Application of rodlike ferroferric oxide Fe3O4 nanoparticles in preparation of magnetoelectric coupling fiber, magnetoelectric coupling fiber and magnetoelectric support

Abstract

The invention provides an application of rod-like ferroferric oxide Fe3O4 nanoparticles in preparation of magnetoelectric coupling fibers, and further provides a preparation method of the rod-like ferroferric oxide Fe3O4 nanoparticles. The invention also provides a magnetoelectric coupling fiber. The magnetoelectric coupling fiber is prepared by embedding the rodlike ferroferric oxide Fe3O4 nanoparticles into the PVDF-TrFE fiber through an electrostatic spinning process. The invention also provides a preparation method and application of the magnetoelectric coupling fiber. The rod-shaped Fe3O4 nanoparticles are adopted, magnetoelectric coupling is enhanced, and extra stress deflection force is generated under the action of a magnetic field through the rod-shaped Fe3O4 nanoparticles with high length-diameter ratio, so that piezoelectric output is enhanced, and signal sensitivity is improved; and in combination with COMSOL simulation analysis, the particle morphology influence is deeply studied. The rod-shaped Fe3O4 particles can enhance magnetoelectric coupling, so that the rod-shaped Fe3O4 particles are not only suitable for flexible sensors, but also can be further expanded to high-end application fields such as nano-generators, neural restoration and intelligent response materials, and have wider application potential.

Description

Technical Field

[0001] The present invention relates to the application of rod-shaped iron tetroxide Fe 3 O 4 nanoparticles in the preparation of magnetoelectric coupling fibers, as well as a magnetoelectric coupling fiber and a magnetoelectric mechanical support. Background Art

[0002] Electrical stimulation is easy to effectively maintain the bioelectric field of cells and has been proven to promote the repair and regeneration of damaged nerve tissue. Nowadays, many invasive electrical stimulation (IES) systems have been developed. However, IES systems usually require long-term tissue penetration and percutaneous wires to connect bulky electrochemical power sources, which limits the operational convenience and increases the risk of infection. In addition, most IES systems always result in excessive charge accumulation on the cell membrane, thus causing nerve stimulation-inertia and subsequent inflammation, immune rejection, and nerve growth inhibition. Due to these drawbacks, there is an urgent need to develop a radio stimulation (WES) system with controllable electrical signal output for nerve tissue engineering applications.

[0003] Piezoelectric materials can convert mechanical forces from different sources into electrical signals. Among them, polyvinylidene fluoride (PVDF) has received extensive attention due to its excellent processing feasibility and excellent sensitivity to tiny mechanical forces. Structurally, PVDF represents five crystalline polymorphs, including α, β, γ, δ, and ε phases. Among them, the β phase exhibits a fully trans planar zigzag conformation, which can result in a significant dipole moment. Therefore, increasing the proportion of the β phase of PVDF is the key to enhancing its piezoelectric effect to output more electrical stimulation. So far, many strategies have been proposed to solve this problem, including modification with copolymers and combination with electrospinning technology. In addition, nanoparticles as nucleating agents are also allowed to be added to PVDF to induce the formation of the β phase. Nevertheless, using a single piezoelectric material only considers mechanical stimulation triggered by single-source cell force or tissue movement, and abandons diverse physical cues from the microenvironment, including electrical, ultrasonic, and magnetic cues. Integrating or constructing a cascade system of multiple physical strategies simultaneously may be more beneficial to improving the output ES.

[0004] The currently reported piezoelectric materials have the following defects:

[0005] 1. Insufficient interfacial interaction between nanoparticles with controllable morphology and fibers

[0006] In the prior art, most only focus on the introduction of spherical Fe 3 O 4 particles and lack the research on the mechanical coupling mechanism of high aspect ratio nanoparticles.

[0007] 2. Insufficient understanding of the stress distribution and electrical output under external magnetic field triggering

[0008] Existing solutions mostly stay at the preliminary verification of magnetic response and piezoelectric output, lacking in-depth research on the internal stress distribution of fibers under the action of a magnetic field for long rod-shaped nanoparticles.

[0009] 3. Insufficient fiber structure orientation and β-phase induction

[0010] Existing technologies are difficult to comprehensively optimize fiber orientation, nanoparticle dispersion, and β-phase crystallinity.

