Flexible piezoelectric sensing composite film and preparation method thereof

Abstract

The invention provides a flexible piezoelectric sensing composite film and a preparation method thereof, and the preparation method comprises the following steps: S1, dispersing barium titanate into a buffer solution, then adding dopamine, and carrying out a reaction to obtain polydopamine modified barium titanate particles; s2, dispersing the polydopamine modified barium titanate particles in an organic solvent, adding polylactic acid, and stirring to obtain a spinning solution; s3, performing electrostatic spinning on the spinning solution to obtain the flexible piezoelectric sensing composite film. Polydopamine modified nano barium titanate is designed and is blended with polylactic acid, and the composite film is prepared through electrostatic spinning. Dopamine modification enables dispersibility and compatibility of barium titanate in a polylactic acid spinning solution to be greatly improved, and adverse effects caused by direct addition of nanoparticles into a polymer are effectively avoided. The piezoelectric current output and the mechanical property of the obtained composite film are improved, the pulse alternating current generated by circulating impact-release for 4000 seconds is stable and does not attenuate, and the requirement of long-term stable work is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of piezoelectric sensing materials and its preparation, and particularly relates to a flexible piezoelectric sensing composite film and a preparation method thereof. BACKGROUND

[0002] With the increasing pursuit of life quality, new technologies are emerging. Among them, the flexible electronic field is developing rapidly, and electronic products have greatly benefited human life, and have potential application prospects in the fields of electronic skin, human health monitoring, human-computer interaction, etc. The commonly used piezoelectric polymer is difficult to degrade and contains toxic substances, such as polyvinylidene fluoride, which will produce harmful gas hydrogen fluoride after degradation. In addition, polyimide, polyurethane, polyethylene terephthalate, and polydimethylsiloxane are all harmful to the environment and human beings. Therefore, flexible piezoelectric materials with green, efficient, biodegradable and good biocompatibility are the new development trend in the field of flexible electronics today.

[0003] Polylactic acid is a bio-based polymer derived from renewable resources, which can be decomposed into water and carbon dioxide. The large number of C=O dipoles in its polymer chain is the reason for its piezoelectricity. Electrospinning can promote the arrangement of dipoles in the polylactic acid chain, resulting in piezoelectricity. However, the piezoelectricity of pure polylactic acid fiber film is still low. Doping inorganic piezoelectric nanomaterials such as barium titanate and lead zirconate titanate with high piezoelectric coefficient in the polymer matrix makes its high piezoelectricity and polymer flexibility complementary. Among them, barium titanate is concerned due to its high piezoelectric coefficient, lead-free and low cost. However, the high surface energy of nanoparticles will cause aggregation problems, and there is an adverse interfacial interaction between the nanoparticles and the polymer matrix, leading to phase separation. After blending of nanoparticles and polymer matrix, the nanoparticles are not uniformly dispersed in the polymer matrix, increasing the internal defects of the composite material, inhibiting stress transfer, and weakening the electromechanical coupling efficiency and mechanical properties. SUMMARY

[0004] In order to solve the problem of poor electromechanical coupling efficiency and mechanical properties caused by the uneven dispersion of nanoparticles in the polymer matrix of the existing piezoelectric sensing material, the application provides a flexible piezoelectric sensing composite film and a preparation method thereof.

[0005] The application is implemented by the following technical solutions: In a first aspect, the application provides a preparation method of a flexible piezoelectric sensing composite film, comprising: S1, dispersing barium titanate into a buffer solution, then adding dopamine and reacting to obtain polydopamine modified barium titanate particles; S2, dispersing the polydopamine modified barium titanate particles in an organic solvent, adding polylactic acid and stirring to obtain a spinning solution; S3, electrospinning the spinning solution to obtain a flexible piezoelectric sensing composite film.

[0006] Preferably, the amount of barium titanate, dopamine and polylactic acid is 10-15 parts, 2-10 parts and 75-95 parts respectively by mass.

[0007] Preferably, in S1, the buffer is one of Tris-HCl buffer, Na2HPO4-NaCl buffer and Na2CO3-NaHCO3 buffer.

[0008] Preferably, in S1, the barium titanate is dispersed in the buffer, specifically, the barium titanate is added into the buffer and ultrasonic treatment is performed for 20-40 minutes.

[0009] Preferably, in S1, the reaction time is 12-30 hours.

[0010] Preferably, in S2, the organic solvent is one or a combination of chloroform, dichloromethane, N-methyl pyrrolidone and dimethylformamide.

