Photochromic fabric sensor and preparation method thereof

Abstract

The invention discloses a photochromic fabric sensor and also discloses a preparation method of the sensor, and the preparation method comprises the following steps: preparing a spiropyran compound by using salicylaldehyde and indole; wrapping a spiropyrane compound by using a miniemulsion polymerization method to obtain a photochromic microcapsule dispersion liquid; after the photochromic microcapsule dispersion liquid is diluted, the fabric is soaked in the photochromic microcapsule dispersion liquid, and the photochromic fabric is obtained; the preparation method comprises the following steps: dehydrating polyether polyol, reacting the dehydrated polyether polyol with a hydrophilic monomer, an organic silicon modifier, an organic tin catalyst and diisocyanate to obtain a polyurethane prepolymer, and adding a chain extender and a neutralizer for continuous reaction to obtain an organic silicon modified polyurethane dispersion liquid; and mixing the organic silicon modified polyurethane dispersion liquid with a conductive material, and spraying the mixture on the surface of the photochromic fabric to obtain the photochromic fabric sensor. The preparation method is simple in process and low in cost, and the prepared sensor has the photochromic characteristic and excellent sensing performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fabric sensors, and relates to a photochromic fabric sensor. BACKGROUND

[0002] Fabric-based sensors are prepared by embedding or integrating conductive materials into fabrics. Compared with traditional rigid sensors, fabric-based sensors have excellent flexibility, can be easily bent, have good air permeability and durability, and have high sensitivity. These significant advantages make fabric-based sensors perfectly fit the wearing needs of the human body. When used in the field of human motion monitoring, fabric-based sensors can capture subtle changes in human motion in real time, providing accurate data support for athlete training monitoring, sports rehabilitation, injury recovery evaluation, etc.

[0003] With the continuous progress of technology and the continuous expansion of application scenarios, sensors with single sensing function have been difficult to meet the diversified needs of complex application fields such as human signal monitoring, medical diagnosis, and human-computer interaction. Under this background, integrating multiple sensing functions into one device has become an important development trend of flexible sensors. For example, a flexible sensing fabric capable of simultaneously detecting and distinguishing temperature and pressure is disclosed in Chinese Patent No. CN114892330A, published on August 12, 2022. Graphene and iron molybdate are used as raw materials to prepare conductive fibers by wet spinning, and then the conductive fibers are woven into a fabric to obtain a sensor. The sensor has high temperature sensing sensitivity and high pressure sensing sensitivity, but the method has high cost and the preparation process is relatively complex.

[0004] Chinese Patent No. CN118792886A, published on October 18, 2024, discloses a fabric sensor capable of monitoring pH and temperature. The sensor is woven from warp yarn and weft yarn. The warp yarn is cotton yarn, and the weft yarn contains cotton yarn, pH sensing yarn, and temperature sensing yarn. The pH sensing yarn is realized by polyaniline, and the temperature sensing yarn is realized by PEDOT:PSS, and both are prepared by electrospinning technology. The sensor made of functional yarns of this method has excellent performance, but the overall process is relatively complex and the cost is high. SUMMARY

[0005] The purpose of the present application is to provide a photochromic fabric sensor with photochromic properties and excellent sensing performance.

[0006] Another purpose of the present application is to provide a preparation method of the above-mentioned fabric sensor, which has the characteristics of simple process and low cost.

[0007] The technical scheme adopted by the present application is a preparation method of a photochromic fabric sensor, in particular to: Step 1, a spiropyran compound is prepared by using salicylaldehyde and indole; Step 2, the spiropyran compound is wrapped by using a miniemulsion polymerization method to obtain a photochromic microcapsule dispersion liquid; Step 3, after the photochromic microcapsule dispersion liquid is diluted, the fabric is soaked in the photochromic microcapsule dispersion liquid to obtain a photochromic fabric; Step 4, polyether polyol is dehydrated, and then is reacted with a hydrophilic monomer, an organic silicon modifier, an organic tin catalyst and a diisocyanate to obtain a polyurethane prepolymer, and then a chain extender and a neutralizing agent are added to continue the reaction to obtain an organic silicon modified polyurethane dispersion liquid; Step 5, after the organic silicon modified polyurethane dispersion liquid is mixed with a conductive material, the mixture is sprayed on the surface of the photochromic fabric to obtain the photochromic fabric sensor.

