A self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film, a preparation method and application thereof

Abstract

The application discloses a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film and a preparation method and application thereof, belongs to the field of functional composite materials and wearable electronic technology, and aims at solving the technical problem that in the prior art, a single BT filler is introduced to optimize piezoelectric response, and the functional modification of the composite material in the biological activity is not considered in cooperation. The application provides a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film. The BT / HA composite material is synthesized through a solvothermal method, the composite material is doped into a PLA matrix, and a BT / HA / PLA piezoelectric nanocomposite film is successfully prepared through a spin coating process. The prepared BT / HA / PLA nanocomposite film has high piezoelectric performance, excellent flexibility and biocompatibility. The 5wt% BT / HA / PLA piezoelectric nanocomposite film has outstanding advantages. The application of the application to a sensor effectively overcomes the limitation of a traditional sensor in terms of wearability and application scenarios.

Description

Technical Field

[0001] This invention relates to the fields of functional composite materials and wearable electronics, specifically to a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film, its preparation method, and its application. Background Technology

[0002] With rapid economic development and a significant increase in public health awareness, portable wearable medical devices are showing broad application prospects in health monitoring, disease prevention, and early diagnosis. Flexible pressure sensors, as the core sensing element of such devices, can convert external mechanical stimuli into recognizable electrical signals. Based on their working mechanism, flexible pressure sensors are mainly divided into four types: resistive, capacitive, piezoelectric, and triboelectric. Among them, flexible piezoelectric sensors, with their inherent self-powered capability, rapid dynamic response characteristics, and excellent signal and noise suppression capabilities, have significant technological advantages in the fields of flexible electronics and implantable medical monitoring.

[0003] The piezoelectric effect, as a highly efficient mechanical-to-electrical energy conversion mechanism, can induce the directional alignment of dipoles within a material under stress, thereby generating polarized charges on the material surface. This allows the conversion of weak mechanical signals generated during human movement or physiological activities into electrical output. Based on this, flexible piezoelectric sensors possess irreplaceable application potential in real-time dynamic physiological signal monitoring.

[0004] Sensing materials are a key factor determining the overall performance of flexible sensors. While traditional polymer materials such as polyethylene (PE) possess characteristics such as non-toxicity and excellent chemical stability, their non-degradability conflicts significantly with current green, environmentally friendly, and sustainable development principles. Polylactic acid (PLA), as a widely available, highly processable, and fully biodegradable green polymer, has been widely applied in packaging, textiles, and medical fields. However, PLA-based materials still have significant limitations in biomedical applications: their inherent hydrophobic surface and lack of functional active groups result in poor cell adhesion, insufficient cell compatibility, and difficulty in effectively integrating with biological tissues, severely restricting their in-depth application in wearable medical device health monitoring.

[0005] To improve the piezoelectric response characteristics of PLA-based materials, researchers have attempted to introduce various functional piezoelectric fillers, such as reduced graphene oxide (rGO), zinc oxide (ZnO), carbon nanotubes (CNTs), and barium titanate (BT). Among them, barium titanate has attracted much attention due to its excellent piezoelectric properties. A study (Chemical Engineering Journal, 2025, 510, 161795) used electrospinning technology to prepare a composite electrospun film of poly(L-lactic acid) (PLLA) and tetragonal barium titanate (T-BTO), achieving a maximum open-circuit voltage of 1.03 V and a short-circuit current of 33.5 nA, significantly improving the piezoelectric output performance of PLA-based materials. Further research (Materials Chemistry Frontiers, 2023, 7, 3082-3092) successfully developed a BT / PLA composite nanogenerator using a spin-coating process, verifying the reinforcing effect of BT as a piezoelectric functional filler in the polymer matrix. However, the above studies all focused on optimizing the piezoelectric response by introducing a single BT filler, without taking into account the functional modification of the composite material in terms of bioactivity.

[0006] While existing BT / PLA composite materials possess improved piezoelectric properties, the lack of bioactive functions in both the PLA matrix and BT filler to actively induce cell adhesion and proliferation presents a technical bottleneck in their interfacial integration with biological tissues. This results in poor flexibility and biocompatibility of their pressure sensing materials, making it difficult to meet the application requirements of wearable medical devices. Therefore, how to maintain a good piezoelectric response in the BT / PLA system while endowing it with excellent flexibility and biocompatibility has become a key technical challenge that urgently needs to be overcome in this field.

[0007] To address the aforementioned technological gaps, there is an urgent need to develop a multifunctional composite material that combines high-voltage electrical response with excellent bioactivity to meet the dual application requirements of next-generation wearable medical devices in dynamic physiological signal monitoring and bio-tissue-friendly interaction. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a self-powered barium titanate / hydroxyapatite / polylactic acid (PLA) piezoelectric nanocomposite film, its preparation method, and its applications. This composite film, through the synergistic effect of BT and HA, simultaneously enhances the piezoelectric properties and biocompatibility of the PLA matrix, solving the problem of limited performance in single-filler composite films.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film, characterized in that the barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film comprises a polylactic acid matrix and a functional filler, wherein the functional filler is formed by a composite of barium titanate nanoparticles and hydroxyapatite nanorods, and the mass fraction of the functional filler is 1~9%.

[0010] Furthermore, the barium titanate nanoparticles are cubic perovskite crystals, the hydroxyapatite nanorods are hexagonal crystal structures, and the barium titanate nanoparticles are uniformly dispersed and attached to the hydroxyapatite nanorods.

[0011] Furthermore, a method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film is characterized by comprising the following steps: S1. Preparation of barium titanate nanoparticles Ba(OH)2 Barium titanate nanoparticles were prepared by a solvothermal method using 8H2O, TiO2, KOH solution and 5% PVA solution as raw materials. S2. Preparation of functional fillers With Ca(NO3)2 A mixed solution was prepared by mixing 4H2O, (NH4)2HPO4 and deionized water. Then, the barium titanate nanoparticles obtained in S1 were mixed with the mixed solution, and functional fillers were prepared by solvothermal method. S3. Preparation of barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin films Barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite films were prepared by spin coating using functional fillers prepared by S2 and polylactic acid as raw materials.

[0012] Furthermore, the specific process for preparing barium titanate nanoparticles in step S1 is as follows: S11, Weigh out Ba(OH)2 Add 8H2O, TiO2, KOH solution and 5% PVA solution to a reaction vessel and stir thoroughly to obtain a mixture; S12. Transfer the mixture to a homogeneous reactor for a solvothermal reaction; S13. The obtained product is washed and dried to obtain barium titanate nanoparticles.

[0013] Further, in step S11, the concentration of KOH solution is 0.2~5 mol / L, and Ba(OH)2... The molar ratio of 8H2O to TiO2 is (1.5~3):1; the volume of PVA solution used is 20~40mL; In step S12, the reaction temperature is 100~200℃ and the reaction time is 12~26h; In step S13, the obtained product is washed with ethanol and deionized water and dried at 60°C for 12 hours.

