A flexible and stretchable ferroelectric electret and its preparation method

Abstract

This invention discloses a flexible and stretchable ferroelectric electret and its preparation method, belonging to the field of flexible electronics technology. The ferroelectric electret prepared by this invention can generate electricity due to its unique porous structure, without requiring additional power-generating materials, exhibiting good power generation performance and promising research prospects. It has broad application markets in smart wearables, health monitoring, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronics technology, specifically relating to a flexible stretchable ferroelectric electret and its preparation method. Background Technology

[0002] Ferroelectric electrets are innovative artificial microstructured functional materials with porous structures that exhibit significant piezoelectric effects. Unlike traditional piezoelectric materials with spontaneous polarization, ferroelectric electrets are charged and polarized through internal pores. The charged porous structure of ferroelectric electrets combines the high piezoelectricity of inorganic piezoelectric compounds (such as piezoelectric ceramics) with the flexible thin-film structure of organic piezoelectric polymers. This unique structure also enhances the ferroelectric electret's sensitivity to forces and its ability to effectively store charge. Ferroelectric electrets also possess advantages such as ultrathinness, ultralight weight, flexibility, and low acoustic impedance, while also being capable of large-area film deposition. These advantages make ferroelectric electrets promising for broad applications in wearable devices, health monitoring, and ultrasonic transducers.

[0003] Common methods for preparing ferroelectric electrets are relatively complex. For example, a typical method involves high-pressure gas injection combined with inorganic microparticle processing. Other common methods include foaming techniques, sandwich structures, and micro-image processing.

[0004] Polydimethylsiloxane (PDMS) is a high molecular weight polymer with the chemical formula (C2H6OSi)n. It is stable, colorless and odorless, with low toxicity, low water absorption, good radiation resistance and excellent electrical properties, making it suitable for preparing high-performance ferroelectric electrets.

[0005] The main charging methods for ferroelectric electrets include corona charging, contact charging, soft X-ray irradiation, and electron beam injection. Under high voltage, the top and bottom surfaces of the pores in the ferroelectric electret can acquire a large number of charges of opposite polarity, thus producing a piezoelectric phenomenon. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a flexible and stretchable ferroelectric electret.

[0009] To address the problems of poor piezoelectricity and complex preparation process of traditional ferroelectric electrets, this invention provides the following improvement schemes, including adding anhydrous ethanol to increase the number of pores to enhance piezoelectricity, and high-temperature preheating to prevent pore overflow.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including,

[0011] Polydimethylsiloxane prepolymer is mixed evenly with curing agent to obtain polydimethylsiloxane. Anhydrous ethanol is added and stirred thoroughly to form a mixed material. The mixed material is first heated at high temperature and then cured at low temperature. Then, it is subjected to high-voltage polarization to obtain ferroelectric electret.

[0012] In a preferred embodiment of the method for preparing the flexible and stretchable ferroelectric electret of the present invention, the curing agent includes one or more of siloxanes, silicones, dimethyl groups, and hydromethyl groups.

[0013] In a preferred embodiment of the preparation method of the flexible stretchable ferroelectric electret of the present invention, the mass ratio of the prepolymer of polydimethylsiloxane to the curing agent is 5 to 10:1.

[0014] In a preferred embodiment of the preparation method of the flexible and stretchable ferroelectric electret of the present invention, the content of anhydrous ethanol is 5% to 20% of the mass of polydimethylsiloxane.

[0015] In a preferred embodiment of the method for preparing the flexible and stretchable ferroelectric electret of the present invention, the stirring is carried out at a speed of 1000-2000 rpm for a duration of 40-120 s.

[0016] In a preferred embodiment of the method for preparing the flexible and stretchable ferroelectric electret of the present invention, the high-temperature heating temperature is 200-300°C and the time is 1-20 seconds.

[0017] In a preferred embodiment of the preparation method of the flexible and stretchable ferroelectric electret of the present invention, the low-temperature curing temperature is 80-150°C and the time is 5-10 min.

[0018] In a preferred embodiment of the method for preparing the flexible and stretchable ferroelectric electret of the present invention, the polarization is corona polarization, performed under inert gas or vacuum conditions.

