Magnetic control nanofiber anti-counterfeiting gel and preparation method thereof

Abstract

The invention discloses a preparation method of magnetic regulation and control nanofiber anti-counterfeiting gel, which comprises the following steps: firstly, preparing nanofiber magnetofluid with good dispersion performance, and directionally arranging the nanofiber magnetofluid through an external magnetic field; and then, combining the magnetic control nanofiber anti-counterfeiting gel with a coagulating bath to prepare the magnetic control nanofiber anti-counterfeiting gel with high orientation degree. The method is simple and convenient to operate, does not need complex chemical crosslinking, and has relatively strong controllability. The magnetic field and the coagulating bath cooperatively regulate and control directional arrangement of nanofibers in the gel, information coding and storage functions are achieved, excellent anisotropic characteristics are given to the gel, and the gel is suitable for high-end application fields such as tissue engineering, drug delivery, sensors and energy storage.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanofiber anti-counterfeiting gels, and particularly relates to a preparation method and application of a magnetically regulated nanofiber anti-counterfeiting gel. Background Art

[0002] As a functional material that realizes anti-counterfeiting, anti-tampering and brand protection through physical or chemical information coding, the anti-counterfeiting gel is of great significance in modern anti-counterfeiting technology. In recent years, with the continuous growth of the demand for high-end anti-counterfeiting, information storage and intelligent materials, the application prospect of the anti-counterfeiting gel has become increasingly broad. At the same time, chitin nanofibers and cellulose nanofibers, as two natural polysaccharide-based nanomaterials, have been widely studied for the preparation of various high-performance functional materials due to their rich sources, excellent biocompatibility and colloidal stability. These nanofibers can not only serve as structural scaffolds, but also realize efficient information coding and regulation through their surface functional groups.

[0003] Currently, the commonly used preparation methods of anti-counterfeiting gels mainly rely on chemical cross-linking technology, in which nanofibers are fixed together by adding cross-linking agents to form a gel network. However, traditional methods often have problems such as cumbersome operation, random structure, and difficult precise control of cross-linking, resulting in low internal orientation degree and uneven hierarchical distribution of the gel, thereby affecting its mechanical properties and information coding accuracy, and it is difficult to meet the requirements of high-end application fields such as tissue engineering, drug delivery, sensors and energy storage.

[0004] In view of the above problems, the present invention proposes a preparation method of a magnetically regulated nanofiber anti-counterfeiting gel. This method utilizes the excellent fluidity and magnetic responsiveness of magnetic fluid, and realizes the directional arrangement of nanofibers through an external magnetic field, and then combines with the gas-phase coagulation bath curing technology to construct a gel with a structure from monolayer to multilayer, and even with a helical directional arrangement. By precisely controlling the magnetic field distribution and curing conditions, a highly ordered hierarchical structure can be formed inside the gel, realizing high-precision information coding, storage, interference and hiding functions. This method is easy to operate, does not require complex chemical cross-linking, is green and environmentally friendly, and has a broad application prospect. Summary of the Invention

[0005] Aiming at the deficiencies of the magnetically regulated nanofiber anti-counterfeiting gel in the prior art in terms of fiber orientation control, hierarchical structure construction and information coding, the present invention proposes a preparation method and application of a magnetically regulated nanofiber anti-counterfeiting gel, aiming to overcome the problems of inaccurate structural orientation, uneven hierarchical distribution and low information storage efficiency in the prior art, so as to realize the preparation of a gel material with high orientation, high stratification and high-precision information coding.

[0006] To this end, the specific technical solution adopted by the present invention is as follows: A preparation method of a magnetically regulated nanofiber anti-counterfeiting gel, which includes the following steps:

[0007] (1) Place the nanofiber magnetic fluid in the magnetic field generated by a magnet, and regulate the distribution direction of the magnetic field to achieve the directional alignment of magnetic nanofibers, obtaining a nanofiber magnetic fluid with a directional alignment structure; (2) Solidify the above nanofiber magnetic fluid with a directional alignment structure through a gas-phase coagulation bath to obtain a magnetically regulated nanofiber anti-counterfeiting gel.

[0008] Furthermore, the magnet is at least one of a permanent magnet, a soft magnet, an electromagnet, and a special alloy magnet; the magnetic field strength is 1 mT to 100 mT.

[0009] Furthermore, the nanofiber magnetic fluid is a nanocellulose magnetic fluid or a nanochitin magnetic fluid; the mass concentration of chitin nanofibers in the nanochitin magnetic fluid is 0.1% to 5%, and the mass concentration of cellulose nanofibers in the nanocellulose magnetic fluid is 0.1% to 3%.

[0010] Furthermore, different patterns are formed by combining magnets to adjust the magnetic field distribution, and the magnetic nanofibers are oriented to obtain a magnetically regulated nanofiber anti-counterfeiting gel with an internal pattern.

