CN109520646B - High-sensitivity capacitive flexible touch sensor based on three-dimensional porous microstructure composite dielectric layer and manufacturing method thereof - Google Patents
High-sensitivity capacitive flexible touch sensor based on three-dimensional porous microstructure composite dielectric layer and manufacturing method thereof Download PDFInfo
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- CN109520646B CN109520646B CN201811422229.9A CN201811422229A CN109520646B CN 109520646 B CN109520646 B CN 109520646B CN 201811422229 A CN201811422229 A CN 201811422229A CN 109520646 B CN109520646 B CN 109520646B
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Abstract
The invention discloses a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer and a preparation method thereof. The capacitive flexible touch sensor has good flexibility, detection sensitivity and dynamic response characteristics, and provides an idea for designing a high-sensitivity flexible touch sensor for intelligent robot electronic skin application.
Description
Technical Field
The invention belongs to the field of flexible touch sensors, and particularly relates to a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer and a preparation method thereof, which are used for realizing touch perception of electronic skin.
Background
Electronic skin (e-skin) is one of the leading directions of intelligent material and sensor research, is also a new field of the development of the modern electronic information industry, and has important application value in the fields of artificial intelligence, communication entertainment, medical health and the like. The flexible touch sensor is an important component in electronic skin research, is an important way for a robot to sense external environment information second to vision, is one of necessary media for the robot to realize direct interaction with the external environment or a target object, and has important scientific significance and application value for exploring the physical world of an intelligent robot in the future.
With the development of scientific technology and the continuous improvement of production and preparation processes, higher requirements are put forward on the aspects of functional structures, appearance characteristics and the like of the robot touch sensor, and the flexible touch sensor with the characteristics of flexibility, wearing comfort, high sensitivity, high stability, large-area touch perception and the like becomes a research hotspot of electronic skins. The traditional silicon-based and metal strain gauge type robot touch sensor has certain defects in the aspects of flexibility, ductility, wearing comfort and the like, and the force-sensitive conductive composite material prepared by filling the nano conductive material in the flexible substrate is widely applied to the design of the flexible touch sensor. The carbon material, especially the carbon nano tube and the graphene can be assembled into various macroscopic structures, including one-dimensional fibers, two-dimensional films and three-dimensional block structures, has excellent electrical, mechanical and thermal properties and good flexibility and stability, endows the flexible sensor with high sensitivity and excellent stability, and plays an important role in the research of the flexible touch sensor by preparing the force-sensitive composite conductive material based on the carbon nano material.
Flexible tactile sensors can be broadly classified into photoelectric, piezoelectric, resistive, capacitive, etc. types according to their operating principles. The capacitive flexible touch sensor has the advantages of high sensitivity, high precision, high response speed, small hysteresis, easiness in integration and the like, and is widely applied to the research of electronic skins of intelligent robots. The sensitivity of a traditional flexible touch sensor based on a composite material in a low-pressure area is low, in order to improve the sensing performance of the flexible touch sensor, domestic and foreign researchers continuously try to design sensitive material systems and sensitive unit structures, and a common method for improving the electronic skin touch detection sensitivity of a robot is to arrange a microstructure on a touch sensitive layer. The common microstructures mainly comprise pyramids, whisker-shaped structures, concave-convex structures, microneedle structures and the like, and generally, when the microstructures are designed on the sensitive layer, complicated process flows such as photoetching, sputtering, evaporation, etching and the like are often needed in the preparation process of the microstructures, and the defects that the mass production is not easy exist and the like are overcome.
