Method for preparing composite nanocellulose aerogel microspheres based on electrostatic field assisted regulation and control
By using an electrostatic field-assisted control method, the problems of uneven particle size, inconsistent structure, and uneven nanoparticle loading in the preparation of nanocellulose aerogel microspheres were solved, and composite nanocellulose aerogel microspheres with excellent performance were prepared, which are suitable for adsorption, catalysis and biomedical fields.
Patent Information
- Application Number
- CN202610222396.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-25
- Publication Date
- 2026-05-01
AI Technical Summary
Traditional methods for preparing nanocellulose aerogel microspheres suffer from problems such as wide particle size distribution, irregular morphology, poor batch stability, disordered ice crystal growth, inconsistent pore structure, and uneven nanoparticle loading, making it difficult to achieve efficient functional composites.
By employing an electrostatic field-assisted control method, the microsphere molding, internal structure, and functionalization were precisely controlled through the synergistic effect of multiple electric fields. This included electrostatic spraying, gradient freeze-drying, and alternating electric field treatment, resulting in the preparation of composite nanocellulose aerogel microspheres with narrow particle size, uniform size, and tunable function.
This achievement ensures uniform droplet size and structure, uniform nanoparticle loading, and enhances the performance and application potential of aerogel microspheres, particularly demonstrating excellent effects in adsorption, catalysis, and biomedicine.
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Abstract
Description
A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control Technical Field
[0001] This invention relates to the field of aerogel microsphere preparation technology, and specifically to a method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted regulation. Background Technology
[0002] Cellulose nanospheres, with their unique three-dimensional porous structure, excellent biocompatibility, high specific surface area, and environmentally friendly properties, have shown broad application prospects in adsorption separation, drug sustained release, catalyst carriers, and environmental remediation. However, traditional methods for preparing cellulose nanospheres still face significant technical bottlenecks, restricting the full realization of their performance and practical applications.
[0003] In the preparation of microspheres, conventional methods such as emulsification crosslinking and spray drying generally suffer from problems such as wide particle size distribution, irregular morphology, and poor batch stability. Although electrostatic spraying technology can achieve the preparation of micron-sized particles, its jet breakup process is affected by the complex coupling of multiple parameters such as solution properties, flow rate, and voltage. It lacks effective real-time control methods, making it difficult to obtain highly monodisperse droplet precursors, resulting in insufficient uniformity of final product size and difficulty in ensuring structural consistency.
[0004] In terms of controlling the internal structure of aerogels, the random growth of ice crystals in traditional freeze-drying processes often leads to the formation of disordered and tortuous pore networks. Achieving precise guidance of ice crystal growth direction and constructing a highly oriented ordered pore structure to simultaneously optimize the mechanical properties and mass transfer characteristics of aerogels is a significant technical challenge.
[0005] In terms of functional composites, uniformly and stably loading photocatalytic nanoparticles within the three-dimensional network of aerogels is key to endowing materials with multifunctionality. However, existing impregnation or physical mixing methods often result in uneven deposition or even blockage of nanoparticles on the carrier surface or at the pore entrances due to strong agglomeration between nanoparticles. This not only reduces the effective utilization rate of active sites but may also affect the structural integrity and long-term stability of the composite material.
[0006] Therefore, the present invention provides a method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, so as to solve the above-mentioned technical problems. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted regulation. Through the synergistic effect of multi-stage electric fields, precise regulation of the entire process of microsphere forming, internal structure construction and functionalization can be achieved, thereby preparing composite nanocellulose aerogel microspheres with narrow particle size distribution, uniform size and adjustable function, which have broad application prospects in the fields of adsorption, catalysis, and biomedicine.