[0008] The present application also has the following characteristics: Step 1 is specifically as follows: Salicylaldehyde and indole with a molar ratio of 1:1 are added into ethanol, and stirring is performed to form a transparent solution, then piperidine is slowly added dropwise as a catalyst, the system is uniformly mixed, and then the temperature is increased to 80-90 DEG C for reaction for 3-4 h, polymerization is performed through hydroxy aldehyde condensation, then the reaction product is filtered and dried to obtain the spiropyran compound.

[0009] The spiropyran compound is one of 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzene spiropyran, 1-nitro-3,3-dimethylindoline-6'-nitrobenzene spiropyran, 1-hydroxy-3,3-dimethylindoline-6'-nitrobenzene spiropyran and 1-methyl-3,3-dimethylindoline-6'-nitrobenzene spiropyran.

[0010] Step 2 is specifically as follows: First, a water phase is prepared: sodium dodecyl sulfate is added into deionized water and is completely dissolved; then, an oil phase is prepared: the spiropyran compound prepared in step 1 is dissolved in butyl stearate, then the shell monomer is added drop by drop, and the solution is put into a cell crusher for reaction until the solution presents a transparent light purple color; The prepared oil phase is added into the water phase, stirring is performed at a speed of 2000-2500 rpm for 15-20 min, then the cell crusher is used for intermittent ultrasonic treatment for 5-8 min to form a light purple turbid solution, an initiator is added into the turbid solution, and reaction is performed at 80-90 DEG C for 6-8 h to obtain the photochromic microcapsule dispersion liquid.

[0011] The mass ratio of the spiropyran compound, butyl stearate and the shell monomer is 1:20-80:20-80; The mass ratio of sodium dodecyl sulfate to the spiropyran compound is 1:2.5; The initiator is azobisisobutyronitrile, and the mass of the initiator is 0.1%-0.2% of the mass of the turbid solution.

[0012] In step 3, the mass percentage of the silicone-modified polyurethane dispersion in the diluted solution is 20wt%.

[0013] Step 4 is specifically: The polyether polyol is dehydrated, and then reacted with a hydrophilic monomer, a silicone modifier, an organotin catalyst, a diisocyanate at 70-85℃ for 1-6h to obtain a polyurethane prepolymer. After the temperature of the reaction system is reduced to 40℃, a chain extender and a neutralizing agent are added and the reaction is continued for 0.5-1h. Then water is added to the system and stirred rapidly for 0.5h-1h to obtain a silicone-modified polyurethane dispersion.

[0014] The polyether polyol is one of polyoxypropylene polyol, polytetrahydrofuran ether polyol, polyethylene glycol monododecyl ether, perfluoro polyether alcohol, and tetrapolyethylene glycol monooctyl ether; The hydrophilic monomer is one of 1,2-dihydroxy-3-propanesulfonic acid sodium, 2,2-dimethylol propionic acid, 2,2-dimethylol butyric acid, tartaric acid, and diethanolamine; The silicone modifier is one of monohydroxyl-terminated polydimethylsiloxane, polydimethylsiloxane hydroxyl-terminated, gamma-aminopropyl triethoxysilane, and triethoxysilane; The organotin catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, and stannous octoate; The diisocyanate is at least one of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, toluene diisocyanate, and lysine diisocyanate; The chain extender is one of 1,4-butanediol, trimethylolpropane, ethylenediamine, glycerol, diethylaminoethanol, and diethanolamine; The neutralizing agent is one of triethylamine, dimethylethanolamine, sodium hydroxide, and potassium hydroxide; The molar ratio of each substance is: polyether polyol: hydrophilic monomer: silicone modifier: diisocyanate: chain extender: neutralizing agent is 18-24:4-7:2-7:0.05-0.1:3-6:2-7; The amount of the organotin catalyst added is 0.01%-0.5% of the total mass of the reactants; and the amount of water added is 60%-80% of the total mass of the entire system.

[0015] The conductive material is one of the following: ionic liquid, lithium salt, low eutectic solvent, MXene, metal-based material, conductive polymer, and carbon-based material. The amount of conductive material added is 30% of the mass of the organosilicon-modified polyurethane dispersion.

[0016] Another technical solution adopted in this invention is a photochromic fabric sensor, which is prepared by the above method.