[0014] Furthermore, the specific process for preparing the functional filler in step S2 is as follows: S21. Weigh out Ca(NO3)2 4H2O and (NH4)2HPO4 were dissolved in 10 mL of deionized water to prepare solutions A and B, respectively. S22. Under thorough stirring, solution B is slowly added to solution A to obtain a mixed solution, and the pH of the mixed solution is adjusted to 10±0.5 with ammonia. S23. The barium titanate nanoparticles prepared in S1 are added to the mixed solution under continuous stirring, and a hydrothermal reaction is carried out. S24. The obtained product was washed with ethanol and deionized water and dried at 60°C for 12 hours to obtain the functional filler.

[0015] Furthermore, in step S21, Ca(NO3)2 The molar ratio of 4H2O to (NH4)2HPO4 is (1~2):1; in step S23, the stirring time is 0.5~2h, and the mass ratio of barium titanate nanoparticles to hydroxyapatite nanorods is (70~90):(30~10); the reaction is carried out at 100~200℃ for 12~26h.

[0016] Furthermore, the specific process for preparing the barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film in step S3 is as follows: S31. Under sealed conditions, polylactic acid is dissolved in CH2Cl2 and subjected to stirring and ultrasonic circulation at 0°C to obtain a polylactic acid solution. S32. Add functional filler to polylactic acid solution, and then stir and ultrasonically circulate the solution at 0°C to make the functional filler uniformly dispersed in the polylactic acid solution, so as to obtain barium titanate / hydroxyapatite / polylactic acid mixed solution. S33. A barium titanate / hydroxyapatite / polylactic acid mixed solution is spin-coated onto a circular substrate and dried to obtain a thin film. S34. The film is immersed in ethanol and peeled off to finally obtain a barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film based on polylactic acid matrix.

[0017] Further, in step S31, the amount of CH2Cl2 used is 10~25mL; in step S32, the mass of the controlled functional filler accounts for 1-9% of the mass of polylactic acid; in step S33, the barium titanate / hydroxyapatite / polylactic acid mixed solution is dried at 60℃ for 12h.

[0018] Furthermore, the self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film is applied in wearable health signal monitoring devices.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The hierarchical structure of the present invention, which first composites BT and HA and then composites PLA, can significantly suppress BT agglomeration, enhance the bonding of inorganic phase interfaces, and improve the interfacial compatibility between inorganic fillers and PLA compared with direct physical blending. It can also reduce defects and losses, and improve polarization efficiency and charge output, thereby greatly improving the piezoelectric properties, cycle stability and durability of BT / HA / PLA composite films, while also having good biocompatibility and biodegradability.

[0020] 2. This invention relates to a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film. By combining barium titanate / hydroxyapatite functional fillers with a polylactic acid matrix, it possesses both high-voltage piezoelectric properties and excellent flexibility and biocompatibility. Its flexibility and biocompatibility effectively overcome the limitations of traditional sensors in wearable devices and application scenarios, providing a more competitive technical solution for wearable health monitoring and intelligent human-computer interaction.

[0021] 3. Compared with similar products, the self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film developed in this invention can not only detect signal transmission during movement, but also detect sound transmission during speech. Combining excellent sensitivity, signal stability, and rapid response capability, the self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film of this invention can accurately detect weak physiological signals and dynamic motion responses.

[0022] 4. The self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film of this invention has a sensitive sensing response to various human movements, providing an effective strategy for the material design of self-powered flexible sensors and supporting their practical application in the field of health monitoring. Attached Figure Description

[0023] Figure 1 for Figure 1 SEM images, particle size distribution curves, EDS spectra, and elemental mappings of samples BT(af), HA(gl), and BT / HA(mr, sx) in Example 1; Figure 2 The XPS full spectrum (a) and detailed elemental spectra (bf), TEM images (h, k, n), HRTEM images (j, l, o), and SAED spectra (j, m, p) of samples BT, HA, and BT / HA in Example 1 are shown. Figure 3Optical photographs (af), SEM surface images (gl), SEM cross-sectional images (mr), and acid and alkali resistance photos (sx) of the PLA matrix in Comparative Example 1 and BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5. Figure 4 The graph (a) shows the TG variation trend of the PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5, and the dielectric constant ε. r Spectrum (b), dielectric loss tanδ spectrum (c), d 33 Value (d), Voc curve (e), Isc curve (f), cycle stability curve of BT / HA / PLA piezoelectric nanocomposite film with 5wt% BT / HA content (g), radar graph of piezoelectric properties of different nanocomposite films in Comparative Examples 1, 4, 9 and 3 (h), and comparison graph of piezoelectric properties of nanocomposite films prepared in Example 3 and existing literature (i). Figure 5 The graph shows the TG variation trend of BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6 (a) and the TG variation trend of HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 (b). Figure 6 To compare the d values ​​of BT / PLA nanocomposite films with different BT contents in Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Examples 7-11 33 value; Figure 7 To compare the ε of BT / PLA nanocomposite films with different BT contents in Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Examples 7-11 r And tanδ variation graph; Figure 8 The diagrams show the open-circuit voltage (Voc) and short-circuit current (Isc) of BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6 (a) and (b) respectively, and the open-circuit voltage (Voc) and short-circuit current (Isc) of HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 (c) and (d) respectively. Figure 9 The Voc response curves of the 5wt% BT / HA / PLA piezoelectric nanocomposite film in Example 3 during different human activity monitoring: clapping (a), speaking (b), elbow bending (c), wrist bending (d), finger tapping (e), walking (f), knee bending (g), and running (h). Figure 10The potential simulation diagram (ad), stress simulation diagram (eh), and electric field distribution simulation diagram (il) of different nanofilms in Comparative Example 1, Comparative Example 4, Comparative Example 9, and Example 3 are shown. Figure 11 Fluorescence staining images of cell viability / necrosis of different nanocomposite films in Comparative Examples 1, 4, 9 and 3: live cells (ad), necrotic cells (eh), and live-dead cell fusion image (il). Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that, unless otherwise specified, the chemicals, reagents, or solvents used in the following examples are all commercially available products commonly used in the field. Unless otherwise specified, the operating methods or conditions used in the following examples are all conventional operating methods or conditions. For example, unless otherwise specified, the temperature is room temperature and the pressure is atmospheric pressure.

[0026] In the embodiments, comparative examples and experimental sections of this invention, PLA is used to replace polylactic acid, BT is used to replace barium titanate nanoparticles, HA is used to replace hydroxyapatite nanorod composites, BT / HA is used to replace functional fillers, and BT / HA / PLA is used to replace barium titanate / hydroxyapatite / polylactic acid.

[0027] Example 1 The method for preparing barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin films provided in this embodiment includes the following steps: S1, Preparation of BT Weigh out 8.69g of Ba(OH)2 8H₂O, 0.88g TiO₂, and 3.36g 2mol / L KOH solution were added to the reaction vessel, and the Ba(OH)₂ was controlled. The molar ratio of 8H2O to TiO2 is 2.5:1; then 30 mL of 5% PVA solution is added and stirred thoroughly to obtain a mixed solution. The mixed solution is transferred to a homogeneous reactor and reacted at 200 °C for 26 h. After the reaction is completed, the product is washed with ethanol and deionized water until neutral and dried at 60 °C for 12 h to obtain barium titanate nanoparticles, i.e., BT.