In recent years, the three-dimensional porous microstructure composite conductive material becomes a machine by using unique electrical properties and mechanical properties thereofIn the research hotspot of human flexible electronic skin, the common preparation method of the three-dimensional porous microstructure composite conductive material comprises the following steps: vacuum freeze drying, chemical vapor deposition, impregnation coating, etc. The principle of the vacuum freeze-drying method, also called sublimation drying, is that a wet material or solution is frozen into a solid state at a lower temperature (-50 ℃ to-10 ℃), and then the moisture in the wet material or solution is directly sublimated into a gas state without a liquid state under vacuum (1.3 to 12Pa) so as to achieve the purpose of drying. Shu Wan et al utilize a freeze vacuum drying method to prepare graphene oxide foam, and based on the characteristics of excellent elasticity, high relative dielectric constant and the like of the graphene oxide foam, high-performance composite dielectric layers and flexible electrodes are respectively prepared by taking the graphene oxide foam and graphene as base materials, and an ultra-sensitive capacitive flexible touch sensor is designed, so that high detection sensitivity (about 0.8 kPa) can be realized-1) Low detection limit (-0.24 Pa), fast response (-100 ms), and the like. However, the vacuum freeze-drying method has the disadvantages of expensive equipment, energy consumption, high material preparation cost and the like. Chemical Vapor Deposition (CVD) usually uses a three-dimensional foamed nickel material as a template, and performs chemical vapor deposition on conductive materials such as graphene on a three-dimensional framework, and then removes the foamed nickel framework through chemical etching to obtain the graphene conductive foam with the three-dimensional porous microstructure. The yellow-vitamin group of advanced materials research institute of Nanjing university of Industrial university prepares the three-dimensional porous conductive material by chemical vapor deposition, is applied to the flexible stretchable touch sensor, and can realize high sensitivity (strain coefficient GF is 35), quick response (about 30ms) and good stability (cycle number)>5000) And (4) a tactile perception function. However, chemical vapor deposition generally has the requirements of low deposition rate, easy pollution to the surface of the film and the environment in the deposition process, and corrosion resistance to equipment. Compared with a vacuum freeze-drying method and a chemical vapor deposition method, the three-dimensional porous microstructure composite conductive material is directly formed on the surface of the three-dimensional skeleton structure in a self-assembly mode of a dipping wrapping method, so that the preparation cost is reduced, the process flow is simplified, and the method has the advantages of simplicity in preparation, contribution to macro-preparation and the like.
The composite dielectric layer of the capacitive touch sensor is designed based on the excellent mechanical properties and electrical properties of the three-dimensional porous microstructure conductive composite material, the high-sensitivity capacitive flexible touch sensor is widely concerned by researchers at home and abroad, and the high-sensitivity capacitive flexible touch sensor has important application value in the fields of human physiological parameter monitoring, human-computer interaction, soft robots and the like.
Disclosure of Invention
In order to improve the touch perception sensitivity of electronic skin, the invention takes a polyurethane sponge three-dimensional framework as a template, adopts a self-assembly method, prepares a three-dimensional conductive network by impregnating and wrapping a graphene/multi-walled carbon nanotube/silicone rubber composite conductive material on the surface of the polyurethane sponge three-dimensional framework layer by layer, and is used as a three-dimensional porous microstructure composite dielectric layer.
The invention solves the technical problem and adopts the following technical scheme:
the invention relates to a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer, which is characterized in that: the capacitive flexible touch sensor can be equivalent to a parallel plate capacitor with the synergistic effect of the polar plate distance and the effective dielectric constant, and a flexible isolation layer, a flexible polar plate and a flexible protection layer are sequentially arranged on the upper surface and the lower surface of a three-dimensional porous microstructure composite dielectric layer;
the three-dimensional porous microstructure composite dielectric layer is obtained by self-assembling a polyurethane sponge serving as a template and a graphene/multi-walled carbon nanotube/silicone rubber composite conductive material serving as a force-sensitive composite material, wherein the graphene/multi-walled carbon nanotube/silicone rubber conductive composite material is impregnated and wrapped on the surface of a three-dimensional framework of the polyurethane sponge layer by layer.
The force-sensitive composite material is prepared by using two-dimensional graphene and a one-dimensional multi-walled carbon nanotube as two-phase conductive materials, dispersing the two-dimensional graphene and the one-dimensional multi-walled carbon nanotube in a silicon rubber matrix, and improving the uniform dispersibility of a conductive phase in the matrix and the stability of an electrical network of the force-sensitive composite material by utilizing the synergistic effect between the two-phase conductive materials. The mass ratio of the two-dimensional graphene to the one-dimensional multi-walled carbon nanotube to the silicone rubber is 1: 2-3: 20-30, and preferably 1:2.5: 20.
The flexible isolation layer and the flexible protection layer are made of PDMS, and the flexible polar plate is made of organic silicon conductive silver adhesive.
