KR101197117B1 - Dry adhesives and fabrication method thereof - Google Patents

Abstract

The present invention relates to a dry adhesive in which an inclined nanopolymer structure having double-sidedness (Janus) functions as an adhesive. The dry adhesive of the inclined nanostructure is manufactured using an electron beam or a specially manufactured dry etching equipment. Unlike the conventional method, after forming the nano-polymer structure on the substrate to form a metal layer on one side wall of each structure, and then performing a heat treatment process or forming a metal layer having a predetermined angle of inclination of the nano-polymer structure By deforming to the inclined nanopolymer structure, it is possible not only to realize a strong adhesive force while making uniform contact irrespective of the surface roughness of the adhesive object, but also to realize a large area of the dry adhesive.

Description

Dry adhesive and its manufacturing method {DRY ADHESIVES AND FABRICATION METHOD THEREOF}

TECHNICAL FIELD The present invention relates to a dry adhesive, and more particularly, to a dry adhesive in which an inclined nanopolymer structure having double-sided (janus) functions as an adhesive and a manufacturing method thereof.

When classifying general adhesives into several types, they can be divided mainly by the way the adhesive is applied and hardened in the liquid state.

First, the most commonly encountered glue or woodworking adhesives, multipurpose adhesives (collectively, "pig bonds"), phenolic adhesives, or solvent evaporative adhesives where solvents evaporate. In other words, a sticky solution or emulsion is an adhesive that dries and hardens.

Secondly, pressure sensitive adhesives, which are rare for adhesives, are often applied to cellophane tape. These adhesives are in such a way that the surface is kept sticky like mucus and the adhesive state is maintained according to its viscosity. There is also a heat-sensitive adhesive that melts after heat and hardens, such as a glue gun.

Third, there are chemically reactive adhesives that differ in state before and after use.

However, all of the conventional adhesives mentioned above have the disadvantage that easy detachment and detachment are not possible, and also have the disadvantage of contaminating another surface (the surface of the object to which the adhesive is adhered) after detachment.

Therefore, although an adhesive for easy desorption may be considered, such an adhesive has a problem in that its applicability is significantly lowered because its adhesive ability is also lowered in proportion to easy desorption.

Research into the tilted nanostructures inspired by gecko lizards can be used as dry glue for the same reason as described above is being conducted around the world.

This dry adhesive is characterized by the fact that numerous micro and nanometer sized structures are formed to have a relatively large surface area at the time of adhesion, which improves adhesion, and is also directional, due to the pull of gravity in the direction of gravity. While the adhesiveness is strong, when the pull in the opposite direction, the adhesive strength is relatively good and has the advantage of being able to move in one direction without residue.

Therefore, in order to imitate such adhesive properties, methods for improving adhesion by forming a structure having a high aspect ratio pattern having a nanometer size have been developed, and as a method for giving directionality, a structure using an electron beam is used. The method to bend in one direction and a special modification of dry etching equipment to create a bent structure and to use it as a master to create a bent polymer structure has been developed representatively.

However, the conventional dry adhesive has a fundamental problem that it is difficult to manufacture a large area due to problems in the manufacturing method, and also has a problem that the manufacturing cost significantly increases because the dry etching equipment must be specially manufactured.

In addition, the conventional dry adhesive has a problem that the adhesion repeatability is remarkably inferior when the modulus such as metal is relatively large.

According to an aspect, the present invention provides a substrate, a plurality of inclined nanopolymer structures formed on the substrate and inclined at a predetermined angle, and respectively formed on one side wall of the plurality of inclined nanopolymer structures. Provided is a dry adhesive comprising a plurality of metal layers.

According to another aspect of the present invention, there is provided a process of forming a plurality of nanopolymer structures on a substrate, a process of selectively forming a metal layer on each side wall of the plurality of nanopolymer structures, and a heat treatment process. By tilting the plurality of nanopolymer structures at a predetermined angle, it provides a method of manufacturing a dry adhesive comprising the step of transforming into a plurality of slanted nanopolymer structures.

According to another aspect of the present invention, there is provided a process of forming a plurality of nanopolymer structures on a substrate, and selecting a plurality of nanopolymer structures while forming a metal layer on each side wall of the plurality of nanopolymer structures. It provides a method for producing a dry adhesive comprising the step of transforming into a plurality of inclined nano-polymer structure inclined at a predetermined angle.

The present invention is a method of depositing a polymer and other materials (for example, metal) on one side surface of the nanopolymer structure through a diagonal deposition method, and by modifying the nanopolymer structure into an inclined nanopolymer structure at the same time as the subsequent heat treatment process or deposition. By producing a dry adhesive, strong adhesive force can be realized while making uniform contact irrespective of the surface roughness of an adhesion object.

