Energy harvesting device

Abstract

One embodiment of the present invention provides an energy harvesting device comprising: a body; a plurality of unit pattern portions formed and arranged periodically on the body, each including a protrusion formed to protrude in one direction from a surface of the body and a through-hole formed to penetrate the body along the one direction; a defect portion disposed on the body and formed at a position adjacent to some of the plurality of unit pattern portions; and an energy conversion portion disposed in the defect portion.

Description

energy harvesting devices

[0001] The present invention relates to an energy harvesting device based on elastic metamaterial.

[0002] Recent rapid advances in low-power electronic device technology have enabled the miniaturization of various electrical devices and their operation at microwatts. In particular, the miniaturization of various types of sensors, including environmental diagnostic sensors for buildings and bridges, safety diagnostic sensors for mechanical structures such as ships and aircraft, and sensors in home automation systems, has enabled more efficient and continuous sensor operation by initially embedding sensors in these structures and configuring them as wireless networks. The continuous monitoring system of these wireless sensor networks requires a power supply system for each sensor node. While batteries can be used for this power supply, these batteries have a short lifespan. Because the sensors in wireless sensor networks must be embedded in structures, battery replacement is either impossible or highly inefficient. To address this issue, energy harvesting methods have been developed, which generate and supply power from surrounding energy sources.

[0003] Well-known energy harvesting methods include generating electricity from solar energy using solar cells, generating electricity from thermal energy using the Seebeck effect, and generating electricity from vibrational energy using Faraday's law of electromagnetic induction, electrostatic effect, piezoelectric effect, or magnetostriction effect. Among these methods, a defect-based energy harvesting device applies a wave at a frequency corresponding to a defect band. When the defect resonates in a specific defect mode shape, the wave energy is localized near the defect, thereby improving energy harvesting performance.

[0004] Meanwhile, metamaterials are materials that can implement previously unobserved strange wave phenomena by periodically arranging artificially designed unit structures and depending on the relationship between the periodicity of the arrangement and the operating wavelength, these metamaterials can be used for various purposes such as refraction, condensation, and reflection of waves, especially for controlling elastic waves among various waves.

[0005] However, due to limitations such as design complexity and limited structural size, existing elastic metamaterials have largely focused on wave control in the high-frequency range. In particular, active research has been conducted to improve the performance of piezoelectric energy harvesting, which converts elastic wave energy into electrical energy by utilizing wave coherence. However, research on piezoelectric energy harvesting using existing metamaterials has been limited to the high-frequency range, limiting its application in real life.

[0006] The present invention was created to solve the above problems, and its purpose is to provide an energy harvesting device that can harvest electric energy not only in the high frequency range but also in the low frequency range by forming a band gap having an extended area simultaneously in the low frequency range and the high frequency range.

[0007] In order to achieve the above object, an energy harvesting device according to one embodiment of the present invention may include an object, a protrusion formed on the object and protruding in one direction from a surface of the object, a penetration formed by penetrating the object along the one direction, a plurality of unit pattern portions periodically arranged on the object, a defect portion arranged on the object and formed at a position adjacent to some of the plurality of unit pattern portions, and an energy conversion portion arranged on the defect portion.

[0008] In an embodiment of the present invention, the unit pattern portion may have a shape in which a plurality of penetrating portions surround the protrusion with the protrusion as the center, but are spaced apart from each other.

[0009] In an embodiment of the present invention, a plurality of the unit pattern portions may be arranged in a grid shape on the object.

[0010] In an embodiment of the present invention, the defective portion (P20) may be an area surrounded by a plurality of the unit pattern portions, but in which the protrusion portion is not formed.

[0011] In an embodiment of the present invention, in the defective portion (P20), a first band gap can be generated in a first frequency band by local resonance induced by the protrusion, and a second band gap can be generated in a second frequency band by the periodicity of the penetration portion.

[0012] In an embodiment of the present invention, the second frequency band may be a higher frequency band than the first frequency band.

[0013] In an embodiment of the present invention, the first band gap and the second band gap can be created simultaneously.

[0014] In an embodiment of the present invention, when a band gap is generated, the area of ​​the first band gap and the area of ​​the second band gap can be expanded due to the interaction between the protrusion and the penetration.

[0015] In an embodiment of the present invention, the protrusion may be in the form of a cylindrical projection, and the through-hole may be in the form of a through-hole having a circular cross-section.

[0016] In an embodiment of the present invention, the protrusion and the penetration may have the same diameter.

