Ion piezoelectric flexible sensor based on polyionic liquid and preparation method and application thereof

Abstract

The invention discloses an ionic piezoelectric flexible sensor based on polyion liquid and a preparation method and application thereof.The sensor comprises a polyion piezoelectric sensitive layer, a gallium-based liquid metal layer, a copper electrode and a flexible wrapping layer.The polyion piezoelectric sensitive layer is prepared by conducting photocuring on an imidazolyl polyion liquid piezoelectric material; positive ions are fixed, and negative ions are movable. When the upper side and the lower side of the ion piezoelectric flexible sensor are stressed, positive ions in the sensitive layer are fixed, negative ions move towards a non-compression area, the gallium-based liquid metal electrode can promote the transmission speed of ions on an interface, and finally the ion piezoelectric flexible sensor which does not leak electrolyte and is high in piezoelectric performance is formed. And a new method is provided for preparation of the ion piezoelectric sensor. According to the ion piezoelectric flexible sensor based on the polyion liquid, the voltage signal reaches 200mv at 110N, the response range of ion piezoelectricity reaches up to 110N, and the ion piezoelectric flexible sensor can be applied to respiration monitoring and human motion monitoring under the condition of no power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric materials, and in particular to an ionic piezoelectric flexible sensor based on polyionic liquid and a preparation method and application thereof. Background Art

[0002] Piezoelectric materials play a key role in converting mechanical energy into electrical energy, and are essential for energy harvesting and human-machine interaction in ionic electronic systems. Unlike the electronic conduction mechanism of traditional conductors, the electronic conduction mechanism of ion gels is ionic conduction. Ion gels produce a voltage output when an ion concentration gradient is induced under applied pressure. Ionic piezoelectric materials use the generated mobile ions to carry signals to produce piezoelectric effects, and do not require polarization. PVDF piezoelectric materials require high-voltage polarization, and the preparation of these materials is often accompanied by problems such as high energy consumption and secondary processing. Unlike the charges generated by piezoelectric or triboelectric effects, ionic piezoelectric materials are very similar to biological sensing processes, so ionic piezoelectric materials can achieve seamless integration with biological systems. In addition, recent advances in the study of ionic liquids have shown that they have ionic conductivity comparable to many organic electrolytes and extremely high boiling points (up to 300-400°C). These unique properties make ionic piezoelectric materials promising candidates for piezoelectric sensing applications.

[0003] Although ionic piezoelectric materials have been used for sensing in recent years, the signal output still faces low output values ​​and may be affected by bioelectricity or other charged objects in practical applications. The key to improving piezoelectric performance is to increase the difference in the mobility of anions and cations. The existing technology is to add electrolytes of mobile ions to polymer soft materials, and the migration of anions and cations under stress is different, thereby achieving an unbalanced ion distribution between symmetrical electrodes, so that the sensor generates a voltage signal without an additional power supply. The researchers used high-resolution stereolithography (SLA) 3D printing to stack hydrogels to achieve improved piezoelectric performance. The piezoelectric performance of ionic polyacrylamide (PAAm) hydrogels can reach 70mv. The researchers used polyvinyl alcohol and ionic liquids to prepare ionic gels, and the voltage can reach 2.11mv, but the electrolyte is a liquid solution leakage. However, the current ionic gel piezoelectric materials have problems such as electrolyte leakage and low ion voltage. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an ionic piezoelectric flexible sensor based on polyionic liquid and a preparation method thereof, wherein the imidazolyl ionic liquid containing vinyl groups is polymerized by photopolymerization to achieve cation fixation and anion mobility, and finally form an ionic piezoelectric flexible sensor based on polyionic liquid with no electrolyte leakage and strong piezoelectric performance. The ionic piezoelectric flexible sensor based on polyionic liquid achieves high voltage response and wide range response.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] First, an ion piezoelectric flexible sensor based on polyion liquid is provided, wherein the ion piezoelectric flexible sensor based on polyion liquid comprises a polyion piezoelectric sensitive layer, a gallium-based liquid metal layer arranged on both sides of the polyion piezoelectric sensitive layer, a copper electrode arranged on the gallium-based liquid metal layer, and a flexible wrapping layer, wherein the polyion piezoelectric sensitive layer is made of the imidazole-based polyion liquid piezoelectric material.