[0011] Preferably, in S2, the polydopamine modified barium titanate particles are dispersed in the organic solvent, specifically, the polydopamine modified barium titanate particles are added into the organic solvent and ultrasonic treatment is performed for 40-80 minutes.

[0012] Preferably, in S2, the stirring time is 12-30 hours.

[0013] Preferably, in S2, the electrospinning parameters are as follows: flow rate 0.001-0.004 mm / s, voltage 12-24 V, receiving distance 12-20 cm and drum rotation speed 400-800 r / min.

[0014] In the second aspect, the application provides a flexible piezoelectric sensing composite film prepared by the above method, which comprises a polylactic acid matrix and polydopamine modified barium titanate dispersed in the polylactic acid matrix.

[0015] Compared with the prior art, the application has the following advantages: In order to prepare green piezoelectric nanocomposites with good piezoelectric properties and mechanical properties, the polydopamine modified nanobarium titanate is designed, and the polydopamine modified nanobarium titanate is blended with polylactic acid to prepare a composite film by electrospinning. The dispersibility and compatibility of the barium titanate in the polylactic acid spinning solution are greatly improved by the dopamine modification, and the adverse effects caused by directly adding nanoparticles into the polymer are effectively avoided. The piezoelectric current output and the mechanical property of the obtained composite film are improved, and the pulse alternating current generated by 4000 s of cyclic impact-release is stable and does not attenuate, which meets the demand of long-term stable operation. In addition, the composite film can be attached to multiple parts of the human body to realize sensitive recognition and monitoring of motion modes such as finger pressing / bending, walking / running, and the like, and can drive the red LED to emit light without other external power supply, which has wide potential in the field of motion wearable sensors.

[0016] Further, when the mass fraction of the polydopamine modified barium titanate is 10-15 parts, the piezoelectric and mechanical properties of the composite film reach the best value, the piezoelectric current output can reach 2 times of that of the polylactic acid and the unmodified barium titanate composite film, and 10 times of that of the pure polylactic acid film; the tensile breaking strength and tensile breaking elongation are also increased. DETAILED DESCRIPTION

[0017] The embodiments of the present application will be described in detail below with specific reference to specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0018] It should be understood that the process equipment or device not specifically mentioned in the following examples all uses the conventional equipment or device in the art.

[0019] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not a limitation on the arrangement order of each method step or a limitation on the range of implementation of the present application, and changes or adjustments of the relative relationship without substantial changes in the technical content are also regarded as the scope of implementation of the present application.

[0020] The preparation method of the flexible piezoelectric sensing composite film described in the present application comprises: S1, dispersing barium titanate into a buffer solution, then adding dopamine and reacting to obtain polydopamine modified barium titanate particles; S2, dispersing the polydopamine-modified barium titanate particles in an organic solvent, adding polylactic acid, stirring to obtain a spinning solution; S3, electrospinning the spinning solution to obtain a flexible piezoelectric sensing composite film.

[0021] In some embodiments of the present application, the amounts of barium titanate, dopamine and polylactic acid are 10-15 parts, 2-10 parts and 75-95 parts, respectively, in terms of mass fraction.

[0022] In some embodiments of the present application, in S1, the buffer is one of a tris-hydroxymethyl aminomethane hydrochloride buffer, a disodium hydrogen phosphate-sodium chloride buffer and a sodium carbonate-sodium bicarbonate buffer, which can provide a suitable alkaline environment for dopamine polymerization and maintain the stability of the solution pH.

[0023] In some embodiments of the present application, in S1, the barium titanate is dispersed in the buffer, specifically, the barium titanate is added to the buffer and ultrasonic treatment is performed for 20-40 minutes.

[0024] In some embodiments of the present application, in S1, the reaction time is 12-30 hours.

[0025] In some embodiments of the present application, in S2, the organic solvent is one or a combination of chloroform, dichloromethane, N-methyl pyrrolidone and dimethylformamide, and the solvent mainly affects the solubility and solution viscosity, and the combination of dichloromethane and dimethylformamide is preferred.

[0026] In some embodiments of the present application, in S2, the polydopamine-modified barium titanate particles are dispersed in the organic solvent, specifically, the polydopamine-modified barium titanate particles are added to the organic solvent and ultrasonic treatment is performed for 40-80 minutes.

[0027] In some embodiments of the present application, in S2, the stirring time is 12-30 hours.

[0028] In some embodiments of the present application, in S2, the parameters of the electrospinning are as follows: flow rate 0.001-0.004 mm / s, voltage 12-24 V, receiving distance 12-20 cm, and drum rotation speed 400-800 r / min.

