阅读说明：本技术 一种超薄透明型碳纳米纤维膜柔性应变传感器及其制备方法 (Ultrathin transparent carbon nanofiber membrane flexible strain sensor and preparation method thereof ) 是由 闫涛 潘志娟 于 2020-07-20 设计创作，主要内容包括：本发明公开了一种超薄透明型碳纳米纤维膜柔性应变传感器及其制备方法,以锌箔纸为纳米纤维接收材料,并利用开槽石墨板夹持纳米纤维膜进行碳化处理,进而获得超薄型纯碳纳米纤维膜。以弹性聚氨酯作为基体,以超薄型碳纳米纤维膜作为导电体,并用导电银胶将碳纳米纤维膜与铜丝相连形成电极,使碳纳米纤维膜包覆于聚氨酯基体中,制得超薄透明型具有高牵伸应变及高灵敏度的柔性应变传感器。本发明可贴附于皮肤表面,检测面部表情的变化和人体关节运动等导致的应变以及声带振动、呼吸等生理信息,并且具有高稳定性；可识别运动过程中人体结构产生的弯曲及牵伸形变。这种传感器可以应用在智能服装及微小形变监测等领域。(The invention discloses an ultrathin transparent carbon nanofiber membrane flexible strain sensor and a preparation method thereof. The elastic polyurethane is used as a matrix, the ultrathin carbon nanofiber membrane is used as a conductor, the carbon nanofiber membrane is connected with a copper wire by conductive silver adhesive to form an electrode, and the carbon nanofiber membrane is coated in the polyurethane matrix to obtain the ultrathin transparent flexible strain sensor with high drawing strain and high sensitivity. The invention can be attached to the surface of the skin, detects the change of facial expression, strain caused by human joint movement and the like, and physiological information such as vocal cord vibration, respiration and the like, and has high stability; the bending and stretching deformation of the human body structure in the process of movement can be identified. The sensor can be applied to the fields of intelligent clothing, micro-deformation monitoring and the like.)

1. The utility model provides a flexible strain transducer of ultra-thin transparent type carbon nanofiber membrane which characterized in that: the carbon nanofiber membrane comprises a carbon nanofiber membrane with a rectangular regular structure, a first copper wire, a second copper wire and a transparent polyurethane matrix, wherein a connecting end of the first copper wire is fixed at the left end of the carbon nanofiber membrane through conductive silver adhesive, a connecting end of the second copper wire is fixed at the right side of the carbon nanofiber membrane through conductive silver adhesive, the transparent polyurethane matrix coats the connecting end of the first copper wire, the connecting end of the second copper wire and the carbon nanofiber membrane, the transparent polyurethane matrix is in an I-shaped structure, the transparent polyurethane matrix is divided into a left matrix, a connecting matrix and a right matrix, the length of the connecting matrix is 10-40 mm, the thickness of the carbon nanofiber membrane is 0.9-3.92 mu m, the width of the carbon nanofiber membrane is 5-10 mm, the length of the carbon nanofiber membrane is 40-70 mm, the difference between the length of the carbon nanofiber membrane and the length of the connecting matrix is 30mm, and the distance between the first copper wire and the end point of the left end of the carbon nanofiber membrane is 5-10 mm, the distance between the second copper wire and the right end point of the carbon nanofiber membrane is 5-10 mm, the distance between the first copper wire and the second copper wire is 30-60 mm, the width of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 25mm, the length of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 70mm, and the thickness of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 80-200 micrometers.

2. A preparation method of an ultrathin transparent carbon nanofiber membrane flexible strain sensor is characterized by comprising the following steps:

(1) coating zinc foil paper on the surface of a roller rotating at a high speed, and obtaining a polyacrylonitrile/graphene composite nanofiber membrane by controlling spinning time and the rotating speed of a receiving roller by using a single-needle electrostatic spinning method;

(2) clamping a polyacrylonitrile/graphene composite nanofiber membrane containing zinc foil paper between two porous ceramic plates, performing pre-oxidation treatment in the air atmosphere, preparing a graphite plate, wherein the graphite plate is provided with a rectangular groove, a plurality of semicircular holes are formed in the edge of the groove, the depth of each semicircular hole is the same as that of the groove, placing the carbon nanofiber membrane containing the zinc foil paper after the pre-oxidation treatment in the groove, covering the carbon nanofiber membrane with the rectangular groove by using another flat graphite plate, performing carbonization treatment in the argon atmosphere, and evaporating the zinc foil paper in the carbonization process to obtain a pure ultrathin carbon nanofiber membrane;

