Preparation method of dielectric layer film with high dielectric constant and high breakdown strength for electrowetting

Abstract

The invention discloses a preparation method of a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, which comprises the following steps: treating BaTiO3 nanoparticles with hydrogen peroxide to obtain surface hydroxylated barium titanate nanoparticles; preparing a silane coupling agent solution, and adding the surface hydroxylated barium titanate nanoparticles into the solution for treatment to obtain silane coupling agent modified barium titanate nanoparticles; preparing a polymethyl methacrylate / vinylidene fluoride-trifluoroethylene-trifluorochlor oethylene mixed solution, and then adding the silane coupling agent modified barium titanate nanoparticles into the mixed solution to obtain a mixture; coating ITO glass with the mixture in a spinning mode through a table type spin coater, and then curing the ITO glass to obtain the dielectric layer thin film. The dielectric layer film prepared by the invention not only can improve the modulation range of an electrowetting contact angle, but also has higher dielectric constant and breakdown strength, and can obviously reduce the liquid drop driving voltage, improve the reliability of equipment and prolong the service life of the dielectric layer.

Description

Technical Field

[0001] The invention belongs to the technical field of electrowetting on dielectrics, and in particular relates to a method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting. Background Art

[0002] Due to its easy operation and excellent integration, the electrowetting on dielectric (EWOD) technology has been applied in many fields, including electrowetting displays, microfluidics, variable focus lenses, biomedicine and other applications. A typical EWOD device consists of a conductive liquid droplet, a solid substrate with a metal electrode, and a hydrophobic dielectric layer film. After applying an electric potential between the substrate electrode and the conductive liquid, the contact angle of the droplet on the dielectric layer decreases as the voltage increases, thereby changing the wettability of the droplet. In the electrowetting technology, the dielectric layer's ability to resist breakdown and the problem of controlling the droplet drive voltage cannot be ignored. Under the action of repeated electric fields, the electrowetting dielectric layer is prone to dielectric breakdown, causing the droplet to be electrolyzed and penetrate into the device, causing damage to the device. Having a high breakdown strength can improve the reliability and life of the device. In addition, it is also very important to use a lower drive voltage to achieve a wide range of changes in the droplet contact angle. Dielectric films with high dielectric constants can reduce the driving voltage of electrowetting, prevent catastrophic failure of EWOD devices when excessive voltage is applied, improve the further integration of EWOD, and increase the safety of EWOD in portable devices. Therefore, dielectric layer materials with both high dielectric constant and high breakdown strength are the key to EWOD.

[0003] At present, various polymers such as Teflon AF, CytopTM and Parylene-C have been applied to electrowetting dielectric layers. However, although these materials have good hydrophobicity, they have a low dielectric constant, usually around 2, and require a high driving voltage during the electrowetting process, which increases the risk of breakdown. Therefore, it is particularly important to study dielectric layer materials with higher performance for EWOD. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these objects and other advantages of the present invention, a method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting is provided, comprising the following steps:

[0006] Step 1: BaTiO 3 The nanoparticles are treated with hydrogen peroxide to obtain surface hydroxylated barium titanate nanoparticles;

[0007] Step 2: preparing a silane coupling agent solution, and then adding the surface hydroxylated barium titanate nanoparticles into the solution for treatment to obtain silane coupling agent modified barium titanate nanoparticles;

[0008] Step 3, preparing a mixed solution of polymethyl methacrylate (PMMA) / vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), and then adding barium titanate nanoparticles modified by a silane coupling agent into the mixed solution to obtain a mixture;

[0009] Step 4: Spin-coat the mixture on the ITO glass using a desktop coating machine, and then put it into a vacuum drying oven for curing to obtain a dielectric layer film.

[0010] Preferably, the step 1 is specifically: BaTiO 3 The nanoparticles were added to a hydrogen peroxide solution, ultrasonically treated and condensed and refluxed. After the reaction, the resulting mixed solution was centrifuged, vacuum dried and ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH.

