TWI466715B - Method for preparing photochromic structural colors films and its applications - Google Patents

Description

Method and application for preparing photon color-changing film by structural color

The present invention relates to a method and application for preparing a photonic color-changing film in a structural color and applying the same.

As is generally known, the colors we see around the environment are caused by industrial chemical pigments and pigments, which pose a serious threat to human harm and environmental pollution. The color produced by man-made, its color and saturation are not as bright and beautiful as the natural world. Under the influence of environmental factors for a long time, it will face the problem of fading. However, we have found that the brilliant colors produced by some organisms are not caused by self-pigmentation, but by the optical effects of light, such as reflection, interference and diffraction, on the structure of the organism. The color of its structure has been shown to be a brilliant color after hundreds of millions of years of time and environmental influence. The structural color and dazzling iridescence produced by biophotonic crystals are natural optical phenomena. Therefore, in recent years, nanotechnology has attempted to mimic the photonic crystal structure biologically and apply it to many research fields, such as optoelectronic components, fiber optic communication. , display devices, smart sensors, etc. However, most of the photonic crystal technology focuses on LED optoelectronic components and optical fiber transmission technology. However, photonic crystal color display technology and other applications are more in the stage of basic academic research.

Nowadays, the photochromic color display technology uses a photochromic polymer to cause a chemical change in the molecular structure under the action of light of a certain wavelength and intensity, resulting in a change in the absorption peak of light, that is, the color corresponding to the color Change. The photonic color-changing film of this patent generates a physical optical phenomenon by incident light interacting through a nanostructure, and its color can be changed by controlling the angle of incident light and the size of the nanostructure. However light The color of the sub-color film is reversible, and does not need to be maintained by any energy device. Under the influence of external forces such as electric power, pressure, temperature, etc., the color of the structure can be hidden and have a transparent and high-transparency characteristic.

In order to avoid the present invention being the same as the prior patents of others, the inventors searched for a method for preparing a color-changing film of the Republic of China Public Publication No. 201122571 and a photocurable adhesive of the Republic of China Publication No. 20070072, using the related method. Polarizing plate for an adhesive, a method for producing the same, an optical member, and a liquid crystal display device. After careful analysis, it is ascertained that the present invention is different from the prior art techniques.

The object of the present invention is to provide a bionic photonic color-changing film which is prepared by utilizing a special optical phenomenon of a structural color, and is applied to a pseudo-display technology, which is characterized in that it can be produced from a transparent film under visible light without maintenance of electric power or any energy device. The hidden structural color is more convenient than the pseudo-pseudo-pattern recognized by ultraviolet rays, and the high-transparency characteristic is more applicable to the pseudo-pseudo-label.

A technical means for achieving the object of the present invention is to provide a monodisperse colloidal microsphere suspension. The colloidal microspheres in the colloidal microsphere suspension are arranged in a self-assembling manner into a periodic colloidal microsphere array. A liquid permeable colloidal material is infiltrated into the colloidal microsphere array, so that the air between the gaps of the original colloidal microspheres is filled with the liquid permeable colloidal material after being infiltrated and solidified to form a photonic color-changing film. The photonic color-changing film is irradiated under a light source to reveal a structural color.

