CN114702709B - Flexible MXene protein composite membrane with electromagnetic shielding and pressure-sensitive characteristics, preparation method and application thereof - Google Patents

Flexible MXene protein composite membrane with electromagnetic shielding and pressure-sensitive characteristics, preparation method and application thereof Download PDF

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CN114702709B
CN114702709B CN202210372838.8A CN202210372838A CN114702709B CN 114702709 B CN114702709 B CN 114702709B CN 202210372838 A CN202210372838 A CN 202210372838A CN 114702709 B CN114702709 B CN 114702709B
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卢革宇
彭润昌
贾晓腾
杨梅
马雪南
赵力
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Jilin University
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Abstract

A flexible MXene protein composite membrane with electromagnetic shielding and pressure sensitivity characteristics, a preparation method and application thereof belong to the technical field of multifunctional material preparation. Degumming silkworm cocoon shells, adding hexafluoroisopropanol solution into silk nanofibers obtained after degumming to ensure that the silk nanofibers are well dispersed in a water phase, and obtaining silk nanofiber aqueous solution; and mixing the MXene nanosheet colloid solution with the silk nanofiber dispersion liquid, carrying out vacuum-assisted suction filtration on the mixture, and naturally drying the mixture to obtain the flexible MXene protein composite membrane. According to the invention, the flexible MXene protein composite membrane with different electromagnetic shielding effectiveness and mechanical properties can be obtained by changing the mass ratio of MXene to silk nanofiber. Due to the excellent conductivity of MXene and the structural characteristics of nanofibers, a conductive network is formed, and the nano-composite material can be used in the military field, artificial intelligence and daily protection, and has good application prospect.

Description

Flexible MXene protein composite membrane with electromagnetic shielding and pressure-sensitive characteristics, preparation method and application thereof
Technical Field
The invention belongs to the technical field of preparation of multifunctional materials, and particularly relates to a flexible MXene protein composite membrane with electromagnetic shielding and pressure-sensitive characteristics, a preparation method and application thereof. The composite film obtained by the invention has good electromagnetic interference (EMI) shielding performance and good mechanical performance, and has good potential and application feasibility for developing flexible wearable electronic equipment.
Background
With the rapid development of 5G and 6G communication technologies, electromagnetic waves have penetrated life aspects as carriers for information transmission. However, with the development of new generation communication technology and the increasing number of intelligent integrated mobile electronic devices, serious electromagnetic interference (EMI) problems are generated, for example: data loss and even information leakage, system faults caused by close-range strong electromagnetic induction effect and adverse effects on human health are caused. Therefore, the research of the electromagnetic shielding composite material is very important, which is not only beneficial to the protection of information, but also can help core sensitive electronic equipment and special personnel to avoid the interference of electromagnetic signals.
Electromagnetic shielding is the use of conductors or magnetic materials to attenuate or suppress magnetic and electric fields, and generally, highly effective EMI shielding materials have good electrical conductivity. With the continuous development of society, the traditional metal-based shielding material limits the application range due to the defects of high density, poor flexibility, easy corrosion, difficult processing and the like; the inert surfaces of carbon-based materials (such as graphene and carbon nanotubes) cause processing and design difficulties, and graphene films prepared by using a redox method have more surface defects, lower conductivity and are difficult to meet actual electromagnetic performance requirements. The development of electromagnetic shielding materials that are easy to process, lightweight, and have high Shielding Effectiveness (SE) is an urgent need.
Meanwhile, with the development of the internet of things technology, various types of flexible wearable sensing electronic devices such as pressure/strain sensors, temperature and humidity sensors and the like are attracting attention of researchers due to the excellent real-time monitoring capability and flexible interaction with human bodies. Particularly, the wearable pressure sensor can monitor physiological signals of a human body and detect movement of organisms in real time, and is important for maintaining personal safety and health conditions. The typical sensing material in conventional devices is replaced by electromagnetically shielded skin with sensing capabilities that can protect equipment and human or robotic systems from damaging electromagnetic waves while providing sensing capabilities. While previous reports on wearable electronics have demonstrated this, the fabrication of electronic skins that achieve both EMI shielding characteristics and their own high sensitivity remains a significant challenge due to limited choices of sensing materials and manufacturing strategies.