[0029] The flexible piezoelectric sensing composite film obtained by the present application comprises a polylactic acid matrix and polydopamine-modified barium titanate dispersed in the polylactic acid matrix.

[0030] Example 1 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 3 parts of barium titanate in a sodium phosphate-sodium chloride buffer solution, ultrasonicating for 30 minutes, adding 2 parts of dopamine and reacting for 12 hours, performing solid-liquid separation by using a high-speed centrifuge under the condition of 8000 r / min, washing 5 times with anhydrous ethanol, drying the obtained product in an oven at 80 DEG C for 12 h, and obtaining polydopamine modified barium titanate particles; (2) dispersing the polydopamine modified barium titanate particles in chloroform, ultrasonicating for 60 minutes, adding 95 parts of polylactic acid, and stirring for 12 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning device, setting the spinning parameters, the flow rate being 0.001 mm / s, the voltage being 12 V, the receiving distance being 12 cm, and the drum rotating speed being 400 r / min, and electrospinning to obtain a composite film; and (4) using the composite film with a size of 2.5 cm*2.5 cm as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0031] Example 2 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 10 parts of barium titanate in a sodium carbonate-sodium bicarbonate buffer solution, ultrasonicating for 30 minutes, adding 5 parts of dopamine and reacting for 30 hours, performing solid-liquid separation by using a high-speed centrifuge under the condition of 8000 r / min, washing 5 times with anhydrous ethanol, drying the obtained product in an oven at 80 DEG C for 12 h, and obtaining polydopamine modified barium titanate particles; (2) dispersing the polydopamine modified barium titanate particles in N-methyl pyrrolidone, ultrasonicating for 60 minutes, adding 85 parts of polylactic acid, and stirring for 30 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning device, setting the spinning parameters, the flow rate being 0.004 mm / s, the voltage being 24 V, the receiving distance being 20 cm, and the drum rotating speed being 800 r / min, and electrospinning to obtain a composite film; and (4) using the composite film with a size of 2.5 cm*2.5 cm as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0032] Example 3 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 12 parts of barium titanate in a tris-hydroxymethyl aminomethane hydrochloride buffer by mass fraction, ultrasonicating for 30 minutes, adding 10 parts of dopamine and reacting for 30 hours, performing solid-liquid separation by using a high-speed centrifuge under the condition of 8000 r / min, washing 5 times by using anhydrous ethanol, drying the obtained product in an oven at 80 DEG C for 12 h, and obtaining polydopamine modified barium titanate particles; (2) dispersing the polydopamine modified barium titanate particles in dimethylformamide, ultrasonicating for 60 minutes, adding 78 parts of polylactic acid, and stirring for 30 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning equipment, setting spinning parameters, the flow rate being 0.002 mm / s, the voltage being 18 V, the receiving distance being 15 cm, and the drum rotating speed being 500 r / min, and electrospinning to obtain a composite film; and (4) using a 2.5 cm*2.5 cm composite film as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0033] Example 4 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 10 parts of barium titanate in a tris-hydroxymethyl aminomethane hydrochloride buffer by mass fraction, ultrasonicating for 30 minutes, adding 10 parts of dopamine and reacting for 24 hours, performing solid-liquid separation by using a high-speed centrifuge under the condition of 8000 r / min, washing 5 times by using anhydrous ethanol, drying the obtained product in an oven at 80 DEG C for 12 h, and obtaining polydopamine modified barium titanate particles; (2) dispersing the polydopamine modified barium titanate particles in dichloromethane, ultrasonicating for 60 minutes, adding 80 parts of polylactic acid, and stirring for 24 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning equipment, setting spinning parameters, the flow rate being 0.003 mm / s, the voltage being 24 V, the receiving distance being 18 cm, and the drum rotating speed being 600 r / min, and electrospinning to obtain a composite film; and (4) using a 2.5 cm*2.5 cm composite film as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0034] Example 5 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) in a sodium carbonate-sodium bicarbonate buffer, 15 parts of barium titanate is added and ultrasonic is performed for 30 minutes, 10 parts of dopamine is added and reacted for 18 hours, solid-liquid separation is performed by a high-speed centrifuge at 8000 r / min, the obtained product is washed with anhydrous ethanol for 5 times, and the obtained product is dried in an oven at 80 DEG C for 12 h to obtain polydopamine modified barium titanate particles; (2) the polydopamine modified barium titanate particles are dispersed in a dimethylformamide / chloroform mixed solvent (mass ratio of dimethylformamide to chloroform is 80:20), ultrasonic is performed for 60 minutes, 75 parts of polylactic acid is added and stirred for 18 hours to obtain a spinning solution; (3) the spinning solution is added into an electrospinning equipment, spinning parameters are set, the flow rate is 0.003 mm / s, the voltage is 12 V, the receiving distance is 15 cm, and the drum rotating speed is 400 r / min, and the composite film is obtained by electrospinning; (4) the conductive copper foil is attached to both sides of the composite film as the top electrode and the bottom electrode to prepare a piezoelectric device.

