Patent Description:
Antireflective surfaces may enhance performance of display devices, such as characteristics relating to screen clarity when observed under uneven light environments, or to transmission of transparent covers for optical devices (e.g., sensors, cameras, etc.) under difficult light conditions. In recent years, much effort has been applied to design optimized anti-reflective and self-cleaning surfaces. Complex micro-scale and nano-scale geometries in nature have been studied and developed, for example, biomimetic sub-wavelength structures inspired by the moth-eye or the lotus leaf, due to their optical performance and potential low cost.

Currently available commercial antireflective solutions include thin films based on destructive interference of multiple reflections. These technologies often suffer from narrow wavelength and angular response, sensitivity to film thickness variations, thermal expansion mismatch, reduced substrate adhesion and susceptibility to scratching. As a result, these films are unable to provide the desired range of optical properties (e.g., high optical transmission, low omnidirectional reflection, etc.) and wetting properties (e.g., superhydrophobicity, oleophobicity, etc.). Moreover, much effort has been made to create nanostructures in different materials; however, difficulties arise in commercial scalability because current technology is produced using expensive and time-consuming lithographic techniques.

This disclosure presents improved anti-reflective transparent oleophobic surfaces and methods of manufacturing thereof. <CIT> relates to oleophobic glass articles and methods of making the same. <CIT> is directed to articles with monolithic, structured surfaces and methods of making the same.

The present invention relates to a method for fabricating a structured surface, comprising: providing a transparent substrate; disposing a dewettable film over the substrate; annealing the dewettable film to form a plurality of islands; forming a coating over the plurality of islands; and etching the plurality of islands to form a structured array of surface features in the coating; transferring the structured array of surface features from the coating to the substrate; and removing the coating. The coating is a dewettable coating comprising at least one of: metals, alloys, metal oxides, polymers, organic materials, metal nitrides, or combinations thereof.

The invention further relates to a structured polymer and/or structured glass, comprising: a structured array of surface features fabricated by the above method, wherein the structured array of surface features has at least one dimension in a range of <NUM> to <NUM>.

The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, in which:.

Reference will now be made in detail to exemplary embodiments which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the exemplary embodiments. It should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures.

Referring now to the figures, <FIG> illustrate a structured polymer fabrication process <NUM>. In a first step of <FIG>, a transparent substrate <NUM> (e.g., glass, glass-ceramic, etc.) is uniformly deposited with an ultra-thin dewettable film <NUM>. The substrate <NUM>, for example, can include a borosilicate glass, an aluminosilicate glass, soda-lime glass, chemically strengthened borosilicate glass, chemically strengthened aluminosilicate glass, and chemically strengthened soda-lime glass. The substrate may have a selected length and width, or diameter, to define its surface area. The substrate <NUM> may also have a selected thickness. In some examples, the substrate <NUM> may have a thickness in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>.

In some examples, the substrate <NUM> includes a glass-ceramic material having both a glassy phase and a ceramic phase. Illustrative glass-ceramics include those materials where the glass phase is formed from a silicate, borosilicate, aluminosilicate, or boroaluminosilicate, and the ceramic phase is formed from β-spodumene, β-quartz, nepheline, kalsilite, or carnegieite. "Glass-ceramics" include materials produced through controlled crystallization of glass. In some examples, the glass-ceramics have about <NUM>% to about <NUM>% crystallinity. Examples of suitable glass-ceramics may include Li<NUM>O-Al<NUM>O<NUM>-SiO<NUM> system (i.e., LAS-System) glass-ceramics, MgO-Al<NUM>O<NUM>-SiO<NUM> system (i.e., MAS-System) glass-ceramics, ZnO × Al<NUM>O<NUM> × nSiO<NUM> (i.e., ZAS system), and/or glass-ceramics that include a predominant crystal phase including β-quartz solid solution, β-spodumene, cordierite, and lithium disilicate. The glass-ceramic substrates may be strengthened using a chemical strengthening process.

