A gold foil graphene composite diaphragm multi-eigenvalue pickup

Abstract

The application relates to a gold foil graphene composite diaphragm multi-eigenvalue pickup, and belongs to the technical field of diaphragm preparation. The gold foil graphene composite diaphragm multi-eigenvalue pickup is used for solving the problems that the existing diaphragm is not designed according to the vibration frequency, the signal-to-noise ratio is low, the diaphragm is relatively thick, the diaphragm cannot be applied to a micro pickup, and the preparation method limits the size of the diaphragm. The gold foil graphene composite diaphragm multi-eigenvalue pickup comprises the following steps: gold foil graphene diaphragm is attached to the top of the internal cavity of a glass support, an optical fiber is inserted into the hole at the bottom of the glass support, and the internal cavity of the glass support constitutes an F-P resonant cavity; different eigenvalues of the gold foil graphene diaphragm are obtained by adjusting the parameters of the gold foil graphene diaphragm, the parameters include a wrinkle state, a thickness, a diameter and a gold foil area, and then the eigenvalues of the gold foil graphene diaphragm are regulated so that the resonance frequency of the gold foil graphene diaphragm matches the characteristic frequency of a target to be identified. The gold foil graphene composite diaphragm is prepared, and the resonance frequency is regulated through the parameters of graphene so that the resonance frequency matches the characteristic frequency of a target to be identified.

Description

Technical Field

[0001] The invention relates to a multi-eigenvalue pickup prepared by adopting a gold foil and graphene composite diaphragm, belonging to the technical field of diaphragm preparation. Background Art

[0002] A microphone is a device that is widely used in various fields such as aerospace, electronic equipment, etc. to collect sound vibrations. The important component of the microphone is the diaphragm.

[0003] The diaphragm is a component that is very sensitive to changes in the magnetic field. When the electrical signal passes through the coil, the magnetic field changes, causing the diaphragm to deform under stress. The existing diaphragm technologies mainly include:

[0004] Patents with publication number CN211047203U, titled "Diaphragm, Speaker, and Headphones," and patents with publication number CN112399312A, titled "Diaphragm, Speaker, and Diaphragm Manufacturing Method," disclose a method for manufacturing a diaphragm, including a four-layer composite diaphragm that can better maximize the high-frequency ductility of the diaphragm while also taking into account both high- and low-pitched sound effects. However, the actual thickness of the diaphragm is relatively large, making it unsuitable for use as a diaphragm for a micro-acoustic pickup.

[0005] Patent publication number CN106060722A, titled "Graphene Diaphragm, Diaphragm Manufacturing Method, and Microphone Including the Diaphragm," proposes a graphene material microphone diaphragm and a method for manufacturing the diaphragm, comprising a metal nickel ring having a protruding structure, and a graphene film integrated with one side of the metal nickel ring having the protruding structure, wherein the protruding structure protrudes from the graphene film. The diaphragm structure is obtained by providing a metal nickel sheet, and disposing a plurality of protruding structures on the outer peripheral portion of one surface of the metal nickel sheet. A graphene film is grown on the surface of a metal nickel sheet with a protruding structure, the protruding structure protrudes from the film surface, and the middle part of the metal nickel sheet is removed by etching to obtain a metal nickel ring with a protruding structure. The metal nickel ring is combined with the graphene film as a whole to obtain a graphene diaphragm. A condenser microphone including the graphene material diaphragm is further proposed. The graphene material diaphragm in this patent has a firm structure, and the sensitivity, frequency response, transient response and other electroacoustic characteristics of the microphone with the graphene diaphragm are greatly improved.

[0006] Patent publication number CN106131755A, entitled "Microphone with Graphene Diaphragm," proposes a condenser microphone with a graphene diaphragm. The device comprises a graphene diaphragm and a back plate with through-holes. The diaphragm and back plate are separated by an insulating ring and a gap. The diaphragm and back plate are connected to power supply and amplification components via conductive components, forming a capacitor. Different power supply methods are used to achieve microphone functionality based on the different spacing between the diaphragm and back plate that form the capacitor structure. This addresses the technical issue of ensuring the proper operation of a microphone with a graphene diaphragm. The microphone described in this patent significantly improves electroacoustic characteristics such as sensitivity, frequency response, and transient response compared to traditional condenser microphones.

[0007] However, the diaphragm sound sensor in the above patent document has the following problems:

[0008] 1. All designs are based on the principle, and the main purpose is only to improve the sensitivity of the pickup diaphragm. There is no corresponding design and explanation of the vibration frequency of the diaphragm, and the signal-to-noise ratio of the diaphragm is also relatively low;

[0009] 2. The multi-layer composite diaphragm mainly focuses on the high-frequency ductility of the diaphragm, while taking into account the effectiveness of treble and bass. However, the actual thickness of the diaphragm is relatively large and cannot be used in micro pickups.