[0011] Preferably, in step 2, the silane coupling agent is KH550, and step 2 specifically comprises: dissolving KH550 in a mixed solution of ethanol and deionized water, and then 3 -OH was added to the silane coupling agent solution, ultrasonicated and magnetically stirred, and the mixed solution was centrifuged and vacuum dried and ground to obtain silane coupling agent-modified barium titanate nanoparticles, namely BaTiO 3 -KH550.

[0012] Preferably, the step three is specifically as follows: adding polymethyl methacrylate (PMMA) and vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (P(VDF-TrFE-CTFE)) to an organic solvent in sequence, ultrasonicating and stirring; obtaining a PMMA / P(VDF-TrFE-CTFE) mixed solution; and then 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution and stirred vigorously, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture.

[0013] Preferably, in step 1, BaTiO 3 The mass ratio of the product to hydrogen peroxide is 1:8-10; the ultrasonic frequency is 20-40kHz, the ultrasonic treatment is performed for 30-45 minutes, and then the product is condensed and refluxed at 102-106°C for 3-6 hours, centrifuged for 5-10 minutes, and washed with deionized water; the vacuum drying temperature is 80-100°C, and the time is 8-12 hours.

[0014] Preferably, in step 2, BaTiO 3 The mass ratio of -OH to silane coupling agent solution is 1:0.4-0.6, and the mass ratio of KH550, ethanol and ionized water is 0.04-0.08:1:9.

[0015] Preferably, the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 30-45 min, the stirring temperature is 60-75° C., and the stirring time is 4-6 h; the vacuum drying temperature is 80-100° C., and the time is 8-12 h.

[0016] Preferably, in the step three, the mass ratio of PMMA, P(VDF-TrFE-CTFE) and organic solvent is 0.6:0.032:6-8; the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 1-2 h, and stirring is performed at 60-80° C. for 20-24 h; and the organic solvent is N,N-dimethylformamide (DMF) solvent.

[0017] Preferably, in step 3, BaTiO 3 - The addition amount of KH550 is 1-10wt% of the PMMA / P(VDF-TrFE-CTFE) mixed solution, and the vigorous stirring time is 48-56h.

[0018] Preferably, in step 4, the size of the ITO glass is 30 mm × 30 mm × 1 mm, the spin coating speed is 1000-1200 rpm, the time is 10-20 s, and then the speed is increased to 2000-2400 rpm, the time is 20-40 s; vacuum drying is performed at 80-100° C. for 8-12 hours until the solvent is completely evaporated.

[0019] Preferably, before step 3, the barium titanate nanoparticles modified with the silane coupling agent obtained in step 2 are subjected to blending modification by: mixing BaTiO 3 -KH550 was added to dilute hydrochloric acid and ultrasonically dispersed, and then nano cobalt oxide was added thereto. After stirring in an ice bath, the reaction was centrifuged and filtered, and then washed with deionized water to obtain BaTiO 3 -KH550, namely CoO / BaTiO 3 -KH550, and then in step 3, use the blended modified CoO / BaTiO 3 -KH550 is fine.

[0020] Preferably, when blending and modifying, BaTiO 3-The mass ratio of KH550 and nano-cobalt oxide is 1:0.05-0.10, the concentration of dilute hydrochloric acid is 0.5-1 mol / L, the amount of dilute hydrochloric acid is 5-10 mL, the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 5-10 min, the ice bath temperature is 0-5°C, the reaction is stirred for 4-8 hours, and the mixture is washed with deionized water for 3-6 times.

[0021] The present invention at least has the following beneficial effects: the present invention converts BaTiO modified by KH550 into 3 Nanoparticles are uniformly introduced into a PMMA / P(VDF-TrFE-CTFE) polymer matrix, and a dielectric layer film that can be used for EWOD is prepared by spin coating. Compared with the commonly used fluorinated dielectric layer materials, the prepared dielectric film also has a certain hydrophobicity, which can not only improve the modulation range of the electrowetting contact angle, but also has a higher dielectric constant and breakdown strength, which can significantly reduce the droplet driving voltage, improve the reliability of the device, and extend the service life of the dielectric layer; the present invention also introduces the nanoparticles into the PMMA / P(VDF-TrFE-CTFE) polymer matrix, and uses the spin coating to prepare the dielectric layer film that can be used for EWOD. Compared with the commonly used fluorinated dielectric layer materials, the prepared dielectric film also has a certain hydrophobicity, which can not only improve the modulation range of the electrowetting contact angle, but also has a higher dielectric constant and breakdown strength, which can significantly reduce the droplet driving voltage, improve the reliability of the device, and extend the service life of the dielectric layer 3 Nano-cobalt oxide is introduced into the nanoparticles to optimize the charge transfer and electrical stability of the prepared dielectric layer, thereby further improving its breakdown strength.

