A method and device for broadband control of ultrasonic transmission based on nanoparticle film

Abstract

The present invention discloses a method and device for broadband control of ultrasonic transmission based on nanoparticle membranes, and belongs to the field of sound field control. The method is specifically as follows: immersing a nanoparticle membrane layer in a water environment, and an air layer is formed at the critical point between the rough surface of the nanoparticle membrane layer and the water; an incident ultrasonic wave is emitted to the water environment, and the air layer forms an impedance mismatch acoustic boundary for the incident ultrasonic wave, thereby achieving total reflection of the incident ultrasonic wave. The method and device for broadband control of ultrasonic transmission based on nanoparticle membranes of the present invention, by performing surface modification treatment on the substrate material, enables the surface of the control device to achieve a super-hydrophobic self-cleaning effect, and can achieve acoustic total reflection of underwater ultrasonic waves within a wide frequency range of 1-15MHz, and has the advantages of being easy to reuse, and being able to selectively reflect sound waves in certain areas according to a pre-set pattern to form a specific sound field, and the like.

Description

Technical Field

[0001] The present invention belongs to the field of sound field regulation, and more specifically, relates to a method and device for broadband regulation of ultrasonic transmission based on nanoparticle membranes. Background Art

[0002] Surface wettability is one of the important properties of solid material surfaces and plays a pivotal role in the application of engineering environments and functional materials. However, surface modification of solid materials with different processes is very important for practical applications. The standard for evaluating the wettability of solid surfaces is the contact angle between the droplet and the solid surface. Generally speaking, if the contact angle is greater than 90°, the material is called a hydrophobic material; when the contact angle is greater than 150°, the material is a superhydrophobic material. If the surface of a material can meet the requirement of a contact angle greater than 150°, the surface will exhibit a self-cleaning effect, namely the "lotus effect".

[0003] Research shows that the reason why materials or structures can exhibit self-cleaning properties is generally due to their low surface energy or suitable surface fine roughness structure. With the increasing maturity of nano-micromachining technology, artificial structural materials are increasingly tending to the micro-nano scale. For functional artificial materials with larger macroscopic scales, they naturally form a rough surface structure, which makes the solid surface have the lotus leaf self-cleaning effect. However, due to technical reasons, it is easier to reduce the surface free energy than to manufacture the surface roughness structure by micro-nano processing technology. Therefore, for the solid material matrix, low surface energy chemical methods are generally used to modify its surface in order to achieve the self-cleaning effect of the material.

[0004] At present, the lotus leaf effect and its self-cleaning function are combined with the super-hydrophobic properties of materials in the regulation and application of underwater sound waves. Within a certain range, the total reflection of underwater sound waves in a wide frequency range is very important for underwater detection. In the prior art, the super-hydrophobic surface with self-cleaning function and capable of total reflection of underwater sound waves within a certain frequency band is generally a chemically synthesized film, by forming a micro-nano morphology of a "papillary" structure on its surface, after contacting with a liquid water environment, the contact surface will be formed in a Cassie-Baxter state, so that the film can be used as a super-hydrophobic film. However, this film has a limited range of suppression of underwater sound wave frequencies, such as meta-skin insulator, which is a chemically synthesized fiber film, and when low-frequency (1-5MHz) ultrasound is transmitted through the film, it will produce a strong reflection effect, and when the sound wave band range is much higher than 5MHz, because the sound wave wavelength reaches the micron level, the film in the prior art is not obvious in the transmission regulation effect of the sound wave. Summary of the invention

[0005] In view of the defects and improvement needs of the prior art, the present invention provides a method and device for broadband control of ultrasonic transmission based on nanoparticle membranes, the purpose of which is to achieve total acoustic reflection of underwater ultrasonic waves.

[0006] A method for broadband control of ultrasonic transmission based on nanoparticle membrane, the method specifically comprising:

[0007] The nanoparticle film layer is immersed in a water environment, and an air layer is formed at the boundary between the rough surface of the nanoparticle film layer and the water; an incident ultrasonic wave is emitted into the water environment, and the air layer forms an impedance mismatch acoustic boundary for the incident ultrasonic wave, thereby achieving total reflection of the incident ultrasonic wave.

