A photo-patternable thermosensitive hydrogel and its use

Abstract

The application discloses a light-induced patternable temperature-sensitive hydrogel and application thereof. The hydrogel comprises a temperature-sensitive polymer, acrylamide and a photoinitiator, wherein the temperature-sensitive polymer, acrylamide and photoinitiator are mixed by directly adding in a gel precursor or by soaking after gel forming. The hydrogel of the application can display corresponding patterns in a certain temperature range after spatial selective irradiation, and the temperature of the pattern display is different when the irradiation time is different, so that the dynamic change of the pattern is realized, and the hydrogel can be applied to light-induced patterns, information encryption, information storage or anti-counterfeiting. The preparation method of the hydrogel is simple, and the pattern can be controlled and dynamically responded without light-sensitive modification of the temperature-sensitive polymer, so that the hydrogel has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of information function in smart materials, specifically relating to a photo-patternable thermosensitive hydrogel and its application in information storage, encryption, and anti-counterfeiting. Background Technology

[0002] Thermosensitive hydrogels are a class of functional soft materials capable of undergoing reversible phase transitions in response to changes in external temperature. They typically rely on thermosensitive polymer systems with a low critical solution temperature (LCST). Within a specific temperature range, they exhibit a phase transition from dissolution to insolubility in water. During this phase transition, the dispersed phase size gradually increases, causing scattering of incident visible light and macroscopically displaying a reversible change from transparent to turbid states. Because these changes can be directly identified by the naked eye or simple optical methods, thermosensitive hydrogels have attracted widespread attention in recent years for applications such as thermochromic smart windows, information displays, anti-counterfeiting labels, and information encryption.

[0003] In information encryption applications, ideal hydrogel materials usually need to meet the following requirements at the same time: (1) They can form spatially resolved information structures or patterns inside the material; (2) Information is not easily read directly under unauthorized conditions to reduce the risk of information leakage; (3) Decryption conditions can be precisely defined, for example, information can only be read correctly within a specific temperature range; (4) The material system has good versatility and reusability, which is convenient for practical applications.

[0004] The existing thermosensitive hydrogels have the following main shortcomings in information encryption applications.

[0005] First, spatial patterning of materials is a fundamental prerequisite for information encryption applications using thermosensitive hydrogels. However, conventional thermosensitive hydrogels are usually based on polymer systems with low critical solution temperatures (LCSTs), and their phase behavior is mainly determined by temperature and solvent environment. They are generally not sensitive to light stimulation, making it difficult to achieve spatially controllable patterning directly through ultraviolet lithography or mask exposure.

[0006] A few studies have achieved photolithographic patterning of thermosensitive hydrogels by photosensitive modification of thermosensitive polymers, introducing photosensitive groups or special monomers into the polymer structure, and combining this with complex synthesis or crosslinking designs. However, these methods usually rely on specific monomer structures and customized synthesis routes, resulting in limited material versatility, complex preparation processes, and difficulty in directly applying them to existing conventional thermosensitive polymer systems. This limits their freedom of material selection, process simplicity, and large-scale application.

[0007] Secondly, regarding information security, existing information encryption systems based on thermosensitive hydrogels generally suffer from a low decryption threshold. Most thermosensitive hydrogels' encryption mechanisms rely solely on the reversible switching between their transparent and turbid states under temperature changes. When the ambient temperature rises above the phase transition temperature, the hidden information can be directly identified. This decryption method is usually not subject to strict conditions and can achieve information reading over a wide temperature range, making encrypted information easily accessible to unauthorized personnel through simple heating methods.

[0008] Because the aforementioned decryption process lacks effective constraints, existing temperature-sensitive hydrogels can often only achieve low-level information hiding at the "visible / invisible" level, making it difficult to meet the needs of applications with high information security requirements, such as anti-counterfeiting labels, secure storage, or multi-level encrypted displays. The fact that this information can be correctly interpreted under any high-temperature conditions significantly increases the risk of information leakage.

[0009] Furthermore, in terms of controlling information decryption conditions, some existing research has focused on fluorescent hydrogel systems. By regulating fluorescence emission behavior, introducing multilayer structures, or constructing composite response systems, information can be displayed or hidden under specific stimulus conditions. These approaches typically rely on changes in fluorescence intensity, wavelength, or luminescence switching behavior to achieve information encryption and decryption.

