CN116836412A - A double negative acoustic metagel material and its preparation method and application - Google Patents

Abstract

The invention provides a double negative acoustic superstructural gel material and its preparation method and application, and belongs to the technical field of functional materials. The present invention prepares a gas-in-water-in-oil emulsion based on a gas phase, a water phase and an oil phase. The gas-in-water-in-oil emulsion includes an oil phase and gas-in-water microspheres dispersed in the oil phase; the oil-in-water emulsion is removed The oil phase in the air-in-water emulsion is then mixed with the obtained air-in-water microspheres and the composite hydrogel solution to obtain a 3D printing ink; the 3D printing ink is sequentially subjected to 3D extrusion printing and physical gelation to obtain a double negative Acoustic metagel materials. The present invention prepares a double-negative acoustic supergel material based on microfluidic and 3D printing technology, which can accurately control the shape, size and distribution of microspheres. The finally prepared double-negative acoustic supergel material can be applied at ultrasonic imaging frequencies. Within the range (0.5~15MHz).

Description

A double negative acoustic metagel material and its preparation method and application

Technical field

The present invention relates to the technical field of functional materials, and in particular to a double negative acoustic superstructure gel material and its preparation method and application.

Background technique

Acoustic metamaterial is an artificial structural material. By artificially designing the structure of the material, it behaves as a material with special acoustic properties as a whole, such as negative refraction, acoustic stealth, extraordinary transmission, sub-wavelength imaging, etc. Currently, soft acoustic metamaterials have attracted widespread attention from researchers. Existing soft acoustic metamaterials are mainly prepared through traditional methods such as emulsion polymerization, dispersion polymerization, and suspension polymerization. They use the difference in mechanical properties between the dispersed phase and the matrix to achieve negative equivalent acoustic parameters, such as negative equivalent mass density parameters and Negative equivalent elastic modulus parameter (Brunet, T., et al., Sharpacoustic multipolar-resonances in highly monodisperseemulsions. Applied Physics Letters, 2012.101(1):p.011913.; Brunet, T., et al., Soft3Dacousticmetamaterial with negative index. NatureMaterials, 2015.14(4) :p.384-388.; Brunet, T., J. Leng, and O. Mondain-Monval, SoftAcoustic Metamaterials. Science, 2013.342(6156): p.323-324.). However, these methods usually produce microspheres with poor polydispersity, poor reproducibility, and poor tunable morphology. The soft acoustic metamaterials finally prepared have larger microbubbles with an average radius of 160 μm, and mainly use low-sounding materials. Silica gel microspheres are used to prepare soft acoustic metamaterials, which results in them only working in the low frequency range (50-500kHz).

Contents of the invention

The purpose of the present invention is to provide a double negative acoustic supergel material and its preparation method and application. The method of the present invention can accurately control the shape, size and distribution of microspheres, and the final double negative acoustic supergel material can Applied in the ultrasonic imaging frequency range (0.5 ~ 15MHz).

In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

The invention provides a method for preparing a double negative acoustic superstructure gel material, which includes the following steps:

A gas-in-water-in-oil emulsion is prepared based on the gas phase, water phase and oil phase, and the gas-in-water-in-oil emulsion includes an oil phase and gas-in-water microspheres dispersed in the oil phase;

Remove the oil phase in the air-in-water-in-oil emulsion, and then mix the obtained air-in-water microspheres with the composite hydrogel solution to obtain a 3D printing ink;

The 3D printing ink is sequentially subjected to 3D extrusion printing and physical gelation to obtain a double negative acoustic superstructure gel material.

Preferably, the gas phase includes air, nitrogen or inert gas;

The aqueous phase includes a first gel material and water, and the first gel material includes chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methacrylic acid acylated gelatin;

The oil phase includes silicone oil.

Preferably, the water-in-oil and gas-in-oil emulsion is prepared in a multiphase flow microfluidic system;

The multi-phase flow microfluidic system includes a tubular main body. Along the material flow direction, the tubular main body is provided with a gas phase inlet, a water phase inlet and an oil phase inlet in sequence. The tubular main body is provided with a gas phase inlet connected to the oil phase inlet. Oil phase microchannel, the oil phase microchannel is provided with a water phase microchannel connected to the water phase inlet, and the water phase microchannel is provided with a gas phase microchannel connected to the gas phase inlet; wherein, the gas phase microchannel The radii of the water phase microchannel and the oil phase microchannel are in the range of 5 to 500 μm, and the radius of the gas phase microchannel is smaller than the radius of the water phase microchannel, and at the same time, the radius of the water phase microchannel is smaller than the radius of the oil phase microchannel. radius;

When preparing the gas-in-water-in-oil emulsion, the flow rates of the gas phase, water phase and oil phase are independently 1 to 10 μL/min.