[0008] Furthermore, after the rough surface of the nanoparticle film layer comes into contact with the water environment, a super-hydrophobic surface is formed.

[0009] Furthermore, the nanoparticle film is a silicon dioxide nanoparticle film.

[0010] Furthermore, the average particle size of the silica nanoparticles in the silica nanoparticle film is 100 nm.

[0011] A device for implementing any of the above-mentioned methods for broadband regulation of ultrasonic transmission based on nanoparticle membranes, comprising: a substrate and a nanoparticle membrane, wherein the nanoparticle membrane is attached to the substrate, and an air layer is formed at the critical surface when the rough surface of the nanoparticle membrane contacts water.

[0012] Furthermore, the substrate is an ultrasonic super-transparent membrane.

[0013] Furthermore, the thickness of the ultrasonic super-transparent film is ≤10um, and it can achieve total reflection of incident ultrasonic waves within a frequency range of 1-15MHz.

[0014] Furthermore, the ultrasonic super-transparent membrane is a PVC membrane or a PDMS material.

[0015] Further, the nanoparticle film is spin-coated on the substrate.

[0016] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0017] (1) The method and device for controlling broadband ultrasonic transmission based on nanoparticle membranes of the present invention immerse the nanoparticle membrane layer in a water environment, and an air layer is formed at the boundary between the rough surface of the nanoparticle membrane and the water; an incident ultrasonic wave is emitted into the water environment, and the air layer forms an impedance mismatch acoustic boundary for the incident ultrasonic wave, thereby achieving total reflection of the incident ultrasonic wave.

[0018] (2) Taking the frequency of 1-15 MHz as an example, when the thickness of the ultrasonic super-transparent film is ≤10 um, the device of the present invention can achieve total reflection of the incident ultrasonic wave within this frequency range.

[0019] (3) Due to the micro-nano morphology of the papillary structure formed between the nanoparticles, after contact with the liquid water environment, the contact surface will form a Cassie-Baxter state, so that the surface of the control device can achieve a superhydrophobic self-cleaning effect.

[0020] (4) The nanoparticle film-based ultrasound transmission broadband control device of the present invention preferably uses spin coating to construct a nanoparticle coating on a substrate material. The coating can be erased without damaging the substrate material, thereby facilitating the reuse of the substrate material.

[0021] (5) The nanoparticle film-based ultrasound transmission broadband control device of the present invention preferably adopts an ultra-thin coating nanoparticle structure with a scale reaching deep subwavelength and an average particle size of about 100 nm, so that the super-hydrophobic nano-coating can reduce the influence of solid-liquid coupling.

[0022] In summary, the nanoparticle membrane-based ultrasonic transmission broadband control device of the present invention has super-hydrophobic self-cleaning properties and can achieve acoustic total reflection of underwater ultrasonic waves in a wide frequency range of 1-15 MHz, that is, it realizes the modulation of sound waves in the acoustic field. In addition, it also has the advantages of easy reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of preparing a nanoparticle film according to an embodiment of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of an ultrasonic transmission broadband control device based on a nanoparticle film according to an embodiment of the present invention.

[0025] Figure 3 The present invention relates to the contact angle measurement of an ultrasonic transmission broadband control device based on a nanoparticle film according to an embodiment of the present invention.

[0026] Figure 4 Schematic diagram of sound waves passing through a PVC film and an ultrasound transmission broadband control device according to an embodiment of the present invention, wherein: Figure 4 a in the figure is a schematic diagram of sound waves passing through the PVC membrane. Figure 4 b is a schematic diagram of sound waves passing through the ultrasonic transmission broadband control device according to an embodiment of the present invention.

[0027] Figure 5 The invention shows the suppressive effect of the broadband control device for ultrasonic transmission based on nanoparticle membrane on the transmission of 1-15 MHz underwater sound waves in the time domain and space.