[0017] In an embodiment of the present invention, the energy conversion unit may include a piezoelectric element.

[0018] In an embodiment of the present invention, the object and the protrusion may be made of an elastic metamaterial.

[0019] As described above, the energy harvesting device according to embodiments of the present invention can form a band gap having an extended area simultaneously in a low-frequency band and a high-frequency band by periodically forming a plurality of protrusions and a plurality of penetrations on an object, thereby utilizing local resonance induced by the protrusions and Bragg scattering generated by the periodicity of the penetrations. In addition, by destroying the periodicity of the unit pattern portion in some area of ​​the object to form a defect state, elastic wave energy is concentrated in the defect portion and converted into electric energy, thereby improving the energy harvesting performance of the energy harvesting device. As a result, by overcoming the limitations of high-performance piezoelectric energy harvesting devices that were limited to high-frequency areas, it is possible to implement energy harvesting devices even in low-frequency areas so that they can be applied in real life. As a result, by overcoming the limitations of high-performance piezoelectric energy harvesting devices that were limited to high-frequency areas, it is possible to implement energy harvesting devices even in low-frequency areas so that they can be applied in real life.

[0020] FIG. 1 is a perspective view illustrating a portion of an energy harvesting device according to one embodiment of the present invention.

[0021] Figure 2 is a plan view showing the energy harvesting device of Figure 1 as viewed from above.

[0022] FIG. 3 is a perspective view illustrating a unit pattern portion constituting an energy harvesting device according to one embodiment of the present invention.

[0023] FIG. 4 is a perspective view illustrating an energy conversion unit connected to a defective portion (P20) in an energy harvesting device according to one embodiment of the present invention.

[0024] Figure 5a is a graph showing the energy band gap in an energy harvesting device equipped only with protrusions.'

[0025] Figure 5b is a graph showing the energy band gap in an energy harvesting device equipped only with a through-hole.

[0026] FIG. 5c is a graph showing the energy band gap in an energy harvesting device according to the present invention including both protrusions and penetrations.

[0027] FIG. 6a is a drawing showing a defect band structure of an energy harvesting device according to the present invention.

[0028] FIG. 6b is a drawing showing an example of a defect mode shape of an energy harvesting device according to the present invention.

[0029] Figure 7a is an example showing an input unit connected to an energy harvesting device according to the present invention.

[0030] Figure 7b is an example showing that elastic energy is concentrated at the joint.

[0031] Figures 8a and 8b are graphs showing examples of energy conversion results in a defect section of a low-frequency band.

[0032] Figures 9a and 9b are graphs showing examples of energy conversion results in a defect section of a high-frequency band.

[0033] Hereinafter, with reference to the attached drawings, preferred embodiments will be described in detail so that those skilled in the art can easily practice the present invention. However, in describing preferred embodiments of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the same reference numerals are used throughout the drawings for parts that have similar functions and actions. In addition, in this specification, terms such as “upper,” “upper part,” “top surface,” “lower,” “lower side,” “lower surface,” and “side” are based on the drawings, and in reality, they may vary depending on the direction in which the components are arranged.

[0034] Additionally, throughout the specification, when a part is said to be "connected" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with other components intervening. Furthermore, unless specifically stated otherwise, "including" a component does not exclude other components, but rather implies the inclusion of other components.

[0035] FIG. 1 is a perspective view illustrating a portion of an energy harvesting device according to an embodiment of the present invention. FIG. 2 is a plan view illustrating the energy harvesting device of FIG. 1 as viewed from above. FIG. 3 is a perspective view illustrating a unit pattern portion constituting the energy harvesting device according to an embodiment of the present invention. In addition, FIG. 4 is a perspective view illustrating an energy conversion portion connected to a defective portion (P20) in an energy harvesting device according to an embodiment of the present invention.

[0036] Referring to FIGS. 1 to 4, the energy harvesting device (10) may include a unit pattern portion (P10) formed by including an object (100) and a protrusion (200). A plurality of such unit pattern portions (P10) may be provided. In this case, the energy harvesting device (10) may further include a defect portion (P20).

[0037] The object (100) is a part where other components of the energy harvesting device (10) are placed, and may be in the form of a thin plate.

[0038] The protrusion (200) may be placed on the object (100). The protrusion (200) may be formed to protrude in an outward direction (Z) from the upper surface of the object (100). At this time, the protrusion (200) may have various shapes. For example, the protrusion (200) may have a cylindrical shape. Meanwhile, the present invention is not limited thereto, but the following description will focus on an embodiment in which the protrusion (200) has a cylindrical shape having a first radius (R1).

