Preparation method of photo-induced ultrasonic transducer based on RGO / PAN fiber membrane
RGO/PAN fiber membranes were prepared by electrospinning and physical vapor deposition, and combined with metal nanoparticles and PDMS. This solved the problems of insufficient selection and bonding tightness of light-absorbing materials in existing photo-induced ultrasonic transducers, and realized efficient and controllable ultrasonic generation, which broadened the bandwidth and intensity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-03-24
AI Technical Summary
Existing photo-induced ultrasound transducers suffer from problems such as the influence of light-absorbing material selection on ultrasonic intensity and bandwidth, insufficient bonding tightness leading to reduced sound pressure, and high cost and poor dispersibility of carbon nanotube materials, which limit their application in the biomedical field.
Reduced graphene oxide (RGO)-polyacrylonitrile (PAN) fiber membranes were prepared by electrospinning, and metal nanoparticles were deposited on them by physical vapor deposition. Combined with polydimethylsiloxane (PDMS) to form a composite layer, which constitutes a light absorption and thermal expansion material. The thickness of the fiber membrane and the distribution of metal nanoparticles were precisely controlled to form a photo-induced ultrasonic transducer.
It achieves high ultrasonic intensity, high frequency, and wide bandwidth, and is efficiently prepared under mild conditions, avoiding harsh conditions of high temperature and high pressure, thus improving photothermal conversion efficiency and transducer controllability.
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Figure CN121715314A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultrasonic technology, and in particular to a method for fabricating a photoinduced ultrasonic transducer based on an RGO / PAN fiber membrane. Background Technology
[0002] The working principle of piezoelectric ultrasonic transducers is based on the piezoelectric effect, which includes two main phenomena: first, the direct piezoelectric effect, where a piezoelectric material generates a potential difference under external force; and second, the inverse piezoelectric effect, where a piezoelectric material undergoes mechanical deformation under an applied electric field. The interaction of these two effects enables efficient conversion between electrical and acoustic energy. Although these transducers dominate many applications, they also face inherent challenges, such as large size, low operating frequency, high driving voltage, and susceptibility to electromagnetic interference. To overcome these limitations of traditional piezoelectric transducers, a novel photo-driven ultrasonic transducer has emerged. This transducer operates based on the photoacoustic effect, converting light energy into ultrasonic energy by irradiating a specific photoacoustic material with a laser, thus efficiently completing the light-heat-sound energy conversion process. Photo-driven ultrasonic transducers exhibit significant advantages, including high intensity, high frequency, and wide bandwidth of generated ultrasonic waves, along with strong resistance to electromagnetic interference and miniaturization. Based on these characteristics, photo-induced ultrasound transducers are expected to show great potential in the medical field, such as in advanced medical technologies like minimally invasive surgery, thrombolysis therapy, targeted drug delivery, and microfluidic injection.
[0003] Laser ultrasonic transducers are mainly composed of light-absorbing materials and thermally expanding materials. Among the many light-absorbing materials, common ones include carbon black, carbon nanotubes, and candle soot particles. Polydimethylsiloxane (PDMS), as a typical thermoelastic material, has a thermal expansion coefficient as high as 3.1 × 10⁻⁶. -4 K -1 It is 20 times stronger than metal, and its acoustic properties are well-matched with biological tissues. When a laser irradiates the light-absorbing material, the generated heat is transferred to the PDMS, which then generates ultrasound waves through the thermoelastic effect. In the design of most laser-ultrasonic transducers, the selection of the light-absorbing material is crucial because its absorption efficiency directly affects the intensity of the ultrasound waves. In addition, the tightness of the bond between the light-absorbing material and the thermally expanding material also affects the generated sound pressure; insufficient bonding will lead to a decrease in sound pressure. Therefore, developing a novel laser-ultrasonic transducer structure to enhance the intensity of ultrasound waves, broaden the bandwidth, and improve the photothermal conversion efficiency has become an urgent technical challenge.
[0004] In the work of RKPoduval, S. Noimark, RJ Colchester, et al. Optical fiber ultrasound transmitter with electrospun carbon nanotube-polymer composite[J]. Appl. Phys. Lett., 2017, 110(22): 223701, the photo-induced ultrasound transducer was prepared by electrospinning carbon nanotube-polyvinyl alcohol (PVA) fiber membrane and then cured by PDMS. However, carbon nanotubes have a wide length distribution and are prone to forming agglomerated bundles, resulting in poor controllability of their length and morphology. The preparation cost of high-purity, highly uniform carbon nanotubes has always been high, especially single-walled carbon nanotubes, whose mass production cost is much higher than that of traditional materials (such as carbon fiber and graphene), which to some extent limits their large-scale application. In addition, the nanoscale and high aspect ratio of carbon nanotubes give them a morphological feature similar to asbestos fibers. Once inside the body, they tend to accumulate in the lungs and cells, leading to inflammation, fibrosis, and even apoptosis. Their surface functional groups may also enhance biotoxicity, thus limiting their application in the biomedical field.
