A fully bio-based composite material and a method for its preparation

Abstract

This invention discloses a fully bio-based composite material and its preparation method, comprising the following materials by mass percentage: 35-65% modified soybean oil epoxy resin, 20-45% dynamic crosslinking agent combination, 5-20% bio-based flexible segments, 5-25% photothermal conversion and reinforcing filler, and 0.5-3% photoinitiator; the dynamic crosslinking agent combination includes lipoic acid and phytic acid; the lipoic acid undergoes ring-opening polymerization to form a network rich in dynamic disulfide bonds, and the phytic acid provides hydrogen bond crosslinking points, constituting a dynamic covalent-non-covalent synergistic crosslinking network; in a system composed of 100% bio-based components, photothermal conversion, shape memory, self-healing, and 3D printing processability are successfully coupled, breaking the constraint of the single function of bio-based materials and providing a material basis for their entry into the field of high-end intelligent devices.

Description

Technical Field

[0001] This invention belongs to the field of bio-based polymer composite materials technology, specifically referring to a fully bio-based composite material and its preparation method. Background Technology

[0002] With the deepening of sustainable development strategies, the development of bio-based materials that can replace petroleum-based products has become a global consensus. However, existing bio-based composite materials still face the following prominent bottlenecks when moving towards high-end intelligent applications, making it difficult to meet the comprehensive requirements of next-generation flexible electronics, soft robots, and intelligent medical devices for integrated, intelligent, and environmentally friendly material properties: Insufficient Functional Specificity and Integration: Current research largely focuses on improving the single properties of bio-based materials, such as enhancing mechanical strength, imparting degradability, or simple shape memory effects. For example, composite materials based on polylactic acid (PLA) or vegetable oils, while possessing good renewability, typically lack active response (such as remote light or heat actuation) and adaptive (such as self-healing) capabilities. Integrating multiple intelligent properties such as photothermal conversion, shape memory, and self-healing into a fully bio-based system and achieving synergistic effects remains a critical technical challenge that urgently needs to be overcome.

[0003] The challenge of balancing dynamic and mechanical properties: To introduce self-healing or remodeling properties, it is often necessary to construct dynamic cross-linked networks (such as those based on Diels-Alder reactions or transesterification). However, these dynamic chemical bonds often lead to low modulus and significant creep at room temperature, failing to meet the stiffness and dimensional stability requirements of structural components. Conversely, traditional cross-linked networks that pursue high mechanical properties sacrifice the dynamic characteristics of the material. The core challenge lies in constructing a network structure with both excellent mechanical strength and high dynamic responsiveness within a fully bio-based system.

[0004] Manufacturing limitations and the disconnect between structure and function: Current molding methods for bio-based composite materials are mainly compression molding, casting, and injection molding, which are difficult to use to create complex three-dimensional structures. Although some studies have attempted to use bio-based materials for fused deposition modeling (FDM) 3D printing, the limitations of material rheology and functional singularity mean that printed parts are usually only geometric entities, unable to achieve integrated design and manufacturing of material-structure-function. For example, it is impossible to manufacture intelligent devices with compositional gradients, thereby possessing functional gradients (such as rigid support at one end and flexible actuation at the other), in a single molding process.

[0005] Application limitations: Existing technologies are mostly geared towards low-value-added areas such as packaging and disposable products, and their performance design does not fully consider the specific needs of high-end application scenarios. In cutting-edge fields such as soft robotics and implantable / wearable medical devices, materials not only need to be environmentally friendly, but also require precise remote actuation, damage self-sensing and repair, and the ability to manufacture customized complex structures. Currently, there is a lack of fully bio-based material solutions that can simultaneously meet these stringent requirements.

[0006] Therefore, developing a fully bio-based composite material and its preparation method that can integrate multiple intelligent properties, balance dynamic and mechanical properties, and adapt to advanced manufacturing processes is of great scientific significance and application value for promoting the penetration of bio-based materials into high-value-added and high-tech fields. Summary of the Invention

[0007] To address the needs and problems mentioned in the background above, the present invention provides a fully bio-based composite material and its preparation method, thereby at least partially solving the above problems.

