Degradable pllA / mxene piezoelectric material for reducing carbon emission and preparation method thereof

Abstract

This invention relates to the field of piezoelectric materials technology, specifically to a biodegradable PLLA / MXene piezoelectric material with reduced carbon emissions and its preparation method. The preparation method includes the following steps: S1, dissolving pretreated PLLA and MXene nanosheets in a fluorinated alcohol solvent, stirring at 40–80°C for 1–5 h, and then ultrasonically dispersing to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 6–12%; S2, patterning the PLLA / MXene solution using electrofluidic printing, and drying to obtain a composite film; S3, applying a pressure of 5–8 MPa at 120–140°C under an absolute vacuum of 5–10 kPa and holding the pressure for 10–15 min to obtain the PLLA / MXene piezoelectric material. This invention uses a fluorinated alcohol solvent and electrofluidic printing process to achieve oriented alignment of PLLA molecular chains and uniform dispersion of MXene nanosheets to enhance interfacial interactions, significantly improving the piezoelectric properties of the composite material while maintaining its excellent biodegradability.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric materials technology, and in particular to a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions and its preparation method. Background Technology

[0002] Piezoelectric materials are core materials in fields such as electronic sensing, micro-energy harvesting, and flexible electronic devices, and their application demand continues to increase. Traditional piezoelectric materials mostly use fossil resources as raw materials, resulting in high carbon emissions during production. Furthermore, they are difficult to degrade after failure, and their recycling or disposal easily releases greenhouse gases, contradicting low-carbon emission reduction goals. Currently, polylactic acid (PLLA) has been studied in the field of environmentally friendly materials due to its biodegradable properties. However, the piezoelectric properties of PLLA alone are relatively weak. In the field of electronic sensing, its sensitivity often fails to meet the requirements of high-precision detection, leading to large errors in detection results. In micro-energy harvesting, its energy conversion efficiency is low, making it difficult to effectively collect and utilize small amounts of energy from the environment, thus failing to meet the functional requirements of devices.

[0003] MXene is a class of two-dimensional inorganic compounds composed of transition metal carbides, nitrides, or carbonitrides with a thickness of several atomic layers, exhibiting the metallic conductivity of transition metal carbides. While MXene materials can help improve the functional properties of materials, they are prone to agglomeration due to their high surface energy. This is because the surface of MXene sheets contains a large number of functional groups, which interact strongly with each other, making the sheets prone to stacking together. This agglomeration phenomenon severely affects the dispersion of MXene in the PLLA matrix, resulting in an inhomogeneous internal structure of the composite piezoelectric material, preventing the linear improvement of piezoelectric performance, and even causing performance degradation at high doping concentrations. Furthermore, PLLA molecular chains are disordered and MXene has poor dispersion. PLLA / MXene composite processes do not combine performance and carbon reduction requirements. Existing composite processes often focus on improving the piezoelectric properties of the material while neglecting carbon emissions during production. For example, the use of highly toxic, volatile, and difficult-to-recover solvents (such as DMF and THF) and complex high-temperature and high-pressure processing methods increase carbon emissions during production, preventing the material from meeting functional and low-carbon requirements, as illustrated in patent document CN 120776515. Patent A discloses a biodegradable piezoelectric nanofiber membrane for bone repair, its preparation method, and its application. The preparation method includes the following steps: S1, mixing a PLLA solution and MXene nanosheets, heating and stirring to obtain a uniform PLLA / MXene mixed solution, wherein the molecular weight of PLLA in the PLLA solution is 80,000–120,000; S2, electrospinning the PLLA / MXene mixed solution to obtain a PLLA / MXene nanofiber membrane semi-finished product; S3, annealing, cooling, heat-treating, and second-cooling the PLLA / MXene nanofiber membrane semi-finished product to obtain the PLLA / MXene nanofiber membrane finished product, which is a biodegradable piezoelectric nanofiber membrane. This patent prepares fibers through electrospinning and annealing heat treatment, but does not address the synergistic need for improved piezoelectric performance and biodegradability, making it difficult to balance device functionality and low-carbon sustainability. This issue urgently needs to be addressed through research. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions and its preparation method.