[0005] In the work of RJ Colchester, EJAlles, AEDesjardins. A directional fiber optic ultrasonic transmitter based on a reduced graphene oxide and polydimethylsiloxane composite[J]. Appl. Phys. Lett., 2019, 114(11): 113505, an RGO-PDMS fiber ultrasonic transducer was prepared by impregnation. In this method, the coating thickness is affected by the solution viscosity, impregnation time, and pulling rate, making it difficult to precisely control the thickness range. Furthermore, it is prone to non-uniform phenomena such as "roof-like" or "thick edges, thin center" coatings. In addition, the loading process of the impregnation method is constrained by factors such as substrate surface energy, solution diffusion rate, and component sedimentation, easily resulting in a "surface enrichment, internal depletion" situation. Active components tend to agglomerate into large particles, especially nanoscale active materials, and poor dispersibility directly reduces their utilization rate. Simultaneously, the loading amount is difficult to quantify precisely, resulting in poor repeatability. The maximum sound pressure generated by this transducer is only 1.7 MPa. Summary of the Invention
[0006] To overcome the shortcomings of the prior art, the present invention provides a method for fabricating a photo-induced ultrasonic transducer based on an RGO / PAN fiber membrane.
[0007] The technical solution of this invention to solve the technical problem is as follows:
[0008] This invention discloses a method for fabricating a photoinduced ultrasonic transducer based on an RGO / PAN fiber membrane. The transducer comprises a composite layer of metal nanoparticles, reduced graphene oxide (RGO), polyacrylonitrile (PAN), and polydimethylsiloxane (PDMS) cured on transparent quartz glass. The metal nanoparticle-RGO-PAN fiber membrane serves as the light-absorbing layer, and PDMS serves as the thermal expansion material. The fabrication method is as follows: First, a graphene oxide (GO)-polyacrylonitrile fiber membrane is prepared by electrospinning, followed by reduction treatment with vitamin C in a water bath to obtain an RGO-PAN fiber membrane. Next, the RGO-PAN fiber membrane is dried, and a layer of metal nanoparticles is deposited on its surface using physical vapor deposition, thereby obtaining an RGO-PAN fiber membrane containing metal nanoparticles. Finally, the metal nanoparticle-RGO-PAN-PDMS fiber membrane is placed in a vacuum drying oven for curing treatment, thus obtaining the photoinduced ultrasonic transducer.
[0009] The optical-ultrasonic transducer prepared in this invention, when in operation, the incident laser pulse is absorbed by the metal nanoparticle-RGO-PAN composite layer and converted into heat, and ultrasound is generated by utilizing the thermoelastic effect of PDMS.
[0010] Furthermore, the method for fabricating the photoinduced ultrasonic transducer specifically includes the following steps:
[0011] 1) Graphene oxide (GO)-polyacrylonitrile (PAN) fiber membranes were prepared using electrospinning technology. The thickness of the fiber membrane was precisely controlled by adjusting the spinning time and the amount of solution. The GO-PAN fiber membranes were then dried in an oven.
[0012] 2) The GO-PAN fiber membrane is immersed in a vitamin C aqueous solution and subjected to water bath heating treatment. After a reduction reaction, an RGO-PAN composite membrane is obtained, which is then dried again.
[0013] 3) Metal nanoparticles were further grown on the surface of the RGO-PAN composite membrane using physical vapor deposition to obtain a metal nanoparticle-RGO-PAN fiber membrane. RGO was attached to the fiber surface, and the RGO-PAN-PDMS fiber membrane was black.
[0014] 4) Spin-coat a layer of PDMS approximately 10-100 μm thick onto the metal particle side of the metal nanoparticle-RGO-PAN fiber membrane, and then tightly adhere it to the quartz glass. Carefully remove any air bubbles trapped in the middle to ensure there are no gaps between the fiber membrane and the quartz glass. Next, spin-coat a layer of PDMS approximately 10-100 μm thick onto the other side of the fiber membrane to ensure that the PDMS is uniformly covered on the surface of the fiber membrane.