In addition, the present invention can be realized by a simple method of transforming the nanopolymer structure into the inclined nanopolymer structure simultaneously with the subsequent heat treatment process or deposition, thereby realizing a large area of the dry adhesive.

The technical idea of the present invention differs from the above-described conventional method of manufacturing a dry adhesive of a slanted nanostructure by using an electron beam or a specially manufactured dry etching apparatus. The metal layer is formed on one side surface of the olfactory structure, and then a heat treatment process is performed to transform the plurality of nanopolymer structures into the inclined nano polymer structures having a predetermined angle of inclination. Problems in the prior art can be effectively improved.

In addition, the present invention, unlike the above, may include another technical idea of transforming the nanopolymer structure into the inclined nanopolymer structure simultaneously with the formation of the metal layer.

Here, the metal layer may be formed by a diagonal deposition method, for example, a deposition process for performing vacuum sputtering or vacuum evaporation while tilting the substrate on which the nanopolymer structure is formed at a predetermined angle. The nanopolymer structure may be formed on one side wall in the inclined direction or one side wall in the inclined direction.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

1A to 1F are process flowcharts illustrating a main process of manufacturing a dry adhesive having an inclined nanopolymer structure according to a first embodiment of the present invention.

Referring to FIG. 1A, a master mold 102 having a hole pattern 104 is prepared. The hole pattern 104 of the master mold 102 may be a substrate (eg, a photolithography process or the like) well known in the art. , Silicon or silicon oxide, or the like).

Subsequently, the surface treatment can optionally be carried out so that the substrate having the nanopolymer structure to be formed on the master mold can be easily removed from the master mold through a subsequent process, such surface treatment being, for example, the surface energy of the master mold. In order to lower the, it may be carried out by a self-assembled monomolecular treatment including a fluorine or hydrocarbon functional group or Teflon treatment on the surface.

Here, the master mold 102 may be made of a relatively hard material or a relatively flexible material, when the substrate having the inclined nano hair structure to be formed on the master mold through a subsequent process is a relatively flexible material The master mold may be made of a relatively hard material, and when the substrate having the inclined nano hair structure is a relatively hard material, the master mold may be made of a relatively flexible material. That is, in the present invention, one of the master mold and the substrate is made of a relatively flexible material, thereby inducing easy detachment from each other.

Next, as an example, as shown in FIG. 1B, a photocurable (UV photocurable) polymer material, such as PUA (precursor polyurethane), may be formed on the master mold 102 on which the hole pattern 104 is formed through a nano molding technique or the like. acrylate, 301RM, and Minuta Tech) (that is, the polymer is embedded in the hole pattern 104) to form a reinforcement plate 108 on the polymer substrate 106 to block oxygen from contacting the polymer. Glue.

Again, the polymer substrate 106 having the nanopolymer structure 110a is cured by irradiating UV light to the polymer substrate 106 side through the reinforcing plate 108, and then the polymer substrate 106 is removed from the master mold 102. As an example, as illustrated in FIG. 1C, the adhesive structure 112a on which the plurality of nanopolymer structures 110a having a vertical shape is formed on the polymer substrate 106 is completed.

In addition, as an example, as shown in FIGS. 1D and 1E, the adhesive structure 112a is fixed to the inclined surface of the holder 114 having the inclined surface at a predetermined angle, and then a plurality of processes are performed by a deposition process such as vacuum sputtering. The metal layer 116 of the thin film is formed on one wall of the nanopolymer structure 110a. That is, in this embodiment, the metal layer is selectively formed on one side wall of the plurality of nanopolymer structures by vacuum sputtering while the adhesive structure is inclined at a predetermined angle.

Here, the metal layer 116 formed on one wall surface of each nanopolymer structure 110a may be any one or two or more of Au, Pt, Cr, Cu, Al, Fe, Co, and Ni.

Next, a heat treatment process (annealing process) is performed on the adhesive structure 112a on which the plurality of nanopolymer structures 110a are formed, so that each nanopolymer structure 110a is inclined at a predetermined predetermined angle. As shown in FIG. 1F, a plurality of warped nanopolymer structures 110 are transformed. That is, the dry adhesive 112 of the reinforcement plate 108, the polymer substrate 106, and the plurality of inclined nanopolymer structures 110 is completed. Here, the inclination angle (deformation or inclination degree) of the inclined nanopolymer structure 110 may be determined by heat treatment process conditions such as heat treatment temperature, heat treatment time, and the like.