The high-sensitivity capacitive flexible touch sensor is based on the synergistic effect of the distance between the polar plates and the effective dielectric constant: under the action of a touch force, the three-dimensional porous microstructure composite dielectric layer is compressed, so that on one hand, the distance between an upper polar plate and a lower polar plate of the capacitive flexible touch sensor is reduced, and on the other hand, the electrical characteristics of the three-dimensional porous microstructure composite dielectric layer are changed, so that the effective dielectric constant of the composite dielectric layer is changed. The synergy between the plate spacing and the effective dielectric constant improves the sensitivity of the capacitive flexible touch sensor.
The composite conductive material is prepared by filling the silicone rubber with the graphene and multi-walled carbon nanotube two-phase conductive filler, the specific surface area of the graphene is far larger than that of the carbon nanotubes, and when the graphene/the carbon nanotubes are dispersed in the silicone rubber matrix, the contact probability of the carbon nanotube-graphene sheet layer is higher than that of the carbon nanotube-carbon nanotube, so that the agglomeration effect between the carbon nanotubes is weakened. In addition, the carbon nanotubes which can serve as bridges are distributed around the graphene sheet layers, gaps among the graphene sheet layers which are far away can be communicated, meanwhile, the graphene sheet layers are not easy to be stacked again, the graphene and the carbon nanotubes play a role in blocking each other, and finally, the carbon nanotubes are well dispersed in the silicon rubber matrix. The synergistic effect between the one-dimensional conductive phase and the two-dimensional conductive phase is beneficial to not only the uniform dispersion of the conductive phase in the matrix, but also the improvement of the stability of the electrical network of the force-sensitive composite conductive material.
The invention relates to a method for manufacturing a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer, which comprises the following steps of:
11. Preparation of graphene/multi-walled carbon nanotube suspension
Dispersing graphene and multi-walled carbon nanotubes in organic solvent naphtha, performing ultrasonic dispersion for 1h, and then performing magnetic stirring for 1h to obtain a uniformly dispersed graphene/multi-walled carbon nanotube suspension;
12. preparation of graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution
Adding silicon rubber into the graphene/multi-walled carbon nanotube suspension, ultrasonically dispersing for 1h, and magnetically stirring for 1h to obtain a uniformly dispersed graphene/multi-walled carbon nanotube/silicon rubber composite conductive solution;
13. preparation of three-dimensional porous microstructure composite dielectric layer
Firstly, washing polyurethane sponge by deionized water, placing the polyurethane sponge in a centrifuge to remove excessive water, setting the rotating speed to be 1000rpm, repeating for multiple times to remove impurities on the surface of the polyurethane sponge, naturally airing and cutting the polyurethane sponge into required sizes;
then, carrying out impregnation-centrifugation-curing treatment on the pretreated polyurethane sponge: immersing the pretreated polyurethane sponge into the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution and extruding for multiple times to ensure that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution is fully contacted with the surface of the three-dimensional skeleton of the polyurethane sponge; placing the polyurethane sponge soaked in the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution on a centrifuge for centrifugation at a rotating speed of 600rpm to remove the redundant graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution; then placing the polyurethane sponge in a vacuum drying oven at 60 ℃ for curing;
repeatedly carrying out multiple dipping-centrifuging-curing treatments, so that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material is attached to the surface of the three-dimensional skeleton of the polyurethane sponge through a layer-by-layer dipping and wrapping process to obtain a three-dimensional porous microstructure composite dielectric layer;
And respectively and sequentially spin-coating a flexible isolation layer, a flexible polar plate and a flexible protective layer on the upper surface and the lower surface of the three-dimensional porous microstructure composite dielectric layer, wherein the thicknesses of the flexible isolation layer, the flexible polar plate and the flexible protective layer are all 50 micrometers, and leading out a flexible electrode on the flexible polar plate to obtain the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure.
Preferably, in the step 1, the mass-to-volume ratio of the graphene to the multi-walled carbon nanotube to the silicone rubber to the naphtha is 1g: 2-3 g: 20-30 g: 500-800 mL.
In the method, the electrical property and the mechanical property of the three-dimensional porous microstructure composite dielectric layer can be regulated and controlled by changing the process parameters such as the dipping and wrapping times, the conductive phase content, the concentration of the composite conductive solution and the like, so that the requirement of electronic skin on touch perception under different application scenes can be met.