In some examples, the film may have a thickness with a range of 1Å to 10000Å, or 2Å to 5000Å, or 3Å to 2500Å, or 5Å to 1000Å, or 10Å to 500Å, or 1Å to 1000Å, or 1Å to 100Å, or 100Å to 1000Å, or 1000Å to 2500Å, or 2500Å to 5000Å, or 5000Å to 10000Å, or 1Å to 10Å, or 5Å to 75Å, or 10Å to 50Å. In some examples, film <NUM> may be deposited with at least one of: pulsed laser ablation, thermal evaporation, sputtering (e.g., magnetron sputtering, DC sputtering, AC sputtering, etc.), chemical vapor deposition (CVD), plasma-enhanced CVD, atomic layer deposition (ALD), electron-beam (E-beam) evaporation, or combinations thereof. In some examples, the film <NUM> may be selected from at least one of: metals (e.g., Cu, Al, Ni, Cr, Ti, Au, Ag, Co, W, Pt, etc.), alloys, metal oxides, polymers, organic materials, metal nitrides, or combinations thereof. In some examples, the deposition may be conducted for a time in a range of <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec.

Thereafter, in a second step of <FIG>, film <NUM> may be subjected to a thermal dewetting process to form islands <NUM> having controlled geometries. In other words, thermal annealing-induced morphological evolution of ultra-thin dewettable films may be used to pattern film <NUM> on substrate <NUM> to obtain an ordered array of crystallographically-oriented or randomly-distributed nanoparticle or microparticle islands <NUM>. The deposition techniques as in <FIG> may function to impose a constraint on the size and number density of the islands post-thermal dewetting sue to formation of a semi-continuous or continuous film for longer deposition times that result in a broad or no localized surface plasmon resonance (LSPR) response. Thus, transformation of such semi-continuous or continuous thin films (e.g., film <NUM>) into random island films is possible by post-deposition thermal dewetting. In some examples, a cross-sectional shape of the islands (or at least a portion thereof) taken from an axis parallel to the substrate <NUM> may be approximately at least one of circular, oval, elliptical, Cassini oval, Cartesian oval, egg-shaped, or combinations thereof.

In some examples, thermal dewetting may be carried out via rapid thermal annealing at temperatures in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, for a time in a range of <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. Before thermal dewetting, the chamber was pumped and purged with nitrogen gas several times to ensure adequate purity. In some examples, forming gas may be flown into the chamber to prevent samples from contamination during thermal treatment. After annealing, samples were cooled to room temperature in the furnace. In some examples, the islands may have at least one dimension (e.g., height, cross-sectional diameter, etc.) in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>.

Thereafter, in a third step of <FIG>, a polymer coating <NUM> is disposed over the substrate <NUM> and islands <NUM>. In some examples, the thickness of coating <NUM> is less than a height of the islands <NUM> to leave a portion of the islands exposed. In some examples, the thickness of coating <NUM> is roughly equivalent to a height of the islands <NUM>. In some examples, the thickness of coating <NUM> is greater than a height of the islands <NUM> to completely bury the islands within the coating. In some examples, a thickness of the coating <NUM> varies in a range of <NUM> to <NUM>. In the invention the coating <NUM> comprises metal oxides. In some other examples, the coating <NUM> may be at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), glass materials, semiconductor materials, or combinations thereof and deposited via at least one of spin-coating, dip coating, plating (e.g., electroplating), sol-gel, Langmuir-Blodgett method, chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), or combinations thereof.

After positioning the coating <NUM> to cover at least a portion of the islands, the entire structure may be cured. The curing process is critical for defining the properties of the polymeric film. In some examples, the curing process comprises a first curing step and a second curing step. In the first curing step, the structure may be heated to a first temperature in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, for a first time in a range of <NUM> sec to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> sec to <NUM>. In the second curing step, the structure may be heated to a second temperature in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, for a second time in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>.