壹. Basic technical features of the present invention

The method for preparing a photonic color-changing film by structural color according to the present invention has the following basic technical features: (a) providing a monodisperse colloidal microsphere suspension (the microsphere material is selected from the group consisting of metal and organic) At least one of a polymer and an inorganic compound selected from the group consisting of gold Au, silver Ag, copper Cu, iron Fe, Co, nickel Ni, palladium Pd, platinum Pt, aluminum Al, lanthanum Si, titanium Ti, zirconium Zr, At least one of vanadium V, niobium Nb, molybdenum Mo, tungsten W and manganese Mn; the organic polymer material is selected from the group consisting of polystyrene series, polymethyl methacrylate series, polymaleic acid series, polylactic acid series, poly At least one of the amino acid series polymers; the inorganic compound material is selected from the group consisting of silver oxide Ag ₂ O, copper oxide CuO, zinc oxide ZnO, cadmium oxide CdO, nickel oxide NiO, palladium oxide PdO, cobalt oxide CoO, magnesium oxide. MgO, cerium oxide SiO ₂ , tin dioxide SnO ₂ , titanium dioxide TiO ₂ , zirconium dioxide ZrO ₂ , cerium oxide HfO ₂ , cerium oxide ThO ₂ , cerium oxide CeO ₂ , cobalt dioxide CoO ₂ , dioxide manganese MnO _2, iridium oxide IrO _2, vanadium dioxide VO _2, ozone Tungsten, WO _3, molybdenum trioxide MoO _3, aluminum oxide Al ₂ O _3, yttria Y ₂ O _3, ytterbium oxide Yb ₂ O _3, dysprosium oxide Dy ₂ O _3, boron trioxide B ₂ O ₃ , chromium oxide Cr ₂ O ₃ , ferric oxide Fe ₂ O ₃ , ferroferric oxide Fe ₃ O ₄ , vanadium pentoxide V ₂ O ₅ , niobium pentoxide Nb ₂ O ₅ , Zinc sulfide ZnS, zinc selenide ZnSe, zinc iodide ZnTe, cadmium sulfide CdS, cadmium selenide CdSe, cadmium iodide CdTe, iron sulfide FeS, iron selenide FeSe, FeTe, cobalt sulfide CoS, cobalt selenide CoSe, iodization Cobalt CoTe, nickel sulfide NiS, nickel selenide NiSe, NiTe, lead sulfide PbS, lead selenide PbSe, lead iodide PbTe, manganese sulfide MnS, manganese selenide MnSe, MnTe, tin sulfide SnS, tin selenide SnSe, tin iodide SnTe, molybdenum disulfide MoS _2, molybdenum diselenide MoSe _2, molybdenum diiodide MoTe _2, tungsten disulfide WS _2, tungsten diselenide WSe _2, tungsten diiodide WTe _2, copper sulfide Cu ₂ S, Se Cu ₂ Se, Cu ₂ Te iodide, Bi ₂ S ₃ trisulphide, Bi ₂ Se ₃ selenide, Bi ₂ Te ₃ triiodide, Bismuth carbide SiC, Titanium carbide TiC, zirconium carbide ZrC, tungsten carbide WC, niobium carbide NbC, carbon Tantalum TaC, two molybdenum carbide Mo ₂ C, boron nitride BN, aluminum nitride AlN, titanium nitride TiN, zirconium nitride ZrN, vanadium nitride VN, niobium nitride NbN, tantalum nitride TaN, silicon nitride At least one of Si ₃ N ₄ and trizirconium nitride Zr ₃ N ₄ . (The experimental example of the present invention is a polystyrene microsphere suspension emulsion); (b) aligning the colloidal microspheres in the colloidal microsphere suspension into a periodic colloidal microsphere array in a self-assembling manner (the self-assembly method) The method is selected from the group consisting of a dip method, a gravity sedimentation method, a vertical deposition method, a solvent evaporation method, a centrifugal deposition method, a magnetic field accelerated sedimentation method, and an electrophoresis-assisted deposition method, and the experimental example of the present invention is a dip method; and (c) Infiltrating a liquid permeable colloidal material into the colloidal microsphere array (the liquid permeable colloidal material is selected from the group consisting of epoxy resin series, benzil series, alkyl benzophenone series, benzophenone series, benzoin ether) At least one of a series, a thiouranone series and a polydimethyl methoxy oxane series, in the experimental example of the present invention, the liquid permeable colloidal material is a polydimethyl oxyalkylene plate (PDMS), so that the original The air between the gaps of the colloidal microspheres fills the liquid permeable colloidal material after infiltration and solidifies to form a photonic color-changing film, so that the photonic color-changing film can be illuminated under a light source to exhibit structural color.

贰. Experimental example of the present invention

In order to achieve the object of the present invention, the inventors conducted specific experiments in which the polystyrene nanospheres were synthesized by soap-free emulsion polymerization, and the polystyrene microspheres were arranged in a self-assembly manner. An ordered periodic nanostructure, cast and infiltrated into a PDMS colloid into a photonic color-changing film around the self-assembled polystyrene nanospheres.

The specific detailed operation procedures included in the experimental examples of the present invention include: synthesis of polystyrene nanosphere suspension, preparation of PDMS substrate, preparation of photonic color-changing film, analysis of influence of polystyrene nanospheres on structural color, and analysis of self-assembly The effect of the immersion method on the ordering degree and stacking thickness of the polystyrene microspheres and the analysis of the optical properties of the photonic color-changing film are described below.

