CN114941980A - Micro-crack strain sensor and preparation method thereof - Google Patents
Micro-crack strain sensor and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a micro-crack strain sensor and a preparation method thereof. The micro-crack strain sensor comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, and an electrode is introduced to achieve electrical signal output. The prepared brittle conductive film is coated on a flexible substrate layer and is pre-bent or stretched to form micro-cracks. The micro-crack strain sensor is based on the strong interaction between the brittle conductive film crack layer and the flexible substrate layer, the brittle conductive film crack layer is divided into a transition layer close to the flexible substrate layer and a body layer far away from the flexible substrate layer, under the various strain effects of stretching, bending, contact pressure and the like, the transition layer and the body layer present different crack expansion forms, the large change (>50000 times) of the resistance value can be realized under the small strain (< 20%), and the micro-crack strain sensor has extremely excellent strain sensing performance. This method of constructing a microcracked strain sensor is known as the Chen-Gong model.
Description
Technical Field
The invention belongs to the field of flexible electronic devices, particularly relates to a micro-crack strain sensor and a preparation method thereof, and particularly relates to a micro-crack strain sensor based on a flexible substrate layer and a brittle conducting layer and a preparation method thereof.
Background
In the fields of wearable intelligent equipment, implantable electronic devices and intelligent robots, flexible strain sensors are one of the most important devices; it can convert the strain into an electrical signal and further into a digital signal for output. Compared with the traditional hard sensor prepared from metal or semiconductor, the flexible strain sensor can be transformed into any shape and attached to any position on the surface of the skin or the surface of the intelligent robot, so that the flexible strain sensor is wider in application environment. In addition, the strain response range and GF value (the rate of change of resistance per unit strain, which is one of the criteria for evaluating strain sensing performance) of the flexible strain sensor are superior to those of the conventional rigid strain sensor, and therefore, no discussion has been given about the flexible strain sensor in recent years. Among them, the most common method for preparing flexible strain sensors is to blend a flexible polymer matrix and conductive fillers uniformly, and the conductive fillers form a conductive path in the flexible polymer matrix. When the composite material is strained, the conductive path is broken, and the resistance of the composite material rises sharply, so that the composite material has better strain sensing performance. However, flexible strain sensors prepared in this way typically require higher GF values (5-500) at higher strains (> 100%).
Patent CN 113930037 a modifies nano metal/graphene, and amino groups are grafted on the surface of the nano metal/graphene, and the amino groups and carboxyl groups in the matrix-modified polyvinyl alcohol undergo a condensation reaction. The method improves the dispersion degree of nano metal/graphene in the modified polyvinyl alcohol matrix, and the uniformly dispersed conductive filler network is easier to be damaged in strain, so that the composite material has good strain sensing performance (the GF value is about 7 under 80% strain). Meanwhile, the chemical bonding between the conductive filler and the polymer matrix enables the composite material to have good stability and fatigue resistance in the cyclic stretching process. However, in practice it is often necessary for the strain sensors to produce a sufficiently large signal for finer strains, which is not possible with strain sensors of the conductive composite type.
In recent years, scientists design a strain sensor with a micro-crack structure, namely a layer of nano-scale metal film is sputtered or sprayed on the surface of a flexible base layer, and the surface of the metal film forms uniform micro-cracks in a bending or stretching mode. During the stretching process, the metal film microcracks are expanded to reduce the thickness of the metal film at the cracks, so that the resistance of the strain sensor is increased sharply. The GF value can be as high as (2000-80000) under extremely low strain (< 5%). Patent CN 113310395 a places a plating template with a corresponding hollowed-out shape on a substrate layer, and deposits two metals in the template. And coating a protective layer on the part where the metal is not deposited by using a template. The microcrack strain sensor prepared in the mode has cracks with higher precision, and the service life of the cracks in the strain process is not influenced. However, the existing micro-crack strain sensor has an essential defect that the micro-crack structure is irreversibly damaged under a large strain, so that the application to a complicated practical application environment is difficult.
Disclosure of Invention
Therefore, an object of the present invention is to provide a novel micro-crack strain sensor with better strain sensing performance at lower strain and good environmental adaptability, which solves the problems of the prior art.
The invention is realized by the following technical scheme:
a micro-crack strain sensor comprises a flexible substrate layer, a brittle conductive thin film crack layer and a flexible packaging layer; the raw material formula comprises the following components in parts by weight: 50-90 parts of a flexible substrate material; 0-5 parts of an elastomer crosslinking agent; 0-10 parts of an elastomer crosslinking assistant; 1-5 parts of a brittle film material; 0.01-0.5 part of conductive filler; 0-3 parts of an interface modifier; the flexible substrate material is one or more of a thermosetting elastomer, a thermoplastic elastomer and a flexible film; the brittle film material is one or more of carboxymethyl chitosan, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, ethylene-vinyl acetate copolymer, cellulose acetate, ethyl cellulose, polyacrylamide, polymethyl methacrylate, polyvinyl chloride and polycarbonate; the conductive filler is one or more of carbon nano tube, graphene, conductive carbon black, nano silver wire, poly (3, 4-ethylenedioxythiophene), polyacetylene and polyaniline.
Further preferably, the thermosetting elastomer is one or more of natural rubber, natural rubber latex, epoxidized natural rubber latex, ethylene propylene rubber, silicone rubber, fluororubber, nitrile rubber latex, carboxylated nitrile rubber latex, styrene-butadiene rubber latex, carboxylated styrene-butadiene rubber latex, eucommia ulmoides latex and dandelion latex, and the thermoplastic elastomer is one or more of styrene-butadiene block copolymer, ethylene-octene copolymer, polyurethane elastomer and polyamide elastomer.
Further preferably, the flexible film material is one or more of polyimide, polyester, cyclic olefin polymer and liquid crystal polymer.
Further preferably, the elastomer crosslinking agent is one or more of a sulfur vulcanizing agent, a peroxide vulcanizing agent, a hydrosilylation crosslinking agent, an amine vulcanizing agent, and a bisphenol vulcanizing agent.
More preferably, the elastomer crosslinking assistant is one or more of zinc oxide, thiazole accelerators, sulfenamide accelerators, thiuram accelerators, thiocarbamate accelerators, guanidine accelerators, bisphenol accelerators, quaternary ammonium salt accelerators, quaternary phosphonium salt accelerators, cyanurate accelerators and transition metal coordination accelerators.