[0017] The beneficial effects of this invention are: (1) The method of the present invention combines photochromism with sensing performance. The fabric sensor prepared can not only judge the changes of ultraviolet rays in the environment by color change, avoiding long-term exposure to ultraviolet rays and causing damage, but also monitor human movement. (2) The fabric sensor of the present invention uses spiropyran photochromic microcapsules as the color-changing component. The fabric and photochromic microcapsules are firmly bonded by the adhesion of organosilicon-modified waterborne polyurethane. The fabric sensor prepared has excellent ultraviolet response, as well as excellent hydrophobicity and excellent sensing performance. (3) The fabric sensor prepared by the method of the present invention is comfortable and soft, and the preparation process is simple, the production cost is low, and it can be mass-produced. Attached Figure Description

[0018] Figure 1 The infrared spectra of the spiropyran compound and photochromic microcapsules prepared in Example 1 of this invention are shown below. Figure 2 These are the ultraviolet spectra of the photochromic microcapsules prepared in Example 1 of this invention before and after ultraviolet light irradiation; Figure 3 The graph shows the mechanical property test results of the organosilicon-modified polyurethane prepared in Example 1 of this invention. Figure 4 This is the infrared spectrum of the organosilicon-modified polyurethane prepared in Example 1 of this invention; Figure 5 The resistance ΔR / R0 of the photochromic fabric sensor prepared in Example 1 of this invention is measured at different bending angles. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] The photochromic fabric sensor of this invention has two characteristics: photochromism and sensing performance. The sensor with the above two characteristics is mainly achieved through two steps. The first step is to introduce photochromic microcapsules on the surface of the fabric, and the second step is to spray a blended dispersion of organosilicon-modified waterborne polyurethane and conductive material.

[0021] The method for preparing the photochromic fabric sensor of the present invention is specifically implemented according to the following steps: Step 1 involves the aldol condensation reaction of salicylaldehyde and indole with piperidine as a catalyst to prepare a spiropyran compound. Specifically: Salicylic aldehyde and indole in a molar ratio of 1:1 were added to a three-necked round-bottom flask, and ethanol was added as a solvent. A transparent solution was formed under magnetic stirring at 300-400 rpm. Piperidine was then slowly added dropwise as a catalyst to the system. After the system was mixed evenly, the temperature was raised to 80-90℃ and the reaction was carried out for 3-4 hours. Polymerization was carried out by aldol condensation. The reaction product was then filtered and dried to obtain the spiropyran compound.

[0022] The prepared spiropyran compound is one of 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, 1-nitro-3,3-dimethylindoline-6'-nitrobenzospiropyran, 1-hydroxy-3,3-dimethylindoline-6'-nitrobenzospiropyran, and 1-methyl-3,3-dimethylindoline-6'-nitrobenzospiropyran, preferably 1-methyl-3,3-dimethylindoline-6'-nitrobenzospiropyran.

[0023] Step 2: The spiropyran compound obtained in Step 1 is encapsulated using a fine emulsion polymerization method to prepare a photochromic microcapsule dispersion. Specifically: First, prepare the aqueous phase: Add sodium dodecyl sulfate (SDS) to deionized water and sonicate until completely dissolved, then set aside. Next, prepare the oil phase: Dissolve the spiropyran compound prepared in step 1 in butyl stearate, then add the shell monomer dropwise and react in a cell disruptor until the solution becomes a transparent pale purple. The mass ratio of spiropyran compound, butyl stearate, and shell monomer is 1:20-80:20-80.

[0024] The prepared oil phase was added to the aqueous phase, wherein the mass ratio of sodium dodecyl sulfate to spiropyran compound was 1:2.5. The mixture was mechanically stirred at 2000-2500 rpm for 15-20 min, and then intermittently sonicated for 5-8 min using a cell disruptor to form a light purple turbid solution. Azobisisobutyronitrile (AIBN) initiator was added to the turbid solution at a mass of 0.1%-0.2% of the solution mass, and the mixture was reacted at 80-90℃ for 6-8 h to obtain a photochromic microcapsule dispersion. The shell material of the prepared photochromic microcapsules is one of polymethyl methacrylate, chitosan, silica, gelatin, polyethylene, and carboxymethyl cellulose.

