A brain-like photoluminescent composite hydrogel, a preparation method and applications thereof

Abstract

The application provides a brain-like piezoluminescence composite hydrogel, a preparation method and application, and comprises a multiple crosslinking hydrogel matrix composed of a polyacrylamide covalent network, a sodium alginate ion crosslinking network and a pectin regulation network, and a piezoluminescence functional phase uniformly dispersed in the multiple crosslinking hydrogel matrix; the piezoluminescence functional phase comprises BaSi2O2N2:Eu 2+ particles modified by a silane coupling agent, and polymethacrylate hydrophobic microzones outside the surface-modified BaSi2O2N2:Eu 2+ particles; the composite hydrogel generates a collectable light signal under the action of a piezoluminescence load and has super-soft viscoelastic mechanical characteristics matched with brain tissue; the application successfully embeds a piezoluminescence phase in a brain-like hydrogel by adopting a phase separation preparation and multiple crosslinking process. The method maintains the super-soft viscoelastic characteristics of the material, overcomes the problem of serious dissipation of piezoluminescence in a super-soft network, and gives the material excellent piezoluminescence load response capability.

Description

Technical Field

[0001] This invention relates to the fields of biomedical biomimetic materials, flexible smart materials, mechanoluminescent materials and mechanical sensing technology, and particularly to a brain-like mechanoluminescent composite hydrogel, its preparation method and application. Background Technology

[0002] In the study of blast-induced traumatic brain injury (BTBI), developing highly realistic brain tissue substitutes is fundamental to revealing the injury mechanism caused by stress waves. Real human brain tissue has extremely high bulk modulus, low shear modulus, and significant strain rate effects.

[0003] While existing technologies have produced brain-like hydrogels using a dual-network strategy that can effectively simulate the modulus and viscoelasticity of brain tissue, significant bottlenecks remain in visualizing the mechanical response. Traditional methods for acquiring internal stress in brain models primarily rely on implanted sensors. This measurement method is considered "invasive point monitoring," which not only disrupts the continuity of the material, causing stress concentration distortion, but also fails to obtain a full-field, continuous image of stress distribution and evolution.

[0004] Mechanoluminescent materials can generate light signals under mechanostimulation, providing new insights into the visualization of stress distribution and damage evolution. However, most existing mechanoluminescent hydrogels are based on high-modulus matrices. For ultrasoft hydrogels with modulus in the kPa range and high water content, achieving mechanoluminescence faces challenges such as quenching of luminescent particles by water molecules, dissipation of mechanoluminescent energy due to polymer chain slippage, and easy slippage and debonding at the particle-matrix interface. These problems prevent luminescent particles from emitting light efficiently in brain-like aqueous environments, thus hindering the development of brain-like mechanoluminescent materials.

[0005] Therefore, there is an urgent need in the field to develop a novel composite hydrogel system that can maintain the ultrasoft viscoelastic mechanical characteristics required for brain tissue substitute materials, while overcoming the physical bottleneck of luminescence in ultrasoft matrices, and achieving force-induced luminescence, stable luminescence in an aqueous environment, and quantitative calibration of stress-light intensity. This system can then be used for visualization studies of the propagation, convergence, stress concentration, and damage evolution of explosive shock waves in brain-like media. Summary of the Invention

[0006] To address the problems existing in the background technology, the present invention provides a brain-like mechanoluminescent composite hydrogel, its preparation method, and its application. The present invention introduces surface-modified inorganic mechanoluminescent particles into a multi-crosslinked hydrogel matrix with brain-like ultra-soft viscoelastic characteristics, and utilizes a hydrophobic micro-region encapsulation mechanism to improve the luminescence stability and stress transmission efficiency of the mechanoluminescent particles in a water-containing environment, thereby achieving non-contact optical characterization of stress concentration, wave propagation, and damage evolution processes under impact loads.

[0007] The specific details of the invention are as follows: In a first aspect, the present invention provides a brain-like mechanoluminescent composite hydrogel, comprising a multi-crosslinked hydrogel matrix composed of a polyacrylamide covalent network, a sodium alginate ion crosslinking network and a pectin regulatory network, and a mechanoluminescent functional phase uniformly dispersed in the multi-crosslinked hydrogel matrix. The mechanoluminescent functional phase includes BaSi2O2N2:Eu, which has been surface-modified with a silane coupling agent. 2+ Mechanoluminescent particles, and in-situ polymerized coatings of BaSi2O2N2:Eu on the surface. 2+ Hydrophobic microdomains of polymethyl methacrylate on the exterior of mechanoluminescent particles; The composite hydrogel generates collectable optical signals under force-induced loading and possesses ultra-soft viscoelastic mechanical characteristics that match those of brain tissue.

[0008] Optionally, in the composite hydrogel, the mechanoluminescent functional phase accounts for 3% to 10% by mass, the polyacrylamide covalent network accounts for 0.3 wt% to 6 wt%, the sodium alginate ion crosslinking network accounts for 0.08 wt% to 1.5 wt%, the pectin regulating network accounts for 1.2 wt% to 6 wt%, and the water content is not less than 85 wt%.