[0008] According to the technical solution of the present invention, a fully bio-based composite material is provided, comprising the following materials by mass percentage: 35-65% modified soybean oil epoxy resin, 20-45% dynamic crosslinking agent combination, 5-20% bio-based flexible segments, 5-25% photothermal conversion and enhancing functional filler and 0.5-3% photoinitiator; The dynamic crosslinking agent combination includes lipoic acid and phytic acid; The lipoic acid ring-opening polymerization forms a network rich in dynamic disulfide bonds, and the phytic acid provides hydrogen bond crosslinking sites, constituting a dynamic covalent-non-covalent synergistic crosslinking network.

[0009] Preferably, the dynamic crosslinking agent combination includes 15-35% thioctic acid and 5-15% phytic acid, which account for 15-35% of the total mass of the composite material.

[0010] Preferably, the bio-based flexible segments are polycaprolactone diol or polylactic acid-hydroxyacetic acid copolymer with a number average molecular weight of 2000-10000; the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0011] Preferably, the photothermal conversion and enhancement functional filler comprises the following materials by mass percentage: It contains 50-80% alkali lignin nanoparticles and 20-50% cellulose nanocrystals.

[0012] On the other hand, the present invention also provides a method for preparing a fully bio-based composite material, comprising the following steps: S1 One-Pot Melt Prepolymerization: Modified soybean oil epoxy resin, dynamic crosslinking agent combination and bio-based flexible segments are reacted at 80-120℃ under inert gas protection for 1-4 hours to form a prepolymer; S2 Functional Filler Dispersion: The prepolymer is cooled, a photoinitiator is added, and then a photothermal conversion and reinforcing functional filler is added. The mixture is then ultrasonically dispersed to form a uniform composite slurry. S3 Photopolymerization Molding: The composite slurry is photopolymerized and 3D printed to obtain the structural component of the composite material.

[0013] Preferably, the photopolymerization molding is a photopolymerization gradient 3D printing molding, which includes the following steps: By using at least two composite slurries with different contents of photothermal conversion and reinforcing fillers, and by controlling the feed ratio of different slurries during the printing process through a program, structural parts with compositional and performance gradients can be constructed in a single printing process.

[0014] Preferably, the composite slurry prepared in S2 is subjected to a shear rate of 1 s at 25°C. -1 The viscosity under the given conditions is greater than 5000 mPa·s, at a shear rate of 100 s⁻¹. -1 The viscosity under the given conditions is less than 500 mPa·s; In S3, the ultraviolet light wavelength for photopolymerization 3D printing is 365-405nm, the single-layer exposure time is 2-15s, and the layer thickness is 25-100μm.

[0015] Thirdly, the present invention also provides a fully bio-based multifunctional composite material structural component, wherein the structural component has a compositional and functional gradient, and the filler content in different regions varies continuously or in a stepwise manner.

[0016] Fourthly, the present invention also provides an application of a fully bio-based multifunctional composite material in the preparation of photothermal driven soft robot actuators or self-healing flexible sensors.

[0017] Furthermore, by utilizing the photothermal-shape memory synergistic effect of the composite material, non-contact actuation of the actuator can be achieved under 808nm near-infrared light irradiation; Alternatively, the self-healing properties of the composite material at 60-80℃ can be utilized to restore the mechanical and electrical properties of the sensor after damage.