[0005] In a first aspect, the present invention provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, comprising the following steps:

[0006] S1. Dissolve PLLA and MXene nanosheets in a fluorinated alcohol solvent, stir at 40–80°C for 1–5 h, and ultrasonically disperse to obtain a uniformly mixed PLLA / MXene solution with a mass concentration of 6–12%. S2. The PLLA / MXene solution is electro-hydraulic printed according to the designed pattern, and then dried to obtain a composite film. S3. Apply 5-8 MPa pressure to the composite membrane under vacuum and at 120-140℃, and keep it at the temperature and pressure for 10-15 minutes to obtain PLLA / MXene piezoelectric material.

[0007] In the above technical solution, PLLA is a bio-based biodegradable polymer, and its final degradation products are CO2 and H2O, leaving no environmental residue. In the preparation process, PLLA and MXene nanosheets are first dissolved in a fluorinated alcohol solvent, stirred, and sonicated to obtain a PLLA / MXene solution. Compared with DMF, THF, and other highly toxic and difficult-to-recover solvents used in traditional processes, the fluorinated alcohol solvent has lower toxicity and is easier to recycle, reducing VOC emissions. The PLLA / MXene solution is then electrofluidically printed according to the designed pattern to obtain a composite film. Compared with electrospinning, electrofluidic printing can directly form according to the CAD design pattern, realizing customized manufacturing of material shape, thickness, and layout, reducing material waste, and is suitable for scenarios with precise requirements for device structure, such as flexible electronics and micro-energy harvesting. The composite film is then subjected to a pressure of 5-8 MPa at 120-140℃ in a vacuum and held for 10-15 minutes to obtain PLLA / MXene piezoelectric material, without the need for long-term high-temperature sintering or complex post-processing. This invention achieves material biodegradability by using PLLA / MXene through blending with fluorinated alcohol solvents, customized electrohydraulic printing, and secondary hot pressing to enhance piezoelectric properties.

[0008] Preferably, the fluorinated alcohol solvent includes at least one of hexafluoroisopropanol and trifluoroethanol.

[0009] In the above technical solution, the fluorinated alcohol solvent includes at least one of hexafluoroisopropanol and trifluoroethanol, which has strong polarity and hydrogen bonding, and can simultaneously and well dissolve PLLA and disperse MXene, thus achieving uniform dispersion of PLLA and MXene. The solvent has a moderate evaporation rate and can induce high orientation of PLLA molecular chains during electrohydraulic printing, providing a structural basis for subsequent hot pressing to enhance piezoelectric properties.

[0010] More preferably, the fluorinated alcohol solvent is hexafluoroisopropanol. Hexafluoroisopropanol has strong polarity and hydrogen bonding, which can simultaneously and effectively disperse PLLA and MXene, and interact with the functional groups (-OH, =O, -F) on the surface of MXene; combined with ultrasonic dispersion, it effectively inhibits the stacking and aggregation of MXene sheets, ensuring the uniformity of the internal structure of the composite film.

[0011] Preferably, the PLLA is dried before use, under the following conditions: drying at 40-80°C for 8-16 hours to remove residual moisture.

[0012] Preferably, the molecular weight of the PLLA is 120,000 to 200,000.

[0013] In the above technical solution, the molecular weight of PLLA is limited to 120,000 to 200,000, which is suitable for electrohydraulic inkjet printing. This ensures that the molecular chains have sufficient fluidity to form an ordered arrangement during hot pressing, and the material possesses both good piezoelectric properties and mechanical strength. If the molecular weight of PLLA is too small (below 120,000), it will result in insufficient molecular chain entanglement, low mechanical strength after film formation, and weak piezoelectric response. If the molecular weight of PLLA is too large (above 200,000), the solution viscosity will be too high, which will easily clog the printhead during electrohydraulic inkjet printing, and the movement of molecular chains will be restricted, resulting in a decrease in orientation after hot pressing.