[0009] Optionally, the static elastic modulus of the composite hydrogel is 1.5 kPa to 3.0 kPa, and the dynamic modulus at high strain rates is 300 kPa to 900 kPa.

[0010] In a second aspect, the present invention provides a method for preparing the neuromorphic luminescent composite hydrogel described in the first aspect above, the method comprising: Using silane coupling agents to catalyze inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ After surface modification, the resulting modified particulate material is mixed with methyl methacrylate and a photoinitiator, and then added to an aqueous solution containing a surfactant for high-speed emulsification to form a mixed system. Sodium alginate and acrylamide were dissolved in deionized water to form sol A; pectin powder was dissolved in deionized water to obtain sol B. The sol A and sol B are mixed with the mixed system, and a chemical crosslinking agent, a thermal initiator ammonium persulfate and a CaCl2 solution are added. The mixture is stirred until homogeneous to form a composite precursor emulsion. The composite precursor emulsion was injected into a mold, and a copolymerization reaction was initiated by ultraviolet light to obtain a mechanoluminescent brain-like composite hydrogel.

[0011] Optionally, the amount of the silane coupling agent is inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+2% to 8% of the quality; The use of silane coupling agent for inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ Surface finishing includes: Inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ The modified granules were dispersed in an ethanol-water solution containing the silane coupling agent γ-MPS, and the pH of the system was adjusted to 4.5-5.5. The mixture was stirred continuously at 50-70 °C for 6-10 hours. After the reaction was completed, the modified granules were centrifuged, washed, and dried.

[0012] Optionally, in the mixed system, the mass ratio of the modified particulate material to methyl methacrylate is 1:0.6 to 1:1.5, and the mass percentage of the surfactant is 0.2% to 0.8%.

[0013] Optionally, in the sol A, the mass ratio of sodium alginate to acrylamide is 1:4 to 1:8, and the total mass percentage of sodium alginate and acrylamide is 3% to 12%. In the sol B, the pectin content is 3.0% to 8.0% by mass.

[0014] Optionally, in the composite precursor emulsion, the mass ratio of sol A to sol B is 1:1 to 1:2.5.

[0015] Optionally, in the composite precursor emulsion, the concentration of CaCl2 solution is 0.05 mol / L to 0.15 mol / L, the mass ratio of chemical crosslinking agent to acrylamide is 0.04% to 0.15%, and the mass ratio of thermal initiator to acrylamide is 0.005% to 0.0120%.

[0016] Thirdly, the present invention provides an application of the brain-like mechanoluminescent composite hydrogel described in the first aspect above, using the brain-like mechanoluminescent composite hydrogel as a brain-like material for research on the injury mechanism of craniocerebral blast injury, visualization of shock stress wave propagation, identification of stress concentration areas, optical monitoring of damage evolution, construction of highly realistic physical head models, or evaluation of the effectiveness of protective equipment.

[0017] Compared with the prior art, the present invention has the following advantages: (1) This invention employs a phase separation preparation and multiple cross-linking process to successfully embed the mechanoluminescent phase into a brain-like hydrogel. This method overcomes the problem of severe dissipation of mechanoluminescence energy in ultra-soft networks while maintaining the ultra-soft viscoelastic properties of the material, thus endowing it with excellent mechanoluminescence response capability.

[0018] (2) The present invention constructs hydrophobic microregions in a high water content environment through particle surface modification and in-situ emulsification and coating of hydrophobic monomers, thereby improving the dispersion stability, stress transfer efficiency and resistance to luminescence decay of mechanoluminescent particles in high water content hydrogels.

[0019] (3) The present invention can convert the mechanoluminescence response induced by stress concentration areas inside or on the surface of the material into a collectable light intensity distribution, which can be used to characterize the propagation, convergence and damage evolution of impact stress waves, thus avoiding the damage to the continuity of materials caused by traditional implantable point sensors.

[0020] (4) The present invention can establish stress-light intensity, strain-light intensity or strain energy density-light intensity relationship by pre-calibration, so as to provide a stable and quantitative material basis for the full-field dynamic mechanical response analysis in craniocerebral blast injury experiments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the preparation method of the mechanoluminescent composite hydrogel with brain-like mechanical characteristics provided in an embodiment of the present invention is shown. Figure 2 The image shown is a physical image of a mechanoluminescent composite hydrogel with brain-like mechanical features provided in an embodiment of the present invention. Figure 3 A comparison diagram of the quasi-static and dynamic compressive real stress-real strain curves of the composite hydrogel provided in Embodiment 1 of the present invention is shown. Figure 4 A comparison diagram of the quasi-static and dynamic compressive real stress-real strain curves of the composite hydrogel provided in Embodiment 2 of the present invention is shown. Figure 5 The quasi-static tensile luminescence intensity-true strain curve of the composite hydrogel provided in Embodiment 1 of the present invention is shown. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by anyone under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0024] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0025] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] In a first aspect, the present invention provides a brain-like mechanoluminescent composite hydrogel, comprising a multi-crosslinked hydrogel matrix composed of a polyacrylamide covalent network, a sodium alginate ion crosslinking network and a pectin regulatory network, and a mechanoluminescent functional phase uniformly dispersed in the multi-crosslinked hydrogel matrix. The mechanoluminescent functional phase includes BaSi2O2N2:Eu, which has been surface-modified with a silane coupling agent. 2+ Mechanoluminescent particles, and in-situ polymerized coatings of BaSi2O2N2:Eu on the surface. 2+ Hydrophobic microdomains of polymethyl methacrylate on the exterior of mechanoluminescent particles; The composite hydrogel generates collectable optical signals under force-induced loading and possesses ultra-soft viscoelastic mechanical characteristics that match those of brain tissue.