Further preferably, the carbon nanotubes are one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes; the conductive carbon black is one or more of oil furnace conductive carbon black, heavy oil reproduced conductive carbon black and calcium carbide acetylene conductive carbon black.
Further preferably, the interface modifier is one or more of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, an aluminum-titanium composite coupling agent, an anionic surfactant, a cationic surfactant and a nonionic surfactant.
The invention also provides a preparation method of the micro-crack strain sensor, which comprises the following steps:
a) obtaining a flexible substrate layer, wherein the flexible substrate layer is a flexible film or an elastomer film or a flexible film-elastomer film composite flexible substrate layer; the preparation method of the elastomer film comprises the following steps: and sequentially adding an elastomer crosslinking agent, or the elastomer crosslinking agent and an elastomer crosslinking assistant, or the elastomer crosslinking agent, the elastomer crosslinking assistant and an interface modifier into the thermosetting elastomer latex or the thermosetting elastomer solution or the thermoplastic elastomer solution, uniformly mixing, and molding to obtain the elastomer film.
b) The preparation method of the brittle conductive film crack layer comprises the following steps:
i) and dissolving the brittle film material in a solvent to obtain a solution of the brittle film material.
ii) dispersing the conductive filler or the conductive filler and the interface modifier in the solution of the brittle film material under the ultrasonic action to obtain the conductive filler-brittle film material suspension.
And iii) coating the conductive filler-brittle film material suspension obtained in the step ii) on the surface of the flexible substrate layer in multiple times, and heating and drying to form a brittle conductive film layer on the surface of the flexible substrate layer.
iv) adopting a pre-bending or stretching mode to enable the brittle conductive film layer prepared in the step iii) to form uniform cracks, and obtaining the brittle conductive film crack layer.
c) And repeating the step a) to obtain a flexible substrate layer, covering the flexible substrate layer on the surface of the conductive film crack layer to be used as a flexible packaging layer to seal the conductive film crack layer, and obtaining the micro-crack strain sensor.
Further preferably, the flexible substrate layer is subjected to surface treatment between the step a) and the step b), and the surface treatment method is one or more of electroplating, chemical plating, electrophoresis, chemical heat treatment, ozone, plasma and laser surface treatment. And step iv) further comprises leading the conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode, and step c) further comprises leading the output electrode out of the flexible packaging layer.
Further preferably, the ultrasonic action time in the step ii) is 0.1-2 hours, and the ultrasonic action power is 100-10000W; the bending curvature radius of the step iv) is 1-5 mm, and the stretching speed is 50-2000 cm/min.
Further preferably, the above prepared micro-crack strain sensor is most sensitive to in-plane strain caused by tension or compression. For the strain which is perpendicular to the microcrack strain sensor or inclined at a certain angle such as pressing, the manufacturing method of the microcrack strain sensor can also add the step d): fixing two ends of the micro-crack strain sensor prepared in the step c), and suspending the middle of the micro-crack strain sensor to obtain the arc-shaped micro-crack strain sensor with an arc structure, wherein the structure can convert the strain of the micro-crack strain sensor in the vertical or certain-angle inclined direction into the strain in the horizontal plane, so that the arc-shaped micro-crack strain sensor has high sensitivity to the strain in the vertical or certain-angle inclined direction.
Has the advantages that:
according to the micro-crack strain sensor based on the flexible substrate layer and the brittle conducting layer, the GF value can reach more than 400000 at most. And the strain response range of the micro-crack strain sensor can be adjusted (the minimum response strain is lowered to 1%, and the maximum response strain is raised to 100%) so as to adapt to different application scenarios.
The micro-crack strain sensor based on the flexible substrate layer and the brittle conducting layer can still keep better strain sensing performance after being subjected to large strain or cyclic strain, and has good stability.
The flexible substrate layer-brittle conducting layer-based micro-crack strain sensor is simple in preparation process and convenient for large-scale production. And the prepared microcrack strain sensor has small volume and light weight, and is suitable for wearable intelligent equipment.
The flexible substrate layer-brittle conducting layer-based micro-crack strain sensor has extremely high GF value and adjustable strain response range. Even under very low voltage, still can output very big current change signal (when operating voltage is 1.5V, can detect the obvious change of electric current), consequently be applicable to the low pressure environment, improved strain sensor's security, reduced strain sensor's energy consumption. The method is suitable for the fields of wearable intelligent equipment in low-voltage environment, aerospace and the like.
Drawings
FIG. 1 is a schematic structural diagram of a microcrack strain sensor provided in example 10;
FIG. 2 is a schematic diagram of the structure and working principle of the arc-shaped microcrack sensor provided by the invention;
FIG. 3 is a schematic diagram of the operation of the microcrack strain sensor of the present invention;
fig. 4a) is a scanning electron microscope picture of the brittle conductive thin film crack layer of the micro-crack strain sensor provided in example 2 in an initial state;
fig. 4b) is a scanning electron microscope picture of the brittle conductive thin film crack layer of the micro-crack strain sensor provided in example 2 at 50% strain;
FIG. 5 is a 3-dimensional scanning cross-sectional curve of the microcracked strain sensor of example 4 at different strains: a) 0% strain; b) 5% strain; c) 50% strain; d) enlarged view of figure c);
FIG. 6 is a 3-dimensional scan of the microcrack strain sensor of example 4 at different strains;
FIG. 7 is a graph of rate of change of resistance versus strain for the microcracked strain sensor of example 9;
fig. 8a) and 8b) are resistivity curves of the microcracked strain sensor of example 5 at 50% and 100% cyclic strain, respectively.
Detailed Description
For a better understanding of the present invention, the present invention is further described with reference to the following drawings and examples, but it should be noted that the examples are not to be construed as limiting the scope of the present invention.
The invention provides a micro-crack strain sensor which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer, wherein the flexible substrate layer is provided with a plurality of grooves; the raw material formula comprises the following components in parts by weight: 50-90 parts of a flexible substrate material and 0-5 parts of an elastomer cross-linking agent; 0-10 parts of an elastomer crosslinking assistant; 1-5 parts of a brittle film material; 0.01-0.5 part of conductive filler; 0-3 parts of an interface modifier.
