A MOF-based hybrid thin film for humidity sensing and actuation and its preparation method

Abstract

The present invention provides a MOFs-based mixed matrix film for humidity sensing and driving and a preparation method thereof, belonging to the technical field of humidity sensors. The preparation method of the present invention comprises the following steps: step 1, fully dispersing MOFs crystal powder in ethanol to obtain solution A; step 2, mixing binder B and solution A evenly and then rotary evaporating to obtain concentrated solution C; step 3, coating the concentrated solution C in step 2 on a substrate and heating until the solvent is completely evaporated to obtain a film D; step 4, peeling the film D in step 3 from the substrate, washing and drying to obtain a MOFs-based mixed matrix film. The present invention provides a self-folding response deformation single-layer film curvature type humidity actuator, which solves the problem of weakened interlayer adhesion of double-layer film curvature type actuators during long-term use, and also solves the problems of signal processing and power supply use of the actuator, and has broad application prospects in environmental monitoring, aerospace, soft robots and other fields.

Description

Technical Field

[0001] The invention relates to the technical field of humidity sensors, in particular to a MOFs-based mixed film for humidity sensing and driving and a preparation method thereof. Background Art

[0002] Humidity is one of the most important physical quantities in human daily life. Its monitoring and control as well as the driver that converts humidity into mechanical energy play an important role in industrial and agricultural production, food and drug storage, climate monitoring and precision instrument maintenance. At the same time, with the rapid development of the Internet of Things and information technology, people's demand and attention to flexible electronic products are increasing. Traditional humidity sensors detect humidity signals by converting them into electrical signals such as capacitance or impedance, so special integrated modules are required to process the converted signals. Traditional humidity drivers are generally implemented with double-layer films. Such humidity sensors and humidity drivers have the following disadvantages: large equipment size and need for signal processing modules, short service life, easy to be contaminated, limited use distance, interface failure, etc., which greatly limit their further development and application in some special applications. Based on the above reasons, seeking a humidity sensor and humidity driver device that does not require a special signal processing module, does not require an external power module, and has no risk of interface failure, and is expected to be used in the fields of wearables, electronic devices, etc., has become one of the problems that the industry needs to solve urgently.

[0003] Metal-Organic Frameworks (MOFs) are a type of porous crystalline materials with a periodic network structure formed by self-assembly of metal centers (metal ions or metal clusters) and organic bridging ligands. MOFs have excellent properties such as diverse structures, uniform pore sizes, extremely high porosity and specific surface area, and extremely high thermal stability and chemical stability. Therefore, they are widely used in the construction of various types of sensor devices such as chemical sensors, biosensors and gas sensors. Among them, the Lavoisier (Materials of Institute Lavoisierframeworks, MIL) series of MOFs materials will show a unique "breathing" effect after absorbing water molecules or solvent molecules, that is, swelling response occurs after adsorbing guest molecules, resulting in an increase in the unit cell volume. Therefore, after its powder particles are doped into a polymer to prepare a mixed matrix film, a unique and designable self-folding response deformation can be achieved, which is expected to obtain flexible humidity sensors and humidity actuators. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a preparation method of a MOFs-based hybrid matrix film for humidity sensing and humidity driving, which has no risk of interface failure, does not require a signal processing module and a power supply module, has a simple preparation process, is inexpensive, does not rely on an external voltage, and has the characteristics of high sensitivity and fast response speed.

[0005] The present invention is realized through the following technical solutions:

[0006] A preparation method of a MOFs-based hybrid film for humidity sensing and humidity driving, comprising the following steps:

[0007] Step 1, fully disperse MOFs crystal powder in ethanol to obtain solution A;

[0008] Step 2, mix binder B and solution A evenly and then perform rotary evaporation to obtain concentrated solution C;

[0009] Step 3, coat the concentrated solution C in Step 2 on a substrate and heat it until the solvent is completely evaporated to obtain film D;

[0010] Step 4, peel the film D in Step 3 from the substrate, wash and dry it to obtain the MOFs-based hybrid matrix film.