[0014] Preferably, the preparation method of the MXene nanosheets is as follows: LiF (lithium fluoride) powder is added to hydrochloric acid solution and stirred for 30-100 min, then Ti3AlC2 powder is added, with a LiF to Ti3AlC2 mass ratio of 1:1 to 1:2. The mixture is stirred continuously at 35-55℃ for 16-30 h, then centrifuged and washed until the pH of the supernatant is 6.5-7.5. The supernatant is then ultrasonically treated at 200-500 W power in an ice-water bath for 0.5-1.5 h, followed by centrifugation at 4000-5000 rpm to collect the supernatant, and then dried to obtain MXene nanosheets. In the above technical solution, the MXene nanosheets prepared by the LiF-HCl etching method are Ti3C2T X The above-mentioned MXene nanosheets were prepared by LiF-HCl etching, which yielded thin-layer nanosheets rich in surface functional groups (-OH, =O, -F, etc.). These functional groups formed hydrogen bonds with PLLA, enhancing the interfacial bonding force.

[0015] Preferably, the MXene nanosheets have 1 to 5 layers.

[0016] Preferably, the concentration of the hydrochloric acid solution is 1-20 mol / L. More preferably, the concentration of the hydrochloric acid solution is 8-12 mol / L.

[0017] Preferably, the mass ratio of LiF to Ti3AlC2 is 1:1 to 2. More preferably, the mass ratio of LiF to Ti3AlC2 is 1:1.2.

[0018] Preferably, in step S1, the viscosity of the PLLA / MXene solution is 80–150 cP.

[0019] In the above technical solution, the viscosity of the PLLA / MXene solution is 80-150 cP. The viscosity of the PLLA / MXene solution directly determines the feasibility and quality of electrohydraulic inkjet printing film formation: when the viscosity is too low, the solution is prone to spreading and leakage due to insufficient surface tension, and cannot maintain the design pattern shape. Moreover, droplet splashing and line breakage are likely to occur during electrohydraulic inkjet printing. When the viscosity is too high, it will lead to increased pump delivery resistance, easy nozzle blockage, and the solution cannot be smoothly extruded to form a continuous jet. Even if a film is formed, the poor molecular chain fluidity and uneven dispersion will result in film cracking and high porosity, ultimately failing to form a dense and uniform effective film layer. Within the above viscosity range, it is suitable for electrohydraulic inkjet printing process, ensuring pattern accuracy and film uniformity.

[0020] Preferably, in step S3, hot pressing involves feeding the composite film into a vacuum hot press forming machine and drawing an absolute vacuum of 5-10 kPa.

[0021] Preferably, the film thickness of the PLLA / MXene piezoelectric material is 100-120 μm.

[0022] In a second aspect, the present invention provides a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, wherein the PLLA / MXene piezoelectric material is obtained by the above-described method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions.

[0023] Preferably, the piezoelectric material uses PLLA as a matrix and uniformly disperses 1 to 5 layers of Ti3C2T. x The piezoelectric material has MXene nanosheets with highly oriented PLLA molecular chains, an open-circuit voltage ≥1.0V, a short-circuit current ≥20nA, and a degradation rate ≥80% in simulated body fluid (pH 7.4) at 37℃ for 6 months.

[0024] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions. PLLA is a bio-based biodegradable material that can significantly reduce carbon emissions during production and use. The addition of MXene nanosheets can effectively improve the piezoelectric properties of PLLA, enabling the material to generate a stronger electrical signal when subjected to external force. The composite piezoelectric material is prepared by blending with an alcohol solvent and custom molding by electrohydraulic spraying combined with vacuum hot pressing at 120~140℃. The MXene doping ratio is 2~10%, and the total solution mass concentration is 6~12%, which improves the piezoelectric properties while achieving material degradability.

