Environmental response type hydrogel as well as preparation method and application thereof

Abstract

The invention discloses environment response type hydrogel and a preparation method and application thereof, and belongs to the technical field of intelligent hydrogel and microchannel control. Stimuli response type hydrogel monomers and a water-phase dispersing agent are used as raw materials, a linear molecular chain is formed under the action of a free radical thermal initiator, and then the environment response type hydrogel is prepared. After the water-phase dispersing agent generates free radicals, graft polymerization is carried out on molecules of the stimuli-responsive hydrogel monomer under the action of the cross-linking agent, in the polymerization process, carbon-carbon double bonds of the cross-linking agent are broken and react with the water-phase dispersing agent and the stimuli-responsive hydrogel monomer, a cross-linked structure is formed, and the environment-responsive hydrogel is obtained. The environment response type hydrogel prepared by the invention has a tri-crosslinked network structure, has a pH and temperature dual-response function, is high in response speed and high in accuracy, and shows hysteresis in the response process.

Description

Technical Field

[0001] The present invention relates to the field of intelligent hydrogel and microchannel control technology, and in particular to an environmentally responsive hydrogel and a preparation method and application thereof. Background Art

[0002] A microvalve is a miniaturized modern valve that works in the same way as a conventional valve, mainly by adjusting the on-off and flow rate of the fluid medium through a switch action. In recent years, environmentally responsive hydrogel microvalves have been widely used in many fields such as microfluidic control, portable diagnosis, and controlled drug release.

[0003] Environmentally responsive hydrogels can reversibly change size or shape under external stimuli such as temperature, pH, light, etc. The material properties of most stimuli-responsive hydrogels are one-to-one with the environmental stimulus signals, but some stimuli-responsive hydrogel materials show hysteresis in the response process. Under the same environmental stimulus signal, the hydrogel material will store the historical information of the previous environment and show different properties. This response hysteresis can allow information to be written, stored, and read, imitating electronic computing systems to perform operations such as sensing input signals, storing and processing information, and outputting readable signals.

[0004] At present, the prior art discloses a preparation method and application field of a class of thermosensitive and photosensitive environmental responsive hydrogels, and uses hydrogel as a microvalve, and the hydrogel makes a shape or size adjustment response according to external stimuli, so as to meet the corresponding flow control needs. However, the responsiveness function of the above-mentioned hydrogel is associated with external stimuli, and there is a response only when there is external information input. Once the stimulus disappears, the response disappears therewith, and the response behavior (such as shape memory) generated based on the external stimulus cannot be maintained continuously, so that the purpose of efficiently controlling the flow of fluid cannot be achieved by controlling the switch of the microvalve; in addition, the response hysteresis of the hydrogel refers to the reaction time of the hydrogel to external stimuli. There is a certain delay, and this characteristic makes the hydrogel reach a swelling or shrinking state after being stimulated for a certain period of time, so this delay can be used to accurately control the flow of the fluid. However, the existing hydrogel has a hysteresis instability problem after the stimulus response, that is, after the hydrogel is stimulated by the external stimulus, its reaction time is delayed, and the reaction degree is uncertain, resulting in poor accuracy of fluid flow control. Summary of the invention

[0005] The present invention provides an environmentally responsive hydrogel and a preparation method and application thereof, which effectively solve the technical problems that the current hydrogel response is closely related to the stimulus, the response behavior cannot be maintained continuously alone, and the response hysteresis of the hydrogel is unstable. At the same time, a heterogeneous hydrogel with excellent mechanical properties and multi-solvent responsiveness is provided, and the hydrogel is applied to a driver intelligent microvalve to realize intelligent control integrating sensing input signals, intelligent memory analysis, and output driving behavior.

[0006] The first object of the present invention is to provide a method for preparing an environmentally responsive hydrogel, comprising the following steps:

[0007] The photothermal conversion material is added into the aqueous solution of the aqueous phase dispersant and dispersed to obtain a photothermal conversion material suspension.