[0028] Figure 6The present invention shows the suppressive effect of the broadband control device for ultrasonic transmission based on nanoparticle membrane on the transmission of 1-15 MHz underwater sound waves in the frequency domain. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The present invention provides a method for broadband control of ultrasound transmission based on nanoparticle membranes, which specifically comprises:

[0031] The nanoparticle film layer is immersed in a water environment, and an air layer is formed at the boundary between the rough surface of the nanoparticle film and the water; an incident ultrasonic wave is emitted into the water environment, and the air layer forms an impedance mismatch acoustic boundary for the incident ultrasonic wave, thereby achieving total reflection of the incident ultrasonic wave.

[0032] Correspondingly, a nanoparticle film-based ultrasound transmission broadband control device is provided, which includes: a substrate and a nanoparticle film, wherein the nanoparticle film is attached to the substrate, and the substrate is an ultrasound super-transparent film. In a water environment, the rough surface of the nanoparticle film forms an air layer, which can form an impedance mismatch acoustic boundary for the incident ultrasound wave, thereby achieving total reflection of the incident ultrasound wave in the frequency range of 1-15MHz, thereby suppressing the transmission of the sound wave.

[0033] The thickness of the substrate is in the deep sub-wavelength scale, which can ensure that the substrate is an ultrasonic super-transparent film, and the attenuation rate of ultrasonic waves passing through the substrate is small and can be ignored.

[0034] According to relevant theories, the thickness of the substrate material does not exceed λ min / 10, i.e. 10um, the substrate thickness can be considered as deep sub-wavelength scale, where λ min is the ultrasonic wavelength corresponding to 15MHz, f max is 15MHz, c is the speed of ultrasound in water at room temperature, which is 1500m / s.

[0035] Taking 1-10MHz as an example, the thickness of the substrate does not exceed 15um.

[0036] Taking 1-5MHz as an example, the thickness of the substrate does not exceed 30um.

[0037] The nanoparticle film is spin-coated on a substrate material, and the ultrasound super-transparent film as the substrate can be a thin polyvinyl chloride (PVC) film or a PDMS material.

[0038] In this embodiment, the base material is a thin polyvinyl chloride (PVC) film with a thickness of about 10 um, and the film is an ultrasonic super-transparent film. The nanoparticle material is silicon dioxide nanoparticles.

[0039] like Figure 1 As shown, the preparation method of the nanoparticle film of this embodiment is to dissolve 3mL of tetraethyl orthosilicate (analytical pure) in 100mL of anhydrous ethanol (analytical pure), mix well to prepare a solution, then dissolve 3mL of concentrated ammonia (analytical pure) in the solution, stir and react for 24h, and vacuum dry at a temperature of 60°C to obtain SiO2 particles. 40mL of dimethylformamide (analytical pure) and 10mL of butanone (analytical pure) are measured and mixed, 2.5g of polyvinylidene fluoride (analytical pure) is added, and a certain amount of SiO2 particles is added after mixing and stirring the mixture, and 5mL of silane coupling agent KH570 (analytical pure) is added, and the mixture is heated and stirred for 2h and then allowed to stand to obtain a nanoparticle mixed solution, and the nanoparticle mixed solution is spin-coated onto the substrate material (PVC film) to form the nanoparticle film of this embodiment. In this embodiment, the sol-gel method is adopted to prepare the silicon dioxide particles. Since the surface particles are uniform and have good dispersibility after dissolution without obvious agglomeration, we select silicon dioxide particles with a size of 100 nm as the dispersion liquid component.

[0040] In this embodiment, a small-scale coating machine (EZ4, Schwan Technology) is used to prepare the spin-coated film required for the substrate of the present invention, i.e., the nanoparticle film. 1.2 mL of the prepared solution is dripped onto the substrate material (PVC film). Two sets of rotation parameters are given for rotation setting. First, the solution is rotated at 50 rpm for 20 seconds to allow the dripping droplets to spread. Then, the solution is evenly coated on the substrate at 800 rpm for 100 seconds. After the mixed liquid is spin-coated, it is allowed to evaporate to obtain the ultrasonic transmission broadband control device in this embodiment.