1. Polystyrene nanospheres synthesize polystyrene microsphere suspension emulsion: In the experimental example of the present invention, polystyrene spheres (PS) of uniform particle size are prepared by soap-free emulsion polymerization method, Add 15 mL of styrene (St) monomer, 10 mg to 100 mg of sodium styrene sulfate (NaSS) co-parent and 135 mL of deionized water (DI water) to the neck reaction flask, and heat up to 70 ° C. The polymerization agent was started at 0.1 g of the starting agent (KPS), and the whole reaction process was carried out for 24 hours under a reflux condenser and a nitrogen atmosphere to synthesize a polystyrene microsphere suspension emulsion. Controlling the content of the p-styrene sulfate (NaSS) co-parent monomer can polymerize polystyrene microspheres of different particle sizes.

2. Polydimethylsiloxane alkylene plate (PDMS substrate) preparation: In the experimental example of the present invention, a PDMS substrate was prepared by uniformly mixing a main agent and a hardener at a mass ratio of 10:1 to form a PDMS prepolymer colloid under vacuum. The bubbles in the PDMS prepolymer gel were removed, and the PDMS prepolymer colloid was cast on the surface of a glass substrate as a PDMS template. The PDMS template was cured after curing at a temperature of 50 ° C for 8 hours, and the hardened PDMS template was applied from the glass substrate. The surface is removed to obtain a PDMS substrate. Since the PDMS substrate obtained in the foregoing step is hydrophobic, the hydrophobic surface of the PDMS substrate is bombarded with a plasma by a plasma cleaner to perform surface modification, so that the surface of the PDMS substrate has a hydrophilic property. A microelectromechanical precision immersion device according to an embodiment of the present invention is shown in the first figure, and the computer controls the step closed loop servo motor 2 via the USB single axis motion controller 1, and the motor bearing shaft rotates the precision of the motor screw coupling 4 The ball screw 5, the optical rotary absolute type encoder 3, moves the linear moving slide 6 of the memory level and the precise positioning precision level to prevent mechanical errors. The test piece clamp group 7 is fixed to the hydrophilic PDMS substrate 8, and the hydrophilic PDMS substrate 8 is immersed in the beaker. The polystyrene suspension 9, the microelectromechanical precision immersion device and the polystyrene suspension 9 are placed on the anti-shock optical table 10.

3. Preparation of photon color-changing film: self-assembly arrangement process of polystyrene microspheres. Referring to the second figure, the surface of the hydrophilic PDMS substrate 8 is pulled out of the surface of the polystyrene suspension 11 by computer controlled immersion rate. A hydrophilic liquid PDMS substrate 8 and a polystyrene suspension 11 will form a meniscus 13 whose capillary force causes the polystyrene microspheres 12 to self-assemble into an ordered polystyrene microsphere colloidal array. 14. The photonic color-changing film of the experimental example of the present invention, as shown in the third figure, casts the ordered polystyrene microsphere colloid array 14 into the PDMS prepolymer 15, and the pores of the polystyrene microsphere colloid array 14 are filled. The PDMS prepolymer 15 was placed in an oven and cured at a heating temperature of 50 ° C. After 8 hours, a photonic color-changing film was taken out.

4. Analysis of the effect of polystyrene nanospheres on the color of the structure: The present invention synthesizes microspheres of different particle sizes, and the structural color is varied by the difference in particle size. As the content of the co-monomer of sodium styrene sulfate (NaSS) increases, the number of microspheres formed at the initial stage of polymerization is large, but the particle size is small. The particle size of the polystyrene microspheres (PS) polymerized without the addition of the sodium styrene sulfate (NaSS) co-parent is about 1155 nm, and the sodium styrene sulfate (NaSS) The content of the co-parent monomer was increased from 10 mg to 100 mg, and the particle size of the polystyrene microsphere (PS) was decreased from 377.4 nm to 116.6 nm, as shown in Fig. 2(a). The size of the microspheres of the polystyrene microspheres (PS) polymerized by different co-monomer content of sodium styrene sulfate (NaSS) and the color corresponding to the reflection are as shown in Fig. 2(b). . When the content of co-monomer of sodium styrene sulfate (NaSS) is between 20 and 80 mg, the average particle size of polystyrene microspheres (PS) is between 310 nm and 145 nm to show the red to blue color. ,As shown in Table 1.