[0008] Add a stimulus-responsive hydrogel monomer to the photothermal conversion material suspension, dissolve it, add a free radical thermal initiator and a cross-linking agent, stir, cool, and then add a promoter initiator to carry out a polymerization reaction in a nitrogen atmosphere. During the polymerization process, the carbon-carbon double bond of the cross-linking agent is broken, and it reacts with the aqueous phase dispersant and the stimulus-responsive hydrogel monomer under the action of the free radical thermal initiator and the promoter initiator to form a cross-linked structure, and then the photothermal conversion material is loaded in the cross-linked structure to obtain an environmentally responsive hydrogel.

[0009] As a preferred embodiment, the mass concentration of the aqueous solution of the aqueous phase dispersant is 5 mg / mL, and the mass ratio of the photothermal conversion material to the aqueous solution of the aqueous phase dispersant is 5-9:325-450.

[0010] As a preferred embodiment, the mass ratio of the stimulus responsive hydrogel monomer to the photothermal conversion material is 40-60:5-9.

[0011] As a preferred embodiment, the mass ratio of the free radical thermal initiator, the crosslinking agent and the accelerator is 10-15:5-10:15-20.

[0012] As a preferred embodiment, the stimulus-responsive hydrogel monomer is one or more of N-isopropylacrylamide, acrylic acid, N-propylacrylamide or sodium alginate.

[0013] As a preferred embodiment, the photothermal conversion material is one or more of carbon nanotubes, silver nanowires, and carbon black.

[0014] As a preferred embodiment, the free radical thermal initiator is one or more of ammonium persulfate, azobisisobutyronitrile, and diacyl peroxide; the crosslinking agent is one or more of N,N-methylenebisacrylamide, diisopropylbenzene peroxide, butadiene, and vinylbenzene; and the accelerator is one or more of N,N,N',N'-tetramethylethylenediamine, propylenediamine, and isopropylenediamine.

[0015] The second object of the present invention is to provide an environmentally responsive hydrogel prepared by the above preparation method.

[0016] The third object of the present invention is to provide an application of the above-mentioned environmentally responsive hydrogel in an actuator intelligent microvalve.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention uses stimulus-responsive hydrogel monomers, aqueous phase dispersants, photothermal conversion materials, free radical thermal initiators, crosslinkers and pro-initiators as raw materials to construct a heterogeneous environmental responsive hydrogel with excellent mechanical properties and multi-solvent responsiveness. The present invention uses stimulus-responsive hydrogel monomers and aqueous phase dispersants as raw materials, and forms linear molecular chains under the action of free radical thermal initiators. After the aqueous phase dispersants generate free radicals, they are grafted and polymerized on stimulus-responsive hydrogel monomer molecules due to the action of crosslinkers. During the polymerization process, the carbon-carbon double bonds of the crosslinkers are broken, and the aqueous phase dispersants and stimulus-responsive hydrogel monomers react to form a crosslinked structure, and then the photothermal conversion material is loaded in the crosslinked structure to obtain an environmental responsive hydrogel. The environmental responsive hydrogel prepared by the present invention is applied to a microvalve, which has a response independent maintenance function and a response hysteresis. When an external stimulus acts on the hydrogel, the microvalve is in a closed state when the volume of the hydrogel expands to a certain extent, and the liquid cannot flow; or when the volume of the hydrogel shrinks to a certain extent, the microvalve is opened and the liquid circulates. In application, the microvalve can realize three states of normally open, normally closed and conversion between open and closed under the condition of the same temperature and only changing the pH value. It has dual response function of pH and temperature, fast response speed and high precision, and at the same time it will show hysteresis stability in the response process.

[0019] Since the microvalve control system needs to memorize and analyze the historical information of the environment, and make intelligent judgments and controls on this basis, the environment-responsive hydrogel prepared by the present invention is applied to the driver intelligent microvalve. Since the hydrogel has a response hysteresis, and this response hysteresis can allow writing, storage and reading of information, imitating the electronic computing system to perform operations such as sensing input signals, storing and processing information, and outputting readable signals, the environment-responsive hydrogel of the present invention can realize intelligent hydrogel microvalve control that integrates sensing input signals, intelligent memory analysis, and output driving behavior, so that it can store the previous environmental historical information and exhibit different properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the application of the environmentally responsive hydrogel of the present invention in the actuator intelligent microvalve.