[0028] S2. Preparation of functional fillers Weigh out 3.94g of Ca(NO3)2 4H₂O and 1.32g(NH₄)₂HPO₄ were dissolved in 10mL of deionized water, respectively, to control the Ca(NO₃)₂ The molar ratio of 4H2O and 1.32g(NH4)2HPO4 was 1.67:1, yielding Ca(NO3)2 solution and (NH4)2HPO4 solution, denoted as solution A and solution B, respectively. Under stirring conditions, solution B was slowly added dropwise to solution A to obtain a mixed solution. The pH of the mixed solution was adjusted to 10±0.5 with ammonia. BT prepared by S1 was added to the mixed solution, and stirring was continued for 30 min. The mixed solution was then transferred to a hydrothermal reactor and reacted at 150℃ for 18 h. After the reaction was completed, the product was washed with ethanol and deionized water until neutral and dried at 60℃ for 12 h to obtain the functional filler, namely BT / HA, where the mass ratio of BT to HA was 80:20.

[0029] S3. Preparation of BT / HA / PLA piezoelectric nanocomposite thin films 4.6 g of PLA was weighed and added to 20 mL of CH2Cl2. Under sealed conditions, the mixture was stirred and ultrasonically circulated at 0 °C to obtain a homogeneous PLA solution. BT / HA prepared by S2 was added to the PLA solution, with the mass of the functional filler BT / HA controlled to be 1% of the mass of PLA. The mixture was also stirred and ultrasonically circulated at 0 °C to uniformly disperse BT / HA in the PLA solution, resulting in a BT / HA / PLA mixed solution. The mixed solution was spin-coated onto a circular substrate and dried at 60 °C for 12 h. The dried film was then immersed in ethanol for peeling to obtain a BT / HA / PLA piezoelectric nanocomposite film based on a PLA matrix.

[0030] Example 2 The preparation steps of the BT / HA / PLA piezoelectric nanocomposite film provided in this embodiment differ from those in Example 1 only in step S3. The difference between S3 and Example 1 is as follows: In this embodiment, the mass of BT / HA in the BT / HA / PLA piezoelectric nanocomposite film accounts for 3% of the mass of PLA.

[0031] Example 3 The preparation steps of the BT / HA / PLA piezoelectric nanocomposite film provided in this embodiment differ from those in Example 1 only in step S3. The difference between S3 and Example 1 is as follows: In this embodiment, the mass of BT / HA in the BT / HA / PLA piezoelectric nanocomposite film accounts for 5% of the mass of PLA.

[0032] Example 4 The preparation steps of the BT / HA / PLA piezoelectric nanocomposite film provided in this embodiment differ from those in Example 1 only in step S3. The difference between S3 and Example 1 is as follows: In this embodiment, the mass of BT / HA in the BT / HA / PLA piezoelectric nanocomposite film accounts for 7% of the mass of PLA.

[0033] Example 5 The preparation steps of the BT / HA / PLA piezoelectric nanocomposite film provided in this embodiment differ from those in Example 1 only in step S3. The difference between S3 and Example 1 is as follows: In this embodiment, the mass of BT / HA in the BT / HA / PLA piezoelectric nanocomposite film accounts for 9% of the mass of PLA.

[0034] This invention also prepared BT / HA / PLA piezoelectric nanocomposite films based on BT / HA mass fractions within the range of 1-9%, with other BT / HA mass fractions such as 2%, 4%, 6% and 8% corresponding to different experimental conditions. The values ​​of each experimental condition can also be adjusted according to different BT / HA mass fractions in actual situations.

[0035] Table 1. Preparation of BT / HA / PLA piezoelectric nanocomposite films in Examples 6-9 This invention uses the BT / HA / PLA piezoelectric nanocomposite films prepared in Examples 1-5 for performance verification experiments. To demonstrate the technical advantages of the BT / HA / PLA piezoelectric nanocomposite films of this invention, their physicochemical properties were also experimentally verified using the following comparative examples, the details of which are as follows: Comparative Example 1 Weigh 4.6g PLA and add it to 20mL CH2Cl2. Under sealed conditions, stir and sonicate at 0℃ to obtain a uniform PLA solution. Spin-coat the PLA solution onto a circular substrate and dry it at 60℃ for 12h. Immerse the dried film in ethanol to peel it off and obtain the PLA substrate.

[0036] Comparative Example 2 4.6 g of PLA was weighed and added to 20 mL of CH2Cl2. Under sealed conditions, the mixture was stirred and ultrasonically circulated at 0 °C to obtain a homogeneous PLA solution. BT was added to the PLA solution, with the mass of BT controlled to be 1% of the mass of PLA. The mixture was also stirred and ultrasonically circulated at 0 °C to ensure that BT was uniformly dispersed in the PLA solution, resulting in a BT / PLA mixed solution. The mixed solution was spin-coated onto a circular substrate and dried at 60 °C for 12 h. The dried film was then immersed in ethanol for peeling to obtain a BT / PLA nanocomposite film based on a PLA substrate.

[0037] Comparative Example 3 The only difference between this comparative example and Comparative Example 2 is that the quality of BT is controlled to account for 3% of the quality of PLA.

[0038] Comparative Example 4 The only difference between this comparative example and Comparative Example 2 is that the quality of BT is controlled to account for 5% of the quality of PLA.

[0039] Comparative Example 5 The only difference between this comparative example and Comparative Example 2 is that the quality of BT is controlled to account for 7% of the quality of PLA.

[0040] Comparative Example 6 The only difference between this comparative example and Comparative Example 2 is that the quality of BT is controlled to account for 9% of the quality of PLA.

[0041] Comparative Example 7 Weigh 4.6g PLA and add it to 20mL CH2Cl2. Under sealed conditions, stir and sonicate at 0℃ to obtain a homogeneous PLA solution. Add HA to the PLA solution, controlling the mass of HA to be 1% of the mass of PLA. Similarly, stir and sonicate at 0℃ to uniformly disperse HA in the PLA solution to obtain an HA / PLA mixed solution. Spin-coat the mixed solution onto a circular substrate and dry at 60℃ for 12h. Immerse the dried film in ethanol for peeling to obtain an HA / PLA nanocomposite film.

[0042] Comparative Example 8 The only difference between this comparative example and comparative example 7 is that the quality of HA is controlled to be 3% of the quality of PLA.

[0043] Comparative Example 9 The only difference between this comparative example and comparative example 7 is that the quality of HA is controlled to be 5% of the quality of PLA.

[0044] Comparative Example 10 The only difference between this comparative example and comparative example 7 is that the quality of HA is controlled to account for 7% of the quality of PLA.

[0045] Comparative Example 11 The only difference between this comparative example and comparative example 7 is that the quality of HA is controlled to account for 9% of the quality of PLA.