[0011] Patent Application Number: 202410586053.X, Invention Title: A PVDF-TrFE / Fe 3 O 4 nanofiber sensitive material and its flexible and stretchable array sensor, relating to a PVDF-TrFE / Fe 3 O 4 nanofiber sensitive material and its flexible and stretchable sensor. It mainly solves the technical problems of poor stretchability and low stability existing in the production of stretchable flexible sensors with existing PVDF-TrFE nanofibers. The technical solution adopted by this invention is: A PVDF-TrFE / Fe 3 O 4 nanofiber sensitive material, which is made of PVDF-TrFE powder with a molar ratio of PVDF to TrFE of 8:2 and a concentration of 10 wt%, 5 wt% of Fe3O4 nanoparticles, and a solvent mixture composed of acetone and N-dimethylformamide. This patent has limitations in the following aspects:

[0012] 1. The morphology of nanoparticles is single, and the anisotropic effect is not fully utilized

[0013] This patent only uses spherical Fe 3 O 4 nanoparticles with a size of 10 - 20 nm, which makes the stress transfer under the action of a magnetic field relatively uniform, unable to effectively utilize the anisotropic characteristics of rod-shaped nanoparticles to enhance the local stress concentration effect, thus limiting the improvement of piezoelectric performance.

[0014] 2. The stress deflection force under the action of a magnetic field is not fully considered

[0015] This patent mainly focuses on the influence of nanoparticles on the piezoelectric response of PVDF-TrFE fibers, but does not study the regulation of the stress transfer path by the particle morphology when an external magnetic field is applied, so there are deficiencies in magnetoelectric coupling enhancement.

[0016] 3. Insufficient comparative analysis of nanoparticles with different morphologies

[0017] This patent only conducts research on spherical Fe 3 O 4 particles, lacking research on Fe with different morphologies (such as rod-shaped)3 O 4 Analysis of the distribution, orientation of nanoparticles in PVDF-TrFE fibers and their effects on electrical properties cannot fully prove which particle morphology is more beneficial to the improvement of piezoelectric properties. Summary of the Invention

[0018] The present invention provides a novel magnetoelectric scaffold for promoting peripheral nerve regeneration and repair. Through electrospinning, anisotropic Fe with a high β-phase crystallinity was obtained 3 O 4 nanorod integrated polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) fiber scaffold. Compared with isotropic Fe 3 O 4 nanoparticles (SFO), the use of anisotropic Fe 3 O 4 nanorods (RFO) increases the coupling area between the magnetostrictive Fe3O4 phase and the piezoelectric PVDF-TrFE phase. In addition, under an applied alternating magnetic field, the initially randomly distributed RFOs are prone to micro-vibrations along the direction of the applied magnetic field, thereby generating a continuous deflection force in the directly contacted PVDF-TrFE region. Benefiting from efficient magneto-mechanical-electrical conversion, the PTRFO scaffold with high ES output shows great potential in promoting PNI regeneration, which is confirmed by the repair of rat sciatic nerve injury. More importantly, this study provides a new strategy to construct a cellular microenvironment by integrating various physical cues.

[0019] The present invention provides an application of rod-shaped iron oxide Fe 3 O 4 nanoparticles in the preparation of magnetoelectric coupling fibers.

[0020] The present invention provides a magnetoelectric coupling fiber, which is obtained by embedding rod-shaped iron oxide Fe 3 O 4 nanoparticles into the interior of PVDF-TrFE fibers through an electrospinning process.

[0021] Wherein, the mass ratio of the rod-shaped iron oxide Fe 3 O 4 nanoparticles to PVDF-TrFE is:

[0022] Rod-shaped iron oxide Fe 3 O 4 nanoparticles 1 part, PVDF-TrFE 25 - 41 parts.

[0023] Preferably, the mass ratio of the rod-shaped iron oxide Fe 3 O 4 nanoparticles to PVDF-TrFE is:

[0024] Rod-shaped Fe₃O₄ 3 O 4 nanoparticles 1 part, PVDF-TrFE 33 parts.

[0025] Among them, the rod-shaped Fe₃O₄ 3 O 4 The preparation method of the nanoparticles includes the following steps:

[0026] a. FeOOH synthesis: Take FeCl 3 Dissolve it in water, put it in a flask and stir, and react at 87 °C for 18 h;

[0027] Temperature and time are crucial for the initial morphology formation of FeOOH nanorods. If the temperature is too low or the reaction time is insufficient, it is difficult to form a stable rod-shaped structure; if the temperature is too high or the time is too long, it may cause excessive growth of particles or loss of morphology control.