MXene is a two-dimensional nano material, can absorb electromagnetic waves more strongly, and is an electromagnetic shielding material with great development prospect. MXene has good conductivity, lower density and large specific surface area, is easy to be compounded with polymer, and is a good choice for preparing the multifunctional electromagnetic shielding material. For the first time, 2016 have published about two-dimensional Ti 3 C 2 T x Since the report of the electromagnetic shielding performance, several hundreds of research papers have been made about the electromagnetic shielding performance of MXene. Through compounding with the polymer, the MXene material can obtain excellent mechanical properties such as better flexibility, stronger tensile property and the like, thereby meeting the requirements of practical application. Silk fibroin is an amino acid-rich hydrophobic protein that self-assembles to form a tough and elastic material and thus can exhibit excellent mechanical properties. And by using a sensitization strategy, the silk fibroin is used as an intercalation agent, the interlayer spacing of the MXene nano-sheet is regulated, and the mechanical strength and the sensitivity to pressure sensing of the MXene nano-sheet are enhanced. Silk fibroin is a composite organic component, has good flexibility, biocompatibility, innocuity and other properties, is easy to process and degrade, and is a good choice for preparing a flexible electromagnetic shielding material by compounding with MXene.
The MXene electromagnetic shielding material belongs to metal carbide or nitride, and has high conductivity, so that the MXene electromagnetic shielding material has good electromagnetic shielding performance. At present, research discovers Ti 3 C 2 T x The conductivity of the material can reach 4665.1S/cm, and the thickness of Ti is 45 mu m 3 C 2 T x The electromagnetic shielding efficiency of the film can reach more than 92 dB. In addition to the layered structure of MXene and its ability to combine well with polymers, MXene materials have become a focus of research in current electromagnetic shielding materials. Meanwhile, inorganic components MXene and silk fibers are compounded into a porous membrane, so that a more abundant structural space can be provided, and the silk fibroin is added, so that the silk fibroin is connected to the MXene in a hydrogen bond manner, and the mechanical strength and the biology are enhancedCompatibility, response to pressure is also more pronounced, thus making the best of favor. Combining inorganic components with organic components to form this flexible MXene protein composite membrane is an effective way to obtain high performance barrier skin.
Disclosure of Invention
The invention aims to provide a flexible MXene protein composite membrane with electromagnetic shielding and pressure-sensitive characteristics, a preparation method and application thereof, which are used for solving the defects of poor mechanical property, small strain range, serious pollution and nondegradable in the production process, poor biocompatibility and the like of the traditional metal or semiconductor electromagnetic shielding material and prolonging the service life and the practicability of the composite material to the maximum extent.
The invention relates to a preparation method of a flexible MXene protein composite membrane with electromagnetic shielding and pressure sensitivity characteristics, which comprises the steps of firstly adopting a method in a document (DOI: 10.1021/acs. Chemnater.7b02847) to etch MAX phase to obtain a few-layer MXene nano-sheet dispersion liquid; simultaneously degumming cocoon shells, adding Hexafluoroisopropanol (HFIP) solution into silk nanofibers obtained after degumming to ensure that the silk nanofibers are well dispersed in a water phase, and obtaining silk nanofiber dispersion liquid; and centrifuging the MXene nano-sheet dispersion liquid, taking supernatant to obtain MXene nano-sheet colloid solution, mixing with silk nano-fiber dispersion liquid, carrying out vacuum auxiliary suction filtration, and naturally drying to obtain the flexible MXene protein composite membrane. According to the invention, the flexible MXene protein composite membrane with different electromagnetic shielding effectiveness and mechanical properties can be obtained by changing the mass ratio of MXene to silk nanofiber. Due to the excellent conductivity of MXene itself and the structural properties of the nanofibers, a conductive network is formed. The obtained composite film has electromagnetic shielding performance and flexibility, and also has good pressure-sensitive characteristic and degradability. Due to the ultrathin and portable wearable property, the nano-composite material can be used in the military field, artificial intelligence and daily protection, and has a good application prospect.
