阅读说明：本技术 一种无感式多功能电纺微金字塔阵列膜及其制备方法 (Non-inductive multifunctional electro-spinning micro-pyramid array membrane and preparation method thereof ) 是由 张嘉汉 潘力佳 施毅 陈璐瑶 高兴迅 程燕 涂增源 张树铭 于 2021-10-11 设计创作，主要内容包括：本发明公开了一种无感式多功能电纺微金字塔阵列膜及其制备方法,制备方法包括如下步骤：首先配置聚合物前驱体溶液；再将前驱体溶液加入导电针头,并在针头接通高压电,使得前驱体溶液形成具有异质结构的带电纤维；采用接地的导电接收器持续收集上述纤维；随后,后续喷射的具有异质结构的纤维自发地优先在已收集的纤维更厚的位置进行沉积；其次,在常温条件下挥发溶剂,最终得到具有电纺微金字塔阵列的超轻薄膜。所述膜不仅具有满足长期使用的无感性,而且在压力传感、辐射制冷、压电、摩擦电、亲疏水等方面具备多重超性能。(The invention discloses a non-inductive multifunctional electro-spinning micro pyramid array membrane and a preparation method thereof, wherein the preparation method comprises the following steps: firstly, preparing a polymer precursor solution; adding the precursor solution into a conductive needle, and connecting high voltage to the needle to enable the precursor solution to form a charged fiber with a heterostructure; continuously collecting said fibers with a grounded conductive receiver; subsequently, the subsequently sprayed fibres with heterostructure deposit spontaneously preferentially at the position where the collected fibres are thicker; and secondly, volatilizing the solvent at normal temperature to finally obtain the ultra-light film with the electrospun micro pyramid array. The film not only has no sensibility and multiple super-performances in the aspects of pressure sensing, radiation refrigeration, piezoelectricity, triboelectricity, hydrophilicity and hydrophobicity and the like, and meets the requirement of long-term use.)

1. The non-inductive multifunctional electrospun micro-pyramid array membrane is characterized in that the surface of the electrospun micro-pyramid array membrane is provided with micro-pyramid structures arranged in an array manner; the micro pyramid structure is formed by self-assembling the electrospun micro/nano fiber with the heterostructure under the action of an electric field.

2. The film of claim 1, wherein the number of the edges of the micro-pyramid structures from the bottom to the top is 3-6; the average height of the micro pyramid structure is between 1 μm and 50 μm; the average length of the bottom edge of the micro pyramid structure is between 5 and 200 mu m; the size of the micro pyramid structure has thickness dependency, and the size of the electro-spinning micro pyramid structure is larger along with the increase of the thickness.

3. The non-inductive multifunctional electrospun micro-pyramid array membrane according to claim 2, wherein the number of the micro-pyramid structures per square centimeter of the surface of the electrospun micro-pyramid array membrane is not less than 2000, and the water vapor transmission rate of the electrospun micro-pyramid array membrane exceeds 2.3 kg/(m) m²D) a thickness of not more than 100 μm and a mass per square centimeter of not more than 0.0015 g.

4. The preparation method of the non-inductive multifunctional electrospun micro-pyramid array membrane of claim 1, characterized by comprising the following steps:

1) adding a polymer into a high-boiling-point solvent, heating and stirring to fully dissolve the polymer, standing at 25 ℃, and removing bubbles generated in the stirring process to obtain a polymer precursor solution;

2) adding the polymer precursor solution obtained in the step 1) into a conductive needle, installing a grounded conductive receiver in front of the needle, and electrically connecting a high voltage to the conductive needle to enable the polymer precursor solution to form a charged fiber with a heterostructure sprayed to the conductive receiver under the action of a high voltage electric field;

3) controlling the flow rate of the polymer precursor solution in the conductive needle in the step 2) by using a mechanical pump, so that the charged fibers with the heterogeneous structures are continuously sprayed to the conductive receiver, and meanwhile, the fibers with the heterogeneous structures sprayed subsequently are spontaneously and preferentially deposited at the thicker positions of the collected fibers until all the polymer precursor solution in the conductive needle is completely sprayed to obtain the deposit received by the conductive receiver;

4) drying the sediment received by the conductive receiver in the step 3) at 25 ℃, and obtaining the non-inductive multifunctional electrospun micro-pyramid array membrane after the high-boiling-point solvent is completely volatilized.

