CN113754897B

CN113754897B - Strippable ultrathin hydrogel, preparation method and application

Info

Publication number: CN113754897B
Application number: CN202110980155.6A
Authority: CN
Inventors: 程思敏; 徐晓敏
Original assignee: Shenzhen International Graduate School of Tsinghua University
Current assignee: Shenzhen International Graduate School of Tsinghua University
Priority date: 2021-08-25
Filing date: 2021-08-25
Publication date: 2024-02-02
Anticipated expiration: 2041-08-25
Also published as: CN113754897A

Abstract

The invention discloses a strippable ultrathin hydrogel, a preparation method and application thereof. The thickness-adjustable strippable ultrathin hydrogel is successfully obtained by extruding the hydrogel coated between the double-layer hydrophobic films by using a simple double-roll coater. The hydrogel film prepared by the method can be easily and completely peeled off from the surface of the hydrophobic film, and the thickness of the hydrogel film can reach 10 mu m at the minimum. The preparation method disclosed by the invention is simple in equipment, easy to operate, low in cost, high in repeatability and universal for different types of hydrogels, and provides a new idea for producing large-area ultrathin hydrogels. And the invention applies it to flexible electronic devices and skin interfaces as super breathable adhesive layers.

Description

Strippable ultrathin hydrogel, preparation method and application

Technical Field

The invention relates to the field of hydrogel materials, in particular to a strippable ultrathin hydrogel, a preparation method and application thereof.

Background

Hydrogels are materials with a three-dimensional hydrophilic polymer network structure that can absorb and immobilize large amounts of moisture. Because of its good biocompatibility and Young's modulus close to human tissue, it is widely used in biomedical and cosmetic fields, including drug release, tissue engineering, mask, etc. Meanwhile, the porous material has good permeability to oxygen and nutrient components, and is widely applied to wound dressings and contact lenses.

In recent years, the rise of adhesive hydrogels has further expanded the application field of hydrogels. Researchers develop hydrogels that can form stable chemical bonds with different substrates, and even can be applied to wet surfaces of some tissues in the human body, with extremely high interfacial bonding forces. Meanwhile, the hydrogel can be used as a novel in-vivo adhesive for repairing tissues and avoiding inflammatory reaction. Hydrogels have also received considerable attention in recent studies as a new type of ionic skin. The adjustable adhesive properties and biocompatibility of hydrogels hold good promise in the field of skin electronics, but related reports are rarely seen at present.

The currently available methods for preparing hydrogel films are mostly limited to die casting or spin coating. None of these methods is suitable for the preparation of ultra-thin large area hydrogel films, which has the drawbacks: when the hydrogel film is prepared by adopting a die casting method, the thickness and the preparation area of the hydrogel film are limited by the precision and the size of the die, the hydrogel film with the thickness less than 100 mu m is difficult to prepare, and the uniformity of the film cannot be controlled; although spin coating can prepare ultra-thin hydrogels with a thickness of 10 μm, a large amount of water loss during spin coating is detrimental to stable structure molding and the resulting films are limited in size.

In addition, since the hydrogel needs to be uniformly leveled on the surface of the substrate during the preparation process, a relatively hydrophilic substrate, such as glass, quartz or PET film with improved hydrophilicity after being treated by plasma, is required, so that the prepared hydrogel film is difficult to peel from the substrate.

Disclosure of Invention

The invention aims to provide a strippable ultrathin hydrogel, a preparation method and application thereof, so that the preparation of the ultrathin hydrogel with large area is realized, and the prepared ultrathin hydrogel is very easy to strip from a substrate.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

in one aspect, the present invention provides a method for preparing a strippable ultrathin hydrogel, the method comprising:

coating one-step reaction type hydrogel collagen liquid between two substrates, and pressing by using double rollers to obtain the strippable ultrathin hydrogel; the substrate is a hydrophobically modified release film.

The one-step reaction type hydraulic collagen liquid is a hydraulic collagen liquid to which all the components required for the reaction are added and which has not been gelled yet, and can be obtained by the prior art, and the present invention is not limited thereto. Such as polyacrylamide/sodium alginate hydrogels, gelatin/glycerol hydrogels.

In a preferred embodiment, the thickness of the two release films is different and/or the release force is different. In the preferred scheme, the release films with different thicknesses and/or different release forces are used as the protective layers of the hydrogel, so that the hydrogel is kept intact and is easier to peel.

In a preferred embodiment, the surface of the side of the release film, which is contacted with the hydraulic collagen liquid, is modified to be hydrophobic.

In a preferred scheme, the release film is a PET film or a PVC film.