The flexible substrate material is one or more of a thermosetting elastomer, a thermoplastic elastomer and a flexible film; the brittle film material is one or more of carboxymethyl chitosan, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, ethylene-vinyl acetate copolymer, cellulose acetate, ethyl cellulose, polyacrylamide, polymethyl methacrylate, polyvinyl chloride and polycarbonate; the conductive filler is one or more of carbon nano tube, graphene, conductive carbon black, nano silver wire, poly (3, 4-ethylenedioxythiophene), polyacetylene and polyaniline; the thermosetting elastomer is one or more of natural rubber, natural rubber latex, epoxidized natural rubber latex, ethylene propylene rubber, silicon rubber, fluororubber, nitrile rubber latex, carboxylated nitrile rubber latex, styrene butadiene rubber latex, carboxylated styrene butadiene rubber latex, eucommia ulmoides latex and dandelion latex, and the thermoplastic elastomer is one or more of styrene-butadiene block copolymer, ethylene-octene copolymer, polyurethane elastomer and polyamide elastomer.
The flexible film is made of one or more of polyimide, polyester, cyclic olefin polymer and liquid crystal polymer.
The elastomer crosslinking agent is one or more of a sulfur vulcanizing agent, a peroxide vulcanizing agent, a hydrosilylation crosslinking agent, an amine vulcanizing agent and a bisphenol vulcanizing agent.
The elastomer crosslinking auxiliary agent is one or more of zinc oxide, thiazole accelerant, sulfenamide accelerant, thiuram accelerant, thiocarbamate accelerant, guanidine accelerant, bisphenol accelerant, quaternary ammonium salt accelerant, quaternary phosphonium salt accelerant, cyanurate accelerant and transition metal coordination accelerant.
The carbon nano tube is one or more of a single-wall carbon nano tube and a multi-wall carbon nano tube; the conductive carbon black is one or more of oil furnace conductive carbon black, heavy oil reproduced conductive carbon black and calcium carbide acetylene conductive carbon black.
The interface modifier is one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, aluminum-titanium composite coupling agent, anionic surfactant, cationic surfactant and nonionic surfactant.
The invention also provides a preparation method of the micro-crack strain sensor, which comprises the following steps:
a) obtaining a flexible substrate layer, wherein the flexible substrate layer is a flexible film or an elastomer film or a flexible film-elastomer film composite flexible substrate layer; the preparation method of the elastomer film comprises the following steps: and sequentially adding an elastomer crosslinking agent, or the elastomer crosslinking agent and an elastomer crosslinking assistant, or the elastomer crosslinking agent, the elastomer crosslinking assistant and an interface modifier into the thermosetting elastomer latex or the thermosetting elastomer solution or the thermoplastic elastomer solution, uniformly mixing, and molding to obtain the elastomer film. In other words, in some embodiments, a flexible film on the market is used as the flexible substrate layer, an elastomer film is also used as the flexible substrate layer, and a flexible film-elastomer film composite flexible substrate layer formed by the laminated flexible film and the elastomer film is also used as the flexible substrate layer.
b) The preparation method of the brittle conductive film crack layer comprises the following steps:
i) and dissolving the brittle film material in a solvent to obtain a solution of the brittle film material.
ii) dispersing the conductive filler or the conductive filler and the interface modifier in the solution of the brittle film material under the ultrasonic action to obtain the conductive filler-brittle film material suspension.
iii) coating the solution in ii) on the surface of the flexible substrate layer in several times, and heating and drying to form a brittle conductive film layer on the surface of the flexible substrate layer.
iv) bending or stretching to form uniform cracks on the brittle conductive film layer in iii) to obtain a brittle conductive film crack layer.
c) And repeating the step a) to obtain a flexible substrate layer, covering the flexible substrate layer on the surface of the conductive film crack layer to be used as a flexible packaging layer to seal the conductive film crack layer, and obtaining the micro-crack strain sensor.
In some embodiments, between step a) and step b) further comprises surface treating the flexible substrate layer by one or more of electro/electroless plating, electrophoresis, chemical heat treatment, ozone, plasma, and laser surface treatment. And step iv) further comprises leading the conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode, and step c) further comprises leading the output electrode out of the flexible packaging layer.
Further preferably, the ultrasonic action time in the step ii) is 0.1-2 hours, and the ultrasonic action power is 100-10000W; the bending curvature radius of the step iv) is 1-5 mm, and the stretching speed is 50-2000 cm/min.
The prepared micro-crack strain sensor can be a laminated strip sensor, can respond to strain in any direction, is particularly sensitive to strain in a horizontal plane caused by stretching or compression, and has relatively low sensitivity to strain which is inclined to the micro-crack strain sensor vertically or at a certain angle such as pressing. Therefore, further, for the strain of the microcrack strain sensor and the like pressed in the vertical direction, the manufacturing method of the microcrack strain sensor can further add the step d): fixing two ends of the micro-crack strain sensor prepared in the step c), and suspending the middle of the micro-crack strain sensor to prepare the micro-crack strain sensor with an arc structure, wherein the structure can convert the strain vertical to or at a certain inclination angle of the arc micro-crack strain sensor into the strain in a horizontal plane, so that the sensitivity of the micro-crack strain sensor to the strain at the vertical or a certain inclination angle is improved. The working principle of the arc-shaped micro-crack strain sensor when being subjected to vertical strain such as pressing is shown in fig. 2. Similarly, when the arc-shaped microcrack strain sensor is pressed at a certain inclination angle, the arc-shaped microcrack strain sensor can also convert the strain in the inclination direction into the strain in the horizontal plane, and therefore, the arc-shaped microcrack strain sensor can also improve the sensitivity to the strain in the inclination direction.
Example 1
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 30 percent is selected as a flexible substrate material, an elastomer crosslinking agent is sulfur, an elastomer crosslinking aid is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, and a conductive filler is a single-walled carbon nanotube. 2phr of sulfur, 1phr of ZDEC, and 0.5phr of zinc oxide were added to the epoxidized natural rubber latex, and the latex was ultrasonically treated with an ultrasonic device for 0.5 hour to uniformly disperse the vulcanization system in the latex to obtain an epoxidized natural rubber latex containing a vulcanization system. 2g of epoxidized natural rubber latex containing the vulcanization system were introduced into a 30cm by 2cm polytetrafluoroethylene mold and spread uniformly. And (3) putting the mould into an oven at 80 ℃ for drying and vulcanizing for 2h to obtain the flexible substrate layer. 0.1g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotube (the mass of the single-walled carbon nanotube is 1 percent of that of the carboxymethyl chitosan) is added, and the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension. And adding the suspension into a polytetrafluoroethylene mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. Manufacturing micro cracks by adopting a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to be used as an output electrode. 1g of epoxidized natural rubber latex containing a vulcanization system is added into a mold, dried at 80 ℃ and vulcanized for 2 hours to serve as a flexible packaging layer to seal the conductive film crack layer, and an output electrode is led out of the flexible packaging layer.