[0021] Figure 2 This is a diagram of the synthesis mechanism of the environmentally responsive hydrogel of the present invention.

[0022] Figure 3 Schematic diagram of the plastic model of the driver intelligent microvalve of the present invention; wherein (a) is the left view and (b) is the right view.

[0023] Figure 4 This is a working state diagram of the environmentally responsive hydrogel of the present invention in an actuator intelligent microvalve at 45°C and pH values ​​of 4, 5 and 6.5, respectively. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the reagents and raw materials, unless otherwise specified, are commercially available.

[0025] Regarding the background technology mentioned in the present invention: In recent years, environmentally responsive hydrogel microvalves have been widely used in many fields such as microfluidic control, portable diagnosis and controlled drug release. Hydrogels are used as microvalves and respond according to external stimuli to meet corresponding regulation needs. However, the responsiveness function of microvalves prepared using existing hydrogels is related to external stimuli. There is a response only when there is external information input, and the response cannot be maintained continuously alone; the measurement time of the hydrogel hysteresis is too fast, the hydrogel system has not reached or is close to the equilibrium steady state, and the hydrogel hysteresis is unstable. Based on the above technical problems, the present invention provides an environmentally responsive hydrogel and its preparation method and application.

[0026] The technical solution of the present invention is analyzed and explained below.

[0027] The present invention provides a method for preparing the above-mentioned environmentally responsive hydrogel, comprising the following steps:

[0028] The photothermal conversion material is added into the aqueous solution of the aqueous phase dispersant and dispersed to obtain a photothermal conversion material suspension.

[0029] Add a stimulus-responsive hydrogel monomer to the photothermal conversion material suspension, dissolve it, add a free radical thermal initiator and a cross-linking agent, stir, cool, and then add a promoter initiator to carry out a polymerization reaction in a nitrogen atmosphere. During the polymerization process, the carbon-carbon double bond of the cross-linking agent is broken, and it reacts with the aqueous phase dispersant and the stimulus-responsive hydrogel monomer under the action of the free radical thermal initiator and the promoter initiator to form a cross-linked structure, and then the photothermal conversion material is loaded in the cross-linked structure to obtain an environmentally responsive hydrogel.

[0030] In the above-mentioned preparation method, the role of the free radical thermal initiator is to initiate the polymerization of free radicals by heat, and the stimulus-responsive hydrogel monomers form linear molecular chains under the action of the initiator. After the free radicals are generated, the aqueous phase dispersant molecules are branched and polymerized on the stimulus-responsive hydrogel monomer molecules due to the action of the crosslinking agent to form a crosslinked structure. The initiator reduces the thermal initiation temperature of the free radical thermal initiator to meet the polymerization requirement that the stimulus-responsive hydrogel monomers need to be polymerized at a lower temperature.

[0031] It should be noted that the mass concentration of the aqueous solution of the aqueous phase dispersant is 5 mg / mL, and the mass ratio of the aqueous solution of the photothermal conversion material to the aqueous phase dispersant is 5-9:325-450. The mass ratio of the stimulus-responsive hydrogel monomer to the photothermal conversion material is 40-60:5-9. Since the amount of photothermal conversion material used will affect the photothermal response rate of the hydrogel, if the proportion of the photothermal conversion material is too small, the hydrogel switch response rate of the hydrogel valve will be reduced, and the overall sensitivity of the intelligent microvalve will be reduced; at the same time, the more photothermal conversion materials, the better. The proportion of photothermal conversion materials has an upper limit on the conversion efficiency. At the same time, too much proportion of this material will affect the polymerization reaction. In addition, if the proportion of methylcellulose is too small, the association effect of the methylcellulose segment caused by the hydrophobic force will be reduced, thereby reducing the hydrophobic hysteresis of the hydrogel system. If the proportion of methylcellulose is too large, the concentration of other monomers will be reduced, affecting the critical solution temperature and pH response effect. Therefore, the dosage ratio of the photothermal conversion material claimed in the present invention can ensure that the environmentally responsive hydrogel prepared by the present invention has a faster photothermal conversion efficiency and will not have an adverse effect on the polymerization reaction of the system.