In a preferred embodiment, after the releasable ultrathin hydrogel is obtained, the releasable ultrathin hydrogel with two release films is stored in a sealed manner. In the preparation process and the subsequent preservation process of the invention, the two sides of the hydrogel film are covered by the PET film, thus preventing water loss in the preparation and storage processes.

In a preferred scheme, the space between the two rollers can be regulated and controlled within the range of 10-1000 mu m so as to obtain hydrogel films with different thicknesses, and the thickness of the hydrogel film obtained by the method can reach 10 mu m at the lowest.

In a preferred scheme, the temperature of the double-roller pressing is 30-200 ℃; the double rollers have a heating function, and the heating interval is 30-200 ℃.

In a preferred embodiment, the strippable ultrathin hydrogelThe side length is (0.1-60) cm, preferably (0.1-30) cm; the method of the present invention can be used in large areas (e.g., 20X 30cm in the examples) ² 、18×60cm ² ) The hydrogel film which is uniformly distributed and can be completely peeled is prepared in the range.

In another aspect, the present invention provides a releasable ultrathin hydrogel obtained by the above preparation method.

According to the releasable ultrathin hydrogel of the invention, preferably, the releasable ultrathin hydrogel comprises a hydrogel film and two hydrophobically modified release films attached to two side surfaces of the hydrogel film.

In yet another aspect, the present invention provides the use of the above-described strippable ultrathin hydrogels as a superbreathable adhesive layer for flexible electronic device-to-skin interfaces. Specifically, for example, the hydrogel film prepared by the method is used as a packaging layer of the electronic device, and the flexible electronic device packaged by the hydrogel is attached to the skin surface, so that the skin moisture is kept breathable, and the electrical performance of the flexible electronic device is not influenced.

The invention adopts a double-roller coater with adjustable spacing, can ensure that the thickness of the prepared hydrogel is controllable and the film is uniformly distributed in a large-area (the side length can reach 60 cm) range. In the preparation process and the subsequent preservation process, the surfaces of both sides of the hydrogel film are covered by the PET film, so that the water loss in the preparation and reaction processes is prevented; meanwhile, the surface of the PET film, which is contacted with the hydrogel film, is subjected to hydrophobic treatment, so that the large-area hydrogel film can be completely peeled off. Further, PET films with different release forces and/or different thicknesses are used as the protective layer of the hydrogel, so that the hydrogel is kept intact and is easier to peel.

Drawings

FIG. 1 is a schematic view of a twin roll coater and operation used in an embodiment of the present invention.

FIGS. 2a and 2b are large area strippable hydrogels prepared in example 1; wherein fig. 2a is a very large area hydrogel film sandwiched between double protective films, and fig. 2b is a hydrogel film peeling process and a completely peeled hydrogel film.

FIG. 3a is a cross-sectional view of the protective layer and hydrogel film of example 1.

FIG. 3b is a graph showing the thickness of the hydrogel film measured using a step ladder in example 1.

Fig. 4 is a graph showing the effect of applying the hydrogel film prepared in example 1 to the skin surface for a long period of time.

Fig. 5 shows that the PET treated with plasma in comparative example 2 was used as a protective film to make ultra thin.

FIGS. 6a and 6b are photovoltaic devices using the large area strippable hydrogels prepared in example 5 using the method of the present invention as skin interface layers; fig. 6a shows the transmittance of hydrogel films of different thickness, and fig. 6b shows the attachment of hydrogel film-encapsulated photovoltaic devices to the skin surface.

Fig. 7 shows the current-voltage (J-V) curve of the photovoltaic device and the J-V curve of the device after attachment of the hydrogel, and it can be seen from comparison that the hydrogel has substantially no effect on the device performance.

Detailed Description

In order to more clearly illustrate the present invention, the present invention will be further described with reference to preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.

Example 1

The hydrogel film is prepared by a chemical crosslinking method in the embodiment:

sodium alginate was dissolved in 6mL of pure water to prepare a 1wt% aqueous solution, which was stirred at room temperature for 4 hours to dissolve, and stirred at 50℃for 30 minutes to swell. 1mL of an aqueous acrylamide solution (concentration: 10 wt%) was added and stirred for 10 minutes, followed by 490. Mu.L of an aqueous N, N' -methylenebisacrylamide crosslinking agent (0.15 wt%) and an aqueous ammonium persulfate thermal initiator solution (concentration: 5 wt%) were added and stirred for 2 hours until uniformly mixed to obtain a mixed solution.