[0046] Experiment 1 The BT, HA, and BT / HA samples prepared in Example 1 were adhered to the sample stage using conductive tape. The microstructure, particle size, and elemental composition of the samples were characterized using field emission scanning electron microscopy (SEM, Quanta FEG 250, USA) and EDS. The results are as follows: Figure 1 As shown. Figure 1 The images show the SEM images, particle size distribution curves, EDS spectra, and elemental mappings of samples BT(af), HA(gl), and BT / HA(mr, sx) in Example 1.

[0047] pass Figure 1 It can be seen that: Figure 1 As shown in ab, the SEM image of BT prepared under the experimental conditions of Example 1 shows that it has a spherical morphology with an average particle size of 71.2 nm; Figure 1 As shown in cf, the elemental mappings plot shows that Ba, Ti, and O elements are evenly distributed, consistent with the theoretical elemental proportions. Figure 1 As shown in gh, the SEM image of HA under the experimental conditions of Example 1 shows that it has a one-dimensional rod-like morphology with an average particle size of 78.5 nm; Figure 1 As shown in Figure 1, the EDS and elemental mappings plots show that P, Ca, and O elements are evenly distributed, consistent with the theoretical elemental proportions. Figure 1 As shown in m and s, the SEM and TEM images of BT / HA show that spherical BTs are uniformly dispersed and attached to the sheet-like HA; as Figure 1 As shown in nr and tx, the elemental mappings show that O, Ba, Ti, P, and Ca are uniformly distributed throughout the sample.

[0048] Experiment 2 The BT, HA, and BT / HA samples prepared in Example 1 were adhered to the sample stage using conductive tape, and their surface chemical composition was determined using X-ray photoelectron spectroscopy (XPS, AXIS ULTRADLD, UK). The BT, HA, and BT / HA samples prepared in Example 1 were dispersed in ethanol, diluted, and a small amount of liquid was added dropwise onto a copper grid using a pipette, then allowed to dry for approximately 1 hour. The surface morphology of the samples was observed using field emission transmission electron microscopy (TEM, JEM-2100F, Japan). The microstructure of the nanomaterials was characterized using high-resolution transmission electron microscopy (HRTEM). Structural analysis of the atomic arrangement of the nanomaterials was performed using selected area electron diffraction (SAED), and the results are as follows: Figure 2 As shown.

[0049] Figure 2 The images show the XPS full spectrum (a) and detailed elemental spectra (bf), TEM images (h, k, n), HRTEM images (j, l, o), and SAED spectra (j, m, p) of samples BT, HA, and BT / HA in Example 1. Figure 2 As shown in di, the elemental composition and chemical valence state of the material were further determined by XPS testing. Figure 2 XPS full spectrum analysis of BT / HA showed that it mainly contains O 1s, Ba 3d, Ti 2p, Ca 2p, and P 2p elements, preliminarily confirming the formation of a BT / HA functional filler composite. Figure 2As shown in cf, the detailed spectral analysis of each element shows that: the O 1s spectrum of BT has three peaks, which, in order of increasing binding energy, correspond to lattice oxygen, oxygen vacancies, and surface adsorbed oxygen in BT, respectively. The lattice oxygen peak at 529 eV originates from the Ti-O bond in the BT lattice, the peak at 531 eV can be attributed to oxygen vacancies in BT, and the peak at 533 eV corresponds to surface adsorbed oxygen in BT, which comes from the -OH group in PVA; in the O 1s spectrum of HA, the lattice oxygen at 530 eV originates from PO4³⁺. - The peak at 531 eV is attributed to oxygen vacancies in HA, and the peak at 532 eV corresponds to surface-adsorbed oxygen in HA, which originates from the -OH group in HA. Figure 2 As shown in Figure d, the fine spectrum of Ba 3d exhibits two doublets at 778 eV and 793 eV, corresponding to the spin orbitals of Ba 3d5 / 2 and Ba 3d3 / 2, respectively. Peak fitting also identified two sets of Ba 3d peaks, which may originate from Ba² in two different chemical environments. + .like Figure 2 As shown in Figure c, the peaks at 458 eV and 464 eV in the Ti 2p fine structure spectrum correspond to the Ti 2p3 / 2 and Ti 2p1 / 2 spin orbitals, indicating the presence of Ti in BT. 4+ .like Figure 2 As shown in e, the peaks at 347 eV and 350 eV in the Ca2p fine spectrum correspond to the Ca 2p3 / 2 and Ca 2p1 / 2 spin orbitals, indicating the presence of Ca²⁺ in HA. + .like Figure 2 As shown in f, in the fine spectrum of P 2p, the two doublets at 133 eV and 134 eV correspond to the P 2p3 / 2 and P 2p1 / 2 spin orbitals, respectively, indicating the presence of P in HA. 5+ Comparative analysis revealed that the peak of BT / HA shifted to the left compared to BT and HA, indicating that the binding energy of the composite peak of the BT / HA functional filler increased, meaning that BT / HA is firmly bonded.

[0050] like Figure 2 As shown in the figure, the microstructures of BT, HA, and BT / HA were characterized by TEM, HRTEM, and SAED. Figure 2 TEM images of h and k show that BT consists of spherical nanoparticles and HA consists of rod-shaped particles; corresponding to Figure 2 The HRTEM images of i and l show that BT and HA have clear lattice fringes. The lattice fringes spacing of 2.85 Å corresponds to the (110) crystal plane of BT, and the lattice fringes spacings of 4.4 Å and 3.0 Å correspond to the (110) and (002) crystal planes of HA, respectively. Figure 2 SAED spectra of j and m show the reciprocal lattice points corresponding to the (220) and (200) crystal planes of BT and the (111) and (101) crystal planes of HA. Figure 2 In the HRTEM image of BT / HA, the 2.85 Å lattice stripe is attributed to the (110) crystal plane of BT, and the 2.81 Å lattice stripe corresponds to the (211) crystal plane of HA. Figure 2 The SAED spectrum of p shows the reciprocal lattice points corresponding to the (110) and (200) crystal planes of BT and the (203) crystal plane of HA, further confirming the successful synthesis of the BT / HA functional filler.

[0051] Experiment 3 (1) The PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5 were cut into squares with a size of 5*5cm and placed on colored cardstock to study their transparency.

[0052] (2) The PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite film samples with different BT / HA contents prepared in Examples 1-5 were attached to the sample stage with conductive tape and the surface morphology and cross-section of the samples were observed by field emission scanning electron microscope (SEM, QuantaFEG 250, USA).

[0053] (3) The PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5 were immersed in 1 mol / L HCl and 0.5 mol / L NaOH solutions for 48 h and photographed to study their acid and alkali resistance.

[0054] Figure 3 Optical photographs (af), SEM surface images (gl), SEM cross-sectional images (mr), and acid and alkali resistance photos (sx) of the PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5.