5. The method of claim 4, wherein: the polymer in the step 1) is polyvinylidene fluoride, thermoplastic polyurethane elastomer rubber, polyvinyl alcohol or polyamide 66.

6. The method of claim 5, wherein: the high-boiling-point solvent in the step 1) is a mixed solution of dimethyl sulfoxide and acetone which is suitable for dissolving polyvinylidene fluoride and thermoplastic polyurethane elastomer rubber in a volume ratio of 1: 1-3: 1, water which is suitable for dissolving polyvinyl alcohol or formic acid which is suitable for dissolving polyamide 66; the heating and stirring temperature is 50-55 ℃; the standing time is 10-120 min.

7. The method of claim 6, wherein: the polymer precursor solution obtained in the step 1) is a polyvinylidene fluoride solution with the mass concentration of 8-9%, a polyurethane solution with the mass concentration of 20-22%, a polyvinyl alcohol solution with the mass concentration of 9-11% or a polyamide 66 solution with the mass concentration of 4-5%.

8. The method of claim 4, wherein: the size of the conductive needle head in the step 2) is any one of 20, 21, 22 and 23; the distance between the conductive needle head and the grounded conductive receiver is 3 cm-10 cm; the high voltage is 12 kV-25 kV direct current voltage; the humidity of the operating environment is 15-60%; the temperature of the operation environment is 18-35 ℃.

9. The method of claim 4, wherein: the charged fiber having the heterostructure of step 2) is a fiber in which the specific volume surface area periodically varies along the length of the fiber or a fiber in which the specific volume surface areas are different from each other.

10. The method of claim 4, wherein: the flow rate of the precursor solution in the step 3) is 0.8 mL/h-1.0 mL/h.

Technical Field

The invention relates to the technical field of micro-nano manufacturing, in particular to a non-inductive multifunctional electro-spinning micro-pyramid array membrane and a preparation method thereof.

Background

The film device which is non-inductive, multifunctional and can be attached to the skin can simultaneously realize a plurality of functions of long-term health, action and behavior monitoring, personal protection, collection and conversion of biological mechanical energy and the like on a user through a simple integrated structure, and has important functions of improving the health level, the life quality and the working efficiency of human beings. The advanced performance and versatility of various skin-engaging membrane devices derives from the inherent properties of the raw materials and the inherent characteristics and significant enhancement effects of the artificial microstructures. An artificial microstructure array formed by geometric shapes with the characteristic of spatial nonuniform distribution, such as a micro-cone array, a micro-pyramid array, a micro-hemisphere array and a micro-prism array, has excellent physical characteristics in various aspects of electricity, force, light, heat and the like, and endows corresponding devices with multiple functions and excellent performance. For example, the paper published in 2015 of Proceedings of the national Academy of Sciences of the United States of America at 117, page 14657-14666, indicates that the alumina particle-filled polydimethylsiloxane film with pyramidal surface microstructure not only has excellent radiation refrigeration performance but also has good self-cleaning performance. The current techniques for manufacturing artificial microstructure arrays are mainly photolithography and 3D printing. The photolithographic technique results in tight bonding between the polymer matrix and the silicon mold, and the prepared polymer matrix is a dense structure. In addition, the 3D printing type additive manufacturing is generally low in precision. The above-mentioned defects result in a film having a microstructure array on its surface that is thick, heavy, and air impermeable, and thus also has no sensitivity.