[0039] The protruding length (hereinafter, protruding length) (T1) of the protrusion (200) may be different from the thickness (T2) of the object (100). For example, the protruding length (T1) of the protrusion (200) may be formed to be greater than the thickness (T2) of the object (100).

[0040] The penetration portion (300) may be a hole formed by penetrating the object (100) in one direction. Here, the one direction may be a direction parallel to the thickness direction (Z) of the penetration portion (300). The penetration portion (300) may have a cross-section of various shapes. For example, the penetration portion (300) may be in the form of a through hole having a circular cross-section. Meanwhile, although the present invention is not limited thereto, the following description will focus on an embodiment in which the penetration portion (300) is a circular hole having a second radius (R2).

[0041] As described above, in the case of a protrusion (200) having a cylindrical shape and a circular hole having a circular cross-section, the radius of the protrusion (200) (hereinafter, first radius) (R1) and the radius of the penetration (300) (hereinafter, second radius) (R2) may be the same size or similar size.

[0042] The unit pattern portion (P10) is a portion of an object (100), and within this portion, at least one protrusion (200) and at least one penetration portion (300) can be formed by arranging them in a predetermined pattern.

[0043] In one embodiment, the unit pattern portion (P10) may be arranged such that a plurality of penetration portions (300) surround a single protrusion (200). At this time, as exemplarily illustrated in FIG. 3, one unit pattern portion (P10) may be formed such that a plurality of penetration portions (300) surround a protrusion (200) disposed at the center of the unit pattern portion (P10). In this case, the unit pattern portion (P10) may have a rectangular shape with the protrusion (200) disposed at the center when viewed from above.

[0044] For example, the unit pattern portion (P10) may be in the shape of a square whose length (L1) and width (L1') are the same. In this case, the penetration portions (300) constituting the unit pattern portion (P10) may be spaced apart at equal intervals in all directions. More specifically, the interval (L2) at which the penetration portions (300) are spaced apart in the longitudinal direction (Y) and the interval (L2') at which the penetration portions (300) are spaced apart in the width direction (X) may be the same. As another example, the unit pattern portion (P10) may be in the shape of a rectangle whose length (L1) and width (L1') are different from each other. In this case, the interval (L2) at which the penetration portions (300) are spaced apart in the longitudinal direction (Y) and the interval (L2') at which the penetration portions (300) are spaced apart in the width direction (X) may be different from each other. However, for the convenience of explanation, the following description will focus on the case where the unit pattern portion (P10) is in the shape of a square.

[0045] The width (L1') and length (L1) of the unit pattern portion (P10) having a square cross-section [hereinafter referred to as the length (L1, L1') of the unit pattern portion] may be larger than the diameter of the penetration portion (300). More specifically, adjacent penetration portions (300) may be spaced apart from each other by a predetermined distance (L2, L2'). Accordingly, the length (L1, L1') of the unit pattern portion (P10) may have a size that is larger than the diameter of the penetration portion (300) by the distance (L2, L2').

[0046] A plurality of unit pattern portions (P10) may be provided. The plurality of unit pattern portions (P10) may be arranged continuously over the entire area of ​​the object (100). At this time, the number of unit pattern portions (P10) is not limited. By arranging in this manner, a protrusion pattern in which a plurality of protrusions (200) are arranged in a grid shape and a penetration pattern in which a plurality of penetration portions (300) are arranged in a grid shape between the protrusions (200) may be simultaneously formed on the object (100). Accordingly, by arranging the plurality of unit pattern portions (P10) in a grid shape, a periodicity including a protrusion pattern and a penetration pattern may be formed on the object (100).

[0047] That is, the object (100) may be a metamaterial (elastic metamaterial) in which unit pattern portions (P10) in the form of unit cells as described above are periodically formed. In addition, the object (100) is made of a material having elasticity, and thus, the object (100) may be an elastic metamaterial.

[0048] The defective portion (P20) may be arranged adjacent to some of the plurality of unit pattern portions (P10) on the above-described upper surface of the object (100). More specifically, the defective portion (P20) may be an area surrounded by some of the plurality of unit pattern portions (P10) arranged in a grid shape, and may be an area where the protrusion (200) (or the protrusion (200) and the penetration portion (300)) is not formed. Accordingly, the defective portion (P20) may be a unit area where only the object (100) formed between the plurality of unit pattern portions (P10) arranged in a grid shape exists. Such defective portions (P20) may be provided in multiple numbers, but for the convenience of explanation, the following description will focus on an example in which one defective portion (P20) is formed.