[0022] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an electron microscope image of the dielectric layer film prepared in Example 4;

[0024] Figure 2 BaTiO 3 -KH550 and unmodified BaTiO 3 XRD and infrared spectra of

[0025] Figure 3 The dielectric layer films prepared in Examples 1 to 4 and Comparative Example 1 were 2 ~10 6 Dielectric properties diagram in the frequency range of Hz;

[0026] Figure 4 Weibull distribution diagram of the breakdown strength of the dielectric layer films prepared in Examples 1 to 4 and Comparative Example 1;

[0027] Figure 5 This is a graph showing the change in contact angle with voltage in Example 4 at a DC voltage of 0 to 50 V. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0029] Example 1

[0030] A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, comprising the following steps:

[0031] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0032] Step 2: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, and then add 0.1 g BaTiO 3 -OH was added to the KH550 solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0033] Step 3: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.006 g BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0034] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coating machine. The spin coating speed is 1000 rpm for 10 seconds, and then the speed is increased to 2000 rpm for 20 seconds. Then, put it into a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 hours until the solvent is completely volatilized to obtain a dielectric layer film recorded as 1wt% BaTiO 3 -PVTC / PMMA.

[0035] Example 2

[0036] A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, comprising the following steps:

[0037] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0038] Step 2: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, and then add 0.1 g BaTiO 3 -OH was added to the KH550 solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0039] Step 3: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.02 g BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0040] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coating machine. The spin coating speed is 1000 rpm for 10 seconds, and then the speed is increased to 2000 rpm for 20 seconds. Then, put it into a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 hours until the solvent is completely volatilized to obtain a dielectric layer film recorded as 3wt% BaTiO 3 -PVTC / PMMA.

[0041] Example 3

[0042] A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, comprising the following steps:

[0043] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0044] Step 2: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, and then add 0.1 g BaTiO 3 -OH was added to the KH550 solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0045] Step 3: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.033 g BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0046] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coating machine. The spin coating speed is 1000 rpm for 10 seconds, and then the speed is increased to 2000 rpm for 20 seconds. Then, put it into a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 hours until the solvent is completely volatilized to obtain a dielectric layer film recorded as 5wt% BaTiO 3 -PVTC / PMMA.

[0047] Example 4

[0048] A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, comprising the following steps:

[0049] Step 1: 10gBaTiO 3The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0050] Step 2: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, and then add 0.1 g BaTiO 3 -OH was added to the KH550 solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0051] Step 3: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.07 g BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0052] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coating machine. The spin coating speed is 1000 rpm for 10 seconds, and then the speed is increased to 2000 rpm for 20 seconds. Then, put it into a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 hours until the solvent is completely volatilized to obtain a dielectric layer film recorded as 10wt% BaTiO 3 -PVTC / PMMA.

[0053] Figure 1 In this embodiment, the content is 10wt% BaTiO 3 The SEM image of the film cross section shows that the film thickness is uniform. 3 The BaTiO 3 The nanoparticles have good compatibility with P(VDF-TrFE-CTFE) and PMMA matrices, and there is a strong interaction.

[0054] Example 5

[0055] A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, comprising the following steps:

[0056] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0057] Step 2: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, and then add 0.1 g BaTiO 3 -OH was added to the KH550 solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0058] Before step 3, the barium titanate nanoparticles modified with silane coupling agent obtained in step 2 are mixed and modified by mixing 0.1 g BaTiO 3 -KH550 was added to 10 mL of 0.5 mol / L dilute hydrochloric acid and ultrasonically dispersed at 20 kHz for 10 min, and then 0.05 g of nano cobalt oxide was added thereto. The mixture was stirred in an ice bath at 2 °C for 6 h, centrifuged and filtered, and then washed with deionized water for 4 times to obtain BaTiO 3 -KH550, namely CoO / BaTiO 3 -KH550.