[0010] However, the above methods are mainly applicable to fluorescent hydrogel systems, whose information reading depends on optical excitation and emission processes. This is fundamentally different from the working mechanism of thermosensitive hydrogels based on phase behavior changes, and it is difficult to directly transfer or apply them to thermosensitive hydrogel systems.

[0011] Therefore, how to achieve photo-patterning of thermosensitive hydrogels without photosensitive modification of thermosensitive polymers or complex synthesis, and further construct a temperature-locked information encryption system that can correctly decrypt within a limited temperature range and present erroneous or undecryptable information at other temperatures, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0012] Therefore, one objective of this invention is to provide a photo-patternable thermosensitive hydrogel, which comprises a thermosensitive polymer, acrylamide (AM), and a photoinitiator. The hydrogel is a pre-formed system containing at least a thermosensitive polymer, acrylamide, and a photoinitiator. The thermosensitive polymer is a conventional LCST-type polymer without introduced photosensitive groups. Acrylamide is used to modulate the local solubility of the thermosensitive polymer under spatially selective irradiation, thereby altering the phase transition temperature. The photoinitiator assists in irradiation-induced changes in the AM state. Thus, without irradiation, the hydrogel exhibits spatially uniform thermosensitive phase behavior; after spatially selective irradiation, at least two spatial regions are formed, in which the phase transition temperatures of the thermosensitive polymer differ, resulting in distinguishable optical states at the same external temperature. During the photo-patterning process of this hydrogel, the main chain or side chain structure of the thermosensitive polymer is not altered; the difference in phase transition temperature originates entirely from the modulation of solubility by changes in the AM state.

[0013] Furthermore, LCST-type thermosensitive polymers include, but are not limited to, polymers containing ether bonds such as polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide block polyether, hydroxypropyl cellulose, polyoxazoline, and polyvinyl methyl ether; and thermosensitive polymers containing amino or amide groups such as N,N-dimethylaminoethyl methacrylate, polyN,N-dimethylacrylamide, polyN,N-isopropylacrylamide, and acrylamide-diacetone acrylamide copolymer.

[0014] A second objective of this invention is to provide a method for preparing the aforementioned photo-patternable thermosensitive hydrogel, which includes the step of incorporating a thermosensitive polymer, acrylamide, and a photoinitiator into the hydrogel matrix. The hydrogel matrix can be a common hydrogel such as polyacrylamide, polyvinyl alcohol, sodium alginate, or agarose, prepared by conventional methods.

[0015] Furthermore, the method of incorporation is to directly incorporate one or more of acrylamide, thermosensitive polymer and initiator into the gel precursor or to incorporate them by soaking after gel formation.

[0016] Specifically, for substances such as acrylamide, thermosensitive polymers, and initiators, if a certain substance has an adverse effect on the gel formation process or the performance of the molded gel, the substance shall be added by soaking after molding; otherwise, it is preferable to mix it directly into the gel precursor.

[0017] For example, when polyacrylamide is used as the hydrogel backbone, since acrylamide and the initiator themselves participate in the polymerization process of gel formation, only the temperature-sensitive polymer and the precursor are mixed first. Then, the mixed solvent of acrylamide and initiator is incorporated into the already formed gel by soaking. The specific operation method includes: mixing a set amount of thermosensitive polymer, acrylamide monomer, initiator, and crosslinking agent in water to form a gel precursor, and then initiating polymerization (the initiation method varies depending on the type of initiator; if it is a photoinitiator, polymerization is initiated by irradiation; if it is a thermal initiator, polymerization is initiated by heating; if it is a redox initiation system, polymerization can generally be initiated at room temperature after mixing the two components of the initiation system). After reacting for a certain period of time, a thermosensitive hydrogel body is obtained (at this time, because of the thermosensitive polymer, the transmittance of the hydrogel body can change with temperature, but either the entire gel is transparent or the entire gel is cloudy, and photo-patterning cannot be achieved); then, the obtained thermosensitive hydrogel body is immersed in an aqueous solution containing acrylamide and initiator (and may also contain crosslinking agent) to enter the thermosensitive hydrogel body and obtain a thermosensitive hydrogel that can be photo-patterned, that is, the immersed thermosensitive hydrogel contains a large amount of monomeric acrylamide, so that polymerization can be initiated under irradiation to achieve photo-patterning.