[0011] Furthermore, in step (1), first cover the surface of the nanofiber magnetic fluid with a film of different patterns; then adjust the distribution direction of the magnetic field to orient the magnetic nanofibers; after the curing in step (2) is completed, remove the covering film, adjust the magnetic field distribution again, and orient the magnetic nanofibers with a magnetic field distribution different from that when the film is covered. Finally, a magnetically regulated nanofiber anti-counterfeiting gel containing the pattern of the covering film is prepared through a gas-phase coagulation bath.

[0012] Furthermore, the penetration and solidification direction of the gas-phase coagulation bath of the nanofiber magnetic fluid is perpendicular to the magnetic field direction. The magnetic field horizontal direction is rotated from 0° to 360° to orient the magnetic nanofibers, and a magnetically regulated nanofiber anti-counterfeiting gel with multiple spatially stratified structures with different orientations formed inside is prepared.

[0013] Furthermore, during the preparation of the magnetically regulated nanofiber anti-counterfeiting gel, the rotation speed of the magnetic field horizontal direction from 0° to 360° is 0.5 rpm / min to 5.0 rpm / min, and the solidification speed of the gas-phase coagulation bath is 0.1 mm / min to 1.0 mm / min. The nanofibers in the magnetic fluid are continuously gelated and fixed at different angles, and a magnetically regulated nanofiber anti-counterfeiting gel with a helical directional alignment structure is prepared; the pitch in the helical directional alignment structure is 100 μm to 300 μm.

[0014] Furthermore, the content of magnetic nanoparticles in the nanofiber magnetic fluid is 1% to 15%, the size of the magnetic particles is 5 to 30 nm, and the saturation magnetization intensity is 1 to 15 emu / g.

[0015] Further, the gas-phase coagulation bath is a volatile acidic coagulation bath or an alkaline ammonia water coagulation bath. The acidic coagulants are hydrochloric acid, acetic acid, and methacryloyl chloride. The time of the acidic coagulation bath is 1 min to 2 h, and the temperature is 1 °C to 60 °C.

[0016] According to another aspect of the present invention, there is provided a magnetically regulated nanofiber anti-counterfeiting gel, which is prepared by using the preparation method of the magnetically regulated nanofiber anti-counterfeiting gel.

[0017] Further, the fibers in the magnetically regulated nanofiber anti-counterfeiting gel have a highly ordered arrangement, and the arrangement direction is consistent with the magnetic field direction. The degree of orientation can reach 50-90%, and the gel storage modulus can reach 1.5 kPa to 30 kPa.

[0018] 11. According to still another aspect of the present invention, there is provided an application of the magnetically regulated nanofiber anti-counterfeiting gel in a biomimetic crab shell material. The magnetically regulated nanofiber anti-counterfeiting gel with a helical and oriented arrangement structure, which is prepared by using the preparation method of the magnetically regulated nanofiber anti-counterfeiting gel, is pickled to remove magnetic nanoparticles and then soaked in a calcium ion solution, and then passed through an ammonia gas-phase coagulation bath to obtain a hydrogel with a superhelical nanofiber skeleton and an inorganic layered mineralized biomimetic structure. Finally, the above gel is hot-pressed and dried to obtain a lightweight and high-strength biomimetic crab shell structure material.

[0019] Further, the concentration of the acid solution is 1% to 5%, the concentration of the calcium ion solution is 5 mmol / L to 120 mmol / L, the time of the gas-phase coagulation bath is 12 h to 48 h, the temperature is 1 °C to 60 °C, the temperature of the hot pressing is 60 °C to 80 °C, the pressure of the hot pressing is 1 MPa to 100 MPa, and the time of the hot pressing is 5 min to 30 min.

[0020] Further, the biomimetic crab shell material has a regular layered structure with alternating mineralized inorganic layers and nanofiber organic layers. The bending strength of the biomimetic crab shell is 20 MPa to 136 MPa, the bending modulus is 5 GPa to 22 GPa, and the fracture strain is 0.2% to 0.91%. The biomimetic structure material with alternating mineralized inorganic layers and nanofiber organic layers meets the requirements of bone tissue engineering and bone replacement in terms of mechanical properties.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) Through the magnetic field-assisted and gas-phase coagulation bath curing methods, precise orientation and multi-layered stratified structure of the fibers inside the gel are achieved, and the degree of orientation is as high as 50-90%. Without relying on complex chemical cross-linking processes, the preparation steps are simplified.

[0023] (2) The construction of a bionic spiral oriented arrangement structure is achieved through the coupling and synergy of magnetic field rotation and gas-phase coagulation bath. The method is simple and easy to operate, providing a functional platform for subsequent bionic material design;

[0024] (3) This anti-counterfeiting gel can not only be used for information encoding, storage, interference, and hiding, but also be widely applied to high-end fields such as tissue engineering, drug delivery, sensors, energy storage, and bionic materials, with broad application prospects. Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 Schematic diagram of the preparation of magnetically regulated anti-counterfeiting gel.