The invention relates to a preparation method of a flexible MXene protein composite membrane with electromagnetic shielding and pressure sensitivity characteristics, which comprises the following steps:
(1) Degumming silk fiber prepared by sodium carbonate degumming method:cutting the dried silkworm cocoon shell into 8-12 mm 2 The obtained silkworm cocoon shell fragments are slowly added into Na (to increase the contact area of the silkworm cocoon shell and the degumming liquid) 2 CO 3 Magnetically stirring in water solution at 90-110 deg.c for 1.0-2.0 hr to degumm; taking out degummed silk, soaking in distilled water, washing thoroughly, and removing residual Na 2 CO 3 And sericin on the surface; finally, the silk is torn into 4 to 6mm 2 Naturally drying the left and right small blocks at room temperature to obtain degummed silk fibers;
(2) Liquid stripping of degummed silk fibers: dripping Hexafluoroisopropanol (HFIP) solution into the degummed silk fiber obtained in the step (1) by using a top-down method, fully mixing and fully immersing the degummed silk fiber, sealing a container filled with the degummed silk fiber/HFIP mixture, and then heating and incubating for 20-30 h in a water bath at 50-70 ℃ to obtain silk fiber pulp;
(3) Dripping the silk fiber paper pulp with the completely volatilized solvent in the step (2) into distilled water, continuously stirring or oscillating until the silk fiber paper pulp is uniformly mixed, and filtering out insoluble silk sediment; performing ultrasonic treatment and centrifugation on the obtained mixture by utilizing an ultrasonic stripping method, and removing silk fiber precipitates which are incompletely degummed or clustered together to obtain silk nanofiber dispersion liquid;
(4) Preparing MXene nano-sheet dispersion liquid by using LiF and HCl etching method, centrifuging the MXene nano-sheet dispersion liquid, and obtaining supernatant to obtain MXene nano-sheet colloid solution; and mixing 10-20 mg/mL of MXene nano-sheet colloidal solution and 10-20 mg/mL of silk nano-fiber dispersion liquid according to the mass ratio of 1: 1-3, mixing and stirring uniformly; finally, vacuum assisted suction filtration is carried out to obtain a filter cake, and the filter cake is naturally dried to obtain the flexible MXene protein composite membrane.
Step (1) Na 2 CO 3 Na in aqueous solution 2 CO 3 The mass fraction of the silk cocoon shell fragments and Na is 1wt% 2 CO 3 The mass ratio of the aqueous solution is 1: 260-300 parts;
in the step (2), the mass ratio of the degummed silk fiber to the HFIP solution is 1: 30-50, placing silk fiber pulp in a fume hood for drying, and completely volatilizing an organic solvent HFIP;
the mass ratio of the silk nanofiber dispersion liquid to distilled water in the step (3) is 1: 180-220, and the ultrasonic time is 0.5-2.0 hours; the centrifugal time is 15-30 minutes, and the centrifugal rotating speed is 8000-12000 revolutions per minute. Because HFIP solvents are toxic and volatile, all of the above operations are performed in a fume hood and the necessary protective measures are taken.
The surface of the flexible MXene protein composite membrane obtained in the step (4) is free of holes, unobvious in fluctuation and smoother in surface. And (3) carrying out electromagnetic shielding performance tests on the prepared pure MXene film and the flexible MXene protein composite film on X, ku and K wave bands, wherein the total electromagnetic shielding efficiency of the flexible MXene protein composite film on X, ku and K wave bands is more than 45dB, which indicates that the electromagnetic shielding performance of the flexible MXene protein composite film is good. In contrast to pure MXene films, flexible MXene protein composite films can be bent multiple times to film edge registration without breaking.
