200), which is an acoustic cavity, at a specific location within an elastic bar (100), and can be utilized for implementing a quasi-bound state within a continuous level with a very high quality factor and for an elastic focusing system or elastic energy harvesting. In addition, the elastic wave focusing device (1) according to the present invention can implement a bound state without being limited to a specific material or a specific structure, and thus can be designed and utilized for various purposes.

[0105]

[0106] The following method for manufacturing an elastic wave focusing device is a method for manufacturing an elastic wave focusing device (1) according to one embodiment of the present invention, and unless otherwise specified, the above contents are cited.

[0107] A method for manufacturing an elastic wave focusing device according to one embodiment of the present invention includes a first step of calculating the frequency of an eigenmode of an elastic bar (100), and a second step of determining the position and volume of a cavity (200) arranged within the elastic bar (100) so that a first fluid injected into the cavity (200) resonates at the frequency.

[0108] In addition, a third step of sealing the penetration portion of the elastic bar (100) with an auxiliary material (400) after injecting the first fluid into the common portion (200) may be further included.

[0109] After setting the physical size of the elastic bar (100), when the cavity (200) is positioned inside it, the frequency of the eigenmode and the dimensionless distance (l) are calculated while the cavity (200) exists inside. Then, the position of the cavity (200) is set according to the calculated distance (l) so as to become the second distance (L2). At this time, the volume of the cavity (200) and the second distance (L2) can be derived instead of the dimensionless distance (l), but if the shapes of the cavity and the elastic bar (100) are simple, the calculation can be performed using the dimensionless distance (l) as above.

[0110] When all of the above conditions are set, the process can be carried out by manufacturing a cavity (200) inside an elastic bar (100) according to the settings, injecting a first fluid into the cavity (200), and sealing the neck (300) formed by penetrating the elastic bar (100) with an auxiliary material (400).

[0111]

[0112] An elastic wave focusing device (1) according to an embodiment of the present invention can be helpful in the field of energy harvesting. For example, when converting mechanical energy into electrical energy, the efficiency of energy harvesting can be increased by adding it to an existing piezoelectric sensor. In the past, research was mainly focused on improving the performance of the piezoelectric sensor itself through mechanical deformation. However, according to the present invention, rather than developing the piezoelectric sensor itself, the piezoelectric sensor can be applied by adding it to a section where energy is focused, that is, a section where mechanical deformation is very large, thereby enabling efficient energy harvesting.

[0113]

[0114] Although the present invention has been described above with reference to examples, the present invention is not limited to the above-described examples, and it goes without saying that modifications can be made and implemented by those skilled in the art without changing the technical idea of ​​the present invention as claimed in the claims.

Claims

1. An elastic bar formed by extending in the first direction, A sealed cavity is formed inside the above elastic bar, The above cavity is filled with a first fluid, An elastic wave focusing device in which, when vibration is applied to an end of the elastic bar, elastic waves are focused between the end and the center of the cavity.

2. In paragraph 1, An elastic wave focusing device in which the Fabry-Perot resonance frequency of an elastic wave traveling in the first direction at the end of the elastic bar is the same as the local resonance frequency of the cavity and the frequency at which perturbation occurs.

3. In paragraph 1, An elastic wave focusing device wherein the first fluid is air.

4. In paragraph 1, A neck is formed that penetrates the elastic bar and is connected to the cavity, An elastic wave focusing device further comprising an auxiliary material for sealing the above-mentioned neck.

5. An elastic wave focusing device in the fourth paragraph, wherein the auxiliary material is a material having a faster elastic wave transmission speed than the first fluid.

6. In paragraph 1, The above elastic bar is an elastic wave focusing device having a column shape having a length longer in the first direction than in the second direction perpendicular to the first direction.

7. In paragraph 1, An elastic wave focusing device in which the elastic bar comprises at least one of metal, glass, and plastic as a material, and the elastic wave transmission speed in the elastic bar is faster than that of the first fluid.

8. An elastic wave focusing device in the first paragraph, wherein the joint is formed in a hexagonal shape.

9. The first step of calculating the natural mode frequency of the elastic bar; and A method for manufacturing an elastic wave focusing device, comprising: a second step of determining the position and volume of the cavity arranged within the elastic bar so that the first fluid injected into the cavity resonates at the frequency; 10. In paragraph 9, A method for manufacturing an elastic wave focusing device further comprising a third step of injecting a first fluid into the cavity through the elastic bar and then sealing the penetration portion of the elastic bar with an auxiliary material.

Images