[0049] The defective portion (P20) may be formed to have the same size as the unit pattern portion (P10). An energy conversion portion (400), which will be described later, may be arranged in the defective portion (P20). By virtue of this defective portion (P20), a region (hereinafter, a defective region) in which the periodicity formed by the unit pattern portions (P10) is locally destroyed may be formed in the object (100).

[0050] The energy conversion unit (400) is composed of an energy conversion element, which may be an element that has the effect of generating voltage when deformed by stress. As described above, the energy conversion unit (400) may be placed within a defect portion (i.e., a defect region) (P20).

[0051] For example, the energy conversion unit (400) may be configured to include a piezoelectric element. In this case, the energy conversion unit (400) may be configured to include an energy conversion body (410) installed in the defect unit (P20), a pair of wire parts (420, 430) connected to the energy conversion body (410), and a power supply unit (not shown) electrically connected to the pair of wire parts (420, 430).

[0052] FIG. 5a is a graph showing the energy band gap in an energy harvesting device having only a protrusion, FIG. 5b is a graph showing the energy band gap in an energy harvesting device having only a through-hole, and FIG. 5c is a graph showing the energy band gap in an energy harvesting device according to the present invention including both a protrusion and a through-hole.

[0053] Referring to FIGS. 5A to 5C, a band gap, also called a band gap, band interval, or energy gap, refers to the energy level or energy difference between the top of the highest energy band (valence band) occupied by electrons in the band structure of a semiconductor or insulator and the bottom of the lowest space band (conduction band). This band gap is one of the representative wave singularities of an acoustic quantum crystal that does not allow waves of a specific frequency band to pass through.

[0054] At this time, a defect band may be generated within the band gap. The defect band refers to a band generated within the band gap by locally destroying the periodicity of the energy harvesting device (10) by applying a defect by replacing one of the unit pattern portions (P10) arranged to have periodicity on the object (100) with a different shape (i.e., a defect portion (P20)). When a wave with a frequency corresponding to this defect band is applied, energy can be localized by mechanical resonance of the defect, and a single defect energy harvesting portion can be formed.

[0055] Meanwhile, in the case where only a plurality of protrusions (200) are provided on the object (100) (hereinafter, Comparative Example 1), as illustrated in FIG. 5a, the protrusions (200) arranged in a lattice shape generate local resonance, thereby forming a band gap in the low-frequency band. In addition, a band gap is also formed in the high-frequency band due to Bragg scattering caused by the periodicity of the protrusions (200). However, in this case, a band gap in a very narrow frequency range is formed according to the resonance-based single-frequency operating principle, which has limitations in forming a defect state. In addition, in the case where only a plurality of penetrations (300) are provided on the object (100) (hereinafter, Comparative Example 2), as illustrated in FIG. 5b, it can be confirmed that no band gap region is formed.

[0056] In comparison, in the case where both the protrusion (200) and the penetration (300) are provided, such as in the energy harvesting device (10) according to the present invention, band gaps can be formed simultaneously in the low frequency band and the high frequency band, as illustrated in FIG. 5c. At this time, the band gap generated in the first frequency band is referred to as the first band gap (B1), and the band gap generated in the second frequency band is referred to as the second band gap (B2). In this case, the second frequency band is a high frequency band, and the first frequency band may be a lower frequency band than the second frequency band, i.e., a low frequency band.

[0057] As described above, the first band gap (B1) and the second band gap (B2) formed can be formed with a more expanded region compared to Comparative Example 1. This is due to the interaction between each band gap (B1, B2) during the formation process. For example, in the low frequency band, the first bad gap (B1) is formed with a region expanded by about 30% compared to Comparative Example 1, and in the high frequency band, the second bad gap (B2) is formed with a region expanded by about 420% compared to Comparative Example 1. In this way, since band gaps having expanded regions are formed in each of the low frequency band and the high frequency band, a defect state can be formed more easily compared to the Comparative Examples.

[0058] Meanwhile, the relationship between frequency and wavelength (i.e., the dispersion relationship), as illustrated in FIGS. 5a to 5c, can be derived by applying the Floquet-Bloch theory, which is an infinitely periodic boundary condition, to the governing elastic wave equations. This dispersion relationship is crucial for understanding the wave propagation characteristics within a medium and must be derived in advance to derive the band gap region. Once the dispersion relationship is derived, a band gap can be generated within a certain frequency range based on Bragg scattering.