[0032] It should be noted that the concentration of the free radical thermal initiator is 10%wt, the concentration of the cross-linking agent is 2.5%wt, and the mass ratio of the free radical thermal initiator, the cross-linking agent and the accelerator is 5-15:5-10:15-20. The free radical thermal initiator will affect the polymerization reaction rate. A lower content of the free radical thermal initiator will reduce the polymerization reaction rate; a higher content of the free radical thermal initiator will produce more chain transfer, the polymer molecular weight will decrease, and the molecular weight distribution will become wider. Too little cross-linking agent will prevent the hydrogel network from forming a complete cross-linked structure, and the stability of the hydrogel polymer will deteriorate; too high a cross-linking agent content will cause too many cross-linking points in the polymer, forming a large number of cross-linked structures, resulting in an uneven polymer structure, affecting the volume change response of the hydrogel, and the swelling rate is too small, and microvalve regulation cannot be performed, which will also lead to an uneven polymer structure. The main function of the initiator is to lower the initiation temperature of the free radical thermal initiator, which meets the polymerization conditions of the stimulus-responsive hydrogel monomer. Therefore, a lower content of the initiator will result in a higher polymerization temperature, causing the stimulus-responsive hydrogel to lose its temperature response function; an excessive amount of the initiator will result in a too low polymerization temperature, making room temperature polymerization impossible, which increases the difficulty of the reaction.

[0033] The present invention also provides an environmentally responsive hydrogel, which is made of the following raw materials in parts by weight: 40 to 60 parts of a stimulus-responsive hydrogel monomer, 325 to 450 parts of an aqueous phase dispersant, 5 to 9 parts of a photothermal conversion material, 5 to 15 parts of a free radical thermal initiator, 5 to 10 parts of a cross-linking agent, and 15 to 20 parts of a catalytic initiator.

[0034] The stimulus-responsive hydrogel monomer is one or more of N-isopropylacrylamide, acrylic acid, N-propylacrylamide or sodium alginate. The photothermal conversion material is one or more of carbon nanotubes, silver nanowires, and carbon black. The free radical thermal initiator is one or more of ammonium persulfate, azobisisobutyronitrile, and diacyl peroxide; the crosslinker is one or more of N,N-methylenebisacrylamide, diisopropylbenzene peroxide, butadiene, and vinylbenzene; the initiator is one or more of N,N,N',N'-tetramethylethylenediamine, propylenediamine, and isopropylenediamine.

[0035] In the above technical solution, a heterogeneous environmental responsive hydrogel with excellent mechanical properties and multi-solvent responsiveness is constructed using stimulus responsive hydrogel monomers, aqueous phase dispersants, photothermal conversion materials, free radical thermal initiators, crosslinkers and pro-initiators as raw materials. The hydrogel has a three-crosslinked network structure and has dual response functions of pH and temperature, fast response speed, high precision, and hysteresis in the response process.

[0036] The present invention also provides an application of the above-mentioned environment-responsive hydrogel in an actuator intelligent microvalve, which specifically comprises the following steps:

[0037] Prepare pH buffer solution: prepare acetic acid-sodium acetate buffer solutions with a concentration of 0.01 mol / L, a pH value of 4 and a pH value of 4 respectively; prepare disodium hydrogen phosphate-sodium dihydrogen phosphate buffer solution with a concentration of 0.01 mol / L, a pH value of 6.5.

[0038] Build a plastic model of the actuator smart microvalve with dimensions such as Figure 3 As shown, the dimensions of the cavities are 16 mm × 17 mm × 15 mm and 16 mm × 16 mm × 15 mm, respectively, and the dimensions of the middle groove are 3 mm × 10 mm × 8 mm. A plastic mold for curing Ecoflex is printed using a 3D printer, and the shape is a U-shaped groove.