[0010] 3. Since graphene films have defects of varying degrees during the preparation process, the success rate of preparing graphene diaphragms will gradually decrease as the area of ​​graphene films used gradually expands. Summary of the Invention

[0011] The purpose of the present invention is to solve the problems that the existing diaphragm is not designed for vibration frequency, has a low signal-to-noise ratio, is relatively thick and cannot be used in micro pickups, and the limitations of the preparation method lead to a small diaphragm size. A gold foil graphene composite diaphragm multi-eigenvalue pickup is provided.

[0012] The present invention discloses a gold foil graphene composite diaphragm multi-eigenvalue pickup, which comprises: a gold foil graphene diaphragm, a glass support, and an optical fiber. The glass support is a rectangular parallelepiped with a hole at the bottom and a cavity inside.

[0013] The gold foil graphene diaphragm is attached to the top of the cavity inside the glass support, and the optical fiber is inserted into the hole at the bottom of the glass support. The cavity inside the glass support constitutes the FP resonant cavity;

[0014] Gold foil graphene diaphragms with different eigenvalues ​​are obtained by adjusting the parameters of the gold foil graphene diaphragm, wherein the eigenvalues ​​are equidistant. The parameters include wrinkle state, thickness, diameter and gold foil area.

[0015] Then, by adjusting the eigenvalue of the gold foil graphene diaphragm, the resonant frequency of the gold foil graphene diaphragm is matched with the characteristic frequency of the target to be identified.

[0016] Preferably, the specific process of obtaining gold foil graphene diaphragms with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm and then regulating the resonant frequency of the gold foil graphene diaphragm includes:

[0017] The fewer wrinkles the gold foil graphene diaphragm has, the higher the resonant frequency is, and the more wrinkles the gold foil graphene diaphragm has, the lower the resonant frequency is.

[0018] The resonant frequency is inversely proportional to the square root of the thickness of the gold foil graphene diaphragm.

[0019] Preferably, the length of the FP resonant cavity is a length that makes the contrast of the interference fringes 1.

[0020] Preferably, the diameter of the gold foil graphene diaphragm is 2 to 20 mm, and the number of layers is 20 to 30.

[0021] Preferably, the gold foil graphene diaphragm is prepared by an inverted suspension method, the specific process of which includes:

[0022] S1, transferring graphene coated with PMMA protective film to the surface of silicon wafer substrate;

[0023] S2. Wetting the surface of the PMMA protective film with anhydrous ethanol, placing the graphene and silicon wafer substrate soaked with the PMMA protective film in a quartz tank, with the surface soaked with the PMMA protective film facing downward;

[0024] S3, pass acetone into the quartz tank for 3 minutes;

[0025] S4. Lift one side of the quartz tank to allow acetone to flow out of the quartz tank, thereby obtaining a graphene diaphragm structure;

[0026] S5. Place the prepared graphene diaphragm structure in air to dry for 1 minute;

[0027] S6. Suspending a gold foil with a thickness of 12 nm on the surface of the graphene diaphragm structure, and adsorbing the gold foil on the surface of the graphene diaphragm structure through intermolecular forces to obtain a gold foil graphene diaphragm.

[0028] Preferably, the wrinkle state of the gold foil graphene diaphragm is controlled by the flow rate and flow velocity of the acetone entering the quartz tank in S3, the flow velocity of the acetone flowing out of the quartz tank in S4, and the lifting angle of the quartz tank.

[0029] Preferably, in S3, acetone is introduced into the quartz tank by a peristaltic pump; and the flow rate and flow velocity of the acetone introduced into the quartz tank are controlled by the peristaltic pump.

[0030] Preferably, the specific method of obtaining gold foil graphene diaphragms with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm, and then matching the resonant frequency of the gold foil graphene diaphragm with the characteristic frequency of the target to be identified by regulating the eigenvalue of the gold foil graphene diaphragm includes:

[0031] The sound pressure P on the surface of the gold foil graphene diaphragm is:

[0032] P=P a e jwt ;

[0033] Among them, P a represents the amplitude of the sound pressure, e represents the natural base, j represents the imaginary unit, w represents the circular frequency of the sound wave, and t represents time;

[0034] External force F on the surface element dxdy F For: F F =Pdxdy;

[0035] Substituting into the membrane vibration equation, we obtain the forced vibration equation of the circular membrane:

[0036]