[0027] Figure 2 Schematic diagram of the orientation effect of magnetic nanofibers under magnetic field regulation.

[0028] Figure 3 Schematic diagram and photo of magnetically regulated anti-counterfeiting gel under horizontal / vertical magnetic fields.

[0029] Figure 4 Oriented arrangement of fibers in magnetically regulated nanofiber anti-counterfeiting gel and its degree of orientation.

[0030] Figure 5 Pattern display effect of magnetic field for oriented nanofiber magnetic fluid placed above a magnet in a gas-phase coagulation bath.

[0031] Figure 6 Patterned magnetically regulated nanofiber anti-counterfeiting gel.

[0032] Figure 7 Design concept of writing binary information into the gel by designing the direction interval of nanofibers in magnetically regulated nanofiber anti-counterfeiting gel.

[0033] Figure 8 Corresponding relationship between nanofiber arrangement direction interval and binary information.

[0034] Figure 9 Effect diagrams of information storage, interference, and hiding of magnetically regulated nanofiber anti-counterfeiting gel.

[0035] Figure 10 Schematic diagram of the device for preparing magnetically regulated nanofiber anti-counterfeiting gel with a spiral oriented arrangement structure.

[0036] Figure 11 Schematic diagram of the preparation of the bionic crab shell by hot pressing.

[0037] Figure 12 Photos of the bionic crab shell and SEM images of its cross section.

[0038] Figure 13 Long-term hydrochloric acid vapor coagulation bath causes the anti-counterfeiting pattern to collapse. DETAILED DESCRIPTION

[0039] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but those skilled in the art will appreciate that the following embodiments and examples are only used to illustrate the present invention and should not be considered as the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. If no specific conditions are specified, they are carried out according to conventional conditions or conditions recommended by the manufacturer.

[0040] Example 1: Preparation of nanofiber magnetic fluid and magnetically regulated anti-counterfeiting gel

[0041] The nanofibers involved in the present invention are prepared from cellulose and chitin as raw materials by acid hydrolysis, deacetylation, enzyme oxidation or chemical oxidation (such as TEMPO / NaBr / NaClO oxidation, TEMPO / laccase / O2 oxidation) combined with mechanical treatment (high-pressure homogenization, ultrasonic crushing, ultrafine grinding, colloid milling, microfluidization), and include negatively charged cellulose nanofibers, positively charged cellulose nanofibers, and bicharged cellulose nanofibers, positively charged chitin nanofibers, and bicharged chitin nanofibers.

[0042] Preparation of cellulose nanofiber magnetic fluid: A nanofiber (TEMPO oxidized cellulose nanofiber, TOCN) dispersion with a mass concentration of 1% was used as the base liquid, 1.194g of ferrous chloride tetrahydrate and 3.24g of ferric chloride hexahydrate were added thereto, and after being fully stirred at room temperature, an ultrasonic probe was used to treat for 60s to make the dispersion uniform. Then, the mixed solution was poured into a 2L sealed container, and 30mL of 25% ammonia water was added at the same time. After passing through an ammonia bath, the mixture was allowed to stand at 25°C for 24h to react. After the reaction, the excess ions were removed by dialysis to obtain a cellulose nanofiber magnetic fluid with a magnetic nanoparticle content of about 8%, an average particle size of about 17nm, and a saturation magnetization of about 8emu / g.

[0043] Preparation of chitin nanofiber magnetic fluid: A nanofiber (partially deacetylated chitin nanofiber, DEChN) dispersion with a mass concentration of 2.5% is used as a base liquid, 1.9104g of ferrous chloride tetrahydrate and 5.184 of ferric chloride hexahydrate are added thereto, and after being fully stirred at room temperature, an ultrasonic probe is used to treat for 60s to make the dispersion uniform. Then, the mixed solution is poured into a 2L sealed container, and 30mL of 25% ammonia water is added at the same time, and the mixture is placed in an ammonia bath at 25°C for 24h to react. After the reaction, the excess ions are removed by physical crushing and repeated centrifugation, and the precipitate is then redispersed in a 1% acetic acid solution to obtain a chitin nanofiber magnetic fluid, which has a magnetic nanoparticle content of about 6%, an average particle size of about 12nm, and a saturation magnetization of about 7emu / g.

[0044] Preparation of magnetically regulated anti-counterfeiting gel: The above-prepared negatively charged cellulose nanofiber magnetic fluid: TOCN carboxyl content (0.8-1.4mmol / g), mass concentration 1%, magnetic particle content 8%, magnetic particle size 17nm, saturation magnetization intensity of about 8emu / g of magnetic fluid is poured into a flat mold and placed in a magnetic field formed by a combination of permanent magnets and soft magnets. The magnetic field intensity is set to 10mT, and the treatment time is 10min, so that the magnetic nanofibers are oriented along the direction of the magnetic field. Subsequently, the oriented magnetic fluid is placed in a volatile acetic acid coagulation bath and cured at room temperature for 2h to quickly fix the gel structure. The storage modulus is tested by a rheometer and is 8-12KPa.