[0055] Figure 3 af are optical photographs of the PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5. It can be seen that the PLA matrix has good transparency, and the transparency gradually decreases with the increase of BT / HA content, and some agglomeration occurs on the surface. Figure 3 Image gl shows SEM images of the PLA matrix in Comparative Example 1 and the surfaces of BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5. As the BT / HA content in the PLA matrix increases, aggregation gradually occurs. Figure 3As shown in the MR diagram, the cross-section of the BT / HA / PLA piezoelectric nanocomposite film was observed. Within the film thickness range of 20~30μm, as the BT / HA content increased, its dispersion in the PLA matrix became increasingly uneven, and the agglomeration phenomenon intensified, which had an adverse effect on the electrical properties of the film. When the BT / HA content was 5wt%, the cross-section of the BT / HA / PLA piezoelectric nanocomposite film showed higher density and uniformity.

[0056] like Figure 3 As shown in Figure sx, the PLA matrix from Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents from Examples 1-5 were immersed in 1 mol / L HCl and 0.5 mol / L NaOH solutions. It can be seen that the film did not dissolve after immersion in HCl solution for 48 hours, while significant dissolution occurred after immersion in NaOH solution for 24 hours. However, with increasing BT / HA content, the integrity of the film under alkaline conditions gradually improved. Therefore, the incorporation of BT / HA effectively hinders the penetration of solution into the film interior, enhancing its acid and alkali resistance. This may be because BT / HA forms a physical barrier in the PLA matrix, delaying the contact and reaction between acid / alkali solutions and the PLA matrix molecular chains.

[0057] Experiments 1-3 demonstrate that the functional filler composites formed by BT and HA are uniform, as are the BT / HA / PLA piezoelectric nanocomposite films formed by combining BT and HA functional fillers with PLA. Furthermore, with increasing BT / HA content, the BT / HA / PLA piezoelectric nanocomposite films exhibit greater acid and alkali resistance; however, with increasing BT / HA content, agglomeration gradually occurs within the PLA matrix. When the BT / HA content is 5 wt%, the cross-section shows that the BT / HA / PLA piezoelectric nanocomposite films exhibit relatively higher density and uniformity.

[0058] Experiment 4 (1) The thermal stability of the PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite film samples with different BT / HA contents in Examples 1-5, the BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6, and the HA / PLA nanocomposite film samples with different HA contents in Comparative Examples 7-11 were tested in a nitrogen atmosphere and within a temperature range of 0-800℃ using a synchronous thermal analyzer (TG, STA 449F3, Germany).

[0059] (2) Using a dielectric spectrometer (FDS, Novo control concept 80, Germany) at 10 0 Hz to 10 6The dielectric constant and dielectric loss trends of PLA substrate in Comparative Example 1 and BT / HA / PLA nanocomposite films with different BT / HA contents in Examples 1-5, BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6, and HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 were examined within the Hz frequency range.

[0060] (3) A precision piezoelectric coefficient tester (d) is used. 33 (ZJ-4AN, Chinese Academy of Sciences) The piezoelectric constant d of BT / HA / PLA nanocomposite film samples with different BT / HA contents in Comparative Examples 1 and 1-5, BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6, and HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 were measured. 33 (0.25N, 110Hz).

[0061] (4) The open-circuit voltage (Voc), short-circuit current (Isc), cycle stability, and health monitoring performance of the PLA substrate in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite film samples with different BT / HA contents in Examples 1-5 were measured using a mixed-signal oscilloscope (RIGOL MSO5354 series). The test procedure was as follows: copper (Cu) electrodes were used to establish electrical contact on both sides of the BT / HA / PLA piezoelectric nanocomposite film, and then polyimide (PI) tape was used for protection. The encapsulated film can be used for health monitoring. When subjected to external mechanical stimulation, a corresponding electrical signal is generated through the electrode circuit.

[0062] Figure 4 The graph (a) shows the TG variation trend of the PLA matrix in Comparative Example 1 and the BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents in Examples 1-5, and the dielectric constant ε. r Spectrum (b), dielectric loss tanδ spectrum (c), d 33 Value (d), Voc curve (e), Isc curve (f), cycle stability curve of BT / HA / PLA piezoelectric nanocomposite film with 5wt% BT / HA content (g), radar graph of piezoelectric properties of different nanocomposite films in Comparative Examples 1, 4, 9 and 3 (h), and comparison graph of piezoelectric properties of nanocomposite films prepared in Example 3 and existing literature (i). Figure 5 The graph shows the TG variation trend of BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6 (a) and the TG variation trend of HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 (b). Figure 6To compare the d values ​​of BT / PLA nanocomposite films with different BT contents in Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Examples 7-11 33 value; Figure 7 To compare the ε of BT / PLA nanocomposite films with different BT contents in Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Examples 7-11 r And tanδ variation graph.

[0063] Figure a shows the thermogravimetric analysis (TGA) curves of BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents. The thermal decomposition process of the BT / HA / PLA piezoelectric nanocomposite films can be divided into three distinct stages: the first stage is from 30 to 150 °C, where weight loss may be attributed to the evaporation of water molecules in the sample; the second stage is from 150 to 250 °C, where weight loss mainly originates from the degradation and carbonization of the PLA polymer matrix; and the third stage is from 250 to 800 °C, where significant weight loss is attributed to the breakage of molecular chains in the PLA matrix. Notably, with increasing BT / HA content, the degradation rate of the PLA matrix gradually decreases, with the maximum thermal decomposition temperature (Tmax) of the pure PLA matrix being 310 °C. With increasing BT / HA content, the thermal decomposition temperature of the nanocomposite film gradually increases, reaching 325 °C when the BT / HA content is 9 wt%. This enhancement may be due to the stronger hydrogen bond interaction between oxygen atoms on the surface of the nanocomposite film and hydroxyl groups in the PLA matrix molecules at higher BT / HA contents, thereby increasing the maximum thermal decomposition temperature.

[0064] Figure 5 The thermogravimetric trends of BT / PLA nanocomposite films with different BT contents and HA / PLA nanocomposite films with different HA contents are shown in Comparative Examples 2-11. Figure 4 The experimental results shown in a are consistent, therefore it can be concluded that the incorporation of BT or HA enhances the thermal stability of the PLA matrix.

[0065] like Figure 4 bc. Evaluate the frequency-dependent dielectric constant (ε) of BT / HA / PLA nanocomposite films with different BT / HA contents. r ) and dielectric loss tangent (tanδ). For example Figure 4 As shown in b, ε r The curve at 10 0 A slight fluctuation occurs at ~10²Hz, possibly due to instability during the initial startup of the instrument; within 10²~10... 6 In the Hz range, the ε of the nanocomposite thin film r The relatively stable dielectric properties indicate stable dielectric properties over a wide frequency range. The ε0 of pure PLA film...r The ε value is 0.42. As the BT / HA content increases, the ε value of the BT / HA / PLA piezoelectric nanocomposite film also increases. r ε first increases and then decreases at 5wt% BT / HA content. r The maximum value of 1.40 is achieved, and this enhancement is attributed to the synergistic effect of the high intrinsic dielectric properties of BT / HA at low filler contents and the polarization of the functional filler-matrix interface; however, at higher contents, filler agglomeration leads to reduced interfacial compatibility and the formation of defect regions, weakening the polarization contribution. Figure 4 As shown by the tanδ curve of c, the dielectric loss tangent of the BT / HA / PLA piezoelectric nanocomposite film increases with increasing frequency. The tanδ of pure PLA is 0.081. With increasing BT / HA content, tanδ first decreases and then increases, reaching a minimum of 0.008 at 5wt% BT / HA content. In the BT / HA / PLA piezoelectric nanocomposite film, the local dipole effect at the interface of BT, HA, and PLA enhances tanδ. Specifically, the local electric field generated at the interface between the BT / HA nanomaterial and PLA induces dipole polarization, leading to a further increase in tanδ.