[0007] Furthermore, the flexible wrapping layer is obtained by packaging with medical polyurethane film tape or polyimide film.

[0008] Furthermore, the thickness of the polyion piezoelectric sensitive layer is 0.5-2 mm; the thickness of the gallium-based liquid metal layer is 50-100 μm.

[0009] Secondly, a method for preparing the above-mentioned polyionic liquid-based ionic piezoelectric flexible sensor is provided, comprising the following preparation steps:

[0010] (1) dissolving a vinyl imidazole salt monomer and a photoinitiator in an appropriate amount of ethanol solution, and uniformly dispersing them by ultrasonication to obtain a precursor solution of a polyionic liquid;

[0011] (2) transferring the precursor solution to a mold, drying it, vacuum defoaming it, and then transferring it to a UV lamp for photocuring to obtain a polyionic liquid piezoelectric material;

[0012] (3) The polyion liquid piezoelectric material is plasma treated to form a polyion piezoelectric sensitive layer, and then a gallium-based liquid metal is coated on the upper and lower surfaces of the polyion piezoelectric sensitive layer to form a gallium-based liquid metal layer. Then, a copper electrode is attached to the gallium-based liquid metal layer, and finally, it is packaged with a medical polyurethane film tape or a polyimide film to obtain an ion piezoelectric flexible sensor based on polyion liquid.

[0013] Furthermore, the vinyl imidazole-based monomer is at least one of 1-vinyl-3-ethyl imidazole tetrafluoroborate, 1-vinyl-3-ethyl imidazole bromide, and 1-vinyl-3-ethyl imidazole chloride.

[0014] Furthermore, the photoinitiator is one of 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0015] Furthermore, the amount of the initiator used is 0.1-1 wt.% of the amount of the vinyl imidazole salt monomer used.

[0016] Furthermore, the frequency of the ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 5-10 min.

[0017] Furthermore, the power of the ultraviolet lamp is 200-300W, the wavelength is 365nm, and the light curing time is 3-15min.

[0018] The beneficial effects of the present invention are:

[0019] The ionic piezoelectric flexible sensor based on polyionic liquid of the present invention fixes cations on the molecular chain of polyionic liquid through the polyionic piezoelectric sensitive layer, and the anions are movable, so as to improve the difference in the mobility of anions and cations, thereby forming an unbalanced ion distribution between symmetrical electrodes, so that the sensor generates a high piezoelectric signal; the gallium-based liquid metal electrode can reduce the interface resistance between the electrode and the polyionic liquid, increase the ion transfer speed, and thus form a large voltage signal on both sides of the electrode. The ionic piezoelectric flexible sensor based on polyionic liquid has a voltage signal of 200mv at 110N, and the ionic piezoelectric response range is as high as 110N, achieving high voltage response and wide range response range, and can be applied to respiratory monitoring and human motion monitoring without power supply, and has potential application value in self-powered sensing.

[0020] The ionic piezoelectric flexible sensor based on polyionic liquid of the present invention polymerizes the imidazolyl ionic liquid containing vinyl by photopolymerization. When the ionic piezoelectric material is subjected to force up and down, the mobility of the fixed cations and the dissociated anions is very different, so the ion concentration difference is formed on both sides of the ionic gel electrode to generate a voltage difference. The present invention realizes ionic voltage breakthrough by using polyionic liquid with fixed cations, and finally forms a polymer piezoelectric material with no electrolyte leakage and strong piezoelectric performance. Its electrical signal increases with the increase of force, providing a new method for the preparation of ionic voltage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 , a schematic diagram of the preparation process of the polyionic liquid piezoelectric material of the present invention;

[0022] Figure 2 , a schematic diagram of the mechanism of the ionic piezoelectric flexible sensor based on polyionic liquid of the present invention;

[0023] Figure 3 , the piezoelectric signal of the ionic piezoelectric flexible sensor based on polyionic liquid obtained in Example 1 of the present invention;

[0024] Figure 4 , the piezoelectric signal of the ionic piezoelectric flexible sensor based on polyionic liquid obtained in Example 2 of the present invention;