[0045] The magnetic field used in the present invention is not limited to neodymium iron boron magnets. The magnetic field generated by permanent magnets, soft magnets, electromagnets or special alloy magnets are all within the scope of the present invention.

[0046] The acid vapor bath involved in the present invention is not limited to acetic acid, and various volatile acids are within the scope of the present invention.

[0047] The magnetic field orientation used in the present invention is not limited to the horizontal direction mentioned in the embodiment. A spatial rectangular coordinate system is established with the magnetic nanofiber as the origin. Any plane and any angle in the rectangular coordinate system are within the scope of the present invention.

[0048] By adjusting the concentration of nanofibers, the dosage of ferrous chloride tetrahydrate and ferric chloride hexahydrate, a series of nanofiber magnetic fluids can be prepared, and their ability to prepare magnetically regulated anti-counterfeiting gels is evaluated. The results are shown in the following table:

[0049]

[0050] Example 2: Preparation of magnetically controlled anti-counterfeiting gel based on chitin nanofiber magnetic fluid

[0051] The positively charged chitin nanofiber magnetic fluid will be prepared by Example 1, where the amino content of DEChN (0.5 - 2.0 mmol / g), the mass concentration of nanofibers is 2.5%, the magnetic particle content is 6%, the magnetic particle size is 12 nm, and the magnetic fluid with a saturation magnetization of about 7 emu / g is poured into a mold and aligned under the action of a magnetic field (magnetic field strength 100 mT) for 30 min; then it is placed in an ammonia gas-phase coagulation bath (temperature 40 °C, curing time 2 h) for curing to form an orientation anti-counterfeiting gel.

[0052] The orientation degrees of the magnetic field-regulated anti-counterfeiting gels prepared from different magnetic fluids under different magnetic field strengths are as follows:

[0053]

[0054] Example 3: Preparation of Magnetic Field-Regulated Anti-Counterfeiting Gels with Different Patterns Formed by Combining Magnets

[0055] The amphoteric cellulose nanofiber magnetic fluid prepared by Example 1, where the carboxyl content (0.4 - 0.6 mmol / g) and amino content (0.4 - 1.0 mmol / g) of the amphoteric cellulose nanofibers, the mass concentration of nanofibers is 3%, the magnetic particle content is 15%, the magnetic particle size is 30 nm, and the magnetic fluid with a saturation magnetization of about 15 emu / g, by combining different magnets to form the required pattern, and then aligned under the action of this magnetic field (magnetic field strength 80 mT) for 15 min; then it is placed in a hydrochloric acid gas-phase coagulation bath (temperature 50 °C, curing time 1.5 h) for curing to form an anti-counterfeiting gel with a designed pattern. ( Figure 5 )

[0056] Example 4: Preparation of Magnetic Field-Regulated Nanofiber Anti-Counterfeiting Gels by Covering-Two-Step Curing Method

[0057] The amphoteric chitin nanofiber magnetic fluid obtained by Example 1 is poured into a mold, where the carboxyl content (0.5 - 0.6 mmol / g) and amino content (0.8 - 1.4 mmol / g) of the amphoteric chitin nanofibers, the mass concentration of nanofibers is 3%, the magnetic particle content is 15%, the magnetic particle size is 30 nm, and the magnetic fluid with a saturation magnetization of about 15 emu / g, and a preset pattern film (crab pattern or pentagram pattern) is covered in a specific area; aligned under the action of a magnetic field (magnetic field strength 68 mT) for 12 min; then it is placed in an acetic acid gas-phase coagulation bath (temperature 30 °C, curing time 1 h) for curing to form an orientation anti-counterfeiting gel. Then the pattern film is removed, by adjusting the horizontal direction of the magnetic field to 180°, and continuing to align under the action of a magnetic field (magnetic field strength 68 mT) for 12 min; then it is placed in an acetic acid gas-phase coagulation bath (temperature 30 °C, curing time 1 h) for curing. A magnetic field-regulated anti-counterfeiting gel with a specific anti-counterfeiting pattern can be preparedFigure 6 )。

[0058] Example 5: Preparation of Magnetically Regulated Anti-Counterfeiting Gel Based on Chitin Nanofiber Magnetic Fluid

[0059] Pour the magnetic fluid with an amino group content (0.5 - 2.0 mmol / g), mass concentration of 2.5%, magnetic particle content of 16%, magnetic particle size of 35 nm, and saturation magnetization of about 7 emu / g of chitin nanofiber DEChN prepared in Example 1 into a mold, such that the permeation and curing direction of the nanofiber magnetic fluid in the gas-phase coagulation bath is perpendicular to the magnetic field direction, and align it directionally for 25 min under the action of a magnetic field (magnetic field intensity 77 mT); then place it in an ammonia gas-phase coagulation bath (temperature 50 °C, curing time 1 h) for curing to form a directional anti-counterfeiting gel.