[0066] like Figure 4 As shown in Figure ef, the open-circuit voltage (Voc) and short-circuit current (Isc) were measured under conditions of 20 N and 1 Hz to investigate the effect of introducing different contents of BT / HA nanomaterials on the piezoelectric properties of the nanocomposite film. When mechanical pressure is applied to the nanocomposite film, the piezoelectric potential generated by BT / HA and PLA causes charge to flow in the external circuit between the upper and lower electrodes, forming a positive peak; subsequently, when the applied pressure is released, the charge flows in the reverse direction, forming a negative peak. Figure 4 As shown in Figure e, the peak Voc of pure PLA is 3.85V. With increasing BT / HA content, Voc first increases and then decreases. When the BT / HA content is 5wt%, the Voc of the BT / HA / PLA piezoelectric nanocomposite film reaches its maximum value of 8.56V, indicating that the introduction of BT / HA effectively regulates the voltage output of the PLA matrix. Figure 4 As shown in f, the peak Isc value of the pure PLA matrix is ​​98 nA. When the BT / HA content is 5 wt%, the peak Isc value of the BT / HA / PLA piezoelectric nanocomposite film reaches 185 nA, consistent with the Voc trend. This change may be attributed to the introduction of BT / HA promoting the dipole motion of PLA, thereby increasing the dipole moment of the composite material and enhancing the piezoelectric properties; the 5 wt% BT / HA / PLA piezoelectric nanocomposite film exhibits the best synergistic effect; however, increasing the filler concentration leads to intrafilm agglomeration, increasing the film hardness, reducing the piezoelectric deformation under the same pressure, thus limiting the dipole motion of PLA, weakening the polarization inside the nanocomposite film, and ultimately reducing the piezoelectric properties. Figure 4As shown in g, the 5wt% BT / HA / PLA piezoelectric nanocomposite film underwent a 3000-second cyclic voltage stability test at 20N and 1Hz. The film exhibited highly stable and durable voltage output during multiple cycles, and no significant degradation occurred in the internal structure or interface contact. This indicates that the charge generation and transfer mechanism during the force-to-electric conversion process is stable and controllable, enabling continuous and stable electrical signal output.

[0067] like Figure 4 As shown in d, the piezoelectric constants (d) of BT / HA / PLA piezoelectric nanocomposite films with different BT / HA contents were determined. 33 Measurement, d of pure PLA 33 The ratio is 0.6 pC / N. As the BT / HA content increases, d 33 The value first increases and then decreases. When the BT / HA content is 5wt%, the d of the BT / HA / PLA piezoelectric nanocomposite film... 33 The maximum value of 2.9 pC / N indicates that the incorporation of BT / HA effectively modulates the piezoelectric properties of the nanocomposite film. Appropriate amounts of BT / HA enhance the piezoelectric properties, while excessive filler leads to agglomeration and reduces performance.

[0068] like Figure 6 As shown, when different amounts of BT and HA are introduced into the PLA matrix, when the BT or HA content is 5wt%, the d of the BT / PLA or HA / PLA nanocomposite film is... 33 The value is the largest.

[0069] Since the content ratio of BT to HA in the 5wt% BT / HA / PLA piezoelectric nanocomposite film of this invention is 80:20, the BT mass fraction in the 5wt% BT / HA / PLA film is 4%. Compared with the 5wt% BT / PLA nanocomposite film, the piezoelectric properties (i.e., those quantified by parameters Voc, Isc, and d) are significantly improved. 33 The slightly lower indicator value is directly proportional to the BT content and falls within the normal range, which is understandable.

[0070] like Figure 4 As shown in h, the piezoelectric properties of PLA-based nanocomposite films with different functional fillers are compared using radar charts. Notably, the 5wt% BT / HA / PLA piezoelectric nanocomposite film exhibits outstanding advantages in key piezoelectric output parameters (d). 33 Voc, Isc) and dielectric constant (ε) r It is significantly superior to the 5wt%HA / PLA and pure PLA systems in terms of performance, while maintaining a low loss tangent (tanδ). Compared with pure PLA film, it has achieved a leap in comprehensive performance and provides a technical reference for the design of flexible piezoelectric materials. Figure 7The ε values ​​of BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 are shown. r From the tanδ value, it can be seen that when the content of functional filler in the nanocomposite film reaches 5wt%, ε r Both tanδ and tanδ reach their optimal values.

[0071] like Figure 4 This paper summarizes the Voc and Isc data of the BT / HA / PLA piezoelectric nanocomposite film developed in this invention and compares them with results from representative literature. A comprehensive review of existing literature on the application of PLA-based nanocomposite films in sensors ensures data comparability. Among these systems, the BT / HA / PLA piezoelectric nanocomposite film developed in this invention achieves the highest Voc and ranks third in Isc, exhibiting superior piezoelectric performance compared to most previously reported PLA-based nanocomposite films. With these excellent piezoelectric output characteristics, the BT / HA / PLA piezoelectric nanocomposite film has great application potential in next-generation wearable health monitoring devices.

[0072] Experiment 5 The open-circuit voltage (Voc), short-circuit current (Isc), cycle stability, and health monitoring performance of BT / PLA nanocomposite films with different BT contents in Comparative Examples 2-6 and HA / PLA nanocomposite films with different HA contents in Comparative Examples 7-11 were measured using a mixed-signal oscilloscope (RIGOL MSO5354 series). The testing procedure involved establishing electrical contacts on both sides of the BT / HA / PLA nanocomposite film using copper (Cu) electrodes, followed by encapsulation and protection with polyimide (PI) tape. The encapsulated film can be used for health monitoring; when subjected to external mechanical stimulation, a corresponding electrical signal is generated through the electrode circuit.

[0073] Figure 8 The graphs show the open-circuit voltage (Voc) and short-circuit current (Isc) of BT / PLA nanocomposite films with different BT contents in Examples 2-6 (a) and HA / PLA nanocomposite films with different HA contents in Examples 7-11 (c) and (d). It can be seen that with the increase of BT or HA content, the open-circuit voltage (Voc) and short-circuit current (Isc) of the BT / PLA or HA / PLA nanocomposite films first increase and then decrease, with the highest values ​​for 5wt% BT / PLA and 5wt% HA / PLA nanocomposite films. This indicates that when the BT or HA addition is 5wt%, the piezoelectric performance of the BT / PLA or HA / PLA nanocomposite films is improved the best.