[0059] Step 3: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.07 g CoO / BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0060] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coating machine. The spin coating speed is 1000 rpm for 10 seconds, and then the speed is increased to 2000 rpm for 20 seconds. Then, put it into a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 hours until the solvent is completely volatilized to obtain a dielectric layer film recorded as 10wt% CoO / BaTiO 3 -PVTC / PMMA.

[0061] Comparative Example 1

[0062] A method for preparing a dielectric layer film comprises the following steps:

[0063] Step 1: 0.032 g PMMA and 0.6 g P (VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 ° C for 24 h to obtain a PMMA / P (VDF-TrFE-CTFE) mixed solution;

[0064] Step 2: The ITO conductive glass substrate was cleaned in an ultrasonic bath containing acetone and ethanol, and then 1 mL of PMMA / P (VDF-TrFE-CTFE) mixed solution was taken with a rubber dropper and spin-coated on the ITO glass by a desktop coating machine. The spin coating speed was 1000 rpm for 10 s, and then the speed was increased to 2000 rpm for 20 s. Then it was placed in a vacuum drying oven for curing and vacuum dried at 80 ° C for 12 h until the solvent was completely volatilized to obtain a dielectric layer film recorded as 0 wt% BaTiO 3 -PVTC / PMMA.

[0065] Comparative Example 2

[0066] A method for preparing a dielectric layer film comprises the following steps:

[0067] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0068] Step 2: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.07 g BaTiO 3 -OH was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0069] Step 3: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 2 and spin-coat it on the ITO glass using a desktop coater. The spin coating speed is 1000 rpm for 10 s, and then the speed is increased to 2000 rpm for 20 s. Then, place it in a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 h until the solvent is completely evaporated to obtain a dielectric layer film.

[0070] Comparative Example 3

[0071] A method for preparing a dielectric layer film comprises the following steps:

[0072] Step 1: Dissolve 0.04 g KH550 in a mixed solution of 1 g ethanol and 9 g deionized water to obtain a KH550 solution, then add 0.1 g BaTiO 3 KH550 was added to the solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain KH550-modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0073] Step 2: 0.032 g PMMA and 0.6 g P(VDF-TrFE-CTFE) were added to 6 g DMF solvent in sequence, ultrasonicated at 25 kHz for 1 h, and then stirred at 60 °C for 24 h to obtain a PMMA / P(VDF-TrFE-CTFE) mixed solution; then 0.07 g BaTiO 3 -KH550 was added to the PMMA / P(VDF-TrFE-CTFE) mixed solution, and the mixture was vigorously stirred for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0074] Step 3: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 2 and spin-coat it on the ITO glass using a desktop coater. The spin coating speed is 1000 rpm for 10 s, and then the speed is increased to 2000 rpm for 20 s. Then, place it in a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 h until the solvent is completely evaporated to obtain a dielectric layer film.

[0075] Comparative Example 4

[0076] A method for preparing a dielectric layer film comprises the following steps:

[0077] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0078] Step 2: Dissolve 0.04g KH550 in a mixed solution of 1g ethanol and 9g deionized water, then add 0.1g BaTiO 3 -OH was added to the silane coupling agent solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain silane coupling agent modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0079] Step 3: Add 0.032 g PMMA to 2 g DMF solvent, ultrasonicate at 25 kHz for 1 h, and then stir at 60 °C for 24 h; then add 0.0036 g BaTiO 3 -KH550 was added to the PMMA mixture and stirred vigorously for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0080] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coater. The spin coating speed is 1000 rpm for 10 s, and then the speed is increased to 2000 rpm for 20 s. Then, place it in a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 h until the solvent is completely evaporated to obtain a dielectric layer film.

