A reflected sound beam adjusting unit based on PVDF / PI piezoelectric beam

Abstract

The application discloses a reflection sound beam adjusting unit based on a PVDF / PI piezoelectric beam, which comprises at least five identical PVDF / PI piezoelectric beams and a cavity made of 3D printing resin material, the piezoelectric beams are inserted into the cavity, and the upper and lower surfaces of the piezoelectric beams are in the shape of arc curved surfaces, each piezoelectric beam is made of a PVDF piezoelectric layer and a PI layer which are bonded and are double-sidedly plated with aluminum electrodes, the cavity is in the structure that the top is open and the four walls and the bottom are closed, the piezoelectric beams are inserted and installed on the inner walls of two sides of the cavity, the bending directions of the piezoelectric beams on the same side are consistent, and the bending directions of the piezoelectric beams on the two sides are opposite; meanwhile, from the top opening of the cavity downwards, the bending direction of the first piezoelectric beam is downward, and the insertion installation points of the piezoelectric beams below are sequentially and pairwise located on the same plane. The application has wide application scenarios, the structure is directly controlled by voltage without additional mechanical or pressure transmission devices, does not need complex circuits, and can realize 2pi range of reflection sound beam phase operation in theory.

Description

Technical Field

[0001] The invention relates to a reflected sound beam adjustment unit based on a PVDF / PI piezoelectric beam, belonging to the field of sound beam phase control. Background Art

[0002] Acoustic metasurfaces have garnered widespread attention in recent years due to their excellent controllability and promising practical applications. These structures, in particular, feature adjustable structural parameters that can adapt to diverse application scenarios. Recently, actively tunable acoustic metasurface units have emerged in large numbers, and the search for easily controllable, fully functional acoustic structures has become a hot topic among researchers.

[0003] Traditional acoustic phase control units utilize Helmholtz resonators, folded structures, and curled structures to achieve phase control through resonance or altering the acoustic path. Tunable metasurfaces utilize methods such as mechanical rotation or filling a cavity with liquid to change the acoustic capacitance, or introduce piezoelectric materials to change the acoustic impedance through external capacitors, thereby achieving adjustable phase control of a single unit.

[0004] However, although mechanical rotation or filling liquid in the cavity can adjust the phase of reflected or transmitted sound, the means are complicated and the control is inconvenient; the method of external circuit components requires careful design of component parameters and circuit design, and the control is complicated and time-consuming. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention starts from the design of an acoustically adjustable metasurface unit, combines the cavity with the piezoelectric beam, and proposes a sub-wavelength reflection sound beam adjustment unit that can be controlled by voltage.

[0006] The technical solution adopted by the present invention is: a reflected sound beam adjustment unit based on PVDF / PI piezoelectric beams, which includes at least five identical PVDF / PI piezoelectric beams and a cavity made of 3D printed resin material. The piezoelectric beams are inserted into the cavity, and the upper and lower surfaces of the piezoelectric beams are arc-shaped. Each piezoelectric beam is made of a PVDF piezoelectric layer with aluminum electrodes on both sides and a PI layer bonded together.

[0007] As a further preferred embodiment of this solution, the cavity is a structure that is closed on all sides and at the bottom and open at the top, and the top opening serves as an entrance for the sound beam.

[0008] As a further preferred embodiment of this solution, the piezoelectric beams are inserted and installed on the inner walls on both sides of the cavity, and the bending directions of the piezoelectric beams on the same side remain consistent, while the bending directions of the piezoelectric beams on both sides are opposite.

[0009] As a further preferred embodiment of the present invention, from the top opening of the cavity downward, the bending direction of the first piezoelectric beam is downward; and the insertion and installation points of the piezoelectric beams thereunder are located in pairs on the same plane.

[0010] As a further preferred embodiment of this solution, the distance between the piezoelectric beams on the same side is: d=20 mm.

[0011] As a further preferred embodiment of this solution, the thickness of the PVDF piezoelectric layer and the PI layer ranges from 50 to 100 microns; a 50-micron thick PVDF piezoelectric layer and a 50-micron thick PI tape are usually selected.

[0012] As a further preferred embodiment of this solution, the total length of the piezoelectric beam is 18 mm, and each piezoelectric beam is pre-bent to have the same curvature; the pre-bent curvature radius is: r=20 mm.