[0025] Step 3: Dilute the photochromic microcapsule dispersion obtained in Step 2 with water to obtain a diluted solution with a concentration of 20wt%. Then, immerse the fabric in the diluted solution to prepare the photochromic fabric. Step 4: Dehydrate the polyether polyol under vacuum at 100-120℃ for 1-3 hours. Then, react the dehydrated polyether polyol with hydrophilic monomers, organosilicon modifiers, organotin catalysts, and diisocyanates at 70-85℃ for 1-6 hours to obtain a polyurethane prepolymer. After the reaction system temperature drops to 40℃, add chain extenders and neutralizers, and react for another 0.5-1 hour. Then, add water at 60%-80% of the total mass of the system and stir rapidly for 0.5-1 hour to obtain an organosilicon-modified polyurethane dispersion.

[0026] The molar ratios of the substances are as follows: The polyether polyol: hydrophilic monomer: organosilicon modifier: diisocyanate: chain extender: neutralizer is 18-24:4-7:2-7:0.05-0.1:3-6:2-7.

[0027] In addition, the amount of organotin catalyst added is 0.01%-0.5% of the total mass of the reactants.

[0028] The polyether polyol is one of polyoxypropylene polyol, polytetrahydrofuran ether polyol, polyethylene glycol monododecyl ether, perfluoropolyether alcohol, and tetraethylene glycol monooctyl ether.

[0029] The hydrophilic monomer is one of sodium 1,2-dihydroxy-3-propanesulfonate, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, tartaric acid, and diethanolamine, preferably 2,2-dimethylolbutyric acid.

[0030] The organosilicon modifier is one of the following: single-terminated dihydroxyl polydimethylsiloxane, polydimethylsiloxane hydroxyl-terminated, γ-aminopropyltriethoxysilane, and triethoxysilane.

[0031] The organotin catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, and stannous octoate, with dibutyltin dilaurate being preferred.

[0032] The diisocyanate is at least one of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, toluene diisocyanate, and lysine diisocyanate.

[0033] The chain extender is one of 1,4-butanediol, trimethylolpropane, ethylenediamine, glycerol, diethylaminoethanol, and diethanolamine.

[0034] The neutralizing agent is one of triethylamine, dimethylethanolamine, sodium hydroxide, or potassium hydroxide.

[0035] Step 5: Mix the silicone-modified polyurethane dispersion obtained in step 4 with the conductive material, and then spray it onto the surface of the photochromic fabric obtained in step 3 to obtain the photochromic fabric sensor.

[0036] The conductive material is one of the following: ionic liquid, lithium salt, low eutectic solvent, MXene, metal-based material, conductive polymer, and carbon-based material. The amount of conductive material added is 30% of the mass of the organosilicon-modified polyurethane dispersion.

[0037] Example 1 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: Take 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole and add them to a three-necked round-bottom flask. Then add ethanol as a solvent and form a transparent solution under magnetic stirring at 300rpm. Then slowly add piperidine as a catalyst to the system. After the system is mixed evenly, react at 80℃ for 4h to polymerize by aldol condensation. Then filter the reaction product, dry it, and obtain the spiropyran compound. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to completely dissolve it. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 4g of butyl stearate. Add this solution to a beaker, then add 4g of methyl methacrylate monomer dropwise. Place the mixture in a cell disruptor and react until the solution turns a transparent light purple color. Add the oil phase to the three-necked flask and mechanically stir at 2000rpm for 15min. Then, sonicate intermittently for 5min using a cell disruptor to form a light purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 80℃ for 8h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate the polytetrahydrofuran ether polyol under vacuum at 120℃ for 2 hours and set aside. Add 4g of polytetrahydrofuran ether polyol, 4.4g of isophorone diisocyanate, 0.68g of 2,2-dimethylolbutyric acid, 200μL of dibutyltin dilaurate, and 0.46g of mono-dihydroxyl polydimethylsiloxane to a three-necked flask and react at 80℃ for 5 hours. After lowering the temperature to 40℃, introduce 0.72g of 1,4-butanediol and 0.46g of triethylamine into the system and react for 1 hour. Then add 35mL of water to the system and stir rapidly for 30 minutes to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

[0038] The spiropyran compound SP prepared in this example and the photochromic microcapsules SP@PMMA were dried in an oven at 40°C, and the following properties were tested: (1) Infrared test: First, potassium bromide (KBr) was baked at 100℃ for 2 hours. Then, the sample to be tested and KBr were pressed into a pellet at a certain ratio, and the wavelength was recorded at 4000-500 cm⁻¹. -1 Infrared spectrum within the range; (2) Ultraviolet-visible spectroscopy test: Take a certain amount of solution and place it in a quartz cuvette for testing, and record the ultraviolet absorption spectrum of 800-400 nm.

