KR101741802B1 - Method for preparing stomata-inspired membrane and stomata-inspired membrane prepared thereby - Google Patents

Abstract

The present invention relates to a membrane in the form of a thermoreactive hydrogel and a method for producing the membrane. More particularly, the present invention relates to a membrane that is characterized in that the size of a hole is changed with respect to a temperature stimulus, Methods, membranes thus prepared and their use. The temperature-responsive hydrogel-type membrane produced according to the method of the present invention is very simple and inexpensive to simultaneously form a polymer membrane and a hole having different physical properties even by a single exposure, A biomimetic membrane can be produced. Further, since the actuator is composed of two parts having different physical properties by using one material, when the two types of hydrogels having different physical properties are used, it is possible to solve the defect problem occurring at the joint part. It has the advantage that it can be changed variously and easily according to the application field, and shows a very useful effect in various industries.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for preparing a pore-simulated membrane, and a biomimetic membrane produced thereby,

The present invention relates to a membrane in the form of a thermoreactive hydrogel and a method for producing the membrane. More particularly, the present invention relates to a membrane that is characterized in that the size of a hole is changed with respect to a temperature stimulus, Methods, membranes thus prepared and their use.

A stimulus-reactive hydrogel is a polymer in which the properties of a substance change in response to external stimuli such as temperature or pH. And can be applied to many fields such as fluid engineering, medicine, and biotechnology which can easily control the dynamic behavior of such polymers and realize special functions. Conventional methods of producing a hydrogel having an actuator were to drill repeated pattern holes in a hydrogel to induce buckling, folding, folding, etc. in the hole, or to bond two kinds of hydrogels having different physical properties to induce bending. However, the conventional method has a disadvantage in that the manufacturing process is complicated and defects may occur at the joint portion during operation.

On the other hand, the leaf of the plant has a stimulus-responsive actuator that controls the exchange of gas by opening and closing the pores in response to temperature, humidity, oxygen / carbon dioxide concentration and the like. In this regard, although some engineering applications in which plant leaves have been simulated have been proposed, there is no known method for biomimetic simulation of the irritant-reactive movement of pores present in plant leaves as well as a method for producing the membrane.

Under these circumstances, it is an object of the present invention to provide a method for producing a temperature-responsive membrane in which plant leaves are biochemically simulated by photopolymerization by ultraviolet exposure, and a temperature-responsive membrane produced thereby.

According to one aspect of the present invention, there is provided a method for producing a temperature-responsive biomimetic membrane.

Specifically, the method of manufacturing the membrane may include the following steps:

a) applying a solution mixed with a monomer, a crosslinking agent and a photoinitiator on a substrate; And

b) photopolymerizing the substrate to which a solution containing the monomer, the crosslinking agent and the photoinitiator is applied through a photomask having a desired pattern,

The step a) is to prepare a mixed solution to be photopolymerized before photopolymerization through exposure and to apply it on a substrate. Specifically, a monomer, a crosslinking agent and a photoinitiator are mixed to prepare a solution, which is then applied onto a substrate.

 At this time, as the monomer, any monomer which can be photopolymerized by exposure and shows a hydrogel shape after polymerization can be freely used, preferably N-isopropylacrylamide monomer (NIPAAm). On the other hand, as the crosslinking agent, any crosslinking agent can be used without limitation as long as it can crosslink the monomers to be used, and preferably N, N-methylenebisacrylamide (MBAm) can be used. The photoinitiator refers to a material that absorbs energy from light to initiate a polymerization reaction. A known photoinitiator may be used without limitation, but preferably 2-hydroxy-1- [ 4- (hydroxyethoxy) phenyl] -2-methyl-1-propanone (Igacure 2959) can be used.

In one preferred embodiment, the mixing weight ratio of the monomer, the crosslinking agent and the photoinitiator may be 1 to 3 parts by weight of the crosslinking agent and 0.5 to 2.5 parts by weight of the photoinitiator based on 100 parts by weight of the monomer. Various solvents may be used as a solvent for preparing the above components as a solution, but water (distilled water) may be preferably used. The monomer, the crosslinking agent and the photoinitiator are mixed to prepare a solution, which is then poured or applied onto a suitable substrate.