Example 2
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 10 percent is selected as a flexible substrate material, an elastomer crosslinking agent is sulfur, an elastomer crosslinking aid is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, and a conductive filler is a single-walled carbon nanotube. 2phr of sulfur, 1phr of ZDEC, and 0.5phr of zinc oxide were added to the epoxidized natural rubber latex, and the latex was ultrasonically treated with an ultrasonic device for 0.5 hour to uniformly disperse the vulcanization system in the latex to obtain an epoxidized natural rubber latex containing a vulcanization system. 2g of epoxidized natural rubber latex containing the vulcanization system were introduced into a 20cm by 2cm polytetrafluoroethylene mold and spread uniformly. And (3) putting the mould into an oven at 80 ℃ for drying and vulcanizing for 2 hours to obtain the flexible substrate layer. 0.1g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotube (the single-walled carbon nanotube accounts for 1 percent of the mass of the carboxymethyl chitosan) is added, and the suspension of the uniformly dispersed single-walled carbon nanotube is obtained after ultrasonic treatment for 0.5 h. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. 1g of epoxidized natural rubber latex containing a vulcanization system is added into a mold, dried at 80 ℃ and vulcanized for 2 hours to serve as a flexible packaging layer to seal the conductive film crack layer, and an output electrode is led out of the flexible packaging layer.
Example 3
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
selecting carboxylic styrene-butadiene rubber latex with 1 percent of carboxyl content as a flexible substrate material, an elastomer crosslinking agent is sulfur, an elastomer crosslinking auxiliary agent is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, and a conductive filler is a single-walled carbon nanotube. 2phr of sulfur, 1phr of ZDEC and 0.5phr of zinc oxide are added into the carboxylated styrene-butadiene rubber latex, and the latex is subjected to ultrasonic treatment for 0.5h by adopting ultrasonic equipment, so that a vulcanization system is uniformly dispersed in the latex to obtain the carboxylated styrene-butadiene rubber latex containing the vulcanization system. 2g of carboxylated styrene-butadiene rubber latex containing the vulcanization system was placed in a 30cm by 2cm teflon mold and spread uniformly. And (3) putting the mould into an oven at 80 ℃ for drying and vulcanizing for 2h to obtain the flexible substrate layer. 0.1g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotube (the mass of the single-walled carbon nanotube is 1 percent of that of the carboxymethyl chitosan) is added, and the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. Adding 1g of carboxylic styrene butadiene rubber latex containing a vulcanization system into a mold, drying at 80 ℃, vulcanizing for 2h to serve as a flexible packaging layer to seal the conductive film crack layer, and leading an output electrode out of the flexible packaging layer.
Example 4
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 30% is selected as a flexible substrate material, an elastomer cross-linking agent is sulfur, an elastomer cross-linking auxiliary agent is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is sodium carboxymethylcellulose, and a conductive filler is a single-walled carbon nanotube. 2phr of sulfur, 1phr of ZDEC, and 0.5phr of zinc oxide were added to the epoxidized natural rubber latex, and the latex was ultrasonically treated with an ultrasonic device for 0.5 hour to uniformly disperse the vulcanization system in the latex to obtain an epoxidized natural rubber latex containing a vulcanization system. 2g of epoxidized natural rubber latex containing the vulcanization system were introduced into a 10cm by 2cm polytetrafluoroethylene mold and spread uniformly. And (3) putting the mould into an oven at 80 ℃ for drying and vulcanizing for 2h to obtain the flexible substrate layer. 0.1g of sodium carboxymethylcellulose is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotube (the mass of the single-walled carbon nanotube is 1 percent of that of the sodium carboxymethylcellulose) is added, and the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. Manufacturing micro cracks by adopting a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to be used as an output electrode. 1g of epoxidized natural rubber latex containing a vulcanization system is added into a mold, dried at 80 ℃ and vulcanized for 2 hours to serve as a flexible packaging layer to seal the conductive film crack layer, and an output electrode is led out of the flexible packaging layer.
Example 5
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 30% is selected as a flexible substrate material, an elastomer cross-linking agent is sulfur, an elastomer cross-linking assistant is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, and a conductive filler is a single-walled carbon nanotube. 2phr of sulfur, 1phr of ZDEC, and 0.5phr of zinc oxide were added to the epoxidized natural rubber latex, and the latex was ultrasonically treated with an ultrasonic device for 0.5 hour to uniformly disperse the vulcanization system in the latex to obtain an epoxidized natural rubber latex containing a vulcanization system. 2g of epoxidized natural rubber latex containing the vulcanization system were introduced into a 6cm by 2cm polytetrafluoroethylene mold and spread uniformly. And (3) putting the mould into an oven at 80 ℃ for drying and vulcanizing for 2h to obtain the flexible substrate layer. 0.1g of carboxymethyl chitosan was dissolved in 10ml of deionized water and 0.01g of poly (3, 4-ethylenedioxythiophene) (poly (3, 4-ethylenedioxythiophene) accounting for 10% of the mass of carboxymethyl chitosan) was added and sonicated for 0.5h to give a uniformly dispersed suspension of poly (3, 4-ethylenedioxythiophene). And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. 1g of epoxidized natural rubber latex containing a vulcanization system is added into a mold, dried at 80 ℃ and vulcanized for 2 hours to serve as a flexible packaging layer to seal the conductive film crack layer, and an output electrode is led out of the flexible packaging layer.
Example 6
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
selecting silicon rubber as a flexible substrate material, an elastomer cross-linking agent as dicumyl peroxide, a brittle film material as carboxymethyl chitosan, and a conductive filler as a nano silver wire. The silicone rubber was dissolved in methylene chloride solvent, and 2phr of elastomer crosslinking agent dicumyl peroxide was added to disperse it uniformly in the silicone rubber solution to obtain a silicone rubber solution containing a vulcanization system. 2g of the silicone rubber solution containing the vulcanization system were introduced into a 6cm by 2cm polytetrafluoroethylene mold and spread uniformly. And (3) putting the mould into a 160 ℃ oven for drying and vulcanizing for 2h to obtain the flexible substrate layer. 0.1g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.001g of nano silver wire (the mass of the nano silver wire is 1 percent of that of the carboxymethyl chitosan) is added, and the nano silver wire is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed nano silver wire suspension. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. 1g of silicon rubber solution containing a vulcanization system is added into a mold, dried at 160 ℃ and vulcanized for 2 hours to serve as a flexible packaging layer to seal the conductive film crack layer, and the output electrode is led out of the flexible packaging layer.
