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CN-121610035-B - Preparation method of silicon dioxide-epoxy resin composite material, ultrasonic transducer, preparation process of ultrasonic transducer and imaging system

CN121610035BCN 121610035 BCN121610035 BCN 121610035BCN-121610035-B

Abstract

The invention discloses a preparation method of a silicon dioxide-epoxy resin composite material, which controls the acoustic impedance of the composite material by adjusting the volume fraction of the silicon dioxide-epoxy resin composite material, an ultrasonic transducer prepared by using the composite material and a preparation process thereof, and an imaging system designed by using the ultrasonic transducer. By designing the matching layer and the backing layer with specific acoustic impedance, seamless fusion of ultrasonic imaging and photoacoustic imaging is realized, and the transducer has ultrahigh sensitivity, broadband characteristic and high optical transparency, shows bimodal imaging capability with high contrast and high resolution, and solves the problem of insufficient acoustic performance of the traditional transparent ultrasonic transducer.

Inventors

  • LI XIANGPENG
  • HUANG RENQIANG
  • ZHANG WENKAI
  • CHEN XUANHAN
  • SUN LINING

Assignees

  • 苏州大学

Dates

Publication Date
20260512
Application Date
20260202

Claims (7)

  1. 1. The preparation method of the silicon dioxide-epoxy resin composite material is characterized by comprising the following steps: (1) Mixing silica micropowder and silica nanopowder serving as ceramic filler with an epoxy resin matrix to prepare ceramic-epoxy resin composite slurry with various volume fractions V; (2) Calculating according to the volume fraction of the ceramic-epoxy resin composite slurry prepared in the step (1) to obtain corresponding acoustic impedance Z, and fitting to form a theoretical curve about the volume fraction V of the ceramic-epoxy resin composite slurry and the acoustic impedance Z; (3) According to the theoretical curve obtained in the step (2), a volume fraction value corresponding to the acoustic impedance value of the silicon dioxide-epoxy resin composite material to be prepared is obtained, positive and negative scaling is carried out on the volume fraction value, and a volume fraction interval value is formed; (4) Preparing ceramic-epoxy resin composite sizing agents with different volume fractions by taking a set value as gradient in the volume fraction interval value in the step (3), preparing corresponding silicon dioxide-epoxy resin composite chips by utilizing each ceramic-epoxy resin composite sizing agent, measuring the round trip propagation time t of ultrasound in the chips through an ultrasonic transducer and a pulse receiver, and calculating the actual longitudinal sound velocity by combining the chip thickness d Simultaneously measuring the weight m and the volume of the chip Calculating the actual density Finally pass through Obtaining the actual acoustic impedance value ; (5) When the actual acoustic impedance value in the step (4) is consistent with the acoustic impedance value of the silicon dioxide-epoxy resin composite material to be prepared, obtaining the actual volume fraction V of the corresponding ceramic-epoxy resin composite slurry, and preparing the corresponding ceramic-epoxy resin composite material according to the volume fraction V; in the step (2), the acoustic impedance Z of the ceramic-epoxy composite slurry is determined by the longitudinal sound velocity C L and the density ρ, and the formula is: Z = C L *ρ; Wherein the density of the ceramic-epoxy composite paste follows the law of mixing, i.e Wherein For the density of the epoxy resin matrix, Is the density of the silica filler; the longitudinal sound velocity C L is determined by the bulk modulus K and the shear modulus G of the composite slurry, and the formula is as follows: ; Wherein K and G are calculated by Dewar model: ; ; In the middle of Is the bulk modulus of epoxy resin, Is the shear modulus of epoxy resin, Is the bulk modulus of silicon dioxide, Is the shear modulus of silica; substituting the specific volume fraction value of the ceramic-epoxy resin composite slurry prepared in the step (1) into the formula, calculating to obtain the corresponding acoustic impedance Z, and fitting to form a theoretical curve about the volume fraction V of the ceramic-epoxy resin composite slurry and the acoustic impedance Z.
  2. 2. The method of claim 1, wherein in the step (5), in order to meet the viscosity requirement of the composite slurry, the viscosity of the composite slurry corresponding to the determined volume fraction V of the ceramic-epoxy resin composite slurry is calculated: (a) Preparing a plurality of ceramic-epoxy resin composite slurries with different volume fractions V, dividing the ceramic-epoxy resin composite slurries into three groups of samples with low volume fraction, medium volume fraction and high volume fraction, uniformly stirring each sample, degassing, and measuring the viscosity of the composite slurry of each sample , (B) Calculation of silica intrinsic viscosity : ; Wherein, the Substituting the volume fraction of the low volume fraction array sample for the viscosity of the pure epoxy resin matrix, and obtaining the viscosity by taking the average value ; (C) The viscosity value of the composite sizing agent, the viscosity of the pure epoxy resin matrix, measured by all the samples with different volume fractions in the step (a) And silica intrinsic viscosity Crigex-doherty model: ; and calculating to obtain corresponding volume fractions Theoretical value, least square fitting is adopted to find one A value that minimizes the sum of squares of deviations of the theoretical viscosity calculated by the model and the measured viscosity measured with the rheometer; (d) Substituting the volume fraction V of the ceramic-epoxy composite paste determined in step (5) into a kriging-doherty model: ; and calculating the viscosity of the ceramic-epoxy resin composite slurry for obtaining the volume fraction And determining the viscosity value Whether the viscosity requirements in the preparation of the ultrasonic transducer are met.