[0018] Beneficial effects: This invention successfully couples photothermal conversion, shape memory, self-healing, and 3D printing processability into a system composed of 100% bio-based components, breaking the shackles of the single function of bio-based materials and providing a material basis for their entry into the field of high-end intelligent devices. This invention achieves decoupling of rigid load-bearing and dynamic rearrangement at the molecular scale through the synergistic cross-linking network design of dynamic covalent bonds and multiple non-covalent bonds. The network provides high strength at room temperature by hydrogen bonds and some crystalline domains, and under thermal stimulation, dynamic covalent bonds dominate network reconstruction, thereby simultaneously obtaining excellent mechanical properties and efficient self-healing / remodeling capabilities. This invention deeply integrates material synthesis and composite with advanced photopolymerization 3D printing technology, and innovatively develops a multi-slurry gradient printing process. This process can realize integrated manufacturing of materials, structure and function, and directly produce complex intelligent structural parts with continuous gradient changes in composition and performance that cannot be achieved by traditional methods, greatly expanding design freedom and application potential. The material properties of this invention are designed directly to meet the needs of cutting-edge fields such as soft robotics, flexible electronics, and smart healthcare, providing these fields with the first all-bio-based material system solution that integrates green, intelligent, and customizable features, and has extremely high practical application value and market prospects. Detailed Implementation

[0019] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0020] It should be noted that the embodiments of the present invention provide the following technical solutions: 1. A fully bio-based multifunctional composite material, wherein the composite material is formed by reacting the following components in mass percentage to form a dynamic cross-linked network: Modified soybean oil epoxy resin: 35-65%, as the main resin matrix for photocuring reaction, with an epoxy value preferably of 0.35-0.55 mol / 100g.

[0021] Dynamic crosslinking agent composition: 20-45%. This composition consists of lipoic acid (LA) and phytic acid (PA), where LA accounts for 15-35% of the total prepolymer mass, and PA accounts for 5-15%. Lipoic acid forms a polylipoic acid network rich in dynamic disulfide bonds through ring-opening polymerization; phytic acid, as a bio-based polyphosphate, provides abundant non-covalent hydrogen bond crosslinking sites. The two work synergistically to construct a dynamic covalent-non-covalent synergistic crosslinking network.

[0022] Bio-based flexible segments: 5-20%, selected from polycaprolactone diol (PCL-diol) or polylactic-co-glycolic acid copolymer (PLGA) with a number average molecular weight (Mn) of 2000-10000. Used to adjust network toughness, degradation rate, and glass transition temperature (Tg).

[0023] Photothermal conversion and reinforcing filler: 5-25%. Includes: Alkali lignin nanoparticles: accounting for 50-80% of the total filler mass, with an average particle size of 50-200nm. As a highly efficient near-infrared photothermal conversion agent, its photothermal conversion efficiency under 808nm wavelength laser is not less than 20%.

[0024] Cellulose nanocrystals (CNC): comprising 20-50% of the total filler mass, with a length of 100-500 nm and a diameter of 10-30 nm. They serve as a reinforcing agent and modulate the rheological properties of the composite slurry, making it suitable for photopolymerization 3D printing.

[0025] Photoinitiator: 0.5-3%, selected from biocompatible 2e type free radical photoinitiators, such as phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (TPO).

[0026] 2. A method for preparing the above-mentioned fully bio-based multifunctional composite material, comprising the following steps: One-pot melt prepolymerization: Modified soybean oil epoxy resin, thioctic acid, phytic acid, and bio-based flexible segments were added to a reaction vessel and stirred for 1-4 hours under an inert gas (such as nitrogen) temperature range of 80-120℃. During this process, thioctic acid underwent ring-opening polymerization, with its carboxyl and epoxy groups reacting. Phytic acid was initially incorporated into the system through hydrogen bonding, forming a viscous prepolymer with photocurable activity and rich in dynamic bond precursors. By controlling the reaction time and temperature, the viscosity of the prepolymer reached 500-5000 mPa·s at 60℃.

[0027] In-situ dispersion of functional fillers and preparation of composite slurries: The temperature of the prepolymer is lowered to 50-70℃, a photoinitiator is added, and the mixture is mechanically stirred until homogeneous. Subsequently, under ice-water bath and ultrasonic conditions with a power of 300-600W, alkali lignin nanoparticles and cellulose nanocrystals are slowly added to the above mixture in batches or together, and ultrasonically dispersed for 30-90 minutes until the filler is uniformly dispersed, forming a homogeneous, stable composite slurry with shear-thinning properties.