Micro/nano fiber structures are another well-known artificial microstructure that can be used to improve the breathability, comfort and utility of skin-engaging membrane devices. Electrostatic spinning is a well-known micro/nano fiber preparation technology, and can be used for manufacturing light films with controllable thickness and designable microstructures. The non-inductive property of the functional device for long-term use by preparing the breathable ultrathin ultra-light film through the electrostatic spinning technology is proved. For example, the paper published in Science 370, 966-970 in 2020 states that the application of an ultra-light, ultra-thin, air-permeable electrospun fiber-based capacitive pressure sensor to the skin of a fingertip can monitor the movement and pressure of the fingertip without being sensed by the human body. In addition, by regulating and controlling the electrostatic spinning process, the density of a functional interface can be improved by designing a micro-nano hierarchical structure, so that various performances of the thin film device, such as sensing sensitivity, electrostatic charge trapping density, electromagnetic wave emissivity, water and heat management capacity, are enhanced. Despite the above advantages, a common problem with electrospinning techniques is the random deposition pattern of the electrospun fibers. This results in that the designability of electrospinning technology is limited mainly to the interior and surface of micro/nanofibers. Although existing three-dimensional electrospinning self-assembly techniques can extend the designability to sub-millimeter and even visible dimensions, the three-dimensional structures produced are neither arrayed nor advantageously shaped to facilitate performance enhancement of skin-conformable membrane devices. The above disadvantages result in very limited adjustability of the electrospinning process, which is not conducive to maximizing the multidisciplinary performance and versatility of the relevant membrane devices. It would be helpful if techniques could be developed for making breathable, ultra-light, ultra-thin films with microarray structures to enable the preparation of conformable skin devices that have both insensitivity to long-term use and versatility.

Disclosure of Invention

The invention provides an insensitive multifunctional electrospinning micro pyramid array film, which has a micro-nano hierarchical structure besides gradient spatial distribution, gradient stress distribution and gradient refractive index, so that the film has excellent multidisciplinary performance and versatility. Meanwhile, due to the ultrathin, ultralight and breathable structure, the electrospun micro-pyramid array membrane is attached to the skin, is not easy to sense and has no sensibility. In addition, the invention also provides a preparation method for preparing the non-inductive multifunctional electrospun micro-pyramid array membrane, and the preparation method has simple process flow and easy operation; the application and popularization of the non-inductive multifunctional electrospinning micro pyramid array membrane are facilitated.

The invention adopts the following technical scheme:

an inductively-free multifunctional electrospun micro-pyramid array membrane, which is composed of electrospun micro/nano fibers with a heterostructure; the surface of the electrospun micro pyramid array membrane is provided with micro pyramid structures arranged in an array manner; the micro pyramid structure is formed by self-assembling the electrospun micro/nano fiber with the heterostructure under the action of an electric field;

furthermore, the number of edges connecting the bottom surface of the micro pyramid structure to the top point is 3-6; the average height of the micro pyramid structure is between 1 μm and 50 μm; the average length of the bottom edge of the micro pyramid structure is between 5 and 200 mu m; the size of the micro pyramid structure has thickness dependency, and the size of the electro-spinning micro pyramid structure is larger along with the increase of the thickness.

Furthermore, the number of the micro pyramid structures on each square centimeter of the surface of the electrospun micro pyramid array membrane is not less than 2000, and the water vapor transmission rate of the electrospun micro pyramid array membrane exceeds 2.3 kg/(m)²D) a thickness of not more than 100 μm and a mass per square centimeter of not more than 0.0015 g.

The preparation method of the non-inductive multifunctional electrospun micro-pyramid array membrane comprises the following steps:

1) adding a polymer into a high-boiling-point solvent, heating and stirring to fully dissolve the polymer, standing at 25 ℃, and removing bubbles generated in the stirring process to obtain a polymer precursor solution;

2) adding the polymer precursor solution obtained in the step 1) into a conductive needle, installing a grounded conductive receiver in front of the needle, and electrically connecting a high voltage to the conductive needle to enable the polymer precursor solution to form a charged fiber with a heterostructure sprayed to the conductive receiver under the action of a high voltage electric field;

3) controlling the flow rate of the polymer precursor solution in the conductive needle in the step 2) by using a mechanical pump, so that the charged fibers with the heterogeneous structures are continuously sprayed to the conductive receiver, and meanwhile, the fibers with the heterogeneous structures sprayed subsequently are spontaneously and preferentially deposited at the thicker positions of the collected fibers until all the polymer precursor solution in the conductive needle is completely sprayed;

4) drying the sediment received by the conductive receiver in the step 3) at 25 ℃, and obtaining the non-inductive multifunctional electrospun micro-pyramid array membrane after the high-boiling-point solvent is completely volatilized;

further, the polymer in the step 1) is polyvinylidene fluoride, thermoplastic polyurethane elastomer rubber, polyvinyl alcohol or polyamide 66;

further, the high-boiling-point solvent is a mixed solution of dimethyl sulfoxide and acetone which is suitable for dissolving polyvinylidene fluoride and thermoplastic polyurethane elastomer rubber in a volume ratio of 1: 1-3: 1, water which is suitable for dissolving polyvinyl alcohol or formic acid which is suitable for dissolving polyamide 66; the heating and stirring temperature is 50-55 ℃; the standing time is 10-120 min.