(3) shearing the pure ultrathin carbon nanofiber membrane along the orientation direction of the pure ultrathin carbon nanofiber membrane or in the direction perpendicular to the orientation direction to prepare the carbon nanofiber membrane with a rectangular regular structure;

(4) preparing a polyurethane solution with the mass fraction of 5%, fixing two ends of the rectangular carbon nanofiber membrane with the regular structure on a glass slide by using a first copper wire and a second copper wire, the distance between the connecting end of the first copper wire and the left end point of the carbon nanofiber membrane with the rectangular regular structure is 5-10 mm, the distance between the connecting end of the second copper wire and the right end point of the carbon nanofiber membrane with the rectangular regular structure is 5-10 mm, then the two ends of the carbon nanofiber membrane with the rectangular regular structure are fixed by using less than 0.05g of polyurethane solution with the mass fraction of 5%, the carbon nanofiber membrane with the rectangular regular structure is respectively connected with the connecting end of the first copper wire and the connecting end of the second copper wire by using conductive silver adhesive, drying at 60 deg.C for 0.5h to form left and right electrodes;

(5) fixing the edge of the carbon nanofiber membrane between the left electrode and the right electrode on the glass slide by taking less than 0.1g of polyurethane solution with the mass fraction of 5%;

(6) preparing a polyurethane solution with the mass fraction of 5% -15%, quickly spreading the polyurethane solution to the surface of a carbon nanofiber membrane, uniformly spreading the polyurethane solution by using a silver needle, and carrying out hot air treatment until the polyurethane solution is completely dried to form a transparent polyurethane matrix, so as to obtain a primary sensor;

(7) standing for two days at room temperature, removing the primary sensor from the glass slide, wrapping the carbon nanofiber membrane in the polyurethane matrix, and cutting the primary sensor into an I-shaped structure along the edge of the carbon nanofiber membrane to form the ultrathin transparent carbon nanofiber membrane flexible strain sensor.

3. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (1), the mass fraction of graphene in the polyacrylonitrile/graphene composite nanofiber membrane is 1%.

4. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (1), the thickness of the zinc-foil paper is 10-25 μm, the spinning time is 10-45 min, the rotating speed of the roller is 200-1000 rpm, and the orientation degree of the polyacrylonitrile/graphene composite nanofiber membrane is 28.1% -61.7%.

5. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (2), the depth of the groove is 0.2-0.5 mm, and the radius of the semicircular hole is 0.2-0.5 mm.

6. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (2), the pre-oxidation treatment condition is 270 ℃/1.5h, the carbonization treatment condition is 1100 ℃/3h, and the thickness of the pure ultrathin carbon nanofiber membrane is 0.9-3.92 μm.

7. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (3), the carbon nanofiber membrane with the rectangular regular structure has a width of 5-10 mm and a length of 40-70 mm.

8. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (4), the distance between the left electrode and the right electrode is 30-60 mm.

9. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (6), the temperature of the hot air treatment is 60 ℃.

10. The method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor as claimed in claim 2, wherein the method comprises the following steps: in the step (7), the width of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 25mm, the length of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 70mm, and the thickness of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 80-200 microns.

Technical Field

The invention belongs to the technical field of sensor materials, and particularly relates to an ultrathin transparent carbon nanofiber membrane flexible strain sensor and a preparation method thereof.

Background

The sensor for researching flexibility, high strain and high sensitivity becomes one of hot directions for developing intelligent wearable equipment, has excellent performances such as high flexibility, high strain and high sensitivity, can be widely applied to the field of wearable electronic products, and can be used for monitoring human motion and physiological information or used for a human-computer interaction system. The traditional metal sheet and semiconductor sensor can only be used under the condition of micro strain, and have the advantages of high rigidity, difficult bending and low sensitivity, so the development of the flexible high-strain/high-sensitivity strain sensor has great significance. The flexible strain sensor reported at present mainly uses conductive nano materials and conductive polymers as conductive media, such as nano silver wires, gold/silver nano particles, nano carbon black, graphene, carbon nano tubes, carbon nano fiber films and carbon nano fiber yarns, polypyrroles, poly 3, 4-ethylenedioxythiophene/polystyrene sulfonate, polyaniline and the like, and there are also related reports of carbonizing common cotton fabrics, silk fabrics and hemp fabrics to obtain carbon fiber fabrics and designing the strain sensor. In order to improve the sensitivity of the sensor in different strain stages, some researchers have mixed a variety of conductive materials with different structures. The structure of the conductive material in the sensor mainly comprises a structure which is uniformly mixed with a polymer, a membrane structure, a yarn structure, a sponge structure, a fabric structure and the like. Up to now, there has been no report on researchers designing flexible strain sensors with a thickness of less than 200 μm using highly light transmissive oriented ultrathin carbon nanofiber films (less than 5 μm).