[0028] Composite slurry at 25℃ and a shear rate of 1s - ¹The viscosity under these conditions is greater than 5000 mPa·s, while at a shear rate of 100 s⁻¹ - The viscosity under the specified conditions should be reduced to below 500 mPa·s to meet the rheological requirements of stereolithography (SLA) or digital light processing (DLP) 3D printing.

[0029] Photopolymerization 3D Printing and Gradient Structure Construction: The composite slurry is loaded into the feed tank of a photopolymerization 3D printing equipment with a multi-feed system.

[0030] Homogeneous structure printing: Using a single paste, the material is cured layer by layer under ultraviolet light with a wavelength of 365-405nm according to a preset three-dimensional model. The exposure time for each layer is 2-15s, and the layer thickness is set to 25-100μm to obtain a homogeneous structural part.

[0031] Gradient Functional Structure Printing: Through program control, composite slurries with different contents of two (or more) functional fillers are switched or mixed proportionally when printing different model areas. By adjusting the feed flow rate of different slurries in real time, continuous or stepwise changes in material composition are achieved during the printing process, thereby creating structural components with compositional and functional gradients in a single molding process. After printing, the uncured resin of the structural components is cleaned with anhydrous ethanol and post-cured at 40-60℃ for 10-30 minutes.

[0032] 3. Product characteristics and applications obtained from the described materials and methods: The fully bio-based composite materials and structural components prepared using the above components and processes exhibit the following comprehensive characteristics: Photothermal-shape memory synergistic effect: When the material is irradiated by an 808nm near-infrared laser, the lignin nanoparticles efficiently absorb light energy and convert it into heat energy, which can raise the local temperature of the material by more than 40°C within 10-30s, exceeding the transition temperature of its dynamic network. This triggers the material to quickly recover from a temporary shape to a permanent shape, with a shape fixation rate (Rf) ≥95% and a shape recovery rate (Rr) ≥90%.

[0033] Highly efficient self-healing capability: After cracks or damage occur, the material can undergo reversible exchange of its dynamic disulfide bonds and recombination of its hydrogen bond network under mild thermal stimulation of 60-80℃ or through the photothermal effect generated by near-infrared light irradiation, thus achieving self-repair. After 24 hours of repair, its mechanical properties (such as tensile strength) can recover to over 85%.

[0034] Excellent processability and mechanical properties: The material can be precisely manufactured into complex three-dimensional structures through photopolymerization 3D printing. After curing, the material has excellent mechanical properties: tensile strength 10-35MPa, elongation at break 50%-250%, Young's modulus 0.1-1.5GPa, which can be flexibly adjusted according to the ratio of flexible segments and fillers.

[0035] Green and environmentally friendly throughout the entire life cycle: All components are derived from biomass. After the composite material reaches the end of its service life, it can be controlled to degrade under specific acid-base catalytic conditions (such as an alkaline solution with pH=10~12) or in a composting environment. The degradation products are harmless to the environment.

[0036] Based on the above characteristics, this composite material is particularly suitable for manufacturing photothermal driven soft robot actuators, self-healing flexible strain / pressure sensor skins, and personalized intelligent medical assistive devices (such as thermoformable orthopedic external fixation braces).

[0037] The following section provides 10 examples and 3 comparative examples. All examples used acrylated epoxidized soybean oil with an epoxy value of 0.45 mol / 100g as the modified soybean oil epoxy resin, and TPO as the photoinitiator. The test methods are as follows: Photothermal performance: Using an 808nm near-infrared laser (1.0W / cm²) 2 Irradiate the sample surface (Φ10mm×2mm) and record the temperature change (ΔT) using an infrared thermal imager.