5. Analysis of the effect of self-assembly immersion method on the ordering degree and stacking thickness of polystyrene microspheres: in order to observe the surface morphology of polystyrene microspheres (PS) formed by self-assembly at different immersion rates, We chose polystyrene microspheres (PS) to have a particle size of 258 nm. The polystyrene microsphere suspension was diluted to a concentration of 10% by weight with pure water, and self-assembled at a leaching rate of 1000 to 0.1 μm/s. It was found by SEM observation that at a faster immersion rate, such as 1000-100 μm/s, as shown in the ninth figure (a-b), the arrangement of the polystyrene microspheres (PS) showed a disordered structure. The PDMS substrate is rapidly pulled out of the surface of the polystyrene microsphere suspension while the van der Waals attraction and electrostatic repulsion between the polystyrene microspheres (PS) are at the interface of the polystyrene microsphere suspension and air. The unbalanced state causes the polystyrene microspheres (PS) to be arranged in a disorderly manner. At a medium immersion rate of 10~1μm/s, since the polystyrene microspheres (PS) have enough time to achieve a better equilibrium between the electrostatic repulsion of the surface and the van der Waals attraction, the ninth figure ( Cd) It can be observed that the arrangement of polystyrene microspheres (PS) is tight, but there are still local line defects and vacancies. The ninth figure (e) shows a uniform and orderly periodic structure of polystyrene microspheres (PS) at a very slow immersion rate of 0.1 μm/s.

Due to the fact that at 10% by weight of the suspension concentration, it is difficult to observe the stack thickness and stacking level of polystyrene microspheres (PS) at different immersion rates from the longitudinal section, in order to make the stack thickness of the polystyrene microspheres (PS) There is a significant difference, so we adjusted the concentration of the polystyrene microsphere suspension to 50% by weight. At a decreasing leaching rate of 1000 → 100 → 10 → 1 → 0.1 μm / s, the stack thickness of polystyrene microspheres (PS) (see Figure 9 (fj)) is from 0.487 → 0.825 → 2.953 → 25.36 →330.9 μm gradually increased. From the comparison of the longitudinal profile (such as the ninth figure (fj)) and the top view (such as the ninth figure (ae)), it is found that the faster the immersion rate (above 100 μm/s), the polystyrene microspheres are not self-assembled. Arranged in disorder, the thickness of the stack is thin. When the immersion rate is slow (10 μm/s or less), the polystyrene microspheres (PS) have sufficient time to self-assemble in an ordered periodic structure, and the thickness of the stack is thicker.

6. Analysis of photonic color film optical properties:

(1) Reflection spectrum

The reflectance of self-assembled microspheres prepared by polystyrene microspheres (PS) at a immersion rate of 1 μm/s on a PDMS substrate at 258 nm polystyrene microspheres (PS) at different polystyrene microsphere suspension concentrations (R%) change (see figure 4). As the polystyrene microsphere suspension concentration increases from 20 wt% to 100 wt% (see Figure 4 (ae)), the reflectance (R%) decreases from 33.8% to 10.1%, and its reflection peak shifts from 522 nm to 497nm is blue-shifted. The thickness of the polystyrene microsphere (PS) stack on the PDMS substrate is the main cause of the reflectance R%. Since the polystyrene microsphere suspension is in the form of a white emulsion, the polystyrene microspheres (PS) are also arranged in a white color on the PDMS substrate. However, when the polystyrene microsphere suspension concentration is increased to 100% by weight, the polystyrene on the PDMS substrate The thickness of the olefin microsphere stack is also increased, causing light to scatter between the polystyrene microspheres, and the reflectance R% is also reduced. The blue shift phenomenon is caused by the large difference in refractive index between polystyrene microspheres (PS) (n=1.6) and air (n=1), resulting in strong scattering of light, resulting in reflection peak drift.

The reflection spectrum of the photonic color-changing film, as shown in the fifth figure, increases with the polystyrene microsphere suspension concentration from 20 wt% to 100 wt%, and the reflectance (R%) decreases from 8.8% (as shown in Fig. 6(a)). To 2.7% (as in Figure 5 (e)), the reflection peak positions are all around 531 nm. The reflectivity of the infiltrated PDMS prepolymer before the polystyrene microspheres was 33.8%, and the reflectance decreased to 8.8% after infiltration of the PDMS prepolymer into the polystyrene microspheres (PS). The light passes through the photonic color changing film to cause total reflection. According to Snell's Law light entering the light-draining medium air (n=1) from the optically dense medium PDMS (n=1.43), when the incident angle is larger than the critical angle (θc=44.4°), total reflection is caused. However, the reflection peak of the photonic color-changing film does not affect the concentration of the suspension of the polystyrene microspheres, because the photonic color-changing film has a matching refractive index between the polystyrene microspheres (PS) and the PDMS, resulting in a reflection peak. Both fall near 531nm.