[0037] Among them, r represents the radial distance of the pole, that is, the polar diameter, η represents the equilibrium direction distance of a point on the membrane from the equilibrium position, that is, the deflection, θ represents the angle between the polar diameter and the polar axis, and c represents a constant. represents partial derivative;

[0038] The solution is:

[0039] η(t,r)=η a e jwt

[0040]

[0041] Among them, η(t,r) represents the distance in the equilibrium direction from the equilibrium position of a point on the membrane as a function of time t and polar radius r, η a represents the amplitude of displacement, k represents a constant, k = 2πf / c, f represents the sound frequency, T represents the membrane tension, unit is N / m, a represents the membrane radius, J0(kr) represents the change of the value of the zero-order Bessel function J0 with the value of r, where r = 0, J0(kr) = 1, indicating that the amplitude of the circular membrane center is the largest, J0(ka) represents the change of the value of the zero-order Bessel function J0 with the value of the membrane radius a;

[0042] The amplitude of displacement η a Taking the average, we get:

[0043]

[0044] J2(ka) represents the change of the value of the second-order Bessel function J2 with the value of the membrane radius a;

[0045] Then the resonant frequency of the gold foil graphene diaphragm (1) is obtained

[0046] Among them, μ n represents the n roots of the zero-order Bessel function, and λ represents the resonant frequency f m The proportionality coefficient with the root value of the zero-order Bessel function;

[0047] The root value of the zero-order Bessel function J0 is directly proportional to the characteristic frequency of the target to be identified.

[0048] Preferably, the bottom of the glass support is further provided with four ventilation holes, which are distributed around the hole for inserting the optical fiber.

[0049] The gold foil graphene composite diaphragm multi-eigenvalue pickup proposed in the present invention has the following advantages:

[0050] 1. The resonant frequency is controlled by adjusting parameters such as the number of graphene layers in the gold foil graphene composite diaphragm, the wrinkles on the graphene diaphragm surface, the thickness of the graphene diaphragm, and the area of ​​the gold foil. This allows the resonant frequency to match the characteristic frequency of the target to be identified, enabling the multi-eigenvalue pickup to detect multiple characteristic frequencies simultaneously. In particular, the use of eigenvalue frequency resonance can realize the detection of tiny signals.

[0051] 2. Use the inverted suspension method to prepare the gold foil graphene composite diaphragm, expand the diameter of the gold foil graphene composite diaphragm to 20mm, and increase the thickness of the graphene diaphragm to 20-30 layers;

[0052] 3. A gold foil layer is compounded on the basis of the graphene composite diaphragm through van der Waals force to increase the reflection;

[0053] 4. The demodulation has a high signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the structure of a gold foil graphene composite diaphragm multi-eigenvalue pickup according to the present invention, wherein A represents incident light;

[0055] Figure 2 is a schematic diagram of the glass support member of the present invention;

[0056] Figure 3 Schematic diagram of the structure of the gold foil graphene diaphragm of the present invention;

[0057] Figure 4This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 50 Hz. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0058] Figure 5 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 63 Hz. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0059] Figure 6 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at an 80 Hz signal frequency. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0060] Figure 7 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 100 Hz. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0061] Figure 8 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 125 Hz. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0062] Figure 9 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 160 Hz. The horizontal axis represents frequency, the vertical axis represents signal-to-noise ratio, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0063] Figure 10 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 50 Hz. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0064] Figure 11 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 63 Hz. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0065] Figure 12This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at an 80 Hz signal frequency. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0066] Figure 13 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 100 Hz. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0067] Figure 14 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 125 Hz. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0068] Figure 15 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 160 Hz. The horizontal axis represents time, the vertical axis represents the time domain signal, curve a represents the gold foil graphene diaphragm pickup, and curve b represents the standard microphone.

[0069] Figure 16 is the experimental and theoretical simulation curves of the graphene resonance frequency, where curve c represents the experimental value and curve d represents the theoretical value; DETAILED DESCRIPTION

[0070] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0071] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0072] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0073] Example 1:

[0074] The following combination Figure 1-Figure 3 This embodiment describes a gold foil graphene composite diaphragm multi-eigenvalue pickup, which includes: a gold foil graphene diaphragm 1, a glass support 2, and an optical fiber 3. The glass support 2 is a rectangular parallelepiped with a hole at the bottom and a cavity inside.

[0075] The gold foil graphene diaphragm 1 is attached to the top of the cavity inside the glass support 2, and the optical fiber 3 is inserted into the hole at the bottom of the glass support 2. The cavity inside the glass support 2 constitutes the FP resonant cavity 4;

[0076] By adjusting the parameters of the gold foil graphene diaphragm 1, gold foil graphene diaphragms 1 with different eigenvalues ​​are obtained, and the eigenvalues ​​are equidistant. The parameters include wrinkle state, thickness, diameter and gold foil area.