[0039] Preparation of Ecoflex film: After the U-shaped groove is soaked with isopropyl alcohol, the silicone rubber Ecoflex prepolymer solution is poured into the U-shaped groove, the excess liquid on the surface is scraped off, and after covering with a glass slide, it is cured in an oven at 60° C. for 1 hour to obtain a U-shaped Ecoflex hydrophobic film with a thickness of 200 mm.

[0040] Since the microvalve is switched on and off by hydrogel swelling and contraction, it is impossible for a simple hydrogel to fit perfectly or be properly controlled, and the switching process only has two points of control: on and off. Adding this hydrophobic film is an extension and supplement to the microvalve hydrogel switch. In addition to the functions of on and off, the microvalve can achieve different degrees of switching, thereby controlling the changes in different flow rates, and enhancing the precision and accuracy of hydrogel control.

[0041] The environmentally responsive hydrogel prepared by the present invention is used as the "switch" of the driver intelligent microvalve, and the driver intelligent microvalve model is the main body of the intelligent microvalve, such as Figure 3 shown.

[0042] The environmentally responsive hydrogel is placed in an actuator intelligent microvalve containing a U-shaped Ecoflex hydrophobic film. The environmental changes are used as input signals, and the expansion and contraction of the hydrogel are used as output signals. When the hydrogel expands, the microvalve is closed, and when the hydrogel contracts, the microvalve is opened.

[0043] The technical effects of the present invention are described below in conjunction with specific embodiments and comparative examples.

[0044] Example 1

[0045] An environmentally responsive hydrogel is composed of the following raw materials in parts by weight: 55 parts of stimulus-responsive hydrogel monomers (N-isopropylacrylamide and acrylic acid), 400 parts of an aqueous phase dispersant (methylcellulose), 6 parts of a photothermal conversion material (carbon nanotubes), 10 parts of a free radical thermal initiator (ammonium persulfate: APS), 7.5 parts of a crosslinking agent (N,N-methylenebisacrylamide: MBAA), and 20 parts of an initiator (N,N,N',N'-tetramethylethylenediamine: TMEDA).

[0046] The weight ratio of the above-mentioned N-isopropylacrylamide, acrylic acid, methylcellulose aqueous solution, CNT, APS aqueous solution, MBAA aqueous solution, and TMEDA is 50:5:400:6:10:7.5:20.

[0047] The method for preparing the above-mentioned environmentally responsive hydrogel comprises the following steps:

[0048] S1, adding carbon nanotubes into a methyl cellulose aqueous solution with a mass concentration of 5 mg / mL, ultrasonically dispersing for 5 minutes and stirring for 1 hour to obtain a uniformly dispersed photothermal conversion suspension.

[0049] S2, adding N-isopropylacrylamide and acrylic acid into the photothermal conversion material suspension and stirring for 2 hours, ultrasonically dispersing for 5 minutes and stirring for 20 minutes to fully dissolve.

[0050] S3, add 10%wt APS aqueous solution and 2.5%wt MBAA aqueous solution, continue stirring for 20min, then transfer to a 0℃ ice water bath, add TMEDA after the solution is cooled, continue stirring for 5min, pass nitrogen, and stand for 24h to obtain an environmentally responsive hydrogel. The reaction process is as follows: Figure 2 shown.

[0051] Example 2

[0052] An environmentally responsive hydrogel is composed of the following raw materials in parts by weight: 40 parts of stimulus-responsive hydrogel monomers (N-isopropylacrylamide and acrylic acid), 325 parts of an aqueous phase dispersant (methyl cellulose), 5 parts of a photothermal conversion material (carbon nanotubes), 5 parts of a free radical thermal initiator (ammonium persulfate), 5 parts of a crosslinking agent (N,N-methylenebisacrylamide), and 15 parts of a catalyzer (N,N,N',N'-tetramethylethylenediamine).

[0053] The weight ratio of the above-mentioned N-isopropylacrylamide, acrylic acid, methylcellulose aqueous solution, CNT, APS aqueous solution, MBAA aqueous solution, and TMEDA is 35:5:325:5:5:5:15.