[0028] In practical implementation, the multi-crosslinked hydrogel matrix is ​​a brain-like ultrasoft framework constructed by three layers of networks, including a polyacrylamide covalent network, a sodium alginate ion crosslinking network, and a pectin regulatory network. Among them, the polyacrylamide covalent network is a continuous flexible main framework that relies on carbon-carbon covalent bonds to form a permanent crosslinked structure, providing the gel's basic molding ability and large deformation extensibility. The sodium alginate polysaccharide molecular chains in the sodium alginate ion crosslinking network can form dynamic and reversible ionic bonds with calcium ions, giving the material viscoelasticity and stress relaxation characteristics unique to the human brain. The pectin polymer chains in the pectin regulatory network are interspersed in the gaps between the first two network layers in the form of physical entanglement, specifically regulating the material's strain rate hardening response and achieving differentiated modulus changes under high and low loading rates.

[0029] In specific implementation, the mechanoluminescent functional phase is a three-layer coated composite particle structure, with its core being rare-earth-doped silicon nitride oxide inorganic mechanoluminescent particles BaSi2O2N2:Eu. 2+ (BSON); the middle modified layer is a silane coupling agent grafted onto the surface of BSON particles, which introduces carbon-carbon double bonds to build a chemical connection bridge between the BSON particles and the hydrophobic micro-regions of the organic matrix; the outer layer is a nanoscale hydrophobic shell formed by in-situ polymerization of polymethyl methacrylate hydrophobic micro-regions, which completely encapsulates the modified luminescent particles.

[0030] Traditional single-network hydrogels can only match a single static modulus, lack strain hardening, and exhibit significant deviations in explosive impact mechanical response from real brain tissue, leading to simulation failure. Dual-hydrogel networks (such as PAM + sodium alginate) experience substantial polymer chain slippage under stress, with most mechanical energy dissipated as heat, resulting in minimal energy absorption and weak luminescence by the luminescent particles. This embodiment incorporates pectin's entanglement effect, limiting excessive molecular chain slippage and transferring more mechanical energy to the BSON luminescent core, addressing the industry pain point of water molecule quenching and low luminescence efficiency in high-water-content ultrasoft hydrogels. Furthermore, the poor compatibility between synthetic polyacrylamide and natural sodium alginate polysaccharide, coupled with pectin as an intermediate phase filler, ensures completely uniform mechanical and luminescence distribution across the entire matrix. This guarantees that the composite hydrogel can generate visible light signals that can be captured by spectrometers and high-speed cameras under force-induced loads (such as compression, tension, shear, and impact), exhibiting ultrasoft viscoelastic mechanical characteristics highly similar to human brain tissue.

[0031] In some embodiments, the composite hydrogel contains the following components: the mechanoluminescent functional phase accounts for 3% to 10% by mass; the polyacrylamide covalent network accounts for 0.3 wt% to 6 wt%; the sodium alginate ion crosslinking network accounts for 0.08 wt% to 1.5 wt%; the pectin regulating network accounts for 1.2 wt% to 6 wt%; and the water content is not less than 85 wt%.

[0032] In specific implementation, the total mass proportion of the mechanoluminescent functional phase in the composite hydrogel is controlled at 3%–10% to ensure that the static elastic modulus of the composite hydrogel is within the ultra-low static modulus range of 1.5 kPa to 3.0 kPa, similar to that of brain tissue. This also ensures that the light intensity generated by the mechanoluminescent functional phase under compression, impact, and other loads can be stably acquired by a spectrometer and high-speed camera, allowing for quantitative calibration of stress and light intensity. The 3%–10% range maintains the ultra-soft biomimetic properties of the matrix while ensuring effective luminescence response. The polyacrylamide covalent network, as the continuous framework of the triple cross-linked matrix, has a mass proportion limited to 0.3 wt%–6 wt%. Excessive polyacrylamide content significantly increases gel hardness, deviating from the soft, kPa-level characteristics of the human brain. Within this range, a low proportion is suitable for preparing soft gray matter, while a high proportion can be combined with pectin to enhance the dynamic impact modulus, simulating the more rigid white matter of the corpus callosum. The sodium alginate ion-crosslinking network, accounting for 0.08%, is the core component providing reversible ion crosslinking and imparting the unique viscoelasticity of brain tissue to the material. By adjusting the amount of sodium alginate added, the stress relaxation rate of the gel can be precisely controlled within the range of wt% to 1.5 wt%, matching the viscosity differences of different brain tissues. The pectin regulatory network achieves strain rate hardening regulation through molecular entanglement, while reducing mechanical energy dissipation during the stress process and improving luminescence efficiency. The pectin content ranges from 1.2 wt% to 6 wt%. When the pectin content is insufficient, the polymer chains slide disorderly under high-speed impact, and most of the mechanical energy is lost as heat energy. The excitation intensity of the luminescent particles is greatly reduced, and the strain rate hardening behavior of the brain tissue, which is "statically soft and dynamically hard," cannot be reproduced. Excessive pectin will lead to the viscosity of the precursor, difficulty in defoaming, and increased brittleness of the finished product. Increasing the pectin ratio within the range can raise the dynamic modulus of the gel to 900 kPa, which is suitable for white matter. Reducing the amount of pectin matches the dynamic modulus range of 300 kPa for gray matter. In addition, based on the superior shrinkage properties of multi-crosslinked hydrogels, the water content of this composite hydrogel is higher than 85%. This index is comparable to the original high water content physiological characteristics of human brain tissue. Sufficient water can not only restore the real cranial mechanical environment, but also work with the hydrophobic micro-regions on the outer layer of luminescent particles to alleviate the quenching effect of water molecules on the luminescence center, thus balancing biomimicry and long-term luminescence stability.