The flexible MXene protein composite membrane obtained in the step (4) can be applied to the fields of electromagnetic shielding protection, pressure sensors and the like.
The flexible MXene protein composite membrane with electromagnetic shielding and pressure sensitivity characteristics is prepared by the method.
The invention has the advantages that:
the invention uses sensitization strategy from the perspective of researching and preparing the flexible MXene-based electromagnetic shielding composite film, enhances the flexibility of the film through the combination of silk nanofiber and MXene, and simultaneously maintains better electromagnetic shielding performance. The MXene protein composite film is prepared by using a vacuum auxiliary suction filtration method, a LiF and HCl etching method, a sodium carbonate degumming method, an ultrasonic stripping method and the like, and the morphology structure, the electromagnetic shielding performance and the flexibility of the MXene protein composite film are researched. Silk Nanofiber (SNF) is a common natural protein fiber material and has excellent biocompatibility, mechanical properties and environmental sustainability, so that the invention provides an application of a SNF and MXene composite method in flexible electronic products. The innovation point of the invention is that the prepared silk nanofiber is used as a material for enhancing the flexibility of MXene, the aramid nanofiber, the bacterial cellulose and the like are compounded to enhance the research result of the flexibility at present, and the silk nanofiber has the advantages of good biocompatibility and better mechanical property, so that the MXene film compounded with the silk nanofiber has better application potential on wearable equipment. Given the abundance of surface functional groups (H, O or F elements) in MXene, hydrogen bonds are formed between SNF and MXene. These bonds connect the MXene nanoflakes together, increasing mechanical strength, and may be packaged as a flexible and wearable device. The silk nanofiber is used as an intercalation agent and a bridging agent, and can self-assemble several layers of MXene into a continuous parallel sheet form with a three-dimensional internal cross-linked structure, so that the strain capacity of the composite membrane is improved. After the MXene protein composite membrane manufactured by the invention is connected with an electrode and is packaged by a polyurethane film, the MXene protein composite membrane can be used as a pressure sensor to be attached to human skin, and a circuit is connected to collect various vital signs of the human body, even the vital signs which are shown as micro deformation such as wrist pulse and laryngeal vibration. The composite membrane provided by the invention has excellent biocompatibility, high sensitivity, long-term durability, excellent mechanical property and low detection lower limit, and can be applied to various fields such as next-generation artificial skin, personal health care wearable equipment and the like. Finally, the preparation method provided by the invention has the advantages of easily available raw materials, simple and safe operation and easy realization of industrial mass production.
Drawings
Fig. 1: cross-sectional scanning electron microscopy (sem) image of pure MXene film (obtained from MXene nanoplatelet dispersion by vacuum filtration, drying) with the same mass of MXene protein composite film (SM) as the dispersion obtained in example 3. The intercalation of silk nano fibers can find that the silk nano fibers adjust the interlayer spacing of the MXene nano sheets so as to further improve the sensitivity of the composite film to pressure and the electromagnetic shielding performance;
fig. 2: a spectrum analysis chart corresponding to a cross-sectional scanning electron microscope chart (fig. 1) of the MXene protein composite membrane obtained in example 3; the energy spectrum analysis chart shows that: the distribution of C, O, N and Ti is consistent with the distribution of the MXene protein composite membrane layered structure, which shows that the MXene and silk nanofibers are uniformly and fully compounded;
fig. 3: the flexible MXene protein composite films obtained in examples 1, 2 and 3 have electromagnetic shielding efficiency curves for electromagnetic waves when the flexible MXene protein composite films have the same thickness (35 μm is uniformly selected); the first, second and third sequences represent the three MXene protein composite membranes obtained in examples 1, 2 and 3, respectively.