Therefore, the invention provides an ultrathin transparent carbon nanofiber membrane flexible strain sensor and a preparation method thereof, and aims to develop a flexible strain sensor with the design thickness of less than 200 microns by utilizing a high-light-transmittance oriented ultrathin carbon nanofiber membrane (less than 5 microns).

Disclosure of Invention

The invention aims to provide an ultrathin transparent carbon nanofiber membrane flexible strain sensor and a preparation method thereof.

The invention has a technical scheme that:

a flexible strain sensor of an ultrathin transparent carbon nanofiber membrane comprises a carbon nanofiber membrane with a rectangular regular structure, a first copper wire, a second copper wire and a transparent polyurethane matrix, wherein a connecting end of the first copper wire is fixed at the left end of the carbon nanofiber membrane through conductive silver adhesive, a connecting end of the second copper wire is fixed at the right side of the carbon nanofiber membrane through conductive silver adhesive, the transparent polyurethane matrix coats the connecting end of the first copper wire, the connecting end of the second copper wire and the carbon nanofiber membrane, the transparent polyurethane matrix is of an I-shaped structure, the transparent polyurethane matrix is divided into a left matrix, a connecting matrix and a right matrix, the length of the connecting matrix is 10-40 mm, the thickness of the carbon nanofiber membrane is 0.9-3.92 mu m, the width of the carbon nanofiber membrane is 5-10 mm, the length of the carbon nanofiber membrane is 40-70 mm, and the difference between the length of the carbon nanofiber membrane and the length of the connecting matrix is 30mm, the distance between the first copper wire and the left end point of the carbon nanofiber membrane is 5-10 mm, the distance between the second copper wire and the right end point of the carbon nanofiber membrane is 5-10 mm, the distance between the first copper wire and the second copper wire is 30-60 mm, the width of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 25mm, the length of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 70mm, and the thickness of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 80-200 μm.

The other technical scheme of the invention is as follows:

a preparation method of an ultrathin transparent carbon nanofiber membrane flexible strain sensor comprises the following steps:

(1) coating zinc foil paper on the surface of a roller rotating at a high speed, and obtaining a polyacrylonitrile/graphene composite nanofiber membrane by controlling spinning time and the rotating speed of a receiving roller by using a single-needle electrostatic spinning method;

(2) clamping a polyacrylonitrile/graphene composite nanofiber membrane containing zinc foil paper between two porous ceramic plates, performing pre-oxidation treatment in the air atmosphere, preparing a graphite plate, wherein the graphite plate is provided with a rectangular groove, a plurality of semicircular holes are formed in the edge of the groove, the depth of each semicircular hole is the same as that of the groove, placing the carbon nanofiber membrane containing the zinc foil paper after the pre-oxidation treatment in the groove, covering the carbon nanofiber membrane with the rectangular groove by using another flat graphite plate, performing carbonization treatment in the argon atmosphere, and evaporating the zinc foil paper in the carbonization process to obtain a pure ultrathin carbon nanofiber membrane;

(3) shearing the pure ultrathin carbon nanofiber membrane along the orientation direction of the pure ultrathin carbon nanofiber membrane or in the direction perpendicular to the orientation direction to prepare the carbon nanofiber membrane with a rectangular regular structure;

(4) preparing a polyurethane solution with the mass fraction of 5%, fixing two ends of the rectangular carbon nanofiber membrane with the regular structure on a glass slide by using a first copper wire and a second copper wire, the distance between the connecting end of the first copper wire and the left end point of the carbon nanofiber membrane with the rectangular regular structure is 5-10 mm, the distance between the connecting end of the second copper wire and the right end point of the carbon nanofiber membrane with the rectangular regular structure is 5-10 mm, then the two ends of the carbon nanofiber membrane with the rectangular regular structure are fixed by using less than 0.05g of polyurethane solution with the mass fraction of 5%, the carbon nanofiber membrane with the rectangular regular structure is respectively connected with the connecting end of the first copper wire and the connecting end of the second copper wire by using conductive silver adhesive, drying at 60 deg.C for 0.5h to form left and right electrodes;