The impregnation wrapping method of the invention adopts the three-dimensional porous material polyurethane sponge as the template, and prepares the three-dimensional porous microstructure composite conductive material by impregnating and wrapping the composite conductive material on the surface of the three-dimensional framework layer by layer, and has the characteristics of simple process, easy regulation and control of mechanical property and electrical property, and the like. The method can realize the macro preparation of the three-dimensional porous microstructure conductive composite material, the three-dimensional porous microstructure conductive composite material has the unique mechanical characteristics of a polyurethane three-dimensional network structure and the excellent electrical and mechanical properties of the conductive composite material, and the application of the conductive composite material in the fields of flexible electronic devices, soft robots, electromagnetic shielding, energy storage materials and the like is expanded.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the high-sensitivity capacitive flexible touch sensor, the three-dimensional porous microstructure conductive composite material is used as the elastic composite dielectric layer, and the detection sensitivity of the flexible touch sensor is improved by utilizing the synergistic effect between the distance between the upper and lower polar plates and the effective dielectric constant change of the composite dielectric layer when the flexible touch sensor is stressed. Meanwhile, based on the excellent mechanical property and electrical property of the three-dimensional porous microstructure composite dielectric layer, the repeatability and dynamic response characteristic of the capacitive flexible touch sensor are improved.
2. According to the high-sensitivity capacitive flexible touch sensor, the layer-by-layer impregnation and wrapping process is utilized, the graphene/multi-walled carbon nanotube/silicone rubber conductive composite material is impregnated and wrapped on the surface of the polyurethane sponge three-dimensional framework layer by layer to prepare the capacitive flexible touch sensor composite dielectric layer, and the electrical property and the mechanical property of the three-dimensional porous microstructure composite dielectric layer can be regulated and controlled by changing the process parameters such as the impregnation and wrapping times, the conductive phase content, the composite conductive solution concentration and the like, so that the flexible regulation and control of the performance of the capacitive flexible touch sensor are realized, and the touch sensing requirements under different application scenes are met.
3. According to the high-sensitivity capacitive flexible touch sensor, the three-dimensional skeleton structure of the polyurethane sponge is used as the template, and compared with three-dimensional conductive network preparation methods such as a vacuum freeze drying method and a chemical vapor deposition method, the three-dimensional porous microstructure composite conductive material is directly formed on the surface of the three-dimensional skeleton structure in a self-assembly mode of layer-by-layer impregnation and wrapping, so that the preparation cost is reduced, the process flow is simplified, and the high-sensitivity capacitive flexible touch sensor has the advantages of simplicity in preparation method, contribution to macro preparation and the like.
4. The high-sensitivity capacitive flexible touch sensor disclosed by the invention takes commercial polyurethane sponge as a base material and carbon-based material as a conductive phase, the price of the used raw materials is low, and meanwhile, the requirements of electronic skin on flexibility, wearing comfort and large-area touch perception are easily met.
Drawings
Fig. 1 is a schematic structural diagram of a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer, wherein the reference numbers in the diagram are as follows: the composite material comprises a flexible protective layer 1, a flexible polar plate 2, a flexible isolating layer 3 and a three-dimensional porous microstructure composite medium layer 4.
FIG. 2 is a schematic diagram of a split structure of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer.
FIG. 3 is a schematic diagram of the working principle of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer.
FIG. 4 is a flow chart of the preparation of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer.
FIG. 5 is a scanning electron microscope image of the three-dimensional porous microstructure composite dielectric layer in the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer according to the invention.
FIG. 6 shows the relative capacitance change of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer under different pressures.
FIG. 7 shows the step response characteristic of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer.
FIG. 8 shows the repetitive characteristics of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer according to the present invention.
FIG. 9 shows the change rule of the electrical characteristics of the three-dimensional porous microstructure composite dielectric layer in the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer under different dipping wrapping times and dipping concentrations.
FIG. 10 is a schematic array structure diagram of a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer according to the present invention.
Detailed Description
The following embodiments of the present invention will be described in detail with reference to the accompanying drawings, which are provided for implementing the technical solution of the present invention, and provide detailed embodiments and specific procedures, but the scope of the present invention is not limited to the following embodiments.