[0060] During the curing process, by adjusting the horizontal direction of the magnetic field to 0°, 45°, and 90°, the directional directions of the magnetic nanofibers in each curing layer are made different, so as to form a multi-layer hierarchical structure to achieve bar code-style binary information coding (0° represents "0", 45° or 90° represents "1", Figure 7 and Figure 8 as shown). After testing, the fiber orientation degree in the anti-counterfeiting gel can reach 73%, the storage modulus is 3.8 kPa, it has good magnetic responsiveness and mechanical properties, and is suitable for high-end anti-counterfeiting and information storage applications. Among them, the coding involved in the present invention is not limited to binary, and various compilation codes are within the scope of the present invention.

[0061] Example 6: Preparation of Anti-Counterfeiting Gel with Helical Directional Structure by Continuous Magnetic Field Rotation

[0062] Pour the magnetic fluid with a carboxyl group content (0.8 - 1.4 mmol / g), mass concentration of 1%, magnetic particle content of 8%, magnetic particle size of 17 nm, and saturation magnetization of about 8 emu / g of TOCN prepared in Example 1 into a flat mold and place it in an adjustable rotating magnetic field device. Initially set the magnetic field direction to 0° and fix it for 0.5 min to cure the first layer; then continuously adjust the magnetic field rotation speed (5.0 rpm / min) so that the horizontal direction of the magnetic field gradually rotates from 0° to 360°, matching the curing speed of the gas-phase coagulation bath (1.0 mm / min), and cure layer by layer to form a continuous anti-counterfeiting gel with a helical directional arrangement structure, and its pitch is controlled at 180 μm.

[0063] The pitches of the magnetically regulated anti-counterfeiting gels with helical directional arrangement structures prepared from different magnetic fluids at different curing speeds of the gas-phase coagulation bath and different magnetic field rotation speeds are as follows in the table:

[0064]

[0065]

[0066] Example 7: Preparation of biomimetic crab shell structure material based on anti-counterfeiting gel

[0067] The helically oriented anti-counterfeiting gel prepared in Example 6 was treated in a 1% - 5% sulfuric acid solution to remove magnetic nanoparticles; subsequently, it was immersed in a calcium ion solution (concentration 60 mmol / L) for mineralization reaction to promote the formation of an inorganic mineralized layer on the gel surface. Then, the mineralized gel was placed in an ammonia gas-phase coagulation bath for curing again (curing conditions: temperature 36°C, time 18 h). After curing, hot pressing treatment (hot pressing temperature 70°C, pressure 55 MPa, hot pressing time 8 min) was used to prepare a dry, lightweight and high-strength biomimetic crab shell structure material. The obtained material has a regular layered structure with alternating mineralized inorganic layers and nanofiber organic layers, a flexural strength of 128 MPa, a flexural modulus of 16 GPa, and a fracture strain of 0.77%, which is suitable for bone tissue engineering and bone replacement.

[0068] The mechanical properties of the biomimetic crab shell structure material under different conditions are as follows in the table:

[0069]

[0070]

[0071] Comparative Example 1: The magnetic fluid nanofibers prepared by the external addition method cannot respond to the magnetic field arrangement

[0072] Cellulose nanofibers (TOCN, carboxyl content 0.8 - 1.4 mmol / g) were configured into a mass concentration of 0.5% and ultrasonically treated in an ultrasonic disperser for 1 h, and then high-speed stirring was carried out for 30 min to try to obtain a uniform dispersion. 8% magnetic nanoparticles (particle size 17.5 nm) were added to the dispersion and stirred well, and then the system state was observed. It was found that due to the difficulty of uniformly loading the externally added magnetic nanoparticles on the nanofibers, the nanofibers in the prepared magnetic fluid could not quickly and effectively respond to the magnetic field, resulting in the inability to regulate the orderly arrangement of nanofibers through the magnetic field. Therefore, when preparing magnetic fluid by externally adding magnetic nanoparticles, the system cannot be effectively magnetically regulated, and magnetic regulation nanofiber anti-counterfeiting gel cannot be further prepared.