(5) fixing the edge of the carbon nanofiber membrane between the left electrode and the right electrode on the glass slide by taking less than 0.1g of polyurethane solution with the mass fraction of 5%;

(6) preparing a polyurethane solution with the mass fraction of 5% -15%, quickly spreading the polyurethane solution to the surface of a carbon nanofiber membrane, uniformly spreading the polyurethane solution by using a silver needle, and carrying out hot air treatment until the polyurethane solution is completely dried to form a transparent polyurethane matrix, thereby obtaining a primary sensor;

(7) standing for two days at room temperature, removing the primary sensor from the glass slide, wrapping the carbon nanofiber membrane in the polyurethane matrix, and cutting the primary sensor into an I-shaped structure along the edge of the carbon nanofiber membrane to form the ultrathin transparent carbon nanofiber membrane flexible strain sensor.

Further, in the step (1), the mass fraction of graphene in the polyacrylonitrile/graphene composite nanofiber membrane is 1%.

Further, in the step (1), the thickness of the zinc-foil paper is 10-25 μm, the spinning time is 10-45 min, the rotating speed of the roller is 200-1000 rpm, and the orientation degree of the polyacrylonitrile/graphene composite nanofiber membrane is 28.1% -61.7%.

Further, in the step (2), the depth of the groove is 0.2-0.5 mm, and the radius of the semicircular hole is 0.2-0.5 mm.

Further, in the step (2), the pre-oxidation treatment is carried out at a temperature of 270 ℃/1.5h, the carbonization treatment is carried out at a temperature of 1100 ℃/3h, and the thickness of the pure ultrathin carbon nanofiber membrane is 0.9-3.92 μm.

Further, in the step (3), the carbon nanofiber membrane with the rectangular regular structure has a width of 5-10 mm and a length of 40-70 mm.

Further, in the step (4), the distance between the left electrode and the right electrode is 30-60 mm.

Further, in the step (6), the temperature of the hot air treatment is 60 ℃.

Further, in the step (7), the width of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 25mm, the length of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 70mm, and the thickness of the ultrathin transparent carbon nanofiber membrane flexible strain sensor is 80-200 μm.

The invention provides an ultrathin transparent carbon nanofiber membrane flexible strain sensor and a preparation method thereof, and the ultrathin transparent carbon nanofiber membrane flexible strain sensor has the advantages that: the cost is low, the energy consumption is low, and the sensor has high transparency, high strain and high sensitivity.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein the content of the first and second substances,

fig. 1 is a schematic structural diagram of a graphite plate with rectangular grooves according to a method for manufacturing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 2 is a schematic flow chart of a method for manufacturing an ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 3 is a diagram illustrating the detection result of a sensor based on a carbon nanofiber membrane (orientation degree 61.7%) parallel to the drafting direction of the sensor on different tensile strains, which is manufactured by the method for manufacturing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 4 is a diagram illustrating the results of knee joint flexion detection by the ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 5 is a diagram showing the pulse vibration detection result of the ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 6 is a diagram showing the detection result of the ultra-thin transparent carbon nanofiber membrane flexible strain sensor for finger bending according to the present invention;

FIG. 7 is a diagram illustrating the result of the flexible strain sensor for an ultra-thin transparent carbon nanofiber membrane in response to acoustic vibrations, in accordance with the present invention;

fig. 8 is a diagram illustrating the detection result of the sensor based on the carbon nanofiber membrane perpendicular to the drafting direction of the sensor on different tensile strains, which is prepared by the method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 9 is a strain sensing curve diagram of a sensor based on a carbon nanofiber membrane perpendicular to a sensor drafting direction, prepared by the method for preparing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 10 is a diagram illustrating the detection result of the sensor based on the carbon nanofiber membrane (orientation degree 28.1%) parallel to the drafting direction of the sensor on different tensile strains, which is prepared by the method for preparing the ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 11 is a strain sensing curve diagram of a sensor based on a carbon nanofiber membrane (with an orientation degree of 28.1%) parallel to a sensor drafting direction, prepared by the method for preparing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 12 is a drawing illustrating the results of tensile strain measurements of a carbon nanofiber-based sensor with different degrees of orientation, prepared according to a method for preparing an ultra-thin transparent carbon nanofiber membrane flexible strain sensor in accordance with the present invention;