[0054] The method for preparing the above-mentioned environmentally responsive hydrogel comprises the following steps:

[0055] S1, adding carbon nanotubes into a methyl cellulose aqueous solution with a mass concentration of 5 mg / mL, ultrasonically dispersing for 10 min and stirring for 2 h to obtain a uniformly dispersed photothermal conversion suspension.

[0056] S2, adding N-isopropylacrylamide and acrylic acid into the photothermal conversion material suspension and stirring for 2 hours, ultrasonically dispersing for 10 minutes and stirring for 30 minutes to fully dissolve.

[0057] S3, add an APS aqueous solution with a mass concentration of 10%wt and an MBAA aqueous solution with a mass concentration of 2.5%wt, continue stirring for 20 minutes, then transfer to a 0°C ice water bath, add TMEDA after the solution is cooled, continue stirring for 5 minutes, pass nitrogen, and let stand for 24 hours to obtain an environmentally responsive hydrogel.

[0058] Example 3

[0059] An environmentally responsive hydrogel is composed of the following raw materials in parts by weight: 60 parts of stimulus-responsive hydrogel monomers (N-isopropylacrylamide and acrylic acid), 450 parts of an aqueous phase dispersant (methyl cellulose), 9 parts of a photothermal conversion material (carbon nanotubes), 15 parts of a free radical thermal initiator (ammonium persulfate), 10 parts of a crosslinking agent (N,N-methylenebisacrylamide), and 18 parts of an initiator (N,N,N',N'-tetramethylethylenediamine).

[0060] The weight ratio of the above-mentioned N-isopropylacrylamide, acrylic acid, methylcellulose aqueous solution, CNT, APS aqueous solution, MBAA aqueous solution, and TMEDA is 55:5:450:9:15:10:18.

[0061] The method for preparing the above-mentioned environmentally responsive hydrogel comprises the following steps:

[0062] S1, adding carbon nanotubes into a methyl cellulose aqueous solution with a mass concentration of 5 mg / mL, ultrasonically dispersing for 8 minutes and stirring for 1.5 hours to obtain a uniformly dispersed photothermal conversion suspension.

[0063] S2, adding N-isopropylacrylamide and acrylic acid into the photothermal conversion material suspension and stirring for 2 hours, ultrasonically dispersing for 8 minutes and stirring for 25 minutes to fully dissolve.

[0064] S3, add an APS aqueous solution with a mass concentration of 10%wt and an MBAA aqueous solution with a mass concentration of 2.5%wt, continue stirring for 20 minutes, then transfer to a 0°C ice water bath, add TMEDA after the solution is cooled, continue stirring for 5 minutes, pass nitrogen, and let stand for 24 hours to obtain an environmentally responsive hydrogel.

[0065] Example 4

[0066] An environmentally responsive hydrogel is composed of the following raw materials in parts by weight: 50 parts of stimulus-responsive hydrogel monomers (N-isopropylacrylamide and acrylic acid), 350 parts of an aqueous phase dispersant (methyl cellulose), 7 parts of a photothermal conversion material (carbon nanotubes), 8 parts of a free radical thermal initiator (ammonium persulfate), 7 parts of a crosslinking agent (N,N-methylenebisacrylamide), and 16 parts of a catalyzer (N,N,N',N'-tetramethylethylenediamine).

[0067] The weight ratio of the above-mentioned N-isopropylacrylamide, acrylic acid, methylcellulose aqueous solution, CNT, APS aqueous solution, MBAA aqueous solution, and TMEDA is 45:5:350:7:8:7:16.

[0068] The method for preparing the above-mentioned environmentally responsive hydrogel comprises the following steps:

[0069] S1, adding carbon nanotubes into a methyl cellulose aqueous solution with a mass concentration of 5 mg / mL, ultrasonically dispersing for 5 minutes and stirring for 2 hours to obtain a uniformly dispersed photothermal conversion suspension.

[0070] S2, adding N-isopropylacrylamide and acrylic acid into the photothermal conversion material suspension and stirring for 2 hours, ultrasonically dispersing for 10 minutes and stirring for 20 minutes to fully dissolve.