[0073] Comparative Example 2: Too high concentration of magnetic fluid nanofibers leads to a decrease in fluidity

[0074] Chitin nanofibers (TEMPO oxidized chitin nanofibers, TOChN carboxyl content 0.8 ~ 1.4mmol / g) were configured to 6%, and 1.194g of ferrous chloride tetrahydrate and 3.24g of ferric chloride hexahydrate were added thereto. After being fully stirred at room temperature, they were treated with an ultrasonic probe for 60s. Then, the mixture was poured into a 2L sealed container, and 30mL of 25% ammonia water was added at the same time. After passing through an ammonia bath, the reaction was allowed to stand at 25°C for 24h. After the reaction, the system state was observed after removing excess ions by dialysis. The experiment found that due to the high concentration of nanofibers, the viscosity of the system increased significantly, the fluid became thicker, and it was difficult to disperse evenly. At the same time, the nanofibers were severely agglomerated. Even after ultrasonic treatment for 1h, a stable dispersion could not be obtained, resulting in a significant decrease in the fluidity of the magnetic fluid, which could not be regulated by a magnetic field. Therefore, when the nanofiber concentration exceeds 3% (cellulose nanofiber) or 5% (chitin nanofiber), the viscosity of the system increases significantly, the magnetic fluid loses its good fluidity, and it is impossible to further prepare the magnetically regulated nanofiber anti-counterfeiting gel.

[0075] Comparative Example 3: High concentration of magnetic nanoparticles leads to self-gelation

[0076] The method of Example 1 was used to prepare chitin nanofibers, DEChN amino content (0.5-2.0mmol / g), mass concentration 2.5%, magnetic particle content 16%, magnetic particle size 35nm, and a magnetic fluid with a saturation magnetization intensity of about 7emu / g. The experiment found that due to the high concentration of magnetic nanoparticles, the magnetic fluid self-gelled before magnetic field regulation, the system thickened rapidly, and presented a gel-like solid state. The strong interaction between the magnetic nanofibers was enhanced, resulting in irreversible coagulation of the nanofibers, making it difficult to evenly disperse, and it was impossible to apply a magnetic field for directional arrangement, forming a disordered solidified structure in advance. When the concentration of magnetic nanoparticles exceeds 15%, the magnetic fluid will gel in advance, resulting in the inability to perform magnetic field regulation, and ultimately the inability to prepare magnetic regulation nanofiber anti-counterfeiting gel.

[0077] Comparative Example 4: The acid vapor coagulation bath time is too long, resulting in blurred patterns

[0078] The method of Example 1 was used to prepare a magnetic fluid with a carboxyl content of TOCN (0.8-1.4 mmol / g), a mass concentration of 1%, a magnetic particle content of 8%, and a magnetic particle size of 17.5 nm. After being treated in a 10mT magnetic field for 10 minutes, it was cured in an acetic acid vapor coagulation bath. In order to explore the effect of the acid vapor phase curing time on the anti-counterfeiting pattern, the curing time was extended to 2.5h. The experiment found that due to the long acid vapor phase curing time, the gel collapsed, the pattern boundary was blurred, and some areas had a non-uniform cured layer due to over-curing, which affected the anti-counterfeiting function ( Figure 13)。The acid gas phase coagulation bath time should be controlled between 1 min and 2 h. Exceeding 2 h will cause the anti-counterfeiting pattern to be distorted and reduce the anti-counterfeiting effect.

[0079] Comparative Example 5: Too fast magnetic field rotation speed leads to distortion of the helical structure

[0080] Prepare the magnetic fluid by the method of Example 1, with the carboxyl content of TOCN (0.8 - 1.4 mmol / g), mass concentration of 1%, magnetic particle content of 8%, and magnetic particle size of 17.5 nm, and place the magnetic fluid in an adjustable rotating magnetic field device for regulation. To study the influence of the magnetic field rotation speed on the helical orientation arrangement structure, set the magnetic field rotation speed to 10 rpm / min. The experiment found that due to the too fast magnetic field rotation speed, the helical orientation arrangement structure was distorted, unable to form a regular pitch, the magnetic nanofibers could not fully respond to the change of the magnetic field direction, and the arrangement was uneven, resulting in the lack of stability of the anti-counterfeiting gel structure and the difficulty in identifying the information coding. The magnetic field rotation speed should be controlled between 0.5 - 5.0 rpm / min. Exceeding 5.0 rpm / min will cause the helical structure to be distorted and affect the storage of anti-counterfeiting information.

[0081] Comparative Example 6: The nanofiber magnetic fluid fails to form a clear pattern in the magnetic field

[0082] Prepare the magnetic fluid with the carboxyl content of TOCN (0.8 - 1.4 mmol / g), mass concentration of 0.5%, magnetic particle content of 8%, and magnetic particle size of 17.5 nm by the method of Example 1, and use a magnet combination to form a specific anti-counterfeiting pattern and regulate the magnetic field direction. The experiment found that due to insufficient magnetic field strength (below 1 mT) or unstable magnetic field direction, the magnetic nanofibers failed to form the expected pattern, the pattern boundary was blurred, and it could not be clearly identified, resulting in the impairment of the information storage function. Therefore, the magnetic field regulation must ensure that the magnetic field strength is between 1 mT and 100 mT, otherwise a stable pattern cannot be formed, affecting the anti-counterfeiting performance.