[0081] Comparative Example 5

[0082] A method for preparing a dielectric layer film comprises the following steps:

[0083] Step 1: 10gBaTiO 3 The nanoparticles were added to 100 g of hydrogen peroxide solution, ultrasonically treated at 25 kHz for 30 min, and then condensed and refluxed at 106 ° C for 6 h. After the reaction, the resulting mixed solution was centrifuged, then vacuum dried at 80 ° C for 12 h, and finally ground to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO 3 -OH;

[0084] Step 2: Dissolve 0.04g KH550 in a mixed solution of 1g ethanol and 9g deionized water, then add 0.1g BaTiO 3 -OH was added to the silane coupling agent solution and ultrasonically treated at 20kHz for 30min, and then dispersed under magnetic stirring at 60℃ for 6h. The mixed solution was centrifuged and vacuum dried at 80℃ for 12h, and then ground to obtain silane coupling agent modified barium titanate nanoparticles, namely BaTiO 3 -KH550;

[0085] Step 3: Add 0.6 g P(VDF-TrFE-CTFE) to 6 g DMF solvent, ultrasonicate at 25 kHz for 1 h, and then stir at 60 °C for 24 h; then add 0.067 g BaTiO 3 -KH550 was added to the P(VDF-TrFE-CTFE) mixed solution, and the mixture was vigorously stirred for 48 h, and then placed in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture;

[0086] Step 4: Clean the ITO conductive glass substrate in an ultrasonic bath containing acetone and ethanol, then use a rubber-tipped dropper to take 1 mL of the mixture obtained in step 3 and spin-coat it on the ITO glass using a desktop coater. The spin coating speed is 1000 rpm for 10 s, and then the speed is increased to 2000 rpm for 20 s. Then, place it in a vacuum drying oven for curing, and vacuum dry it at 80°C for 12 h until the solvent is completely evaporated to obtain a dielectric layer film.

[0087] The dielectric layer films prepared in Examples 1-4 and Comparative Examples 1-5 were characterized and tested. The static contact angles of Examples 1-5 and Comparative Examples 1-5 were tested using a contact angle meter. Each material was repeated 3-5 times and then the average value was taken. The results are shown in Table 1. 3 When the content of the organic solvent is 10 wt %, the static contact angle reaches the maximum value (105.05°), and a higher initial contact angle can also increase the contact angle variation range.

[0088] Table 1

[0089]

[0090]

[0091] Take Example 4 by H 2 O 2 and KH550 modified BaTiO 3 Compared with unmodified BaTiO 3 XRD and infrared analysis were performed to obtain the surface modification of BaTiO 3 The XRD and IR comparison chart is as follows Figure 2 As shown, from Figure 2 (a) It can be seen that BaTiO 3 BaTiO appears at 2θ=22.01°, 31.34°, 38.72°, 44.94°, 50.62°, 55.9° 3 The characteristic peaks of the three nanoparticles correspond to the (100), (110), (111), (200), (210), and (211) interfaces, respectively, indicating that barium titanate belongs to the cubic perovskite structure. From the XRD spectrum, it can be seen that all characteristic peaks of the three nanoparticles have not shifted, which indicates that when BaTiO is modified with a coupling agent, 3 During the process, the modified BaTiO 3 No obvious phase change occurs, which also indicates that amorphous KH550 will not change the crystal structure of barium titanate ceramics; Figure 2 (b) It can be seen that at 583cm -1 The strong absorption peak near BaTiO 3 The vibration absorption peak of Ti-O bond in -1 The absorption band near is mainly due to BaTiO 3 Absorbed CO 2 This causes a certain amount of carbonate to be mixed into the sample, 3450cm -1 The absorption peak at corresponds to the stretching vibration of the hydroxyl group. Figure 2 It can be seen that BaTiO 3 The absorption peak intensity of -OH in the -OH sample is much higher than that of BaTiO 3 The sample shows that after H 2 O 2 Treated BaTiO 3 The surface hydroxyl density is enhanced to a certain extent, that is, BaTiO 3 The hydroxylation modification was successful. After modification with KH550, the -1 The Si-O characteristic absorption peak appears at the bottom of the graphite crystal. These results also show that KH550 is indeed grafted onto BaTiO 3 The surface of nanoparticles.