[0025] 2. This invention provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions. Testing showed that the prepared piezoelectric material has an open-circuit voltage of 1.0-2.8V and a short-circuit current of 12.1-71.1nA, which are 2-5.6 times and 2.4-14.2 times higher than pure PLLA, respectively. In simulated body fluid (pH 7.4) at 37℃, the degradation rate is ≥80% after 6 months, with the final products mainly being CO2 and H2O, and no organic residue.

[0026] 3. The piezoelectric material preparation method provided by this invention has mature technology and controllable cost, and is suitable for scenarios such as electronic sensing, micro-energy harvesting, and flexible electronic devices, and has good industrialization prospects. Attached Figure Description

[0027] Figure 1 SEM image of MXene nanosheets prepared according to this invention; Figure 2 The FTIR spectra of the piezoelectric materials in Examples 1-5 and Comparative Example 1 are shown below. Figure 3 The XRD pattern of the piezoelectric material in Example 3 is shown below. Figure 4 The open-circuit voltage data are for the piezoelectric materials of Examples 1-5 and Comparative Example 1; Figure 5 The short-circuit current data are for the piezoelectric materials of Examples 1-5 and Comparative Example 1; Figure 6 The degradation data are for the piezoelectric material in Example 3. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0029] In the following examples, the PLLA used had weight-average molecular weights of 120,000 g / mol, 150,000 g / mol, and 200,000 g / mol, and a L-lactic acid content of ≥90%. The PLLA was pretreated and dried in a vacuum drying oven at 60°C for 12 hours to remove residual moisture, with the moisture content below 10 ppm.

[0030] MXene nanosheets were prepared by LiF-HCl etching: 1g of LiF powder was added to 20mL of 9M hydrochloric acid solution, stirred at room temperature for 60min, and then 1g of Ti3AlC2 powder was slowly added. The mixture was stirred continuously at 35-55℃ for 24h. The resulting sample was repeatedly centrifuged and washed until the supernatant pH≈7. After ultrasonic treatment at 300W power in an ice-water bath for 1h, the supernatant was collected by centrifugation at 4000-5000rpm, filtered, and dried to obtain MXene nanosheets. Figure 1 The image shown is a SEM image of MXene nanosheets, which have 1 to 5 layers.

[0031] Instruments: Vacuum drying oven, ultrasonic disperser, thermostatic stirrer, high-precision injection pump (with 16G stainless steel nozzle), 0-15kV high-voltage DC power supply, three-dimensional motion platform, vacuum hot press molding machine (including PID temperature controller and 0-10MPa pressure sensor), 6517 linear motor, water bath.

[0032] Example 1 This embodiment provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, including the following steps: S1. Dissolve PLLA and MXene nanosheets in hexafluoroisopropanol, stir at 60℃ for 3 hours, and then disperse with an ultrasonic disperser for 60 minutes to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 8%, of which the weight average molecular weight of PLLA is 150,000 g / mol and the proportion of MXene nanosheets is 2%, ensuring that there is no obvious precipitation in the solution. S2. Subsequently, a customized pattern is drawn using CAD software, and the motion control card is converted into a three-dimensional motion platform trajectory. The injection pump delivers the blended solution at a rate of 1-5 mL / h, and a high-voltage DC power supply applies a voltage of 3-6 kV (8-12 cm between the nozzle and the substrate). The PLLA / MXene solution is electro-hydraulic printed according to the designed pattern, and then dried in a 50°C oven for 15-30 minutes to obtain a composite film. S3. Next, the composite film is peeled off from the substrate and sent into a vacuum hot press forming machine. The absolute vacuum is evacuated to 5-10 kPa. The composite film is subjected to a pressure of 5-8 MPa at 120-140°C under vacuum. The temperature and pressure are maintained for 10-15 minutes to obtain PLLA / MXene piezoelectric material. The film thickness is controlled to be 100-120 μm.