[0028] b. Polyacrylic acid PAA shell protection: Take the dispersed FeOOH solution prepared in step a, dissolve it in water, stir for 5 min, add 80 mg / ml PAA, 1 ml ammonia water and stir for 5 min, and finally react in an oil bath at 60 °C for 24 h to obtain FeOOH-PAA NRs;

[0029] This temperature and time determine the degree of binding between PAA and the surface of FeOOH nanorods. Excessive PAA or insufficient reaction time may both lead to uneven surface modification, thus affecting the morphology stability in the subsequent reduction stage. The PAA concentration directly determines the degree of surface modification of the FeOOH rod-shaped structure. Too low a concentration will result in insufficient protection layer, and too high a concentration is likely to cause particle aggregation or too high viscosity, affecting subsequent reactions.

[0030] c. Fe 3 O 4 Reduction

[0031] Dissolve FeOOH-PAA NRs in diethylene glycol DEG, add DEG to the flask, heat the solution to 220 °C under nitrogen protection and then add the mixed solution, and react for 8 h to obtain. The high-temperature reduction environment (combined with nitrogen protection) in this step is the key to converting FeOOH to Fe 3 O 4 . Too low a temperature is difficult to achieve complete reduction, and too high a temperature or too long a time may cause breakage or aggregation of the nanorods.

[0032] In the rod-shaped Fe₃O₄ 3 O 4During the preparation process of the nanoparticles, in the first and second steps, water is used as the main solvent, combined with acetone, DMF or other systems; in the third step, high-temperature reduction is carried out in diethylene glycol (DEG). The selection and ratio of these solvents directly affect the growth environment, surface charge and crystal growth kinetics of the nanorods, and are important factors to ensure the rod-like morphology and dispersion. During the high-temperature reduction process at 220 °C, nitrogen protection can prevent oxidation and reduce side reactions, which is crucial for the formation of high-purity and morphologically stable Fe 3 O 4 rod-shaped nanoparticles.

[0033] Compared with the rod-shaped iron oxide nanoparticles prepared by the existing reported methods, the main advantages of the Fe 3 O 4 nanoparticles are as follows:

[0034] 1. Multi-step controllable morphology growth

[0035] This process adopts a multi-step strategy of "first synthesizing FeOOH nanorods → PAA coating → high-temperature reduction to obtain Fe 3 O 4 " to finely control the morphology and size of the nanorods. Compared with the common one-step hydrothermal / solvothermal method, this multi-step method can regulate the morphology at each step, and finally obtain stable and well-dispersed rod-shaped Fe 3 O 4 .

[0036] 2. Protection and dispersibility of the PAA shell

[0037] PAA modification is completed at medium temperature (60 °C) for a long time (24 h), so that the nanorods can still maintain the rod-shaped structure during subsequent high-temperature reduction, and are not easy to agglomerate or break. Compared with the reduction method without a protective agent, this process is beneficial to improving the dispersibility and morphological consistency of the product.

[0038] 3. Mild conditions and reproducibility

[0039] The temperature for the formation of FeOOH in the first stage is only 87 °C and it is carried out in the aqueous phase; although the reduction temperature in the third stage is relatively high at 220 °C, the use of the DEG system and nitrogen protection can ensure the stability of the process and reduce the generation of by-products. The overall process does not adopt ultra-high temperature or extreme conditions, and has better operability and reproducibility.

[0040] 4. Higher correlation between morphology and performance

[0041] The rod-shaped Fe 3 O 4, with an adjustable aspect ratio, and when combined with a polymer (such as PVDF-TrFE) in the subsequent process, the anisotropy of the rod-shaped particles can be further utilized to enhance the magneto-mechanical coupling and piezoelectric properties, which is superior to the common spherical or short rod-shaped Fe 3 O 4 Limitations in improving the performance of piezoelectric materials.

[0042] 5. Adapt to subsequent functionalization or composite processes

[0043] This process uses PAA modification in the intermediate step, providing better interfacial bonding force for subsequent combination with polymers or other surfactants; at the same time, after the high-temperature reduction is completed, the surface of the Fe 3 O 4 nanorods still have certain modifiable sites, facilitating later functionalization (such as surface modification with dopamine, silane, etc.).

[0044] The present invention provides a method for preparing the magnetoelectric coupling fiber as described above, which includes the following steps:

[0045] a. Take a mixed solution of DMF / acetone (V:V = 3:2) and prepare a 16wt% PVDF-TrFE spinning solution, and stir for 15 minutes;

[0046] b. Add rod-shaped iron oxide Fe 3 O 4 nanoparticles, ultrasonically disperse for 30 min, load the mixed solution into a 10 ml syringe, and perform electrospinning. The electrospinning parameters are: nozzle flow rate 1 ml / h, r (distance from the tip to the collection bucket) = 15 cm, V (voltage) = -2 to 13 kV, n (rotation speed of the collection bucket) = 500, spraying distance 5 cm; spinning time 2 h, and then put it into an oven for drying.