Further, the polymer precursor solution obtained in the step 1) is a polyvinylidene fluoride solution with the mass concentration of 8-9%, a polyurethane solution with the mass concentration of 20-22%, a polyvinyl alcohol solution with the mass concentration of 9-11% or a polyamide 66 solution with the mass concentration of 4-5%.

Further, the size of the conductive needle in the step 2) is any one of 20, 21, 22 and 23; the distance between the conductive needle head and the grounded conductive receiver is 3 cm-10 cm; the high voltage is 12 kV-25 kV direct current voltage; the humidity of the operating environment is 15-60%; the temperature of the operation environment is 18-35 ℃;

further, the charged fiber having the heterostructure of the step 2) is a fiber in which a specific volume surface area periodically varies along a length of the fiber or a fiber in which specific volume surface areas are different from each other.

Further, the flow rate of the precursor solution in the step 3) is 0.8 mL/h-1.0 mL/h.

The invention has the beneficial effects that:

1) the invention provides a method for preparing an inductionless multifunctional electrospun micro-pyramid array membrane, and the method can be used for preparing an ultra-light and ultra-thin breathable membrane with an electrospun micro-pyramid array on the surface in a large-scale and high-efficiency manner by a single-step electrospinning self-assembly method which is simple in process and easy to operate. Based on the huge filament output and the ultra-fast fiber deposition speed in the electrostatic spinning self-assembly process, the preparation method has the advantages of simplicity, high efficiency and large scale in the aspect of producing the electrospun micro-pyramid array membrane.

2) Compared with the film with the surface provided with the micro pyramid array prepared by the traditional photoetching method or 3D printing method, the electrospinning micro pyramid array film prepared by the invention has good air permeability, ultrathin thickness and ultralight weight, so that the film has no sensitivity; compared with the traditional electrospinning flat membrane, the surface of the electrospinning micro pyramid array membrane prepared by the invention is formed by a three-dimensional microarray structure with multiple physical properties, so that the membrane has the advantages of multiple disciplines and excellent performance and multiple functions; the experimental result shows that compared with the airtight micro pyramid array membrane prepared by the traditional photoetching method, the air permeability of the ultrathin and ultralight air permeable electrospun micro pyramid array membrane prepared by the invention exceeds 2.3 kg/(m)²D) a thickness of not more than 100 μm and a mass per square centimeter of not more than 0.0015 g. The pressure sensing sensitivity, the radiation refrigeration temperature, the triboelectric output voltage, the piezoelectric output voltage, the hydrophobic contact angle and the hydrophilic contact angle of the ultrathin and ultralight breathable electrospun micro pyramid array membrane prepared by the method are 633 times, 1.22 times, 1.53 times, 1.89 times, 1.08 times and 0.88 times of those of the traditional electrospun smooth membrane respectively; the invention is beneficial to developing and building an electrostatic spinning self-assembly theoretical system, and provides a simple and novel mode to realize a non-inductive multifunctional membrane device which can be attached to the skin.

Drawings

FIG. 1 is a schematic view of the structure of an electrospun micro-pyramid array membrane of the present invention.

FIG. 2 is a schematic diagram of the mechanism for forming the electrospun micro-pyramid array of the present invention.

Fig. 3 is a photograph of an object of the electrospun micropyramid array membrane obtained in example 1 of the present invention.

FIG. 4 is a longitudinal-sectional field emission scanning electron microscope image of the electrospun micro-pyramid array film obtained in example 1 of the present invention.

FIG. 5 is a high power field emission scanning electron microscope image of the surface of the electrospun micro-pyramid array membrane obtained in example 1 of the present invention.

Fig. 6 is a field emission scanning electron microscope image illustrating the number of edges connecting the micro pyramid structures from the bottom to the top in the electrospun micro pyramid array film obtained in example 1 of the present invention.

FIG. 7 is a scanning electron microscope image of low power field emission of the surface of the electrospun micro-pyramid array membrane obtained in example 1 of the present invention.