[0092] The precision impedance analyzer was used to 2 Hz-10 6 The dielectric constants of the dielectric films prepared in Examples 1-5 and Comparative Examples 1-5 were tested in a frequency range of 100 Hz; each sample of Examples 1-5 and Comparative Examples 1-5 was tested 10 times at different locations using a ferroelectric analyzer, and then the breakdown performance of the dielectric films was evaluated using the Weibull distribution of the breakdown field strength. The dielectric constants and breakdown voltages of Examples 1-5 and Comparative Examples 1-5 are shown in Table 2.

[0093] Table 2

[0094]

[0095]

[0096] The dielectric films prepared in Examples 1-4 and Comparative Example 1 were 2 -10 6 The dielectric properties in the frequency range of Hz are shown in the figure Figure 3 As shown, it can be seen that with the high dielectric constant BaTiO 3 As the particle mass fraction increases, the dielectric constant of the dielectric layer film gradually increases. This is attributed to the BaTiO modified by KH550. 3 It can be well dispersed in the polymer matrix, further improving the interfacial polarization. 2 Hz, when BaTiO 3 When the content is 10 wt % (corresponding to Example 4), the dielectric constant reaches 24.6, which is a relatively high value in electrowetting applications.

[0097] The breakdown strength is also an important characteristic of the composite film, which determines the maximum applied potential and the number of voltage cycles during the electrowetting process. In order to show the stability of the breakdown performance of the composite film, the Weibull distribution diagram of the breakdown strength of the dielectric layer film prepared in Examples 1-4 and Comparative Example 1 is shown in FIG. Figure 4 As shown, with the BaTiO 3 As the mass fraction increases, the breakdown strength decreases. 3 When the content of BaTiO in Example 4 is 10wt%, the breakdown strength also reaches 194.90KV / mm, maintaining a relatively high value. 3 -P(VDF-TrFE-CTFE) / PMMA film has good breakdown strength and dielectric constant, which can increase the service life of the dielectric layer and reduce the driving voltage.

[0098] For Example 4, BaTiO modified by hydrogen peroxide and silane coupling agent 3It can be evenly dispersed in the polymer matrix, and the evenly dispersed nanoparticles can effectively improve the dielectric constant and breakdown strength of the dielectric film. Therefore, the values of the dielectric constant and breakdown strength of the dielectric film prepared in Example 4 are much higher than those in Comparative Example 2.

[0099] Based on Example 4, in Example 5, nano cobalt oxide was introduced for blending modification to BaTiO 3 -KH550. Due to the introduction of cobalt oxide, the charge transport and electrical stability of the finally prepared dielectric layer were optimized, thereby further improving the breakdown strength of the dielectric layer film.

[0100] It can be found that the dielectric constant and breakdown strength of the dielectric film prepared in Example 4 are both higher than those in Comparative Example 3, indicating that the BaTiO 2 O 2 nanoparticles modified by H 3 and KH550 together on the surface can effectively improve its dispersibility in the polymer matrix, thereby increasing the dielectric constant and breakdown strength.

[0101] By analyzing the dielectric constant and breakdown strength of the dielectric layer films prepared in Example 4 and Comparative Example 4, it can be found that adding PMMA can effectively improve the breakdown strength, but the dielectric constant decreases significantly.

[0102] By analyzing the dielectric constant and breakdown strength of the dielectric layer films prepared in Example 4 and Comparative Example 5, since PMMA was not added in Comparative Example 5, the dielectric constant of Comparative Example 5 is slightly higher than that of Example 4, but it is found that the breakdown strength decreases severely, which also indicates that PMMA can improve the breakdown strength of the dielectric film.

[0103] Taking the 10wt% BaTiO 3 dielectric layer film prepared in Example 4 as an example, the variation of the contact angle of the droplet on the dielectric layer with voltage was studied. The results are as Figure 5 shown. At voltages from 0 to 50V, the contact angle decreased from 105° to 69.7°, with a variation range of 35.3°. Therefore, this indicates that the dielectric layer film has a high contact angle modulation range and a low driving voltage.