[0015] 5) The metal nanoparticle-RGO-PAN-PDMS composite layer, together with the quartz glass, is placed in a vacuum drying oven and heated and cured in a vacuum environment to obtain the photo-induced ultrasonic transducer.
[0016] Furthermore, in step 1), the voltage for electrospinning is controlled at 15-25kV; the distance from the needle to the receiving plate is 10-20cm; the feed rate of the electrospinning liquid is 0.5-1mL / h; the ambient temperature is 20-30℃; the relative humidity is 20-30%; the spinning time is 1-3h; and the volume of the spinning solution is 1-3mL.
[0017] Furthermore, in step 1), the GO content in the fiber membrane is 50-300 mg, and the thickness is 3-50 μm.
[0018] Furthermore, in step 2), the water bath heating temperature is 80-95℃, and the time is 1-3h.
[0019] Furthermore, in step 3), the metal nanoparticles can be gold or silver, with a size of 8-30 nm.
[0020] Furthermore, in step 4), during the preparation of PDMS, the main agent and auxiliary agent are mixed in a beaker at a mass ratio of 10:1 and magnetically stirred. The mixture is then placed in a vacuum chamber and allowed to stand until all air bubbles in the PDMS mixture completely dissipate. Preferably, the stirring time is 5-30 minutes.
[0021] Furthermore, in step 5), the vacuum heating time is 20-120 minutes and the heating temperature is 80-120°C.
[0022] The present invention has the following technical effects:
[0023] 1. In this invention, by precisely controlling the duration of the electrospinning process and the amount of solution used, the thickness of the GO-PAN fiber membrane can be effectively adjusted to achieve the best ultrasonic effect. Graphene oxide (GO) particles are uniformly distributed on the surface of polyacrylonitrile (PAN) fibers. After reduction treatment, they are transformed into reduced graphene oxide (RGO) with superior conductivity. The RGO-PAN fiber membrane exhibits excellent light absorption capabilities.
[0024] 2. The micropores between the fibers produced by electrospinning provide space for the growth of metal nanoparticles. These metal particles can adhere to the fibers, and the localized plasmon resonance effect of the metal nanoparticles can significantly improve the efficiency of light-to-heat energy conversion. Furthermore, the micropores between the fibers can increase the incorporation of PDMS and ensure sufficient contact between the light-absorbing material and PDMS.
[0025] 3. The size and shape of the transducer are well controllable. A single fiber membrane can be used to manufacture multiple transducers of different sizes to meet various application requirements.
[0026] 4. The reaction method of the present invention can be carried out efficiently under mild conditions without relying on harsh conditions such as high temperature and high pressure. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the ultrasonic transducer in this invention.
[0028] Figure 2 This is a SEM microstructure image of the reduced graphene oxide-polyacrylonitrile fiber membrane in this invention.
[0029] Figure 3 The average light absorption rate of RGO-PAN-PDMS with a spinning amount of 3 mL in Comparative Example 1 of this invention was obtained by testing at wavelengths of 300-2500 nm.
[0030] Figure 4 The image shows the ultrasonic pressure signal obtained by testing RGO-PAN-PDMS with different spinning amounts at 18mJ laser energy in Comparative Example 1 of this invention.
[0031] Figure 5 The image shows the ultrasonic pressure signal obtained by testing Au-RGO-PAN-PDMS with a spinning amount of 3 mL under different laser energies in Example 1 of this invention.
[0032] Figure 6 This is a comparison of the ultrasonic signal intensity of two transducers, RGO-PAN-PDMS and Au-RGO-PAN-PDMS, with a spinning amount of 3 mL in Example 1 and Comparative Example 1 of the present invention, under 18 mJ laser energy.
[0033] Figure 7 This is a comparison of the spectrum of ultrasonic signals obtained from tests of two transducers in Embodiment 1 and Comparative Example 1 of the present invention.
[0034] Figure 1 In the diagram, 1 is PDMS, 2 is reduced graphene oxide-polyacrylonitrile fiber membrane, 3 is metal nanoparticles, and 4 is quartz glass substrate. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments.
[0036] Example 1
[0037] This invention discloses a photo-induced ultrasonic transducer based on RGO / PAN fiber membrane and its manufacturing method. The transducer has the advantages of small size and simple structure, and can generate ultrasonic waves with low attenuation, high frequency and wide bandwidth.