FIG. 8 is a scanning electron microscope image of low power field emission of the cross section of the electrospun micro-pyramid array film obtained in example 1 of the present invention.

FIG. 9 is a scanning electron microscope image of the field emission of the conventional electrospun flat film obtained in comparative example 2 of the present invention.

Fig. 10 is a graph of capacitance pressure sensing curve and pressure sensing sensitivity data of the electrospun micro-pyramid array film obtained in example 1 of the present invention and the conventional electrospun flat film obtained in comparative example 2 of the present invention.

Fig. 11 is a radiation refrigeration temperature-time curve diagram of the electrospun micro-pyramid array film obtained in example 1 of the present invention and the conventional electrospun flat film obtained in comparative example 2 of the present invention.

Fig. 12 is a graph of the triboelectric output voltage of the electrospun micropyramid array film obtained in example 1 of the present invention and the conventional electrospun flat film obtained in comparative example 2 of the present invention.

Fig. 13 is a piezoelectric output voltage curve diagram of the electrospun micro-pyramid array film obtained in example 1 of the present invention and the conventional electrospun flat film obtained in comparative example 2 of the present invention.

Fig. 14 is a graph of hydrophobic contact angle data for electrospun micropyramid array membranes obtained in example 1 of the present invention and for conventional electrospun flat membranes obtained in comparative example 2 of the present invention.

Fig. 15 is a graph showing hydrophilic contact angle data of the electrospun micropyramid array membrane prepared in example 1 of the present invention and the conventional electrospun flat membrane prepared in comparative example 2 of the present invention after being coated with the same polyamide 66.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the following description will be made in conjunction with the practical research results of the inventors, and the following description is only used to illustrate the technical solution of the present invention and not to limit the same.

A preparation method of an inductionless multifunctional electrospun micro-pyramid array membrane comprises the following steps:

1) adding a polymer into a high-boiling-point solvent, heating and stirring at a temperature lower than the boiling point of the solvent to fully dissolve the polymer, standing at 25 ℃, and removing bubbles generated in the stirring process to obtain a polymer precursor solution;

the polymer is any one of polyvinylidene fluoride, thermoplastic polyurethane elastomer rubber, polyvinyl alcohol and polyamide 66; the high boiling point solvent is a mixed solution of dimethyl sulfoxide and acetone which is suitable for dissolving polyvinylidene fluoride and thermoplastic polyurethane elastomer rubber in a volume ratio of 1: 1 to 3: 1, water which is suitable for dissolving polyvinyl alcohol, and a corresponding solvent in formic acid which is suitable for dissolving polyamide 66; the heating and stirring temperature is 50-55 ℃; the standing time is 10-120 min; the polymer precursor solution is any one of a polyvinylidene fluoride solution with the mass concentration of 8-9%, a polyurethane solution with the mass concentration of 20-22%, a polyvinyl alcohol solution with the mass concentration of 9-11% and a polyamide 66 solution with the mass concentration of 4-5%.

2) Adding the polymer precursor solution obtained in the step 1) into a conductive needle, installing a grounded conductive receiver in front of the needle, electrically connecting a high voltage to the conductive needle, and enabling the polymer precursor solution to form a charged fiber with a heterostructure sprayed to the conductive receiver under the action of a high voltage electric field under the conditions of certain humidity and temperature;

the size of the conductive needle head is any one of 20, 21, 22 and 23; the distance between the conductive needle head and the grounded conductive receiver is 3 cm-10 cm; the high voltage is 12 kV-25 kV direct current voltage; the humidity of the operating environment is 15-60%; the temperature of the operation environment is 18-35 ℃; the charged fiber having a heterostructure is any of a fiber in which a specific volume surface area periodically varies along a fiber length and a fiber in which the specific volume surface areas are different from each other.