[0018] When polyvinyl alcohol and borax crosslinking network are selected as the gel backbone, the gel formation process is not achieved through monomer polymerization, but through the direct interaction between the polymer and the crosslinking agent. Therefore, acrylamide does not participate in this process, and direct mixing with the precursor is preferred. First, a predetermined amount of polyvinyl alcohol, thermosensitive polymer, acrylamide, and initiator are dissolved in water to obtain a mixed solution. Then, a predetermined amount of crosslinking agent (borax solution) is added to the solution, and after standing for a certain period of time, a patternable thermosensitive hydrogel is obtained.

[0019] When polyethyleneimine and diglycidyl ether crosslinking agents are selected as the gel backbone, the gel formation process is not achieved through monomer polymerization, but rather through the direct interaction between the polymer and the crosslinking agent. Acrylamide does not participate in this process, so direct mixing with the precursor is also preferred. First, a predetermined amount of polyethyleneimine, thermosensitive polymer, acrylamide, and initiator are dissolved in water to obtain a mixed solution. Then, a predetermined amount of crosslinking agent (diglycidyl ether reagent) is added to the solution, and after standing for a certain period of time, a patternable thermosensitive hydrogel is obtained.

[0020] When a crosslinked network of polyvinyl alcohol and glutaraldehyde is selected as the gel backbone, the gel formation process is not achieved through monomer polymerization, but rather through the direct interaction between the polymer and the crosslinking agent. Therefore, acrylamide does not participate in this process, making direct mixing with the precursor the preferred method. Since the crosslinking reaction of polyvinyl alcohol and glutaraldehyde is very slow and requires acid catalysis, the two can be mixed first, with only the catalyst added at the end. First, a predetermined amount of polyvinyl alcohol, the thermosensitive polymer, acrylamide, the initiator, and glutaraldehyde are dissolved in water to obtain a mixed solution. Then, a predetermined amount of catalyst (an acid, such as acetic acid or hydrochloric acid) is added to the solution, and after standing for a certain period, a patternable thermosensitive hydrogel is obtained.

[0021] Since there are many methods for preparing conventional hydrogels, it is impossible to list them all. The specific way of mixing acrylamide and thermosensitive polymer depends on the specific properties of the gel skeleton. It is only necessary that the final thermosensitive hydrogel contains non-covalently linked thermosensitive polymer, a large amount of unpolymerized acrylamide monomer, and photoinitiator.

[0022] The third objective of this invention is to provide a method for photo-patterning thermosensitive hydrogels, comprising the following steps:

[0023] 1) Spatially selectively irradiate a predetermined area of ​​the above-mentioned thermosensitive hydrogel to form at least two spatial regions inside the hydrogel;

[0024] 2) The irradiated hydrogel is placed under certain external temperature conditions to obtain a pattern with distinguishable optical states.

[0025] Furthermore, the irradiation is UV irradiation; the irradiation method may include direct writing, photolithography, photomask, etc.

[0026] Furthermore, the irradiation time varies in different regions during the spatial selective irradiation. This difference in irradiation time leads to differences in AM state, resulting in different phase transition temperatures of the thermosensitive polymer in different regions. This creates distinguishable optical patterns, which exhibit changes within a continuously varying temperature range. By adjusting the UV irradiation time of each region, the pattern display temperature can be precisely controlled. The pattern can dynamically evolve in line width and clarity as the temperature changes, achieving a temperature-dependent decryptable pattern.

[0027] Furthermore, the aforementioned certain external temperature condition is a temperature increase starting from 0 to 10 degrees Celsius.

[0028] The fourth objective of this invention is to provide applications of hydrogels in photolithographic patterns, information encryption, information storage, or anti-counterfeiting.

[0029] Furthermore, the photo-induced pattern is a dynamically changing pattern. Different spatial regions have different irradiation times, resulting in different patterns at different temperatures during external heating. This dynamic change allows for better application in information encryption, storage, or anti-counterfeiting.

