A high-voltage electric gamma-glycine / pva film and preparation and application thereof

Abstract

The application relates to a high-voltage electric gamma-glycine / PVA film and preparation and application thereof, and belongs to the field of biological piezoelectric materials. The application provides a preparation method of a gamma-glycine / PVA film, which comprises the following steps: firstly, stirring and uniformly mixing a glycine aqueous solution and a PVA aqueous solution at 80-100 DEG C to prepare a blending liquid; then, drying the blending liquid to prepare a composite film, and introducing ultrasonic treatment in the drying process; and finally, peeling the dried film to prepare the gamma-glycine / PVA film. In the process of preparing a wafer-level heterostructure glycine film by using a direct coagulation process, ultrasonic treatment is introduced, so that an oriented gamma-glycine / PVA film can be obtained, the piezoelectric performance of the obtained film is almost twice that of a gamma-glycine / PVA film prepared by using a direct coagulation process, and a negative strain curve of gamma-glycine is observed for the first time through testing.

Description

Technical Field

[0001] This invention relates to a high-voltage γ-glycine / PVA thin film, its preparation and application, and belongs to the field of biopiezoelectric materials. Background Technology

[0002] Piezoelectric materials are a class of materials capable of converting electrical energy into mechanical energy. Due to their unique electromechanical conversion properties, they have enormous potential for self-powered or wireless power supply, and could replace the toxic chemical batteries used in most medical devices. Currently, the piezoelectric materials used in most biomedical fields are still inorganic piezoelectric ceramics, such as lead magnesium niobate (PMN-PT), lead zirconate titanate (PZT), and potassium sodium niobate (KNN). These ceramics are rigid, difficult to process precisely, and may even contain toxic elements (such as lead), making them difficult to biodegrade. Even flexible piezoelectric polymers, such as polyvinylidene fluoride (PVDF), do not meet the requirements for biodegradability. These shortcomings severely limit their application in on-demand transient devices. Therefore, it is essential to prioritize, develop, and optimize biodegradable biopiezoelectric materials for use in next-generation medical electronic devices.

[0003] Studies have shown that some organic materials, such as silk, collagen, and amino acids, are piezoelectric. However, due to the lack of large-scale domain arrangement (either spontaneous or due to polarization) and poor piezoelectric properties, as well as difficulties in polarization, whether electric or mechanical, research on these biomaterials remains largely at the conceptual or theoretical level, severely hindering their practical applications.

[0004] Glycine, one of the simplest amino acids, exists in three crystalline forms: a non-piezoelectric α phase and piezoelectrically active β and γ phases. The β phase, reportedly unstable both kinetically and thermodynamically, exhibits significant shear piezoelectricity (178 pm V). -1 ) and a good piezoelectric voltage coefficient (8000×10 -3 Vm N -1 The piezoelectricity of glycine crystals is comparable to that of PZT ceramics. Subsequent work has largely focused on stabilizing the β-phase of glycine and orienting its domains. However, reported methods, including electrospinning and electrohydrodynamic spraying, are quite complex and require high electric fields to achieve domain orientation, making them difficult to industrialize and energy-intensive. Therefore, a simple and flexible preparation method is urgently needed to improve the piezoelectricity of glycine crystals. The piezoelectricity of wafer-level heterostructured glycine films prepared by direct solidification originates from γ-glycine oriented through hydrogen bonding with polyvinyl alcohol (PVA). Although this preparation method is simple and novel, the piezoelectric properties of the obtained γ-glycine still differ significantly from theoretical values ​​due to inconsistent crystal growth orientation. Summary of the Invention

[0005] To address the aforementioned deficiencies, the applicant of this invention points out for the first time that the closer the growth direction of γ-glycine is to the c-axis, the higher its piezoelectric properties. Based on this, the applicant points out that in the process of preparing wafer-level heterostructure glycine films using direct solidification, introducing ultrasonic treatment can obtain orientation-optimized γ-glycine / PVA films, and the piezoelectric properties of the obtained films are almost twice that of γ-glycine / PVA films prepared by the direct solidification process. Furthermore, the applicant observes the negative strain curve of γ-glycine for the first time through testing.

[0006] The technical solution of this invention:

[0007] The first technical problem to be solved by the present invention is to provide a method for preparing a γ-glycine / PVA film. The preparation method is as follows: first, glycine aqueous solution and PVA aqueous solution are stirred and mixed at 80-100°C to obtain a blend; then, the blend is dried to form a composite film, and ultrasonic treatment is introduced during the drying process; finally, the dried film is peeled off to obtain the γ-glycine / PVA film.