[0077] Then, by adjusting the eigenvalue of the gold foil graphene diaphragm 1, the resonant frequency of the gold foil graphene diaphragm 1 is matched with the characteristic frequency of the target to be identified.

[0078] Furthermore, four ventilation holes are formed on the bottom of the glass support 2 , and the four ventilation holes are distributed around the hole where the optical fiber 3 is inserted.

[0079] Furthermore, the specific process of obtaining gold foil graphene diaphragms 1 with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm 1 and then regulating the resonant frequency of the gold foil graphene diaphragm 1 includes:

[0080] The fewer wrinkles the gold foil graphene diaphragm 1 has, the higher the resonance frequency; the more wrinkles the gold foil graphene diaphragm 1 has, the lower the resonance frequency.

[0081] The resonant frequency is inversely proportional to the first power of half the thickness of the gold foil graphene diaphragm 1 .

[0082] Furthermore, the length of the FP resonant cavity 4 is a length that makes the contrast of the interference fringes 1.

[0083] Furthermore, the diameter of the gold foil graphene diaphragm 1 is 2 to 20 mm, and the number of layers is 20 to 30.

[0084] Furthermore, the gold foil graphene diaphragm 1 is prepared by an inverted hanging method, and the specific process includes:

[0085] S1, transferring graphene coated with PMMA protective film to the surface of silicon wafer substrate;

[0086] S2. Wetting the surface of the PMMA protective film with anhydrous ethanol, placing the graphene and silicon wafer substrate soaked with the PMMA protective film in a quartz tank, with the surface soaked with the PMMA protective film facing downward;

[0087] S3, pass acetone into the quartz tank for 3 minutes;

[0088] S4. Lift one side of the quartz tank to allow acetone to flow out of the quartz tank, thereby obtaining a graphene diaphragm structure;

[0089] S5. Place the prepared graphene diaphragm structure in air to dry for 1 minute;

[0090] S6. Suspending a gold foil with a thickness of 12 nm on the surface of the graphene diaphragm structure, and adsorbing the gold foil on the surface of the graphene diaphragm structure through intermolecular forces, thereby obtaining a gold foil graphene diaphragm 1.

[0091] Furthermore, the wrinkle state of the gold foil graphene diaphragm 1 is controlled by the flow rate and flow velocity of the acetone entering the quartz tank in S3, the flow velocity of the acetone flowing out of the quartz tank in S4, and the lifting angle of the quartz tank.

[0092] Furthermore, in S3, acetone is introduced into the quartz tank through a peristaltic pump; the flow rate and flow velocity of the acetone introduced into the quartz tank are controlled by the peristaltic pump.

[0093] Furthermore, the specific method of obtaining gold foil graphene diaphragms 1 with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm 1 and then matching the resonant frequency of the gold foil graphene diaphragm 1 with the characteristic frequency of the target to be identified by regulating the eigenvalue of the gold foil graphene diaphragm 1 includes:

[0094] The sound pressure P on the surface of the gold foil graphene diaphragm 1 is:

[0095] P=P a e jwt ;

[0096] Among them, P a represents the amplitude of the sound pressure, e represents the natural base, j represents the imaginary unit, w represents the circular frequency of the sound wave, and t represents time;

[0097] External force F on the surface element dxdy F For: F F =Pdxdy;

[0098] Substituting into the membrane vibration equation, we obtain the forced vibration equation of the circular membrane:

[0099]

[0100] Among them, r represents the radial distance of the pole, that is, the polar diameter, η represents the equilibrium direction distance of a point on the membrane from the equilibrium position, that is, the deflection, θ represents the angle between the polar diameter and the polar axis, and c represents a constant. represents partial derivative;

[0101] The solution is:

[0102] η(t,r)=η a e jwt

[0103]

[0104] Among them, η(t,r) represents the distance in the equilibrium direction from the equilibrium position of a point on the membrane as a function of time t and polar radius r, η a represents the amplitude of displacement, k represents a constant, k = 2πf / c, f represents the sound frequency, T represents the membrane tension, unit is N / m, a represents the membrane radius, J0(kr) represents the change of the value of the zero-order Bessel function J0 with the value of r, where r = 0, J0(kr) = 1, indicating that the amplitude of the circular membrane center is the largest, J0(ka) represents the change of the value of the zero-order Bessel function J0 with the value of the membrane radius a;

[0105] The amplitude of displacement η a Taking the average, we get:

[0106]

[0107] J2(ka) represents the change of the value of the second-order Bessel function J2 with the value of the membrane radius a;

[0108] Then the resonant frequency of the gold foil graphene diaphragm 1 is obtained

[0109] Among them, μ n represents the n roots of the zero-order Bessel function, and λ represents the resonant frequency f m The proportionality coefficient with the root value of the zero-order Bessel function;

[0110] The root value of the zero-order Bessel function J0 is directly proportional to the characteristic frequency of the target to be identified.