[0030] Beneficial effects:

[0031] (1) Simple operation and wide applicability: No photosensitization modification or complex synthesis is required, and it is applicable to a variety of LCST polymers and hydrogel matrices;

[0032] (2) The temperature range of the pattern display is increased, and the pattern is controllable and dynamically responsive: By adjusting the UV irradiation time, the phase transition temperature of different regions can be precisely controlled to achieve temperature-dependent pattern display;

[0033] (3) High information security: The pattern changes dynamically with temperature, which can realize temperature-locked information encryption;

[0034] (4) High scalability: The method is simple, scalable, and easy to prepare on a large scale. Attached Figure Description

[0035] Figure 1 This illustrates the effect of different UV irradiation times on the phase transition temperature of a pattern before and after irradiation in Example 1 of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating the variation of pattern linewidth with temperature at different temperatures in Embodiment 2 of the present invention;

[0037] Figure 3 This is a schematic diagram of temperature-locked information encryption using the temperature-sensitive polymer L62 hydrogel in Embodiment 3 of the present invention;

[0038] Figure 4 This is a schematic diagram of temperature-locked information encryption using the thermosensitive polymer polyN-isopropylamide hydrogel in Example 4 of the present invention.

[0039] Figure 5 This is a schematic diagram of temperature-locked information encryption using the thermosensitive polymer polyhydroxypropyl cellulose hydrogel in Embodiment 5 of the present invention.

[0040] Figure 6 This is a schematic diagram of the hydrogel temperature-locked information encryption method in the gel precursor of Embodiment 6 of the present invention;

[0041] Figure 7 This is a schematic diagram of the temperature-locked dynamic information encryption of the temperature-sensitive polymer L62 hydrogel in Embodiment 7 of the present invention;

[0042] Figure 8 This is a schematic diagram of the temperature-locked dynamic information encryption of the temperature-sensitive polymer L62 hydrogel in Embodiment 8 of the present invention;

[0043] Figure 9 This is a schematic diagram illustrating the encryption of the temperature-locking QR code information of the temperature-sensitive polymer L62 hydrogel in Embodiment 9 of the present invention.

[0044] Figure 10 This is a schematic diagram of the temperature-locked dynamic information encryption of the temperature-sensitive polymer polyhydroxypropyl cellulose hydrogel in Embodiment 10 of the present invention.

[0045] Figure 11 This is a schematic diagram of temperature-locked information encryption using the temperature-sensitive polymer AM-co-DAAM hydrogel in Embodiment 11 of the present invention. Detailed Implementation

[0046] The present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention. The present invention is not limited to the following embodiments or examples. Any modifications and variations made without departing from the spirit of the present invention should be included within the scope of the present invention. Unless otherwise specified, the experimental materials or reagents used in the following embodiments are all commercially available products; unless otherwise specified, the percentages in the following embodiments are all mass fractions; unless otherwise specified, the solvent for the solutions in the following embodiments is deionized water; information on the main raw materials and reagents used in the following embodiments is shown in Table 1.

[0047] Table 1 Main raw materials and reagents for the experiment

[0048]

[0049] Example 1:

[0050] 0.75 g AM, 0.042 g L62, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) were added to 11.9 g H2O (resulting in mass fractions of 5.3%, 0.3%, 5.7%, and 4.2%, respectively), mixed thoroughly, and 3.5 g was placed in a 10 mm glass cuvette. Subsequently, the mixture was placed in a UV curing chamber and irradiated for 15 min to obtain the original thermosensitive hydrogel with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 0.53477 g of 60% AM solution, 0.0667 g of crosslinking agent solution (3wt%), and 0.066 g of photoinitiator I2959 ethanol solution (1.2wt%) were added to the original thermosensitive hydrogel. The mixture was left to stand for 3 days to ensure uniform diffusion and allow excess water from the soaking process to evaporate completely, thus obtaining a photolithographically patternable thermosensitive hydrogel.

[0051] Different hydrogel samples were irradiated in a UV curing chamber (peak wavelength 365 nm, average irradiance 179 mW / cm²) for 3, 5, 7, 10, and 13 min, respectively. Their transmittance at different temperatures was measured using an L5 UV-Vis spectrophotometer (INESA Group Ltd.) at a wavelength of 500 nm. The optical path length of the cuvette was 10 mm, and its temperature was controlled with an accuracy of ±0.1℃ using a metal clamp connected to a constant temperature water bath (OWELL, Hangzhou Qiwei Instrument Co., Ltd.). Each sample was equilibrated at the target temperature for 5 minutes before measurement. The temperature at which transmittance decreased by 50% was defined as the phase transition temperature (T0). cp ). (The result is as follows) Figure 1 The graph showing the relationship between irradiation time and phase transition temperature of the system shows that the longer the irradiation time, the lower the phase transition temperature. Moreover, the phase transition temperature changes more rapidly from irradiation time of 3 to 10 minutes, and then tends to slow down. It can be seen that the hydrogel of the present invention can increase and adjust the temperature range of pattern display through irradiation, providing the possibility for dynamic changes in the pattern.