[0033] In some embodiments, the composite hydrogel has a static elastic modulus of 1.5 kPa to 3.0 kPa and a dynamic modulus of 300 kPa to 900 kPa under high strain rates. The composite hydrogel's true stress-strain response under quasi-static loading and high strain rate loading conditions matches the target brain tissue. Specifically, a static modulus of around 1.5 kPa and a dynamic modulus of around 300 kPa are suitable for simulating gray matter; a static modulus of around 3 kPa and a dynamic modulus of around 900 kPa are suitable for simulating white matter of the corpus callosum. Gray matter and the corpus callosum are the parts of brain tissue with the lowest and highest moduli, respectively. By adjusting the material ratio, the composite hydrogel's modulus can be positioned between these two values, thus simulating the mechanical properties of other parts of the brain tissue.

[0034] Secondly, the present invention provides a method for preparing the neuromorphic mechanoluminescent composite hydrogel described in the first aspect above. Figure 1 A flowchart illustrating the preparation method of the neuromorphic mechanoluminescent composite hydrogel provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes: S1. Using silane coupling agents to precipitate inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ After surface modification, the resulting modified particulate material is mixed with methyl methacrylate and a photoinitiator, and then added to an aqueous solution containing a surfactant for high-speed emulsification to form a mixed system. S2. Dissolve sodium alginate and acrylamide in deionized water to form sol A; dissolve pectin powder in deionized water to obtain sol B; S3. Mix the sol A and sol B with the mixed system, and add the chemical crosslinking agent, the thermal initiator ammonium persulfate and CaCl2 solution, and stir evenly to form a composite precursor emulsion; S4. The composite precursor emulsion is injected into a mold, and a copolymerization reaction is initiated by ultraviolet light to obtain a mechanoluminescent brain-like composite hydrogel.

[0035] In practical implementation, inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ The surface of (BSON) contains a large number of polar hydroxyl groups, resulting in strong electrostatic attraction between particles. Direct mixing into an aqueous sol makes it prone to agglomeration and sedimentation, necessitating hydrophobic modification. This embodiment utilizes a silane coupling agent to first modify the BSON surface. The process includes: adding inorganic mechanoluminescent particles BaSi2O2N2:Eu... 2+The granules were dispersed in an ethanol-water solution containing the silane coupling agent 3-methacryloyloxypropyltrimethoxysilane (γ-MPS). The pH of the system was adjusted to 4.5–5.5, and the mixture was continuously stirred at 50–70 °C for 6–10 hours. After the reaction, the modified granules were centrifuged, washed, and dried. The amount of silane coupling agent used was [missing information - likely a specific concentration] of inorganic mechanoluminescent particles BaSi₂O₂N₂:Eu². + The mass is 2%–8%; during this process, after the silane coupling agent is hydrolyzed in a weakly acidic ethanol system with a pH of 4.5–5.5, the siloxane end undergoes dehydration condensation with the hydroxyl groups on the surface of BSON particles to form stable Si-O inorganic covalent bonds. Organic molecular chains with unsaturated double bonds of methacrylic acid are then firmly grafted onto the particle surface. This establishes a chemical connection bridge between the BSON inorganic particles and the organic phase. Subsequently, methyl methacrylate in the emulsification stage and acrylamide monomer in the molding stage can undergo UV free radical copolymerization with these double bonds, forming an integrated covalently bonded structure of the BSON core, hydrophobic microdomains of polymethacrylate, and polyacrylamide gel matrix, thus eliminating the effects of external impact and compression. The action of the silane modification layer reduces the interfacial slippage and debonding phenomenon between the particles, the coating layer, and the hydrogel skeleton, minimizing the unnecessary dissipation of mechanical energy at the interface. This allows more load stress to be effectively transferred to the BSON luminescent lattice, significantly improving the luminescence intensity under the same strain. On the other hand, the organic hydrophobic carbon chains grafted onto the particle surface weaken the strong polarity of the inorganic powder, greatly improving the dispersion ability of BSON in aqueous emulsions containing surfactants and mixed sols of sodium alginate and acrylamide. This prevents local particle agglomeration and ensures a uniform distribution of the luminescent phase inside the final composite hydrogel, achieving full-field visualization imaging of impact stress without bright or dark patches. Simultaneously, the silane modification layer acts as an inner hydrophobic barrier, forming a double-layer water-resistant structure with the subsequent in-situ polymerized outer hydrophobic microregions of polymethyl methacrylate, preventing water molecules in the high-water-content matrix from directly contacting the Eu inside the particles. 2+Rare-earth luminescent centers suppress the quenching effect of water molecule-induced nonradiative transitions, allowing the brain-like gel with a water content ≥ 85% to maintain a stable and detectable light signal even under long-term immersion in physiological saline. Furthermore, silane modification imparts organic compatibility to the particle surface, eliminating interference from bare inorganic particles on sodium alginate ion crosslinking and pectin molecule physical entanglement. No flocculation or stratification issues occur after precursor mixing, and the triple crosslinking structure of the polyacrylamide covalent network, sodium alginate ion crosslinking network, and pectin regulatory network is fully preserved after molding. This ensures that the mechanical properties of the composite hydrogel are matched with those of brain tissue (static elastic modulus of 1.5 kPa to 3.0 kPa, and dynamic modulus of 300 kPa to 900 kPa under high strain rate) without shifting due to the filling of luminescent particles. It simultaneously meets the two core requirements of precise mechanical biomimicry and high-sensitivity force-induced optical sensing. If this surface modification step is omitted, the finished gel will have multiple defects such as particle sedimentation, weak luminescence, rapid attenuation of light intensity after stress, and local mechanical property imbalance, making it impossible to achieve quantitative visualization of the cranial impact stress field.