In some examples, the first temperature is less than the second temperature, or the first temperature is approximately equal to the second temperature, or the first temperature is greater than the second temperature. In some examples, the first time is less than the second time, or the first time is approximately equal to the second time, or the first time is greater than the second time. In some examples, the first curing step and the second curing step are performed consecutively, or with an intervening processing step therebetween.

Thereafter, in a fourth step of <FIG>, the islands <NUM> are etched to form a relatively structured array of features <NUM> (e.g., hole, indentation, cavities, etc.) in the coating <NUM> having a footprint at the locations of the previously positioned islands <NUM>. In some examples, the features may have at least one dimension (e.g., depth, diameter, etc.) in a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>.

In some examples, the etching may be a wet etch comprising at least one of ammonium persulfate, FeCl<NUM> saturated solution, KCN, H<NUM>O:HNO<NUM>, HNO<NUM>, NH<NUM>OH:H<NUM>O<NUM>, HNO<NUM>:H<NUM>O<NUM>, NH<NUM>:H<NUM>O<NUM>, H<NUM>PO<NUM>:HNO<NUM>:HAc, HNO<NUM>:H<NUM>SO<NUM>:CrO<NUM>:NH<NUM>Cl:H<NUM>O, HCl:FeCl<NUM>:H<NUM>O, or combinations thereof. In some examples, the etching may be a dry vapor etch, such as plasma etching with oxygen plasma.

Turning now to <FIG>, which illustrate a structured glass fabrication process, according to some embodiments. Specifically, the first step of <FIG>, where a transparent substrate <NUM> is uniformly deposited with an ultra-thin dewettable film <NUM>, and the second step of <FIG>, where film <NUM> is subjected to a thermal dewetting process to form islands <NUM> having controlled geometries, may be performed with the conditions and/or materials as described above in <FIG>.

Thereafter, in a third step of <FIG>, a dewettable coating <NUM> is disposed over the substrate <NUM> and islands <NUM>. In some examples, the thickness of coating <NUM> is less than a height of the islands <NUM> to leave a portion of the islands exposed. In some examples, the thickness of coating <NUM> is roughly equivalent to a height of the islands <NUM>. In some examples, the thickness of coating <NUM> is greater than a height of the islands <NUM> to completely bury the islands within the coating. In some examples, a thickness of the coating <NUM> varies in a range of <NUM> to <NUM>. In some examples, the coating <NUM> is a dewettable coating comprising at least one of metals (e.g., Cu, Al, Ni, Cr, Ti, Au, Ag, Co, W, Pt, etc.), alloys, metal oxides, polymers, organic materials, metal nitrides, or combinations thereof and may be deposited similarly (e.g., apparatus, etc.) as film <NUM>. For example, coating <NUM> may be deposited with at least one of: pulsed laser ablation, thermal evaporation, sputtering (e.g., magnetron sputtering, DC sputtering, AC sputtering, etc.), chemical vapor deposition (CVD), plasma-enhanced CVD, atomic layer deposition (ALD), electron-beam (E-beam) evaporation, or combinations thereof for a time in a range of <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec. , or <NUM> sec. to <NUM> sec.

Thereafter, in a fourth step of <FIG>, where the islands <NUM> are etched to form a relatively structured array of features <NUM> (e.g., hole, indentation, cavities, etc.) in the coating <NUM> having a footprint at the locations of the previously positioned islands <NUM>, may be performed with the conditions and/or materials as described above in <FIG>.

Thereafter, in a fifth step of <FIG>, the structured array of features <NUM> in the coating <NUM> is transferred to the substrate <NUM> to form pattern <NUM>. In some examples, the transfer process comprises an isotropic wet etch. In some examples, the transfer process comprises an anisotropic dry etch (e.g., reactive ion etching, RIE). In some examples, the etch may be conducted to a depth having a range of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, into the substrate <NUM>.

