A photo-induced ultrasonic transmitter and its manufacturing method

Abstract

The present invention discloses a photoultrasound transmitter and its fabrication method. The transmitter comprises a metal nanoparticle-porous alumina array composite layer, which absorbs incident light and converts it into heat. Polydimethylsiloxane, a thermal expansion material, is filled into the nanopores of the alumina array to absorb heat energy and emit ultrasound waves through the thermoelastic effect. The substrate is a glass substrate. The device utilizes the principle of photoultrasound, generating ultrasonic signals under the action of a pulsed laser. The method is simple and produces ultrasound waves with high intensity, high frequency, and a wide bandwidth.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic technology, and in particular to a photo-induced ultrasonic transmitter and a manufacturing method thereof. Background Art

[0002] Ultrasonic transmitters are widely used in ultrasonic diagnosis and medical imaging. Traditional ultrasonic sound sources, such as piezoelectric transducers, suffer from limitations such as large size, low frequency, high drive voltage, susceptibility to electromagnetic interference, and a large focal point for the acoustic waves. With the continuous advancement of science and technology, researchers have proposed the concept of photoultrasound, which generates ultrasound waves with high intensity, high frequency, and wide bandwidth. It is also immune to electromagnetic interference and offers the advantages of miniaturization. Ultrasonic transmitters fabricated using the photoultrasound effect have applications in medical fields such as minimally invasive ultrasonic surgery, thrombolysis, targeted drug delivery, and microinjection.

[0003] Photoacoustic ultrasound emitters are typically composed of a light-absorbing material and a thermal expansion material. Commonly used absorbing materials include carbon-based materials such as carbon black, carbon nanotubes, and candle soot particles, while the thermal expansion material is polydimethylsiloxane (PDMS). The incident light is absorbed by the absorbing material, and the generated heat is transferred to the PDMS, generating ultrasound using the thermoelastic effect. However, in most photoacoustic ultrasound emitter devices, the light-absorbing material and the thermoelastic material are mixed randomly, resulting in random and disordered heat conduction, causing the ultrasound direction to diffuse and the intensity to decrease. Therefore, preparing an ultrasonic emitter with a completely new structure to improve the ultrasound intensity, bandwidth, and photothermal conversion efficiency is a technical challenge that needs to be solved urgently. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a photo-ultrasound transmitter and a manufacturing method thereof. The provided photo-ultrasound transmitter is an ultrasonic transmitter based on self-assembled metal nanoparticles-porous anodic aluminum oxide array-PDMS.

[0005] In a first aspect, the present invention provides a photoacoustic ultrasound transmitter comprising a transparent glass substrate, a light absorbing portion, and a thermal expansion material. The light absorbing portion comprises a porous alumina array, a metal film, and metal nanoparticles. The light absorbing portion is hereinafter referred to as the metal nanoparticle-porous alumina array. The porous alumina array of the present invention is a symmetrical double-pass AAO (Anodic Aluminum Oxide) nanotemplate having uniformly distributed nanopores.

[0006] The metal film is a film layer deposited on the surface of the porous alumina array, and the thickness of the metal film is 50-120nm; the metal nanoparticles are adsorbed on the nanopore walls of the porous alumina array, and the grain diameter ranges from 10-25nm; the thermal expansion material is polydimethylsiloxane PDMS, and the thermal expansion material is filled in the nanopores.

[0007] Preferably, the metal film and the metal nanoparticles are made of materials selected from aluminum or silver.

[0008] Preferably, the center-to-center spacing of the pores of the porous alumina array is 450 nm, and the pore size is 250-350 nm; further preferably, the thickness of the anodized aluminum oxide is 60 μm.

[0009] After the incident laser pulse is absorbed by the metal nanoparticle-porous alumina array-PDMS composite layer of the above-mentioned photoultrasound emitter, it is converted into heat, and then ultrasound is generated using the thermoelastic effect.