[0033] Example 2 This embodiment provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, including the following steps: S1. Dissolve PLLA and MXene nanosheets in hexafluoroisopropanol, stir at 80℃ for 2 hours, and then disperse using an ultrasonic disperser for 1 hour to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 8%, wherein the weight-average molecular weight of PLLA is 120,000 g / mol, and the proportion of MXene nanosheets is 4%. S2. Subsequently, a customized pattern is drawn using CAD software, the motion control card is converted into a three-dimensional motion platform trajectory, the injection pump delivers the blended solution at 1-5 mL / h, a high-voltage DC power supply applies a voltage of 3-6 kV, the PLLA / MXene solution is electro-hydraulic printed according to the design pattern, and dried in a 50℃ oven for 15-30 min to obtain a composite film. S3. Next, the composite film is peeled off from the substrate and sent into a vacuum hot press forming machine. The absolute vacuum is evacuated to 5-10 kPa. The composite film is subjected to a pressure of 5-8 MPa at 120-140°C under vacuum. The temperature and pressure are maintained for 10-15 minutes to obtain PLLA / MXene piezoelectric material. The film thickness is controlled to be 100-120 μm.

[0034] Example 3 This embodiment provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, including the following steps: S1. Dissolve PLLA and MXene nanosheets in hexafluoroisopropanol, stir at 80℃ for 2 hours, and then disperse using an ultrasonic disperser for 1 hour to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 8%, a PLLA weight-average molecular weight of 150,000 g / mol, and an MXene nanosheet content of 6%. S2. Subsequently, a customized pattern is drawn using CAD software, the motion control card is converted into a three-dimensional motion platform trajectory, the injection pump delivers the blended solution at 1-5 mL / h, a high-voltage DC power supply applies a voltage of 3-6 kV, the PLLA / MXene solution is electro-hydraulic printed according to the design pattern, and dried in a 50℃ oven for 15-30 min to obtain a composite film. S3. Next, the composite film is peeled off from the substrate and sent into a vacuum hot press forming machine. The absolute vacuum is evacuated to 5-10 kPa. The composite film is subjected to a pressure of 5-8 MPa at 120-140°C under vacuum. The temperature and pressure are maintained for 10-15 minutes to obtain PLLA / MXene piezoelectric material. The film thickness is controlled to be 100-120 μm.

[0035] Example 4 This embodiment provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, including the following steps: S1. Dissolve PLLA and MXene nanosheets in hexafluoroisopropanol, stir at 80℃ for 2 hours, and then disperse using an ultrasonic disperser for 1 hour to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 8%, wherein the weight-average molecular weight of PLLA is 120,000 g / mol, and the proportion of MXene nanosheets is 8%. S2. Subsequently, a customized pattern is drawn using CAD software, the motion control card is converted into a three-dimensional motion platform trajectory, the injection pump delivers the blended solution at 1-5 mL / h, a high-voltage DC power supply applies a voltage of 3-6 kV, the PLLA / MXene solution is electro-hydraulic printed according to the design pattern, and dried in a 50℃ oven for 15-30 min to obtain a composite film. S3. Next, the composite film is peeled off from the substrate and sent into a vacuum hot press forming machine. The absolute vacuum is evacuated to 5-10 kPa. The composite film is subjected to a pressure of 5-8 MPa at 120-140°C under vacuum. The temperature and pressure are maintained for 10-15 minutes to obtain PLLA / MXene piezoelectric material. The film thickness is controlled to be 100-120 μm.