3) Controlling the flow rate of the polymer precursor solution in the conductive needle in the step 2) to be 0.8-1.0 mL/h by using a mechanical pump, so that the charged fibers with the heterogeneous structures are continuously sprayed to the conductive receiver, and simultaneously, the fibers with the heterogeneous structures sprayed subsequently are spontaneously and preferentially deposited at the thicker positions of the collected fibers until all the polymer precursor solution in the conductive needle is completely sprayed;

4) drying the sediment received by the conductive receiver in the step 3) at 25 ℃, and obtaining the non-inductive multifunctional electrospun micro-pyramid array membrane after the high-boiling-point solvent is completely volatilized;

as shown in fig. 1, the obtained electrospun micro-pyramid array membrane is composed of electrospun micro/nanofibers with a heterostructure; the surface of the electrospun micro pyramid array membrane is provided with a micro pyramid array structure; the micro pyramid structure is formed by self-assembling the electrospun micro/nano fiber with the heterostructure under the action of an electric field; the number of the edges of the micro pyramid structure from the bottom surface to the top point is 3-6; the number of the micro pyramid structures on each square centimeter of the surface of the electro-spinning micro pyramid array film is not less than 2000, and the average height of the micro pyramid structures is between 1 and 50 micrometers; the average length of the bottom edge of the micro pyramid structure is between 5 and 200 mu m; the size of the micro pyramid structure has thickness dependency, and the larger the size of the electro-spinning micro pyramid structure is along with the increase of the thickness; the water vapor transmission rate of the electrospun micro pyramid array membrane exceeds 2.3 kg/(m)²D) a thickness of not more than 100 μm and a mass per square centimeter of not more than 0.0015 g.

Example 1

1) Adding polyvinylidene fluoride into a mixed solution of dimethyl sulfoxide and acetone in a volume ratio of 2: 1, stirring at 50 ℃ to fully dissolve the polyvinylidene fluoride, standing at 25 ℃ for 15min, and removing bubbles generated in the stirring process to obtain a polyvinylidene fluoride solution with the mass concentration of 8.59%;

2) adding the polyvinylidene fluoride solution obtained in the step 1) into a No. 22 conductive needle, installing a grounded conductive receiver at a position 8cm in front of the needle, electrically connecting a 12.5kV direct current high voltage with the conductive needle, and enabling the polyvinylidene fluoride solution to form fibers which are sprayed to the conductive receiver and have the specific volume surface area periodically changed along the length of the fibers under the action of a high voltage electric field under the environment of 40% humidity and 25 ℃;

3) controlling the flow rate of the polyvinylidene fluoride solution in the conductive needle head in the step 2) to be 1.0mL/h by using a mechanical pump, continuously injecting the fibers with the specific volume surface area periodically changing along the length of the fibers into the conductive receiver, and simultaneously, spontaneously and preferentially depositing the fibers with the specific volume surface area periodically changing along the length of the fibers in the subsequent injection at a position where the collected fibers are thicker until all the polyvinylidene fluoride precursor solution in the conductive needle head is completely injected;

as shown in fig. 2, a charged fiber with a heterostructure is ejected from a conductive needle under the combined action of electrostatic and surface tension forces, and the influence of the surface tension on the jet is greater than coulomb repulsion. The charged fibers just ejected are positively charged, but the charged fibers just ejected are not limited to being positively charged. The term heterostructure fiber having a periodic variation of the specific volume surface area along the length of the fiber is used for example, but not limited thereto. When the first positively charged fibers are close to the grounded conductive receiver, the conductive receiver surface exhibits an opposite negative charge due to electrostatic induction. Once the positively charged fibers contact the conductive receiver, the sites on the fibers having a larger specific surface area are still positively charged, whereas the negative charge is transferred to the sites on the fibers having a smaller specific surface area. This is because the high-boiling point solvent in the position of the fiber having a large specific surface area is completely volatilized during the fiber spraying process, and the insulation at this position is good. In contrast, during fiber spraying, the high boiling point solvent on the fiber at the location of the smaller specific volume surface area cannot completely evaporate, making this location poorly insulating, and not continuously binding the positive charge that existed before it was in contact with the conductive receiver. The positively charged deposition areas on the receiver repel the next batch of positively charged fibers. Instead, the subsequently ejected jet is attracted to the negatively charged deposition zone on the receiver, forming a new thicker negatively charged deposition zone. After a certain period of time, hemispherical three-dimensional protrusions consisting of fibers are formed. At the same time, the electrostatic induction and polarization of the electrostatic field further negatively charges the tops of the hemispherical three-dimensional protrusions. In addition, a single fiber is always deposited on the tops of the adjacent hemispherical three-dimensional protrusions to form suspended fibers. The suspended fiber is a prototype of an electro-spun micro-pyramid prism structure. The subsequently ejected charged fibers tend to deposit at higher locations due to the higher location on the three-dimensional protrusions having a stronger local electric field and being closer to the subsequently ejected charged fibers. Meanwhile, the suspended fibers serve as a frame to receive the charged fibers sprayed subsequently, and a prism structure is gradually formed. With the continuous electrostatic spinning self-assembly process, the hemispherical three-dimensional protrusion array is evolved into an electrospun micro pyramid array. As the number of deposited fibers increases, adjacent highly adjacent electrospun micropyramids can be fused into larger electrospun micropyramids. For the adjacent electrospinning micro pyramids with different heights, because the higher position has a higher local electric field, the growth speed of the higher electrospinning micro pyramid is far higher than that of the lower electrospinning micro pyramid, and the lower electrospinning micro pyramid is gradually covered by the deposited fibers along with the continuous increase of the deposited fibers, and only the higher electrospinning micro pyramid is shown. Therefore, the size of the micro-pyramid structure has thickness dependence, and the size of the micro-pyramid structure is larger along with the increase of the thickness.