[0008] Furthermore, the volume ratio of glycine aqueous solution to PVA aqueous solution is 1 to 2:1.

[0009] Furthermore, the drying temperature is 50–60°C.

[0010] Furthermore, the frequency of the ultrasonic treatment is 0.1–2 MHz.

[0011] The second technical problem to be solved by the present invention is to provide a γ-glycine / PVA film prepared by the above method.

[0012] Furthermore, the γ-glycine / PVA film has a sandwich structure, in which layered γ-glycine is encapsulated in the middle by PVA.

[0013] Furthermore, the piezoelectric properties of the γ-glycine / PVA film are 5.4±0.5~10.4±0.5 pC N. -1 .

[0014] Furthermore, the piezoelectric voltage coefficient of the γ-glycine / PVA film is 201 × 10⁻⁶. -3 ~300×10 -3 Vm N -1 .

[0015] The third technical problem this invention aims to solve is to specify the applications of the aforementioned γ-glycine / PVA thin film in wireless detection, sensors, or accelerators. These applications include wireless detection, diagnosis, and treatment in transient medical electronics, such as arterial pulse sensing, on-demand pain management, and accelerated wound healing, as well as industrial applications in biodegradable sensors and accelerators.

[0016] The fourth technical problem to be solved by this invention is to provide a method for improving the piezoelectric properties of γ-glycine / PVA thin films, wherein the method involves: promoting the growth direction of γ-glycine closer to the c-axis (i.e., the

[001] direction, such as...) Figure 7 ).

[0017] Furthermore, the above method for improving the piezoelectric properties of γ-glycine / PVA films is as follows: glycine / PVA films are prepared using a direct solidification process, and ultrasonic treatment is introduced during the film preparation process.

[0018] Furthermore, the above method for improving the piezoelectric properties of γ-glycine / PVA film is as follows: first, glycine aqueous solution and PVA aqueous solution are stirred and mixed at 80-100℃ to obtain a blend; then, the blend is dried to form a composite film, and ultrasonic treatment is introduced simultaneously during the drying process; finally, the dried film is peeled off to obtain the γ-glycine / PVA film.

[0019] The beneficial effects of this invention are:

[0020] This invention provides a method for synthesizing ultrasound-assisted self-aligned piezoelectric γ-glycine / PVA thin films. Ultrasound lowers the nucleation barrier and prevents aggregation, resulting in more uniform γ-glycine growth closer to the c-axis, thereby improving piezoelectric properties. The piezoelectricity of the γ-glycine / PVA thin film prepared by this method is 10.4 pCN. -1 Compared with the direct solidification method, it is 196% higher; the piezoelectric voltage coefficient is 324×10. -3 Vm N -1 Compared with the direct solidification method, it improved by 208%; and for the first time, the negative strain curve of γ-glycine / PVA film was experimentally observed. Attached image description:

[0021] Figure 1 This is a schematic diagram of the γ-glycine / PVA film preparation process in an example of the present invention.

[0022] Figure 2The images show: (a) a SEM image of the cross-section of the γ-glycine / PVA film in embodiment (of the present invention); (bd) elemental distribution diagrams of the cross-section, showing N, C, and O elements; scale bar: 100 micrometers. As can be seen from the images, the γ-glycine / PVA film obtained by the preparation method of the present invention has a sandwich structure, with layered glycine encapsulated in the middle by PVA. The N element, present only in glycine, is observed to be concentrated in the middle part, while C and O elements are more concentrated on the top and bottom sides, indicating that the structure of the γ-glycine / PVA film is that glycine is distributed in the middle layer, and PVA is at the top and bottom.

[0023] Figure 3 The images show the XRD patterns of γ-glycine / PVA films prepared from the materials obtained in the embodiments and comparative examples of this invention at different glycine / PVA ratios. When no PVA is added, the obtained glycine is the α-phase. As the glycine content increases, α-glycine gradually transforms into γ-glycine. When the ratio of glycine to PVA increases to 2:1, the characteristic peak of the γ-phase is observed, and no other phase peaks are observed, indicating that the piezoelectrically active γ-phase dominates in the composite film. The -OH group of PVA is always exposed and tends to combine with glycine to form hydrogen bonds, thereby forming self-aligned γ-glycine throughout the film. Therefore, the γ-glycine / PVA film can generate piezoelectricity without polarization. When the ratio of glycine to PVA is further increased to 3:1, the characteristic peak of α-glycine reappears, possibly indicating that the diffusion and separation of excess glycine and PVA are more challenging. In particular, an enhanced (102) peak (around 35°) was observed in the 2:1 γ-glycine / PVA film, which is closer to the c-axis than the reported

[101] oriented glycine / PVA film.