[0036] It should be noted that this embodiment does not specify the photoinitiator used; any water-soluble free radical photoinitiator that meets the requirements of ultraviolet light source is acceptable, such as 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959) used in this embodiment. This embodiment also does not specify the chemical crosslinking agent used; any conventional crosslinking agent that can cooperate with the photoinitiator to achieve ultraviolet free radical polymerization is acceptable, such as N,N'-methylenebisacrylamide used in this embodiment.

[0037] In some embodiments, the mass ratio of the modified particulate material to methyl methacrylate in the mixed system is 1:0.6 to 1:1.5, and the mass percentage of the surfactant is 0.2% to 0.8%.

[0038] In some embodiments, the mass ratio of sodium alginate to acrylamide in sol A is 1:4 to 1:8, and the total mass percentage of sodium alginate and acrylamide is 3% to 12%. In the sol B, the pectin content is 3.0% to 8.0% by mass.

[0039] In some embodiments, the mass ratio of sol A to sol B in the composite precursor emulsion is 1:1 to 1:2.5.

[0040] In some embodiments, the concentration of CaCl2 solution in the composite precursor emulsion is 0.05 mol / L to 0.15 mol / L, the mass ratio of chemical crosslinking agent to acrylamide is 0.04% to 0.15%, and the mass ratio of thermal initiator to acrylamide is 0.005% to 0.0120%.

[0041] Thirdly, the present invention provides an application of the brain-like mechanoluminescent composite hydrogel described in the first aspect above, using the brain-like mechanoluminescent composite hydrogel as a brain-like material for research on the injury mechanism of craniocerebral blast injury, visualization of shock stress wave propagation, identification of stress concentration areas, optical monitoring of damage evolution, construction of highly realistic physical head models, or evaluation of the effectiveness of protective equipment.

[0042] To enable those skilled in the art to better understand the present invention, the following embodiments are provided to illustrate in detail the neuromorphic luminescent composite hydrogel, its preparation method, and its application.

[0043] Example 1: Mechanoluminescent composite hydrogel mimicking brain gray matter This embodiment provides a mechanoluminescent composite hydrogel that matches the mechanical characteristics of real brain gray matter and possesses highly sensitive stress sensing capabilities. The static elastic modulus of brain gray matter is approximately 1.5 kPa, and the dynamic impact modulus is approximately 300 kPa. The raw material components and their masses for preparing this gel are as follows: Inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ (BSON) 0.8 g, silane coupling agent γ-MPS 0.04 g, methyl methacrylate (MA) 0.8 g, photoinitiator I2959 0.008 g, surfactant Tween 80 0.4 g, sodium alginate 0.8 g, acrylamide 4.8 g, pectin 4.5 g, chemical crosslinking agent N,N'-methylenebisacrylamide 0.004 g, thermal initiator ammonium persulfate 0.001 g, 0.1 mol / L CaCl2 solution 1.5 mL, deionized water 180 mL.

[0044] The specific preparation steps are as follows: BSON particle surface modification: 0.8 g BSON was dispersed in an ethanol-water aqueous solution with a volume ratio of 95:5, 0.04 g γ-MPS was added, and the pH of the system was adjusted to 5.0 using glacial acetic acid. The reaction was continuously stirred at 60 °C for 8 h. After the reaction was completed, the particles were centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C to obtain surface-modified BSON particles—M-BSON.