fig. 13 is a diagram illustrating the detection result of the sensor based on the carbon nanofiber membrane (with a width of 10mm) parallel to the drafting direction of the sensor on different tensile strains, which is prepared by the method for preparing the ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 14 is a strain sensing curve diagram of a sensor based on a carbon nanofiber membrane (with a width of 10mm) parallel to a drafting direction of the sensor, prepared by the method for preparing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 15 is a diagram illustrating a detection result of tensile strain of a sensor based on carbon nanofibers with different widths prepared by the method for preparing an ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 16 is a diagram illustrating the detection result of the sensor based on the carbon nanofiber membrane (thickness is 3.92 μm) parallel to the drafting direction of the sensor on different tensile strains, which is prepared by the method for preparing the ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

FIG. 17 is a strain sensing curve diagram of a sensor based on a carbon nanofiber membrane (thickness of 3.92 μm) parallel to the drafting direction of the sensor, prepared by the method for preparing an ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention;

fig. 18 is a diagram illustrating a detection result of tensile strain of a sensor based on carbon nanofibers with different thicknesses, which is prepared by the method for preparing an ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention.

Detailed Description

The oriented polyacrylonitrile/graphene composite nanofiber membrane is prepared by an electrostatic spinning method, then the carbon nanofiber membrane with directionally arranged fibers is prepared by pre-oxidation and carbonization, and the carbon nanofiber membrane is compounded with polyurethane to prepare the ultrathin carbon nanofiber membrane flexible strain sensor with low cost, low energy consumption, high transparency, high strain and high sensitivity.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The invention relates to an ultrathin transparent carbon nanofiber membrane flexible strain sensor, which is characterized in that a flexible strain sensor with high strain and sensitivity is prepared by compounding an oriented carbon nanofiber membrane and a polymer. The structure of the carbon nanofiber membrane comprises a carbon nanofiber membrane with a rectangular regular structure, a first copper wire, a second copper wire and a transparent polyurethane matrix, wherein the connecting end of the first copper wire is fixed at the left end of the carbon nanofiber membrane through conductive silver paste, the connecting end of the second copper wire is fixed at the right side of the carbon nanofiber membrane through conductive silver paste, the connecting end of the first copper wire, the connecting end of the second copper wire and the carbon nanofiber membrane are wrapped by the transparent polyurethane matrix, and the transparent polyurethane matrix is of an I-shaped structure. In the structure, the light transmittance of the carbon nanofiber membrane to light with the wavelength of 300-700 nm can reach 50%, the thickness and the orientation degree of the carbon nanofiber membrane can be changed at will by controlling the spinning time and the rotating speed of the receiving roller according to the requirement of sensing performance, and when the roller rotates at 200-1000 rpm, the orientation degree is increased from 28.1% to 61.7%; when the spinning time is 10-45 min, the thickness of the carbon nanofiber film is increased from 0.9 mu m to 3.92 mu m. When the tensile strain is more than 40%, the sensitivity coefficient ((delta R/R0)/(delta L/L0)) reaches more than 140, and the method can be applied to the fields of human body movement, physiological information monitoring, human-computer interaction and the like.

Referring to fig. 2, fig. 2 is a schematic flow chart of a method for manufacturing an ultra-thin transparent carbon nanofiber membrane flexible strain sensor according to the present invention. As shown in fig. 2, the method for preparing the structure comprises:

(1) coating zinc foil paper with the thickness of 10-25 mu m on the surface of a roller rotating at a high speed, and controlling the spinning time and the rotating speed of a receiving roller to be randomly changed by using a single-needle electrostatic spinning method, wherein the orientation degree of the polyacrylonitrile/graphene composite nanofiber membrane is increased from 28.1% to 61.7% when the roller rotates at 200-1000 r/min;