Preferably, the radius of the water-in-air microspheres is 15 to 50 μm.

Preferably, the composite hydrogel solution includes a second gel material, an auxiliary curing material and water; the concentration of the second gel material in the composite hydrogel solution is 10 to 20 wt%, and the concentration of the auxiliary curing material is 1～5wt%.

Preferably, the second gel material includes chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methacrylate acylated gelatin, and the auxiliary curing material includes carrageenan, gelatin or agar. .

Preferably, the volume fraction of water-in-air microspheres in the 3D printing ink is 5 to 40%.

Preferably, the 3D extrusion printing is performed at room temperature, and the operating conditions of the 3D extrusion printing include: the needle extrusion speed is 0.1~1mm/s, the needle moving speed is 0.1~1mm/s; the printing line spacing <1mm, printing thickness is 1~3mm, printing width is 4~6mm.

The present invention provides a double negative acoustic superstructural gel material prepared by the preparation method described in the above technical solution, including a gel matrix material and hollow microbubbles distributed in the gel matrix material. The radius of the hollow microbubbles is It is 15~50μm.

The present invention provides the application of the double-negative acoustic superstructural gel material described in the above technical solution in the preparation of ultrasonic penetrating imaging preparations. Suitable high-acoustic impedance media for the ultrasonic penetrating imaging preparations include muscles or skulls.

The invention provides a method for preparing a double negative acoustic superstructural gel material, which includes the following steps: preparing a water-in-oil gas-in-oil emulsion based on a gas phase, a water phase and an oil phase, and the oil-in-water gas-in-oil emulsion includes an oil phase. with air-in-water microspheres dispersed in the oil phase; removing the oil phase in the air-in-water-in-oil emulsion, and then mixing the obtained air-in-water microspheres with the composite hydrogel solution to obtain a 3D printing ink; The 3D printing ink is sequentially subjected to 3D extrusion printing and physical gelation to obtain a double negative acoustic superstructure gel material. The present invention prepares a double-negative acoustic supergel material based on microfluidic and 3D printing technology, and can accurately control the shape, size and distribution of microspheres. The finally prepared double-negative acoustic supergel material can be applied at ultrasonic imaging frequencies. Within the range (0.5～15MHz).

Description of the drawings

Figure 1 is a schematic structural diagram of the multiphase flow microfluidic system in the present invention;

Figure 2 is a schematic structural diagram of the 3D printing system in the present invention.

Detailed ways

The invention provides a method for preparing a double negative acoustic superstructure gel material, which includes the following steps:

A gas-in-water-in-oil emulsion is prepared based on the gas phase, water phase and oil phase, and the gas-in-water-in-oil emulsion includes an oil phase and gas-in-water microspheres dispersed in the oil phase;

Remove the oil phase in the air-in-water-in-oil emulsion, and then mix the obtained air-in-water microspheres with the composite hydrogel solution to obtain a 3D printing ink;

The 3D printing ink is sequentially subjected to 3D extrusion printing and physical gelation to obtain a double negative acoustic superstructure gel material.

In the present invention, unless otherwise specified, the raw materials used are commercially available products that are well known to those skilled in the art, and the equipment used are all equipment well known to those skilled in the art.

The present invention prepares a gas-in-water-in-oil emulsion based on a gas phase, a water phase and an oil phase. The gas-in-water-in-oil emulsion includes an oil phase and gas-in-water microspheres dispersed in the oil phase. In the present invention, the gas phase preferably includes air, nitrogen or inert gas, and is more preferably air. In the present invention, the aqueous phase preferably includes a first gel material and water; the first gel material preferably includes chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methyl Acrylic acylated gelatin is more preferably polyvinyl alcohol; the mass fraction of the first gel material in the aqueous phase is preferably 1 to 10%, more preferably 1.5 to 5%, and even more preferably 2%. The present invention preferably uses the above-mentioned type of first gel material, which has the advantages of good biocompatibility, environmental friendliness, safety and non-toxicity. In the present invention, the oil phase preferably includes silicone oil.