[0071] S3, add an APS aqueous solution with a mass concentration of 10%wt and an MBAA aqueous solution with a mass concentration of 2.5%wt, continue stirring for 20 minutes, then transfer to a 0°C ice water bath, add TMEDA after the solution is cooled, continue stirring for 5 minutes, pass nitrogen, and let stand for 24 hours to obtain an environmentally responsive hydrogel.

[0072] Example 5

[0073] An environmentally responsive hydrogel is composed of the following raw materials in parts by weight: 50 parts of stimulus-responsive hydrogel monomers (N-isopropylacrylamide and acrylic acid), 425 parts of an aqueous phase dispersant (methyl cellulose), 8 parts of a photothermal conversion material (carbon nanotubes), 12 parts of a free radical thermal initiator (ammonium persulfate), 6 parts of a crosslinking agent (N,N-methylenebisacrylamide), and 17 parts of a catalyzer (N,N,N',N'-tetramethylethylenediamine).

[0074] The weight ratio of the above-mentioned N-isopropylacrylamide, acrylic acid, methylcellulose aqueous solution, CNT, APS aqueous solution, MBAA aqueous solution, and TMEDA is 45:5:425:8:12:6:17.

[0075] The method for preparing the above-mentioned environmentally responsive hydrogel comprises the following steps:

[0076] S1, adding carbon nanotubes into a methyl cellulose aqueous solution with a mass concentration of 5 mg / mL, ultrasonically dispersing for 5 minutes and stirring for 2 hours to obtain a uniformly dispersed photothermal conversion suspension.

[0077] S2, adding N-isopropylacrylamide and acrylic acid into the photothermal conversion material suspension and stirring for 2 hours, ultrasonically dispersing for 10 minutes and stirring for 20 minutes to fully dissolve.

[0078] S3, add an APS aqueous solution with a mass concentration of 10%wt and an MBAA aqueous solution with a mass concentration of 2.5%wt, continue stirring for 20 minutes, then transfer to a 0°C ice water bath, add TMEDA after the solution is cooled, continue stirring for 5 minutes, pass nitrogen, and let stand for 24 hours to obtain an environmentally responsive hydrogel.

[0079] The performance test of the environment-responsive hydrogel of the above embodiment when used in the actuator intelligent microvalve is as follows:

[0080] The environmentally responsive hydrogel prepared by the present invention is placed in a buffer solution at room temperature or 45° C. and pH values ​​of 4, 5 and 6.5 respectively for proton exchange, and is then placed in a plastic model of an actuator intelligent microvalve.

[0081] When the pH value of the acetic acid-sodium acetate buffer solution is 4, the entire driver intelligent microvalve system is placed in a room temperature environment, and the grooves on both sides are filled with a buffer solution with a pH value of 4, and the hydrogel expands to the maximum in the middle groove. At first, the hydrogel squeezes the Ecoflex film in front to seal the round hole, and the valve is in a closed state. Add blue dye to the left water tank, wait for 30 minutes, and there is no color change in the right water tank, indicating that the valve has good sealing. Then irradiate the hydrogel with near-infrared light (808nm, 2W), the hydrogel begins to shrink visibly, the Ecoflex film returns to its original state to open the round hole, and the blue liquid gradually flows to the right water tank. When the near-infrared emitter is turned off, the hydrogel gradually expands. Add yellow dye to the left water tank again. It can be seen from the figure that the water in the left water tank has turned green, while the right side is still blue. This shows that by applying the hydrogel prepared by the present invention to a microvalve, good control of fluid circulation can be achieved, and it has better control stability.

[0082] When the pH value of the disodium hydrogen phosphate-sodium dihydrogen phosphate buffer solution is 6.5, the entire microvalve system is placed on a heating table, and the grooves on both sides are filled with buffer solutions with a pH value of 6.5 and a temperature of 45°C. The hydrogel expands to the maximum in the middle groove. At first, the hydrogel squeezes the Ecoflex film in front to seal the round hole, and the valve is in a closed state. Add blue dye to the left sink, and after waiting for 30 minutes, there is no color change in the right sink, indicating that the valve is in a good state of closure. Next, the hydrogel is irradiated with near-infrared light, and there is no obvious change in the hydrogel, the round hole is still closed, and the blue liquid cannot flow to the right sink. It can be seen that the hydrogel microvalve is in a normally closed state at this time. Therefore, the hydrogel has a better control effect on the microvalve.