[0111] In this embodiment, the zero-order cylindrical Bessel function J0(z) has n roots, and μ n express:

[0112]

[0113] The resonant frequency f of the graphene diaphragm m and the root value X of the zero-order cylindrical Bessel function J0(z) n By comparing the experimental values ​​with the theoretical values, the experimental values ​​and theoretical values ​​of the n-th order resonance frequency of the graphene diaphragm have similar change trends, such as Figure 16 As shown, curve c represents the experimental value, and curve d represents the theoretical value.

[0114] In the present invention, the extrinsic Fabry-Perot Interfermoter (EFPI) fiber optic sensor structure is not limited by the optical fiber itself. It can realize the sensing and simultaneous measurement of multiple parameters such as biological, pressure, acceleration, strain, vibration, displacement, liquid level, temperature, refractive index, humidity, etc. according to different mechanisms, greatly expanding the application field of fiber optic sensing technology; EFPI fiber optic sensor is also the most promising FP cavity structure for miniaturization.

[0115] The present invention proposes a "short cavity long coaxial type" fiber optic microphone structure. The typical structure of the coaxial EFPI microphone is as follows Figure 1 As shown, the diaphragm is a 30-layer graphene film structure with a diameter of 15 mm. A polished optical fiber encapsulated with an SC ceramic ferrule is inserted into a glass sleeve bonded with a graphene film. A five-axis precision translation stage is used to control the FP cavity length, and an optical spectrum analyzer is used to monitor the FP cavity's reflection spectrum. Once the desired FP cavity length is achieved, the probe is encapsulated using a two-component curing adhesive. Generally, a demodulation result with a contrast of 1 for the interference fringes yields the highest signal-to-noise ratio.

[0116] In the present invention, the outer frame of the silicon wafer substrate is a square silicon wafer with a size of 25mm*25mm and a through hole diameter of 15mm. The quartz cavity and the gold foil / graphene composite diaphragm made according to the size of the silicon wafer substrate are as follows: Figure 2 and Figure 3 As shown, Figure 2 is a schematic diagram of the quartz cavity. Figure 3 This diagram shows a gold foil / graphene composite diaphragm, with the gold foil side facing downward, firmly attached to a quartz cavity. Comparative testing was conducted between the gold foil / graphene composite diaphragm EFPI fiber optic microphone and a standard microphone. Acoustic testing and sensor signal demodulation were performed, and the sound pickup performance of the two microphones was evaluated using signal-to-noise ratio and time-domain signals.

[0117] The EFPI fiber optic microphone made of the gold foil graphene diaphragm proposed in this invention was compared with a standard microphone, and acoustic experimental tests and sensor signal demodulation were carried out. The sound collection effects of the two microphones were evaluated by signal-to-noise ratio and time domain signal. Figure 4-Figure 9 As shown, Figure 4 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a 50HZ signal frequency. Figure 5 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 63HZ. Figure 6 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at 80HZ signal frequency. Figure 7This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 100HZ. Figure 8 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 125HZ. Figure 9 This is a comparison chart of the signal-to-noise ratio of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 160HZ. At different frequency signals of 50HZ, 63HZ, 80HZ, 100HZ, 125HZ, and 160HZ, the signal-to-noise ratio of the gold foil graphene diaphragm is significantly higher than that of the standard microphone. Figure 4-Figure 9 It can be seen that under the 125HZ frequency signal, the signal-to-noise ratio gap is the largest, the standard microphone is about 40dB, and the gold foil graphene diaphragm EFPI fiber optic microphone is about 100dB.

[0118] like Figure 10-15 The following is a comparison of the time domain signals of the gold foil graphene diaphragm pickup and the standard microphone at different signal frequencies. Figure 10 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 50HZ. Figure 11 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 63HZ. Figure 12 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at 80HZ signal frequency. Figure 13 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 100HZ. Figure 14 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 125HZ. Figure 15 This is a time domain signal comparison chart of the gold foil graphene diaphragm pickup and the standard microphone at a signal frequency of 160HZ. Figure 10-15 As shown in the figure, at different frequencies of 50 Hz, 63 Hz, 80 Hz, 100 Hz, 125 Hz, and 160 Hz, the time domain signal of the gold foil / graphene composite diaphragm EFPI fiber microphone is significantly better than that of a standard microphone. This is especially true for low-frequency signals below 100 Hz, where the standard microphone outputs more spikes and poor signal quality. Response experiments at different frequencies show that the gold foil / graphene composite diaphragm EFPI fiber microphone significantly outperforms the standard microphone in both signal-to-noise ratio and time domain signal at low frequencies.