Electromagnetic shielding effectiveness (EMI SE) is a measure of the ability of a material to attenuate electromagnetic waves, the Total electromagnetic shielding effectiveness (Total EMI SE) (SE T ) Is defined as the logarithm of the ratio of the incident power (Pi) to the transmitted power (Pm) of the electromagnetic wave, the total Shielding Effectiveness (SE) in decibels (dB) T ) Including absorption losses (SE) associated with multiple reflections at the interface, electric dipoles and mobile charge carriers A ) And reflection loss (SE R ). The abscissa is the electromagnetic wave frequency and the ordinate is the shielding effectiveness, defined as se=20 lg (E 1 /E 2 ) (dB), using a medium-electric forty-one ZV 3672B-S type vector network analyzer to test by using a rectangular waveguide, wherein the electromagnetic wave frequency range is an X wave band (8-12.4 GHz), a Ku wave band (12-18 GHz) and a K wave band (18-26.5 GHz), and each wave band is tested by using a corresponding rectangular waveguide adapter, so that the result can obtain the mass ratio of different silk nanofibers to MXene, the electromagnetic shielding efficiency is different, and the MXene protein composite film obtained in the third embodiment has the highest electromagnetic shielding efficiency;
fig. 4: SE in three bands (X band, ku band and K band) of the MXene protein Complex film obtained in example 3 T 、SE A And SE R Histograms of the mean values, respectively, illustrate the total shielding effectiveness (SE T ) Absorption loss (SE) A ) And reflection loss (SE R ) Ability, SE of (2) T ＝SE R +SE A . From the figure, SE A The contribution to the shielding performance of the composite film is greatest. SE, regardless of the content of nanomaterial in the test frequency range A Are all dominant factors, account for total SE T The average proportion of (2) is about 80%.
Fig. 5: the optical photograph of the conductive ability of the flexible MXene protein composite film obtained in the embodiment 3 under bending, the left graph shows that the flexible MXene protein composite film is bent without breaking, the right graph shows that the flexible MXene protein composite film can be used as a lead to light an LED bulb in a bending state after being cut into a rectangle, so that the flexible MXene protein composite film has better mechanical property and good conductivity, and can be applied to flexible sensing.
Fig. 6: the flexible MXene protein composite membrane obtained in example 2 has a response rate curve (FIG. a) at a pressure of 2.82kPa and a transient response recovery curve (FIG. b) at 48.5kPa, with the inset of FIG. a showing an enlarged detail of 1000 to 1020 turns; the results indicate that the sensor has a good and fast continuous response at a pressure of 2.82 kPa. When the sensor is compressed, the resistance is reduced, and when the pressure is released, the resistance is obviously increased, which indicates that the sensor can distinguish human body signals in real time.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the present invention, but are not to be construed as limiting the scope of the invention.
Example 1:
(1) Degumming silk fiber prepared by sodium carbonate degumming method: cutting dried silkworm cocoon shell into 10mm 2 About small pieces, 5g of broken silkworm cocoon shell pieces are slowly added with 1wt% Na 2 CO 3 In the aqueous solution, the mass ratio is 1:280, boiling and magnetically stirring with a smart magnetic stirrer for 1h. Taking out degummed silk, soaking in distilled water, washing thoroughly, and removing residual Na 2 CO 3 And surface sericin. Finally, the silk is torn into 4 to 6mm 2 Naturally drying the left and right small blocks at room temperature to obtain the degummed silk fiber.
(2) And dripping Hexafluoroisopropanol (HFIP) solution (the mass ratio of the silk fiber to the HFIP solution is 1:40) into the degummed silk fiber, and fully mixing to completely submerge the fiber. The sealed vessel containing the silk fiber/HFIP mixture was heated in a water bath at 60℃and incubated for 24h. And then putting the synthesized silk fiber pulp into a fume hood for drying, so that the HFIP is completely volatilized.
(3) The dried silk fiber pulp is put into distilled water (the mass ratio of silk fiber to distilled water is 1:200), and is continuously stirred or oscillated until the mixture is uniform, and insoluble silk sediment is filtered. The resulting mixture was sonicated using an ultrasonic stripping method for 1 hour at a power of 200W. And centrifuging for 20 minutes at 10000 revolutions per minute, and removing the degummed incomplete or agglomerated silk fiber sediment to obtain Silk Nanofiber (SNF) dispersion. Because HFIP solvents are toxic and volatile, all of the above operations are performed in a fume hood and the necessary protective measures are taken.