Example 7
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
selecting carboxyl nitrile rubber as a flexible substrate material, an elastomer cross-linking agent is dicumyl peroxide, a brittle film material is carboxymethyl chitosan, a conductive filler is polyaniline, and an interface modifier is a silane coupling agent bis- [3- (triethoxysilyl) propyl ] -tetrasulfide (TESPT). Dissolving carboxyl nitrile rubber in a solvent, adding 2phr of dicumyl peroxide, and carrying out ultrasonic treatment on the solution for 0.5h by adopting ultrasonic equipment to uniformly disperse a vulcanization system in the carboxyl nitrile rubber solution to obtain the carboxyl nitrile rubber solution containing the vulcanization system. 2g of carboxylated nitrile rubber solution containing the vulcanization system are introduced into a 6cm by 2cm polytetrafluoroethylene mould, and spread out uniformly. And (3) putting the mould into a 160 ℃ oven for drying and vulcanizing for 2h to obtain the flexible substrate layer. The flexible substrate layer was surface treated with TESPT. 0.1g of carboxymethyl chitosan is dissolved in 100ml of Dimethylformamide (DMF), 0.01g of polyaniline (the mass of the polyaniline is 10 percent of that of the carboxymethyl chitosan) is added, and the polyaniline-carboxymethyl chitosan solution is obtained after ultrasonic treatment for 0.5 h. And adding the solution into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. Adding 1g of carboxylic nitrile rubber solution containing a vulcanization system into a mold, drying at 160 ℃, vulcanizing for 2h to serve as a flexible packaging layer to seal the conductive film crack layer, and leading an output electrode out of the flexible packaging layer.
Example 8
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
selecting a commercial polyester film as a flexible substrate layer, a brittle film material as polyacrylamide, and a conductive filler as a single-walled carbon nanotube. 0.1g of polyacrylamide is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotube (the mass of the single-walled carbon nanotube is 1 percent of that of the polyacrylamide) is added, and the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension. And spraying the suspension on the surface of the polyester film for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. Manufacturing a micro-crack by adopting a pre-stretching mode (the stretching speed is 500mm/min), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to be used as an output electrode. Covering the polyester film on the surface of the brittle conductive film crack layer to serve as a flexible packaging layer to seal the conductive film crack layer, and leading the output electrode out of the flexible packaging layer.
Example 9
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
the method selects a commercial polyimide film as a flexible substrate layer, a fragile film material is cellulose acetate, a conductive filler is a multi-wall carbon nano tube, and an interface modifier is an anionic surfactant sodium dodecyl benzene sulfonate. Firstly, the surface treatment is carried out on the polyimide film by adopting sodium dodecyl benzene sulfonate. 0.1g of cellulose acetate is dissolved in 10ml of deionized water, 0.002g of multi-walled carbon nano-tube (the mass of the multi-walled carbon nano-tube is 2 percent of that of polyacrylamide) is added, and ultrasonic treatment is carried out for 0.5h to obtain the evenly dispersed multi-walled carbon nano-tube suspension. And spraying the suspension on the surface of the polyester film for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. Manufacturing a micro-crack by adopting a pre-stretching mode (the stretching speed is 500mm/min), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to be used as an output electrode. Covering the surface of the brittle conductive film crack layer with the surface-treated polyester film to serve as a flexible packaging layer to seal the conductive film crack layer, and leading the output electrode out of the flexible packaging layer.
Example 10
The embodiment provides a microcrack strain sensor, as shown in fig. 1, including flexible substrate layer 1, fragile conductive film crack layer 2 and flexible encapsulation layer 3 stacked in sequence from bottom to top, flexible substrate layer 1 includes flexible thin film layer 11 and elastomer thin film layer 12 stacked from bottom to top, as shown in fig. 3, fragile conductive film crack layer includes body layer 21 and transition layer 22, flexible encapsulation layer 3 includes elastomer thin film encapsulation layer 31 and flexible thin film encapsulation layer 32 stacked from bottom to top, the microcrack strain sensor preparation method is as follows:
epoxidized natural rubber latex with the epoxy degree of 30 percent and a polyimide film are selected as flexible substrate materials, an elastomer crosslinking agent is sulfur, an elastomer crosslinking aid is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, a conductive filler is a single-walled carbon nanotube, and an interface modifier is silane coupling agent gamma-methacryloxypropyl trimethoxysilane (KH 570). To the epoxidized natural rubber latex was added 2phr of sulfur, 1phr of ZDEC, 0.5phr of zinc oxide, and 2phr of KH 570. And (3) carrying out ultrasonic treatment on the latex by adopting ultrasonic equipment for 0.5h, so that the vulcanization system and the interface modifier are uniformly dispersed in the latex to obtain the epoxidized natural rubber latex containing the vulcanization system and the interface modifier. 2g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier is coated on the surface of a polyimide film and is put into an oven at 80 ℃ for drying and vulcanization for 2 hours to obtain a flexible film layer 11 and an elastomer film layer 12 which are laminated from bottom to top as a flexible substrate layer 1. And electroplating the upper surface of the flexible substrate layer. 0.1g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.001g of single-walled carbon nanotubes (the single-walled carbon nanotubes are 1 percent of the mass of the carboxymethyl chitosan) and 1phr of KH570 are added, and the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing micro cracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer 2, and introducing a conductive copper sheet into the brittle conductive film crack layer 2 to serve as an output electrode (not shown). Coating 1g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier on the surface of a polyimide film, drying the coated film in an oven at 80 ℃, vulcanizing the coated film for 2 hours to obtain a polyimide film-epoxidized natural rubber latex film composite layer, covering the polyimide film-epoxidized natural rubber latex film composite layer on a fragile conductive film crack layer 2 to serve as a flexible packaging layer 3 to seal the conductive film crack layer, attaching the epoxidized natural rubber latex film layer to the fragile conductive film crack layer, and leading an output electrode out of the flexible packaging layer.