[0047] The present invention provides a magnetoelectric mechanical support, which contains the magnetoelectric coupling fiber as described above.

[0048] The present invention also provides the application of the magnetoelectric mechanical support in the fields of sensors, energy collectors or biomedicine.

[0049] Among them, the magnetoelectric mechanical support is used for nerve repair and regeneration, muscle or bone tissue engineering, implantable or wearable biosensors, energy collection and self-driven devices, and intelligent responsive materials.

[0050] Among them, for the nerve repair and regeneration material, with the aid of an external magnetic field excitation, the magnetic nanoparticles in the scaffold generate mechanical strain and induce electrical signals, stimulating the differentiation of nerve cells (such as PC12, etc.) and axon growth; meanwhile, the flexible fiber structure of the scaffold can serve as a physical channel for nerve growth, and is used for the repair of peripheral nerves such as sciatic nerve injury. For the muscle or bone tissue engineering material, through the periodic loading of the magnetic field, the scaffold can output weak electrical stimulation, enhancing the proliferation and differentiation of muscle cells or osteoblasts; meanwhile, the scaffold has good mechanical support and is suitable for providing external force guidance and a stabilizing effect at the defect site, promoting tissue regeneration. For the implantable or wearable biosensor, the multi-field coupling of the piezoelectric polymer and magnetic particles in the scaffold facilitates the real-time detection of external pressure or deformation; combined with wireless magnetic field triggering, it can be used as a flexible biosensor with higher sensitivity to monitor the tiny mechanical changes in the body or on the body surface. For the energy harvesting and self-powered device: when there is environmental vibration or an external magnetic field, the scaffold can convert mechanical energy or magnetic energy into electrical energy to provide power for microelectronic devices; in the biomedical scenario, it can extend the battery life of implantable devices and reduce the frequency of battery replacement. For the intelligent response material: it can be remotely controlled by using a magnetic field, enabling the scaffold to generate electrical or mechanical stimulation at the target position, which is used for accelerating wound healing, controlling drug release, or assisting rehabilitation training, etc., more flexibly meeting clinical needs.

[0051] The advantages of the present invention are as follows:

[0052] 1. Using rod-shaped Fe 3 O 4 nanoparticles to enhance magnetoelectric coupling

[0053] Through rod-shaped Fe 3 O 4 nanoparticles with a high aspect ratio (major axis 380 nm, minor axis 82 nm), an additional stress deflection force is generated under the action of a magnetic field, thereby enhancing the piezoelectric output and improving the signal sensitivity.

[0054] 2. Combining COMSOL simulation analysis to deeply study the influence of particle morphology

[0055] Using COMSOL simulation to study the stress distribution and strain transfer of Fe 3 O 4 particles with different morphologies inside the fiber, and clarifying how the long rod-shaped nanoparticles enhance the stress concentration effect under the action of a magnetic field, thereby providing a more reasonable design basis.

[0056] 3. Suitable for energy harvesting and sensor devices with higher performance requirements

[0057] Due to rod-shaped Fe 3 O 4The particles can enhance the magnetoelectric coupling. The present invention is not only applicable to flexible sensors, but can also be further extended to high-end application fields such as nanogenerators, nerve repair, and intelligent response materials, with broader application potential.

[0058] The beneficial effects of the present invention are as follows:

[0059] 1. Strengthen stress transfer and improve electrical output

[0060] Since the present invention uses rod-shaped Fe 3 O 4 nanoparticles with a high aspect ratio, an additional "deflection force" can be generated under the action of an external magnetic field, making the local stress inside the fiber more concentrated, thereby enhancing the polarization degree and β-phase content of the PVDF-TrFE fiber, and improving the overall piezoelectric and magnetoelectric coupling performance.

[0061] 2. Balance the mechanical properties and structural stability of the fiber

[0062] By modifying the surface of the nanorods and optimizing the electrospinning parameters, the present invention realizes good dispersion and strong interfacial bonding of the nanoparticles while maintaining the basic mechanical properties of the fiber, avoiding the performance degradation caused by particle agglomeration or uneven dispersion in the prior art.