In the present invention, the water-in-oil and gas-in-oil emulsion is preferably prepared in a multiphase flow microfluidic system. As an embodiment of the present invention, as shown in Figure 1, the multiphase flow microfluidic system includes a tubular body. Along the material flow direction, the tubular body is sequentially provided with a gas phase inlet, a water phase inlet and an oil phase inlet. , the tubular body is provided with an oil phase microchannel connected to the oil phase inlet, the oil phase microchannel is provided with a water phase microchannel connected to the water phase inlet, and the water phase microchannel is provided with a gas phase microchannel Gas phase microchannels with connected inlets; wherein the radii of the gas phase microchannels, water phase microchannels and oil phase microchannels are in the range of 5 to 500 μm, and the radius (R ₁ ) of the gas phase microchannels is smaller than the water phase microchannels The radius (R ₂ ) of the water phase microchannel is smaller than the radius of the oil phase microchannel (R ₃ ). In the embodiment of the present invention, R ₁ is 50 μm, R ₂ is 100 μm, and R ₃ is 200 μm in the multiphase flow microfluidic system.

In the present invention, when preparing the water-in-oil gas-in-oil emulsion, the flow rates of the gas phase, water phase and oil phase are preferably independently 1 to 10 μL/min, and more preferably satisfy the flow rate of the water phase (V ₂ ) is less than the flow rate of the gas phase (V ₁ ), and the flow rate of the gas phase is less than the flow rate of the oil phase (V ₃ ). In the embodiment of the present invention, when preparing the water-in-oil emulsion, the V ₁ is 4 μL/min, the V ₂ is 2 μL/min, and the V ₃ is 8 μL/min. In the present invention, the radius of the air-in-water microspheres is preferably 15 to 50 μm, more preferably 20 to 40 μm, and even more preferably 30 μm. In the present invention, the volume fraction of air-in-water microspheres in the air-in-oil emulsion is preferably 1 to 40%, more preferably 10 to 35%, further preferably 20 to 33%, and even more preferably 30%. %. In the present invention, the water-in-oil and gas-in-oil emulsion is preferably prepared under room temperature conditions.

When preparing the water-in-oil emulsion, the present invention passes the gas phase, water phase and oil phase into the multi-phase flow microfluidic system. Due to the difference in mechanical properties of the first gel material in the water phase and the gas phase, there will be Strong unipolar resonance, forming gas-in-water (G/W) microspheres, that is, hollow micro-resonance units (referring to the gel material wrapping gas to form a hollow microbubble structure); the present invention is preferably based on microfluidics The technology keeps the gas phase, water phase and oil phase flow rates within the above flow rate range (specifically, the gas phase, water phase and oil phase flow rates can be controlled by an automatic syringe pump), and the shape, size and distribution of air-in-water microspheres can be precisely controlled. In the present invention, the greater the flow rate of the oil phase, the smaller the size of the gas-in-water microspheres formed; when the flow rates of the gas phase and the oil phase are fixed, when the speed of the water phase increases, the diameter of the gas-in-water microspheres becomes smaller, and the gas-in-water microspheres become smaller. The spacing between microspheres increases; when the automatic injection pumps for the gas phase, water phase and oil phase are started, since the water phase flow rate is set greater than the gas phase flow rate and gas/water is insoluble, the gas phase will be injected into the water phase microchannel. By shearing, water-in-gas microspheres are formed at the connection between the gas phase microchannel and the water phase microchannel with the first gel material aqueous solution as the intermediate liquid (water phase) and the gas phase distributed in the water phase. At the same time, due to the insolubility of water/oil, the gas-in-water microspheres at the outlet of the water phase microchannel will be sheared by the oil phase and dispersed into the oil phase, forming gas-in-water-in-oil (G /W/O) lotion.

After obtaining the air-in-water-in-oil emulsion, the present invention removes the oil phase in the air-in-water-in-oil emulsion, and then mixes the obtained air-in-water microspheres with the composite hydrogel solution to obtain 3D printing ink. The present invention preferably removes the oil phase in the water-in-oil emulsion by washing, and the washing preferably includes alternating water washing and ethanol washing; the water used for the water washing is preferably ultrapure water, and the ethanol used for the ethanol washing is preferably Absolute ethanol. In the present invention, after each washing, the water-in-air microspheres are left to settle completely at the bottom, the upper liquid is sucked away, and then the next washing is performed until the upper liquid is clear; wherein, the last washing is preferably water washing, followed by filtration. The water is removed to obtain air-in-water microspheres.