[0104] Although the embodiments of the present invention have been disclosed as above, it is not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the examples shown and described herein.

Claims

1. A method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting, characterized in that: The following steps are involved: Step 1: treating BaTiO3 nanoparticles with hydrogen peroxide to obtain surface hydroxylated barium titanate nanoparticles; Step 2: preparing a silane coupling agent solution, and then adding the surface hydroxylated barium titanate nanoparticles into the solution for treatment to obtain silane coupling agent modified barium titanate nanoparticles; Step 3, preparing a mixed solution of polymethyl methacrylate / vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene, and then adding barium titanate nanoparticles modified by a silane coupling agent into the mixed solution to obtain a mixture; Step 4: Spin-coat the mixture on the ITO glass using a desktop coating machine, and then put it into a vacuum drying oven for curing to obtain a dielectric layer film.

2. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 1, characterized in that: The step 1 specifically comprises: adding BaTiO3 nanoparticles into a hydrogen peroxide solution, ultrasonically treating and condensing and refluxing, centrifuging the obtained mixed solution after the reaction, and then vacuum drying and grinding to obtain surface hydroxylated barium titanate nanoparticles, namely BaTiO3-OH.

3. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 1, characterized in that: In the step 2, the silane coupling agent is KH550, and the step 2 is specifically as follows: dissolving KH550 in a mixed solution of ethanol and deionized water, adding BaTiO3-OH to the silane coupling agent solution, ultrasonicating and magnetically stirring, centrifuging the mixed solution and vacuum drying and grinding to obtain silane coupling agent-modified barium titanate nanoparticles, namely BaTiO3-KH550.

4. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 1, characterized in that: The step three is specifically as follows: adding polymethyl methacrylate and vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene to an organic solvent in sequence, ultrasonicating and stirring; obtaining a polymethyl methacrylate / vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene mixed solution; then adding BaTiO3-KH550 to the polymethyl methacrylate / vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene mixed solution, stirring vigorously, and then placing it in a vacuum drying oven to evacuate and remove bubbles to obtain a mixture.

5. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 2, characterized in that: In the step 1, the mass ratio of BaTiO3 to hydrogen peroxide is 1:8-10; the ultrasonic frequency is 20-40kHz, the ultrasonic wave is performed for 30-45min, and then condensed and refluxed at 102-106°C for 3-6h, centrifuged for 5-10min, and washed with deionized water; the vacuum drying temperature is 80-100°C, and the time is 8-12h.

6. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 3, characterized in that: In the step 2, the mass ratio of BaTiO3-OH to silane coupling agent solution is 1:0.4-0.6, the mass ratio of KH550, ethanol and ionized water is 0.04-0.08:1:9, the ultrasonic frequency is 20-40kHz, the ultrasonic time is 30-45min, the stirring temperature is 60-75°C, the stirring time is 4-6h; the vacuum drying temperature is 80-100°C, and the time is 8-12h.

7. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 4, characterized in that: In the step 3, the mass ratio of polymethyl methacrylate, vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene and organic solvent is 0.6:0.032:6-8.

8. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 4, characterized in that: In the step 3, the ultrasonic frequency is 20-40 kHz, the ultrasonic time is 1-2 hours, and the stirring is performed at 60-80° C. for 20-24 hours; and the organic solvent is N,N-dimethylformamide solvent.

9. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 4, characterized in that: In the step 3, the addition amount of BaTiO3-KH550 is 1-10wt% of the polymethyl methacrylate / vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene mixed solution, and the vigorous stirring time is 48-56h.

10. The method for preparing a dielectric layer film with high dielectric constant and high breakdown strength for electrowetting according to claim 1, characterized in that: In the step 4, the size of the ITO glass is 30mm×30mm×1mm, the spin coating speed is 1000-1200rpm, the time is 10-20s, and then the speed is increased to 2000-2400rpm, the time is 20-40s; vacuum drying is carried out at 80-100°C for 8-12h until the solvent is completely evaporated.

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