[0063] 3. Suitable for a wider range of biological or sensing applications

[0064] The composite fiber of the present invention can play a role in the fields of biomedical sensing, nanogenerators, etc., providing higher electrical output and stability, overcoming the limitations in the prior art that can only achieve preliminary magnetic response or low piezoelectric output, and providing a more feasible technical solution for related application scenarios. Description of the Drawings

[0065] Figure 1 For the preparation and characterization of FO (where A is SEM and EDX analysis, B is particle size statistics, C is XRD analysis, D is XPS analysis, E is VSM analysis, F and G are EDS analysis);

[0066] Figure 2 For the preparation and characterization of three scaffolds (A is SEM analysis, B is diameter statistics, C is XPS analysis, D is FTIR analysis, E is XRD analysis, F is β-phase content statistics);

[0067] Figure 3 For the magnetoelectric effect characterization of three scaffolds (Figure A shows the pressure response phase curve of the three scaffolds and Figure B shows the amplitude voltage, Figures C - F show the finite element simulation of the magnetoelectric effect of two scaffolds, including the stress change and potential distribution generated on the fiber);

[0068] Figure 4H&E staining images of the sciatic nerve 4 weeks after magneto-mechanical-electrical scaffolds enhanced PNI for nerve regeneration therapy. Detailed implementation mode

[0069] Example 1 Preparation of the magnetoelectric coupling fiber of the present invention

[0070] I. Synthesis of rod-shaped FO nanoparticles

[0071] 1. Synthesis of FeOOH:

[0072] 4 mol FeCl 3 Dissolve it in 40 ml of water, put it into a flask and stir, and react at 87 °C for 18 h; 2. Protection of the PAA shell

[0073] Take 4.6 ml of the dispersed FeOOH solution and dissolve it in 15.4 ml of water, stir for 5 min, add 80 mg / ml PAA, 1 ml of ammonia water and stir for 5 min, and finally react in an oil bath at 60 °C for 24 h;

[0074] 3. Reduction of Fe3O4

[0075] Dissolve FeOOH-PAA NRs in 8 ml of DEG, add 20 ml of DEG to the flask, heat the solution to 220 °C under nitrogen protection and then add the mixed solution, and react for 8 h;

[0076] Washing: Wash three times with ethanol first, centrifugation: 11000 rpm, 8 min / time; then wash three times with RO water; then continue to wash twice with ethanol;

[0077] Storage: Resuspend and store in 20 ml of ethanol.

[0078] II. Electrospinning:

[0079] Raw materials: PVDF-TrFE 16 wt%, solvent: DMF / acetone (V:V = 3:2), 20 mg FO

[0080] Take 5 ml of the mixed solution (DMF / acetone (V:V = 3:2)), prepare a 16 wt% PVDF-TrFE spinning solution, stir for 15 minutes, add 20 mg FO, ultrasonically disperse for 30 min, load the mixed solution into a 10 ml syringe, set the electrospinning parameters: nozzle flow rate 1 ml / h r (distance from the tip to the collection bucket) = 15 cm, V (voltage) = -2 to 13 kV, n (collection bucket rotation speed) = 500, spraying distance 5 cm, spinning time 2 h, and then put it into the oven to dry overnight.

[0081] Example 2 Preparation of magnetic Fe3O4 nanoparticles with different morphologies

[0082] Synthesis of spherical FO nanoparticles:

[0083] Raw materials: ferric chloride, trisodium citrate, ammonium acetate

[0084] ① 1.35 g of FeCl3·6H2O, 0.46 g of trisodium citrate (anhydrous), and 3.854 g of NH4Ac were successively added to 70 ml of ethylene glycol every 15 minutes under stirring;

[0085] ② The mixture was stirred at room temperature for 1.5 h to form a homogeneous black solution;

[0086] ③ It was transferred to a 100 ml autoclave and reacted at 200 °C for 8 h;

[0087] ④ It was cooled to room temperature, and the black precipitate was collected with a magnet.

[0088] First, two kinds of nanoparticles were synthesized: SFO (spherical FO nanoparticles) and RFO (rod-shaped FO nanoparticles). SFO was prepared by a simple one-step hydrothermal reaction. To obtain RFO, we adopted a surface protection method to transform non-magnetic FeOOH nanorods into magnetic RFO.