In the present invention, the composite hydrogel solution preferably includes a second gel material, an auxiliary solidifying material and water. In the present invention, the second gel material preferably includes chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methacrylic acid acylated gelatin, and is more preferably polyvinyl alcohol. In the present invention, the auxiliary curing material preferably includes carrageenan, gelatin or agar, more preferably carrageenan; the carrageenan can be cured into a thermally reversible hydrogel when it is below 40°C, and is used as an auxiliary curing material. By compounding the material with the second gel material, a composite hydrogel solution with room temperature curing ability can be obtained; in addition, adding the auxiliary curing material is beneficial to removing air in the solution. In the present invention, the concentration of the second gel material in the composite hydrogel solution is 10 to 20 wt%, more preferably 15 wt%; the concentration of the auxiliary curing material is 1 to 5 wt%, more preferably 2 wt%.

In the present invention, the radius of the water-in-air microsphere is recorded as r, according to the filling ratio of the designed double negative acoustic supergel material (the ratio of the water-in-air microsphere in the double negative acoustic supergel material Volume ratio, recorded as φ), the number N of water-in-air microspheres in the double negative acoustic superstructure gel material per unit volume can be calculated: N=3φ/(4πr ³ ); According to the designed double negative acoustic superstructure Based on the volume parameters of the structural gel material (taking a material with a square cross-section as an example, the thickness is recorded as h, and the length and width are both w), it can be calculated that Nw ² h is the total number of water-in-air microspheres that need to be prepared and collected. Specifically, the present invention mixes the water-in-air microspheres and the composite hydrogel solution to obtain 3D printing ink. In the present invention, the volume fraction of gas-in-water microspheres in the 3D printing ink is preferably 5 to 40%, more preferably 10 to 30%, and even more preferably 20%; the gas-in-water microspheres in the 3D printing ink are The number of balls is based on the total number of water-in-air microspheres (Nw ² h) required to prepare the double negative acoustic superstructure gel material.

After obtaining the 3D printing ink, the present invention sequentially performs 3D extrusion printing and physical gel formation on the 3D printing ink to obtain a double negative acoustic superstructure gel material. In the present invention, the 3D extrusion printing is preferably performed at room temperature. The operating conditions of the 3D extrusion printing include: the needle extrusion speed (v) is 0.1 to 1 mm/s, and the needle moving speed (v _s ) It is 0.1~1mm/s; the printing line spacing (d) is <1mm, the printing thickness (h) is 1~3mm, and the printing width (w) is 4~6mm. The present invention prepares double negative acoustic superstructural gel materials based on 3D printing technology. It is applicable to a wide range of materials and has accurate spatial guidance, and can construct the required structure more accurately. In the present invention, during the 3D extrusion printing process, the printing line spacing is adjusted to make the printing lines merge. When the printing line spacing is relatively small (d<1mm), it is beneficial to achieve complete integration of the printing lines; printing The thickness (i.e. height) is 1 to 3 mm, the printing width is 4 to 6 mm, and the printing length is equal to the width. The final precursor material obtained by 3D extrusion printing is a cuboid with a square cross-section. In embodiments of the present invention, the 3D extrusion printing is specifically performed in a 3D printing system. The structural diagram of the 3D printing system is shown in Figure 2, including a three-dimensional motion control platform, an extrusion feeding system, and a needle The syringe, the heat preservation device, the computer and the control system, wherein the computer controls the three-dimensional motion control platform, the extrusion feeding system and the heat preservation device through the control system; the extrusion feeding system is connected to the syringe, and the heat preservation The device is used to control the temperature of 3D printing ink in the syringe. The present invention preferably pours the 3D printing ink into a syringe that can be insulated, squeezes out the 3D printing ink from the needle, and realizes 3D extrusion printing by controlling the extrusion feeding system and the three-dimensional motion control platform. The extruded 3D printing The ink quickly completes the first cross-linking and solidification at room temperature.