[0039] Figure 1 The infrared spectra of the spiropyran compound SP and the photochromic microcapsules SP@PMMA prepared in this embodiment show that, in the infrared spectrum of SP, the 1089 cm⁻¹... -1 The absorption peak at 1605 cm⁻¹ corresponds to the stretching vibration of -COC-. -1 and 1508cm -1 The characteristic peaks at 1750 cm⁻¹ are caused by the stretching vibrations of the -NO₂ group, and the presence of these characteristic peaks confirms the successful preparation of SP. Meanwhile, the peak at 1750 cm⁻¹... -1 and 1150cm -1 The absorption peak at the specified position is due to the stretching vibration of the ester group, and the presence of this group proves the successful preparation of PMMA. Comparison of the infrared spectra of SP and SP@PMMA shows that the complete disappearance of the characteristic peak indicates that the spiropyran molecule has been completely encapsulated by PMMA, successfully preparing microcapsules with photochromic properties.

[0040] Figure 2 The image shows the ultraviolet spectrum of the photochromic microcapsule SP@PMMA prepared in this embodiment (SP@PMMA becomes MC@PMMA after being irradiated with ultraviolet light). It can be seen that the ultraviolet absorption peak of the photochromic microcapsule is 550 nm, and it can undergo isomerization and ring opening in this wavelength range.

[0041] The silicone-modified polyurethane dispersion prepared in this embodiment was film-formed in a polytetrafluoroethylene mold and cured in a 40°C oven. After curing, the following properties were tested: (1) Mechanical properties: Tensile strength and elongation at break were tested according to the test methods provided in GB / T1040 "Determination of tensile properties of plastics". The results are as follows: Figure 3 As shown, its tensile strength and elongation at break were measured to be 6 MPa and 380%, respectively.

[0042] (2) Infrared test: First, test the background infrared spectrum to eliminate the influence of moisture in the air on the experiment. Then, put the dry film of organosilicon modified polyurethane into the Fourier transform infrared spectrometer and record its infrared spectrum data.

[0043] Test results are as follows Figure 4 As shown, it can be seen that at 3319cm -1 The strong NH absorption peak at 1706 cm⁻¹ and the strong absorption peak at 1706 cm� -1 The C=O stretching vibration at 1020 cm⁻¹ confirms the presence of the urethane bond group (-NHCOO-), indicating the successful synthesis of the polyurethane backbone. The modified Si-WPU exhibits a stretching vibration at 1020 cm⁻¹. -1 The presence of a significant Si-O-Si stretching vibration peak indicates that the modifier has been grafted into the polyurethane skeleton.

[0044] The sensor prepared in this embodiment was attached to the knuckle, and both ends of the sample were fixed with copper foil tape. Simultaneously, the wires at both ends of the sensor were connected to a digital power meter, and its resistance ΔR / R0 was measured at different bending angles. The results are as follows. Figure 5 As shown, the sensor exhibits different resistance changes at three different bending angles (30°, 60°, and 90°), with the largest resistance change observed at a bending angle of 90°. This indicates that the fabric-based sensor of this embodiment can be used to monitor the activity of human joints.

[0045] Example 2 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: Take 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole and add them to a three-necked round-bottom flask. Add ethanol as a solvent and form a transparent solution under magnetic stirring at 400rpm. Then, slowly add piperidine as a catalyst to the system. After the system is mixed evenly, react at 90℃ for 3h to polymerize by aldol condensation. Then filter the reaction product, dry it, and obtain the spiropyran compound. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to completely dissolve it. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 4g of butyl stearate. Add this solution to a beaker, then add 8g of methyl methacrylate monomer dropwise. Place the mixture in a cell disruptor and react until the solution turns a transparent light purple color. Add the oil phase to the three-necked flask and mechanically stir at 2500rpm for 15min. Then, use a cell disruptor to intermittently sonicate for 5min to form a light purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 90℃ for 6h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate polyethylene glycol monododecyl ether under vacuum at 110℃ for 2 hours and set aside. Add 4g polyethylene glycol monododecyl ether, 4.4g isophorone diisocyanate, 0.68g 2,2-dimethylolbutyric acid, 200μL dibutyltin dilaurate, and 0.91g monodihydroxyl-terminated polydimethylsiloxane to a three-necked flask and react at 85℃ for 5 hours. After lowering the temperature to 40℃, introduce 0.72g 1,4-butanediol and 0.46g triethylamine into the system and react for 1 hour. Then add 36mL of water to the system and stir rapidly for 1 hour to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