[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, comprising the following steps: Step 1: adding silane coupling agent hydrolysate to a nanocellulose suspension, stirring and reacting at 25-45℃ for 2-3 hours to obtain a modified nanocellulose suspension; wherein the mass ratio of nanocellulose to silane coupling agent is 1:0.5-1.5; Step 2: adding surfactant to the modified nanocellulose suspension, stirring at 25-45℃ for 3-4 hours, and then loading it into an injection device with adjustable propulsion speed and real-time monitoring feedback function; setting an annular electrode group between the needle and the grounding electrode to form a uniform electrostatic field; simultaneously applying an electrostatic voltage at the needle to drive the propeller to make the fluid in the injection device form a jet and break into droplets; monitoring the droplet diameter in real time through high-speed imaging and image analysis, and adjusting the propulsion speed and voltage in real time to achieve the desired effect. The droplets are uniform in size. Step 3: The droplets first enter a pre-cooling zone with a temperature of -30℃ to -20℃ and an electric field strength of 8-20V / cm for initial condensation, and then fall into liquid nitrogen for rapid freezing into spheres. The frozen microspheres are collected and subjected to gradient freeze-drying to obtain aerogel microspheres with an oriented pore structure. Step 4: The aerogel microspheres are immersed in an aqueous solution of modifier with a concentration of 0.5-5wt% and a mass of 10-20 times the microspheres for 20-30 seconds, then filtered and dried. The above operation is repeated 3-5 times. The aerogel microspheres are then immersed in an aqueous dispersion of nano-microspheres with a concentration of 0.5-3wt% and a mass of 8-15 times the microspheres, and reacted at 30-70℃ for 3-8 hours. An alternating electric field is applied outside the system during the reaction. The reaction solution is then filtered and vacuum dried to obtain composite nanocellulose aerogel microspheres. The amplitude of the alternating electric field is adjusted within the range of 5-15V / cm, and the frequency is set to 40-60Hz.
[0009] Furthermore, the preparation method of the nanocellulose suspension is as follows: cellulose nanocrystals are added to deionized water and ultrasonically dispersed at 200-300W for 50-80 minutes to obtain the nanocellulose suspension; wherein, the concentration of cellulose nanocrystals in the nanocellulose suspension is 0.8-1.5wt%.
[0010] Furthermore, the preparation method of the silane coupling agent hydrolysate is as follows: add the silane coupling agent to an ethanol aqueous solution with a mass of 3-5 times and a concentration of 85-90wt%, and hydrolyze it at 50-60℃ for 1-2 hours to obtain the solution.
[0011] Furthermore, the silane coupling agent is any one of γ-glycidoxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane.
[0012] Furthermore, the propulsion speed of the thruster is set to 300-700 μL / min, and the electrostatic voltage is set to 8-15 kV.
[0013] Furthermore, the surfactant is polyvinylpyrrolidone or carboxymethyl cellulose, and its dosage is 5-8‰ of the modified nanocellulose.
[0014] Furthermore, the specific steps of the gradient freeze-drying process are as follows: first, maintain at -30℃ to -20℃ for 2-3 hours, and then freeze-dry at -50℃ to -40℃ for 24-48 hours.
[0015] Furthermore, the concentration of nanospheres in the aqueous dispersion is 0.5-3 wt%, and the mass of the aqueous dispersion is 8-15 times that of the aerogel microspheres.
[0016] Furthermore, the preparation method of the nanospheres is as follows: ethylene glycol with a volume of 1-3 times that of titanium oxysulfate aqueous solution is added, the resulting mixture is transferred into a reaction vessel and sealed, and heat-treated at 160-190℃ for 5-10h. The reaction solution is then filtered, and the filter cake is washed alternately with deionized water and ethanol 3-5 times, then vacuum dried at 80-100℃, and finally sintered at 300-400℃ for 3-5h to obtain nanospheres; wherein, the concentration of titanium ions in the titanium oxysulfate aqueous solution is 0.2-0.5mol / L.
[0017] Furthermore, the modifier is selected from any one of tea polyphenols, catechins, gallic acid, epicatechin, epicatechin gallic acid, and epigallocatechin.
[0018] Compared with existing technologies, the beneficial effects of this invention are as follows: 1. This invention achieves highly uniform and controllable droplet size through an electrostatic field-assisted injection device and a real-time monitoring and feedback system. Under the synergistic effect of the uniform electrostatic field formed by the adjustable propeller and the ring electrode group, combined with real-time feedback adjustment through high-speed imaging and image analysis, the jet breakage process can be precisely controlled, thereby producing droplets with narrow particle size distribution and regular morphology, laying the foundation for obtaining aerogel microspheres with consistent structure. Secondly, this invention adopts an electric field-assisted gradient freeze-drying process. The droplets undergo the combined action of low temperature and weak electric field in the pre-cooling zone, guiding the initial orientation and solidification of nanocellulose, followed by rapid deep freezing and shaping in liquid nitrogen. This process not only effectively inhibits the random growth of ice crystals but also promotes the orderly arrangement of nanocellulose along the electric field direction, ultimately obtaining aerogel microspheres with a highly oriented porous structure through gradient freeze-drying.