[0035] Example 6 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) in a sodium carbonate-sodium bicarbonate buffer, 15 parts of barium titanate is added and ultrasonic is performed for 30 minutes, 10 parts of dopamine is added and reacted for 18 hours, solid-liquid separation is performed by a high-speed centrifuge at 8000 r / min, the obtained product is washed with anhydrous ethanol for 5 times, and the obtained product is dried in an oven at 80 DEG C for 12 h to obtain polydopamine modified barium titanate particles; (2) the polydopamine modified barium titanate particles are dispersed in a dimethylformamide / chloroform mixed solvent (mass ratio of dimethylformamide to chloroform is 80:20), ultrasonic is performed for 60 minutes, 75 parts of polylactic acid is added and stirred for 18 hours to obtain a spinning solution; (3) the spinning solution is added into an electrospinning equipment, spinning parameters are set, the flow rate is 0.003 mm / s, the voltage is 12 V, the receiving distance is 15 cm, and the drum rotating speed is 400 r / min, and the composite film is obtained by electrospinning; (4) the conductive copper foil is attached to both sides of the composite film as the top electrode and the bottom electrode to prepare a piezoelectric device.

[0036] Example 7 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 4 parts of barium titanate in a sodium phosphate-sodium chloride buffer solution, ultrasonicating for 30 minutes, adding 8 parts of dopamine and reacting for 24 hours, performing solid-liquid separation by using a high-speed centrifuge at 8000 r / min, washing 5 times with anhydrous ethanol, drying the obtained product in an oven at 80 DEG C for 12 hours, and obtaining polydopamine modified barium titanate particles; (2) dispersing the polydopamine modified barium titanate particles in dichloromethane / N-methyl pyrrolidone mixed solvent (mass ratio of dichloromethane and N-methyl pyrrolidone is 80:20), ultrasonicating for 60 minutes, adding 88 parts of polylactic acid, and stirring for 24 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning device, setting the spinning parameters, the flow rate is 0.003 mm / s, the voltage is 24 V, the receiving distance is 20 cm, and the drum rotating speed is 800 r / min, and electrospinning to obtain a composite film; and (4) using the composite film with a size of 2.5 cm*2.5 cm as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0037] Comparative Example 1 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) adding 5 parts of barium titanate in a sodium phosphate-sodium chloride buffer solution, ultrasonicating for 30 minutes, performing solid-liquid separation by using a high-speed centrifuge at 8000 r / min, washing 5 times with anhydrous ethanol, and drying the obtained product in an oven at 80 DEG C for 12 hours to obtain barium titanate particles; (2) dispersing the barium titanate particles in chloroform, ultrasonicating for 60 minutes, adding 95 parts of polylactic acid, and stirring for 12 hours to obtain a spinning solution; (3) adding the spinning solution into an electrospinning device, setting the spinning parameters, the flow rate is 0.001 mm / s, the voltage is 12 V, the receiving distance is 12 cm, and the drum rotating speed is 400 r / min, and electrospinning to obtain a composite film; and (4) using the composite film with a size of 2.5 cm*2.5 cm as an intermediate layer, attaching conductive copper foils to both sides of the composite film as top and bottom electrodes to prepare a piezoelectric device.

[0038] Comparative Example 2 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) in a sodium carbonate-sodium bicarbonate buffer, 15 parts of barium titanate is added, and ultrasonic treatment is performed for 30 minutes, and solid-liquid separation is performed at 8000 r / min by using a high-speed centrifuge, and the obtained product is washed with anhydrous ethanol for 5 times, and the obtained product is dried in an oven at 80 DEG C for 12 hours to obtain barium titanate particles; (2) the barium titanate particles are dispersed in dichloromethane, and ultrasonic treatment is performed for 60 minutes, and 85 parts of polylactic acid is added, and stirring is performed for 30 hours to obtain a spinning solution; (3) the spinning solution is added to an electrospinning device, and spinning parameters are set, the flow rate is 0.004 mm / s, the voltage is 24 V, the receiving distance is 20 cm, and the drum rotating speed is 800 r / min, and the composite film is obtained by electrospinning; (4) the composite film with a size of 2.5 cm*2.5 cm is used as an intermediate layer, and conductive copper foil is attached to both sides of the composite film as a top electrode and a bottom electrode to prepare a piezoelectric device.