Example 1
As shown in fig. 1, in the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer of the embodiment, the structure of the high-sensitivity capacitive flexible touch sensor can be equivalent to a parallel plate capacitor with a synergistic effect of a plate spacing and an effective dielectric constant, a flexible isolation layer 3, a flexible plate 2 and a flexible protection layer 1 are sequentially arranged on the upper surface and the lower surface of a three-dimensional porous microstructure composite dielectric layer 4, and a schematic diagram of a splitting structure of the high-sensitivity capacitive flexible touch sensor is shown in fig. Wherein: the flexible isolation layer 3 and the flexible protection layer 1 are made of PDMS, and the flexible polar plate 2 is made of organic silicon conductive silver adhesive; the three-dimensional porous microstructure composite dielectric layer 4 is obtained by taking polyurethane sponge as a template and taking graphene/multi-walled carbon nanotube/silicone rubber conductive composite material as a force-sensitive composite material, impregnating and wrapping the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material on the surface of a three-dimensional skeleton of the polyurethane sponge layer by layer and performing self-assembly.
The working principle schematic diagram of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer is shown in fig. 3, and the structure of the high-sensitivity capacitive flexible touch sensor can be equivalent to a parallel plate capacitor. As shown in fig. 3(a), under the action of a tactile force, the three-dimensional porous microstructure composite dielectric layer of the capacitive flexible tactile sensor is compressed under the action of the tactile force: on one hand, the parallel plate capacitor plate spacing is reduced; on the other hand, the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material wrapped on the surface of the polyurethane sponge three-dimensional framework has the advantages that as the distance between conductive phases is reduced, the conductive contact probability is increased, the number of effective conductive paths is increased, or the composite conductive material is in interface contact, a new three-dimensional conductive network is formed, so that the electrical characteristics of the three-dimensional porous composite dielectric layer are changed, and the effective dielectric constant is changed accordingly. Fig. 3(b) is a stress-strain simulation result of a single three-dimensional porous microstructure based on ANSYS finite element simulation software, and it can be seen that, under the action of a tactile force, the three-dimensional skeleton structure deforms, and the stress at the skeleton joint is the largest, so that the effective conductive path of the force-sensitive composite conductive material wrapped on the skeleton surface changes.
The preparation process of the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure composite dielectric layer in the embodiment is shown in fig. 4, and the specific steps are as follows:
11. Preparation of graphene/multi-walled carbon nanotube suspension
Weighing 0.10g of graphene and 0.25g of multi-walled carbon nanotube, dispersing a conductive filler in 50mL of organic solvent naphtha, and performing ultrasonic dispersion for 1h and magnetic stirring for 1h in sequence to obtain a uniformly dispersed graphene/multi-walled carbon nanotube suspension.
12. Preparation of graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution
Adding 2g of silicon rubber into the graphene/multi-walled carbon nanotube suspension, and performing ultrasonic dispersion for 1 hour and magnetic stirring for 1 hour to obtain the graphene/multi-walled carbon nanotube/silicon rubber composite conductive solution which is uniformly dispersed.
13. Preparation of three-dimensional porous microstructure composite conductive material
Firstly, washing polyurethane sponge by deionized water, placing the polyurethane sponge in a centrifuge to remove excessive water, setting the rotating speed to be 1000rpm, repeating for 6 times to remove impurities on the surface of the polyurethane sponge, naturally airing and cutting the polyurethane sponge into required size;
then, carrying out impregnation-centrifugation-curing treatment on the pretreated polyurethane sponge: immersing the pretreated polyurethane sponge into the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution and extruding for multiple times to ensure that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution is fully contacted with the surface of the three-dimensional skeleton of the polyurethane sponge; placing the polyurethane sponge soaked in the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution on a centrifuge for centrifugation at a rotating speed of 600rpm to remove the redundant graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution; then placing the polyurethane sponge in a vacuum drying oven at 60 ℃ for curing;
carrying out impregnation-centrifugation-curing treatment for 6 times repeatedly, so that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material is attached to the surface of the three-dimensional skeleton of the polyurethane sponge through a layer-by-layer impregnation wrapping process to obtain a three-dimensional porous microstructure composite dielectric layer;
And respectively and sequentially spin-coating a flexible isolation layer, a flexible polar plate and a flexible protective layer on the upper surface and the lower surface of the three-dimensional porous microstructure composite dielectric layer, wherein the thicknesses of the flexible isolation layer, the flexible polar plate and the flexible protective layer are all 50 micrometers, and leading out a flexible electrode on the flexible polar plate to obtain the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure.