Meanwhile, in the present embodiment, the inclined nano polymer structure is bent in the direction in which the metal layer is formed through the heat treatment process, but this is merely illustrative and the present invention is not necessarily limited thereto. That is, the two materials forming the warp-shaped nanopolymer structure, that is, the polymer and the metal, have different thermal expansion coefficients. When the temperature increases according to the heat treatment process, the structure is bent toward the smaller thermal expansion coefficient. That is, when the thermal expansion coefficient of the polymer is smaller than the thermal expansion coefficient of the metal, the structure is bent in the direction in which the metal layer is not formed, and when the thermal expansion coefficient of the metal is smaller than the thermal expansion coefficient of the polymer, the structure is bent in the direction in which the metal layer is formed.

2 is a schematic diagram of the results of the shearing test (hanging test) according to the direction using the nano-polymer structure having Janus characteristics.

Referring to FIG. 2A, it is an image of a nanopolymer structure standing in a vertical form without being bent in one direction. However, when the measurement is performed by changing the direction and bending it in one direction, the nano polymer structure exhibits different characteristics depending on the direction. .

In order to test the shear stress, the inventors measured an area of 1 cm × 1 cm using a preload of about 0.3 N and then measured the shear stress without the preload.

Referring to FIG. 2B, the inventors of the present invention have a shear stress of 20 N / cm 2 when the polymer surface is in contact with the glass plate that is the target surface, and the shear surface is 10 N / cm 2 because the metal surface is in contact with the glass plate when pulled in the opposite direction. It was clear that the stress was measured.

Figure 2c schematically shows the above test, in order to explain these results, the inventors of the present invention found the adhesion energy at the interface. That is, the adhesion energy was obtained through the harmonic mean equation (W ₁₂ ) as shown in Equation 1 below using the contact angle of each material.

[Equation 1]

In the above Equation 1, the subscripts d and p represent the dispersion and polar components of the surface energy, respectively, and the adhesion energy at the two interfaces obtained using Equation 1 is W _{pt_glass} = 107 mJ, respectively. / _M 2 and W _{PUA_glass} = 126 mJ / m 2. As can be seen from this result, it is difficult to explain the difference of shear stress according to the adhesive material by using only the adhesive energy, which is very large (modulus of 150 GPa or more for Pt or metal, but 19.8 MPa for polymer). This is because it is small and it is advantageous to cover the entire surface during adhesion.

[Example 2]

Figures 3a to 3d is a process flow diagram illustrating the main process of manufacturing a dry adhesive having a slanted nanopolymer structure according to a second embodiment of the present invention.

Referring to FIG. 3A, an adhesive structure including a reinforcing plate 308, a polymer substrate 306, and a vertical nano-polymer structure 310a may be formed by performing a series of processes as described with reference to FIGS. 1A and 1B of Embodiment 1 described above. Complete (312a).

Next, the adhesive structure 312a is fixed to the inclined surface of the holder 314 having the inclined surface at a predetermined angle, and then a deposition process, for example, a vacuum evaporation, is performed to form one wall surface of the plurality of nanopolymer structures 310a. A thin metal layer 316 is formed on the substrate. That is, in this embodiment, the vacuum evaporation is performed while the adhesive structure is inclined at a predetermined angle to selectively form a metal layer on one side wall of the plurality of nanopolymer structures.

Herein, the metal layers 316 formed on one side wall of each nanopolymer structure 310a may be any one of Au, Pt, Cr, Cu, Al, Fe, Co, and Ni, as in Example 1 described above. Or two or more composites.

At this time, the metal layer 316 selectively deposited on one wall surface of the nanopolymer structure 310a has a compressive stress or a tensile stress according to the characteristics of the metal. The direction in which the structure is bent changes.

For example, in the case of metals such as Au, since the stress has a compressive stress, the structure is bent in the direction of the metal layer due to the force of the metal gathering as it cools (FIG. 3c), whereas in the case of a metal such as Al, the stress is an extensional stress. Since the metal is bent in the direction in which it expands while cooling, it is bent in the polymer direction (the direction opposite to the metal layer) (FIG. 3D).

That is, in the present embodiment, unlike the above-described Embodiment 1 in which the nanopolymer structure is transformed into the inclined nanopolymer structure through a separate heat treatment process, the inclined while cooling the adhesive structure 312a after the evaporation process. By deforming to the type nanopolymer structure 310, as shown in FIGS. 3C and 3D, for example, the structure is bent (tilt) or the metal layer 316 is formed in the direction in which the metal layer 316 is formed on one wall. It is possible to produce a dry adhesive 312, the structure is bent in a direction that is not.