[0011] Preferably, in Step 1, the MOFs crystal powder is a MIL (MIL: Materials from Institute Lavoisier)-type metal-organic framework material with a breathing effect such as MIL-53, MIL-88 or MIL-101, and its addition amount is 0.01 - 0.07 g / ml calculated based on the volume of ethanol.

[0012] Preferably, in Step 1, the dispersion method of the MOFs crystal powder is specifically to place it in an ultrasonic cleaner at room temperature and ultrasonicate for 10 min.

[0013] Preferably, binder B in Step 2 is to stir thermoplastic polyurethane elastomer (abbreviated as TPU) at 50 °C for 20 - 30 min to fully dissolve it in DMF, and its addition amount is 0.02 - 0.06 g / ml calculated based on the volume of DMF.

[0014] Preferably, the mixing method of binder B and solution A in Step 2 is to slowly drop binder B into solution A and ultrasonicate it in an ultrasonic cleaner at room temperature for 10 min.

[0015] Preferably, the volume ratio of the solvent of solution A and binder B in Step 2 is 1:1.

[0016] Preferably, in step 2, the rotary evaporation is specifically as follows: the water bath temperature is 25-50 °C, the rotary evaporation time is 20-40 min, and the rotation speed of the rotary evaporator is 70-100 rpm.

[0017] Preferably, the loading amount range of MOFs in the mixed matrix film prepared in step 4 is 30%-90%.

[0018] Preferably, the MOF-based mixed matrix film is applied to humidity sensors or humidity-driven devices.

[0019] Compared with the prior art, the beneficial effects of the preparation method of the MOF-based mixed thin film provided by the present invention, which can be used in humidity sensors and humidity-driven devices, are as follows:

[0020] Through the "breathing effect" of MIL series MOF materials, unique self-folding response deformation is achieved, and effective specific detection of humidity in the environment is carried out. It has many advantages such as high sensitivity, fast response speed, good flexibility and strength, and convenient carrying, and has broad application prospects in the fields of environmental monitoring, aerospace, soft robotics, etc.

[0021] The present invention provides a single-layer film curvature type humidity sensor and humidity driver, which solves the problem of weakened interlayer adhesion that occurs during the long-term use of the double-layer film curvature type sensor, and also solves the problems of the use of the signal processing module and the power supply module in the application of the driver. Description of the Drawings

[0022] Figure 1 It is the SEM characterization diagram of the MOF-based mixed matrix film that can be used for humidity sensing and driving in Example 1 of the present invention.

[0023] Figure 2 It is the physical diagram of the MOF-based mixed matrix film that can be used for humidity sensing and driving in Example 1 of the present invention before and after humidity response.

[0024] Figure 3 It is the response data diagram of the MOF-based mixed matrix film that can be used for humidity sensing and driving in Example 1 of the present invention under different humidity conditions.

[0025] Figure 4 It is the humidity cycle response data diagram of the MOF-based mixed matrix film that can be used for humidity sensing in Example 1 of the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be further described in detail with reference to the drawings in the embodiments of the present invention. The described embodiments are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] Step 1: Select a high-purity optical quartz glass sheet with a size of 2.5 cm × 2.5 cm as the substrate. After thoroughly rinsing it with deionized water, soak it in ethanol and ultrasonicate for 10 min, then dry it in a blast drying oven for later use.