[0089] Figure 1 A shows the scanning electron microscope (SEM) images of SFO and RFO, which indicate completely different morphologies. High-resolution transmission electron microscope (TEM) images and energy-dispersive X-ray spectroscopy (EDX) mapping analysis were also obtained, as Figure 1 shown in A. Through analysis, the average diameter of SFO is about 210 nm, while the average length of RFO is about 379 nm and the average width is about 82 nm ( Figure 1 B). Subsequently, the X-ray diffraction (XRD) pattern shows that the characteristic peaks corresponding to Fe 3 O 4 are observed in both SFO and RFO ( Figure 1 C). In addition, the energy-dispersive spectroscopy (EDS) shows that Fe and O elements can be found in both SFO and RFO, and their Fe:O ratio is approximately 3:4, which further proves that the crystal phase is Fe 3 O 4 ( Figure 1 F, Figure 1 G). In addition, X-ray photoelectron spectroscopy (XPS) confirms the presence of Fe 2p and O 1s peaks in both types of Fe 3 O 4 nanoparticles ( Figure 1 D). Then, the magnetism was studied by a vibrating sample magnetometer (VSM). As Figure 1 shown in E, the VSM curve shows that although there are multiple-step reactions, RFO still has 26 emu·g -1The saturation magnetization indicates excellent magnetic responsiveness.

[0090] Example 3 Composition of the magneto-mechanical-electric bracket of the present invention

[0091] Under electrospinning conditions, the β-phase of the PVDF-based material is usually obtained by stretching the molecular dipoles along the direction of the applied voltage. Compared with pure PVDF, the copolymerized PVDF-TrFE has a higher β-phase crystallinity, resulting in more aligned dipole moments, which endows it with improved piezoelectric responsiveness. Therefore, magnetic Fe 3 O 4 nanoparticles were integrated into the piezoelectric PVDF-TrFE fiber matrix by electrospinning technology to prepare a magneto-mechanical-electric bracket. Both the SFO / PVDF-TrFE fiber bracket (SFOPT) and the RFOPT showed a uniform fiber structure and successful embedding of magnetic nanoparticles ( Figure 2 A). Under an external electric field, due to surface tension, SFO and RFO dispersed in the initial PVDF-TrFE solution were respectively covered by the PVDF-TrFE layer instead of being located on the surface of the PVDF-TrFE layer. Compared with the pure PVDF-TrFE bracket (PT), the average fiber diameters of both SFOPT and RFOPT increased slightly, indicating that the nano-fillers have a direct effect on the size of the PVDF-TrFE fibers ( Figure 2 B). At the same time, compared with isotropic SFO, anisotropic RFO led to a smaller increase in the average fiber diameter of the PVDF-TrFE fibers. We also studied the XPS spectra and found peaks of с, F, Fe, and O ( Figure 2 C). A binding energy of 710 eV was found in both SFOPT and RFOPT. However, due to the existence of the Auger effect, peaks corresponding to F in the range of 680–710 eV were also found in pure PVDF-TrFE, indicating that there is no obvious difference between the peaks of FE and F. Then, we studied the β-phase crystallization in these two magneto-mechanical-electric brackets with different magnetic Fe 3 O 4 nanoparticles. Figure 2 D shows the FT-IR spectra of pure PT, SFOPT, and RFOPT, and the characteristic β-phase crystallization peaks appearing at 840 cm -1 were observed for all three brackets. Figure 2Figure E depicts the XRD patterns of three scaffolds. The pure PVDF-TrFE scaffold is mainly in the non-polar α-phase, with characteristic peaks at 2θ = 18.4 (corresponding to the (202) plane) and 26.6 (corresponding to the (1 1 0 / 0 2 1) plane), and a low-intensity β-phase characteristic peak at 2θ = 20.7 (corresponding to the (1 1 0, 2 0 0) plane). Adding SFO and RFO to PVDF-TrFE respectively reduces the α-phase content in the SFOPT and RFOPT scaffolds and partially converts the α-phase into the β-phase. Due to the ion-dipole interaction occurring between the CH2 dipoles of the PVDF chains and the oxygen and / or hydroxyl groups on the surface of the 3 O 4 Fe3O4 nanoparticles 5, the (1 1 0, 2 0 0) plane of the β-phase forms within these two Fe3O4 nanoparticle-integrated scaffolds. The β-phase crystallinity content is calculated from the XRD patterns. The results show that the β-phase content in the SFOPT scaffold (66.13%) and the RFOPT scaffold (75.34%) is higher compared to that of the pure PT scaffold (48.02%). Apparently, the RFOPT scaffold with anisotropic Fe 3 O 4 nanoparticles has the highest β-phase content.