[0052] The phase transition temperature of the un-soaked AM hydrogel (i.e., the original thermosensitive hydrogel) was measured using the same method and was approximately 23.5°C, significantly lower than the phase transition temperature of the photolithographically patternable thermosensitive hydrogel irradiated for 10 minutes. This demonstrates that the pattern display temperature range of the thermosensitive hydrogel of this invention is greatly increased.

[0053] Example 2:

[0054] 0.75 g AM, 0.042 g L62, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) were added to 11.9 g H2O and mixed well. The mixture was then poured into a 100×100×15 mm container. 3 The sample was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing oven (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the obtained hydrogel, making the AM monomer account for approximately 10% of the mass fraction of the hydrogel. The sample was stored for two days to ensure uniform diffusion, and excess water from the soaking process was allowed to evaporate completely naturally to obtain a photolithographically patternable thermosensitive hydrogel.

[0055] The above samples were prepared into hydrogels with a thickness of approximately 2 mm in circular glass petri dishes. A pattern mask with 1 mm, 3 mm, and 5 mm stripes was applied to the petri dishes to completely block incident light. Subsequently, the hydrogels were irradiated from the bottom (λpeak = 365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for 10 min.

[0056] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 2 As shown, the gel gradually reveals stripes from a transparent state, then the stripes widen with increasing temperature until they become blurred. Figure 3 The diagram shows the relationship between the line width of the pattern and temperature. It can be seen that the pattern begins to appear at 25 ℃, and the line width increases as the temperature rises. At 40 ℃, the average line width of the stripes reaches 2.4 times the original line width. Furthermore, the line width gradually decreases as the temperature decreases. These characteristics are significantly different from those of patterns in existing schemes, where the line width either does not change significantly with temperature or undergoes irreversible changes.

[0057] Example 3:

[0058] Add 0.75 g AM, 0.042 g L62, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O, mix well, and pour into a 100×100×15 mm container. 3 The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing chamber (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure uniform diffusion and to allow excess water from the soaking process to evaporate.

[0059] The sample was prepared into a hydrogel approximately 2 mm thick in a round glass petri dish. A pattern mask was formed by completely blocking the incident light with black PET polyester film tape and attaching it to the petri dish. Subsequently, the hydrogel was irradiated from the bottom (λpeak = 365 nm) with an average intensity of 179 mW / cm² using an LED UV curing chamber (BX-203) for 10 min.

[0060] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 3As shown, the gel begins to show a pattern at 25 ℃ from its original transparent state. When the temperature exceeds 30 ℃, the pattern gradually becomes blurred, indicating that the system has the ability to perform photo-patterning and can be used for information encryption.

[0061] Example 4:

[0062] Add 0.75 g AM, 0.14 g poly-N-isopropylacrylamide, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O (resulting in mass fractions of 5.3%, 1%, 5.6%, and 4.2%, respectively), mix well, and pour into a 100×100×15 mm container. 3 The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing chamber (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure uniform diffusion and to allow excess water from the soaking process to evaporate.

[0063] The sample was prepared into a hydrogel with a thickness of approximately 2 mm in a circular glass petri dish. A mask with a pattern "B" was attached to the petri dish to completely block the incident light. Subsequently, the hydrogel was irradiated from the bottom (λpeak=365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for 10 min.

[0064] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 4 As shown, the gel begins to display the pattern "B" from its original transparent state at 30°C. When the temperature exceeds 35°C, the pattern gradually becomes blurred, indicating that the system has the ability to perform photo-patterning and can be used for information encryption.

[0065] Example 5:

[0066] Add 0.75 g AM, 0.14 g hydroxypropyl cellulose, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O (resulting in mass fractions of 5.3%, 1%, 5.6%, and 4.2%, respectively), mix well, and pour into a 100×100×15 mm container. 3The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing oven (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiation intensity of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure complete diffusion and to allow excess water from the soaking process to evaporate.

[0067] The sample was prepared into a hydrogel with a thickness of approximately 2 mm in a circular glass petri dish. A mask with a "C" pattern was attached to the petri dish to completely block the incident light. Subsequently, the hydrogel was irradiated from the bottom (λpeak=365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for 10 min.