Further, in step b), a photomask having a desired pattern is applied on a substrate to which the mixed solution of step a) is applied, and then light is irradiated to perform photopolymerization by performing exposure. The exposure used in the present invention means that the energy rays are continuously irradiated through a photomask having a desired pattern. Further, the photomask refers to a portion in which a light transmitting portion and a light shielding portion of the energy ray are arranged in a desired pattern. In a specific embodiment, a transparent photomask on which a desired pattern is printed is coated on a substrate to which a mixed solution containing a monomer, a crosslinking agent and a photoinitiator prepared in step a) is applied, and then exposed to an energy ray, preferably ultraviolet ray. The solution covered by the pattern printed on the photomask is not exposed to ultraviolet rays, and the solution located on the unprinted portion of the photomask is exposed to ultraviolet rays. At this time, the photoinitiator in the exposed solution starts the polymerization reaction with the monomer and the cross-linking agent, generating free radicals. Since the intensity of the light to be exposed has a regular (Gaussian) distribution, the most intense light is exposed at the middle portion and the polymerization reaction is started at this central portion (see FIG. At this time, as the monomer and the cross-linking agent are consumed, the chemical potential gradient is formed and the monomer and the cross-linking agent spread to the central portion of the exposed region. On the other hand, a free chemical is formed in the exposed part, whereas a chemical potential gradient is formed in the unexposed part because there is no free radical, and the free radical is diffused into the unexposed part. As this phenomenon continues, a relatively thick polymer is formed in the central region of the exposed portion and a thin polymer is formed in the outer portion (see FIG. 2E). In the present invention, the thick part of the formed polymer is called a 'frame', and the thin part is called a 'base'. It is possible to produce temperature-responsive membranes having various desired shapes by changing the shape of the pattern to be printed on the photomask.

In yet another aspect, the present invention relates to a thermoreactive biomimetic membrane made by the above method. Specifically, the membrane is sensitive to stimulation, preferably temperature stimulation, so that the size of the hole located in the membrane changes.

When a polymer such as PNIPAAm polymerized with NIPAAm, which is one of the monomers used in the present invention, is heated to a lower critical temperature (32 DEG C) or higher, the polymer formed decreases in volume as it releases water. At this time, as the density of the polymer is increased, the volume expansion ratio is lowered, so that the relatively dense frame portion has a lower volume expansion ratio than the base portion, , But it contains two parts having different physical properties. Thus, when the membrane is heated, a large volume change occurs at the base portion rather than the frame portion. Therefore, when the edge of the membrane manufactured according to the above manufacturing method is fixed and then heated, the frame portion maintains the shape of the membrane due to the difference in volume change rate between the frame portion and the base portion, but the base portion shrinks greatly and the size of the hole increases. The change in temperature reactivity of the holes located in these membranes is a biomimetic simulation of the movement of pores that control the size of the pores in response to temperature changes.

As described above, in the case of manufacturing the membrane according to the manufacturing method of the present invention, it is possible to form two portions having different physical properties, specifically, an expansion ratio in one membrane by a simple process of one exposure using one kind of material Whereby it is possible to provide a membrane having fine-sized, repetitive holes having actuators that are responsive to stimuli such as temperature. Such a temperature-responsive membrane is a technology that automatically controls the cooling performance of a cooling device such as an air conditioner, or a technology that autonomously controls and transfers a drug in a drug delivery device, Applicable to the field. In this case, the shape of the photomask can be changed freely according to the application field, and the membrane having the holes having various shapes can be used autonomously, which makes it possible to manufacture easily and efficiently.

The temperature-responsive hydrogel-type membrane produced according to the method of the present invention is very simple and inexpensive to simultaneously form a polymer membrane and a hole having different physical properties even by a single exposure, A biomimetic membrane can be produced. Further, since the actuator is composed of two parts having different physical properties by using one material, when the two types of hydrogels having different physical properties are used, it is possible to solve the defect problem occurring at the joint part. It has the advantage that it can be changed variously and easily according to the application field, and shows a very useful effect in various industries.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing the names and chemical formulas of constituent components contained in a mixed solution of a monomer, a crosslinking agent and a photoinitiator. FIG.
Figure 2 illustrates the principle and process of making a temperature responsive membrane according to the present invention using a photopolymerization process.
FIG. 3 is a photograph showing the process of forming a pore-forming membrane by photopolymerization reaction through ultraviolet exposure at intervals of 30 seconds.
FIG. 4 is a photograph showing morphological changes of various types of pore-simulating membranes and membranes according to temperature.

Example  One: Monomers, Cross-linking agent  And Photo initiator  Preparation of mixed solution

100 mg of monomer N- isopropylacrylamide monomer (NIPAAm), 1 mg of crosslinker N , N'- methylenebisacrylamide (MBAm), 1 mg of photoinitiator 2-hydroxy-1- [4- hydroxyethoxy) phenyl] -2-methyl-1-propanone (Irgacure 2959) was dissolved in 0.7 ml of distilled water to prepare a solution.