[0045] Preparation of the hydrophobic functional phase: The M-BSON particles obtained above were thoroughly mixed with 0.8 g of methyl methacrylate (MA) and 0.008 g of I2959, and then slowly added dropwise to 20 mL of deionized water containing 0.4 g of Tween 80. Emulsification was then performed using a high-speed shear emulsifier at 10,000 rpm for 20 min to form a mixed system in which M-BSON was tightly coated with the hydrophobic monomer MA.

[0046] Sol preparation: 0.8g sodium alginate and 4.8g acrylamide were completely dissolved in 80mL of deionized water and stirred at high speed at room temperature to obtain sol A; 4.5g pectin powder was added to 100mL of deionized water at 90℃ and stirred at high speed at constant temperature for 30min until completely dissolved to obtain sol B.

[0047] Mixing and Molding: The above-mentioned mixture, sol A, and sol B were thoroughly mixed according to the mass ratio. Then, 1.5 mL of CaCl2 solution, 0.004 g of MBAA, and 0.001 g of APS were added sequentially. After the mixture was stirred at high speed and thoroughly degassed using a vacuum degassing machine, it was poured into a pre-cooled mold and irradiated under 365 nm ultraviolet light for 40 min to initiate a copolymerization reaction. After demolding, a mechanoluminescent gray composite hydrogel specimen was obtained. See the actual image below. Figure 2 .

[0048] Example 2: Mechanoluminescent composite hydrogel simulating the corpus callosum This embodiment provides a mechanoluminescent composite hydrogel that matches the mechanical characteristics of the human corpus callosum and possesses highly sensitive stress sensing capabilities. The static elastic modulus of the corpus callosum is approximately 3 kPa, and the dynamic impact modulus is approximately 900 kPa. The raw material components and their masses for preparing this gel are as follows: Inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ 1.2 g of (BSON), 0.08 g of silane coupling agent γ-MPS, 1 g of methyl methacrylate (MA), 0.012 g of photoinitiator I2959, 0.5 g of surfactant Tween 80, 1.5 g of sodium alginate, 7.5 g of acrylamide, 6.5 g of pectin, 0.008 g of chemical crosslinking agent N,N'-methylenebisacrylamide, 0.001 g of thermal initiator ammonium persulfate, 2 mL of 0.1 mol / L CaCl2 solution, and 175 mL of deionized water.

[0049] The specific preparation steps are as follows: Surface modification of BSON particles: 1.2 g of BSON was dispersed in an ethanol-water aqueous solution with a volume ratio of 95:5, 0.08 g of γ-MPS was added, and the pH of the system was adjusted to 5.0 using glacial acetic acid. The reaction was carried out by continuous stirring at 60 °C for 8 h. After the reaction was completed, the particles were centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C to obtain surface-modified BSON particles—M-BSON.

[0050] Preparation of the hydrophobic functional phase: The M-BSON particles obtained above were thoroughly mixed with 1 g of methyl methacrylate and 0.012 g of I2959, and then slowly added dropwise to 20 mL of deionized water containing 0.5 g of Tween 80. The mixture was then emulsified at 10,000 rpm for 20 min using a high-speed shear emulsifier to form a mixed system in which M-BSON was tightly coated with the hydrophobic monomer MA.

[0051] Sol preparation: 1.5 g sodium alginate and 7.5 g acrylamide were completely dissolved in 75 mL deionized water and stirred at high speed at room temperature to obtain sol A; 6.5 g pectin powder was added to 100 mL of deionized water at 90 ℃ and stirred at high speed at constant temperature for 30 min until completely dissolved to obtain sol B.

[0052] Mixing and Molding: The above-mentioned mixture, sol A, and sol B were completely mixed according to the mass ratio. Then, 2 mL of CaCl2 solution, 0.008 g of MBAA, and 0.001 g of APS were added sequentially. After the mixture was stirred at high speed and thoroughly degassed using a vacuum degassing machine, it was poured into a pre-cooled mold and irradiated under 365 nm ultraviolet light for 40 min to initiate a copolymerization reaction. After demolding, mechanoluminescent corpus callosum-like composite hydrogel specimens were obtained.

[0053] Performance testing: Mechanical property testing: (1) Quasi-static compression: Instron 5943 testing machine, 10N sensor, cylindrical specimen (15mm diameter × 10mm height), strain rate 0.01s -1 The strain was increased to 40% compressive strain, and the actual stress-strain curve and initial modulus were recorded.

[0054] (2) Dynamic impact: Split Hopkinson bar (SHPB), bullet velocity 4-12 m / s, strain rate 1000-4000 s. -1 Because the specimen impedance is extremely low, a PMMA transmission rod was used and impedance matching correction was performed.