[0019] In a preferred embodiment of the method for preparing the flexible and stretchable ferroelectric electret of the present invention, the polarization voltage is -15 to -25 kV, the polarization height is 3 to 5 cm, and the polarization time is 3 to 10 min.

[0020] Another objective of this invention is to overcome the shortcomings of the prior art and provide a flexible and stretchable ferroelectric electret.

[0021] Beneficial effects of this invention:

[0022] (1) The ferroelectric electret prepared by this invention can generate electricity due to its special porous structure, without the need for additional power generation materials, and has good power generation effect, thus having good research and application prospects.

[0023] (2) The ferroelectric electret prepared by the present invention has flexible and stretchable properties and has a wide range of applications in smart wearables, health monitoring and other fields.

[0024] (3) The ferroelectric electret prepared by the present invention has a simple preparation process and has the potential to be commercialized. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 This is a stress-strain curve of the ferroelectric electret obtained in Example 1 of the present invention.

[0027] Figure 2 This is a stress-strain curve of the ferroelectric electret obtained in Comparative Example 1 of the present invention.

[0028] Figure 3 A schematic diagram illustrating the basic power generation principle provided by this invention. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0032] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0033] The materials obtained in the embodiments of the present invention were subjected to performance testing according to the following method:

[0034] The stress-strain curve was measured and the Young's modulus was calculated using a tensile testing machine (KZ-SSBC-500 universal testing machine).

[0035] The static piezoelectric coefficient d was measured using a charge amplifier (AFT-0966C) and a data acquisition card (Virtins DS0-2820). 33 .

[0036] In the static piezoelectric coefficient d 33 During the measurement, an initial force of F = 0.5 N was applied to the sample surface, followed by a force of F = 5 N, which was then rapidly released. The charge amplifier (AFT-0966C) and data acquisition card (Virtins DS0-2820) recorded the subsequent charge Q. Throughout the experiment, a static force of 0.5 N was maintained on the sample surface to prevent interference signals from being generated when the force was released from the electrode surface. The charge was then calculated using formula d. 33 =Q / F yields the static piezoelectric coefficient.

[0037] Example 1

[0038] This embodiment provides a method for preparing a flexible and stretchable ferroelectric electret, specifically as follows:

[0039] PDMS (Dow Corning DC184) was obtained by mixing the prepolymer of PDMS with the curing agent at a ratio of 10:1. Then, 15% anhydrous ethanol by weight of PDMS was added and stirred at 1500 rpm for 80 seconds to fully mix and form a mixed material.

[0040] The mixed material is first heated to 250℃ for 5 seconds, then cured at 150℃ for 5 minutes.

[0041] Ferroelectric electrets were obtained by polarizing at a polarization height of 4 cm and a high voltage of -16 kV for 5 min.

[0042] Figure 1 The stress-strain curve of the FENG prepared for this embodiment shows that its Young's modulus is about 0.4 MPa, the material is easy to deform and has good flexibility, which proves that it has good tensile properties.

[0043] Example 2

[0044] The difference between this embodiment and Example 1 is that the content of anhydrous ethanol is adjusted to 5%, while the rest of the preparation process is the same as in Example 1, and a ferroelectric electret is obtained.

[0045] Example 3

[0046] The difference between this embodiment and Example 1 is that the content of anhydrous ethanol is adjusted to 20%, while the rest of the preparation process is the same as in Example 1, to obtain a ferroelectric electret.

[0047] The performance of the materials prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 1.

[0048] Table 1

[0049] Example 1 Example 2 Example 3 Anhydrous ethanol content (%) 15 5 20 <![CDATA[d 33 (pC / N)]]> 160 60 80 Young's modulus (MPa) 0.46 0.42 0.40

[0050] As shown in the table above, adjusting the content of anhydrous ethanol has little effect on the Young's model of the ferroelectric electret, but a significant effect on the static piezoelectric coefficient. This is because anhydrous ethanol is highly volatile. When the mixture of anhydrous ethanol and PDMS is heated to solidification, the anhydrous ethanol evaporates, forming numerous pores that adjust the structure and morphology of PDMS. The number and size of these pores are related to the anhydrous ethanol content and the curing temperature. The more pores, the stronger the charge storage capacity, and the larger the piezoelectric coefficient obtained after polarization. When the anhydrous ethanol content is too low, the number of pores is too small, resulting in a weakened polarization effect; when the content is too high, it affects the curing and polarization process of PDMS, causing a decrease in the performance of the ferroelectric electret. According to the results in the table above, the optimal technical effect can be obtained when the anhydrous ethanol content in this invention is 15%.