[0038] Shape memory performance: A sample (30 mm long, 5 mm wide, and 1 mm thick) was bent into a temporary shape (angle θ1) at 80°C and cooled to set. Its recovery process was then recorded under NIR irradiation, and the shape retention rate (Rf) and recovery rate (Rr) were calculated. Rf = θ1 / 180° × 100%; Rr = (θ1 - θ2) / θ1 × 100%, where θ2 is the angle after recovery.

[0039] Self-healing performance: The sample was completely cut, the cut surfaces were then glued together, and treated on a 70℃ hot plate for 24 hours. The tensile strength (σ) after repair was then tested. r The ratio of the original strength (σ0) to the original strength (σ0) is used as the repair rate.

[0040] Mechanical properties: Tensile properties and elongation at break were tested using a universal testing machine (ASTM D638, rate 10 mm / min).

[0041] Example 1 50wt% modified soybean oil epoxy resin, 25wt% thioctic acid, 8wt% phytic acid, and 10wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000 were added to a reaction vessel as bio-based flexible segments. Under a nitrogen atmosphere, the mixture was stirred and reacted at 100℃ for 2 hours to form a viscous prepolymer with photocurable activity and rich in dynamic bond precursors. The viscosity of the prepolymer reached 4000 mPa·s at 60℃.

[0042] The temperature of the prepolymer was lowered to 60°C, and 2 wt% of the photoinitiator phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added and mechanically stirred until homogeneous.

[0043] Subsequently, under ice-water bath and 500W ultrasonic conditions, 4wt% of alkali lignin nanoparticles and 1wt% of cellulose nanocrystals were slowly added to the above mixture in batches or together, and ultrasonically dispersed for 60 minutes until the filler was uniformly dispersed to form a homogeneous, stable composite slurry with shear thinning properties to meet the rheological requirements of stereolithography (SLA) 3D printing.

[0044] The composite slurry is loaded into the feed tank of a photopolymerization 3D printing equipment with a multi-feed system.

[0045] Homogeneous structure printing: Using a single paste, the material is cured layer by layer under ultraviolet light with a wavelength of 405nm according to a preset three-dimensional model. The exposure time for each layer is 5s and the layer thickness is set to 50μm to print a homogeneous structural part.

[0046] Example 2 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 40 wt% modified soybean oil epoxy resin, 30 wt% lipoic acid, 10 wt% phytic acid, 12 wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000, 2 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 4.8 wt% alkali lignin nanoparticles, and 1.2 wt% cellulose nanocrystals.

[0047] Example 3 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 60 wt% modified soybean oil epoxy resin, 15 wt% lipoic acid, 5 wt% phytic acid, 12 wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000, 2 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 4.8 wt% alkali lignin nanoparticles, and 1.2 wt% cellulose nanocrystals.

[0048] Example 4 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 65 wt% modified soybean oil epoxy resin, 18 wt% lipoic acid, 5 wt% phytic acid, 5 wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000, 1.8 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 4.2 wt% alkali lignin nanoparticles, and 1 wt% cellulose nanocrystals.

[0049] Example 5 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 50 wt% modified soybean oil epoxy resin, 25 wt% lipoic acid, 8 wt% phytic acid, 10 wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000, 2 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 2.5 wt% alkali lignin nanoparticles, and 2.5 wt% cellulose nanocrystals.

[0050] Example 6 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 65 wt% modified soybean oil epoxy resin, 18 wt% lipoic acid, 5 wt% phytic acid, 5 wt% polylactic acid-glycolic acid copolymer with a number average molecular weight (Mn) of 4000, 2 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 4 wt% alkali lignin nanoparticles, and 1 wt% cellulose nanocrystals.

[0051] Example 7 The difference from Example 1 lies in the amount of each component added, as shown below: The composition consists of 45 wt% modified soybean oil epoxy resin, 25 wt% lipoic acid, 8 wt% phytic acid, 10 wt% polycaprolactone diol with a number average molecular weight (Mn) of 4000, 2 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 9 wt% alkali lignin nanoparticles, and 1 wt% cellulose nanocrystals.