FIG. 4 is a SEM photograph of a dry adhesive on which an inclined nanopolymer structure is formed according to a second embodiment of the present invention. FIG. 4A is a photograph of a test result in which the inclined nanopolymer structure is bent in a direction in which a metal layer is formed. 4B is a photograph of an experimental result in which the inclined nanopolymer structure is bent in a direction in which a metal layer is not formed, and the inventors of the present invention form a shape in which the structure is bent in a desired direction through a simple vacuum evaporation process. It turned out that the dry adhesive which has can be manufactured.

[Experimental Example]

The inventors of the present invention performed a performance test for the dry adhesive prepared according to Example 1 of the present invention, the test results are as follows.

First, when the thermal expansion coefficient increases with respect to two materials, the thermal expansion coefficient may be bent toward the smaller side. The bent nanostructures have good adhesive properties, and the smaller the angle of bending, the smaller the effective Young's modulus. As a result, the area of contact becomes wider and the adhesive force increases relatively.

5a is a SEM photograph of the nanopolymer structure fabricated by performing a heat treatment process for 30 minutes at a temperature of 120 ℃. Here, the metal is deposited on the left side of each structure in the picture, it can be seen that the structure is bent in the metal direction.

Referring to FIG. 5A, the larger the angle θ is, the more deflected the structure is. When the heat treatment is not performed, the angle θ becomes 90 degrees, which means that the structure is not bent and stands vertically.

5b is a SEM photograph of the nanopolymer structure fabricated by performing a heat treatment process for 30 minutes at a temperature of 140 ° C. Referring to this, it can be clearly seen that the higher the heat treatment temperature, the greater the degree of warpage of the structure.

Referring to FIG. 5B, it can be seen that a phenomenon in which the end (end) of the structure is bent downward while the warpage becomes relatively large, in this case, adversely affects the adhesive force of the dry adhesive, so that the temperature condition of the heat treatment process It can be seen that it is necessary to adjust the appropriately.

5c is a graph showing the angle at which the structure is bent as a function of the thickness of the metal deposited on the structure and the heat treatment temperature. The higher the temperature, the more the structure is bent, and the thicker the metal, the greater the degree of support. It can be seen that.

In order to obtain this quantitatively, a curvature, which is a degree of bending, was obtained using a simple bimetal elastic model, as shown in Equation 2 below.

&Quot; (2) "

Where r is the radius of curvature, E _eff is the effective modulus (E _p : PUA modulus, E _m : Pt modulus), t is the total thickness (= t _p + t _m , t _p : PUA thickness, t _m : Pt thickness), ΔT represents the change in temperature, and α _p and α _m represent the thermal expansion coefficients of the polymer and the metal, respectively. In addition, the effective modulus can be calculated as shown in Equation 3 below.

&Quot; (3) "

Using the above equations (2) and (3), the degree of warp with respect to Pt at a thickness of 6 and 12 nm was obtained. For this purpose, α _m = 9 × 10 ^-6 K ^-1 and α _p used 250 × 10 ^-6 K ^-1 as a fitting parameter. Looking at Figure 5c it can be seen that the experimental results and the predicted values fit well. However, as the temperature increases, the plastic deformation increases, and thus the elastic theory cannot be predicted.

Next, the inventors of the present invention measured the shear stress using this curved double-sided polymer structure, the results are shown in Figure 5d. That is, when the bending angle is 70 degrees, the shear stress in the polymer direction is 31 N / cm 2, but in the opposite direction, the shear stress is very small at 4.1 N / cm 2, which is very large at 7.5. Therefore, it can be seen that when the angle is high, this ratio becomes smaller, and when the angle is 70 degrees, the ratio is the largest. However, in the case of an angle of 40 degrees, the tip is bent downward, and thus the adhesive strength is also decreased, and the ratio of the adhesion strength according to the orientation is also reduced, indicating that it is not advantageous to be used as a dry adhesive.

In order to explain the directionality of the shear stress, it was explained using the equation proposed by Kendall. Assuming that the end of the nanostructure is in contact with the target surface, the critical peel-off force per unit area, F _c, is obtained as in Equation 4 below.