[0019] 2. This invention utilizes a modifier to treat the surface of aerogel microspheres, introducing abundant active groups and enhancing their surface reactivity and affinity. Subsequently, under the action of an applied alternating electric field, the pre-prepared nanospheres are efficiently and uniformly loaded into the interior and surface of the oriented channels. The alternating electric field effectively overcomes the agglomeration tendency of nanoparticles, promotes their directional migration and firm adhesion, and achieves uniform dispersion and stable composite of nanospheres in a three-dimensional network.
[0020] 3. The nanospheres prepared in this invention can control the conversion between hydrophilicity and hydrophobicity through light irradiation of different wavelengths or intensities, enabling them to selectively capture or release substances of different polarities. Secondly, the nanospheres possess excellent photocatalytic activity, allowing the composite nanocellulose aerogel microspheres to efficiently degrade organic pollutants or exhibit self-cleaning capabilities under ultraviolet or visible light irradiation, expanding their application in environmental remediation. Furthermore, the nanospheres, acting as a reinforcing phase, can further enhance the compressive modulus and shape recovery of the composite nanocellulose aerogel microspheres, and their high thermal stability also helps improve the thermal durability of the composite material. In addition, the uniform loading of nanospheres within the oriented cellulose network forms a micro-nano hierarchical composite structure. This structure not only increases the specific surface area and active sites but also significantly improves performance through synergistic effects between components, giving the prepared composite nanocellulose aerogel microspheres excellent application potential in adsorption, catalysis, and sensing, with broad application prospects. Detailed Implementation
[0021] The technical solutions of 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0022] Example 1: A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, comprising the following steps: Step 1: Adding silane coupling agent hydrolysate to a nanocellulose suspension, stirring and reacting at 25°C for 2 hours to obtain a modified nanocellulose suspension; wherein the mass ratio of nanocellulose to silane coupling agent is 1:0.5; wherein the preparation method of the nanocellulose suspension is: adding cellulose nanocrystals to deionized water and ultrasonically dispersing at 200W for 80 minutes to obtain the nanocellulose suspension; wherein the concentration of cellulose nanocrystals in the nanocellulose suspension is 0.8 wt%. The preparation method of silane coupling agent hydrolysate is as follows: γ-glycidyl etheroxypropyltrimethoxysilane is added to an 85wt% ethanol aqueous solution at 3 times its mass, the pH is adjusted to 3.5 with acetic acid, and the solution is hydrolyzed at 50℃ for 2 hours to obtain the hydrolysate. Step two: A surfactant is added to the modified nanocellulose suspension, and after stirring at 25℃ for 4 hours, the solution is loaded into an injection device with adjustable propulsion speed and real-time monitoring feedback function. A ring-shaped electrode group is set between the needle and the grounding electrode to form a uniform electrostatic field. Simultaneously, an electrostatic voltage is applied at the needle to drive the propeller, causing the fluid in the injection device to form a jet and break into droplets. The droplet diameter is monitored in real time using high-speed photography and image analysis, and the propulsion speed and voltage are adjusted in real time to ensure uniform droplet size. The propulsion speed of the propeller is set to 300 μL / min, and the electrostatic voltage is set to 8 kV. The surfactant is polyvinylpyrrolidone, and its dosage is 5‰ of the modified nanocellulose. In step three, the droplets first enter a pre-cooling zone at -30℃ and an electric field strength of 8 V / cm for initial condensation, and then fall into liquid nitrogen for rapid freezing into spheres. The frozen microspheres are collected and subjected to gradient freeze-drying to obtain aerogel microspheres with an oriented pore structure. The specific steps of gradient freeze-drying are as follows: First, keep at -30℃ for 3 hours, then freeze-dry at -50℃ for 48 hours; Step four, immerse the aerogel microspheres in a 0.5wt% aqueous solution of tea polyphenols (10 times their weight) for 20 seconds, filter and air-dry, repeating the above operation 3 times; then immerse the aerogel microspheres in an aqueous dispersion of nano-microspheres (8 times their weight) with a concentration of 0.5wt%, and react at 3℃ for 8 hours, applying an alternating electric field outside the system during the reaction; then filter and vacuum dry the reaction solution to obtain composite nanocellulose aerogel microspheres; wherein, the amplitude of the alternating electric field is adjusted within the range of 5V / cm, and the frequency is set to 40Hz.