(2) Penetration spectrum

The light illuminates the polystyrene microspheres (PS) arranged on the PDMS template to produce reflection and refraction. From the breakthrough spectrum of the sixth graph, a photonic band gap is formed, that is, the light is reflected because it cannot propagate. When the polystyrene microsphere suspension concentration was increased from 20 wt% to 100 wt%, it was found from the sixth graph (ae) that the average transmittance decreased from 77.5% to 8.3%. As the concentration of polystyrene microsphere suspension increases, the polystyrene microspheres self-assemble the thicker the stack thickness, due to the accumulation of light on the PDMS substrate. Scattering between styrene microspheres results in reduced optical transmittance.

The average transmittance of the polystyrene microspheres in the photonic color-changing film due to the filling of the PDMS prepolymer is shown by the seventh diagram (ae) when the polystyrene microsphere suspension concentration is increased from 20 wt% to 100 wt%. From 95.2% to 31.2%. Here, the highest average transmittance of the polystyrene microsphere suspension concentration before and after pouring the PDMS template into the PDMS prepolymer is 20 wt%. The average penetration of polystyrene microspheres on the PDMS substrate before pouring the PDMS prepolymer was 77.5% (as in Figure 6 (a)), and the penetration rate increased significantly to 95.2% after casting (as in the seventh Figure (a)), the reason for this high transmittance is the optical properties of the PDMS material itself. After the incident light is refracted and multi-reflected by the polystyrene microspheres in different directions, most of the light cannot penetrate from the polystyrene microsphere (PS) colloidal crystal, which gives a white vision. After the infiltration of the PDMS prepolymer, the light enters the photonic color-changing film and collides with the polystyrene microspheres (PS) to cause scattering. The scattered light travels along the microspheres forward, and the PDMS itself has high penetration characteristics. Light penetrates the photonic color-changing film, thereby increasing the transmittance of the photonic color-changing film.

We use a banknote as the background, and there is a laser-like pseudo-pattern on the right side of the banknote, and then the photonic color-changing film prepared by the experiment of the present invention is placed on the banknote, as shown in the tenth figure (a). It can be observed that its high penetrating property, after tilting the banknote, the photonic color-changing film will reflect the hidden structure color inside, which can clearly see a green letter "U" and a blue letter "N". Displayed on the photonic color film as shown in the tenth (b). The laser-like pseudo-bar on the right side of the banknote is posted on the typeface, causing the text in the overlapping area of the banknote to be covered by the dummy strip. But photon change The color film has a 95% high penetration property, and the image on the banknote is clearly visible when it is covered on the surface of the banknote. The photonic transparent film will reflect the hidden structure color under any visible light source, and the photonic transparent film can change its color and pattern. The pseudo-pseudo-facilitability is higher than the hidden design illuminated by the ultraviolet light source. It can be applied to the potential of pseudo-pseudo, hidden encrypted files and developed into special decorative coatings.

Reference

According to the foregoing description and analysis, the present invention does have the following technical features and effects:

1. The color display technology of the present invention does not cause a chemical change after the material absorbs light, but a physical optical phenomenon generated by the interaction between the nanostructure and the incident light, and the photochromic process does not need any The energy device or drive produces a color transition, which is a special optical property of the structural color.

2. The photonic color-changing film of the present invention has a high optical transmission characteristic of about 95%, but has a hidden structural color appearance at the same time, that is, changes from a transparent film to a color film.

3. The present invention uses the dip-draw method to cause the polystyrene microspheres to self-assemble into an ordered structure, but the polystyrene microspheres can be stacked in different shapes under different dip-drawing rates and polystyrene suspension concentrations. And thickness, affecting its penetration and color intensity.

4. The structural color can be controlled by the particle size of the polystyrene microspheres, and the polydimethylsiloxane (PDMS) is infiltrated between the gaps of the polystyrene microspheres and cured, in addition to enhancing the mechanical strength of the film. It also increases optical penetration.