[0068] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 5 As shown, the gel begins to display the pattern "C" from a transparent state at 40 ℃. When the temperature exceeds 48 ℃, the pattern gradually becomes blurred, indicating that the system has the ability to perform photo-patterning and can be used for information encryption.

[0069] Example 6:

[0070] Weigh 5 g of PVA and add it to 95 g of deionized water. Stir at 90 °C for 30 min to obtain a 5 wt% PVA aqueous solution. Then, thoroughly mix 30 g of the 5 wt% PVA solution, 0.075 g of 50 wt% glutaraldehyde solution, 1.7 g of AM, 0.126 g of L62, 1 g of 3 wt% crosslinking agent solution, and 1 g of 1.2 wt% photoinitiator 2959 ethanol solution. Next, add four drops of 2 mol / L HCl to adjust the pH to approximately 2. Pour 14 g of the solution into a 100×100×15 mm container. 3 PVA-GA-AM-5%-L62-0.3% hydrogel was obtained by placing the gel in a glass culture dish mold at 25°C for 24 h.

[0071] The sample was prepared into a hydrogel with a thickness of approximately 2 mm in a circular glass petri dish. A mask with a pattern "A" was attached to the petri dish to completely block the incident light. Subsequently, the hydrogel was irradiated from the bottom (λpeak=365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for 10 min.

[0072] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 6 As shown, the gel begins to display the pattern "A" from a transparent state to 28 ℃. When the temperature exceeds 35 ℃, the pattern gradually becomes blurred, indicating that the system has the ability to perform photo-patterning and can be used for information encryption.

[0073] Example 7:

[0074] Add 0.75 g AM, 0.042 g L62, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O, mix well, and pour into a 100×100×15 mm container. 3 The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing oven (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiation intensity of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure complete diffusion and to allow excess water from the soaking process to evaporate.

[0075] The samples were prepared into hydrogels approximately 2 mm thick in circular glass petri dishes. A mask with the pattern "Welcome to Chongqing" was formed by completely blocking incident light and attaching it to the petri dish. Subsequently, the hydrogels were irradiated from the bottom (λpeak = 365 nm) with an average intensity of 179 mW / cm² using an LED UV curing chamber (BX-203). The "You" pattern was irradiated for 5 min, the "Welcome" pattern for 7 min, and the "Chongqing" pattern for 10 min.

[0076] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 7 As shown, the gel gradually displays different patterns from a transparent state. The characters "Chongqing" appear first, which has the longest irradiation time, followed by "Welcome". The character "You" appears last, which has the shortest irradiation time, and then the pattern becomes blurred, achieving dynamic changes in the pattern. This can be used for information encryption.

[0077] Example 8:

[0078] Add 0.75 g AM, 0.042 g L62, 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O, mix well, and pour into a 100×100×15 mm container. 3The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing oven (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiation intensity of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinking agent solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure complete diffusion and to allow excess water from the soaking process to evaporate.

[0079] The sample was prepared into a hydrogel approximately 2 mm thick in a circular glass petri dish. Black PET polyester film tape, completely blocking the incident light, was applied to the petri dish to form a mask for a seven-stroke pattern. Subsequently, the hydrogel was irradiated from the bottom (λpeak = 365 nm) at an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203). Different strokes of the seven-stroke pattern were irradiated for different durations: the "8" area was irradiated for 5 min, the "9" area for 7 min, and the "3" area for 10 min.

[0080] Observe the optical changes of the irradiated hydrogel in the range of 20–40 °C, such as Figure 8 As shown, the gel gradually displays different patterns as it transitions from a transparent state. At 25°C, a faint "3" pattern first appears in the seven-stroke tube. When the temperature rises to 28°C, an additional stroke appears, displaying a "9" pattern. When the temperature rises to 35°C, yet another stroke appears, displaying an "8" pattern. From... Figure 9 As can be seen, the hydrogel displays different patterns at different temperatures, providing different information. For example, it displays "3" at 25℃, "9" at 28℃, and "8" at 35℃. Unlike traditional patterned hydrogels, where the specific encrypted information within the hydrogel can be fully understood simply by heating, this method... Figure 9 The system can only know the specific encrypted information (number) if it knows the specific decryption temperature. Figure 9 The system thus achieves temperature-locked information encryption by controlling the irradiation time of different regions of the hydrogel to display different patterns and information at different temperatures.