[0023] The concentration of nanospheres in the aqueous dispersion of nanospheres was 0.5 wt%, and the mass of the aqueous dispersion of nanospheres was 8 times that of the aerogel microspheres. The preparation method of nanospheres was as follows: ethylene glycol of equal volume was added to an aqueous solution of titanium oxysulfate, the resulting mixture was transferred to a reaction vessel and sealed, and heat-treated at 160℃ for 10 h. The reaction solution was then filtered, and the filter cake was washed three times alternately with deionized water and ethanol, then vacuum dried at 80℃, and finally sintered at 300℃ for 3 h to obtain nanospheres. The concentration of titanium ions in the aqueous solution of titanium oxysulfate was 0.2 mol / L.
[0024] Example 2: A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, comprising the following steps: Step 1: Adding silane coupling agent hydrolysate to a nanocellulose suspension, stirring and reacting at 35°C for 3 hours to obtain a modified nanocellulose suspension; wherein the mass ratio of nanocellulose to silane coupling agent is 1:1; wherein the preparation method of the nanocellulose suspension is: adding cellulose nanocrystals to deionized water and ultrasonically dispersing at 250W for 60 minutes to obtain the nanocellulose suspension; wherein the concentration of cellulose nanocrystals in the nanocellulose suspension is 1wt%; the preparation method of the silane coupling agent hydrolysate is: adding γ-glycidoxypropyltrimethoxysilane agent to 4 times its mass of an 85wt% ethanol aqueous solution, and adjusting the pH value to 3 with acetic acid.5. After hydrolysis at 55℃ for 2 hours, the product is obtained; Step 2: Add surfactant to the modified nanocellulose suspension, stir at 35℃ for 4 hours, and then load it into an injection device with adjustable propulsion speed and real-time monitoring feedback function. A ring-shaped electrode group is set between the needle and the grounding electrode to form a uniform electrostatic field; simultaneously, an electrostatic voltage is applied at the needle to drive the propeller, causing the fluid in the injection device to form a jet and break into droplets; the droplet diameter is monitored in real time through high-speed imaging and image analysis, and the propulsion speed and voltage are adjusted in real time to ensure uniform droplet size; The propulsion speed of the thruster was set to 500 μL / min, and the electrostatic voltage was set to 12 kV; the surfactant was carboxymethyl cellulose, and its dosage was 6‰ of the modified nanocellulose; in step three, the droplets first entered a pre-cooling zone with a temperature of -25℃ and an electric field strength of 15 V / cm for initial condensation, and then fell into liquid nitrogen for rapid freezing into spheres; the frozen microspheres were collected and subjected to gradient freeze-drying to obtain aerogel microspheres with an oriented pore structure; the specific steps of gradient freeze-drying were as follows: first, keep at -25℃ for 3 hours, and then freeze-dry at -45℃ for 4 hours. 0h is sufficient; Step 4: Immerse the aerogel microspheres in a 3wt% catechol aqueous solution (15 times their weight) for 25s, then filter and air dry. Repeat the above operation 4 times; then immerse the aerogel microspheres in a 2wt% nano-microsphere aqueous dispersion (12 times their weight) and react at 50℃ for 5h, applying an alternating electric field outside the system during the reaction; then filter and vacuum dry the reaction solution to obtain composite nanocellulose aerogel microspheres; wherein, the amplitude of the alternating electric field is adjusted within a range of 10V / cm, and the frequency is set to 50Hz; wherein, nano... The concentration of nanospheres in the aqueous dispersion was 2 wt%, and the mass of the aqueous dispersion was 12 times that of the aerogel microspheres. The nanospheres were prepared by adding twice the volume of ethylene glycol to an aqueous solution of titanium oxysulfate. The resulting mixture was transferred to a sealed reactor and heat-treated at 180°C for 6 hours. The reaction solution was then filtered, and the filter cake was washed four times alternately with deionized water and ethanol. The mixture was then vacuum-dried at 90°C and finally sintered at 350°C for 4 hours to obtain the nanospheres. The concentration of titanium ions in the titanium oxysulfate aqueous solution was 0.3 mol / L.