[0029] Step 2: Add 0.2 g of TPU particles to 5 ml of DMF solution, and stir at 50 °C for 30 min to fully dissolve it to obtain Solution A;

[0030] Step 3: Weigh 0.3 g of MIL-88A crystal powder and place it in a scintillation vial, then add 5 ml of ethanol solution. Place it in an ultrasonic cleaner at room temperature and ultrasonicate for 10 min to fully disperse the MOFs crystal powder in the ethanol solvent to obtain Solution B;

[0031] Step 4: Slowly drip Solution A into Solution B and continue ultrasonication for 10 min to evenly mix the two components to obtain a mixed solution C. Transfer it to a round-bottom flask and rotary evaporate at 35 °C for 20 min to obtain a concentrated solution D, with a rotation speed of 90 rpm;

[0032] Step 5: Evenly coat 1 ml of concentrated solution D on the substrate, cover it with a petri dish and place it in a blast drying oven, dry it at 80 °C for 2 h to completely volatilize the solvent; then soak the substrate in ethanol solution for two minutes, use tweezers to peel the film from the substrate, wash it successively with deionized water and ethanol, and then dry it in a blast drying oven for 30 min to obtain the MOFs-based mixed matrix film, which is labeled as 1#.

[0033] Example 2

[0034] Step 1: Select a high-purity optical quartz glass sheet with a size of 2.5 cm × 2.5 cm as the substrate. After thoroughly rinsing it with deionized water, soak it in ethanol and ultrasonicate for 10 min, then dry it in a blast drying oven for later use.

[0035] Step 2: Add 0.3 g of TPU particles to 5 ml of DMF solution, and stir at 50 °C for 30 min to fully dissolve it to obtain Solution A;

[0036] Step 3: Weigh 0.2 g of MIL-88A crystal powder and place it in a scintillation vial, then add 5 ml of ethanol solution. Place it in an ultrasonic cleaner at room temperature and ultrasonicate for 10 min to fully disperse the MOFs crystal powder in the ethanol solvent to obtain Solution B;

[0037] Step 4: Slowly add Solution A dropwise into Solution B and continue ultrasonic treatment for 10 min to make the two components mix evenly, obtaining mixed solution C. Transfer it to a round-bottom flask and rotary evaporate at 35 °C for 20 min to obtain concentrated solution D, with a rotation speed of 90 rpm.

[0038] Step 5: Uniformly coat 1 ml of concentrated solution D on the substrate, cover it with a petri dish and place it in a forced-air drying oven, dry it at 80 °C for 2 h to completely volatilize the solvent; then immerse the substrate in an ethanol solution for two minutes, use forceps to peel the film from the substrate, wash it successively with deionized water and ethanol, and then dry it in a forced-air drying oven for 30 min to obtain the MOFs-based mixed matrix film, which is labeled as 2#.

[0039] Example 3

[0040] Step 1: Select a 2.5 cm × 2.5 cm high-purity optical quartz glass sheet as the substrate, thoroughly rinse it with deionized water, soak it in ethanol and perform ultrasonic treatment for 10 min, and then dry it in a forced-air drying oven for standby.

[0041] Step 2: Add 0.2 g of TPU particles into 5 ml of DMF solution, stir at 50 °C for 30 min to fully dissolve it to obtain Solution A.

[0042] Step 3: Weigh 0.3 g of MIL-100 crystal powder, place it in a scintillation vial, add 5 ml of ethanol solution, and place it in an ultrasonic cleaner at room temperature for ultrasonic treatment for 10 min to fully disperse the MOFs crystal powder in the ethanol solvent to obtain Solution B.

[0043] Step 4: Slowly add Solution A dropwise into Solution B and continue ultrasonic treatment for 10 min to make the two components mix evenly, obtaining mixed solution C. Transfer it to a round-bottom flask and rotary evaporate at 35 °C for 20 min to obtain concentrated solution D, with a rotation speed of 90 rpm.

[0044] Step 5: Uniformly coat 1 ml of concentrated solution D on the substrate, cover it with a petri dish and place it in a forced-air drying oven, dry it at 80 °C for 2 h to completely volatilize the solvent; then immerse the substrate in an ethanol solution for two minutes, use forceps to peel the film from the substrate, wash it successively with deionized water and ethanol, and then dry it in a forced-air drying oven for 30 min to obtain the MOFs-based mixed matrix film, which is labeled as 3#.