[0025] Figure 5 , the piezoelectric signal of the ionic piezoelectric flexible sensor based on polyionic liquid obtained in Example 3 of the present invention;

[0026] Figure 6 , infrared spectrum of the polyionic liquid piezoelectric material obtained in Example 3 of the present invention;

[0027] Figure 7 , the force-voltage relationship of the ionic piezoelectric flexible sensor based on polyionic liquid obtained in Example 3 of the present invention;

[0028] Figure 8 , the variable pressure infrared spectrum of the polyionic liquid piezoelectric material obtained in Example 3 of the present invention;

[0029] Fig. 9 , thermal stability curve of the polyionic liquid piezoelectric material obtained in Example 3 of the present invention;

[0030] Fig.10 , the application of the ionic piezoelectric flexible sensor based on polyionic liquid prepared in Example 3 of the present invention on finger pressing;

[0031] Fig.11 , Application of the ionic piezoelectric flexible sensor based on polyionic liquid prepared in Example 3 of the present invention in breathing detection;

[0032] Fig.12 , a physical picture of the ionic piezoelectric flexible sensor based on polyionic liquid prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0033] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the claims of the present invention. The reagents or instruments used in the present invention without indicating the manufacturer are all conventional products that can be purchased commercially.

[0034] Example 1

[0035] A method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid comprises the following preparation steps:

[0036] (1) 2.4 g of 1-vinyl-3-ethylimidazolium tetrafluoroborate and 0.024 g of 2-hydroxy-2-methylpropiophenone initiator were stirred and mixed uniformly, and then ultrasonically dispersed for 10 min at a frequency of 40 kHz to obtain a precursor solution of a polyionic liquid;

[0037] (2) pouring the precursor solution obtained in step (1) into a mold, and then placing it in a vacuum box, and letting it stand for 1 hour under a vacuum degree of 0.1 kPa to eliminate bubbles in the solution;

[0038] (3) transferring the sample obtained in step (2) to a 200 W ultraviolet lamp (365 nm) for photocuring, the ultraviolet lamp being 10 cm above the sample, and curing for 5 min to obtain an imidazole-based polyionic liquid piezoelectric material with a thickness of 1 mm;

[0039] (4) After the polyion liquid piezoelectric material is plasma treated for 5 minutes, a polyion piezoelectric sensitive layer is obtained; a gallium-based liquid metal with a thickness of 100 μm is coated on the upper and lower surfaces of the polyion piezoelectric sensitive layer to form a gallium-based liquid metal layer, and then a copper electrode is attached to the gallium-based liquid metal layer, and finally it is encapsulated with a polyimide film to obtain an ion piezoelectric flexible sensor based on polyion liquid, sample number 1#.

[0040] Apply pressure to one side of the electrode and collect its voltage signal with an electrometer. The test results are shown in Figure 3. Figure 3 It can be seen that the voltage signal of the ionic piezoelectric flexible sensor based on polyionic liquid increases with the increase of force, and the ionic piezoelectric response range is 30-110N. In particular, the voltage signal reaches 0.5mv at 110N. This is because the tetrafluoroborate is unevenly distributed on the upper and lower electrodes under pressure, generating an ionic voltage signal. The schematic diagram of the ionic voltage signal generation is shown in Figure 2 shown.

[0041] Example 2

[0042] A method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid comprises the following preparation steps:

[0043] (1) Dissolve 2.4 g of 1-vinyl-3-ethylimidazolium chloride in 4.8 ml of alcohol and stir well; then add 0.024 g of initiator 2-hydroxy-2-methylpropiophenone and disperse by ultrasonication for 10 min at a frequency of 40 kHz to obtain a precursor solution of a polyionic liquid;

[0044] (2) pouring the precursor solution obtained in step (1) into a mold, placing it in an oven at 50° C. and drying it for 8 h to evaporate the solvent; then transferring it to a vacuum box and leaving it at a vacuum degree of 0.1 kPa for 2 h to eliminate bubbles in the solution;

[0045] (3) transferring the sample obtained in step (2) to a 300 W ultraviolet lamp (365 nm) for photocuring, the ultraviolet lamp was 10 cm away from the sample, and the curing was performed for 8 min to obtain an imidazole-based polyionic liquid piezoelectric material with a thickness of 1 mm;