[0081] Example 9:

[0082] Add 5.25 g AM, 0.294 g L62, 5.6 g crosslinking agent aqueous solution (3wt%), and 4.2 g photoinitiator I2959 ethanol solution (1.2wt%) to 84 g H2O, mix well, and pour into a 200×200×20 mm container. 3The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing oven (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 56 g of 20% AM solution, 0.7 g of crosslinking agent solution (3 wt%), and 0.7 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel to bring the mass fraction of AM monomer to approximately 10%. The mixture was stored for two days to ensure complete diffusion and to allow excess water from the soaking process to evaporate.

[0083] The sample was prepared into a hydrogel approximately 2 mm thick in a circular glass petri dish. A mask with a QR code pattern was formed by completely blocking incident light and attaching it to the petri dish using black PET polyester film tape. Subsequently, the hydrogel was irradiated from the bottom (λpeak = 365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for a fixed 10 min.

[0084] Observe the optical changes of the hydrogel in the range of 20–40 °C, such as Figure 10 As shown, during the heating process, the gel transitions from a transparent state to displaying a clear QR code. As the temperature further increases, the line width of the QR code pattern becomes blurred. Below 25°C, the QR code pattern is incomplete, making it impossible to decrypt the information using a mobile app. Above 29°C, the QR code's line width increases, and even if the pattern is displayed, the clarity exceeds the QR code's error tolerance, preventing decryption via a mobile app. Only within the temperature range of 25°C to 29°C can the encrypted information in the hydrogel be decrypted via a mobile app, thus achieving temperature-locked information encryption. This differs from... Figure 7 and Figure 8 Temperature lock information encryption mode in the middle, Figure 9 It utilizes temperature to control the system linewidth and combines it with QR codes to achieve a temperature-locked encryption mode that can only be decrypted within a specific temperature range.

[0085] Example 10:

[0086] Add 0.75g AM, 0.14g hydroxypropyl cellulose, 0.8g crosslinking agent aqueous solution (3wt%), and 0.6g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9g H2O, mix well, and pour into a 100×100×15mm container. 3In a glass petri dish mold. Subsequently, it was placed in a UV curing box (BX-203 of Shenzhen Bestar Technology Co., Ltd.) and irradiated for 15 min with a peak wavelength of 365 nm and an average irradiation intensity of 179 mW / cm². 8 g of 20% AM solution, 0.1 g of crosslinker solution (3 wt%), and 0.1 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the obtained hydrogel, so that the mass fraction of AM monomer was about 10%. It was stored for two days to ensure thorough diffusion and to evaporate the excess water during the soaking process.

[0087] The sample was made into a hydrogel with a thickness of about 2 mm in a circular glass petri dish. A black PET polyester film tape completely blocked the incident light and was pasted on the petri dish to form a mask template with the pattern of "forest". Subsequently, the hydrogel was irradiated from the bottom (λpeak = 365 nm) with an average intensity of 179 mW / cm² through an LED ultraviolet curing box (BX-203), with one "wood" irradiated for 17 min and "forest" irradiated for 10 min.

[0088] Observe the optical changes of the irradiated hydrogel within the range of 33–50 °C, such as Figure 10 shown. The gel gradually shows different patterns from the transparent state. The character "wood" with a longer irradiation time (17 minutes) is最先显示 (the first to show) at 38 °C. When the temperature rises to 43 °C, the other character "wood" with an irradiation time of 10 minutes also shows up, and the hydrogel presents the pattern of the character "forest". From Figure 10 it can be seen that even if the thermosensitive polymer is replaced, the entire hydrogel can still show different patterns at different temperatures, providing differential information. Different from traditional patterned hydrogels, as long as they are heated, the specific encrypted information in the hydrogel can be completely known. Figure 10 In the system of , only by knowing the specific decryption temperature can the specific encrypted information be known. Thus, by regulating the irradiation time of different regions of the hydrogel, different patterns are shown at different temperatures, showing different information, so as to achieve temperature-locked information encryption.

[0089] Example 11:

[0090] Weigh 0.75 g of AM, 0.75 g of diacetone acrylamide, 0.88 g of sodium bisulfite aqueous solution (6%), and 0.44 g of potassium persulfate aqueous solution (6%), add them to 10 g of H2O, and mix well. After dialysis for 24 h, it was put into an oven and dried at 50 °C for 24 h to obtain the copolymer P(AM-co-DAAM) of acrylamide and diacetone acrylamide, and this copolymer also has the thermosensitive property of LCST.