[0036] Example 5 This embodiment provides a method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, including the following steps: S1. Dissolve PLLA and MXene nanosheets in hexafluoroisopropanol, stir at 80℃ for 2 hours, and then disperse using an ultrasonic disperser for 1 hour to obtain a uniformly mixed PLLA / MXene solution with a total mass concentration of 8%, wherein the weight-average molecular weight of PLLA is 120,000 g / mol, and the proportion of MXene nanosheets is 10%. S2. Subsequently, a customized pattern is drawn using CAD software, the motion control card is converted into a three-dimensional motion platform trajectory, the injection pump delivers the blended solution at 1-5 mL / h, a high-voltage DC power supply applies a voltage of 3-6 kV, the PLLA / MXene solution is electro-hydraulic printed according to the design pattern, and dried in a 50℃ oven for 15-30 min to obtain a composite film. S3. Next, the composite film is peeled off from the substrate and sent into a vacuum hot press forming machine. The absolute vacuum is evacuated to 5-10 kPa. The composite film is subjected to a pressure of 5-8 MPa at 120-140°C under vacuum. The temperature and pressure are maintained for 10-15 minutes to obtain PLLA / MXene piezoelectric material. The film thickness is controlled to be 100-120 μm.

[0037] Comparative Example 1 This comparative example is similar to Example 3, except that MXene nanosheets were not used; only pure PLLA was used, and the piezoelectric material was obtained using the same preparation method as in Example 3.

[0038] Comparative Example 2 This comparative example is similar to Example 3, except that N,N-dimethylformamide (DMF) is used as the solvent and the same preparation method as in Example 3 is used. Because PLLA cannot be dissolved, a thin film piezoelectric material cannot be obtained.

[0039] Comparative Example 3 This comparative example is similar to Example 1, except that the weight-average molecular weight of PLLA is 80,000 (less than 120,000), and the piezoelectric material is obtained using the same preparation method as in Example 3.

[0040] Comparative Example 4 This comparative example is similar to Example 1, except that the weight-average molecular weight of PLLA is 250,000 (higher than 200,000), and the piezoelectric material is obtained using the same preparation method as in Example 3.

[0041] Comparative Example 5 This comparative example is similar to Example 1, except that the temperature in step S3 is 100°C, and the piezoelectric material is obtained using the same preparation method as in Example 3.

[0042] Comparative Example 6 This comparative example is similar to Example 1, except that the temperature in step S3 is 160°C, and the piezoelectric material is obtained using the same preparation method as in Example 3.

[0043] Comparative Example 7 This comparative example is similar to Example 1, except that the proportion of MXene nanosheets is 15%, and the piezoelectric material is obtained using the same preparation method as in Example 3.

[0044] Test Example 1 The PLLA / MXene piezoelectric materials prepared in Examples 1-5 and Comparative Examples 1-7 were tested for open-circuit voltage and short-circuit current using a 6517 electrometer unit. Samples measuring 1 cm × 1 cm × 110 μm were prepared at 25°C and 50% relative humidity, coated with a 100 nm thick silver electrode, and subjected to a sinusoidal pressure of 20 N peak force and 1 Hz frequency. Quasi-static d 33 The tester measures the piezoelectric coefficient d. 33 The degradation performance was assessed by placing 1cm×1cm×110μm samples in PBS buffer at 37℃ and pH=7.4. Weight loss was measured using an electronic balance every 30 days. The results are shown in Table 1. Experimental precautions: PLLA must be thoroughly dried to prevent subsequent hydrolysis from affecting performance. MXene centrifugation and washing must ensure pH≈7. Hot pressing temperature must be controlled below the PLLA melting point to preserve the customized pattern.

[0045] Test data of Examples 1-5 and Comparative Examples 1-7

[0046] Figure 2 The FTIR spectra of Examples 1-5 and Comparative Example 1 are shown at 1747 cm⁻¹. -1 At point C=O, at 1450cm -1 The concentration is CH3, at 1180cm. -1 The location is COC, at 1080cm. -1 The location is COC, at 1035cm. -1 The position is C-CH3, at 920-930 cm. -1 The peak at this location is a characteristic peak of the amorphous region. Figure 3 The image shows the XRD pattern of the PLLA / MXene piezoelectric material in Example 3.