In the present invention, the physical gel formation preferably includes: freezing and thawing the precursor material obtained after the 3D extrusion printing; the number of freezing and thawing is preferably 3 to 4 times. In the present invention, the temperature of each freezing is preferably -10 to -40°C, more preferably -18°C; the holding time is independently preferably 10 to 12 hours, more preferably 11 hours; the freezing is preferably performed in a refrigerator. In the present invention, the temperature for each thawing is preferably room temperature, and the holding time is independently preferably 1 to 2 hours, more preferably 1.5 to 2 hours. In the present invention, during the physical gel formation process, the precursor material obtained after 3D extrusion printing completes the second cross-linking and solidification to obtain a double negative acoustic superstructure gel material.

The present invention provides a double negative acoustic superstructural gel material prepared by the preparation method described in the above technical solution, including a gel matrix material and hollow microbubbles distributed in the gel matrix material. In the present invention, the radius of the hollow microbubbles is 15 to 50 μm; the volume fraction of the hollow microbubbles in the double negative acoustic superstructure gel material is preferably 5 to 40%. In the present invention, the operating frequency of the double negative acoustic metagel material is 0.5 to 15 MHz, more preferably 5 MHz. The double-negative acoustic metagel material provided by the present invention is suitable for application in the ultrasonic imaging frequency range and can be used for ultrasonic penetration imaging of high-acoustic impedance media; the high-acoustic impedance medium can be, for example, muscles or skulls.

The technical solutions in the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example 1

Using a polyvinyl alcohol aqueous solution with a mass fraction of 2% as the water phase, air as the gas phase, and silicone oil as the oil phase, a water-in-oil emulsion was prepared using the multiphase flow microfluidic system with the structure shown in Figure 1; wherein, the In the multiphase flow microfluidic system, the radius of the gas phase microchannel (R ₁ ) is 50 μm, the radius of the water phase microchannel (R ₂ ) is 100 μm, and the radius of the oil phase microchannel (R ₃ ) is 200 μm; and through automatic injection The pump controls the gas phase flow rate (V ₁ ) to be 4 μL/min, the oil phase (V ₃ ) flow rate to be 8 μL/min, and the water phase flow rate (V ₂ ) to be 2 μL/min. Shearing through the multiphase flow microfluidic system The water-in-air microspheres dispersed in the oil phase are obtained (i.e., polyvinyl alcohol-wrapped hollow microbubbles with a radius of 30 μm) are obtained;

Mix polyvinyl alcohol, carrageenan and water, heat the water bath to 90°C and stir until completely dissolved, and then keep the water bath at 50°C for 1 hour to obtain a composite hydrogel solution. The concentration of polyvinyl alcohol in the composite hydrogel solution is 15wt%, the concentration of carrageenan is 2wt%; the above gas-in-oil emulsion is washed alternately with ultrapure water and absolute ethanol, and left to stand after each washing to completely settle the water-in-air microspheres at the bottom of the washing container. Aspirate and discard the upper liquid, and then perform the next washing until the upper liquid is clear. The last washing is water washing. After water washing, the water is removed by filtration. The obtained water-encapsulated air microspheres are mixed with the composite hydrogel solution to obtain 3D printing. Ink, the volume fraction of air-in-water microspheres in the 3D printing ink is 20%;

Using the 3D printing system with the structure shown in Figure 2, the 3D printing ink is 3D extruded and printed at room temperature (25°C). After being extruded, the 3D printing ink is rapidly pre-cured at room temperature to obtain the precursor. body material; the operating conditions of the 3D extrusion printing include: the needle extrusion speed is 0.5mm/s, the needle moving speed is 0.5mm/s; the printing line spacing is 0.5mm, the printing thickness is 1mm, and the printing width is 4mm. The printing length is equal to the printing width, and the final printed precursor material is a cuboid with a square cross-section;

The precursor material is frozen and thawed to achieve physical gelation, and a double negative acoustic superstructure gel material is obtained; wherein the number of freezing and thawing is 3 times, and the temperature of each freezing is -18°C, and the insulation The time is 11h; the temperature for each thawing is room temperature, and the holding time is 2h.