4) Drying the sediment received by the conductive receiver in the step 3) at 25 ℃, and obtaining an insensitive multifunctional electrospinning micro pyramid array membrane (shown in figure 3) after the mixed solvent of dimethyl sulfoxide and acetone is completely volatilized; the electrospun micro-pyramid array membrane is composed of electrospun micro/nanofibers with specific volume surface area periodically varying along the length of the fiber (as shown in fig. 4); the surface of the electrospun micro pyramid array membrane has a micro pyramid array structure (as shown in fig. 5); the micro pyramid structure is formed by self-assembling the electro-spinning micro/nano-fibers with the specific volume surface area periodically changing along the length of the fiber under the action of an electric field; the number of the edges of the micro pyramid structure from the bottom surface to the top point is 3-6 (as shown in FIG. 6); the number of the micro pyramid structures per square centimeter of the surface of the electrospun micro pyramid array film is about 4489(ii) as shown in fig. 7, the average height of the micro-pyramid structures is 24.75 μm; the average length of the bottom edge of the micro pyramid structure is 41.77 mu m; the water vapor transmission rate of the electrospun micro pyramid array membrane is 2.428 kg/(m)²D) overall thickness of 46 μm (as shown in fig. 8), mass per square centimeter of 0.0011 g.

Comparative example 1

The thickness of the polymer film with the surface provided with the micro pyramid array prepared by the traditional photoetching method is 500 mu m, the mass per square centimeter is 0.066g, the whole structure is an airtight compact structure, and the water vapor transmission rate is 0.0001 kg/(m)²D). Therefore, the polymer film with the surface provided with the micro pyramid array prepared by the traditional photoetching method has no non-sensitivity. Compared with the polymer film with the surface provided with the micro pyramid array prepared by the traditional photoetching method, the electrospun micro pyramid array film prepared in the example 1 has ultrathin thickness, ultralight weight and good air permeability, so that the film has no sensibility for long-term use.

Comparative example 2 (electrospinning flat film prepared by conventional electrospinning process)

1) Adding polyvinylidene fluoride into a mixed solution of dimethyl sulfoxide and acetone in a volume ratio of 2: 1, stirring at 50 ℃ to fully dissolve the polyvinylidene fluoride, standing at 25 ℃ for 15min, and removing bubbles generated in the stirring process to obtain a polyvinylidene fluoride solution with the mass concentration of 8.59%;

2) adding the polyvinylidene fluoride solution obtained in the step 1) into a No. 22 conductive needle, installing a grounded conductive receiver at a position 8cm in front of the needle, electrically connecting a 10.0kV direct current high voltage with the conductive needle, and enabling the polyvinylidene fluoride solution to form fibers which are sprayed to the conductive receiver under the action of a high voltage electric field under the environment of 40% humidity and 25 ℃;

controlling the flow rate of the polyvinylidene fluoride solution in the conductive needle in the step 2) to be 1.0mL/h by using a mechanical pump, and continuously spraying the fibers to the conductive receiver and uniformly depositing the fibers on the conductive receiver until all the polyvinylidene fluoride precursor solution in the conductive needle is completely sprayed;

drying the deposit received by the conductive receiver in the step 3) at 25 ℃ to obtain a traditional electrospinning flat membrane (as shown in fig. 9) after the mixed solvent of dimethyl sulfoxide and acetone is completely volatilized; the surface of the electrospinning flat film is free of a three-dimensional protrusion array structure; the total thickness of the traditional electrospinning flat film is 36 mu m, and the mass per square centimeter is 0.0011 g.