Fig. 5 is a scanning electron microscope image of the three-dimensional porous microstructure composite dielectric layer manufactured in this embodiment. FIG. 5(a) is a scanning electron microscope image of a three-dimensional skeleton of a pretreated polyurethane sponge; fig. 5(b) is a scanning electron microscope image of the polyurethane sponge three-dimensional skeleton coated with the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material, and it can be seen that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material is uniformly coated on the surface of the polyurethane sponge three-dimensional skeleton; fig. 5(c) is a scanning electron microscope image of the graphene/multiwall carbon nanotube/silicone rubber composite conductive material, and it can be seen that the graphene/multiwall carbon nanotube conductive phases are uniformly dispersed in the silicone rubber matrix, and the stability of the electrical network of the composite conductive material is improved by the synergistic conductive effect between the one-dimensional conductive phase and the two-dimensional conductive phase.
To characterize the high sensitivity of the capacitive flexible touch sensor obtained in this example, the output of the capacitive flexible touch sensor under different pressures is measured and plotted against the change in capacitance as shown in FIG. 6, and the sensitivity of the capacitive flexible touch sensor is 3.42kPa in the ranges of 0 to 1kPa and 1 to 8kPa, respectively-1And 0.66kPa-1Meanwhile, the input and output characteristics of the pressure sensor are good in linearity in the ranges of 0-1kPa and 1-8 kPa.
The polyurethane sponge has good resilience, is used as a template of a three-dimensional porous microstructure composite dielectric layer, has an important significance for improving the dynamic characteristic of the capacitive flexible touch sensor, and is used for further measuring the dynamic response time of the capacitive flexible touch sensor, the capacitive flexible touch sensor obtained in the embodiment is subjected to stage excitation, the response characteristic curve of the capacitive flexible touch sensor is shown in fig. 7, and the response time is about 38 ms. The capacitance type flexible touch sensor obtained in the embodiment is subjected to cyclic loading and unloading, the stability and the repeatability are observed, the test result is shown in fig. 8, and after about 2200s loading and unloading experiments, the capacitance type flexible touch sensor can still stably output, so that good stability is maintained.
Fig. 9 shows the electrical property change rule of the three-dimensional porous microstructure composite dielectric layer under different Dipping times (Dipping times) and solution concentrations, and it can be seen that when the concentration of the conductive composite solution is fixed, the resistance of the three-dimensional porous microstructure composite dielectric layer gradually becomes stable along with the increase of the Dipping times; under the same dipping times, when the polyurethane sponge is dipped and wrapped by different conductive composite solution concentrations, the resistance of the three-dimensional porous microstructure composite dielectric layer is different and tends to be stable along with the increase of the dipping times. Therefore, the electrical property and the mechanical property of the three-dimensional porous microstructure composite dielectric layer can be regulated and controlled by changing the process parameters such as the dipping and wrapping times, the conductive phase content, the concentration of the composite conductive solution and the like, so that the requirement of electronic skin on touch perception under different application scenes can be met.
In general, in order to realize the electronic skin large-area tactile perception function, an array design of the flexible tactile sensor is often required. The row and column structure is a method commonly adopted by the array design of the touch sensor, in order to realize large-area touch sensing and give consideration to the characteristics of electronic skin wearability, splicing and the like, the array design of the capacitive flexible touch sensor obtained in the embodiment is carried out, the schematic diagram of the array structure is shown in figure 10, a 10 multiplied by 10 capacitive flexible touch sensing array is designed on a flexible substrate, electrodes in each row and each column are led to the edge of the flexible substrate so as to be convenient for testing and array expansion, and the array touch sensing is realized by scanning each touch sensing unit in the capacitive flexible touch sensing array one by one.