[0059] Also, referring back to FIG. 5c, it can be confirmed that the slope of the graph in each frequency band where the first band gap (B1) and the second band gap (B2) are formed converges to O. At this time, the slope of the graph indicates the speed of the wave, and the convergence of this slope to O means that the speed of the wave converges to 0. Therefore, since the speed of the wave converges to 0 in both the first band gap region and the second band gap (B2) region, the elastic wave does not move and can be condensed at the defect portion (P20). In this way, due to the wave being condensed at the defect portion (P20), a larger strain field is induced in the energy conversion portion (400) composed of the piezoelectric element, thereby improving the piezoelectric energy harvesting performance.

[0060] FIG. 6a is a drawing showing a defect band structure of an energy harvesting device according to the present invention, and FIG. 6b is a drawing showing an example of a defect mode shape of an energy harvesting device according to the present invention.

[0061] Referring to FIG. 6a, when examining the defect band structure of the energy harvesting device (10) according to the present invention, as examined in FIG. 5c above, it can be confirmed that both the first band gap (B1) formed in the low frequency region and the second band gap (B2) formed in the high frequency region are formed in a defect state by the defect portion (P20).

[0062] Also, referring to FIG. 6b, when examining the defect mode shape of the energy harvesting device according to the present invention, it can be confirmed that in both defect states, elastic waves are condensed at the joint. The elastic wave energy in the form of a plane wave input to the energy harvesting device (10) is propagated via the object (100). At this time, a phenomenon occurs (band gap) in which the propagation of the elastic wave is hindered by the protrusions (200) and penetrations (300) arranged to have periodicity on the object (100). Accordingly, the elastic wave moves to the defect portion (P20), which is an area where the periodicity is destroyed on the object (100) and it is easy to propagate. In addition, the elastic wave energy propagated into the joint portion (P20) is hindered from escaping from the defect portion (P20) by the unit pattern portions (P10) formed around the joint portion (P20), and thus becomes trapped within the defect portion (P20). By the trapping and resonance phenomenon of these elastic waves, elastic wave energy can be concentrated at the defect (P20), as exemplarily illustrated in Fig. 6b.

[0063] Fig. 7a is an example showing an input portion connected to an energy harvesting device according to the present invention, and Fig. 7b is an example showing that elastic energy is concentrated at a joint.

[0064] Referring to Fig. 7a, an input unit (20) may be connected to the energy harvesting device (10) as described above. The input unit (20) may include a function generator (21), an amplifier (power amplifier) ​​(22), and a transducer (23). In this case, when an electrical signal is input to the function generator (21), the signal passes through the amplifier (22) and noise is removed, and then the signal is converted into an elastic wave by the transducer (23) and supplied to the energy harvesting device (10). Thereafter, the supplied elastic wave is condensed at the defect (P10) as described above in the process of propagating through the object (100). The condensed elastic wave energy may be converted (extracted) into electrical energy (voltage) by the energy conversion unit (400). At this time, the magnitude of the extracted voltage may be controlled by adjusting the resistance value using the resistance substituter (12) prior to the energy conversion.

[0065] Meanwhile, the energy condensed in the defect portion (P20) can be detected by a detector (11) such as a scanning LDV. Accordingly, it can be confirmed that elastic wave energy is condensed in the defect portion (P20), as exemplarily illustrated in FIG. 7b. For reference, the upper left drawing of FIG. 7b shows when the amplitude of the condensed elastic wave is maximum in the first defect mode (BM1), and the upper right drawing of FIG. 7b shows when the amplitude of the condensed elastic wave is minimum in the first defect mode (BM1). In addition, the lower left drawing of FIG. 7b shows when the amplitude of the condensed elastic wave is maximum in the second defect mode (BM2), and the lower right drawing of FIG. 7b shows when the amplitude of the condensed elastic wave is minimum in the second defect mode (BM2).

[0066] Figures 8a and 8b are graphs showing examples of energy conversion results in a defect section (P20) in a low-frequency band. And, Figures 9a and 9b are graphs showing examples of energy conversion results in a defect section (P20) in a high-frequency band.