[0055] Figure 3 The diagram shows a comparison of the quasi-static and dynamic compressive true stress-true strain curves of the composite hydrogel provided in Embodiment 1 of the present invention, as follows: Figure 3 As shown, under quasi-static compression conditions (strain rate 0.01 s⁻¹), -1 The true stress-strain curve of the composite hydrogel exhibits a typical "J"-shaped characteristic of ultrasoft materials, with an initial modulus of approximately 1.5 kPa, which highly matches the static elastic modulus of real brain gray matter; under high strain rate dynamic impact conditions (strain rate 1000~4000 s⁻¹), the hydrogel also shows a high degree of stability. -1The dynamic compressive modulus of the material was significantly increased to approximately 300 kPa, exhibiting a clear strain rate enhancement effect, consistent with the mechanical response characteristics of brain tissue under impact load. The significant difference between the quasi-static and dynamic curves indicates that the composite hydrogel successfully reproduced the strain rate sensitivity of brain tissue. Testing showed that the composite hydrogel provided in Example 1 had a water content of approximately 85%, a static compressive modulus of 1.5 kPa, and a dynamic compressive modulus of 300 kPa. These mechanical properties correspond to the test results of quasi-static compression and dynamic impact in the testing method, confirming that the composite hydrogel prepared in Example 1 highly matches the modulus level of brain gray matter.

[0056] Figure 4 The diagram shows a comparison of the quasi-static and dynamic compressive true stress-true strain curves of the composite hydrogel provided in Embodiment 2 of the present invention; as shown. Figure 4 As shown, under quasi-static compression conditions, the initial modulus of the composite hydrogel is approximately 3.0 kPa, matching the static elastic characteristics of the corpus callosum white matter; under dynamic impact conditions, the dynamic compression modulus increases to approximately 900 kPa. Compared to Example 1, the quasi-static and dynamic moduli of Example 2 are significantly improved, indicating that by adjusting the proportion of gel components, the mechanical properties of the composite hydrogel can be flexibly adjusted within the range of 1.5–3.0 kPa (static) and 300–900 kPa (dynamic), achieving accurate simulation of the mechanical characteristics of different brain regions. Tests showed that Example 2 had a water content of approximately 85%, a static compression modulus of 3 kPa, and a dynamic compression modulus of 900 kPa. These mechanical property indicators correspond to the test results of quasi-static compression and dynamic impact in the test methods, confirming that the composite hydrogel prepared in Example 2 highly matches the modulus level of the corpus callosum white matter.

[0057] Optical performance testing: (1) Force-optical coupling calibration: The specimen was placed on the testing machine, and a fiber optic spectrometer (Ocean OpticsQE Pro) was arranged at a 45° angle to the side, with a sampling rate ≥100Hz and a strain rate of 0.01 s. -1 Compress to 30% and establish normalized light intensity-stress / strain / strain energy density calibration curves.

[0058] The force-light coupling calibration results show that, within the range of 0-30% compressive strain, the normalized light intensity of the composite hydrogel in Example 1 exhibits a good monotonically positive correlation with stress / strain / strain energy density, and the correlation coefficient R2 of the linear fitting of light intensity and stress is greater than 0.98, laying a calibration foundation for quantitative force-light characterization.

[0059] (2) Dynamic impact visualization: a drop hammer (1.5kg, drop height 20-60cm), a high-speed camera (PhantomV2512, 50000fps, 512×384 pixels) was used to record transient luminescence images and extract the location, area and peak light intensity evolution of the stress concentration area.

[0060] In the dynamic impact visualization experiment of Examples 1 and 2, the composite hydrogels produced a clearly visible transient luminescence signal under the impact of the falling hammer. The high-speed camera successfully captured the propagation path of the stress wave and the luminescence distribution in the stress concentration area. The position and area of ​​the luminescence area were highly consistent with the impact contact area. The peak light intensity increased with the increase of impact energy, which verified the feasibility of the composite hydrogel of the present invention in the full-field visualization of the impact stress field.

[0061] (3) Aquatic environment stability: The specimens were immersed in physiological saline at 37℃ and taken out for testing at 1, 3, 7 and 14 days respectively, and the decay of luminescence intensity was recorded.

[0062] The stability tests of the composite hydrogels in the aqueous environment in Examples 1 and 2 showed that after being immersed in physiological saline at 37°C for 14 days, the mechanoluminescence intensity retention rate of the composite hydrogels was greater than 80%, indicating that the double-layer water-proof structure formed by the hydrophobic microdomains of polymethacrylate and the silane-modified layer effectively inhibited the influence of water molecules on Eu. 2+ The quenching effect of the luminescent center ensures the long-term stability of mechanoluminescence in a water-containing environment.

[0063] (4) Cyclic repeatability: 20% strain amplitude, 0.5Hz frequency, 50 cycles of loading and unloading, record the peak light intensity retention rate.

[0064] The cyclic repeatability test of the composite hydrogels in Examples 1 and 2 showed that after 50 cycles of loading and unloading under the conditions of 20% strain amplitude and 0.5 Hz frequency, the peak light intensity retention rate of the composite hydrogels was greater than 90%, demonstrating excellent fatigue resistance, luminescence stability and reusability.