[0119] Experimental measurements show that the resonant frequencies of the EFPI fiber optic microphone with a gold foil / graphene composite diaphragm and a diameter of 15 mm are 70 Hz, 135 Hz, 275 Hz, 310 Hz, 365 Hz, 416 Hz, 470 Hz... 1060 Hz, 1115 Hz, 1165 Hz, 1213 Hz, 1262 Hz..., and in a 50 dB noise environment, it can detect a sound source with a sound intensity of 40 decibels at a distance of 50 meters, with a resonant frequency width of 5 Hz. This is equivalent to a micro-acoustic pickup that can detect a sound source with a sound intensity of 80 decibels at a distance of 6,400 meters.

[0120] By manipulating the wrinkles on the surface of the graphene diaphragm, the resonant frequency of the gold foil / graphene composite diaphragm EFPI fiber microphone is controlled. Because graphene film exhibits varying degrees of defects during its fabrication, the success rate of fabricating the diaphragm decreases as the surface area of ​​the film increases. When the diameter increases to over 2mm, the "inverted hanging method" is used to fabricate the graphene diaphragm. The diameter of the graphene diaphragm is then increased to 15mm, and the thickness of the diaphragm is appropriately increased to 20-30 layers. The key step of the "inverted suspension method" is to transfer PMMA / graphene to the surface of a clean silicon wafer, first soak the PMMA surface with anhydrous ethanol, then place the PMMA surface downward on a quartz U-shaped groove, use a peristaltic pump to slowly introduce acetone into the U-shaped groove (for about 3 minutes), wait for the acetone to stop flowing, slowly lift one side of the quartz groove to allow the acetone reagent in the groove to slowly flow out, and place the graphene diaphragm structure in the air to dry for 1 minute. Then, use tweezers to slowly clamp it out and flip it over to the silicon wafer facing down and place it in the sample box. The degree of relaxation and wrinkle state of the graphene diaphragm can be controlled by adjusting the flow rate of acetone, the flow rate of acetone, and the angle and speed of the quartz groove lifting. In this way, the resonant frequency of the gold foil / graphene composite diaphragm EFPI fiber microphone can be adjusted, and then the appropriate diaphragm can be selected for target detection based on the specific target.

[0121] In the present invention, since the silicon wafer used is very thin and brittle, it is difficult to drill a through hole in the silicon wafer by mechanical processing. The energy density of the laser is very high, and a laser marking machine is used to cut the silicon wafer into standard pieces of 25mm×25mm.

[0122] During the laser drilling process, contaminants will be present on the surface of the silicon wafer. You need to first clamp the silicon wafer into a beaker, pour in deionized water that is level with the liquid level of the ultrasonic cleaner, and use an ultrasonic cleaner to clean it. This method can clean the contaminants on the surface of the silicon wafer and improve the hydrophilicity of the silicon wafer.

[0123] After cleaning the silicon wafer, remove it with tweezers and place it on filter paper to dry. Cut the 5cm×5cm graphene sheet into 25mm×25mm pieces. Before using the silicon wafer to retrieve it, first place the graphene film in water to release it. Then, use filter paper to scoop up the graphene that has been released onto the surface of the deionized water. Use a straw to remove excess water from the filter paper (until no water droplets appear on the filter paper). While the filter paper is still wet, cut out the desired pattern. Allow the filter paper to dry naturally before releasing it again. The graphene needs to be suspended for as long as possible, and tweezers should be used to spread it out as much as possible. This process should be completed in one go; avoid cutting multiple times. Once the graphene is suspended on the liquid surface and fully spread out, use a silicon wafer to scoop it out. First, place it on the surface of filter paper to dry naturally, then dry it in a dryer at 80°C for 30 minutes.

[0124] The key step of the "inverted suspension method" is to transfer PMMA / graphene to the cleaned silicon wafer surface, first soak the PMMA surface with anhydrous ethanol, and then place the PMMA surface downward on a quartz U-shaped groove, and use a peristaltic pump to slowly introduce acetone into the U-shaped groove (for about 3 minutes). After the acetone stops flowing, slowly lift one side of the quartz groove to allow the acetone reagent in the groove to slowly flow out. After placing the graphene diaphragm structure in the air to dry for 1 minute, it is slowly clamped out with tweezers and turned over to the silicon wafer facing down and placed in the sample box.