[0038] This device consists of a light absorption section and a thermal expansion section. A schematic diagram of its cross-sectional structure is shown below. Figure 1 As shown, the light-absorbing part of the device includes metal nanoparticles (3) and an RGO / PAN fiber membrane (2). Its preparation steps are as follows:
[0039] GO / PAN fiber membranes were prepared using electrospinning technology. 300 mg of graphene oxide (GO) was added to 10 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute in an ultrasonic cell disruptor. Then, 1000 mg of polyacrylonitrile (PAN) was added to the solution, and the mixture was stirred continuously at room temperature for 12 h to obtain a precursor solution. 3 mL of the precursor solution was drawn using a syringe with the needle 15 cm from the receiving plate and a feed rate of 1 mL / h. Electrospinning was performed under 15 kV high voltage conditions at an ambient temperature of 25 °C and a relative humidity of 30% for 3 h. The resulting GO / PAN fiber membrane was then dried in an oven at 80 °C for 8 h. Subsequently, the fiber membrane was placed in a vitamin C aqueous solution and reduced by heating in a 95 °C water bath for 3 h. It was then dried again in an oven at 80 °C for 8 h to obtain the RGO-PAN fiber membrane. We obtained the microstructure of the RGO / PAN fiber membrane through scanning electron microscopy (SEM) analysis, such as... Figure 2 As shown in the figure, reduced graphene oxide (RGO) particles are clearly attached to the surface of polyacrylonitrile (PAN) fibers. Finally, we successfully grew gold nanoparticles with a size of approximately 8-30 nm in the pores of the fiber membrane using physical vapor deposition (PVD). This resulted in the fabrication of an RGO-PAN fiber membrane containing metal nanoparticles.
[0040] The thickness of the RGO / PAN fiber membrane is 30 μm.
[0041] The flow rate of the electrospinning liquid is 1 mL / h.
[0042] The concentration of vitamin C aqueous solution is 3g / 150mL.
[0043] The growth rate of gold nanoparticles was 0.13 nm / s.
[0044] The thermally expandable PDMS is obtained by mixing the main agent and auxiliary agent in a mass ratio of 10:1, and its preparation steps are as follows:
[0045] Mix 10 grams of the main agent with 1 gram of the auxiliary agent, then add the mixture to a beaker and stir with a magnetic stirrer for 20 minutes to ensure that the two components are fully combined. Afterward, place the mixture in a vacuum chamber for vacuum treatment and allow it to stand until the air bubbles completely dissipate.
[0046] The Au-RGO-PAN fiber membrane was then cured onto quartz glass (4). The preparation steps are as follows:
[0047] 1) A 10μm PDMS layer was spin-coated onto an Au-RGO-PAN fiber membrane containing metal particles.
[0048] 2) Attach the Au-RGO-PAN fiber membrane to the cleaned quartz glass, and gently scrape off any air bubbles in the middle with tweezers to ensure that there are no gaps between the fiber membrane and the quartz glass.
[0049] 3) Spin-coat 100 μm of PDMS onto the other side of the fiber membrane.
[0050] 4) The prepared Au-RGO-PAN-PDMS composite layer was dried in a vacuum drying environment at 80℃ for 2 hours.
[0051] Comparative Example 1
[0052] The preparation method is basically the same as that in Example 1, except that:
[0053] 1) The amount of spinning solution was 1 ml, 2 ml, and 3 ml, respectively; this was repeated three times.
[0054] 2) The phrase "Gold nanoparticles were successfully grown in the pores of the fiber membrane using physical vapor deposition (PVD) technology" in Example 1 is omitted.
[0055] An RGO-PAN-PDMS transducer without gold nanoparticles was prepared.
[0056] The prepared laser ultrasonic transducer was immersed in a quartz water tank filled with water, and then irradiated with a nanosecond-level pulsed laser (wavelength 532nm, pulse width 10 nanoseconds, repetition frequency 100Hz). Sound pressure signals were captured using a hydrophone at a distance of 1mm from the sample.
[0057] like Figure 3As shown, the RGO-PAN-PDMS transducer prepared in Comparative Example 1 with a spinning amount of 3 mL has an average light absorption rate of approximately 90% in the wavelength range of 300-2500 nm.
[0058] like Figure 4 As shown, when the spinning amount is 3 mL, the ultrasonic signal intensity generated by the RGO-PAN-PDMS transducer in Comparative Example 1 reaches its maximum; when the spinning amount exceeds 3 mL, the transducer cannot generate an ultrasonic signal.
[0059] like Figure 5 As shown, when the laser energy is 18mJ, the sound pressure generated by the Au-RGO-PAN-PDMS transducer with a spinning amount of 3mL in Example 1 reaches its strongest.