[0046] Example 3 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole were added to a three-necked round-bottom flask, and ethanol was added as a solvent. A transparent solution was formed under magnetic stirring at 300rpm. Piperidine was then slowly added dropwise to the system as a catalyst. After the system was mixed evenly, it was reacted at 80℃ for 3.5h to polymerize via aldol condensation. The reaction product was then filtered, dried, and the spiropyran compound was obtained. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to ensure complete dissolution. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 4g of butyl stearate. Add this to a beaker, then add 16g of methyl methacrylate monomer dropwise. React the mixture in a cell disruptor until the solution turns a transparent pale purple. Add the oil phase to the three-necked flask and mechanically stir at 2000rpm for 20min. Then, sonicate intermittently for 8min using a cell disruptor to form a pale purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 80℃ for 7h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate the perfluoropolyether alcohol under vacuum at 120℃ for 3 hours and set aside. Add 4g of perfluoropolyether alcohol, 4.4g of isophorone diisocyanate, 0.68g of 2,2-dimethylolbutyric acid, 200μL of dibutyltin dilaurate, and 1.36g of monohydroxyl-terminated polydimethylsiloxane to a three-necked flask and react at 70℃ for 6 hours. After lowering the temperature to 40℃, introduce 0.72g of 1,4-butanediol and 0.46g of triethylamine into the system and react for 1 hour. Then add 37mL of water to the system and stir rapidly for 30 minutes to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

[0047] Example 4 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole were added to a three-necked round-bottom flask, and ethanol was added as a solvent. A transparent solution was formed under magnetic stirring at 350rpm. Piperidine was then slowly added dropwise to the system as a catalyst. After the system was mixed evenly, it was reacted at 85℃ for 4h to polymerize via aldol condensation. The reaction product was then filtered, dried, and the spiropyran compound was obtained. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to completely dissolve it. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 8g of butyl stearate. Add this solution to a beaker, then add 4g of methyl methacrylate monomer dropwise. Place the mixture in a cell disruptor and react until the solution turns a transparent light purple color. Add the oil phase to the three-necked flask and mechanically stir at 2200rpm for 15min. Then, use a cell disruptor to intermittently sonicate for 5min to form a light purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 85℃ for 7h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate the polytetrahydrofuran ether polyol under vacuum at 120℃ for 2 hours and set aside. Add 4g of polytetrahydrofuran ether polyol, 4.4g of isophorone diisocyanate, 0.68g of 2,2-dimethylolbutyric acid, 200μL of dibutyltin dilaurate, and 1.82g of mono-dihydroxyl-terminated polydimethylsiloxane to a three-necked flask and react at 75℃ for 2 hours. After lowering the temperature to 40℃, introduce 0.72g of 1,4-butanediol and 0.46g of triethylamine into the system and react for 0.5 hours. Then add 38mL of water to the system and stir rapidly for 30 minutes to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

[0048] Example 5 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: Take 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole and add them to a three-necked round-bottom flask. Add ethanol as a solvent and form a transparent solution under magnetic stirring at 350rpm. Then, slowly add piperidine as a catalyst to the system. After the system is mixed evenly, react at 80℃ for 4h to polymerize by aldol condensation. Then filter the reaction product, dry it, and obtain the spiropyran compound. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to completely dissolve it. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 16g of butyl stearate. Add this solution to a beaker, then add 4g of methyl methacrylate monomer dropwise. Place the mixture in a cell disruptor and react until the solution turns a transparent light purple color. Add the oil phase to the three-necked flask and mechanically stir at 2000rpm for 20min. Then, sonicate intermittently for 6min using a cell disruptor to form a light purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 80℃ for 6h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate the polytetrahydrofuran ether polyol under vacuum at 120℃ for 2 hours and set aside. Add 4g of polytetrahydrofuran ether polyol, 4.4g of isophorone diisocyanate, 0.68g of 2,2-dimethylolbutyric acid, 200μL of dibutyltin dilaurate, and 2.27g of mono-dihydroxyl-terminated polydimethylsiloxane to a three-necked flask and react at 80℃ for 2 hours. After lowering the temperature to 40℃, introduce 0.72g of 1,4-butanediol and 0.46g of triethylamine into the system and react for 1 hour. Then add 39mL of water to the system and stir rapidly for 30 minutes to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