[0074] Experiment 6 A mixed-signal oscilloscope (RIGOL MSO5354 series) was used to measure the health monitoring sensor response of a 5wt% BT / HA / PLA piezoelectric nanocomposite film under different movement states in different parts of the human body (clapping, speaking, elbow bending, wrist bending, finger tapping, walking, knee bending, and running). The testing process involved establishing electrical contact on both sides of the BT / HA / PLA nanocomposite film using copper (Cu) electrodes, followed by encapsulation and protection with polyimide (PI) tape. The encapsulated film can be used for health monitoring; when subjected to external mechanical stimulation, it generates corresponding electrical signals through the electrode circuit, enabling real-time monitoring of physiological activities.

[0075] Figure 9 The Voc response curves of the 5wt% BT / HA / PLA piezoelectric nanocomposite film in Example 3 during different human activity monitoring activities are as follows: clapping (a), speaking (b), elbow flexion (c), wrist flexion (d), finger tapping (e), walking (f), knee flexion (g), and running (h). Hand movements: clapping ( Figure 9 a) and finger tapping ( Figure 9 The Voc characteristics of e) closely correspond to the rhythm of movement. The interval between voltage peaks during clapping matches the clapping frequency. Each tap with the fingers produces a sharp voltage peak, and the peak amplitude is related to the tapping force, indicating that the thin film can sensitively capture different hand movements and detect subtle changes in applied force. Joint and muscle movements: speaking ( Figure 9 b) Elbow flexion ( Figure 9 c) Wrist flexion ( Figure 9 d) and knee bend ( Figure 9 The Voc responses of g) all exhibit regular, patterned signals. Vocal cord vibration generates pulsed voltage changes, which can effectively detect laryngeal muscle activity. When the joint flexes, the voltage fluctuates periodically with the movement, and the peak amplitude is related to the angle and velocity, allowing the surface membrane to accurately reflect the joint state. Limb movement: Walking ( Figure 9 f) and running ( Figure 9 h) Stable and strong periodic voltage fluctuations were generated, respectively, reflecting the differences in mechanical vibrations related to motion intensity, indicating that the membrane can distinguish motion intensity. In summary, the 5wt% BT / HA / PLA piezoelectric nanocomposite film can effectively convert the mechanical vibrations generated by various human movements.

[0076] Experiment 7 Finite element method (FEM) simulations were performed using the multiphysics coupled simulation software COMSOL to analyze the piezoelectric nanocomposite films of PLA matrix in Comparative Example 1, 5wt% BT / PLA in Comparative Example 4, 5wt% HA / PLA in Comparative Example 9, and 5wt% BT / HA / PLA in Example 3. The effects of different functional fillers on the piezoelectric properties, mechanical characteristics, and electric field distribution of the PLA matrix nanocomposite films were investigated. The steady-state calculation process used the following equations: , .in, D Represents the electric displacement vector. e Represents the coupling matrix. S Indicates strain, Represents the dielectric matrix. E Represents the electric field intensity vector. T Indicates stress, The matrix represents the elasticity matrix. Based on the piezoelectric effect mechanism, applying pressure to the surface of nanocomposite thin film materials can induce internal polarization and generate an electric potential. Therefore, the potential amplitude generated by the material under pressure can be used as a key quantitative indicator for evaluating the piezoelectric properties of the material.

[0077] Figure 10 The following are simulated potential (ad), stress (eh), and electric field distribution (il) diagrams for different nanofilms in Comparative Examples 1, 4, 9, and 3. Figure 10 As shown in the diagram, the surface potential distribution of pure PLA is non-uniform, with high-potential and low-potential regions interspersed, and the maximum potential is 11.2 V. The surface potential of the 5 wt% HA / PLA nanocomposite film is enhanced compared to pure PLA, which is attributed to the excellent dispersion of HA particles in the PLA matrix, uniformly enhancing the piezoelectric effect. In contrast, the 5 wt% BT / HA / PLA piezoelectric nanocomposite film exhibits a more uniform and stable potential distribution, with the maximum potential increasing to 28.0 V, indicating that the synergistic effect between BT and HA fillers jointly optimizes the piezoelectric properties of the film. Figure 10 As shown in the figure, regarding stress distribution, pure PLA exhibits significant stress fluctuations accompanied by localized stress concentrations, with peak stress reaching as high as 1.1 × 10⁻⁶. 5 MPa; After introducing HA as a reinforcing phase, the stress distribution of the 5wt% HA / PLA nanocomposite film was improved; The stress distribution of the 5wt% BT / HA / PLA piezoelectric nanocomposite film was more uniform, and the maximum stress increased to 6.7×10 MPa. 5 MPa. For example... Figure 10As shown in Figure 1, the electric field distribution simulation reveals that the electric field distribution of pure PLA is non-uniform, exhibiting alternating regions of high and low intensity. This pattern may induce local breakdown under an external electric field. In contrast, the electric field distribution uniformity of the 5wt% HA / PLA nanocomposite film is improved, indicating that the uniform dispersion of HA effectively suppresses charge accumulation and local electric field concentration, thereby significantly enhancing the overall uniformity of the electric field. Notably, the 5wt% BT / HA / PLA piezoelectric nanocomposite film exhibits the most uniform electric field distribution, suggesting that the synergistic effect between BT and HA effectively modulates the electric field within the composite film, thus enhancing the stability of its piezoelectric properties. In summary, the 5wt% BT / HA / PLA piezoelectric nanocomposite film demonstrates excellent performance in terms of potential, stress, and electric field distribution. The simulation results are consistent with experimental data, providing important theoretical and experimental support for the application of PLA-based nanocomposite films in piezoelectric sensing, intelligent actuation, and related fields.

[0078] Experiment 8 The effects of different nanocomposite films on the viability of mouse embryonic osteoblast precursor cells were evaluated using live / dead fluorescence staining. Nanocomposite film samples from Comparative Examples 1, 4, 9, and 3 were sterilized, seeded into cells, and cultured for a set time. Calcein was used to analyze the staining. Cells were stained using AM / PI dual fluorescence staining and incubated at 37°C in the dark. Images of green fluorescence in live cells and red fluorescence in dead cells were acquired using a laser confocal microscope. The dual-channel images were then superimposed to obtain a fused image of live and dead cells, thus providing a direct representation of the effects of different nanofilms on cell viability. Figure 11 Fluorescence staining images of cell viability / necrosis of different nanocomposite films in Comparative Examples 1, 4, 9 and 3: live cells (ad), necrotic cells (eh), and live-dead cell fusion image (il).