(2) clamping a polyacrylonitrile/graphene composite nanofiber membrane containing zinc foil paper between two porous ceramic sheets, and pre-oxidizing in an air atmosphere at the pre-oxidation condition of 270 ℃/1.5 h; then, the polyacrylonitrile/graphene composite nanofiber membrane after the pre-oxidation treatment is placed in a graphite plate with rectangular grooves, please refer to fig. 1, where fig. 1 is a schematic structural diagram of the graphite plate with rectangular grooves in the preparation method of the ultrathin transparent carbon nanofiber membrane flexible strain sensor according to the present invention. As shown in FIG. 1, the depth of the groove is 0.2-0.5 mm, the edge of the groove is provided with a semicircular hole, the radius is 0.2-0.5 mm, and the depth is the same as that of the rectangular groove, and then the groove is covered by another graphite plate without the groove and carbonized under the argon atmosphere, and the carbonization condition is 1100 ℃/3 h. The zinc foil paper is evaporated in the carbonization process to obtain a pure ultrathin carbon nanofiber membrane without damage, and the thickness of the pure ultrathin carbon nanofiber membrane is 0.9-3.92 mu m. The grooved graphite plate has the functions of preventing the nanofiber membrane from being torn due to shrinkage stress in the carbonization process and ensuring the integrity and the flatness of the carbon nanofiber membrane; the semicircular holes on the edges of the grooves are used for keeping air circulation and facilitating the outflow of zinc vapor;

(3) shearing the pure ultrathin carbon nanofiber membrane along the orientation direction of the nanofibers or perpendicular to the orientation direction to prepare the carbon nanofiber membrane with the rectangular regular structure. The width of the carbon nanofiber membrane is 5-10 mm, and the length of the carbon nanofiber membrane is 40-70 mm;

(4) preparing a polyurethane solution with a certain mass fraction (5%). Fixing two ends of the carbon nanofiber membrane on a glass slide by using copper wires, wherein the distance between the copper wires and the near-end points of the carbon nanofiber membrane is 5-10 mm, fixing the two ends of the carbon nanofiber membrane by using a polyurethane solution with the mass fraction of 5% and less than 0.05g, connecting the carbon nanofiber membrane and the copper wires by using conductive silver adhesive, and drying at the drying temperature of 60 ℃ for 0.5h to form the electrode. The distance between the two electrodes is 30-60 mm;

(5) fixing the edge of the carbon nanofiber membrane between two electrodes on a glass slide by taking less than 0.1g of polyurethane solution with the mass fraction of 5%, and preventing the carbon nanofiber membrane from being curled and torn due to the surface tension of the solution;

(6) preparing a polyurethane solution with a certain mass fraction (5-15%), quickly spreading the polyurethane solution with a required mass on the surface of the carbon nanofiber membrane, uniformly spreading the polyurethane solution by using a silver needle, and carrying out hot air treatment at the temperature of 60 ℃ until the polyurethane solution is completely dried to form a transparent polyurethane film, wherein at the moment, the copper wire, the carbon nanofiber membrane and the transparent polyurethane film jointly form a primary sensor;

(7) and (3) standing for two days at room temperature to remove the solvent in the primary sensor and the internal stress in the polymer, peeling the primary sensor from the glass slide, and coating the carbon nanofiber membrane on the surface of the polyurethane substrate. The nanofiber membrane was then cut along its edge into an "I" configuration to form a strain sensor, wherein the sensor was cut 25mm wide and 70mm long. The thickness of the sensor is between 80 and 200 mu m. The I-shaped structure forms a strain sensor, the transparent polyurethane matrix is the I-shaped structure, for the convenience of detailed description of the structure and the size, the I-shaped structure is rotated by 90 degrees and is placed, the transparent polyurethane matrix is divided into three parts from left to right according to the structure and the size, namely a left matrix, a connecting matrix and a right matrix, the left matrix and the right matrix are connected through the connecting matrix, the left matrix and the right matrix are symmetrically arranged, the length of the connecting matrix is 10-40 mm, the difference between the length of the carbon nanofiber membrane and the length of the connecting matrix is 30mm, and the ultrathin high-light-permeability carbon nanofiber membrane flexible strain sensor has the characteristics of being stretchable (< 70%), bendable, having high sensitivity (>140) and the like.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are further described below. The invention is not limited to the embodiments listed but also comprises any other known variations within the scope of the invention as claimed.

First, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

The present invention is described in detail by using the schematic structural diagrams, etc., and for convenience of illustration, the schematic diagrams are not enlarged partially according to the general scale when describing the embodiments of the present invention, and the schematic diagrams are only examples, which should not limit the scope of the present invention. In addition, the actual fabrication process should include three-dimensional space of length, width and depth.