[0091] It should be noted that the part "最先显示" in the translation of needs to be further clarified according to the accurate meaning in the original context to ensure a more precise translation.Add 0.75 g AM, 0.7 g P (AM-co-DAAM), 0.8 g crosslinking agent aqueous solution (3wt%), and 0.6 g photoinitiator I2959 ethanol solution (1.2wt%) to 11.9 g H2O, mix well, and pour into a 100×100×15 mm container. 3 The mixture was placed in a glass culture dish mold. Subsequently, it was placed in a UV curing chamber (Shenzhen Bestech Technology Co., Ltd. BX-203) and irradiated for 15 min, with a peak wavelength of 365 nm and an average irradiance of 179 mW / cm². 8 g of 40% AM solution, 0.2 g of crosslinking agent solution (3 wt%), and 0.2 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added to the resulting hydrogel; 8 g of 5% AM solution, 0.025 g of crosslinking agent solution (3 wt%), and 0.05 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added; and 8 g of 2.5% AM solution, 0.0125 g of crosslinking agent solution (3 wt%), and 0.0125 g of photoinitiator I2959 ethanol solution (1.2 wt%) were added. The mass fractions of AM monomers were approximately 10%, 20%, 2.5%, and 1.25%, respectively. The mixture was stored for two days to ensure complete diffusion and to allow excess water from the soaking process to evaporate.

[0092] The sample was prepared into a hydrogel with a thickness of approximately 2 mm in a circular glass petri dish. A mask with an "E" pattern was attached to the petri dish to completely block the incident light. Subsequently, the hydrogel was irradiated from the bottom (λpeak=365 nm) with an average intensity of 179 mW / cm² in an LED UV curing chamber (BX-203) for a fixed irradiation time of 10 min.

[0093] Observe the optical changes of the irradiated hydrogel in the range of 33–50 °C, such as Figure 11 As shown, the gel begins to display the pattern "E" from a transparent state to 25 ℃. When the temperature exceeds 35 ℃, the pattern gradually becomes blurred, indicating that the system has the ability to perform photo-patterning and can be used for information encryption.

[0094] The conventional techniques and solutions not described in detail in the above embodiments are all well known in the art, and therefore will not be elaborated upon here. The above embodiments and / or experimental examples describe the preferred embodiments of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A photo-patternable thermosensitive hydrogel, characterized in that, The hydrogel contains a thermosensitive polymer, acrylamide, and a photoinitiator.

2. The hydrogel as described in claim 1, characterized in that, The thermosensitive polymer is an LCST type thermosensitive polymer.

3. The hydrogel as described in claim 2, characterized in that, The LCST-type thermosensitive polymer includes one or more of the following: polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide block polyether, hydroxypropyl cellulose, polyoxazoline, polyvinyl methyl ether, N,N-dimethylaminoethyl methacrylate, polyN,N-dimethylacrylamide, polyN,N-isopropylacrylamide, and acrylamide-diacetone acrylamide copolymer.

4. The method for preparing the hydrogel according to any one of claims 1-3, characterized in that, This includes the step of incorporating a thermosensitive polymer, acrylamide, and a photoinitiator into the hydrogel matrix.

5. The preparation method according to claim 4, characterized in that, The method of mixing is to directly mix one or more of acrylamide, thermosensitive polymer and initiator into the gel precursor or to mix them by soaking after gel formation.

6. A method for photo-patterning thermosensitive hydrogels, characterized in that, Includes the following steps: 1) Apply spatially selective irradiation to a predetermined region of the hydrogel according to any one of claims 1-3, so that at least two spatial regions are formed inside the hydrogel; 2) The irradiated hydrogel is placed under certain external temperature conditions to obtain a pattern with distinguishable optical states.

7. The method as described in claim 6, characterized in that, Different spatial irradiation times are used in the aforementioned space selective irradiation.

8. The method as described in claim 7, characterized in that, The specified external temperature condition is to start heating from 0 to 10 degrees Celsius, thereby obtaining a pattern with distinguishable changes in optical state.

9. The application of the hydrogel according to any one of claims 1-3 in photolithographic patterning, information encryption, information storage, or anti-counterfeiting.

10. The method as described in claim 9, characterized in that, The photo-induced pattern is a dynamically changing pattern.

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