  3. 3. An ultrasonic transducer based on a silica-epoxy composite material, comprising a stack and a housing (60), between which the transparent polyurethane resin is filled, characterized in that the stack comprises: A piezoelectric crystal (10), wherein the piezoelectric crystal (10) is a lithium niobate crystal sputtered by indium tin oxide; The transparent electrode layer is sputtered on the front side and the back side of the piezoelectric crystal (10), and is an indium tin oxide layer; a front matching layer (20) and a back matching layer (30) which are arranged outside the transparent electrode layers on the front and back sides of the piezoelectric crystal (10); the transparent back lining layer (50) is of a double-layer structure, has acoustic impedance of 4-6 MRayl and is made of a silicon dioxide-epoxy resin composite material; wherein the front side matching layer (20) comprises a first matching layer (21) with acoustic impedance of 7 MRayl-9 Mrayl and a second matching layer (22) with acoustic impedance of 2 MRayl-3 Mrayl, and the back side matching layer (30) has acoustic impedance of 3.5 MRayl-4 Mrayl; and the first matching layer (21), the second matching layer (22) and the back matching layer (30) are all manufactured by the manufacturing method of the silicon dioxide-epoxy resin composite material according to claim 1 or 2; The optical transmittance of the first matching layer (21), the second matching layer (22), the back matching layer (30) and the transparent back layer (50) meets the requirement that the visible light area is more than or equal to 90 percent and the near infrared area is more than or equal to 95 percent; The first matching layer (21) is 7.5 MRayl in acoustic impedance and 31 in thickness, is prepared by compounding ceramic filler and epoxy resin, wherein the ceramic filler is composed of silica micropowder with the particle size of 3 microns and nano powder with the particle size of 15nm according to the mass ratio of 9:1, the volume fraction of the ceramic filler is 0.49, the second matching layer (22) is 2.4: 2.4 MRayl in acoustic impedance and 18 microns in thickness, the ceramic filler is prepared by compounding silica-epoxy resin materials, the volume fraction of the ceramic filler is 0.25, the acoustic impedance of the back matching layer (30) is 3.8MRayl and 25 microns in thickness, the ceramic filler is prepared by compounding ceramic filler composed of silica micropowder with the particle size of 3 microns and nano powder with the particle size of 30nm according to the mass ratio of 95:5, the volume fraction of the ceramic filler is 0.38, the upper layer acoustic impedance of the transparent backing layer (50) is 4.2 MRayl, the lower layer acoustic impedance is 5.8 MRayl, the two layers are 50 microns in thickness, and the corresponding ceramic filler volume fractions are 0.4 and 0.43.
  4. 4. An ultrasonic transducer according to claim 3 wherein the stack is held in a housing (60) and the coaxial cable is connected by conductive epoxy, the housing (60) being grounded on the front side to the piezoelectric crystal (10) and the signal conductors on the back side.
  5. 5. An ultrasound transducer according to claim 4, wherein the viscosity of the silica-epoxy composite of the first matching layer (21), the second matching layer (22) and the backside matching layer (30) is between 80-100 McPs.
  6. 6. A process for preparing an ultrasonic transducer according to any one of claims 3 to 5, comprising the steps of: taking the lithium niobate crystal sputtered by indium tin oxide as a piezoelectric crystal, sequentially coating two layers of composite slurry on the front surface of the piezoelectric crystal, solidifying and grinding to a set thickness, and taking the front surface as a front surface matching layer; coating composite slurry on the back of the piezoelectric crystal as a back matching layer; Coating a backing layer material outside the back matching layer to form a stacked body, and vacuum degassing for 30 minutes to avoid interlayer bubbles; Four corners of the front matching layer and the back matching layer are removed, and the electrode layer of the piezoelectric crystal is connected with the coaxial cable, so that the conductive path is ensured to be free from shielding; and filling a gap between the shell and the stacking body with transparent polyurethane resin to complete the whole package.
  7. 7. An imaging system, characterized by comprising a collimator (1) and an imaging head, wherein, The imaging head comprising two angularly adjustable silver mirrors (2), a right angle prism mirror (3) and two parabolic mirrors (4), the imaging head further comprising an ultrasonic transducer according to any one of claims 3-5; The two angle-adjustable silver film reflectors (2) are positioned below the collimator (1), the right-angle prism reflector (3) is positioned below the two angle-adjustable silver film reflectors (2), the ultrasonic transducer is positioned between the two parabolic reflectors (4), the acoustic center of the ultrasonic transducer coincides with the optical axis of the parabolic reflectors, and the laser beam can vertically penetrate the ultrasonic transducer and then is incident to the parabolic reflectors.