[0024] Figure 4 The image shows a comparison of the XRD patterns of the 2:1 γ-glycine / PVA film obtained in Example 3 of this invention and the glycine powder collected from the middle of the 2:1 γ-glycine / PVA film. As can be seen from the figure, glycine is in the γ phase in both the film and the powder. However, compared with the collected glycine powder, the (102) peak in the 2:1 γ-glycine / PVA film is significantly enhanced, further proving that γ-glycine grows in the PVA layer along the

[102] direction.

[0025] Figure 5 The figures show the XRD patterns of the materials obtained in Example 3 and Comparative Example 1 before and after ultrasonic treatment. As can be seen from the figures, with the help of ultrasonic treatment, the γ phase of glycine in the 2:1 γ-glycine / PVA film is more uniform and pure. More importantly, after ultrasonic treatment, the orientation of the γ-glycine crystals changes, and the (102) peak is enhanced.

[0026] Figure 6The figure shows the biaxial strain curve of the 2:1 γ-glycine / PVA film in Example 3 of the present invention; as can be seen from the figure, the strain curve exhibits a negative bud-like characteristic.

[0027] Figure 7 The diagram shows the growth direction of γ-glycine in this invention.

[102] (red arrow) is closer to the c-axis, i.e., the

[001] direction, than

[101] (blue arrow). As can be seen from the figure, by applying ultrasound, the growth direction of γ-glycine crystals in the 2:1 γ-glycine / PVA film changes from

[101] (comparative example 1, blue arrow in the figure) to

[102] (example 3, red arrow in the figure), and its growth direction is closer to the c-axis, i.e., the angle between the growth direction and the c-axis is smaller and closer to the

[001] direction. Detailed Implementation

[0028] The applicant of this invention discovered that the closer the growth direction of γ-glycine is to the c-axis, the higher its piezoelectric properties. Based on this, this invention improves the preparation method of glycine, especially by optimizing the crystal orientation to make it as close to the c-axis as possible to fully develop its piezoelectric properties, thereby obtaining a high-voltage γ-glycine / PVA film; this is of vital significance.

[0029] This invention provides a method for synthesizing a self-aligned, high-voltage γ-glycine / PVA thin film using ultrasound-assisted synthesis. The specific steps are as follows: Step 1: Mixing glycine and PVA aqueous solutions uniformly in a specific ratio; Step 2: Drying the mixture obtained in Step 1 under ultrasound; After the mixture is completely dried, a γ-glycine / PVA thin film is obtained. In this invention, ultrasound can lower the energy barrier for nucleation, thereby accelerating the crystallization process. Simultaneously, the introduction of ultrasound enhances solution mixing, increases particle collisions, and prevents agglomeration, thus achieving the preparation of a uniform and consistently oriented γ-glycine / PVA thin film.

[0030] The following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0031] Examples 1-3

[0032] I. Preparation of glycine and PVA solution

[0033] 1) Add 10 grams of glycine (Yuanye Bio) to 100 ml of deionized water and stir until completely dissolved to form a glycine solution.

[0034] 2) Add 10 grams of PVA (Guoyao) to 100 ml of deionized water and stir in an oil bath at 100°C for 3 hours until the PVA is completely dissolved.

[0035] II. Preparation of a mixed solution of glycine and PVA

[0036] The glycine solution and PVA solution obtained in step one were mixed in different volume ratios of 1:1 (Example 1), 1.5:1 (Example 2), and 2:1 (Example 3) to obtain glycine / PVA mixed solutions. For example, a 2:1 glycine / PVA solution is obtained by adding 20 ml of glycine solution to 10 ml of PVA solution. The glycine / PVA mixed solution was stirred in an oil bath at 100°C for 1 hour to ensure uniform mixing.