[0052] Comparative Example 1 The difference from Example 1 lies in the amount of each component added, as shown below: 55wt% modified soybean oil epoxy resin, 30wt% lipoic acid, 10wt% phytic acid, 1wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 3wt% alkali lignin nanoparticles and 1wt% cellulose nanocrystals.

[0053] Comparative Example 2 In Example 1, 25 wt% lipoic acid was replaced with an equal amount of the common curing agent methylhexahydrophthalic anhydride, while phytic acid was retained. The network consisted only of hydrogen bonding and chemical crosslinking, with no dynamic covalent bonds.

[0054] Comparative Example 3 The modified soybean oil epoxy resin (50wt%) in Example 1 was replaced with an equal amount of petroleum-based bisphenol A type epoxy acrylate, while the other components remained unchanged.

[0055] Comparative Example 4 The amount of each component added is the same as in Example 1. The prepared composite slurry is poured into a mold and cured as a whole under ultraviolet light irradiation with a wavelength of 365-405nm.

[0056] The products obtained in Examples 1-7 and Comparative Examples 1-4 were tested and analyzed, and the experimental data are shown in Table 1 below: Table 1 It can be seen from Table 1 above: Example 7, with its highest lignin content, exhibited a significantly higher photothermal conversion efficiency, demonstrating its potential as a high-efficiency photothermal driving material. Example 5, with its high CNC content and low lignin content, had the lowest ΔT. All examples containing dynamic networks had ΔT > 45°C, satisfying the triggering conditions. Comparative Example 1, due to excessive network rigidity, had a lower ΔT, affecting its heat transfer performance. The photothermal performance of Comparative Examples 2, 3, and 4 was comparable to that of Example 1, indicating that this performance primarily depends on the lignin filler.

[0057] All samples showed Rf > 95%, indicating that the network effectively fixed strain. Rr better reflects the network dynamics: the high Rr of Example 1 demonstrates the efficient responsiveness of the synergistic network of lipoic acid and phytic acid. Comparative Example 2, lacking dynamic disulfide bonds, had poor network reconstruction ability, resulting in the lowest Rr and incomplete recovery. Comparative Example 1 also had a low Rr due to insufficient network flexibility.

[0058] Examples 1-7 all demonstrated excellent self-healing capabilities, which are directly attributed to the dynamic covalent-non-covalent synergistic network composed of lipoic acid and phytic acid. Comparative Example 2 serves as the most direct comparison, demonstrating that the dynamic disulfide bonds provided by lipoic acid are the decisive factor in the material's self-healing ability.

[0059] Example 5 achieved the highest strength through high CNC content; Example 3 achieved the highest elongation at break through low crosslinking agent content. Comparative Example 1, lacking flexible segments, was extremely brittle, with an elongation at break of only 25%, demonstrating the necessity of flexible segments to ensure material toughness.

[0060] Although Comparative Example 3 is comparable to Example 1 in terms of performance and process, its bio-based carbon content is 0%, and it cannot be degraded in composting experiments.

[0061] Application Example 1 Two types of slurry were prepared: slurry A prepared according to Example 1, and slurry B with a total filler content of 5% and a lignin:CNC ratio of 1:1. A three-finger gripper model was designed, with the fingertip portion programmed to contain 100% slurry A, and the portion from the finger root to the arm linearly transitioning from 100% slurry A to 100% slurry B.

[0062] The resulting product exhibits the following performance characteristics: sensitive photothermal response at the fingertips (ΔT>50℃) and strong flexural recovery; increasing modulus from the fingertip to the forearm, providing stable support. Under periodic NIR irradiation, the gripper can accurately grasp and release objects weighing 20 times its own weight, and has a drive cycle life of >5000 cycles.

[0063] Application Example 2 The material from Example 1 was printed into a flexible substrate with a thickness of 0.5 mm. A liquid metal (Galinstan) microcrack sensing circuit was printed on its surface and then packaged to form a sensor.