[0041] In the ultrasonic transmission broadband control device of the embodiment of the present invention, the spin-coated nanoparticles are freely dispersed on the surface of the substrate. Due to the presence of the nanoparticles, the surface is composed of silicon dioxide particles with excellent dispersion performance and an average particle size of 100nm. At the same time, spin coating cannot spread the nano-scale particles evenly on the surface, so the particles will form a papillary structure (similar to the lotus leaf effect), such as Figure 2 As shown. When we immerse the ultrasonic transmission broadband control device in a water environment, due to its slightly rough surface, a tiny air layer will be formed at the interface. At this time, there is a solid-liquid-gas three-phase state at the interface, which satisfies the theoretical model under the Cassie-Baxter state, that is, a Cassie-Baxter state is constructed on any ultrasonic super-transparent membrane substrate, and there is a solid-liquid-gas three-phase state at the interface. For the device after treatment, its surface has super-hydrophobic properties. Figure 3As shown, the surface contact angle of the ultrasonic transmission broadband control device of the embodiment of the present invention is measured as CA = 161.2°. In other embodiments, the control frequency can be adjusted according to actual needs, and the corresponding film thickness of the substrate can also be calculated.

[0042] In this embodiment, the transmission of sound waves through three different media, namely, a water environment medium, a thin polyvinyl chloride film, and an ultrasonic transmission broadband control device with super-hydrophobic properties in the present invention, is used to illustrate the total reflection of the incident sound wave by the device of the present invention within a broadband range of 1-15M.

[0043] Set the acoustic impedance of the sound wave in the water environment medium:

[0044] R0=ρ0c0, where ρ0 is the density of the water environment medium and c0 is the propagation speed of the sound wave in the water environment medium.

[0045] In the water environment medium, a 10um thick isotropic thin polyvinyl chloride film, i.e. PVC film, is inserted, and its acoustic impedance is:

[0046] R1=ρ1c1, where ρ1 is the density of the PVC film and c1 is the propagation speed of sound waves in the PVC film.

[0047] Acoustic impedance in the silica nanoparticle film in this example (its thickness is negligible):

[0048] R2=ρ2c2, where ρ2 is the density of the silica nanoparticle film and c2 is the propagation speed of the sound wave in the silica nanoparticle film.

[0049] like Figure 4 As shown in a, due to the different material impedances on both sides of the interface between the water environment medium and the PVC membrane, when the sound wave passes through, part of the incident wave is reflected to form a reflected wave, and part of the incident wave is transmitted into the PVC membrane to form a transmitted wave. The device with the PVC membrane inserted into the water environment medium is used as the control group. Among them, interface A is the interface between the water environment and the PVC membrane, and interface B is the interface between the PVC membrane and the water at the sound wave output end.

[0050] like Figure 4 As shown in b, the ultrasonic transmission broadband control device with super-hydrophobic properties in this embodiment (i.e., a silicon dioxide nanoparticle film spin-coated on a PVC film) is inserted into the water environment medium as an experimental group. Since the theoretical model under the Cassie-Baxter state is satisfied, the acoustic impedance of the tiny air layer formed at the interface C is:

[0051] R3=ρ3c3, where ρ3 is the density of the air layer medium and c3 is the propagation speed of the sound wave in the air layer. Under the assumption of linear small amplitude, solve the one-dimensional sound wave equation:

[0052]

[0053] Where p is the sound pressure at any position in the water environment medium, and the relationship between sound pressure and velocity satisfies:

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] Among them, p i represents the incident sound wave in the water environment medium, p r0 is the sound wave reflected into the water medium after the incident sound wave encounters the interface A, p t1 is the sound wave incident on the ultrasonic supertransparent film (PVC film) through the interface A, p r1 is the sound wave reflected into the PVC membrane after passing through interface B (the interface between the PVC membrane and the external water medium), p t is the sound wave transmitted into the water environment. The term before the e index is the amplitude of the sound wave, i.e. p 0i 、p 0ra 、p 1ta 、p 1ra 、p ta They are respectively the amplitude of the incident sound wave in the water environment medium, the amplitude of the sound wave reflected in the water medium after the incident sound wave encounters interface A, the amplitude of the sound wave incident on the ultrasonic super-transparent membrane (PVC membrane) through interface A, the amplitude of the sound wave reflected in the PVC membrane after passing through interface B (the interface between the PVC membrane and the external water medium), and the amplitude of the sound wave transmitted into the water environment. k0 is the wave number propagated in the water environment medium, the positive sign indicates the incident wave, and the negative sign indicates the reverse propagation wave, i.e. the reflected wave. k1 is the wave number propagated in the PVC medium, the positive sign indicates the incident wave, and the negative sign indicates the reverse propagation wave, i.e. the reflected wave. D is the thickness of the PVC medium. In this embodiment, a 10um thick PVC membrane is used as the ultrasonic super-transparent membrane. k j Satisfies the relationship: j is 0, 1, 2.

[0060] According to the equation of motion of the medium in an ideal fluid The velocity potential of each propagating wave can be calculated:

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] Among them, v i is the vibration velocity of the incident sound wave particle in the water environment medium, v r0 is the vibration velocity of the sound wave particle reflected into the water medium after the incident sound wave encounters the interface A, v t1 is the vibration velocity of the acoustic wave particle incident on the PVC film through the interface A, v r1 is the vibration velocity of the sound wave particles reflected into the PVC membrane after passing through interface B (the interface between the PVC membrane and the external water medium), v t is the vibration velocity of the sound wave particle transmitted into the water environment.

[0067] The conditions for the continuity of sound pressure and particle velocity at the interface A and B are:

[0068] p i +p r0 =p t1 +p r1 ;

[0069] v i +v r0 =v t1 +v r1 ;

[0070] The ratio of the sound intensity on interface B to the sound intensity of the incident wave at interface A can be obtained:

[0071]

[0072] In this embodiment, a PVC film with D=10 um is used, which satisfies the condition k1D<<1. I ≈1. That is, the middle layer of the PVC film in this embodiment is acoustically transparent, which provides a good base material for further highlighting the nanoparticle film of the present invention as a total reflection device.

[0073] When the device of the present invention is completely immersed in an aqueous medium, Figure 4 As shown in b, the whole system consists of three interfaces, interface A is the interface between the water environment and the ultrasonic supertransparent membrane, interface B' is the interface between the ultrasonic supertransparent membrane and the silica nanoparticle membrane, and interface C is the interface between the nanoparticle membrane and water, that is, the air layer here.

[0074] After the sound wave completely passes through the PVC film layer in this embodiment, it encounters the interface B'. Since the thickness of the spin-coated nanoparticle layer is very small, the impedance is regarded as the impedance of water, which is 1.5 MRayl (where 1 MRayl = 1 × 10 6 kg / s / m 2 ) can be regarded as an acoustically transparent layer. When encountering interface C, that is, the air layer, the impedance difference is large, and the sound wave encounters a soft boundary, resulting in total reflection of the wave.

[0075] The following part analyzes the theory of total reflection that occurs after encountering the air layer:

[0076]

[0077]

[0078] p2 is the superposition of the wave intensity of the sound wave advancing along the incident direction of the sound wave and the sound wave intensity of the sound wave encountering the air layer at the interface C in the nanoparticle film medium, p3 represents the transmitted wave transmitted to the air layer at the interface in the silica nanoparticle film in this embodiment, k2 is the wave number propagating in the nanoparticle film medium, the positive sign represents the incident wave, the negative sign represents the reverse propagating wave, i.e., the reflected wave, p i2 is the vibration amplitude of the incident wave (i.e. the original incident sound wave p i The amplitude of the sound wave transmitted into the nanoparticle film medium after passing through the interface A and B), p r2 is the amplitude after reflection from the air layer at the interface of the silicon dioxide nanoparticle film in this embodiment, p t2 is the amplitude of the sound wave that passes through the ultrasonic super-transparent membrane (i.e., the PVC membrane in this embodiment) and enters the air layer, and k3 is the wave number of the sound wave in the interfacial air layer in the silicon dioxide nanoparticle membrane in this embodiment.