Finally, after the step of pattern transfer, the coating <NUM> is etched to remove the residual mask. In some examples, the etching may be a wet etch comprising at least one of HNO<NUM>:HAc:acetone, HF:HNO<NUM>, FeCl<NUM>, HNO<NUM>:H<NUM>SO<NUM>:HAc:H<NUM>O, HNO<NUM>:H<NUM>O, HNO<NUM>:HAc, Ce(NH<NUM>)<NUM>(NO<NUM>)<NUM>:H<NUM>O, HF, H<NUM>PO<NUM>, HNO<NUM>, HF:HNO<NUM>, HCl:HNO<NUM>, 2NH<NUM>NO<NUM>. Ce(NO<NUM>)<NUM>. <NUM>(H<NUM>O):HNO<NUM>:H<NUM>O, H<NUM>PO<NUM>:HNO<NUM>:CH<NUM>COOH:H<NUM>O, or combinations thereof. In some examples, the etching may be a dry vapor etch, such as plasma etching with oxygen plasma.

Thus, as provided herein, processes are disclosed to form structured polymers and structured glasses comprising features having at least one dimension (e.g., diameter, depth, or combinations thereof) in a range of or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>.

Moreover, the nanostructures formed on the surface of the polymers (e.g., <FIG>) and/or the surface of the glass substrate (e.g., <FIG>) comprise a surface area fraction in a range of <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%, or <NUM>% to <NUM>%.

As a result of the formed structured polymers and structured glasses, the resultant final structure (e.g., <FIG> and/or <FIG>) comprise optical properties of at least one of: (<NUM>) transmission through structure as greater than <NUM>%, or greater than <NUM>%, or greater than <NUM>%, or greater than <NUM>%, or greater than <NUM>%, or greater than <NUM>%; or (<NUM>) haze of the structured surface as being less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%; or (<NUM>) reflection of the structured surface as being less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%, or less than <NUM>%; or (<NUM>) water contact angle of the structured surface (after fluorosilane treatment) as being greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°, or greater than <NUM>°; or (<NUM>) a combination of (<NUM>), (<NUM>), (<NUM>) and/or (<NUM>).

The embodiments described herein will be further clarified by the following examples.

Double-side, optically-polished, ultraviolet (UV)-fused silica glass substrates having a thickness of about <NUM> and an area of about <NUM> sq. were utilized. The substrate surfaces were first cleaned in acetone for about <NUM>, followed by an ethanol ultrasonic bath, also for about <NUM>. The substrates were then rinsed in deionized (DI) water and dried with nitrogen gas. An ultra-thin metal film of copper was deposited using a magnetron sputtering system (ATC Orion <NUM>, AJA International, Inc.

For example, the sputtering system comprises a computer-controlled fully automatic RF/DC deposition system with co-planar configuration and may have at least two different target materials installed at the same time. The target size diameter is <NUM> inches and the system reaches thickness uniformity of about <NUM>% over <NUM>-inch diameter substrates. Moreover, there may be an integrated load lock system for sample transfer without breaking the vacuum of the main chamber. The to-be-coated substrates may optionally be subjected to co-sputtering, as the sputtering system includes multiple radio-frequency (RF) and multiple direct current (DC) power sources. The sputtering system also allows deposition at higher temperature (e.g., up to <NUM>) and comprises an oxygen reactive gas line, apart from an argon processing gas line. Substrates are placed on a rotating sample holder that spin around an axis of the chamber up to a maximum rotation frequency of <NUM> revolutions/min. The main chamber is connected to a turbo pump which reaches a base vacuum level of <NUM>×<NUM>-<NUM> Pa (<NUM>×<NUM>-<NUM> Torr), while the load lock is pumped by a smaller rotary pump.

Thereafter, the copper-coated substrates were annealed to high temperatures in a range of <NUM> to <NUM> to create nanoparticles by a rapid thermal annealing system (RTP-<NUM>-HV, Unitemp GmbH). High purity nitrogen gas was included as part of the anneal to prevent oxidation of the copper film at an environment pressure of about <NUM> atm. By controlling thickness of the deposited metal as well as the temperature and time of the annealing process, it is possible to define the geometry of the nanoparticles formed by dewetting.