(4) Preparing MXene nano-sheet dispersion liquid (DOI: 10.1021/acs. Chemnater.7b02847) according to a method in a literature, centrifuging the MXene nano-sheet dispersion liquid, taking supernatant to obtain MXene nano-sheet colloid solution, and diluting the solution to the concentration of 10 mg/mL; diluting the silk nanofiber dispersion liquid obtained in the step (3) to a concentration of 10mg/mL, and mixing the silk nanofiber dispersion liquid with 10mg/mL of MXene nanosheet dispersion liquid according to a dispersion mass ratio of 1:1, mixing and stirring uniformly. Finally, 15mL of the liquid is taken, vacuum assisted suction filtration and natural drying are carried out on the liquid, and the MXene protein composite membrane with the thickness of about 50 mu m is obtained.
(5) And measuring scattering parameters, namely S parameters, by using a vector network analyzer and adopting a rectangular waveguide method. The reflection loss, absorption loss and electromagnetic shielding efficiency of the material can be calculated through the S parameter. Rectangular MXene protein composite membranes of 25 mm ×10mm, 16×8mm and 11×4mm in size were prepared, and S parameters were measured corresponding to the X-band, the Ku-band and the K-band, respectively.
The average density of the MXene protein composite membrane prepared in this example was 2.18g/cm 3 Conductivity is 3.51X10 3 S/cm. The MXene protein composite film is used for testing the electromagnetic shielding efficiency of three wave bands of electromagnetic wave X wave band, ku wave band and K wave band, so that a certain electromagnetic shielding protection effect can be achieved, and SE thereof T Can reach more than 45 dB. Meanwhile, the flexibility is good, the fracture phenomenon is avoided after the bending for many times, and the obvious protection efficiency loss is avoided; the biocompatibility is good.
Example 2:
(1) Degumming silk fiber by sodium carbonate degumming method: cutting dried silkworm cocoon shell into 10mm 2 About small pieces, 5g of broken silkworm cocoon shell pieces are slowly added with 1wt% Na 2 CO 3 In the water solution, the massThe ratio is 1:280, boiling and magnetically stirring with a smart magnetic stirrer for 1h. Taking out degummed silk, soaking in distilled water, washing thoroughly, and removing residual Na 2 CO 3 And surface sericin. Finally, the silk is torn into 4 to 6mm 2 Naturally drying the left and right small blocks at room temperature to obtain the degummed silk fiber.
(2) And dripping Hexafluoroisopropanol (HFIP) solution (the mass ratio of the silk fiber to the HFIP solution is 1:40) into the degummed silk fiber, and fully mixing to completely submerge the fiber. The sealed vessel containing the silk fiber/HFIP mixture was heated in a 65℃water bath and incubated for 24h. And then putting the synthesized silk fiber pulp into a fume hood for drying, so that the HFIP is completely volatilized.
(3) The dried silk fiber pulp is put into distilled water (the mass ratio of silk fiber to distilled water is 1:200), and is continuously stirred or oscillated until the mixture is uniform, and insoluble silk sediment is filtered. And (3) carrying out ultrasonic treatment on the obtained mixture for 1h by utilizing an ultrasonic stripping method, carrying out centrifugation for 20 minutes at 10000 revolutions per minute, and removing the silk fiber sediment which is incompletely degummed or aggregated together to obtain a Silk Nanofiber (SNF) dispersion liquid. Because HFIP solvents are toxic and volatile, all of the above operations are performed in a fume hood and the necessary protective measures are taken.
(4) Preparing MXene nano-sheet dispersion liquid (DOI: 10.1021/acs. Chemnater.7b02847) according to a method in a literature, centrifuging the MXene nano-sheet dispersion liquid, taking supernatant to obtain MXene nano-sheet colloid solution, and diluting the solution to the concentration of 10 mg/mL; diluting the silk nanofiber dispersion liquid obtained in the step (3) to 10mg/mL, and mixing the silk nanofiber dispersion liquid with 10mg/mL of MXene nanosheet dispersion liquid according to a dispersion mass ratio of 1:2, mixing and stirring uniformly. Finally, 15mL of the liquid is taken, vacuum assisted suction filtration and natural drying are carried out on the liquid, and the MXene protein composite membrane with the thickness of about 40 mu m is obtained.