[0049] Example 6 The method for preparing the photochromic fabric sensor in this embodiment includes the following steps: Step 1: 2g of 5-nitrosalicylic acid and 2.07g of 1,3,3-trimethyl-2-methyleneindole were added to a three-necked round-bottom flask, and ethanol was added as a solvent. A transparent solution was formed under magnetic stirring at 350rpm. Piperidine was then slowly added dropwise to the system as a catalyst. After the system was mixed evenly, it was reacted at 85℃ for 3.5h to polymerize via aldol condensation. The reaction product was then filtered, dried, and the spiropyran compound was obtained. Step 2: First, prepare the aqueous phase: Weigh 0.08g of sodium dodecyl sulfate and add it to 60mL of deionized water. Then, add this solution to a three-necked flask and sonicate for 20min to completely dissolve it. Set aside. Next, prepare the oil phase: Weigh 0.2g of spiropyran compound and dissolve it in 4g of butyl stearate. Add this solution to a beaker, then add 4g of methyl methacrylate monomer dropwise. Place the mixture in a cell disruptor and react until the solution turns a transparent light purple color. Add the oil phase to the three-necked flask and mechanically stir at 2000rpm for 20min. Then, use a cell disruptor to intermittently sonicate for 6min to form a light purple turbid solution. Add 0.1g of azobisisobutyronitrile initiator to this turbid solution and react at 80℃ for 6h to obtain a photochromic microcapsule dispersion. Step 3: Add the above dispersion to water to prepare a 20wt% dilution, immerse the fabric in the dilution, and prepare a photochromic fabric. Step 4: Dehydrate the polytetrahydrofuran ether polyol under vacuum at 120℃ for 1 hour and set aside. Add 4g of polytetrahydrofuran ether polyol, 4.4g of isophorone diisocyanate, 0.68g of 2,2-dimethylolbutyric acid, 200μL of dibutyltin dilaurate, and 2.27g of mono-dihydroxyl-terminated polydimethylsiloxane to a three-necked flask and react at 80℃ for 4 hours. After lowering the temperature to 40℃, introduce 0.72g of 1,4-butanediol and 0.46g of triethylamine into the system and react for 0.5 hours. Then add 40mL of water to the system and stir rapidly for 1 hour to obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the ionic liquid and spray it onto the surface of the photochromic fabric to prepare the photochromic fabric sensor.

Claims

1. A method for fabricating a photochromic fabric sensor, characterized in that, Specifically: Step 1: Prepare spiropyran compounds using salicylaldehyde and indole; Step 2: Encapsulate the spiropyran compound using a fine emulsion polymerization method to obtain a photochromic microcapsule dispersion; Step 3: After diluting the photochromic microcapsule dispersion, immerse the fabric in it. A photochromic fabric was obtained; Step 4: Dehydrate the polyether polyol, then react it with hydrophilic monomers, organosilicon modifiers, organotin catalysts, and diisocyanates to obtain a polyurethane prepolymer. Then add chain extenders and neutralizers to continue the reaction and obtain an organosilicon-modified polyurethane dispersion. Step 5: Mix the silicone-modified polyurethane dispersion with the conductive material and then spray it onto the surface of the photochromic fabric to obtain the photochromic fabric sensor.

2. The method for preparing the photochromic fabric sensor according to claim 1, characterized in that, Step 1 is as follows: Salicylic aldehyde and indole in a molar ratio of 1:1 were added to ethanol and stirred to form a transparent solution. Then, piperidine was slowly added dropwise as a catalyst. After the system was mixed evenly, the temperature was raised to 80-90℃ and reacted for 3-4 hours. Polymerization was carried out by aldol condensation. The reaction product was then filtered and dried to obtain the spiropyran compound.