Description

Preparation method of silicon dioxide-epoxy resin composite material, ultrasonic transducer, preparation process of ultrasonic transducer and imaging system Technical Field The invention relates to a preparation method of a silicon dioxide-epoxy resin composite material, an ultrasonic transducer, a preparation process of the ultrasonic transducer and an imaging system, and belongs to the technical field of transparent ultrasonic transducers. Background The ultrasonic imaging takes the important place for a long time in the fields of clinical diagnosis, biomedical research and the like by virtue of the core advantages of simple operation, high safety, controllable cost and deep penetration depth, while the optical imaging technology, including photoacoustic imaging PAI, optical coherence tomography OCT, fluorescent imaging FLI and the like, can accurately capture molecular level information of biological tissues with the characteristics of high specificity and high resolution, and the two technologies are fused into the key direction for improving the sensitivity and specificity of disease diagnosis, namely by the short plate with complementary single mode, the deep penetration advantage of ultrasonic imaging is reserved, the accurate positioning and the qualitative of focus are realized by virtue of the high specificity of optical imaging, and the ultrasonic imaging method is particularly suitable for complex scenes such as early disease screening, dynamic monitoring and the like. However, the fusion requirement is limited by the technical bottleneck of a core device for a long time, the traditional imaging system is difficult to simultaneously realize the dual aims of 'seamless integration' and 'optimal bimodal performance', if a separated design is adopted, the independent arrangement of ultrasonic and optical components can lead to complex system structure and huge volume, the coaxial calibration difficulty of an optical channel and an ultrasonic channel is high, the imaging precision is influenced, the imaging precision is difficult to adapt to miniaturized application scenes such as in-vivo imaging and minimally invasive diagnosis and treatment, and if the integration is realized through a transparent component, the performance defect of an early related device can seriously compromise the overall effect, so that the practical value of fusion imaging is greatly reduced. Before the development of the novel transparent ultrasonic transducer, the ultrasonic transducer in the industry is divided into two large camps for a long time, and the two types of traditional ultrasonic transducers are introduced below, wherein the limitations which cannot be broken through exist in the two types of ultrasonic transducers: Firstly, the traditional opaque ultrasonic transducer has mature acoustic performance, and good acoustic impedance matching is realized through the matching layer and the backing layer constructed by the metal-epoxy resin composite material, so that the traditional opaque ultrasonic transducer is stable in performance on core indexes such as bandwidth, signal transmission efficiency, sensitivity and the like, and can meet the requirement of conventional single-mode ultrasonic imaging. The optical imaging system has the defects that the opaque structure can block light transmission, cannot be seamlessly integrated with optical modes such as optoacoustic, fluorescence and the like, limits the development of multi-mode imaging, and needs to additionally design an optical channel, so that the imaging system has huge volume and complex structure, and is difficult to adapt to miniaturized and in-vivo imaging scenes. Second, the Transparent Ultrasonic Transducer (TUT) that was explored earlier was designed to achieve the dual function of "ultrasonic sound-optical penetration" by using a transparent piezoelectric crystal (e.g., lithium niobate), a transparent polymer, or a ceramic-polymer composite material instead of a metal component, in combination with a transparent Indium Tin Oxide (ITO) electrode. The front end matching layer has acoustic impedance of 2-3 MRayl (far lower than ideal 7-9 MRayl), the backing layer has impedance of less than 5 MRayl, so that the acoustic wave transmission efficiency is low, the residual vibration is serious, the bandwidth is narrow, the peak voltage is low, the signal attenuation is fast, the imaging resolution and the penetration depth are obviously inferior, gaps exist between all layers or the bonding is unstable, the acoustic transmission continuity is damaged, and the quality and the stability of the transducer are further reduced. Disclosure of Invention The ultrasonic transducer based on the silicon dioxide-epoxy resin composite material, the preparation process and the imaging system thereof realize seamless fusion of ultrasonic imaging and photoacoustic imaging by designing a matching layer and a backing layer of specific acoustic impedance, and the transducer