[0079] According to the equation of motion Solve for its particle velocity:

[0080]

[0081] Where v2 is the vibration velocity of the particles in the nanoparticle film medium, v i2 is the particle velocity amplitude in the incident wave direction, v r2 is the particle velocity amplitude in the direction of the reflected wave, v3 is the particle velocity caused by the wave transmitted into the air layer at the interface of the silicon dioxide nanoparticle film in this embodiment, and v t2 is the particle vibration velocity amplitude in the interface air layer.

[0082] According to the continuity conditions of the sound pressure at the interface and the normal particle velocity: p2=p3; v2=v3, it is obtained that the silicon dioxide nanoparticle film and the interfacial air dielectric layer at the interface C in this embodiment satisfy:

[0083] pi2 +p r2 =p t2 ;v i2 +v r2 =v t2 .

[0084] Furthermore, the ratio of the reflected sound pressure to the incident sound pressure at the interface between the silicon dioxide nanoparticle film and the interfacial air dielectric layer in this embodiment is obtained. p , the ratio of transmitted sound pressure to incident sound pressure t p They are:

[0085] in, R m =ρ m c m , m, n take values ​​of 0, 1, 2, 3 respectively.

[0086] When the sound wave passes through the interface C between the silicon dioxide nanoparticle film and the interfacial air dielectric layer in this embodiment, according to the sound wave energy relationship:

[0087] I=p 2 / 2ρc=p 2 / 2R,

[0088] Among them, I is the sound intensity, p is the sound pressure, R is the impedance, ρ is the density of the medium, and c is the propagation speed of the sound wave in the medium. The energy relationship at the interface C can be obtained:

[0089]

[0090]

[0091] Among them, r I is the energy of the reflected sound wave, t I The impedance of the PVC film medium is 3.2982 MRayl, and the characteristic impedance of the surrounding water environment medium is 1.5 MRayl (where 1 MRayl = 1×10 6 kg / s / m 2 ), according to the energy relationship, its energy transmission t I About 86%. Generally, we agree that sound wave transmission ≥ 80% can meet the boundary conditions of similar impedance. According to the theory of propagation in the intermediate medium layer when vertical incidence k1 is the wave number of the sound wave in the PVC medium. At this time, T I≈1, and the substrate material satisfies k1D<<1. Since the thickness of the nanoparticle film can be ignored, that is, the thickness of the device in the present invention satisfies the relationship: k1D<<1, then the sound wave after passing through the device in the present invention is fully transmitted. The transmitted sound wave meets the air medium at the interface C, and the impedance mismatch boundary condition is met at this interface, where the characteristic impedance of the air medium layer is 0.00041503MRayl. When the sound wave meets this soft boundary, total reflection will occur.

[0092] Based on the above analysis, the sound waves are still fully transparent after passing through the PVC film, and almost no reflection occurs; for the ultrasonic transmission broadband control device with super hydrophobic properties in the present invention, the impedance R1+R2 satisfies: R1+R2≈R0, that is, the overall impedance of the substrate material and the nanoparticle film is close to the impedance of the water environment medium, and satisfies k1D<<1. After the sound waves pass through the substrate material, they are still fully transparent, and almost no reflection occurs. Since the device in the present invention is immersed in the surrounding water medium, such as Figure 4 As shown in b in the figure, a stable air / water interface will be formed, causing the medium at the output end of the transmission control device in the present invention to be equivalent to the air medium when the sound wave propagates in the water environment medium. At this time, the acoustic impedance of the tiny air layer medium is: R3=ρ3c3, ρ3 is the density of the air layer medium, c3 is the propagation speed of the sound wave in the air layer, and satisfies the relationship: R3<R0, then at this time, the ratio of the reflected / transmitted sound pressure to the incident sound pressure is r p =1,t p =0, the ratio of transmitted sound intensity t I ≈0, at this time, the interface C at the output end of the device in the present invention is a soft boundary for the sound wave in the water environment, the sound wave will be totally reflected, and the sound pressure phase difference between the reflected wave and the incident wave is 180°.