Example 11
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 30 percent and a polyimide film are selected as flexible substrate materials, an elastomer crosslinking agent is sulfur, an elastomer crosslinking aid is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan and polycarbonate, a conductive filler is a single-walled carbon nanotube, and an interface modifier is silane coupling agent gamma-methacryloxypropyl trimethoxysilane (KH 570). To the epoxidized natural rubber latex was added 2phr of sulfur, 1phr of ZDEC, 0.5phr of zinc oxide, and 2phr of KH 570. And (3) carrying out ultrasonic treatment on the latex by adopting ultrasonic equipment for 0.5h, so that the vulcanization system and the interface modifier are uniformly dispersed in the latex to obtain the epoxidized natural rubber latex containing the vulcanization system and the interface modifier. 2g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier is coated on the surface of a polyimide film and is put into an oven at 80 ℃ to be dried and vulcanized for 2 hours to prepare a flexible substrate layer. And electroplating the surface of the flexible substrate layer. 0.05g of carboxymethyl chitosan is dissolved in 10ml of deionized water, 0.0005g of single-walled carbon nanotube (the single-walled carbon nanotube accounts for 1 percent of the mass of the carboxymethyl chitosan) and 1phr of KH570 are added, ultrasonic treatment is carried out for 0.5h to obtain a uniformly dispersed single-walled carbon nanotube suspension, and the suspension is added into a mould for drying in 2 times. 0.05g of polycarbonate is dissolved in 20ml of dichloromethane, 0.0005g of single-walled carbon nanotubes (the single-walled carbon nanotubes account for 1% of the mass of the polycarbonate) and 1phr of KH570 are added, the mixture is subjected to ultrasonic treatment for 0.5h to obtain a uniformly dispersed suspension of the single-walled carbon nanotubes, and the suspension is added into a mold in 2 times and dried. And drying for 8 hours at the temperature of 60 ℃ to obtain the composite brittle conductive film layer. Manufacturing micro cracks by adopting a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to be used as an output electrode. Coating 1g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier on the surface of a polyimide film, drying the coated film in an oven at 80 ℃, vulcanizing the coated film for 2 hours to obtain a polyimide film-epoxidized natural rubber latex film composite layer, covering the polyimide film-epoxidized natural rubber latex film composite layer on a fragile conductive film crack layer to serve as a flexible packaging layer to seal the fragile conductive film crack layer, attaching the epoxidized natural rubber latex film layer to the fragile conductive film crack layer, and leading an output electrode out of the flexible packaging layer.
Example 12
The embodiment provides a microcrack strain sensor, which comprises a flexible substrate layer, a brittle conductive film crack layer and a flexible packaging layer which are sequentially stacked from bottom to top, wherein the preparation method comprises the following steps:
epoxidized natural rubber latex with the epoxy degree of 30 percent and a polyimide film are selected as flexible substrate materials, an elastomer crosslinking agent is sulfur, an elastomer crosslinking aid is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), a brittle film material is carboxymethyl chitosan, a conductive filler is a single-walled carbon nanotube and poly (3, 4-ethylenedioxythiophene), and an interface modifier is a silane coupling agent gamma-methacryloxypropyltrimethoxysilane (KH 570). To the epoxidized natural rubber latex, 2phr of sulfur, 1phr of ZDEC, 0.5phr of zinc oxide, and 2phr of KH570 were added. And (3) carrying out ultrasonic treatment on the latex by adopting ultrasonic equipment for 0.5h, so that the vulcanization system and the interface modifier are uniformly dispersed in the latex to obtain the epoxidized natural rubber latex containing the vulcanization system and the interface modifier. 2g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier is coated on the surface of a polyimide film and is put into an oven at 80 ℃ to be dried and vulcanized for 2 hours to prepare a flexible substrate layer. And electroplating the surface of the flexible substrate layer. 0.1g of carboxymethyl chitosan was dissolved in 10ml of deionized water, and 0.001g of single-walled carbon nanotubes and 0.001g of poly (3, 4-ethylenedioxythiophene) (both single-walled carbon nanotubes and poly (3, 4-ethylenedioxythiophene) were 1% by mass of carboxymethyl chitosan) and 1phr of KH570 were added, and sonication was performed for 0.5h to obtain a uniformly dispersed suspension. And adding the suspension into a mold for 4 times, and drying in an oven at 60 ℃ for 8 hours to obtain the brittle conductive film layer. The method comprises the steps of manufacturing microcracks in a pre-bending mode (the curvature radius is 1mm), obtaining a brittle conductive film crack layer, and introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode. Coating 1g of epoxidized natural rubber latex containing a vulcanization system and an interface modifier on the surface of a polyimide film, drying the coated film in an oven at 80 ℃, vulcanizing the coated film for 2 hours to obtain a polyimide film-epoxidized natural rubber latex film composite layer, covering the polyimide film-epoxidized natural rubber latex film composite layer on a fragile conductive film crack layer to serve as a flexible packaging layer to seal the fragile conductive film crack layer, attaching the epoxidized natural rubber latex film layer to the fragile conductive film crack layer, and leading an output electrode out of the flexible packaging layer.
Comparative example 1
Epoxidized natural rubber latex with the epoxy degree of 30 percent is selected as a matrix, an elastomer crosslinking agent is sulfur, an elastomer crosslinking assistant is zinc oxide and Zinc Diethyldithiocarbamate (ZDEC), and a conductive filler is a single-walled carbon nanotube. Adding 0.05g of single-walled carbon nanotubes into 100ml of deionized water; carrying out ultrasonic treatment on the single-walled carbon nanotube suspension for 0.5h by adopting ultrasonic equipment to obtain uniformly dispersed single-walled carbon nanotube suspension; adding the single-walled carbon nanotubes into 5g of epoxidized natural rubber latex, and performing ultrasonic treatment for 0.5h to uniformly disperse the single-walled carbon nanotubes among latex particles; and (3) placing the obtained suspension in an oven for drying and vulcanizing at 60 ℃ for 24h to obtain the epoxidized natural rubber/single-walled carbon nanotube composite material with the isolation structure.
A series of performance tests were performed on the microcrack strain sensors of examples 1-12 and the epoxidized natural rubber/single-walled carbon nanotube composite of comparative example 1, the performance test methods being as follows:
first, the prepared sample was cut into dumbbell-shaped specimens with a cutter. The bars were then secured with a jig on a rubber tensile machine. And finally, connecting the electrodes at the two ends of the sample strip with a universal meter. The resistance change was measured during stretching of the specimen.