The above description is only one of the possible embodiments of the present invention, and is not intended to limit the scope of the patent of the present invention, and the content, characteristics and fineness thereof according to the following claims are mentioned. The equivalent implementation of God's other changes shall be included in the scope of this creation's patent. In addition to the above advantages, this creation has deep industrial applicability, can effectively improve the lack of use, and is specifically defined in the characteristics of the request item, not found in similar items, so it is practical and progressive, and has been in line with the new type. For patents, the application shall be filed in accordance with the law. The Bureau shall be required to approve the patent in accordance with the law to protect the lawful rights and interests of the applicant.

1‧‧‧USB single axis motion controller

2‧‧‧Step closed loop servo motor

3‧‧‧Optical rotary absolute encoder

4‧‧‧Motor screw coupling

5‧‧‧Precision ball screw

6‧‧‧Precision linear moving slide

7‧‧‧Film holder

8‧‧‧PDMS substrate

9‧‧‧ beaker

10‧‧‧Anti-vibration optical table

11‧‧‧ polystyrene suspension

12‧‧ ‧ polystyrene microspheres

13‧‧‧ Meniscus

14‧‧‧colloid array

15‧‧‧PDMS prepolymer

The first figure is a schematic diagram of a microelectromechanical precision immersion device used in the present invention.

The second figure is a schematic diagram of the self-assembly alignment process of the polystyrene microspheres of the present invention.

The third figure is a schematic diagram of the photonic color-changing film of the present invention.

The fourth graph is the reflection spectrum of the polystyrene microsphere suspension concentration on the PDMS substrate varying from 20 wt% to 100 wt%.

The fifth figure is the reflection spectrum of the photochromic color film polystyrene microsphere suspension concentration change of 20 wt% to 100 wt%.

The sixth graph is the breakthrough spectrum of the polystyrene microsphere suspension concentration on the PDMS substrate varying from 20 wt% to 100 wt%.

The seventh figure shows the breakthrough spectrum of the photochromic color film polystyrene microsphere suspension concentration of 20 wt% to 100 wt%.

The eighth figure shows the size of the microspheres of the polystyrene microspheres (PS) polymerized by different NaSS content and the wavelength (color) corresponding to the reflection.

The ninth diagram (a-b) is an SEM observation of the arrangement structure of polystyrene microspheres (PS) at different immersion rates by SEM; (f-j) is the polyphenylene of the invention at a decreasing immersion rate. Stacking thickness of ethylene microspheres (PS).

Figure 11 (a) shows the photonic color-changing film prepared by the experiment of the present invention placed on the banknote; the photograph (b) shows the hidden structure color of the banknote obliquely reflected by the banknote of the present invention, and the letters "U" and " The appearance of N".

8‧‧‧PDMS substrate

9‧‧‧ beaker

11‧‧‧ polystyrene suspension

12‧‧ ‧ polystyrene microspheres

13‧‧‧ Meniscus

14‧‧‧colloid array

Claims (3)

A method for preparing a photonic color-changing film in a structural color, comprising the steps of: (a) providing a monodisperse colloidal microsphere suspension; and (b) allowing the colloidal microspheres in the colloidal microsphere suspension to be self-assembled. Arranging into a periodic colloidal microsphere array; and (c) infiltrating a liquid permeable colloidal material into the colloidal microsphere array, so that the air between the gaps of the original colloidal microspheres is filled with the liquid after permeation The colloidal material is solidified to form a photonic color-changing film, and the photonic color-changing film is irradiated under a light source to exhibit a structural color, wherein the colloidal microsphere suspension is a polystyrene microsphere suspension, and the concentration thereof is 20wt% to 100wt%, the self-assembly method is a immersion method, the immersion method is used to immerse and pull a hydrophilic PDMS substrate on the surface of the polystyrene suspension at a leaching rate, by capillary The force causes the polystyrene microspheres to self-assemble into an ordered array of polystyrene microspheres having a immersion rate of 100 to 0.1 [mu]m/s. The liquid permeable colloidal material is a PDMS prepolymer. The method of claim 1, wherein the microspheres of step (a) have an average particle size of between 100 nm and 500 nm. The method of claim 1, wherein the liquid permeable colloidal material is selected from the group consisting of epoxy resin series, alkyl benzophenone series, benzophenone series, benzoin ether series, thiocyanate series and At least one of the polydimethyl siloxane series.