[0125] The graphene diaphragm structure was left to dry at room temperature to allow the organic reagent to evaporate naturally, resulting in a pure graphene diaphragm structure. After resolving the problem of excessive wrinkles in the graphene diaphragm, an ultra-thin graphene diaphragm structure with a diameter of 15 mm was produced.

[0126] Finally, place the gold foil side of the graphene composite diaphragm toward the quartz cavity and fit it tightly with the quartz cavity.

[0127] Existing research on graphene diaphragms only proposes the concept of a graphene diaphragm, without providing a detailed preparation process. Furthermore, the resonant frequency of the graphene diaphragm is not understood. Research primarily aims to improve the sensitivity of the pickup diaphragm, without lowering the lower limit of sound detection. Furthermore, the resonant frequency of the graphene diaphragm is not utilized, nor is the high signal-to-noise ratio of the graphene diaphragm considered. Furthermore, previous patents have focused on multi-layer graphene composite diaphragms, focusing primarily on the diaphragm's high-frequency ductility and its ability to balance high and low-pitched sound effects. However, the actual thickness of the diaphragm is relatively large, making it unsuitable for use as a micro-acoustic pickup diaphragm.

[0128] Because the experimental values ​​of graphene's resonant frequencies closely match the theoretical values ​​of the zero-order cylindrical Bessel function, this paper calculates the resonant frequencies of graphene membranes with different parameters using the root values ​​of the zero-order cylindrical Bessel function J0(z), ensuring that the resonant frequencies of the graphene membranes match the characteristic frequencies of the target to be identified and located. After studying the vibration modes of the graphene membranes, we assembled a prototype of a long-range target sound recognition pickup based on graphene film, based on the principle of Fabry-Perot interferometry.

[0129] The characteristic frequency of the pickup can be controlled by using parameters such as the coverage area of ​​the gold foil in the graphene / gold foil diaphragm, the number of graphene layers, and the wrinkles on the surface of the graphene diaphragm. It has a good effect on detecting multiple characteristic frequencies at the same time, and the effect is good when compared with the standard microphone. The signal-to-noise ratio is significantly better than that of the standard microphone.

[0130] Experiments have shown that the gold foil / graphene diaphragm's amplitude at resonant frequencies is hundreds of times greater than at normal frequencies, with a distinct response to multiple characteristic frequencies. By measuring the large-amplitude vibration response of the gold foil / graphene diaphragm at resonant frequencies in the presence of high background noise, the researchers were able to capture minute sound signals from a distance.

[0131] Through experiments, it was measured that the resonant frequencies of the EFPI fiber optic microphone with a diameter of 15mm are 70HZ, 135HZ, 275HZ, 310HZ, 365HZ, 416HZ, 470HZ...1060HZ, 1115HZ, 1165HZ, 1213HZ, 1262HZ..., with a total of about 30 resonance points. Therefore, a single gold foil / graphene diaphragm can measure about 30 long-distance micro-acoustic signals of different frequencies.

[0132] The resonant frequency of graphene diaphragms with different parameters can be calculated by the root value of the zero-order cylindrical Bessel function, and the characteristic frequency of the pickup can be controlled by using parameters such as the coverage area of ​​the gold foil in the gold foil / graphene diaphragm, the number of graphene layers, and the wrinkles on the surface of the graphene diaphragm. This makes the characteristic frequency of the gold foil / graphene diaphragm consistent with the detection target frequency, which can effectively detect distant sound targets, and the signal-to-noise ratio of the pickup is significantly better than that of a standard microphone.