[0093] From the above, it can be seen that in the water environment medium, the PVC film can be regarded as an acoustically transparent material, and for the PVC film coated with super-hydrophobic nanoparticles (i.e., the ultrasonic transmission broadband control device with super-hydrophobic properties of the present invention), the thin film layer formed by the nanoparticles is evenly attached to the PVC film, and the nanoparticles will form an air layer on the surface of the film layer. For the incident sound wave, due to the existence of the impedance mismatch condition, the transmission of the sound wave is suppressed, and the total reflection of the incident sound wave is achieved. In this embodiment, the system environment medium is a water environment, the water environment impedance value is 1.5 MRayl, the air impedance value is 0.00041503 MRayl, and the acoustic impedance of the PVC film is 3.2982 MRayl, wherein the density of water at 20°C is 1000kg / m 3 , the speed of sound is about 1500m / s; the air density is 1.21kg / m 3 , the speed of sound is about 343m / s; the density of PVC film is 1380kg / m 3 , the propagation speed of sound waves in PVC film is 2390m / s.

[0094] Specifically, in this embodiment, a commercial piezoelectric ceramic conversion device (water-immersed transducer) is used to verify the transmission performance of the ultrasonic transmission broadband control device with super-hydrophobic properties in this embodiment. The water-immersed transducer converts the electrical energy of the time-harmonic vibration into mechanical vibration through the electroacoustic conversion mechanism, thereby exciting the vibration source on the surface of the transducer and radiating sound waves in the water environment; the transmission signal spectrum of the water-immersed transducer through the device in this embodiment is acoustically characterized by using an underwater ultrasonic detection device (Precision Acoustic UMS3), and the waveform and spectrum of sound waves with center frequencies of 1MHz, 2.25MHz, 3.5MHz, 5MHz, 10MHz, and 15MHz are measured when they pass through the water environment medium, the PVC film, and the ultrasonic transmission broadband control device with super-hydrophobic properties in the present invention.

[0095] like Figure 5 As shown, from the dimension of time domain, the comparison of time-harmonic signal waveforms is observed. Under the condition of excitation of piezoelectric transducer signal waveforms with different center frequencies, the wave envelope amplitudes of the sound waves of each frequency band in the water environment medium and the PVC film are highly consistent, that is, the PVC film has little energy loss for the sound waves in the propagation path. After the PVC film is spin-coated with nanoparticles to form the ultrasonic transmission broadband control device with super-hydrophobic properties in the present invention, its transmission amount is reduced to zero in the time domain space. It shows that the medium containing only PVC film has no reflection effect on the sound waves, while the ultrasonic transmission broadband control device with super-hydrophobic properties of the present invention realizes total reflection of the incident sound waves. And the device in the present invention can reflect most of the sound waves to the transducer to form standing waves, and has a strong boundary reflection effect.

[0096] In addition, we expand the time domain signal into the frequency domain, such as Figure 6As shown. Since the water-immersed transducer has a certain acoustic bandwidth, under the excitation of different center frequencies (1MHz, 2.25MHz, 3.5MHz, 5MHz, 10MHz, 15MHz), it can be seen that in the frequency domain space, the amplitude at the main frequency is taken as the maximum value for normalization, and the amplitude curve overlap of the sound wave passing through the water environment medium and the amplitude curve containing only the PVC film is relatively high, indicating that the PVC film has a small loss in the propagation process for the sound wave in the frequency band near the main frequency, and the sound wave passes through the ultrasonic transmission broadband control device with super-hydrophobic characteristics of the embodiment of the present invention, and the amplitude of each frequency range is reduced to zero. On the one hand, it is explained that the medium containing only the PVC film has no reflection effect on the excitation signal of the center frequency band, and the ultrasonic transmission broadband control device with super-hydrophobic characteristics of the embodiment of the present invention realizes the total reflection of the excitation signal of the center frequency band; on the other hand, within the frequency band near the main frequency, the ultrasonic transmission broadband control device with super-hydrophobic characteristics of the present embodiment can also realize the total reflection of the incident sound wave. That is, the ultrasonic control device with super-hydrophobic properties in this embodiment realizes total acoustic reflection of underwater sound waves in a wide frequency range of 1-15 MHz.