[0037] III. Preparation of γ-glycine / PVA films

[0038] Transfer an appropriate amount of the homogeneous solution obtained in step two into a petri dish (7 cm in diameter) until the solution completely covers the bottom of the dish. Place the petri dish containing the mixture in a drying oven and dry it at 60°C while simultaneously applying ultrasound at a frequency of 1 MHz until the solution is completely dry. Finally, the γ-glycine / PVA film is directly peeled off from the petri dish.

[0039] The piezoelectric properties and piezoelectric voltage coefficients of the obtained γ-glycine / PVA films with different ratios are shown in Table 1. The piezoelectric properties are obtained by quasi-static d... 33 The tester (Institute of Acoustics, Chinese Academy of Sciences, ZJ-3A) was used to test the piezoelectric voltage coefficient, which was calculated from the piezoelectric constant and dielectric constant, where the piezoelectric constant and dielectric constant were taken as the average value of the thin film.

[0040] Furthermore, the 2:1 membrane was characterized using a ferroelectric strain gauge (TF2000) at 160 kV cm⁻¹. -2 Under an electric field, the biaxial strain curve of the 2:1 γ-glycine / PVA film exhibits a negative bud-like characteristic (e.g. Figure 6 ).

[0041] Table 1. Raw material ratios and piezoelectric properties of the embodiments and comparative examples of the present invention.

[0042]

[0043] Comparative Example 1

[0044] I. Preparation of glycine and PVA solution

[0045] 1) Add 10 grams of glycine (Yuanye Bio) to 100 ml of deionized water and stir until completely dissolved to form a glycine solution.

[0046] 2) Add 10 grams of PVA (Guoyao) to 100 ml of deionized water and stir in an oil bath at 100°C for 3 hours until the PVA is completely dissolved.

[0047] II. Preparation of a mixed solution of glycine and PVA

[0048] Mix the glycine and PVA solution obtained in step one at a ratio of 2:1, that is, add 20 ml of glycine solution to 10 ml of PVA solution, and then stir the glycine / PVA mixture in an oil bath at 100°C for 1 hour to mix evenly.

[0049] III. Preparation of γ-glycine / PVA films

[0050] Transfer an appropriate amount of the homogeneous solution obtained in step two into a petri dish (7 cm in diameter) until the solution completely covers the bottom of the dish. Place the petri dish containing the mixture in a drying oven and dry it at 60°C until the solution is completely dry. Finally, peel the γ-glycine / PVA film directly from the petri dish.

[0051] performance:

[0052] The 2:1 γ-glycine / PVA thin film prepared by this method exhibits piezoelectric properties of 4.6–5.4 pC N. -1 The piezoelectric voltage coefficient is 200×10 -3 Vm N -1 XRD results show that its growth direction is

[101] (e.g. Figure 5 It exhibits characteristic peaks of the α phase.

[0053] Comparative Examples 2-3

[0054] The preparation process was the same as in Example 1, except that in step two, glycine and PVA solution were mixed in volume ratios of 0.5:1 (Comparative Example 2) and 3:1 (Comparative Example 3) to obtain a glycine / PVA solution. The performance results are shown in Table 1.

Claims

1. A method for preparing a γ-glycine / PVA thin film, characterized in that, The preparation method is as follows: first, glycine aqueous solution and PVA aqueous solution are stirred and mixed at 80-100℃ to obtain a blend; then, the blend is dried to form a composite film, and ultrasonic treatment is introduced during the drying process, with the ultrasonic treatment frequency being 0.1-2 MHz; finally, the dried film is peeled off to obtain the γ-glycine / PVA film; wherein, the volume ratio of glycine aqueous solution to PVA aqueous solution is 1-2:

1.

2. The method for preparing a γ-glycine / PVA thin film according to claim 1, characterized in that, The drying temperature is 50–60°C.

3. A γ-glycine / PVA film, characterized in that, The thin film is prepared by the preparation method described in claim 1 or 2.

4. The γ-glycine / PVA film according to claim 3, characterized in that, The γ-glycine / PVA film has a sandwich structure, with γ-glycine encapsulated in the middle by PVA.

5. The γ-glycine / PVA film according to claim 3, characterized in that, The piezoelectric properties of the γ-glycine / PVA film are 5.4±0.5~10.4±0.5 pC N. -1 ; The piezoelectric voltage coefficient of the γ-glycine / PVA film is 201 × 10⁻⁶. -3 ~300×10 -3 Vm N -1 .

6. Use of the γ-glycine / PVA thin film prepared by the method of claim 1 or 2 in wireless detection or sensors.

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