[0060] like Figure 6 , 7 As shown, at a laser energy of 18 mJ, the RGO-PAN-PDMS transducer with a 3 mL spinning amount in Example 1 achieved an acoustic intensity of 1.7 MPa and a bandwidth of 5 MHz (-6 dB); while the Au-RGO-PAN-PDMS transducer with a 3 mL spinning amount achieved an acoustic intensity of 3.2 MPa and a bandwidth of 8 MHz (-6 dB). Based on this, it can be calculated that the acoustic intensity of the Au-RGO-PAN-PDMS transducer is 1.88 times that of the RGO-PAN-PDMS transducer, and its bandwidth (-6 dB) is 1.6 times that of the latter.
[0061] This invention discloses a simple and efficient manufacturing process for a laser ultrasonic transducer. By utilizing the photo-induced ultrasound effect, this invention proposes an innovative structural design for a laser ultrasonic transducer, which exhibits low ultrasonic attenuation rate and high ultrasonic conversion efficiency.
[0062] The above are merely embodiments of the present invention and do not limit the scope of the patent. Any equivalent modifications made based on the content of this specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.
Claims
1. A method for fabricating a photoinduced ultrasonic transducer based on an RGO / PAN fiber membrane, characterized in that, The transducer consists of a composite layer of metal nanoparticles, reduced graphene oxide (RGO), polyacrylonitrile (PAN), and polydimethylsiloxane (PDMS) solidified on transparent quartz glass. The metal nanoparticle-RGO-PAN fiber membrane serves as the light-absorbing layer, and PDMS acts as the thermal expansion material. The photo-induced ultrasonic transducer is prepared as follows: First, a graphene oxide (GO)-polyacrylonitrile fiber membrane is prepared by electrospinning, followed by reduction treatment with vitamin C in a water bath to obtain an RGO-PAN fiber membrane. Next, the RGO-PAN fiber membrane is dried, and a layer of metal nanoparticles is deposited on its surface using physical vapor deposition, thus obtaining an RGO-PAN fiber membrane containing metal nanoparticles. Finally, the metal nanoparticle-RGO-PAN-PDMS fiber membrane is placed in a vacuum drying oven for curing, thereby obtaining the photo-induced ultrasonic transducer.
2. The method for fabricating a photoinduced ultrasonic transducer according to claim 1, characterized in that, Specifically, the following steps are included: 1) Graphene oxide (GO)-polyacrylonitrile (PAN) fiber membranes were prepared using electrospinning technology; the thickness of the fiber membrane was precisely controlled by adjusting the spinning time and the amount of solution; the GO-PAN fiber membranes were then dried in an oven. 2) The GO-PAN fiber membrane is immersed in a vitamin C aqueous solution and subjected to water bath heating treatment. After a reduction reaction, an RGO-PAN composite membrane is obtained, which is then dried again. 3) Metal nanoparticles were further grown on the surface of the RGO-PAN composite membrane using physical vapor deposition to obtain a metal nanoparticle-RGO-PAN fiber membrane. 4) Spin-coat a layer of PDMS of about 10-100 μm on one side of the metal particles of the metal nanoparticle-RGO-PAN fiber membrane, and then attach it tightly to the quartz glass; then spin-coat a layer of PDMS of about 10-100 μm on the other side of the fiber membrane to ensure that the PDMS is uniformly covered on the surface of the fiber membrane. 5) The metal nanoparticle-RGO-PAN-PDMS composite layer, together with the quartz glass, is placed in a vacuum drying oven and heated and cured in a vacuum environment to obtain the photo-induced ultrasonic transducer.
3. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 1), the voltage for electrospinning is controlled at 15-25kV; the distance from the needle to the receiving plate is 10-20cm; the feed rate of the electrospinning liquid is 0.5-1mL / h; the ambient temperature is 20-30℃; the relative humidity is 20-30%; the spinning time is 1-3h; and the volume of the spinning solution is 1-3mL.
4. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 1), the GO content in the fiber membrane is 50-300 mg, and the thickness is 3-50 μm.
5. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 2), the water bath heating temperature is 80-95℃ and the time is 1-3h.
6. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 3), the metal nanoparticles can be gold or silver, with a size of 8-30 nm.
7. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 4), when preparing PDMS, the main agent and auxiliary agent are mixed in a beaker at a mass ratio of 10:1 and magnetically stirred; then the mixture is placed in a vacuum chamber and left to stand until the bubbles in the PDMS mixture completely dissipate.
8. The method for fabricating a photoinduced ultrasonic transducer according to claim 2, characterized in that, In step 5), the vacuum heating time is 20-120 minutes and the heating temperature is 80-120℃.