Selecting two PET release films with surface release force of 15-20g, thickness of 25 μm and 75 μm respectively, length of 15cm and width of 10cm, wherein one side surface of the two PET release films is subjected to silicone oil coating treatment (the PET films adopted in the embodiment are purchased from Shanghai Huadong composite material filter cloth screen mill), cutting, then enabling the silicone oil treatment surface of the PET release film with thickness of 75 μm to face upwards, cleaning the double rollers by adopting a double-roller coater as shown in figure 1, adjusting the roller spacing to about 150 μm, and keeping the double-roller spacing to be about consistent.

To 1mL of the above mixed solution was added 50. Mu.L of an aqueous ammonium persulfate solution having a concentration of 5wt% and stirred for 3 minutes, then 20. Mu.L of an aqueous N, N, N ', N' -tetramethyl ethylenediamine solution having a concentration of 20wt% was added and stirred for 30 seconds, and the mixed stock solution was poured about 1mL to the prepared 75 μm thick release film surface, taking note that the dropping point was not excessive. The silicone oil treatment surface of the PET release film with the thickness of 25 mu m is covered on the hydrogel, one end of the two layers of PET release films with the hydrogel mixed solution in the middle is inserted into a double roller of a cold mounting machine, as shown in figure 1, and a handle is gently rotated to roll the double roller, so that the PET release film is naturally pressed in. The whole process needs to keep the hydrogel in a good flowing state.

After pressing the hydrogel film, it was sealed with a plastic bag, left overnight at room temperature, and removed as shown in fig. 2 a. The 25 μm thick PET release film was gently torn off to give a hydrogel film 8cm wide and 15cm long which remained intact on the 75 μm thick PET release film. The four sides of the hydrogel were stuck with tape, which was gently pulled up from the PET surface, and the tape simultaneously supported the torn hydrogel film as shown in fig. 2 b. The thickness of the film is 40-50 μm (shown in FIG. 3 b) after being tested by a step ladder, the cross section of the film is shown in FIG. 3a, and the film can be seen to be uniform in thickness.

The ultrathin hydrogel with the release film can be directly attached to the surfaces of metal, glass, silicon wafer or skin and the like, and then the release film layer is gently torn off, so that the ultrathin hydrogel can be completely adhered to the surface of an application substrate. Due to the extremely low Young's modulus and the thickness of less than 50 μm, the hydrogel can adhere well to the skin surface without falling off easily. FIG. 4 is a graph showing the effect of the resulting hydrogel film on long-term adhesion to the skin surface.

Example 2

The hydrogel film is prepared by a physical crosslinking method in the embodiment:

after 2g of gelatin was immersed in a mixed solvent of 9g of glycerin and 3g of pure water for 12 hours, the mixture was stirred at 70℃for 2 hours, and then placed in a 90℃oven until all bubbles disappeared.

The heating switch of the twin-roll coater was turned on (heating interval 30-90 ℃) and the twin rolls were heated to 90 ℃ to steady state. The laminator is similar in structure to the twin roll coater of fig. 1, with only twin rolls adding a heating function.

1mL of the mixed solution is poured on the surface of a PET release film (purchased from Hua Hong composite material Co., ltd.) with the thickness of 100 mu m, the length of 15cm and the width of 10cm when the mixed solution is hot, the surface is treated by silicone oil, the release force of 7-10g is 7-12 g, the surface is covered with another PET release film (purchased from Shanghai Huadong composite material filter cloth screen mill) with the thickness of 19 mu m (release force of 8-12 g) and the surface is treated by silicone oil, and the PET release film is quickly transferred between two rollers of a film laminating machine to be pressed and molded. The fluidity of the hydrogel is maintained as much as possible in the whole process.

Placing the sealed hydrogel film in a refrigerator, and taking out after the reaction is completed to obtain the product with an area of about 8X10 cm ² The thickness of the hydrogel film was measured to be 80 to 90. Mu.m.

Example 3

The surface of the substrate is not treated, but has a thickness of 100 μm and an area of 10×15cm ² Is a PVC film. 3M Novec 1700 and 3M Novec 7100 were combined at 1:7, preparing a solution, performing plasma treatment on the surface of a PVC film, uniformly coating the Novec solution on the surface of the PVC film by using a four-side coater, volatilizing the solvent, pouring the hydraulic collagen solution prepared in the example 1 on the surface of the PVC film, and pressing by using a double roller. After the reaction is completed, the protective film is torn off to obtain the hydrogel film.

Example 4

In this example, a PET release film (purchased from Shanghai Huadong composite insulating filter cloth screening mill) with a thickness of 50 μm, which had been subjected to silicone oil coating treatment, and a PET release film (fluorous release film, purchased from Sitting adhesive tape store, model number FA 050) with a thickness of 50 μm, which had been subjected to fluorination treatment, were used, and after cutting, the polyacrylamide/sodium alginate mixed solution prepared in example 1 was applied by dropping on the surface silicone oil-treated PET release film by suction with a dropper, and thereafter the same as in example 1 was used.