[0133] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A gold foil graphene composite diaphragm multi-eigenvalue pickup, characterized in that: It includes: A gold foil graphene diaphragm (1), a glass support (2) and an optical fiber (3), wherein the glass support (2) is a rectangular parallelepiped with a hole at the bottom and a cavity inside; The gold foil graphene diaphragm (1) is attached to the top of the internal cavity of the glass support (2), the optical fiber (3) is inserted into the hole at the bottom of the glass support (2), and the internal cavity of the glass support (2) constitutes an FP resonant cavity (4); Gold foil graphene diaphragms (1) with different eigenvalues ​​are obtained by adjusting the parameters of the gold foil graphene diaphragm (1), wherein the eigenvalues ​​are equidistant, and the parameters include wrinkle state, thickness, diameter and gold foil area. Then, by adjusting the eigenvalue of the gold foil graphene diaphragm (1), the resonant frequency of the gold foil graphene diaphragm (1) is matched with the characteristic frequency of the target to be identified; The specific method of obtaining gold foil graphene diaphragms (1) with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm (1), and then matching the resonant frequency of the gold foil graphene diaphragm (1) with the characteristic frequency of the target to be identified by regulating the eigenvalue of the gold foil graphene diaphragm (1) comprises: The sound pressure P on the surface of the gold foil graphene diaphragm (1) is: P=P a e jwt ; Among them, P a represents the amplitude of the sound pressure, e represents the natural base, j represents the imaginary unit, w represents the circular frequency of the sound wave, and t represents time; External force F on the surface element dxdy F For: F F =Pdxdy; Substituting into the membrane vibration equation, we obtain the forced vibration equation of the circular membrane: Among them, r represents the radial distance of the pole, that is, the polar diameter, η represents the equilibrium direction distance of a point on the membrane from the equilibrium position, that is, the deflection, θ represents the angle between the polar diameter and the polar axis, and c represents a constant. represents partial derivative; The solution is: η(t,r)=η a e jwt Among them, η(t,r) represents the distance in the equilibrium direction from the equilibrium position of a point on the membrane as a function of time t and polar radius r, η a represents the amplitude of displacement, k represents a constant, k = 2πf / c, f represents the sound frequency, T represents the membrane tension, unit is N / m, a represents the membrane radius, J0(kr) represents the change of the value of the zero-order Bessel function J0 with the value of r, where r = 0, J0(kr) = 1, indicating that the amplitude of the circular membrane center is the largest, J0(ka) represents the change of the value of the zero-order Bessel function J0 with the value of the membrane radius a; The amplitude of displacement η a Taking the average, we get: J2(ka) represents the change of the value of the second-order Bessel function J2 with the value of the membrane radius a; Then the resonant frequency of the gold foil graphene diaphragm (1) is obtained Among them, μ n represents the n roots of the zero-order Bessel function, and λ represents the resonant frequency f m The proportionality coefficient with the root value of the zero-order Bessel function; The root value of the zero-order Bessel function J0 is directly proportional to the characteristic frequency of the target to be identified.

2. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 1, characterized in that: The specific process of obtaining gold foil graphene diaphragms (1) with different eigenvalues ​​by adjusting the parameters of the gold foil graphene diaphragm (1) and then regulating the resonant frequency of the gold foil graphene diaphragm (1) includes: The fewer wrinkles the gold foil graphene diaphragm (1) has, the higher the resonance frequency; the more wrinkles the gold foil graphene diaphragm (1) has, the lower the resonance frequency; The resonant frequency is inversely proportional to the first power of half the thickness of the gold foil graphene diaphragm (1).

3. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 1, characterized in that: The length of the FP resonant cavity (4) is a length that makes the contrast of the interference fringes 1.

4. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 1, characterized in that: The gold foil graphene diaphragm (1) has a diameter of 2 to 20 mm and a number of layers of 20 to 30.

5. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 1, characterized in that: The gold foil graphene diaphragm (1) is prepared by an inverted hanging method, and the specific process includes: S1, transferring graphene coated with PMMA protective film to the surface of silicon wafer substrate; S2. Wetting the surface of the PMMA protective film with anhydrous ethanol, placing the graphene and silicon wafer substrate soaked with the PMMA protective film in a quartz tank, with the surface soaked with the PMMA protective film facing downward; S3, pass acetone into the quartz tank for 3 minutes; S4. Lift one side of the quartz tank to allow acetone to flow out of the quartz tank, thereby obtaining a graphene diaphragm structure; S5. Place the prepared graphene diaphragm structure in air to dry for 1 minute; S6. Suspending a gold foil with a thickness of 12 nm on the surface of the graphene diaphragm structure, and adsorbing the gold foil on the surface of the graphene diaphragm structure through intermolecular forces, thereby obtaining a gold foil graphene diaphragm (1).

6. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 5, characterized in that: The wrinkle state of the gold foil graphene diaphragm (1) is controlled by the flow rate and flow velocity of the acetone entering the quartz tank in S3, the flow velocity of the acetone flowing out of the quartz tank in S4, and the lifting angle of the quartz tank.

7. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 6, characterized in that: In S3, acetone is introduced into the quartz tank through a peristaltic pump; the flow rate and flow velocity of the acetone into the quartz tank are controlled by the peristaltic pump.

8. The gold foil graphene composite diaphragm multi-eigenvalue pickup according to claim 1, characterized in that: The bottom of the glass support (2) is also provided with four ventilation holes, which are distributed around the hole for inserting the optical fiber (3).

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