[0067] As described above, an energy conversion unit (400) may be installed in the defective portion (P20). The energy conversion unit (400) is configured as a piezoelectric element and can convert elastic wave energy condensed in the defective portion (P20) into electrical energy. At this time, since the object (100) is formed of an elastic metamaterial having periodicity due to a lattice arrangement of protrusions (200) and penetrations (300) as described above, the energy harvesting device (10) can have superior electrical performance in both low-frequency bands and high-frequency bands compared to a case where the object (100) is not a metamaterial.

[0068] Referring to FIGS. 8a and 8b, when examining the energy conversion results at the defect portion (P20) of the low-frequency band, at the "first defect mode (BM1) frequency (e.g., 9.430 kHz in the graph)" of the low-frequency band where the first band gap (B1) is formed, it can be confirmed that the voltage measurement value (e.g., 1.37 V in the graph) and the maximum power value (e.g., 24.4 μW in the graph) converted and converged by the energy conversion portion (400) are increased by approximately 190% compared to the case where the elastic metamaterial is not used.

[0069] In addition, referring to FIGS. 9a and 9b, when examining the energy conversion results at the defect portion (P20) of the high-frequency band, when examining the energy conversion results at the defect portion (P20) of the high-frequency band, at the "second defect mode (BM2) frequency (e.g., 47.187 kHz in the graph)" of the high-frequency band where the second band gap (B2) is formed, it can be confirmed that the voltage measurement value (e.g., 4.05 V in the graph) and the maximum power value (e.g., 1.28 mW in the graph) converted and converged by the energy conversion portion (400) are increased by about 400% compared to the case where the elastic metamaterial is not used.

[0070] As described above, the energy harvesting device (10) according to embodiments of the present invention can form a band gap having an extended area simultaneously in a low-frequency band and a high-frequency band by periodically forming a plurality of protrusions (200) and a plurality of penetrations (300) on an object (100), thereby utilizing local resonance induced by the protrusions (200) and Bragg scattering generated by the periodicity of the penetrations (300). In addition, in some areas of the object (100), the periodicity of the unit pattern portion (P10) is destroyed to form a defect state, thereby condensing elastic wave energy in the defect portion (P20) and converting it into electric energy, thereby improving the energy harvesting performance of the energy harvesting device (10). As a result, by overcoming the limitations of high-performance piezoelectric energy harvesting devices that were limited to a high-frequency range, it is possible to implement the energy harvesting device (10) even in a low-frequency range so that it can be applied in real life.

[0071] Although the embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

[0072] The present invention can be applied to an industrially usable energy harvesting device.

Claims

1. Object; A unit pattern portion formed on the object and including a protrusion formed in one direction protruding from the surface of the object and a penetration portion formed by penetrating the object along the one direction, the unit pattern portion being provided in multiple numbers and periodically arranged on the object; A defect portion disposed on the above object and formed at a position adjacent to some of the plurality of unit pattern portions; and An energy harvesting device, comprising: an energy conversion unit disposed in the above-mentioned defective portion.

2. In paragraph 1, The above unit pattern part is, An energy harvesting device having a plurality of penetrations surrounding the protrusion but spaced apart from each other, centered on the protrusion.

3. In paragraph 2, An energy harvesting device, wherein a plurality of the above unit pattern sections are arranged in a grid shape on the object.

4. In paragraph 1, An energy harvesting device, wherein the above-mentioned defective portion is an area surrounded by a plurality of the above-mentioned unit pattern portions, but in which the above-mentioned protrusion is not formed.

5. In paragraph 2, An energy harvesting device, wherein, in the above-described defective portion, a first band gap is generated in a first frequency band by local resonance induced by the protrusion, and a second band gap is generated in a second frequency band by the periodicity of the penetration portion.

6. In paragraph 5, An energy harvesting device, wherein the second frequency band is a higher frequency band than the first frequency band.

7. In paragraph 5, An energy harvesting device, wherein the first band gap and the second band gap are generated simultaneously.

8. In paragraph 5, An energy harvesting device, wherein, when a band gap is generated, an area of ​​the first band gap and an area of ​​the second band gap are expanded due to the interaction between the protrusion and the penetration.

9. In paragraph 1, The above protrusion is in the shape of a cylinder. An energy harvesting device, wherein the above-mentioned penetration portion is in the form of a penetration hole having a circular cross-section.

10. In paragraph 9, An energy harvesting device, wherein the protrusion and the penetration have the same diameter.

11. In paragraph 1, An energy harvesting device, wherein the energy conversion unit includes a piezoelectric element.

12. In paragraph 1, The above object is an energy harvesting device which is an elastic metamaterial.

Images