[0013] As a further preferred embodiment of this solution, the side length of the inner wall of the cavity is: a=20 mm, and the wall thickness of the cavity is: t=6 mm.

[0014] As a further optimization of this solution, when all piezoelectric beams are connected in parallel and the same voltage is applied, the PVDF layer will stretch or shrink due to the inverse piezoelectric effect, while the length of the PI layer remains unchanged. Therefore, the curvature of the piezoelectric beam will change with the voltage, thereby affecting the equivalent acoustic refractive index of the entire structure, causing the reflected sound phase to change accordingly, thereby achieving the effect of sound beam adjustment. The relationship between the voltage V and the curvature radius r of the piezoelectric beam is as follows:

[0015]

[0016] t1 and t2 are the thicknesses of the PVDF layer and the PI layer, E1 and E2 are the Young’s moduli of PVDF and PI, d31 is the piezoelectric coefficient of the PVDF layer, and ε is the deformation of the PVDF layer.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The structure proposed in the present invention does not require additional mechanical or pressure transmission devices, and is directly voltage-controlled. It does not require complex circuits and can theoretically achieve phase manipulation of the reflected sound beam within a 2π range.

[0019] (2) It has a wide range of application scenarios. This structure can be arranged into a metasurface according to the needs of different scenarios to achieve acoustic functions such as reflected sound deflection and focusing.

[0020] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Middle: (a) is a schematic diagram of the metasurface composed of the regulation unit; (b) is a schematic diagram of the structure of the regulation unit; (c) is a schematic diagram of the PVDF / PI piezoelectric beam structure.

[0022] Figure 2 Middle: (a) is the simulation diagram of the reflected sound field of the adjustment unit, and the black dot is the domain point probe; (b) is the curve diagram of the reflected sound phase of the adjustment unit changing with the curvature radius r of the piezoelectric beam; (c) is the simulation diagram of the focused sound field with a focal length of 60 mm; (d) is the distribution diagram of the square of the sound pressure modulus on the cross-section at y = 60 mm; (e) is the simulation effect diagram of the reflected sound deflection; (f) is the simulation effect diagram of converting the incident sound field into a surface wave.

[0023] Figure 3 Middle: (a) is a schematic diagram of the experimental measurement setup; (b) is the relationship between the normalized reflected sound phase and the voltage, where the gray line represents the voltage phase change and the black dots represent the reflected sound phase offset at the corresponding moment. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, a reflected sound beam adjustment unit based on PVDF / PI piezoelectric beams includes five identical PVDF / PI piezoelectric beams and a cavity made of 3D printed resin material. The piezoelectric beams are inserted into the cavity, and the upper and lower surfaces of the piezoelectric beams are curved. Each piezoelectric beam is made of a 50-micron-thick PVDF piezoelectric layer with aluminum electrodes on both sides and a 50-micron-thick PI tape. The cavity is a structure that is closed on all sides and the bottom and open on the top. The top opening serves as the sound beam entrance. The piezoelectric beams are inserted and installed on the inner walls of both sides of the cavity, three on one side and two on the other opposite side. The bending directions of the piezoelectric beams on the same side remain consistent, while the bending directions of the piezoelectric beams on both sides are opposite. At the same time, from the top opening of the cavity downward, the bending direction of the first piezoelectric beam is downward, and the insertion and installation points of the piezoelectric beams below it are located in the same plane in pairs.

[0026] When in use, all piezoelectric beams are connected in parallel and the same voltage is applied. The PVDF layer will stretch or shrink due to the inverse piezoelectric effect, while the length of the PI layer remains unchanged. Therefore, the curvature of the piezoelectric beam will change with the voltage, thereby affecting the equivalent acoustic refractive index of the entire structure, causing the reflected sound phase to change accordingly, thereby achieving the effect of sound beam adjustment. Figure 1 A structural diagram is shown, and the structural parameters in the figure are as follows:

[0027] The side length of the cavity wall: a = 20 mm;

[0028] Cavity wall thickness: t = 6 mm;

[0029] The distance between the piezoelectric beams on the same side: d = 20 mm;

[0030] Pre-bending curvature radius: r = 20 mm.