The present invention is not limited to the above exemplary embodiments, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A manufacturing method of a high-sensitivity capacitive flexible touch sensor based on a three-dimensional porous microstructure composite dielectric layer is characterized by comprising the following steps of:
the capacitive flexible touch sensor can be equivalent to a parallel plate capacitor with the synergistic effect of the polar plate distance and the effective dielectric constant, and is characterized in that a flexible isolation layer, a flexible polar plate and a flexible protection layer are sequentially arranged on the upper surface and the lower surface of a three-dimensional porous microstructure composite dielectric layer; the three-dimensional porous microstructure composite dielectric layer is obtained by self-assembling a polyurethane sponge serving as a template and a graphene/multi-walled carbon nanotube/silicone rubber conductive composite material serving as a force-sensitive composite material, wherein the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material is impregnated and wrapped on the surface of a three-dimensional framework of the polyurethane sponge layer by layer; the force-sensitive composite material is dispersed in a silicon rubber matrix by using two-dimensional graphene and a one-dimensional multi-walled carbon nanotube two-phase conductive material together, and the uniform dispersibility of a conductive phase in the matrix and the stability of an electrical network of the force-sensitive composite material are improved by utilizing the synergistic effect between the two-phase conductive material; the mass ratio of the two-dimensional graphene to the one-dimensional multi-walled carbon nanotube to the silicone rubber is 1: 2-3: 20-30; the electrical property and the mechanical property of the three-dimensional porous microstructure composite dielectric layer can be regulated and controlled by changing the dipping and wrapping times, the conductive phase content and the concentration of the composite conductive solution, so that the flexible regulation and control of the performance of the capacitive flexible touch sensor are realized, and the touch sensing requirements under different application scenes are met;
the manufacturing method of the high-sensitivity capacitive flexible touch sensor comprises the following steps:
step 1, preparing a three-dimensional porous microstructure composite dielectric layer
11. Preparation of graphene/multi-walled carbon nanotube suspension
Dispersing graphene and multi-walled carbon nanotubes in organic solvent naphtha, performing ultrasonic dispersion for 1h, and then performing magnetic stirring for 1h to obtain a uniformly dispersed graphene/multi-walled carbon nanotube suspension;
12. preparation of graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution
Adding silicon rubber into the graphene/multi-walled carbon nanotube suspension, ultrasonically dispersing for 1h, and magnetically stirring for 1h to obtain a uniformly dispersed graphene/multi-walled carbon nanotube/silicon rubber composite conductive solution;
13. preparation of three-dimensional porous microstructure composite dielectric layer
Firstly, washing polyurethane sponge by deionized water, placing the polyurethane sponge in a centrifuge to remove excessive water, setting the rotating speed to be 1000rpm, repeating for multiple times to remove impurities on the surface of the polyurethane sponge, naturally airing and cutting the polyurethane sponge into required sizes;
then, carrying out impregnation-centrifugation-curing treatment on the pretreated polyurethane sponge: immersing the pretreated polyurethane sponge into the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution and extruding for multiple times to ensure that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution is fully contacted with the surface of the three-dimensional skeleton of the polyurethane sponge; placing the polyurethane sponge soaked in the graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution on a centrifuge for centrifugation at a rotating speed of 600rpm to remove the redundant graphene/multi-walled carbon nanotube/silicone rubber composite conductive solution; then placing the polyurethane sponge in a vacuum drying oven at 60 ℃ for curing;
repeatedly carrying out multiple dipping-centrifuging-curing treatments, so that the graphene/multi-walled carbon nanotube/silicone rubber composite conductive material is attached to the surface of the three-dimensional skeleton of the polyurethane sponge through a layer-by-layer dipping and wrapping process to obtain a three-dimensional porous microstructure composite dielectric layer;
step 2, high-sensitivity capacitive flexible touch sensor
And respectively and sequentially spin-coating a flexible isolation layer, a flexible polar plate and a flexible protective layer on the upper surface and the lower surface of the three-dimensional porous microstructure composite dielectric layer, wherein the thicknesses of the flexible isolation layer, the flexible polar plate and the flexible protective layer are all 50 micrometers, and leading out a flexible electrode on the flexible polar plate to obtain the high-sensitivity capacitive flexible touch sensor based on the three-dimensional porous microstructure.
2. The method of manufacturing according to claim 1, wherein: the flexible isolation layer and the flexible protection layer are made of PDMS, and the flexible polar plate is made of organic silicon conductive silver adhesive.
3. The method of manufacturing according to claim 1, wherein: in the step 1, the mass-to-volume ratio of the graphene to the multi-walled carbon nanotube to the silicone rubber to the naphtha is 1g: 2-3 g: 20-30 g: 500-800 mL.
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