(5) And measuring scattering parameters, namely S parameters, by using a vector network analyzer and adopting a rectangular waveguide method. The reflection loss, absorption loss and electromagnetic shielding efficiency of the material can be calculated through the S parameter. Rectangular MXene protein composite membranes of 25 mm ×10mm, 16×8mm and 11×4mm in size were prepared, and S parameters were measured corresponding to the X-band, the Ku-band and the K-band, respectively.
The average density of the MXene protein composite membrane prepared in this example was 2.23g/cm 3 Conductivity is 4.80×10 3 S/cm. The MXene protein composite film is used for testing the electromagnetic shielding efficiency of three wave bands of electromagnetic wave X wave band, ku wave band and K wave band, so that a certain electromagnetic shielding protection effect can be achieved, and SE thereof T Can reach more than 50 dB. Meanwhile, the flexibility is good, the fracture phenomenon is avoided after the bending for many times, and the obvious protection efficiency loss is avoided; the biocompatibility is good.
Example 3:
(1) Degumming silk fiber by sodium carbonate degumming method: cutting dried silkworm cocoon shell into 10mm 2 About small pieces, 5g of broken silkworm cocoon shell pieces are slowly added with 1wt% Na 2 CO 3 In the aqueous solution, the mass ratio is 1:280, boiling and magnetically stirring for 2h with a smart magnetic stirrer. Taking out degummed silk, soaking in distilled water, washing thoroughly, and removing residual Na 2 CO 3 And surface sericin. Finally, the silk is torn into 4 to 6mm 2 Naturally drying the left and right small blocks at room temperature to obtain the degummed silk fiber.
(2) And dripping Hexafluoroisopropanol (HFIP) solution (the mass ratio of the silk fiber to the HFIP solution is 1:40) into the degummed silk fiber, and fully mixing to completely submerge the fiber. The sealed vessel containing the silk fiber/HFIP mixture was heated in a water bath at 60℃and incubated for 28h. And then putting the synthesized silk fiber pulp into a fume hood for drying, so that the HFIP is completely volatilized.
(3) The dried silk fiber pulp is put into distilled water (the mass ratio of silk fiber to distilled water is 1:200), and is continuously stirred or oscillated until the mixture is uniform, and insoluble silk sediment is filtered. The resulting mixture was sonicated for 1h using an ultrasonic peel-off method at a power of 200W. And centrifuging for 20 minutes at 10000 revolutions per minute, and removing the degummed incomplete or agglomerated silk fiber sediment to obtain Silk Nanofiber (SNF) dispersion. Because HFIP solvents are toxic and volatile, all of the above operations are performed in a fume hood and the necessary protective measures are taken.
(4) Preparing MXene nano-sheet dispersion liquid (DOI: 10.1021/acs. Chemnater.7b02847) according to a method in a literature, centrifuging the MXene nano-sheet dispersion liquid, taking supernatant to obtain MXene nano-sheet colloid solution, and diluting the solution to a concentration of 20 mg/mL; diluting the silk nanofiber dispersion liquid obtained in the step (3) to 20mg/mL, and mixing the silk nanofiber dispersion liquid with 20mg/mL of MXene nanosheet dispersion liquid according to a dispersion mass ratio of 2:3, mixing and stirring uniformly. Finally, 7.5mL of the liquid is taken, vacuum assisted suction filtration and natural drying are carried out on the liquid, and the MXene protein composite membrane with the thickness of about 45 mu m is obtained.