After formation of the nanoparticle islands, diluted polyimide (CP1 Polyimide, Nexolve Materials) in N-methyl-<NUM>-pyrrolidone (NMP) was spun coated, covering the whole substrate and partially covering a portion of the nanoparticles. An APS ((<NUM>-aminopropyl)triethoxysilane) promoter may be used to improve adhesion of the PI layer to the substrate via silicon-oxygen bonds. The thickness of the deposited polymer films may be controlled by variation of polymer (PI) concentration in solution (NMP) as well as varying the process parameters of the deposition apparatus (G3P Spin Coater, Specialty Coating Systems). For example, the spin coater may be spun at a rotational speed in a range of <NUM> rpm to <NUM> rpm, for a time in a range of <NUM> sec to <NUM> sec, and at a ramp time ranging from <NUM> sec to <NUM> sec. After completion of deposition, PI polymer is cured in a two-step process, first at about <NUM> for <NUM> and subsequently at about <NUM> for <NUM>, both of which were conducted on a standard hot plate. As a final step, the copper nanoparticle islands were chemically etched using a <NUM>% solution of ammonium persulfate in water for a time in a range of <NUM> to <NUM>, leaving a uniform nanostructured PI surface.

Double-side, optically-polished, ultraviolet (UV)-fused silica glass substrates having a thickness of about <NUM> and an area of about <NUM> sq. were utilized. The substrate surfaces were first cleaned in acetone for about <NUM>, followed by an ethanol ultrasonic bath, also for about <NUM>. The substrates were then rinsed in deionized (DI) water and dried with nitrogen gas. An ultra-thin metal film of copper was deposited using a magnetron sputtering system (explained above). Thereafter, the copper-coated substrates were annealed to high temperatures in a range of <NUM> to <NUM> to create nanoparticles by a rapid thermal annealing system (explained above). High purity nitrogen gas was included as part of the anneal to prevent oxidation of the copper film at an environment pressure of about <NUM> atm. By controlling thickness of the deposited metal as well as the temperature and time of the annealing process, it is possible to define the geometry of the nanoparticles formed by dewetting.

Subsequently, a thin film of nickel was deposited by sputtering atop the copper nanoparticles, filling the gaps therebetween, to a height less than a height of the copper nanoparticles. The copper nanoparticles were chemically etched using a <NUM>% solution of ammonium persulfate in water, leading to a nano-hole patterned coating of nickel with sufficient thickness to use as a mask for a dry etch. A RIE system (Plasmalab System <NUM>, Oxford Instruments) was used in a dry etch to transfer the nanostructured array of features in the nickel coating to the substrate surface to form a pattern mirroring the pattern of the dewetted copper particles. Etching was performed at 300W RF power (<NUM> DC voltage) at <NUM> Pa (<NUM> mTorr) in <NUM> sccm Ar/<NUM> sccm CHF<NUM> plasma. Finally, the samples were immersed in an aqua regia etchant (mixture of water, hydrochloric acid and nitric acid - <NUM>:<NUM>:<NUM> by volume) to remove the residual nickel metal mask.

<FIG> illustrate optical comparisons (antireflective effects) between bare fused silica glass and nanostructured glass, according to some embodiments. Specifically, the nanostructured effects on glass results in a higher transmission (<FIG>) and lower reflection (<FIG>) of the glass than when compared with bare glass that does not have nanostructuring. Thus, nanostructuring only one surface makes it possible to reduce reflection by almost half, thereby indicating antireflective effect of the nanostructures.