Example 5

With the PET release films used in example 1 and example 3 having a thickness of 75 μm and 50 μm, respectively, and a release force of 15 to 20g, a width of 20cm and a length of 1m, 30mL of the gelatin/glycerin hydrogel mixed solution prepared in example 2 was placed in an oven and heated at 90℃for half an hour, and then taken out. The heating button of the double-roll coater is turned on, the heating temperature is set to 90 ℃, the mixed hot solution of the hydrogel is poured on the PET release film uniformly at intervals of 10cm by about 5mL, meanwhile, the double-roll coater is rolled to coat and shape the hydrogel, and then the hydrogel is taken out after being placed in a refrigerator to wait for about 1 h.

The hydrogel film of this example was obtained in a width of about 18cm, a length of about 60cm and a thickness of 100 to 110. Mu.m.

Example 6

In this example, the strippable ultrathin hydrogel prepared in example 1 was used as a super breathable adhesive layer at the interface between a flexible electronic device and skin.

The ultra-thin hydrogel was fixed on a jig and the film was tested for visible light absorption in the range of 200-900nm using an ultraviolet-visible spectrophotometer, and the results are shown in FIG. 6 a. According to the results of the transmittance of the hydrogel films with different thicknesses, the super-transparent hydrogel film has 92% transmittance in the range of 800-380 nm. The peeled ultrathin hydrogel was attached to both sides of the photovoltaic device, respectively, and the hydrogel encapsulation device and its display attached to the skin surface are shown in fig. 6 b.

Placing the hydrogel-encapsulated device at 100mW/cm ² And testing the photovoltaic performance under a xenon lamp and connecting a source meter, comparing the device performance before encapsulation, and determining that the hydrogel encapsulation has no influence. Fig. 7 shows the current-voltage (J-V) curve of the photovoltaic device and the J-V curve of the device after attachment of the hydrogel, and it can be seen from comparison that the hydrogel has substantially no effect on the device performance.

Comparative example 1

PET films (purchased from Hua Hong composite company and Shanghai Huadong composite insulating filter cloth screening mill) with thicknesses of 100 μm and 50 μm respectively, each of which had not been subjected to silicone oil treatment, were cut into films with a size of 15X 10cm, and about 0.5mL of the polyacrylamide/sodium alginate hydrogel mixed solution prepared in example 1 was poured onto the surface of the PET film, followed by the same procedure as in example 1.

The area obtained was 10X 8cm ² The film can be partially separated from the surface of the PET film, but for a large-area hydrogel film, the film is difficult to completely separate from the surface, and the film is extremely easy to damage due to forced separation.

Comparative example 2

PET films each having a thickness of 100 μm and 50 μm, respectively, on the surface of which silicone oil was not treated in comparative example 1 were cut into films having a size of 15X 10cm, and after 5 minutes of treatment with plasma, about 0.5mL of the polyacrylamide/sodium alginate hydrogel mixed solution prepared in example 1 was poured onto the surface of the PET film, followed by the same procedure as in example 1.

As shown in fig. 5, after tearing the upper 100 μm protective film, it was found that the hydrogel film had adhesiveness to both the protective films, resulting in tearing of the resulting film, incomplete film, and failure to peel from the substrate.

It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. The preparation method of the strippable ultrathin hydrogel is characterized by comprising the following steps of:

coating one-step reaction type hydrogel collagen liquid between two substrates, and pressing by using double rollers to obtain the strippable ultrathin hydrogel;

the substrate is a hydrophobically modified release film, and the surface of one side of the release film, which is contacted with the hydraulic collagen liquid, is hydrophobically modified;

the thickness of the two release films is different and/or the release force is different;

the space between the two rollers is 10-1000 mu m.

2. The method according to claim 1, wherein the release film is a PET film or a PVC film.

3. The method according to claim 1, wherein the releasable ultrathin hydrogel with two release films is stored in a sealed state after the releasable ultrathin hydrogel is obtained.

4. The method according to claim 1, wherein the temperature of the twin-roll press is 30 to 90 ℃.

5. The method of claim 1, wherein the strippable ultrathin hydrogel has a side length dimension of (0.1-60) cm.

6. A releasable ultrathin hydrogel obtained by the production process of any one of claims 1 to 5;

the strippable ultrathin hydrogel comprises a hydrogel film and two hydrophobically modified release films attached to two side surfaces of the hydrogel film.

7. Use of the strippable ultrathin hydrogel of claim 6 as a superbreathable adhesive layer for flexible electronic device-to-skin interfaces.