[0046] (4) After the polyion liquid piezoelectric material is plasma treated for 5 minutes, a polyion piezoelectric sensitive layer is obtained; a gallium-based liquid metal with a thickness of 100 μm is coated on the upper and lower surfaces of the polyion piezoelectric sensitive layer to form a gallium-based liquid metal layer, and then a copper electrode is attached to the gallium-based liquid metal layer, and finally it is encapsulated with a polyimide film to obtain an ion piezoelectric flexible sensor based on polyion liquid, sample number 2#.

[0047] Apply pressure to one side of the electrode and collect its voltage signal with an electrometer. The test results are as follows: Figure 4 As shown. Figure 4 It can be seen that the voltage signal of the ionic piezoelectric flexible sensor based on polyionic liquid increases with the increase of force, and changes little within the range of 30-80N. At 110N, the voltage signal reaches 0.9mv. The schematic diagram of the ionic voltage signal generation is shown in Figure 2 shown.

[0048] Example 3

[0049] A method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid comprises the following preparation steps:

[0050] (1) 2.4 g of 1-vinyl-3-ethylimidazolium bromide, 0.024 g of 2-hydroxy-2-methylpropiophenone initiator and 4.8 ml of alcohol were ultrasonically dispersed for 10 min at a frequency of 40 kHz to obtain a precursor solution of a polyionic liquid;

[0051] (2) pouring the precursor solution obtained in step (1) into a polytetrafluoroethylene mold, drying in an oven at 50° C. for 8 h to evaporate the solvent; then transferring to a vacuum box, and standing for 2 h at a vacuum degree of 0.1 kPa to eliminate bubbles in the solution;

[0052] (3) transferring the sample obtained in step (2) to a 300 W ultraviolet lamp (365 nm) for photocuring, the ultraviolet lamp being 10 cm above the sample, and curing for 5 min to obtain an imidazole-based polyionic liquid piezoelectric material with a thickness of 1 mm;

[0053] (4) After the polyion liquid piezoelectric material is plasma treated for 5 minutes, a polyion piezoelectric sensitive layer is obtained; a gallium-based liquid metal with a thickness of 100 μm is coated on the upper and lower surfaces of the polyion piezoelectric sensitive layer to form a gallium-based liquid metal layer, and then a copper electrode is attached to the gallium-based liquid metal layer, and finally it is encapsulated with a polyimide film to obtain an ion piezoelectric flexible sensor based on polyion liquid, sample number 3#.

[0054] Apply pressure to one side of the electrode and collect its voltage signal with an electrometer. The result is as follows: Figure 5The electrical signal of the polyionic liquid-based ionic piezoelectric flexible sensor prepared by the present invention increases with the increase of force. The voltage signal reaches 200mv at 110N. The response range of ionic piezoelectricity is as high as 110N, which is far beyond the performance of existing ionic piezoelectric materials. The schematic diagram of the ionic voltage signal generation is shown in Figure 2 shown.

[0055] Figure 6 This is the infrared spectrum of the polyionic liquid piezoelectric material prepared in Example 3. Figure 6 As shown, 1658cm -1 and 3158cm -1 They correspond to the C=C double bond and =CH in 1-vinyl-3-ethylimidazolium bromide. 2 -, while the characteristic peak corresponding to the carbon-carbon double bond in the polyionic liquid disappears after photocuring. Figure 5 The test results show that the ionic liquid of imidazolium bromide has completed polymerization.

[0056] like Figure 7 As shown, during the test of the polyionic liquid-based ionic piezoelectric flexible sensor prepared in Example 3, when the force reaches the required value, the force load is maintained for 0.5s, and then the force load is repeatedly applied. Figure 7 It can be seen that the peak of the voltage signal is synchronized with the peak of the force curve and there is no phase difference, indicating that the voltage signal is not generated by the friction electricity of the material, but by the uneven distribution of anions and cations.