[0083] When the pH value of the acetic acid-sodium acetate buffer solution is 5, the entire microvalve system is placed on the heating table, and the grooves on both sides are filled with buffer solutions with a pH value of 5 and a temperature of 45°C, and the hydrogel expands to the maximum in the middle groove. At first, the hydrogel squeezes the Ecoflex film in front to seal the round hole, and the valve is in a closed state. Add blue dye to the left water tank, wait for 30 minutes, and there is no color change in the right water tank, indicating that the valve is in a good closed state. Then use near-infrared light to irradiate the hydrogel, the volume of the hydrogel is slightly reduced, the round hole opens, and the blue liquid slowly flows to the right water tank. When the near-infrared emitter is turned off, the hydrogel still cannot expand. At this time, yellow dye is added to the left water tank, and the water in the right water tank has turned green. This shows that the shape of the hydrogel when it shrinks is memorized. Although there is no near-infrared irradiation, the hydrogel microvalve is still in an open state, which fully demonstrates that the environmentally responsive hydrogel prepared by the present invention has better response hysteresis stability.

[0084] In summary, the environmentally responsive hydrogel prepared by the present invention has a three-cross-linked network structure and has dual response functions of pH and temperature, fast response speed and high precision. At the same time, it will show hysteresis in the response process, which effectively solves the current technical problems that the response of hydrogel is closely related to the stimulus and the response cannot be maintained alone; the hysteresis of hydrogel is unstable. The environmentally responsive hydrogel is applied to the actuator intelligent microvalve to realize intelligent control integrating sensing input signal, intelligent memory analysis and output driving behavior.

[0085] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing an environmentally responsive hydrogel, characterized in that: The following steps are involved: Adding the photothermal conversion material into the aqueous solution of the aqueous phase dispersant and dispersing the material to obtain a photothermal conversion material suspension; Add a stimulus-responsive hydrogel monomer to the photothermal conversion material suspension, dissolve it, add a free radical thermal initiator and a cross-linking agent, stir, cool, and then add a promoter initiator to carry out a polymerization reaction in a nitrogen atmosphere. During the polymerization process, the carbon-carbon double bond of the cross-linking agent is broken, and it reacts with the aqueous phase dispersant and the stimulus-responsive hydrogel monomer under the action of the free radical thermal initiator and the promoter initiator to form a cross-linked structure, and then the photothermal conversion material is loaded in the cross-linked structure to obtain an environmentally responsive hydrogel.

2. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The mass concentration of the aqueous solution of the aqueous phase dispersant is 5 mg / mL, and the mass ratio of the photothermal conversion material to the aqueous solution of the aqueous phase dispersant is 5-9:325-450.

3. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The mass ratio of the stimulus-responsive hydrogel monomer to the photothermal conversion material is 40-60:5-9.

4. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The mass ratio of the free radical thermal initiator, the crosslinking agent and the accelerator is 10-15:5-10:15-20.

5. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The stimulus-responsive hydrogel monomer is one or more of N-isopropylacrylamide, acrylic acid, N-propylacrylamide or sodium alginate.

6. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The photothermal conversion material is one or more of carbon nanotubes, silver nanowires, and carbon black.

7. The method for preparing the environmentally responsive hydrogel according to claim 1, characterized in that: The free radical thermal initiator is one or more of ammonium persulfate, azobisisobutyronitrile, and diacyl peroxide; the crosslinking agent is one or more of N,N-methylenebisacrylamide, diisopropylbenzene peroxide, butadiene, and vinylbenzene; the accelerator is one or more of N,N,N',N'-tetramethylethylenediamine, propylenediamine, and isopropylenediamine.

8. An environmentally responsive hydrogel prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the environmentally responsive hydrogel according to claim 8 in an actuator intelligent microvalve.

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