[0051] Example 4

[0052] The difference between this embodiment and Embodiment 1 is that the polarization voltage is adjusted to -15kV, while the rest of the preparation process is the same as in Embodiment 1, and a ferroelectric electret is obtained.

[0053] Example 5

[0054] The difference between this embodiment and Embodiment 1 is that the polarization voltage is adjusted to -25kV, while the rest of the preparation process is the same as in Embodiment 1, to obtain a ferroelectric electret.

[0055] The performance of the materials prepared in the above embodiments was tested, and the results compared with those of Example 1 are shown in Table 2.

[0056] Table 2

[0057] Example 1 Example 4 Example 5 Polarization voltage (kV) -16 -15 -25 <![CDATA[d 33 (pC / N)]]> 160 120 110 Young's modulus (MPa) 0.40 0.40 0.40

[0058] As shown in the table above, adjusting the polarization voltage has a significant impact on the performance of the ferroelectric electret. This is because the charge generated by polarization directly affects the magnitude of the piezoelectric effect. Adjusting the polarization voltage affects the polarization intensity and direction of the ferroelectric electret. When the polarization voltage is too low, incomplete polarization may occur; when the polarization voltage is too high, it may exceed the material's tolerance range, leading to changes in the electret structure. According to the results in the table above, the optimal technical effect is achieved when the polarization voltage in this invention is -16kV.

[0059] Example 6

[0060] The difference between this embodiment and Embodiment 1 is that the high-temperature heating temperature is adjusted to 200°C, while the rest of the preparation process is the same as in Embodiment 1, and a ferroelectric electret is obtained.

[0061] Example 7

[0062] The difference between this embodiment and Embodiment 1 is that the high-temperature heating temperature is adjusted to 300°C, while the rest of the preparation process is the same as in Embodiment 1, and a ferroelectric electret is obtained.

[0063] The performance of the materials prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 3.

[0064] Table 3

[0065]

[0066]

[0067] As shown in the table above, adjusting the high-temperature heating temperature has a significant impact on the performance of the ferroelectric electret. This is because adjusting the high-temperature heating temperature affects the curing degree and structure of PDMS, thus affecting the performance of the electret. Excessively high heating temperatures may cause PDMS molecular chains to break or become over-crosslinked, thereby affecting the polarization effect and mechanical properties of the electret. Conversely, excessively low heating temperatures may result in poor high-temperature preheating, leading to bubble overflow during the subsequent low-temperature curing process, a decrease in the porosity of the electret, and a reduction in the piezoelectric coefficient. Based on the results in the table, the optimal technical effect is achieved when the high-temperature heating temperature in this invention is 250℃.

[0068] Example 8

[0069] The difference between this embodiment and Embodiment 1 is that the high-temperature heating time is adjusted to 1 second, while the rest of the preparation process is the same as in Embodiment 1, and a ferroelectric electret is obtained.

[0070] Example 9

[0071] The difference between this embodiment and Embodiment 1 is that the high-temperature heating time is adjusted to 20 seconds, while the rest of the preparation process is the same as in Embodiment 1, and a ferroelectric electret is obtained.

[0072] The performance of the materials prepared in the above embodiments was tested, and the comparison results with those of Example 1 are shown in Table 4.

[0073] Table 4

[0074] Example 1 Example 8 Example 9 Heating time (s) 5 1 20 <![CDATA[d 33 (pC / N)]]> 160 120 100 Young's modulus (MPa) 0.40 0.43 0.41

[0075] As shown in the table above, adjusting the high-temperature heating time has a significant impact on the performance of the ferroelectric electret. This is because adjusting the high-temperature heating time affects the curing degree and structure of PDMS, thus affecting the performance of the electret. Too short a heating time may result in poor high-temperature preheating, causing bubbles to overflow during the subsequent low-temperature curing process, reducing the porosity of the electret, and leading to unsatisfactory polarization. Conversely, too long a heating time may cause the molecular chains of PDMS to break or thermally decompose, thereby affecting the mechanical and electrical properties of the electret. According to the results in the table above, a high-temperature heating time of 5 seconds in this invention achieves the best technical effect.