[0083] Summary

[0084] The above-mentioned examples respectively used different pretreatment methods, nanofiber sources (cellulose or chitin) and curing conditions to prepare a magnetically regulated nanofiber anti-counterfeiting gel with high orientation, multi-layer hierarchical structure and information coding function, and further extended to the preparation of biomimetic crab shell structure materials. This method does not require complex chemical cross-linking, is simple to operate, green and environmentally friendly, significantly simplifies the preparation steps of the magnetic fluid, and at the same time realizes the fine regulation of the internal microstructure of the gel and the multi-functional integration, with broad application prospects.

[0085] In addition, in the present invention, since the pH adjustment is caused by gas-phase diffusion and liquid-phase diffusion, it will not cause deformation due to liquid impact, thus simplifying the steps of directional preparation, solving the disadvantage of extremely difficult control of the gel shape in traditional directional gel preparation, and can be applied to various customized shapes.

[0086] The above embodiments are only the best implementation manners of the present invention, and all kinds of modifications, equivalent substitutions and improvements within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0087] Figure 1 The regulation mechanism of the magnetic field on the nanofiber magnetic fluid is described in detail. The present invention combines magnetic field orientation and gas-phase coagulation bath to achieve layered orientation of the gel.

[0088] Figure 2 It is a schematic diagram of the orientation of magnetic nanofibers in a magnetic field and a photograph of the light transmission effect of the magnetic fluid under different magnetic field direction orientations, indicating that the magnetic fluid prepared by the present invention has a high degree of orientation in the magnetic field.

[0089] Figure 3 It is a schematic diagram and a photograph of the light reflection effect of the magnetic fluid under different magnetic field direction orientations. When the oriented fibers are perpendicular to the light incident direction, the light can be reflected, while when parallel to the incident direction, the light cannot be reflected, indicating that it has anisotropic light transmittance and can be used for anti-counterfeiting encryption.

[0090] Figure 4 It is an SEM image of the fiber network of the magnetically regulated nanofiber anti-counterfeiting gel prepared in Example 2 and its orientation degree calculation diagram. After orientation, the orientation of the nanofibers is as high as 77%.

[0091] Figure 5 It is the pattern display effect of the magnetic field on the oriented nanofiber magnetic fluid placed above the magnet in the gas-phase coagulation bath, indicating that the magnetic field pattern can be formed by the (combined magnetic field) magnetically regulated nanofiber anti-counterfeiting gel.

[0092] Figure 6 It is a patterned magnetically regulated nanofiber anti-counterfeiting gel, demonstrating that the magnetically regulated nanofiber gel has a high degree of free customizability. (By covering + two-step curing, the preparation of a magnetically regulated nanofiber anti-counterfeiting gel containing a covered film pattern can be achieved)

[0093] Figure 7, among 8 and 9, by adjusting the magnetic field direction, horizontal stripes can be obtained at different positions of the magnetically regulated nanofiber anti-counterfeiting gel. Therefore, by stepwise adjusting the magnetic field direction, light and dark stripes similar to barcodes can be formed in the gel. The preparation method is as shown in the figure. Combining binary codes, information can be stored in the gel through binary codes. By superimposing two codes, four groups of codes can be obtained. Matching them with different fiber directions respectively, and then encoding them into the gel by adjusting the magnetic field, a hydrogel with two codes can be obtained. As shown in the figure, the information observed at -45° is UBC, the information observed at +45° is NFU, and the information observed from the front is scrambled information. Thus, not only can multiple pieces of information be transmitted simultaneously, but the original information can also be hidden to achieve the effect of confidentiality.

[0094] Figure 10 This is a schematic diagram for preparing a magnetically regulated nanofiber anti-counterfeiting gel with a helical oriented arrangement structure by the present invention. As can be seen from the figure, the magnetic fluid can be placed above a rotating magnetic field to prepare a magnetically regulated nanofiber anti-counterfeiting gel with a helical oriented arrangement structure. The magnetic field rotates horizontally from 0° to 360° in cooperation with a gas-phase coagulation bath, and the nanofibers in the magnetic fluid are continuously gelated and fixed at different angles, thus preparing a magnetically regulated nanofiber anti-counterfeiting gel with a helical oriented arrangement structure.

[0095] Figure 11 A schematic diagram for efficiently preparing a biomimetic crab shell by hot pressing to remove excess water in the gel and further tightly bond the mineralized layer.

[0096] Figure 12 The biomimetic crab shell prepared by hot pressing has a layered structure similar to that of a natural crab shell.

[0097] Figure 13 Due to the too long acid gas-phase curing time, the gel collapses, the pattern boundaries are blurred, and non-uniform cured layers appear in some areas due to over-curing, resulting in the distortion of the anti-counterfeiting pattern and the reduction of the anti-counterfeiting effect.