Example 2: Fabrication of a pore-simulated membrane using a photopolymerization process

A solution mixed with a monomer, a crosslinking agent, and a photoinitiator was poured onto the bowl and covered with various patterned photomasks (see FIG. 2A). When the photoinitiator is exposed to ultraviolet light for 4 minutes on a photomask (VIRVER Lourmat, model: 4.L, wavelength = 365 nm, power: 4 W) And began to photopolymerize with monomers and crosslinking agents. At this time, free radicals and monomers diffuse in opposite directions (Fig. 2C). A free radical chemical potential gradient was generated between the portion exposed to the ultraviolet ray and the portion not exposed to the radiation so that the free radicals were diffused to the portion not exposed. On the other hand, in the exposed portion, photopolymerization occurs and the monomers are consumed, and the monomers are diffused to the center of the exposed region by the chemical potential (see FIG. 2C). At this time, poly ( N- isopropylacrylamide) (PNIPAAm) formed by polymerization reaction was covalently attached to the surface of the photomask.

Example  3: Through ultraviolet exposure Light curing  Reaction The membrane  Process of formation

직경의 마스크 무늬로 자외선에 노광되지 못하는 용액을 나타낸다. 노광을 시작한지 3분 후, 투명한 용액이 점차 불투명하게 변해갔다(도 3a 참조). 그리고 노광된 영역의 중앙 부분부터 불투명한 격자 형태의 중합체가 형성되었다(도 3b 참조). 노광이 지속될수록 불투명한 중합체 형성이 나머지 부분들로 확대되었다(도 3c, d 참조). 노광을 시작한지 5분 후, 마스크 무늬를 제외한 대부분의 영역이 불투명한 중합체로 채워졌다(도 3e 참조). 삽도는 광중합에 기인하여 단량체와 포토개시제가 확산되는 과정을 보여주고 있다.The photopolymerization reaction was induced by ultraviolet exposure to confirm the formation process of the pore simulation membrane. In order to prepare a membrane according to Example 2, the film was photographed at intervals of 30 seconds while exposed to ultraviolet rays, and the results are shown in FIG. 3, the dotted line indicates 500

A mask pattern of a diameter indicates a solution which can not be exposed to ultraviolet rays. Three minutes after the start of the exposure, the clear solution gradually became opaque (see FIG. 3A). And an opaque lattice-like polymer was formed from the central portion of the exposed region (see Fig. 3B). As the exposure continued, the opaque polymer formation expanded to the rest (see Fig. 3c, d). After 5 minutes from the start of exposure, most of the area except the mask pattern was filled with opaque polymer (see FIG. 3E). The illustration shows the diffusion of monomer and photoinitiator due to photopolymerization.

Example 4: Deformation of membranes according to various types of prepared pore-simulating membranes and temperature

It has been confirmed that a pore-simulated membrane with various holes can be fabricated using a photomask having various patterns. FIG. 4A shows an image obtained by observing the actually fabricated pore simulation membranes with an optical focus microscope, and the illustration shows the shape of the photomask used in each fabrication process. When PNIPAAm is heated above the lower critical temperature of 32 ° C, the volume is reduced while releasing water. By changing the characteristics of these materials, it is possible to induce the deformation of the pore-forming membrane by changing the ambient temperature. After the edge of the membrane of the pore-biomimetic membrane was fixed to the slide glass and the temperature of the membrane was heated from 26 ° C to 36 ° C The holes in the membrane that were closed were opened. As the temperature increased, the circular hole became larger in diameter (see Fig. 4A-c) and the slit-shaped hole became elliptical (see Fig. 4B-d).

Claims (12)

N-isopropylacrylamide (NIPAAm) as a monomer, N, N-methylenebisacrylamide (MBAm) as a crosslinking agent and 2-hydroxy-1- [4- (hydroxyethoxy) -2-methyl-1-propanone (Irgacure 2959);
A step of photopolymerizing the base material to which a solution containing the monomer, the cross-linking agent and the photoinitiator is applied through a photomask having a circular or slit-shaped pattern as a shading part, for one to three minutes to five minutes, A method for producing a simulated membrane,
1 to 3 parts by weight of a crosslinking agent and 0.5 to 2.5 parts by weight of a photoinitiator based on 100 parts by weight of the monomer,
Characterized in that the membrane does not have a bonding site,
Wherein the membrane comprises a polymer membrane comprising a hole, a frame and a base different in physical properties.
The volume expansion ratio of the base is higher than the volume expansion ratio of the frame,
Characterized in that the pore size varies with temperature. The method according to claim 1,
Wherein the exposure is performed using ultraviolet light. delete delete delete A plant leaf pore-simulating membrane prepared by the method of any one of claims 1 or 2. delete delete delete A flow control device comprising the plant leaf porosity mimetic membrane of claim 6. A cooling device comprising the plant leaf porosity mimetic membrane of claim 6 as a cooling performance regulating device. A drug delivery device comprising the plant leaf porosity mimetic membrane of claim 6.

Images