[0064] The sensor was attached to the knuckle of the product obtained in Application Example 1. After the sensor (including the substrate and circuit) was completely pierced by a blade, the performance before and after repair at 70°C for 24 hours was basically the same.

[0065] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fully bio-based composite material, characterized in that, Includes the following percentages of material by mass: 35-65% modified soybean oil epoxy resin, 20-45% dynamic crosslinking agent combination, 5-20% bio-based flexible segments, 5-25% photothermal conversion and enhancing functional filler and 0.5-3% photoinitiator; The dynamic crosslinking agent combination includes lipoic acid and phytic acid; The lipoic acid ring-opening polymerization forms a network rich in dynamic disulfide bonds, and the phytic acid provides hydrogen bond crosslinking sites, constituting a dynamic covalent-non-covalent synergistic crosslinking network.

2. The all-bio-based composite material according to claim 1, characterized in that, The dynamic crosslinking agent combination includes 15-35% thioctic acid and 5-15% phytic acid, which account for 15-35% of the total mass of the composite material.

3. The all-bio-based composite material according to claim 1, characterized in that, The bio-based flexible segments are polycaprolactone diol or polylactic acid-hydroxyacetic acid copolymer with a number average molecular weight of 2000-10000; the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

4. The all-bio-based composite material according to claim 1, characterized in that, The photothermal conversion and enhancement functional filler comprises the following materials by mass percentage: It contains 50-80% alkali lignin nanoparticles and 20-50% cellulose nanocrystals.

5. A method for preparing a fully bio-based composite material according to any one of claims 1-4, characterized in that, Includes the following steps: S1 One-Pot Melt Prepolymerization: Modified soybean oil epoxy resin, dynamic crosslinking agent combination and bio-based flexible segments are reacted at 80-120℃ under inert gas protection for 1-4 hours to form a prepolymer; S2 Functional Filler Dispersion: The prepolymer is cooled, a photoinitiator is added, and then a photothermal conversion and reinforcing functional filler is added. The mixture is then ultrasonically dispersed to form a uniform composite slurry. S3 Photopolymerization Molding: The composite slurry is photopolymerized and 3D printed to obtain the structural component of the composite material.

6. The method for preparing the all-bio-based composite material according to claim 5, characterized in that, The photopolymerization molding is a photopolymerization gradient 3D printing molding process, including the following steps: By using at least two composite slurries with different contents of photothermal conversion and reinforcing fillers, and by controlling the feed ratio of different slurries during the printing process through a program, structural parts with compositional and performance gradients can be constructed in a single printing process.

7. The method for preparing the all-bio-based composite material according to claim 5, characterized in that, The composite slurry prepared by S2 is subjected to a shear rate of 1 second at 25°C. -1 The viscosity under the given conditions is greater than 5000 mPa·s, at a shear rate of 100 s⁻¹. -1 The viscosity under the given conditions is less than 500 mPa·s; In S3, the ultraviolet light wavelength for photopolymerization 3D printing is 365-405nm, the single-layer exposure time is 2-15s, and the layer thickness is 25-100μm.

8. A fully bio-based multifunctional composite material structural component prepared by the preparation method according to any one of claims 5-7, characterized in that, The structural components have compositional and functional gradients, with the filler content in different regions varying continuously or in steps.

9. An application of a fully bio-based multifunctional composite material as described in any one of claims 1 to 4, characterized in that, Application of the fully bio-based multifunctional composite material in the preparation of photothermal driven soft robot actuators or self-healing flexible sensors.

10. The application according to claim 9, characterized in that, By utilizing the photothermal-shape memory synergistic effect of the composite material, non-contact actuation of the actuator can be achieved under 808nm near-infrared light irradiation; Alternatively, the self-healing properties of the composite material at 60-80℃ can be utilized to restore the mechanical and electrical properties of the sensor after damage.

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