In the tensile test, the tensile rate of the sample strip is 10 mm/min; in the cyclic tensile test, the tensile rate and recovery rate of the specimens are both 10mm/min, and the maximum strain is 50% and 100%, respectively. The multimeter selects the two-wire resistance mode, and the frequency of resistance measurements is 40 times/second.
The performance data for the microcrack strain sensors of examples 1-12 and the epoxidized natural rubber/single-walled carbon nanotube composite of comparative example 1 are shown in Table 1.
TABLE 1 Performance data for the microcrack strain sensors of examples 1-12 and the epoxidized natural rubber/single-walled carbon nanotube composites of comparative example 1
| GF value | Strain response Range (%) | |
| Comparative example 1 | 20 | 50-200 |
| Example 1 | 450000 | 5-30 |
| Example 2 | 260000 | 5-50 |
| Example 3 | 130000 | 20-100 |
| Example 4 | 120000 | 10-50 |
| Example 5 | 40000 | 50-100 |
| Example 6 | 50000 | 20-50 |
| Example 7 | 200000 | 5-20 |
| Example 8 | 100000 | 1-5 |
| Example 9 | 120000 | 1-5 |
| Example 10 | 150000 | 2-10 |
| Example 11 | 200000 | 2-20 |
| Example 12 | 180000 | 5-10 |
The properties of examples 1 to 12 are shown in Table 1. The example numbers in the table correspond to the examples described above.
Comparing comparative example 1 and example 1, the flexible substrate layer-brittle conductive layer based micro-crack strain sensor of the present invention has a higher GF value and a lower strain response range than the conventional conductive composite type strain sensor.
Comparing example 1 with example 2, epoxidized natural rubber latex with different epoxy degrees is used as the flexible substrate layer, which has obvious influence on the interaction size between the flexible substrate layer and the brittle conductive film crack layer, and further influences the GF value and the strain response range.
Comparing example 1 and example 3, different elastomeric films were selected as the flexible substrate layer; comparing example 1 with example 4, different brittle film materials were selected; comparing example 1 with example 5, different conductive fillers were selected; comparing example 1 with example 6, different elastomer films were selected as the flexible substrate layer and different conductive fillers, which resulted in better strain sensing performance.
Comparing the embodiment 1 with the embodiment 8, different flexible substrate materials are selected as substrate layers, and the strain response ranges of the strain sensor are obviously different, namely when the flexible substrate layers are elastomer thin films, larger strain is needed to realize resistance mutation; when the flexible substrate layer is a commercial flexible film, abrupt resistance changes can be realized under small strain. In the practical application process, the substrate layer can be flexibly selected according to the applicable environment.
Comparing example 8 with example 9, after surface treatment of the surface of the commercial flexible film, the interfacial interaction between the flexible substrate layer and the brittle conductive film crack layer was increased, the thickness of the transition layer was increased, and the GF value was increased.
Comparing the embodiment 10 with the embodiment 1, the flexible film-elastomer film composite is selected as the flexible substrate layer, and the strain sensor has better strain sensing performance and can be applied to the fields of touch screens and the like.
Comparing the example 10 with the example 11, the multilayer brittle conductive film crack layer is formed by compounding different brittle conductive films, and the strain response range can be effectively expanded.
Compared with the embodiment 10 and the embodiment 12, different types of conductive fillers are selected for compounding, so that the resistance before mutation can be effectively reduced, and the GF value can be effectively improved.
Fig. 1 is a schematic structural diagram of the micro-crack strain sensor obtained in embodiment 10, which is composed of a flexible substrate layer, a brittle conductive thin film crack layer, and a flexible package layer, and an electrode is introduced to implement electrical signal output.
Fig. 2 is a schematic view of the working principle of the arc-type micro-crack strain sensor provided by the invention under the strain in the vertical direction. When the arc-shaped microcrack strain sensor is vertically pressed, the strain in the vertical direction of the arc-shaped microcrack strain sensor is converted into the strain in the horizontal plane.
FIG. 3 is a schematic diagram of the operation of the microcrack strain sensor of the present invention, wherein for tensile strain, in the initial state, the cracks of the brittle conductive film crack layer are substantially in a closed state; when tensile strain is applied to the micro-crack strain sensor, the cracks of the brittle conductive film crack layer gradually expand, and the resistance sharply increases; when the strain is removed, the cracks gradually disappear and the resistance decreases. For the pressing strain, in the initial state, the micro-crack strain sensor is in a pre-stretching state, and the cracks of the brittle conductive film crack layer are in an expansion state; when a certain pressing strain is applied to the micro-crack strain sensor, the cracks of the brittle conductive film crack layer are gradually closed, and the resistance is sharply reduced; when the strain is removed, the cracks gradually recover and the resistance increases.
Fig. 4a) is a scanning electron microscope picture of the brittle conductive film crack layer of the micro-crack strain sensor obtained in example 2 in an initial state, and compared with a smooth conductive film surface, the crack has obvious wrinkles; fig. 4b) is a scanning electron microscope image of the brittle conductive film crack layer in example 2 at 50% strain, and it can be clearly seen that the crack propagation modes of the bulk layer 21 and the transition layer 22 of the brittle conductive film crack layer are obviously different.
FIG. 5a) is a 3-dimensional scanning cross-sectional curve of the initial state of the micro-crack strain sensor obtained in example 4, wherein the width of the micro-crack is 9.1 μm and the depth is 5.6 μm; fig. 5b) is a 3-dimensional scanning cross-sectional curve of a flexible substrate layer-brittle conductive layer based micro-crack strain sensor with strain increased to 5%, the width and depth of the micro-crack increased to 23.9 μm and 15.7 μm, respectively; fig. 5c) is a 3-dimensional cross-sectional scan curve of a micro-crack strain sensor based on a flexible substrate layer-brittle conductive layer with strain increased to 50%, the width and depth of the micro-crack increased to 188.1 μm and 24.6 μm, respectively, and the transition layer cracked at this time, and fig. 5d shows that the crack depth of the transition layer was about 1.5 μm (i.e., the depth of the transition layer 22).
Fig. 6 is a 3-dimensional scan of the microcracked strain sensor obtained in example 4 at different strains, with crack width and depth increasing as the strain increases.
FIG. 7 is a graph of the rate of change of resistance versus strain for the microcracked strain sensor obtained in example 9, with the rate of change of resistance increasing dramatically as the strain increases. When the strain was 5%, the resistance change rate was as high as 40000.