[0010] In a second aspect of the same inventive concept, the present invention provides a method for manufacturing a photoultrasound transmitter, comprising the following steps:

[0011] Step S1, growing a metal film on the surface of a double-pass porous anodized aluminum using a physical vapor deposition method, and depositing metal nanoparticles in the pores;

[0012] Step S2: Mixing PDMS and a curing agent at a preset mass ratio in a beaker, immersing the prepared metal nanoparticle-porous alumina array composite layer in a polydimethylsiloxane (PDMS) solution, and magnetically stirring for a preset time; leaving the beaker to stand, so that air remaining in the pores will form bubbles in the solution, and then removing the beaker after the bubbles in the polydimethylsiloxane mixture have completely dissipated;

[0013] Step S3, immersing the prepared metal nanoparticle-porous alumina array composite layer in a PDMS mixed solution, allowing the PDMS mixed solution to fully penetrate the nanopores of the porous alumina array; removing the metal nanoparticle-porous alumina array-PDMS composite layer and placing it on a transparent glass substrate;

[0014] Step S4: Place the glass sheet together with the metal nanoparticle-porous alumina array-PDMS composite layer in a vacuum drying oven, evacuate and heat to cure, and solidify the PDMS in the nanopores of the metal nanoparticle-porous alumina array to obtain an ultrasonic transmitter.

[0015] Preferably, in step S1, the thickness of the metal film is 50-120 nm. If the metal film is too thick or too thin, it will cause pore blockage and reduced light absorption. When the metal film is an aluminum film, the optimal aluminum film deposition rate is 0.05 nm / s, and the deposition time is controlled at 1000s to 2400s, among which a deposition time of 2000s has the best effect.

[0016] Preferably, in step S2, the stirring time is 1-30 min.

[0017] Preferably, in step S4, the vacuum heating time is 5-100 min, and the heating temperature is 60-120°C.

[0018] The present invention has the following beneficial effects: 1. By controlling the growth rate and time of physical vapor deposition, the thickness of the metal film and the depth, quantity, and diameter of the metal nanoparticles deposited within the pores can be controlled, resulting in a prepared metal nanoparticle-porous alumina array with a high light absorption coefficient. Excessively thick or thin metal films can lead to pore clogging and reduced light absorption. 2. The light absorption of the device is primarily concentrated on the metal nanoparticles within the alumina nanopores. Since the metal nanoparticles are adsorbed on the nanopore walls, the thermal conductivity of the metal is greater than that of the alumina. Therefore, heat conduction is primarily along the direction of the nanopore walls, giving the device anisotropic thermal conductivity. This orderly heat conduction causes the thermoelastic material to expand and contract only along the axial direction, effectively improving the photoacoustic conversion efficiency of the ultrasonic transmitter. 3. The thickness of the prepared metal nanoparticle-porous alumina array of the ultrasonic transmitter is 50-70 μm, and its cross-section can be laser cut to a size similar to the diameter of a multimode optical fiber, making it suitable for use in fiber-based ultrasonic transmitters, thus showing the potential for further miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1a Schematic diagram of the structure of the metal nanoparticle-porous alumina array of the present invention;

[0020] Figure 1b Schematic diagram of the cross-sectional structure of the photoultrasound transmitter of the present invention;

[0021] Figure 2 This is a spectrum absorption diagram of the aluminum nanoparticle-porous alumina array in an embodiment of the present invention.

[0022] Figure 3 This is an ultrasonic signal diagram obtained by testing an embodiment of the present invention;

[0023] Figure 4 This is a spectrum diagram of an ultrasonic signal obtained by testing an embodiment of the present invention;

[0024] Among them, 1 is a metal film, 2 is a porous alumina array, 3 is metal nanoparticles, 4 is polydimethylsiloxane, 5 is a metal nanoparticle-porous alumina array, and 6 is a transparent glass substrate. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to 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.

[0026] Example 1

[0027] A structure and preparation method of a photo-ultrasound emitter. The device is small in size and simple in structure. It generates high ultrasonic sound pressure, high frequency, wide bandwidth, and small divergence angle. The device is divided into a light absorption part and a thermal expansion part.

[0028] Composition and production process of light absorption part

[0029] like Figure 1a The light absorption part of the device is shown, namely the metal nanoparticle-porous alumina array 5, which includes a metal film 1, a symmetrical double-pass AAO nano template 2 of model DP450-300S-50000 produced by Shenzhen Topology Fine Membrane, and metal nanoparticles 3.

[0030] The preparation steps are as follows: an aluminum film is grown on the surface of porous anodized aluminum by physical vapor deposition, and aluminum nanoparticles are deposited in the pores. The anodized aluminum has a thickness of 60 μm, a pore diameter of 300 nm, a pore center spacing of 450 nm, and an aluminum film deposition rate of 0.05 nm / s. After 2000 s of deposition, the aluminum film thickness reaches 100 nm.

[0031] The spectral absorption range of the aluminum nanoparticle-aluminum oxide array 5 was tested using an integrating sphere. Figure 2 shown.