[0047] Figure 4 and Figure 5 The data are open-circuit voltage and short-circuit current, respectively. Example 1 uses 98% PLLA + 2% MXene as the piezoelectric material, with an open-circuit voltage of 1.0V and a short-circuit current of 12.1nA. Example 2 uses 96% PLLA + 4% MXene as the piezoelectric material, with an open-circuit voltage of 2.0V and a short-circuit current of 33.4nA. Example 3 uses 94% PLLA + 6% MXene as the piezoelectric material, with an open-circuit voltage of 2.8V and a short-circuit current of 71.1nA. Example 4 uses... The material used in Example 5 is 92% PLLA + 8% MXene, with an open-circuit voltage of 1.8V and a short-circuit current of 40.5nA. The piezoelectric material used in Example 5 is 98% PLLA + 2% MXene, with an open-circuit voltage of 1.4V and a short-circuit current of 25.6nA. When the MXene concentration is 6%, the material's open-circuit voltage is approximately 2.8V and the short-circuit current is approximately 71.1nA, which are 5.6 times and 14.2 times higher than pure PLLA, respectively, effectively solving the problem of weak piezoelectric performance of single PLLA. Figure 4 The data for the degradation of the PLLA / MXene piezoelectric material film in Example 1 are as follows: weights of 20 mg (0 months), 18.9 mg (1 month), 14.4 mg (2 months), 11.1 mg (3 months), 8.2 mg (4 months), 5.4 mg (5 months), and 3.6 mg (6 months). Regarding degradation performance, the material exhibits a degradation rate >80% after 6 months in PBS buffer at 60°C and pH 7.4. The final products are CO2 and H2O, with no organic residue, thus avoiding carbon emissions associated with the disposal of traditional piezoelectric materials. The 6-month degradation rates of the PLLA / MXene piezoelectric materials in Examples 2-5 are all >80%.

[0048] Comparative Example 1's piezoelectric material, without the addition of MXene and using only pure PLLA, exhibited an open-circuit voltage of 0.5V and a short-circuit current of 5.7nA. While possessing some piezoelectricity, its weak polarization and low charge collection efficiency resulted in significantly lower voltage and current outputs compared to all other examples. Comparative Example 2's piezoelectric material was prepared using DMF as a solvent. DMF has poor solubility for PLLA, failing to form a uniform and stable blend solution, thus hindering subsequent electrohydrodynamic printing and preventing the acquisition of continuous thin films.

[0049] The piezoelectric material used in Comparative Example 3 has a PLLA molecular weight of only 80,000, which is lower than the 120,000-200,000 range specified in this invention. Its open-circuit voltage is 0.8V, and its short-circuit current is 10.9nA. 33 = 6.7pC / N. The low molecular weight results in excessively short polymer chains, making it difficult to form a highly oriented crystal structure during hot pressing, leading to a significant decrease in piezoelectric response. Although the degradation rate remains high, the insufficient molecular weight limits chain segment movement and polarization ability. The piezoelectric material in Comparative Example 4 used a molecular weight of 250,000, exceeding the 200,000 upper limit, with an open-circuit voltage of 0.9V and a short-circuit current of 11.2nA. 33 = 6.9 pC / N. The excessively high molecular weight leads to a significant increase in solution viscosity, which is not conducive to filament formation and solvent evaporation during electrohydraulic printing. At the same time, excessive chain segment entanglement during hot pressing restricts orientation and reduces piezoelectric properties. The above indicates that a suitable PLLA molecular weight window of 120,000-200,000 is crucial for the forming and orientation of piezoelectric materials.

[0050] In Comparative Example 5, the hot-pressing temperature of the piezoelectric material prepared was only 100℃, lower than the effective orientation temperature range of PLLA (120–140℃). The open-circuit voltage was 0.6V, and the short-circuit current was 6.9nA. 33 = 4.8 pC / N. The hot-pressing temperature was too low, resulting in insufficient polymer chain mobility. The polymer chains could not align sufficiently in a specific direction under pressure, leading to piezoelectric properties close to those of pure PLLA. The temperature was too low to trigger chain orientation recombination. In Comparative Example 6, the hot-pressing temperature for the piezoelectric material was 160℃, exceeding the effective orientation temperature range of PLLA. The open-circuit voltage was 0.9V, and the short-circuit current was 11.6nA. 33 = 6.9 pC / N. The hot pressing temperature is too high. Although it is not completely melted, it has approached or entered the melting zone, which leads to the destruction of the ordered structure inside the material. Phase separation or agglomeration occurs at the MXene / PLLA interface, and the piezoelectric properties decrease. Excessive temperature will destroy the already formed orientation structure.