[0039] Comparative Example 3 A flexible piezoelectric sensing composite film is prepared by the following steps: (1) in chloroform, 100 parts of polylactic acid is added, and stirring is performed for 30 hours to obtain a spinning solution; (2) the spinning solution is added to an electrospinning device, and spinning parameters are set, the flow rate is 0.002 mm / s, the voltage is 18 V, the receiving distance is 15 cm, and the drum rotating speed is 500 r / min, and a pure polylactic acid film is obtained by electrospinning; (4) the pure polylactic acid film with a size of 2.5 cm*2.5 cm is used as an intermediate layer, and conductive copper foil is attached to both sides of the pure polylactic acid film as a top electrode and a bottom electrode to prepare a piezoelectric device.

[0040] The piezoelectric devices obtained in each example and comparative example are tested for piezoelectric performance and mechanical performance, and the test results are shown in Table 1.

[0041] Table 1 Piezoelectric performance and mechanical performance of polylactic acid / modified barium titanate composite film

[0042] As can be seen from Table 1, compared with Comparative Example 1, Comparative Example 2 and Comparative Example 3 respectively, the output current of Example 1, Example 2 and Example 3 is higher than that of the corresponding comparative example, and the piezoelectric stability is also higher, but the improvement is smaller than the output current. The tensile strength and elongation at break of each example are also higher than those of the corresponding comparative example. Compared among each example, the piezoelectric output current of Example 4 reaches the highest value, and the piezoelectric stability of Example 4 and Example 6 reaches the best. The tensile strength of Example 4 and Example 6 is also higher. The elongation at break of Example 7 is the best.

[0043] The motion monitoring performance of the piezoelectric devices obtained in each example and comparative example is tested, and the test results are shown in Table 2.

[0044] Table 2 Motion monitoring performance of poly-lactic acid / modified barium titanate composite film piezoelectric devices

[0045] As can be seen from Table 2, the piezoelectric output current of Examples 1, 2 and 3 under different motion states are higher than that of Comparative Examples 1, 2 and 3, respectively. In comparison among the examples, Example 4 achieves the highest piezoelectric output current value in the motion states of finger bending, walking and fast running, etc.

Claims

1. A method for preparing a flexible piezoelectric sensing composite film, characterized in that: include: S1, dispersing barium titanate in a buffer solution, then adding dopamine to react to obtain polydopamine-modified barium titanate particles; S2, dispersing polydopamine-modified barium titanate particles in an organic solvent, adding polylactic acid, and stirring to obtain a spinning solution; S3, electrospinning the spinning solution to obtain a flexible piezoelectric sensing composite membrane.

2. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: Calculated by weight, the amounts of barium titanate, dopamine and polylactic acid are 10-15 parts, 2-10 parts and 75-95 parts respectively.

3. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S1, the buffer solution is one of tris hydrochloride buffer solution, disodium hydrogen phosphate-sodium chloride buffer solution and sodium carbonate-sodium bicarbonate buffer solution.

4. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, wherein: In S1, barium titanate is dispersed in a buffer solution, specifically, barium titanate is added to the buffer solution and ultrasonicated for 20 to 40 minutes.

5. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S1, the reaction time is 12 to 30 hours.

6. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S2, the organic solvent is one or a combination of chloroform, dichloromethane, N-methylpyrrolidone and dimethylformamide.

7. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S2, the polydopamine-modified barium titanate particles are dispersed in an organic solvent. Specifically, the polydopamine-modified barium titanate particles are added to the organic solvent and ultrasonicated for 40 to 80 minutes.

8. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S2, the stirring time is 12 to 30 hours.

9. The method for preparing the flexible piezoelectric sensing composite film according to claim 1, characterized in that: In S2, the electrospinning parameters are: flow rate 0.001-0.004 mm / s, voltage 12-24 V, receiving distance 12-20 cm, and drum speed 400-800 rpm.

10. The flexible piezoelectric sensing composite film obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The invention comprises a polylactic acid matrix and polydopamine-modified barium titanate dispersed in the polylactic acid matrix.

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