[0025] Example 3: A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, comprising the following steps: Step 1: Adding silane coupling agent hydrolysate to a nanocellulose suspension, stirring and reacting at 45°C for 2 hours to obtain a modified nanocellulose suspension; wherein the mass ratio of nanocellulose to silane coupling agent is 1:1.5; wherein the preparation method of the nanocellulose suspension is: adding cellulose nanocrystals to deionized water and ultrasonically dispersing at 300W for 50 minutes to obtain the nanocellulose suspension; wherein the concentration of cellulose nanocrystals in the nanocellulose suspension is 1.5wt%; the preparation method of the silane coupling agent hydrolysate is: adding γ-glycidyl etheroxypropyltrimethoxysilane to 5 times its mass of a 90wt% ethanol aqueous solution, and adjusting the pH to 3 with acetic acid.5. After hydrolysis at 60℃ for 1 hour, the product is obtained; Step 2: Add surfactant to the modified nanocellulose suspension, stir at 45℃ for 3 hours, and then load it into an injection device with adjustable propulsion speed and real-time monitoring feedback function. A ring-shaped electrode group is set between the needle and the grounding electrode to form a uniform electrostatic field; simultaneously, an electrostatic voltage is applied at the needle to drive the propeller, causing the fluid in the injection device to form a jet and break into droplets; the droplet diameter is monitored in real time through high-speed imaging and image analysis, and the propulsion speed and voltage are adjusted in real time to ensure uniform droplet size; among which, The propulsion speed of the thruster was set to 700 μL / min, and the electrostatic voltage was set to 15 kV; the surfactant was polyvinylpyrrolidone, and its dosage was 8‰ of the modified nanocellulose; in step three, the droplets first entered a pre-cooling zone at a temperature of -20℃ and an electric field strength of 20 V / cm for initial condensation, and then fell into liquid nitrogen for rapid freezing into spheres; the frozen microspheres were collected and subjected to gradient freeze-drying to obtain aerogel microspheres with an oriented pore structure; the specific steps of gradient freeze-drying were: first, holding at -20℃ for 2 hours, and then freeze-drying at -40℃ for 24 hours. Step 4: Immerse the aerogel microspheres in a 5wt% gallic acid aqueous solution (20 times their weight) for 30 seconds, then filter and air dry. Repeat this process 5 times. Next, immerse the aerogel microspheres in a 3wt% nano-microsphere aqueous dispersion (15 times their weight) and react at 70°C for 3 hours, applying an alternating electric field outside the system during the reaction. Then, filter and vacuum dry the reaction solution to obtain the composite nanocellulose aerogel microspheres. The amplitude of the alternating electric field is adjusted to 15V / cm, and the frequency is set to 60Hz. The concentration of nanospheres in the aqueous dispersion of nanospheres was 3 wt%, and the mass of the aqueous dispersion of nanospheres was 15 times that of the aerogel microspheres. The nanospheres were prepared by adding ethylene glycol at a volume of 3 times that of titanium oxysulfate aqueous solution. The resulting mixture was transferred to a reaction vessel and sealed. After heat treatment at 190℃ for 5 h, the reaction solution was filtered. The filter cake was washed 5 times alternately with deionized water and ethanol, then vacuum dried at 100℃, and finally sintered at 400℃ for 3 h to obtain the nanospheres. The concentration of titanium ions in the titanium oxysulfate aqueous solution was 0.5 mol / L.
[0026] Comparative Example 1: The difference between this comparative example and Example 1 is that: in this comparative example, an equal amount of aerogel microspheres prepared in step three are used instead of the composite nanocellulose aerogel microspheres prepared in Example 1.
[0027] Comparative Example 2: The difference between this comparative example and Example 1 is that no annular electrode group was set in this comparative example, and the droplet diameter was not monitored in real time by high-speed imaging and image analysis.
[0028] Comparative Example 3: The difference between this comparative example and Example 1 is that the collected frozen microspheres were not subjected to gradient freeze-drying in this comparative example.
[0029] Comparative Example 4: The difference between this comparative example and Example 1 is that no alternating electric field was applied outside the system during the reaction process in this comparative example.
[0030] Performance testing: The relevant properties of the composite nanocellulose aerogel microspheres prepared in Examples 1-3 and Comparative Examples 1-4 were tested respectively, and the test data are recorded in the table below: Note: The specific method for testing the particle size span is as follows: The particle size of the composite nanocellulose aerogel microsphere sample is determined by laser diffraction. 50 mg of aerogel microsphere sample is mixed with 1 mL of ultrapure water, vortexed for 20 seconds, and then dispersed ultrasonically. The aerogel microsphere dispersion is then placed in a particle size analyzer to measure D10, D50, and D90, and the span value is calculated as (D90 - D10) / D50. The ultraviolet irradiation intensity is 1.3 mW / cm². 3 The UV irradiation time was 3 hours. After the irradiation was completed, the water droplet contact angle was measured after 12 hours in the dark at room temperature.