(5) And measuring scattering parameters, namely S parameters, by using a vector network analyzer and adopting a rectangular waveguide method. The reflection loss, absorption loss and electromagnetic shielding efficiency of the material can be calculated through the S parameter. Rectangular MXene protein composite membranes of 25 mm ×10mm, 16×8mm and 11×4mm in size were prepared, and S parameters were measured corresponding to the X-band, the Ku-band and the K-band, respectively.
The average density of the MXene protein composite membrane prepared in this example was 1.98g/cm 3 Conductivity is 6.37X10 3 S/cm. The MXene protein composite film is used for testing the electromagnetic shielding efficiency of three wave bands of electromagnetic wave X wave band, ku wave band and K wave band, so that a certain electromagnetic shielding protection effect can be achieved, and SE thereof T Can reach more than 57 dB. Meanwhile, the flexibility is good, the fracture phenomenon is avoided after the bending for many times, and the obvious protection efficiency loss is avoided; the biocompatibility is good.

Claims (3)

1. A preparation method of a flexible MXene protein composite membrane with electromagnetic shielding and pressure sensitivity characteristics comprises the following steps:
(1) Degumming silk fiber prepared by sodium carbonate degumming method: cutting the dried silkworm cocoon shell into 8-12 mm 2 Slowly adding the obtained silkworm cocoon shell fragments into Na 2 CO 3 Magnetically stirring in an aqueous solution at 90-110 ℃ for 1.0-2.0 h to perform degumming treatment; taking out degummed silk, soaking in distilled water, washing thoroughly, and removing residual Na 2 CO 3 And sericin on the surface; finally, tearing the silk into 4-6 mm 2 Naturally drying the small pieces at room temperature to obtain degummed silk fibers; na (Na) 2 CO 3 Na in aqueous solution 2 CO 3 The mass fraction of the silk cocoon shell fragments and Na is 1wt% 2 CO 3 The mass ratio of the aqueous solution is 1: 260-300;
(2) Liquid stripping of degummed silk fibers: dropwise adding hexafluoroisopropanol solution into the degummed silk fibers obtained in the step (1) by using a top-down method, fully mixing and fully immersing the degummed silk fibers, sealing a container filled with a degummed silk fiber/hexafluoroisopropanol mixture, and then heating and incubating for 20-30 hours at 50-70 ℃ in a water bath to obtain silk fiber pulp; the mass ratio of the degummed silk fiber to the HFIP solution is 1: 30-50, placing silk fiber pulp in a fume hood for drying, and completely volatilizing an organic solvent HFIP;
(3) Dripping the silk fiber paper pulp with the completely volatilized solvent in the step (2) into distilled water, continuously stirring or oscillating until the silk fiber paper pulp is uniformly mixed, and filtering out insoluble silk sediment; performing ultrasonic treatment and centrifugation on the obtained mixture by utilizing an ultrasonic stripping method, and removing silk fiber precipitates which are incompletely degummed or clustered together to obtain silk nanofiber dispersion liquid; the mass ratio of the silk nanofiber dispersion liquid to distilled water is 1: 180-220, wherein the ultrasonic time is 0.5-2.0 hours; the centrifugation time is 15-30 minutes, and the centrifugation rotating speed is 8000-12000 revolutions per minute;
(4) Preparing MXene nano-sheet dispersion liquid by using LiF and HCl etching method, centrifuging the MXene nano-sheet dispersion liquid, and obtaining supernatant to obtain MXene nano-sheet colloid solution; and mixing 10-20 mg/mL of MXene nano-sheet colloidal solution with 10-20 mg/mL of silk nano-fiber dispersion liquid according to the mass ratio of 1: 1-3, mixing and uniformly stirring; finally, vacuum assisted suction filtration is carried out to obtain a filter cake, and the filter cake is naturally dried to obtain the flexible MXene protein composite membrane.
2. A flexible MXene protein composite membrane having electromagnetic shielding and pressure sensitive properties, characterized in that: is prepared by the method of claim 1.
3. Use of a flexible MXene protein composite membrane having electromagnetic shielding and pressure sensitive properties as defined in claim 2 for electromagnetic shielding protection or pressure sensors.
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