[0092] Compared with the pure PT scaffold, the introduction of magnetic Fe 3 O 4 nanoparticles increases the β-phase content of PVDF. The Fe3O4 nanoparticles as fillers trigger the nucleation effect, which is regulated by the interaction between the negatively charged surface of the Fe 3 O 4 nanoparticles and the positively charged C-H bonds of the PVDF chains. This electrostatic interaction mediated by Fe 3 O 4 nanoparticles affects the formation of the electroactive β-phase during the PVDF crystallization process. Apparently, the specific surface area (SSA) of these Fe 3 O 4 nanoparticles determines the magnitude of this electrostatic interaction ( Figure 2 F). The specific surface area of the RFO nanoparticles is calculated to be approximately 0.0538 nm -1 , which is higher than that of the SFO nanoparticles (approximately 0.0143 nm -1 ). Theoretically, introducing RFO nanoparticles with a higher SSA into PVDF should have the ability to nucleate more electroactive β-phase. This is consistent with the results of Figure 2 F.

[0093] Example 4 Magneto-Piezoelectric Performance Output of the Invention

[0094] The β-phase content directly affects the piezoelectricity of PVDF-based materials. Therefore, the piezoelectric properties of PT, SFOPT, and RFOPT scaffolds were investigated by piezoresponse force microscopy (PFM). Figure 3 A shows the local single-point phase recording. It clearly shows the ferroelectric phase responses of the three scaffolds. When the positive direct current (DC) bias increases, the dipoles of the PVDF crystallites in these three scaffolds begin to reorient along the applied direction, showing related phase transition responses. The coercive voltages of the RFOPT scaffold measured from the hysteresis curves are -0.47 V and 0.62 V, lower than those of pure PT (-0.82 V and 1.66 V) and the SFOPT scaffold (-0.63 V and 1.89 V). The reduction in the coercive voltage of the RFOPT scaffold means that the operating voltage for polarization switching is relatively low, which is beneficial for low-cost practical applications. It is worth noting that applying an external MF does not change the ferroelectric responsiveness of the SFOPT and RFOPT scaffolds, showing almost identical hysteresis loops with or without MF. The amplitude hysteresis response (butterfly loop) was also measured, as Figure 3 B shows. Compared with other scaffolds with or without an external MF, the RFOPT scaffold exhibits significantly higher amplitudes, which is consistent with the trend of their β-phase content. In addition, based on the PFM results, the piezoelectric coefficient was calculated, and the RFOPT scaffold showed the highest d33 of 42.67 pm / V, which is almost 2.1 times that of the SFOPT scaffold and 1.23 times that of the pure PT scaffold. Such a high d33 value is also higher than other reported PVDF-based scaffolds, thin films, and hydrogels.

[0095] The electrical output of the magneto-electro-mechanical scaffolds was simulated by the finite element method.

[0096] In the simplified model, both ends of the magnetic nanoparticles, including SFO and RFO nanoparticles, serve as fixed constraint points within a single PVDF-TrFE nanofiber and vary with the direction of the nanofiber. The strain distribution is as Figure 3 shown in C. Under the applied magnetic field, the strain at the contact surface between the magnetic nanoparticles and the PVDF-TrFE nanofiber can trigger the piezoelectric effect. Due to the anisotropic shape, the RFO nanoparticles with sharp ends generate higher strain than the isotropic SFO nanoparticles. As the applied magnetic field increases, the maximum strain near the surface of the SFO and RFO nanoparticles also increases. Apparently, the RFO nanoparticles trigger higher strain under the same MF. As a result, the piezoelectric potential generated by the RFOPT scaffold ranges from 8.13×10 -12 V to 3.25×10 -9 V with the external MF increasing from 10 to 200 mT ( Figure 3E&F). The theoretical piezopotential of the RFOPT scaffold is greater than that of the SFOPT scaffold, which is consistent with the higher β-phase content and different strain distributions in the two systems. In fact, the anisotropic RFO nanoparticles are not aligned along the long axis of the PVDF-TrFE nanofibers. For the RFOPT scaffold, in addition to the MF force along the nanofibers, an additional deflection force is generated at the interface between PVDF-TrFE and RFO nanoparticles, resulting in a higher piezoelectric effect. In contrast, no additional deflection force is formed within the SFOPT scaffold under a magnetic field parallel to the nanofibers.