[0057] Figure 8 This is the variable pressure infrared spectrum of the polyionic liquid piezoelectric material prepared in Example 3. Figure 8 It can be seen that with the increase of applied force, the stretching vibration peak of the CH bond of the imidazole ring (2850cm -1 ) The peak intensity decreases with the increase of pressure, and there is basically no change after 200 kPa. The variable pressure infrared results show that the ion movement rate of the piezoelectric material increases in the range of 0-200 kPa (corresponding to a force of 110 N), while the peak intensity of the imidazole ring CH bond stretching decreases.

[0058] The thermogravimetric curve of the polyionic liquid piezoelectric material prepared in Example 3 is as follows: Fig. 9 As shown, the mass of the sample begins to change at 300°C, indicating that the prepared sample has good thermal stability and can meet the needs of most usage scenarios.

[0059] like Fig.10 As shown, taking the ionic piezoelectric flexible sensor based on polyionic liquid prepared in implementation 3 as an example, the ionic piezoelectric flexible sensor is used in a finger pressing application experiment, and the sensor can well distinguish the force of the finger pressing; as shown Fig.11As shown, the polyionic liquid-based ionic piezoelectric flexible sensor can also be used for human breathing detection, and can well distinguish breathing patterns, such as normal breathing, rapid breathing, and holding the breath.

[0060] According to the disclosure of the above description, those skilled in the art to which the present invention belongs may also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. An ionic piezoelectric flexible sensor based on polyionic liquid, characterized in that: The polyion liquid-based ion piezoelectric flexible sensor includes a polyion piezoelectric sensitive layer, a gallium-based liquid metal layer arranged on both sides of the polyion piezoelectric sensitive layer, a copper electrode arranged on the gallium-based liquid metal layer, and a flexible wrapping layer. The polyion piezoelectric sensitive layer is made of the imidazole-based polyion liquid piezoelectric material.

2. The polyionic liquid-based ionic piezoelectric flexible sensor according to claim 1, characterized in that: The flexible wrapping layer is obtained by packaging with a medical polyurethane film tape or a polyimide film.

3. The ionic piezoelectric flexible sensor based on polyionic liquid according to claim 1, characterized in that: The thickness of the polyion piezoelectric sensitive layer is 0.5-2 mm; the thickness of the gallium-based liquid metal layer is 50-100 μm.

4. A method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid according to any one of claims 1 to 3, characterized in that: The method comprises the following preparation steps: (1) dissolving a vinyl imidazole salt monomer and a photoinitiator in an appropriate amount of ethanol solution, and uniformly dispersing them by ultrasonication to obtain a precursor solution of a polyionic liquid; (2) transferring the precursor solution to a mold, drying it, vacuum defoaming it, and then transferring it to a UV lamp for photocuring to obtain a polyionic liquid piezoelectric material; (3) The polyion liquid piezoelectric material is plasma treated to form a polyion piezoelectric sensitive layer, and then a gallium-based liquid metal is coated on the upper and lower surfaces of the polyion piezoelectric sensitive layer to form a gallium-based liquid metal layer. Then, a copper electrode is attached to the gallium-based liquid metal layer, and finally, a flexible wrapping layer is used for packaging to obtain an ion piezoelectric flexible sensor based on polyion liquid.

5. The method for preparing the polyionic liquid-based ionic piezoelectric flexible sensor according to claim 4, characterized in that: The vinyl imidazole-based monomer is at least one of 1-vinyl-3-ethyl imidazole tetrafluoroborate, 1-vinyl-3-ethyl imidazole bromide, and 1-vinyl-3-ethyl imidazole chloride.

6. The method for preparing the polyionic liquid-based ionic piezoelectric flexible sensor according to claim 4, characterized in that: The photoinitiator is one of 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

7. The method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid according to claim 4, characterized in that: The amount of the initiator used is 0.1-1 wt.% of the amount of the vinyl imidazole salt monomer used.

8. The method for preparing an ionic piezoelectric flexible sensor based on polyionic liquid according to claim 4, characterized in that: The frequency of the ultrasonic dispersion is 40 kHz, and the ultrasonic dispersion time is 5-10 min.

9. The method for preparing the polyionic liquid-based ionic piezoelectric flexible sensor according to claim 4, characterized in that: The power of the ultraviolet lamp is 200-300W, the wavelength is 365nm, and the light curing time is 3-15min.

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