[0031] Figure 2 The reflected sound control capability of the present invention is demonstrated. Figure 2 Figure (a) is a model that simulates the acoustic reflection capability of the control unit. The incident sound pressure is set to 1 Pa, the frequency is 1500 Hz, and the incidence is vertical. A domain point probe is used to detect the reflected sound phase. The results are shown in Figure (b), indicating that the unit can theoretically achieve an acoustic phase shift in the range of 2π. The metasurface composed of this unit has the ability to manipulate the wavefront arbitrarily. Figure 2 (c), (e), and (f) respectively demonstrate the three functions achieved by the metasurface in the simulation, namely, focusing, deflecting, and converting vertically incident sound waves into surface waves. When the phase distribution of the metasurface unit satisfies:

[0032]

[0033] When , the sound energy of the reflected sound field will be concentrated at the point (0,F); Figure 2 (c) shows the case when the sound wave with a frequency of 1500Hz is incident vertically and F = 60mm. The sound energy at the focus is 9.6 times the incident sound energy, showing a good focusing effect. When the phase distribution of the metasurface unit satisfies:

[0034]

[0035] When the reflected sound field is θ r Abnormal angle reflex; Figure 2 (e) shows the case when the sound wave with a frequency of 1500 Hz is incident vertically and dφ(x) = π / 6. The direction of the reflected sound is θ r =36.55° is marked with a black arrow. r =90°, the reflected sound appears in the form of surface waves, and the sound energy is only near the metasurface and decays rapidly in the y direction, such as Figure 2 (f) shown.

[0036] Figure 3 The experimental results demonstrate that the modulation unit has the ability to control the phase of the reflected sound, which changes in real time with the sound pressure at both ends of the piezoelectric beam. The relationship between the voltage V and the curvature radius r of the piezoelectric beam is as follows:

[0037]

[0038] t1 and t2 are the thicknesses of the PVDF layer and the PI layer, E1 and E2 are the Young’s moduli of PVDF and PI, d31 is the piezoelectric coefficient of the PVDF layer, and ε is the deformation of the PVDF layer.

[0039] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the scope of protection of the present invention in any form, and all technical solutions obtained by equivalent replacement and other methods fall within the scope of protection of the present invention.

[0040] The parts not involved in the present invention are the same as the existing technology or can be implemented by using the existing technology.

Claims

1. A reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam, characterized in that: It includes at least five identical PVDF / PI piezoelectric beams and a cavity made of 3D printed resin material. The piezoelectric beams are inserted into the cavity, and the upper and lower surfaces of the piezoelectric beams are curved surfaces. Each piezoelectric beam is made of a PVDF piezoelectric layer with aluminum electrodes on both sides and a PI layer bonded together.

2. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 1, characterized in that: The cavity is a structure with its periphery and bottom closed and its top open, and the top opening serves as an entrance for the sound beam.

3. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 2, characterized in that: The piezoelectric beams are inserted and mounted on the inner walls of both sides of the cavity, and the bending directions of the piezoelectric beams on the same side remain consistent, while the bending directions of the piezoelectric beams on both sides are opposite.

4. A reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 2 or 3, characterized in that: From the top opening of the cavity downward, the bending direction of the first piezoelectric beam is downward; the insertion and installation points of the piezoelectric beams below it are located in pairs on the same plane.

5. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 3, characterized in that: The distance between the piezoelectric beams on the same side is: d = 20 mm.

6. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 1, characterized in that: The thickness of the PVDF piezoelectric layer and the PI layer ranges from 50 to 100 microns.

7. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 1, characterized in that: The total length of the piezoelectric beams is 18 mm, and each piezoelectric beam is pre-bent into the same curvature.

8. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 7, characterized in that: The curvature radius of the pre-bend is: r=20mm.

9. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 1, characterized in that: The side length of the inner wall of the cavity is: a=20 mm, and the wall thickness of the cavity is: t=6 mm.

10. The reflected sound beam adjustment unit based on PVDF / PI piezoelectric beam according to claim 1, characterized in that: When in use, all piezoelectric beams are connected in parallel and the same voltage is applied. The PVDF layer stretches or contracts, while the length of the PI layer remains unchanged. The relationship between the voltage V and the curvature radius r of the piezoelectric beam is as follows: t1 and t2 are the thicknesses of the PVDF layer and the PI layer, E1 and E2 are the Young’s moduli of PVDF and PI, d31 is the piezoelectric coefficient of the PVDF layer, and ε is the deformation of the PVDF layer.

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