[0076] Comparative Example 1

[0077] This comparative example provides a conventional method for preparing ferroelectric electrets, specifically as follows:

[0078] The first step involves mixing polyurethane (PU) with a curing agent, toluene diisocyanate-trimethylolpropane (TDI-TMP) adduct, at a 1:1 ratio. The second step involves curing the mixture at 80°C for 10 minutes. The third step involves polarizing the mixture at a polarization height of 4 cm under a -16 kV high voltage for 5 minutes to obtain a ferroelectric electret.

[0079] Comparative Example 2

[0080] The difference between this comparative example and Example 1 is that anhydrous ethanol is not added, but the rest of the preparation process is the same as in Example 1, and a ferroelectric electret is obtained.

[0081] Comparative Example 3

[0082] The difference between this comparative example and Example 1 is that no high-temperature heating is added, but the rest of the preparation process is the same as in Example 1, and a ferroelectric electret is obtained.

[0083] The performance of the materials prepared in the above comparative example was tested, and the results compared with those of Example 1 are shown in Table 5.

[0084] Table 5

[0085] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[d 33 (pC / N)]]> 160 20 50 100 Young's modulus (MPa) 0.40 38 0.42 0.45

[0086] As can be seen from the table above, compared with polyurethane, the flexible stretchable ferroelectric electret prepared by this invention has better piezoelectricity and lower Young's modulus. Furthermore, the improvement schemes provided by this invention, including the addition of anhydrous ethanol and high-temperature preheating, have significant effects on improving piezoelectricity. This preparation method has broad application prospects.

[0087] Figure 3 This is a schematic diagram illustrating the basic power generation principle provided by this invention. The piezoelectric effect of a ferroelectric electret originates from the change in macroscopic electric dipoles on its internal holes. Within the pores of the ferroelectric electret, a large number of charges are trapped on the top and bottom surfaces. These charges have opposite polarities, forming a giant permanent dipole in engineering. When subjected to mechanical stress or strain, the pores within the ferroelectric electret deform, causing a redistribution of charges and a change in the dipole moment. This change results in a potential difference across the thin film, ultimately leading to the macroscopic piezoelectric effect.

[0088] The ferroelectric electret prepared by this invention can generate electricity due to its special porous structure, without the need for additional power generation materials, and has good power generation effect, showing good research and application prospects.

[0089] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a flexible and stretchable ferroelectric electret, characterized in that: include, Polydimethylsiloxane prepolymer is mixed evenly with curing agent to obtain polydimethylsiloxane. Anhydrous ethanol is added and stirred thoroughly to form a mixed material. The mixed material is first heated at high temperature and then cured at low temperature. Then it is subjected to high-voltage polarization to obtain ferroelectric electret. The amount of anhydrous ethanol added is 5% to 20% of the mass of polydimethylsiloxane; The high-temperature heating temperature is 200~300℃, and the time is 1~20s; The low-temperature curing temperature is 80~150℃, and the time is 5~10min; The high-voltage polarization has a polarization voltage of −15 to −25 kV, a polarization height of 3 to 5 cm, and a polarization time of 3 to 10 min.

2. The method for preparing the flexible and stretchable ferroelectric electret as described in claim 1, characterized in that: The curing agent includes one or more of siloxanes, silicones, dimethyl, and hydromethyl.

3. The method for preparing the flexible and stretchable ferroelectric electret as described in claim 1, characterized in that: The mass ratio of the prepolymer of the polydimethylsiloxane to the curing agent is 5~10:

1.

4. The method for preparing the flexible and stretchable ferroelectric electret as described in claim 1, characterized in that: The stirring is carried out at a speed of 1000-2000 rpm for a duration of 40-120 seconds.

5. The method for preparing the flexible and stretchable ferroelectric electret as described in claim 1, characterized in that: The polarization method is corona polarization, performed under inert gas or vacuum conditions.

6. A flexible, stretchable ferroelectric electret prepared by the method described in any one of claims 1 to 5.

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