3. The method for preparing a photochromic fabric sensor according to claim 1 or 2, characterized in that, The spiropyran compound is one of 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran, 1-nitro-3,3-dimethylindoline-6'-nitrobenzospiropyran, 1-hydroxy-3,3-dimethylindoline-6'-nitrobenzospiropyran, and 1-methyl-3,3-dimethylindoline-6'-nitrobenzospiropyran.

4. The method for preparing a photochromic fabric sensor according to claim 1, characterized in that, Step 2 is as follows: First, prepare the aqueous phase: add sodium dodecyl sulfate to deionized water and dissolve it completely; then prepare the oil phase: dissolve the spiropyran compound prepared in step 1 in butyl stearate, then add the shell monomer dropwise, and place it in a cell disruptor to react until the solution turns a transparent light purple. The prepared oil phase is added to the aqueous phase and stirred at 2000-2500 rpm for 15-20 min. Then, the mixture is intermittently sonicated for 5-8 min using a cell disruptor to form a light purple turbid solution. An initiator is added to the turbid solution and the mixture is reacted at 80-90℃ for 6-8 h to obtain a photochromic microcapsule dispersion.

5. The method for preparing a photochromic fabric sensor according to claim 4, characterized in that, The mass ratio of the spiropyran compound, butyl stearate, and shell monomer is 1:20-80:20-80; The mass ratio of sodium dodecyl sulfate to spiropyran compound is 1:2.5; The initiator is azobisisobutyronitrile, and its mass is 0.1%-0.2% of the mass of the turbid solution.

6. The method for preparing a photochromic fabric sensor according to claim 1, characterized in that, In step 3, the mass percentage of the organosilicon-modified polyurethane dispersion in the diluted solution is 20 wt%.

7. The method for preparing a photochromic fabric sensor according to claim 1, characterized in that, Step 4 specifically involves: The polyether polyol is dehydrated and then reacted with a hydrophilic monomer, an organosilicon modifier, an organotin catalyst, and a diisocyanate at 70-85℃ for 1-6 hours to obtain a polyurethane prepolymer. After the temperature of the reaction system is reduced to 40℃, a chain extender and a neutralizing agent are added and the reaction continues for 0.5-1 hours. Then, water is added to the system and the mixture is stirred rapidly for 0.5-1 hours to obtain an organosilicon-modified polyurethane dispersion.

8. The method for preparing a photochromic fabric sensor according to claim 1 or 7, characterized in that, The polyether polyol is one of polyoxypropylene polyol, polytetrahydrofuran ether polyol, polyethylene glycol monododecyl ether, perfluoropolyether alcohol, and polyethylene glycol monooctyl ether. The hydrophilic monomer is one of sodium 1,2-dihydroxy-3-propanesulfonate, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, tartaric acid, and diethanolamine. The organosilicon modifier is one of the following: single-terminated dihydroxyl polydimethylsiloxane, polydimethylsiloxane hydroxyl-terminated, γ-aminopropyltriethoxysilane, and triethoxysilane. The organotin catalyst is one of dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, and stannous octoate. The diisocyanate is at least one of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, toluene diisocyanate, and lysine diisocyanate; The chain extender is one of 1,4-butanediol, trimethylolpropane, ethylenediamine, glycerol, diethylaminoethanol, and diethanolamine; The neutralizing agent is one of triethylamine, dimethylethanolamine, sodium hydroxide, and potassium hydroxide; The molar ratio of each substance is: polyether polyol: hydrophilic monomer: organosilicon modifier: diisocyanate: chain extender: neutralizer is 18-24:4-7:2-7:0.05-0.1:3-6:2-7; The amount of organotin catalyst added is 0.01%-0.5% of the total mass of the reactants; the amount of water added is 60%-80% of the total mass of the whole system.

9. The method for preparing a photochromic fabric sensor according to claim 1, characterized in that, The conductive material is one of the following: ionic liquid, lithium salt, low eutectic solvent, MXene, metal-based material, conductive polymer, and carbon-based material. The amount of conductive material added is 30% of the mass of the organosilicon-modified polyurethane dispersion.

10. A photochromic fabric sensor, characterized in that, It is prepared by the method described in any one of claims 1-9.

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