[0045] The MOFs-based mixed matrix films prepared in Examples 1 to 3 were subjected to morphology characterization. Figure 1 Corresponding to the surface SEM characterization diagram of the 1# film prepared in Example 1, it can be seen from the figure that the distribution of MOFs grains in the film is relatively uniform and the combination with the polymer is good.

[0046] The test results of the surface SEM characterization diagrams of the 2# and 3# membranes prepared in Example 2 and Example 3 are similar to Figure 1 that.

[0047] The MOF-based mixed matrix membranes prepared in Examples 1 to 3 all showed good flexibility. For example, Figure 2 the physical pictures of the MOF-based mixed matrix membrane 1# prepared in Example 1 before and after humidity response when directly placed in the air are shown as follows.

[0048] The MOF-based mixed matrix membrane 1# prepared in Example 1 was placed in a saturated salt solution atmosphere with different humidities, and the change in the deflection angle of the MOF-based mixed matrix membrane under different relative humidity conditions was measured. According to the formula:

[0049]

[0050] the curvature of the MOF-based mixed matrix membrane 1# after humidity response was calculated under the humidity conditions corresponding to different saturated salt solutions, and the humidity response curve shown as follows was obtained. The curvature of the MOF-based mixed matrix membrane increases with the increase of relative humidity, and the two show a good linear relationship. Therefore, as a new type of humidity sensor and humidity actuator, the MOF-based mixed matrix membrane has excellent humidity response performance. Figure 3 The figure reflects the curvature change of the MOF-based mixed matrix membrane 1# prepared in Example 1 after 20 humidity cycle responses under the condition of 75% RH relative humidity, indicating that the humidity response performance of the MOF-based mixed matrix membrane obtained in the present invention is stable and can be recycled.

[0051] Figure 4 ​

Claims

1. A MOF-based hybrid thin film for humidity sensing and actuation, Characterized in that: The hybrid thin film is prepared according to the following method: 1) Thoroughly disperse MOF crystal powder in ethanol to obtain solution A; 2) Mix binder B and solution A evenly and then perform rotary evaporation to obtain concentrated solution C; 3) Coat the concentrated solution C in step 2 on a substrate and heat it until the solvent completely evaporates to obtain thin film D; 4) Peel the thin film D in step 3 from the substrate, wash and dry it to obtain MOF-based hybrid thin films with different contents. The MOF crystal powder in step 1 is a MIL-type metal-organic framework material with a breathing effect, and the binder B in step 2 is thermoplastic polyurethane elastomer (abbreviated as TPU).

2. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 1, Characterized in that: The MOF crystal powder in step 1 is MIL-53, MIL-88 or MIL-101, and its addition amount is 0.01 - 0.07 g / ml calculated by the volume of ethanol.

3. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 1, Characterized in that: The binder B in step 2 is to stir the thermoplastic polyurethane elastomer at 50 °C for 20 - 30 min to fully dissolve it in DMF, and its addition amount is 0.02 - 0.06 g / ml calculated by the volume of DMF.

4. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 1, Characterized in that: The mixing method of binder B and solution A in step 2 is to slowly drop binder B into solution A and place it in an ultrasonic cleaner at room temperature for ultrasonic treatment for 10 min.

5. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 3, Characterized in that: The volume ratio of the solvent of solution A and binder B in step 2 is 1:

1.

6. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 1, Characterized in that: The specific rotary evaporation in step 2 is as follows: the water bath temperature is 25 - 50 °C, the rotary evaporation time is 20 - 40 min, and the rotation speed of the rotary evaporator is 70 - 100 rpm.

7. A MOF-based hybrid thin film for humidity sensing and actuation according to claim 1, Characterized in that: The loading amount range of MOFs in the hybrid thin film prepared in step 4 is 30% - 90%.

8. Application of the MOF-based hybrid thin film according to any one of claims 1 - 7 in humidity sensing or humidity actuation.

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