The capacitance pressure sensing curve and pressure sensing sensitivity data of the non-inductive multifunctional electrospun micro-pyramid array membrane prepared in example 1 and the conventional electrospun flat membrane prepared in comparative example 2 are shown in fig. 10; the temperature-time curves of the radiation refrigeration of the non-inductive multifunctional electrospun micropyrat array membrane prepared by example 1 and the conventional electrospun flat membrane prepared by comparative example 2 are shown in fig. 11; the triboelectric output voltage curves of the non-inductive multifunctional electrospun micropyrat array membrane prepared by example 1 and the conventional electrospun flat membrane prepared by comparative example 2 are shown in fig. 12; piezoelectric output voltage curves of the non-inductive multifunctional electrospun micro-pyramid array membrane prepared by example 1 and the conventional electrospun flat membrane prepared by comparative example 2 are shown in fig. 13; hydrophobic contact angle data for the non-inductive multifunctional electrospun micropyrate array membrane prepared by example 1 and the conventional electrospun flat membrane prepared by comparative example 2 are shown in fig. 14; the hydrophilic contact angle data of the non-inductive multifunctional electrospun micropyrate array membrane prepared in example 1 and the conventional electrospun flat membrane prepared in comparative example 2 after being respectively subjected to the same polyamide 66 coating treatment are shown in fig. 15.

As can be seen from FIG. 10, the capacitance pressure sensing sensitivity of the non-inductive multifunctional electrospun micro-pyramid array film prepared by example 1 and the conventional electrospun flat film prepared by comparative example 2 was 19kPa respectively^-1With 0.03kPa^-1(ii) a As can be seen from fig. 11, the radiation refrigeration temperatures of the non-inductive multifunctional electrospun micro-pyramid array film prepared by example 1 and the conventional electrospun flat film prepared by comparative example 2 were 3.3 ℃ and 2.7 ℃, respectively; as can be seen from fig. 12, the triboelectric output voltages of the non-inductive multifunctional electrospun micro-pyramid array film prepared by example 1 and the conventional electrospun flat film prepared by comparative example 2 were 26.9V and 17.6V, respectively; as can be seen from FIG. 13, according to example 1The piezoelectric output voltages of the prepared non-inductive multifunctional electrospun micro-pyramid array membrane and the traditional electrospun flat membrane prepared by the comparative example 2 are 6.8V and 3.6V respectively; as can be seen from fig. 14, the hydrophobic contact angles of the non-inductive multifunctional electrospun micropyramid array film prepared by example 1 and the conventional electrospun flat film prepared by comparative example 2 were 154.9 ° and 143.1 °, respectively; as can be seen from fig. 15, the non-inductive multifunctional electrospun micropyramid array membrane prepared in example 1 and the conventional electrospun flat membrane prepared in comparative example 2 respectively have hydrophilic contact angles of 72.1 ° and 81.4 ° after being coated with the same polyamide 66. The structure of the electrospinning micro pyramid array structure enhances the sensing performance, the radiation refrigeration performance, the frictional electrical performance, the piezoelectric performance, the hydrophobic performance and the hydrophilic performance of the conformable skin membrane. The results show that the unique physical properties of the electrospun micro-pyramid array endow the skin-attachable device with good multidisciplinary performance and versatility.

In conclusion, the ultra-light, ultra-thin and breathable skin-conformable film with the electrospun micro-pyramid structure on the surface is prepared. The ultra-light, ultra-thin, breathable structure gives the skin-conformable film a non-sensivity for long-term use; meanwhile, the electrospun micro-pyramid structure endows the membrane capable of being attached to the skin with good versatility in the aspects of pressure sensing, radiation refrigeration, piezoelectricity, triboelectricity, hydrophilicity and hydrophobicity and the like.

Although the present invention has been described in detail with reference to the foregoing examples, it will be apparent to one skilled in the art that various changes and modifications can be made, and equivalents can be substituted for elements thereof without departing from the scope of the invention.