It can be seen from the above examples that the present invention can achieve this by using a multi-phase flow microfluidic system, using mutually incompatible multi-phase fluids to form an oil-in-water-in-air emulsion, and then using ionic cross-linking technology to generate hollow hydrogel microspheres. Precise control of the size, morphology and composition of water-in-air microspheres; the hollow hydrogel microspheres form micro-resonance units, which can achieve unipolar resonance to produce negative equivalent elastic modulus under ultrasonic excitation. Then combined with 3D printing technology, based on the water-in-air microspheres and composite hydrogel solution, with the help of models designed by computers and software, double negative acoustic superstructure gels with different morphologies can be constructed through layer-by-layer solidification. Material. The stack of large-density water-in-air microspheres in the present invention produces dipole resonance, which can produce dipole resonance under ultrasonic excitation, thereby producing a negative equivalent mass density. The material as a whole exhibits double negative acoustic characteristics, and its operating frequency is 0.5 to 15 MHz. , suitable for application in the ultrasonic imaging frequency range, and can be used for ultrasonic penetration imaging of high acoustic impedance media. Therefore, the combination of microfluidics and 3D printing technology in the present invention provides a design-related controllable solution for the development of double negative acoustic metagel materials.

The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (10)

1. The preparation method of the double negative acoustic super-structure gel material comprises the following steps:

preparing a gas-in-water-in-oil emulsion based on a gas phase, a water phase and an oil phase, wherein the gas-in-water-in-oil emulsion comprises the oil phase and gas-in-water microspheres dispersed in the oil phase;

removing the oil phase in the water-in-oil air emulsion, and then mixing the obtained air-in-water microspheres with the composite hydrogel solution to obtain 3D printing ink;

and sequentially carrying out 3D extrusion printing and physical gel forming on the 3D printing ink to obtain the double negative acoustic super-structure gel material.

2. The method of claim 1, wherein the gas phase comprises air, nitrogen, or an inert gas;

the water phase comprises a first gel material and water, wherein the first gel material comprises chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methacrylic acid acylated gelatin;

the oil phase comprises silicone oil.

3. The preparation method according to claim 2, wherein the gas-in-water-in-oil emulsion is prepared in a multiphase flow microfluidic system;

the multiphase flow microfluidic system comprises a tubular main body, wherein a gas phase inlet, a water phase inlet and an oil phase inlet are sequentially arranged on the tubular main body along the material flow direction, an oil phase microchannel communicated with the oil phase inlet is arranged in the tubular main body, a water phase microchannel communicated with the water phase inlet is arranged in the oil phase microchannel, and a gas phase microchannel communicated with the gas phase inlet is arranged in the water phase microchannel; the radius of the gas phase micro-channel, the radius of the water phase micro-channel and the radius of the oil phase micro-channel are in the range of 5-500 mu m, the radius of the gas phase micro-channel is smaller than the radius of the water phase micro-channel, and meanwhile, the radius of the water phase micro-channel is smaller than the radius of the oil phase micro-channel;

when the water-in-oil gas-in-oil emulsion is prepared, the flow rates of the gas phase, the water phase and the oil phase are independently 1-10 mu L/min.

4. The method according to claim 3, wherein the radius of the air-in-water microsphere is 15 to 50. Mu.m.

5. The method of claim 4, wherein the composite hydrogel solution comprises a second gel material, an auxiliary curing material, and water; the concentration of the second gel material in the composite hydrogel solution is 10-20wt% and the concentration of the auxiliary curing material is 1-5wt%.

6. The method according to claim 5, wherein the second gel material comprises chitosan, sodium alginate, polyvinyl alcohol, polyethylene glycol diacrylate or methacrylic acid acylated gelatin, and the auxiliary solidifying material comprises carrageenan, gelatin or agar.

7. The method according to any one of claims 1 to 6, wherein the volume fraction of the air-in-water microspheres in the 3D printing ink is 5 to 40%.

8. The method of claim 1, wherein the 3D extrusion printing is performed at room temperature, and wherein the operating conditions of the 3D extrusion printing include: the extrusion speed of the needle head is 0.1-1 mm/s, and the moving speed of the needle head is 0.1-1 mm/s; the printing line spacing is less than 1mm, the printing thickness is 1-3 mm, and the printing width is 4-6 mm.

9. The double negative acoustic super-structure gel material prepared by the preparation method of any one of claims 1 to 8, which comprises a gel matrix material and hollow microbubbles distributed in the gel matrix material, wherein the radius of the hollow microbubbles is 15 to 50 μm.

10. Use of the double negative acoustic super structure gel material of claim 9 for preparing an ultrasound penetration imaging preparation, the ultrasound penetration imaging preparation being suitable for high acoustic impedance media comprising muscle or skull.