[0031] By comparing and analyzing the relevant data in the table, it can be seen that this invention achieves precise control over the entire process of microsphere molding, internal structure construction, and functionalization through the synergistic effect of multi-stage electric fields. This results in the preparation of composite nanocellulose aerogel microspheres with narrow particle size distribution, uniform size, and tunable function, which have broad application prospects in adsorption, catalysis, and biomedicine. Therefore, this invention demonstrates that the method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control has a broader market prospect and is more suitable for widespread application.
[0032] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0033] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control, characterized in that, Includes the following steps: Step 1: Add silane coupling agent hydrolysate to the nanocellulose suspension and stir at 25-45℃ for 2-3 hours to obtain a modified nanocellulose suspension; wherein the mass ratio of nanocellulose to silane coupling agent is 1:0.5-1.
5. Step 2: Add surfactant to the modified nanocellulose suspension and stir at 25-45℃ for 3-4 hours. Then, load the mixture into an injection device with adjustable propulsion speed and real-time monitoring feedback. A ring-shaped electrode group is set between the needle and the grounding electrode to form a uniform electrostatic field. Simultaneously, an electrostatic voltage is applied at the needle to drive the propeller, causing the fluid in the injection device to form a jet and break into droplets. The droplet diameter is monitored in real time by high-speed imaging and image analysis, and the propulsion speed and voltage are adjusted in real time to ensure uniform droplet size. Step 3: The droplets first enter a temperature range of -30℃ to -20℃. The microspheres are initially condensed in a pre-cooling zone with an electric field strength of 8-20 V / cm, and then rapidly frozen into spheres in liquid nitrogen. The frozen microspheres are collected and subjected to gradient freeze-drying to obtain aerogel microspheres with an oriented pore structure. In step four, the aerogel microspheres are immersed in an aqueous solution of a modifier with a concentration of 0.5-5 wt% (10-20 times their weight) for 20-30 seconds, then filtered and dried. This process is repeated 3-5 times. The aerogel microspheres are then immersed in an aqueous dispersion of nano-microspheres with a concentration of 0.5-3 wt% (8-15 times their weight) and reacted at 30-70℃ for 3-8 hours, with an alternating electric field applied outside the system during the reaction. The reaction solution is then filtered and vacuum dried to obtain composite nanocellulose aerogel microspheres. The amplitude of the alternating electric field is adjusted within the range of 5-15 V / cm, and the frequency is set to 40-60 Hz.
2. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that, The preparation method of the nanocellulose suspension is as follows: cellulose nanocrystals are added to deionized water and ultrasonically dispersed at 200-300W for 50-80 minutes to obtain the nanocellulose suspension; wherein, the concentration of cellulose nanocrystals in the nanocellulose suspension is 0.8-1.5wt%.
3. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that, The preparation method of the silane coupling agent hydrolysate is as follows: add the silane coupling agent to an ethanol aqueous solution with a mass of 3-5 times and a concentration of 85-90wt%, and hydrolyze it at 50-60℃ for 1-2 hours to obtain the solution.
4. A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1 or 3, characterized in that: The silane coupling agent is either γ-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane.
5. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that: The propulsion speed of the thruster is set to 300-700 μL / min, and the electrostatic voltage is set to 8-15 kV.
6. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that: The surfactant is polyvinylpyrrolidone or carboxymethyl cellulose, and its dosage is 5-8‰ of the modified nanocellulose.
7. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that, The specific steps of the gradient freeze-drying process are as follows: first, maintain the temperature at -30℃ to -20℃ for 2-3 hours, and then freeze-dry at -50℃ to -40℃ for 24-48 hours.
8. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1, characterized in that: The concentration of nanospheres in the aqueous dispersion is 0.5-3 wt%, and the mass of the aqueous dispersion is 8-15 times that of the aerogel microspheres.
9. A method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 1 or 8, characterized in that, The preparation method of the nanospheres is as follows: ethylene glycol with a volume of 1-3 times that of titanium oxysulfate aqueous solution is added to the solution. The resulting mixture is transferred into a reaction vessel and sealed. After heat treatment at 160-190℃ for 5-10 hours, the reaction solution is filtered. The filter cake is washed with deionized water and ethanol alternately 3-5 times, then vacuum dried at 80-100℃, and finally sintered at 300-400℃ for 3-5 hours to obtain the nanospheres. The concentration of titanium ions in the titanium oxysulfate aqueous solution is 0.2-0.5 mol / L.
10. The method for preparing composite nanocellulose aerogel microspheres based on electrostatic field-assisted control according to claim 9, characterized in that: The modifier is selected from any one of tea polyphenols, catechins, gallic acid, epicatechin, epicatechin gallic acid, and epigallocatechin.