[0032] Thermal expansion material configuration process

[0033] The thermal expansion material is prepared by mixing polydimethylsiloxane and a curing agent. The preparation steps are as follows:

[0034] Take 5 g of polydimethylsiloxane and 0.5 g of curing agent Dow Corning 184, mix them and add them to a small beaker; stir them magnetically for 3 minutes to mix them thoroughly; and let the beaker stand until the bubbles dissipate.

[0035] Ultrasonic transmitter device manufacturing process

[0036] The cross-sectional structure diagram of the prepared ultrasonic transmitter device is shown in FIG. Figure 1b As shown, it includes polydimethylsiloxane (4), aluminum nanoparticle-porous alumina array 5 and transparent glass substrate 6. In the specific embodiment, K9 glass is used. The preparation steps are as follows:

[0037] 1) Immersing the aluminum nanoparticle-porous alumina array in a polydimethylsiloxane mixture;

[0038] 2) After the bubbles in the mixed solution completely dissipate, remove the aluminum nanoparticle-porous alumina array-PDMS composite layer;

[0039] 3) The soaked aluminum nanoparticle-porous alumina array-PDMS composite layer was placed on K9 glass and heated at 90°C for 30 minutes.

[0040] Ultrasonic test process and results of ultrasonic transmitter device

[0041] The prepared photoultrasonic emitter was placed in a quartz tank filled with water and irradiated with a nanosecond pulse laser. The specific nanosecond pulse laser wavelength was set to 532nm, the pulse width was 10 nanoseconds, and the repetition frequency was 100Hz. The ultrasonic signal was recorded using a hydrophone at a distance of 3 mm from the sample.

[0042] like Figure 3 and 4 As shown, at 1.13mj / cm 2 Under laser irradiation with an energy density of 100 nm, a sound intensity of 23.7 MPa and a bandwidth of -6 dB at 24 MHz were obtained.

[0043] The present invention provides a photo-induced ultrasonic transmitter and a method for manufacturing the same. The fabrication process is simple. By utilizing the photo-induced ultrasonic effect, a novel structure is provided, exhibiting anisotropic thermal conductivity. When a pulsed laser is applied to the ultrasonic transmitter, a high-intensity ultrasonic signal is generated.

Claims

1. A photo-ultrasound transmitter, comprising a transparent glass substrate, a light absorbing portion and a thermal expansion material, characterized in that: The light absorbing portion includes: a porous alumina array, a metal film, and metal nanoparticles; the metal film is a film layer deposited on the surface of the porous alumina array, and the thickness of the metal film is 50-120 nm; the metal nanoparticles are adsorbed on the nanopore walls of the porous alumina array, and the grain size ranges from 10-25 nm; the thermal expansion material is polydimethylsiloxane (PDMS), and the thermal expansion material is filled in the nanopores; The material of the metal film and the metal nanoparticles is aluminum; The center-to-center spacing of the pores of the porous alumina array is 450 nm, and the pore size is 250-350 nm.

2. The photoacoustic transmitter according to claim 1, wherein The thickness of the porous alumina array is 60 μm.

3. A method for manufacturing a photoultrasound transmitter, characterized in that: The manufacturing method includes: using a magnetron sputtering device to deposit a metal film on a double-pass porous anodic aluminum oxide array, self-assembling and depositing metal nanoparticles in the nanopores to form a metal nanoparticle-porous aluminum oxide array composite layer; immersing the prepared metal nanoparticle-porous aluminum oxide array composite layer in a PDMS solution, stirring and then allowing it to stand, and after the solution is fully immersed in the nanopores of the porous aluminum oxide, taking it out and placing it on a glass substrate; placing the glass-based metal nanoparticle-porous aluminum oxide array-PDMS composite layer in a vacuum drying oven, and after curing treatment, obtaining a photoultrasound emitter.

4. The method for manufacturing a photoultrasonic transmitter according to claim 3, wherein: The metal film is an aluminum film, and the deposition rate of the aluminum film is 0.05 nm / s, and the deposition time is 1000 s to 2400 s.

5. The method for manufacturing a photoultrasonic transmitter according to claim 4, wherein: The deposition time of the metal film is 2000s.

6. The method for manufacturing a photo-ultrasound transmitter according to claim 3, wherein: The stirring time is 1-30 min.

7. The method for manufacturing a photoultrasonic transmitter according to claim 3, wherein: The vacuum drying time is 5-100 minutes, and the drying temperature is 60-120°C.

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