Fig. 8a) and 8b) are resistivity curves of the micro-crack strain sensor obtained in example 5 under 50% and 100% cyclic strain, respectively, the resistivity changes are substantially synchronous with the strain and do not decay with the increase of the number of cycles, which shows that the micro-crack strain sensor based on the flexible substrate layer-the brittle conductive layer has good durability.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.
Claims (10)
1. A microcrack strain sensor, comprising: the packaging structure comprises a flexible substrate layer, a fragile conductive film crack layer and a flexible packaging layer; the microcrack strain sensor comprises the following raw materials in parts by weight:
the flexible substrate material is one or more of a thermosetting elastomer, a thermoplastic elastomer and a flexible film;
the brittle film material is one or more of carboxymethyl chitosan, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, ethylene-vinyl acetate copolymer, cellulose acetate, ethyl cellulose, polyacrylamide, polymethyl methacrylate, polyvinyl chloride and polycarbonate;
the conductive filler is one or more of carbon nano tubes, graphene, conductive carbon black, nano silver wires, poly (3, 4-ethylenedioxythiophene), polyacetylene and polyaniline.
2. The microcrack strain sensor of claim 1, wherein: the thermosetting elastomer is one or more of natural rubber, natural rubber latex, epoxidized natural rubber latex, ethylene propylene rubber, silicon rubber, fluororubber, nitrile rubber latex, carboxylated nitrile rubber latex, styrene butadiene rubber latex, carboxylated styrene butadiene rubber latex, eucommia ulmoides latex and dandelion latex, and the thermoplastic elastomer is one or more of styrene-butadiene block copolymer, ethylene-octene copolymer, polyurethane elastomer and polyamide elastomer; the flexible film is made of one or more of polyimide, polyester, cyclic olefin polymer and liquid crystal polymer.
3. The microcrack strain sensor of claim 1, wherein: the elastomer crosslinking agent is one or more of a sulfur vulcanizing agent, a peroxide vulcanizing agent, a hydrosilylation crosslinking agent, an amine vulcanizing agent and a bisphenol vulcanizing agent.
4. The microcrack strain sensor of claim 1, wherein: the elastomer crosslinking auxiliary agent is one or more of zinc oxide, thiazole accelerant, sulfenamide accelerant, thiuram accelerant, thiocarbamate accelerant, guanidine accelerant, bisphenol accelerant, quaternary ammonium salt accelerant, quaternary phosphonium salt accelerant, cyanurate accelerant and transition metal coordination accelerant.
5. The microcrack strain sensor of claim 1, wherein: the carbon nano tube is one or more of a single-wall carbon nano tube and a multi-wall carbon nano tube; the conductive carbon black is one or more of oil furnace conductive carbon black, heavy oil reproduced conductive carbon black and calcium carbide acetylene conductive carbon black.
6. The microcrack strain sensor of claim 1, wherein: the interface modifier is one or more of silane coupling agent, titanate coupling agent, aluminate coupling agent, aluminum-titanium composite coupling agent, anionic surfactant, cationic surfactant and nonionic surfactant.
7. A method for manufacturing a microcrack strain sensor according to any one of claims 1 to 6, comprising the steps of:
a) obtaining a flexible substrate layer, wherein the flexible substrate layer is a flexible film or an elastomer film or a flexible film-elastomer film composite flexible substrate layer; the preparation method of the elastomer film comprises the following steps: sequentially adding an elastomer crosslinking agent, or an elastomer crosslinking agent and an elastomer crosslinking assistant, or an elastomer crosslinking agent, an elastomer crosslinking assistant and an interface modifier into thermosetting elastomer latex or a thermosetting elastomer solution or a thermoplastic elastomer solution, uniformly mixing, and molding to obtain the elastomer film;
b) the preparation method of the brittle conductive film crack layer comprises the following steps:
i) dissolving a brittle film material in a solvent to obtain a solution of the brittle film material;
ii) dispersing the conductive filler or the conductive filler and the interface modifier in the solution of the brittle film material under the ultrasonic action to obtain a conductive filler-brittle film material suspension;
iii) coating the conductive filler-brittle film material suspension obtained in the step ii) on the surface of the flexible substrate layer in a plurality of times, and heating and drying to form a brittle conductive film layer on the surface of the flexible substrate layer;
iv) forming uniform cracks on the brittle conductive film layer obtained in the step iii) in a bending or stretching mode to obtain a brittle conductive film crack layer;
c) and repeating the step a) to obtain a flexible substrate layer, covering the flexible substrate layer on the surface of the conductive film crack layer to serve as a flexible packaging layer to seal the conductive film crack layer, and obtaining the microcrack strain sensor.
8. The method of claim 7, further comprising between step a) and step b) performing a surface treatment on the flexible substrate layer, wherein the surface treatment is one or more of electroplating, electroless plating, electrophoresis, chemical heat treatment, ozone, plasma and laser surface treatment; and step iv) further comprises introducing a conductive copper sheet into the brittle conductive film crack layer to serve as an output electrode, and step c) further comprises leading the output electrode out of the flexible packaging layer.
9. The method for preparing the micro-crack strain sensor according to claim 7, wherein the ultrasonic action time in the step ii) is 0.1-2 hours, and the ultrasonic action power is 100-10000W; the bending curvature radius of the step iv) is 1-5 mm, and the stretching speed is 50-2000 cm/min.
10. The method of making a microcrack strain sensor of claim 7, adding step d): fixing two ends of the micro-crack strain sensor prepared in the step c), and suspending the middle of the micro-crack strain sensor to form the micro-crack strain sensor with an arc structure.
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| CN105783697B (en) * | 2016-05-18 | 2018-08-14 | 郑州大学 | Flexible strain transducer with crack structtire and preparation method thereof |
| CN108444377B (en) * | 2018-03-18 | 2019-10-01 | 吉林大学 | Rule-based micron crackle array structure flexibility strain transducer and preparation method thereof |
| CN110105590B (en) * | 2019-04-30 | 2021-09-24 | 南京林业大学 | Preparation method and application of flexible strain sensor based on carboxymethyl cellulose/lithium chloride-polyacrylamide hydrogel |
| CN111721192B (en) * | 2020-06-30 | 2020-12-29 | 暨南大学 | Strain sensor based on graphical induced cracks and preparation method thereof |
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