&Quot; (4) "

In Equation 4, g denotes an adhesive energy, θ denotes a peel-off angle, E _eff denotes an effective modulus, b and t denote a width and a thickness of the nanostructure, and D denotes a density of the nanostructure. In this case, when the material properties of the structure using the polymer are substituted (g = 126 mJ / ㎡, b = 100 nm, t = 100 nm and D = 4 × 10 ⁸ cm ^-2 . E _eff = 150 MPa) At 30 degrees, 90 degrees, and 110 degrees, they become smaller at 31, 5, and 3.7 N / cm 2, respectively. The results of FIG. 5D can be explained using this. When the bending angle is 70 degrees, the initial peel-off force is 7.6 N / cm ^2, but as the pulling angle becomes smaller, the adhesive force increases. So, when the pull in the direction of the polymer at 70 degrees, 78 degrees can be explained that the adhesion is similar. However, when the angle is increased and bent in the opposite direction by more than 90 degrees, the falling force gradually decreases, and when it is 70 degrees, it falls off more quickly, and the ratio of the direction of the adhesive force gradually increases.

In the above description has been described by presenting a preferred embodiment of the present invention, but the present invention is not necessarily limited to this, and those skilled in the art to which the present invention pertains within a range without departing from the technical spirit of the present invention It will be readily appreciated that branch substitutions, modifications and variations are possible.

1a to 1f is a process flow chart showing the main process of manufacturing a dry adhesive having a sloped nanopolymer structure according to a first embodiment of the present invention,

Figure 2 is a result of the shear test (hanging test) according to the direction using a nano-polymer structure having Janus properties (schematic diagram)

3a to 3d is a process flow chart showing the main process of manufacturing a dry adhesive having a sloped nanopolymer structure according to a second embodiment of the present invention,

4A and 4B are SEM photographs of the dry adhesive having the slanted nanopolymer structure formed according to the second embodiment of the present invention.

Figure 5a is a SEM image of the nano-polymer structure produced by performing a heat treatment process for 30 minutes at a temperature of 120 ℃,

Figure 5b is a SEM photograph of the nano-polymer structure produced by performing a heat treatment process for 30 minutes at a temperature condition of 140 ℃,

5c is a graph showing the angle at which the structure is bent as a function of the thickness of the metal deposited on the structure and the heat treatment temperature;

Figure 5d is a schematic table of the results of measuring the shear stress using a polymer structure having a curved double-sided.

Description of the Related Art

106: polymer substrate 108: reinforcement plate

110a, 310a: nano polymer structure 110, 310: sloped nano polymer structure

112a, 312a: adhesive structure 112, 312: dry adhesive

116, 316: metal layer

Claims (11)

A substrate; A plurality of inclined nanopolymer structures formed on the substrate and inclined at a predetermined angle; A plurality of metal layers each formed on one side wall of the plurality of inclined nanopolymer structures Dry adhesive comprising a. The method of claim 1, The plurality of metal layers, dry adhesive, characterized in that each formed on the opposite side wall surface in the inclined direction or one side wall surface in the inclined direction. The method of claim 2, The plurality of metal layers, Au, Pt, Cr, Cu, Al, Fe, Co, Ni, dry adhesive, characterized in that at least two or more composites. Forming a plurality of nanopolymer structures on a substrate, Selectively forming a metal layer on each side wall of the plurality of nanopolymer structures; A process of transforming the plurality of nanopolymer structures into a plurality of inclined nanopolymer structures by performing a heat treatment process to incline the plurality of nanopolymer structures at a predetermined angle. Dry adhesive manufacturing method comprising a. 5. The method of claim 4, The metal layer is a dry adhesive manufacturing method, characterized in that formed through a diagonal deposition method. 6. The method of claim 5, The diagonal vapor deposition method is vacuum sputtering performed by tilting the substrate at a predetermined angle. The method according to any one of claims 4 to 6, The metal layer is Au, Pt, Cr, Cu, Al, Fe, Co, Ni, any one or two or more composites of the dry adhesive manufacturing method characterized in that. Forming a plurality of nanopolymer structures on a substrate, A process of transforming the plurality of nanopolymer structures into a plurality of inclined nano polymer structures inclined at a predetermined angle while selectively forming a metal layer on each side wall of the plurality of nanopolymer structures. Dry adhesive manufacturing method comprising a. 9. The method of claim 8, The metal layer is a dry adhesive manufacturing method, characterized in that formed through a diagonal deposition method. The method of claim 9, Said diagonal deposition method is a vacuum evaporation performed by inclining the said board | substrate at a predetermined angle, The dry adhesive manufacturing method characterized by the above-mentioned. 11. The method according to any one of claims 8 to 10, The metal layer is Au, Pt, Cr, Cu, Al, Fe, Co, Ni, any one or two or more composites of the dry adhesive manufacturing method characterized in that.

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