[0097] Example 5 In Vivo Therapeutic Efficacy

[0098] All animal experiments were conducted in accordance with the ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines. In addition, all animal experiments in this study were approved by the Animal Health and Use Committee of Sichuan University (Approval number: SYXK (Sichuan): 2019 - 189). The experiments were performed using female Sprague-Dawley (SD) rats (200 - 220 g, obtained from Chengdu Dossy). The female SD rats were randomly divided into 5 groups (n = 5 / group): sham group, PNI group, PT group, RFOPT-MT group, and RFOPT+MT group (where the Sham group is the sham operation group, the PNI group is the complete injury group, the PT group is the pure PVDF-TrFE scaffold, and RFOPT is the scaffold of the present invention, ±MF represents magnetic field treatment and no magnetic field treatment). First, after anesthesia by intraperitoneal injection of sodium pentobarbital (50 mg kg -1 )), the hair on the left thigh of the rats was shaved off. Then, a 15 mM incision was made on the thigh using a scalpel, and the sciatic nerve was observed by dissecting the gluteal muscles. Next, a crush injury model was created by clamping the sciatic nerve (5 mm) with a vascular clamp for 5 minutes. The PT and RFOPT scaffolds were used to treat nerve defects respectively. For the RFOPT+MT group, the rats were placed in a Helmholtz coil (15 mT, load 50%, 100 Hz) for 15 minutes every day. The scaffold patch was implanted by curling and wrapping without any additional sutures. In the PNI group, only the sciatic nerve without any implanted material was crushed. For the sham operation group, the sciatic nerve was exposed and sutured without any other treatment. After 28 days of surgery, the nerve tissues were collected for analysis.

[0099] H&E staining was performed to observe the overall repair effect of the damaged nerve 4 weeks after the operation ( Figure 4)。The results showed that the axonal fibers in the PNI group had a sparse hollow state with obvious damage, while the axonal fibers in the PT-RFO+MF group showed a highly concentrated and good state, and their structure was similar to that of the sham operation group. In contrast, the repair effect of the nerve fibers in the remaining two groups was equivalent between these two groups.

Claims

1. Application of rod-shaped ferroferric oxide Fe3O4 nanoparticles in the preparation of magnetoelectric coupling fibers.

2. A magnetoelectric coupling fiber, characterized in that: It embeds rod-shaped ferroferric oxide Fe3O4 nanoparticles into PVDF-TrFE fibers through an electrospinning process.

3. The magnetoelectric coupling fiber according to claim 2, characterized in that: The mass ratio of the rod-shaped ferroferric oxide Fe3O4 nanoparticles to PVDF-TrFE is: 1 part of rod-shaped ferroferric oxide Fe3O4 nanoparticles and 25-41 parts of PVDF-TrFE.

4. The magnetoelectric coupling fiber according to claim 3, characterized in that: The mass ratio of the rod-shaped ferroferric oxide Fe3O4 nanoparticles to PVDF-TrFE is: 1 part of rod-shaped ferroferric oxide Fe3O4 nanoparticles and 33 parts of PVDF-TrFE.

5. The magnetoelectric coupling fiber according to claim 3 or 4, characterized in that: The preparation method of the rod-shaped ferroferric oxide Fe3O4 nanoparticles comprises the following steps: a. Synthesis of FeOOH: Dissolve FeCl3 in water, put it into a flask, stir, and react at 87°C for 18h; b. Polyacrylic acid PAA shell protection: Dissolve the dispersed FeOOH solution prepared in step a in water, stir for 5 min, add 80 mg / ml PAA and 1 ml ammonia water, stir for 5 min, and finally react in an oil bath at 60 °C for 24 h to obtain FeOOH-PAA NRs; c. Fe3O4 reduction FeOOH-PAA NRs were dissolved in diethylene glycol (DEG). DEG was added into a flask. The solution was heated to 220°C under nitrogen protection, and then the mixed solution was added and reacted for 8 hours to obtain the product.

6. A method for preparing the magnetoelectric coupling fiber according to any one of claims 2 to 5, characterized in that: It includes the following steps: a. Take a mixed solution of DMF / acetone (V:V=3:2), prepare a 16wt% PVDF-TrFE spinning solution, and stir for 15 minutes; b. Add rod-shaped ferroferric oxide Fe3O4 nanoparticles and ultrasonically disperse them for 30 minutes. Pour the mixed solution into a 10 ml syringe and perform electrospinning. The electrospinning parameters are: nozzle flow rate 1 ml / h, r (distance from needle tip to collection bucket) = 15 cm, V (voltage) = -2 ~ 13 kV, n (collection bucket speed) = 500, injection distance 5 cm; spinning time 2 hours, and put it in an oven for drying after the end.

7. A magnetic electromechanical support, characterized in that: It contains the magnetoelectric coupling fiber as described in any one of claims 2-5.

8. Application of the magneto-electromechanical stent according to claim 7 in sensors, energy harvesters or biomedical fields.

9. The use according to claim 8, characterized in that: The magneto-electromechanical stent is used for nerve repair and regeneration, muscle or bone tissue engineering, implantable or wearable biosensors, energy harvesting and self-driving devices, and intelligent response materials.

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