[0065] Figure 5 The quasi-static tensile luminescence intensity-true strain curve of the composite hydrogel provided in Embodiment 1 of the present invention is shown; as follows: Figure 5 As shown, the normalized luminescence intensity of the composite hydrogel exhibits a monotonically increasing trend with increasing tensile strain. The increase in luminescence intensity is relatively gradual in the low strain region (0–10%), but rises significantly in the medium to high strain region (10%–30%), indicating that the stress transfer efficiency of the mechanoluminescent particles is improved under larger deformation, resulting in enhanced luminescence response sensitivity. This monotonic correspondence provides an experimental basis for the quantitative inversion of mechanical parameters through optical signals, confirming that the composite hydrogel of this invention possesses reliable force-optical coupling response characteristics.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," 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, the 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. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0067] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0068] The foregoing provides a detailed description of the neuromorphic luminescent composite hydrogel, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only intended to help understand the methods and core ideas of the present invention. At the same time, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A neuromorphic mechanoluminescent composite hydrogel, characterized in that, It includes a multi-crosslinked hydrogel matrix composed of a polyacrylamide covalent network, a sodium alginate ion crosslinking network and a pectin regulatory network, and a mechanoluminescent functional phase uniformly dispersed in the multi-crosslinked hydrogel matrix; The mechanoluminescent functional phase includes BaSi2O2N2:Eu, which has been surface-modified with a silane coupling agent. 2+ Mechanoluminescent particles, and in-situ polymerized coatings of BaSi2O2N2:Eu on the surface. 2+ Hydrophobic microdomains of polymethyl methacrylate on the exterior of mechanoluminescent particles; The composite hydrogel generates collectable optical signals under force-induced loading and possesses ultra-soft viscoelastic mechanical characteristics that match those of brain tissue.

2. The neuromorphic mechanoluminescent composite hydrogel according to claim 1, characterized in that, In the composite hydrogel, the mechanoluminescent functional phase accounts for 3% to 10% by mass, the polyacrylamide covalent network accounts for 0.3 wt% to 6 wt%, the sodium alginate ion crosslinking network accounts for 0.08 wt% to 1.5 wt%, the pectin regulating network accounts for 1.2 wt% to 6 wt%, and the water content is not less than 85 wt%.

3. The neuromorphic mechanoluminescent composite hydrogel according to claim 1, characterized in that, The composite hydrogel has a static elastic modulus of 1.5 kPa to 3.0 kPa and a dynamic modulus of 300 kPa to 900 kPa at high strain rates.

4. A method for preparing the neuromorphic mechanoluminescent composite hydrogel according to any one of claims 1-3, characterized in that, The preparation method includes: Using silane coupling agents to catalyze inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ After surface modification, the resulting modified particulate material is mixed with methyl methacrylate and a photoinitiator, and then added to an aqueous solution containing a surfactant for high-speed emulsification to form a mixed system. Sodium alginate and acrylamide were dissolved in deionized water to form sol A; pectin powder was dissolved in deionized water to obtain sol B. The sol A and sol B are mixed with the mixed system, and a chemical crosslinking agent, a thermal initiator ammonium persulfate and a CaCl2 solution are added. The mixture is stirred until homogeneous to form a composite precursor emulsion. The composite precursor emulsion was injected into a mold, and a copolymerization reaction was initiated by ultraviolet light to obtain a mechanoluminescent brain-like composite hydrogel.

5. The method for preparing the neuromorphic mechanoluminescent composite hydrogel according to claim 4, characterized in that, The amount of the silane coupling agent is the inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ 2% to 8% of the quality; The use of silane coupling agent for inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ Surface hydrophobic modification includes: Inorganic mechanoluminescent particles BaSi2O2N2:Eu 2+ The modified granules were dispersed in an ethanol-water solution containing the silane coupling agent γ-MPS, and the pH of the system was adjusted to 4.5-5.

5. The mixture was stirred continuously at 50-70 °C for 6-10 hours. After the reaction was completed, the modified granules were centrifuged, washed, and dried.

6. The method for preparing the neuromorphic mechanoluminescent composite hydrogel according to claim 4, characterized in that, In the mixture, the mass ratio of the modified particulate material to methyl methacrylate is 1:0.6 to 1:1.5, and the mass percentage of the surfactant is 0.2% to 0.8%.

7. The method for preparing the neuromorphic mechanoluminescent composite hydrogel according to claim 4, characterized in that, In the sol A, the mass ratio of sodium alginate to acrylamide is 1:4 to 1:8, and the total mass percentage of sodium alginate and acrylamide is 3% to 12%. In the sol B, the pectin content is 3.0% to 8.0% by mass.

8. The method for preparing the neuromorphic luminescent composite hydrogel according to claim 4, characterized in that, In the composite precursor emulsion, the mass ratio of sol A to sol B is 1:1 to 1:2.

5.

9. The method for preparing the neuromorphic mechanoluminescent composite hydrogel according to claim 4, characterized in that, In the composite precursor emulsion, the concentration of CaCl2 solution is 0.05 mol / L to 0.15 mol / L, the mass ratio of chemical crosslinking agent to acrylamide is 0.04% to 0.15%, and the mass ratio of thermal initiator to acrylamide is 0.005% to 0.0120%.

10. The application of the neuromorphic mechanoluminescent composite hydrogel according to any one of claims 1-3, characterized in that, The aforementioned brain-like mechanoluminescent composite hydrogel can be used as a brain-like material for studying the injury mechanism of craniocerebral blast injuries, visualizing the propagation of shock stress waves, identifying stress concentration areas, optically monitoring damage evolution, constructing highly realistic physical head models, or evaluating the effectiveness of protective equipment.

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