Claims

1. A preparation method of a magnetically regulated nanofiber anti-counterfeiting gel, characterized in that, It includes the following steps: (1) Place the nanofiber magnetic fluid in the magnetic field generated by a magnet, regulate the distribution direction of the magnetic field to achieve the directional arrangement of magnetic nanofibers, and obtain a nanofiber magnetic fluid with a directional arrangement structure; (2) Solidify the above nanofiber magnetic fluid with a directional arrangement structure through a gas-phase coagulation bath to obtain a magnetically regulated nanofiber anti-counterfeiting gel; The magnet is at least one of a permanent magnet, a soft magnet, an electromagnet, and a special alloy magnet; the magnetic field strength is 1 mT to 100 mT; the nanofiber magnetic fluid is a nanocellulose magnetic fluid or a nanochitin magnetic fluid; the mass concentration of chitin nanofibers in the nanochitin magnetic fluid is 0.1% to 5%, and the mass concentration of cellulose nanofibers in the nanocellulose magnetic fluid is 0.1% to 3%.

2. The preparation method of a magnetically regulated nanofiber anti-counterfeiting gel according to any one of claim 1, characterized in that, Form different patterns by combining magnets to adjust the magnetic field distribution, orient the magnetic nanofibers, and then solidify through a gas-phase coagulation bath to prepare a magnetically regulated nanofiber anti-counterfeiting gel with an internal pattern.

3. The preparation method of a magnetically regulated nanofiber anti-counterfeiting gel according to any one of claim 1, characterized in that, In step (1), first cover the surface of the nanofiber magnetic fluid with films of different patterns; then adjust the distribution direction of the magnetic field to orient the magnetic nanofibers; after the solidification in step (2) is completed, remove the covering film, adjust the magnetic field distribution again, orient the magnetic nanofibers in a magnetic field distribution different from that when the film is covered, and finally prepare a magnetically regulated nanofiber anti-counterfeiting gel containing the pattern of the covering film through a gas-phase coagulation bath.

4. The preparation method of a magnetically regulated nanofiber anti-counterfeiting gel according to any one of claims 1, characterized in that, The penetration and solidification direction of the gas-phase coagulation bath of the nanofiber magnetic fluid is perpendicular to the magnetic field direction. Adjust the magnetic field to rotate horizontally from 0° to 360° to orient the magnetic nanofibers, and prepare a magnetically regulated nanofiber anti-counterfeiting gel with multiple spatially stratified structures with different orientations formed inside.

5. The preparation method of a magnetically regulated nanofiber anti-counterfeiting gel according to claim 4, characterized in that, The rotation speed of the magnetic field horizontally from 0° to 360° is 0.5 rpm / min to 5.0 rpm / min, the solidification speed of the gas-phase coagulation bath is 0.1 mm / min to 1.0 mm / min, and the nanofibers in the magnetic fluid are continuously gelled and fixed at different angles to prepare a magnetically regulated nanofiber anti-counterfeiting gel with a helical directional arrangement structure; the pitch in the helical directional arrangement structure is 100 μm to 300 μm.

6. The preparation method of a magnetically regulated nanofiber anti-counterfeiting gel according to any one of claims 1-5, characterized in that, The content of magnetic nanoparticles in the nanofiber magnetic fluid is 1% to 15%, the size of the magnetic particles is 5 to 30 nm, and the saturation magnetization intensity is 1 to 15 emu / g.

7. A method for preparing a magnetically regulated nanofiber anti-counterfeiting gel according to any one of claims 1-5, characterized in that, The gas-phase coagulation bath is a volatile acidic coagulation bath or an alkaline ammonia coagulation bath. The acidic coagulation is hydrochloric acid, acetic acid, and methacryloyl chloride. The time of the coagulation bath is 1 min to 2 h, and the temperature is 1 °C to 60 °C.

8. A magnetically regulated nanofiber anti-counterfeiting gel, which is prepared by using the preparation method of the magnetically regulated nanofiber anti-counterfeiting gel according to any one of claims 1-7, and is characterized in that, The fibers in the magnetically regulated nanofiber anti-counterfeiting gel have a highly ordered arrangement, the arrangement direction is consistent with the magnetic field direction, the orientation degree can reach 50 - 90%, and the gel storage modulus can reach 1.5 KPa to 30 KPa.

9. Application of a magnetically regulated nanofiber anti-counterfeiting gel in a biomimetic crab shell material, characterized in that, The magnetically controlled nanofiber anti-counterfeiting gel with a helical and oriented arrangement structure, prepared by the preparation method of a magnetically controlled nanofiber anti-counterfeiting gel according to claim 5, is immersed in a calcium ion solution after pickling to remove magnetic nanoparticles, and then in an ammonia gas coagulation bath to obtain a hydrogel with a superhelical nanofiber skeleton and an inorganic layered mineralized biomimetic structure. Finally, the above gel is hot-pressed and dried to obtain a lightweight and high-strength biomimetic crab shell structure material.

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