[0097] in, Figure 5 and Figure 6 In the figure, Free Space means that the sound wave penetrates the water environment medium, PVC W / O Film means that the sound wave penetrates the thin polyvinyl chloride film, and PVC W / Film means that the sound wave penetrates the ultrasonic transmission broadband control device with superhydrophobic properties in the present invention, that is, the thin polyvinyl chloride film containing a nanoparticle film coating.

[0098] The present invention constructs a coating on a substrate by spin coating, and when the coating is no longer needed, it can be wiped off with alcohol without damaging the substrate, and further acoustic performance characterization can be performed, making it convenient for the substrate to be reused.

[0099] In addition, the nanoparticle film in the present invention can also be pre-set to different patterns, thereby defining different total reflection areas. Specifically, for a specific pattern, we process its mask in a one-to-one ratio, and the material properties of the mask are not required here. The mask is bonded to the substrate so that the two are completely in close contact, and then an appropriate amount of nanoparticle film spin coating liquid is dripped, and the entire device is placed on the spin coater and evenly spread out, and finally the mask layer is removed to obtain a pre-designed pattern. For example, the selective pattern spin coating in the present invention can be applied to commercial piezoelectric ceramic converters. Since commercial piezoelectric ceramic converters generate sound waves in a Gaussian vibration mode, there are great limitations on the formation of a high local energy sound field, but with the modulation mode of the device of the present invention on the spatial sound wave, a focused sound field and a vortex sound field can be formed. Taking the formation of a focused sound field as an example, the phase condition that should be met on the device of the present invention can be calculated. The phase is proportional to the propagation distance, and the pattern can be selectively spin-coated. According to the pre-set pattern, the sound wave can be selectively fully reflected in some areas and completely passed through in some areas, so that the sound wave forms a phase difference, thereby forming a specific sound field.

[0100] The method and device for broadband control of ultrasonic transmission based on nanoparticle membranes of the present invention realize the suppression of incident ultrasonic transmission in the acoustic field, and further can control the sound field.

[0101] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultrasonic transmission broadband control device based on nanoparticle film, characterized in that: include: A substrate and a nanoparticle film, wherein the nanoparticle film is attached to the substrate, and an air layer is formed at the critical surface when the rough surface of the nanoparticle film contacts water; wherein when an incident ultrasonic wave is emitted into a water environment, the air layer forms an impedance mismatch acoustic boundary for the incident ultrasonic wave, thereby achieving total reflection of the incident ultrasonic wave; The substrate is an ultrasonic super-transparent film, the thickness of the ultrasonic super-transparent film is ≤10um, and the ultrasonic super-transparent film can achieve total reflection of the incident ultrasonic wave within the frequency range of 1-15MHz.

2. The nanoparticle film-based ultrasound transmission broadband control device according to claim 1, characterized in that: The ultrasonic super-transparent membrane is a PVC membrane or a PDMS material.

3. The nanoparticle film-based ultrasound transmission broadband control device according to claim 2, characterized in that: The nanoparticle film is spin-coated on the substrate.

4. The nanoparticle film-based ultrasound transmission broadband control device according to claim 1, characterized in that: After the rough surface of the nanoparticle film layer contacts with the water environment, a super-hydrophobic surface is formed.

5. The nanoparticle film-based ultrasound transmission broadband control device according to claim 4, characterized in that: The nanoparticle film is a silicon dioxide nanoparticle film.

6. The nanoparticle film-based ultrasound transmission broadband control device according to claim 5, characterized in that: The average particle size of the silica nanoparticles in the silica nanoparticle film is 100 nm.

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