[0051] The piezoelectric material of Comparative Example 7 has an MXene doping ratio of 15%, exceeding the 2-10% range specified in this invention. Its open-circuit voltage is 0.8V, and its short-circuit current is 10.7nA. 33= 4.1 pC / N, degradation rate 78.4%. Excess MXene severely aggregates in the PLLA matrix, forming localized conductive pathways, reducing material resistance, and weakening piezoelectric output. Simultaneously, the agglomeration interface becomes a stress concentration point, disrupting polarization continuity. 33 The degradation rate decreased slightly, possibly due to MXene aggregation hindering the penetration of the hydrolysis medium. The ratio of MXene nanosheets to the total mass of PLLA and MXene nanosheets was limited to 2–10%.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a biodegradable PLLA / MXene piezoelectric material that reduces carbon emissions, characterized in that, Includes the following steps: S1. Dissolve PLLA and MXene nanosheets in a fluorinated alcohol solvent, stir at 40–80°C for 1–5 h, and ultrasonically disperse to obtain a uniformly mixed PLLA / MXene solution with a mass concentration of 6–12%. S2. The PLLA / MXene solution is electro-hydraulic printed according to the designed pattern, and then dried to obtain a composite film. S3. Apply 5-8 MPa pressure to the composite membrane under vacuum and at 120-140℃, and keep it at the temperature and pressure for 10-15 minutes to obtain PLLA / MXene piezoelectric material.

2. The preparation method according to claim 1, characterized in that, The fluoroethanol solvent contained is selected from at least one of hexafluoroisopropanol and trifluoroethanol.

3. The preparation method according to claim 1, characterized in that, The weight-average molecular weight of the PLLA is 120,000 to 200,000. Before using the PLLA, it is dried under vacuum at 40 to 80°C for 8 to 16 hours.

4. The preparation method according to claim 1, characterized in that, The MXene nanosheets are Ti3C2T x The MXene nanosheets were prepared by the following method: LiF powder was added to a hydrochloric acid solution with a concentration of 8-12 mol / L and stirred for 30-100 min. Then Ti3AlC2 powder was added, with a mass ratio of LiF to Ti3AlC2 of 1:1 to 1:

2. The mixture was stirred continuously at 35-55℃ for 16-30 h. After centrifugation and washing until the pH of the supernatant was 6.5-7.5, the supernatant was ultrasonically treated at 200-500 W power and under ice-water bath conditions for 0.5-1.5 h. The supernatant was then centrifuged at 4000-5000 rpm and dried to obtain MXene nanosheets.

5. The preparation method according to claim 4, characterized in that, The MXene nanosheets have 1 to 5 layers; And / or the concentration of the hydrochloric acid solution is 1-20 mol / L.

6. The preparation method according to claim 1, characterized in that, The viscosity of the PLLA / MXene solution in step S1 is 80–150 cP.

7. The preparation method according to claim 1, characterized in that, In step S1, MXene nanosheets account for 2 to 10% of the total mass of PLLA and MXene.

8. The preparation method according to claim 1, characterized in that, In step S3, hot pressing involves feeding the composite film into a vacuum hot pressing machine and drawing an absolute vacuum of 5-10 kPa.

9. The preparation method according to claim 1, characterized in that, The film thickness of the PLLA / MXene piezoelectric material is 100-120 μm.

10. A biodegradable PLLA / MXene piezoelectric material for reducing carbon emissions, characterized in that, The piezoelectric material is obtained by the preparation method according to any one of claims 1-9.

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