[0079] like Figure 11 As shown, the effects of different nanocomposite films on the viability of mouse embryonic osteoblast precursor cells were evaluated by live / dead fluorescence staining. Figure 11 The image above shows the fluorescence of live cells. Green fluorescence indicates live cells. A large number of green fluorescent live cells appeared on the surfaces of all four types of films. The cells were morphologically intact and well spread, indicating that they provided different degrees of support for cell survival. Figure 11 The images show fluorescence of necrotic cells, with red fluorescence indicating necrotic cells. These images show that only a small number of red fluorescent dead cells are present on the surface of the four thin film materials, indicating that the four film materials have low cytotoxicity. Figure 11The images show fluorescence fusion patterns of live and dead cells. These images indicate that the introduction of BT or HA did not significantly affect the live / dead staining results, demonstrating that the composite film of this invention has good biocompatibility. This characteristic lays the foundation for bioengineering applications, and its potential value in the biomedical field deserves further investigation.

[0080] This invention discloses a method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film. The method employs a hierarchical composite strategy of first compositing and then blending. Compared to direct physical blending, barium titanate nanoparticles (BT) and hydroxyapatite nanorods (HA) are first chemically bonded to form a BT / HA composite filler via a solvothermal method. The skeletal effect of the one-dimensional HA nanorods can be utilized to suppress BT aggregation, strengthen interfacial bonding and polarization stability, and simultaneously improve the piezoelectric activity, rigidity, and biocompatibility of the system. Then, this BT / HA composite filler is spin-coated with polylactic acid (PLA) to form a film. The hydrogen bonding between the hydroxyl groups on the HA surface and the ester groups of PLA significantly improves the inorganic-organic interfacial compatibility, reduces interfacial defects and charge leakage, and enhances stress transfer efficiency and dielectric properties. Ultimately, this results in a significant improvement in the piezoelectric output, cycle stability, and sensing sensitivity of the composite film.

[0081] The 5wt% BT / HA / PLA piezoelectric nanocomposite film of this invention exhibits outstanding advantages in key piezoelectric output parameters (d). 33 Voc, Isc) and dielectric constant (ε) r In terms of performance, it significantly outperforms 5wt% HA / PLA and pure PLA, while maintaining a low loss tangent (tanδ). Compared to pure PLA, it achieves a leap in overall performance, with open-circuit voltage increasing from 3.85V to 8.56V (a growth rate of 122.3%), short-circuit current increasing from 98nA to 185nA (an enhancement of approximately 88.8%), and piezoelectric coefficient d... 33 The piezoelectricity was increased from 0.6 pC / N to 2.9 pC / N. The 5 wt% BT / HA / PLA nanocomposite film not only exhibited excellent piezoelectric properties and piezoelectric cycling stability (3000 seconds) and durability, but also possessed good biocompatibility and flexibility. This provides a new approach for the research of nanocomposite films for wearable health monitoring electronic devices. The BT / HA / PLA piezoelectric nanocomposite films prepared in Examples 6-9 of this invention have similar technical effects to those in Examples 1-5.

[0082] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film, characterized in that, The barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film comprises a polylactic acid matrix and a functional filler, wherein the functional filler is formed by a composite of barium titanate nanoparticles and hydroxyapatite nanorods; the mass fraction of the functional filler is 1-9%.

2. The self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film according to claim 1, characterized in that, The barium titanate nanoparticles are cubic perovskite crystals, and the hydroxyapatite nanorods are hexagonal crystal structures. The barium titanate nanoparticles are uniformly dispersed and attached to the hydroxyapatite nanorods.

3. The method for preparing the self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 1, characterized in that, Includes the following steps: S1. Preparation of barium titanate nanoparticles Ba(OH)2 Barium titanate nanoparticles were prepared by a solvothermal method using 8H2O, TiO2, KOH solution and 5% PVA solution as raw materials. S2. Preparation of functional fillers With Ca(NO3)2 A mixed solution was prepared by mixing 4H2O, (NH4)2HPO4 and deionized water. Then, the barium titanate nanoparticles obtained in S1 were mixed with the mixed solution, and functional fillers were prepared by solvothermal method. S3. Preparation of barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin films Barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite films were prepared by spin coating using functional fillers prepared by S2 and polylactic acid as raw materials.

4. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 3, characterized in that, The specific process for preparing barium titanate nanoparticles in step S1 is as follows: S11, Weigh out Ba(OH)2 Add 8H2O, TiO2, KOH solution and 5% PVA solution to a reaction vessel and stir thoroughly to obtain a mixture; S12. Transfer the mixture to a homogeneous reactor for a solvothermal reaction; S13. The obtained product is washed and dried to obtain barium titanate nanoparticles.

5. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 4, characterized in that, In step S11, the concentration of KOH solution is 0.2~5 mol / L, and Ba(OH)2 The molar ratio of 8H2O to TiO2 is (1.5~3):1; the volume of PVA solution used is 20~40mL; In step S12, the reaction temperature is 100~200℃ and the reaction time is 12~26h; In step S13, the obtained product is washed with ethanol and deionized water and dried at 60°C for 12 hours.

6. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 3, characterized in that, The specific process for preparing the functional filler in step S2 is as follows: S21. Weigh out Ca(NO3)2 4H2O and (NH4)2HPO4 were dissolved in 10 mL of deionized water to prepare solutions A and B, respectively. S22. Under thorough stirring, solution B is slowly added to solution A to obtain a mixed solution, and the pH of the mixed solution is adjusted to 10±0.5 with ammonia. S23. The barium titanate nanoparticles prepared in S1 are added to the mixed solution under continuous stirring, and a hydrothermal reaction is carried out. S24. The obtained product was washed with ethanol and deionized water and dried at 60°C for 12 hours to obtain the functional filler.

7. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 6, characterized in that, In step S21, Ca(NO3)2 The molar ratio of 4H2O to (NH4)2HPO4 is (1~2):1; in step S23, the stirring time is 0.5~2h, and the mass ratio of barium titanate nanoparticles to hydroxyapatite nanorods is (70~90):(30~10); the reaction is carried out at 100~200℃ for 12~26h.

8. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 3, characterized in that, The specific process for preparing the barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film in step S3 is as follows: S31. Under sealed conditions, polylactic acid is dissolved in CH2Cl2 and subjected to stirring and ultrasonic circulation at 0°C to obtain a polylactic acid solution. S32. Add functional filler to polylactic acid solution, and then stir and ultrasonically circulate the solution at 0°C to make the functional filler uniformly dispersed in the polylactic acid solution, so as to obtain barium titanate / hydroxyapatite / polylactic acid mixed solution. S33. A barium titanate / hydroxyapatite / polylactic acid mixed solution is spin-coated onto a circular substrate and dried to obtain a thin film. S34. The film is immersed in ethanol and peeled off to finally obtain a barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film based on polylactic acid matrix.

9. The method for preparing a self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite thin film according to claim 8, characterized in that, In step S31, the amount of CH2Cl2 used is 10~25mL; In step S32, the mass of the controlled functional filler accounts for 1-9% of the mass of polylactic acid; In step S33, the barium titanate / hydroxyapatite / polylactic acid mixed solution is dried at 60°C for 12 hours.

10. The application of the self-powered barium titanate / hydroxyapatite / polylactic acid piezoelectric nanocomposite film according to claim 1 in wearable health signal monitoring devices.

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