<FIG> illustrate optical comparisons (antireflective effects) between flat polyimide (PI) on glass and nanostructured polyimide on glass, according to some embodiments. Specifically, the nanostructured effects on polyimide results in a higher transmission (<FIG>) and lower reflection (<FIG>) of the polyimide on glass than when compared with flat polyimide on glass that does not have nanostructuring. Thus, even with deposition of a higher refractive index material on top of glass, nanostructuring the polyimide make it possible to reduce the bare glass reflection, combining the advantage of having PI on glass and introducing an antireflective effect.

The antireflective effect of the disclosed nanostructures is based on a smooth refractive index gradient between the air-nanostructured surface interface. Creating sub-wavelength structures, light scattering becomes negligible, thereby preserving directionality of the transmitted beams (e.g., visible light as shown in <FIG>). Modifying geometry and size of the nanostructures allows for optimization of the antireflective effect for different and wider wavelength ranges, while the angular response (i.e., omnidirectionality), is improved compared with the antireflective multilayer coatings.

<FIG> illustrate SEM images of nanostructured polyimide on glass at <NUM> (<FIG>), <NUM> (<FIG>), and <NUM> (<FIG>) magnification, according to some embodiments. <FIG> illustrate SEM images of nanostructured glass at <NUM> (<FIG>), <NUM> (<FIG>), and <NUM> (<FIG>) magnification, according to some embodiments. In both cases, visual evidence is provided of the formed nanostructures (e.g., cavities) that mirror the shape of the dewetted nanoparticle islands as explained in the fabrication process. The nanostructured polyimide on glass may be formed by the process of <FIG>; the nanostructured glass may be formed by the process of <FIG>.

<FIG> illustrate SEM images of nanostructured polyimide on glass before (upper) and after (lower) the TABER® Crockmeter test, which can be used to test smudge and smear resistance, as well as rub abrasion, scuff and/or mar performance of surfaces. In one implementation, mechanical resistance was tested by rubbing a standard rubbing textile (e.g., microfiber cloth) over a two-squared centimeter nanostructured surface area at a constant force of 9N. As is seen in <FIG>, the integrity of the nanostructured polyimide on glass surface remains intact both before (upper) and after (lower) conducting the Crockmeter test, thereby indicating sufficient mechanical resistance of the article upon application of shear and compression forces.

<FIG> illustrates wetting properties of nanostructured glass, according to some embodiments. Contact angles for water, oleic acid and hexadecane were measured on nanostructured glass before coating ("after fabrication") and after coating ("after fluorosilane") its surface with a low surface tension fluorosilane self-assembled monolayer. For reference, contact angles were also measured on flat glass (i.e., non-nanostructured glass; "flat SiO<NUM> sample after fluorosilane") to determine and compare effects of nanostructuring on hydrophobicity. It is seen that not only does fluorosilane enhance hydrophobicity of the nanostructured glass, but that creating these subwavelength nanostructures allows for achieving superhydrophobicity and oleophobicity, much more so than flat glass. Thus, nanostructured surfaces, when coated with a low surface tension fluorosilane self-assembled monolayer, may become superhydrophobic and oleophobic with very low contact angle hysteresis (difference between the advancing and receding contact angle).

Thus, as provided herein, improved transparent oleophobic surfaces are disclosed and methods of fabrication thereof having enhanced optical properties, mechanical resistance, and hydrophobicity. In other words, a new anti-reflective, low haze, transparent, hydrophobic substrate based on nanostructures is disclosed. Moreover, a novel lithography-free, scalable technique for fabricating the nanostructures in glass, polyimide, or other inorganic and organic (polymer) materials is also disclosed. Contemplated applications include self-cleaning and anti-reflective surfaces for display screens, solar panels, and automotive. Advantages of the surface and method of fabrication disclosed herein include: (<NUM>) a lithography-free, scalable, and timesaving process to nanostructure glass, polyimide, inorganic and organic crystals in general; and (<NUM>) improvements to optical, mechanical, and wetting properties of glass, polyimide, and polyimide on glass.

As utilized herein, the terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided.

As utilized herein, "optional," "optionally," or the like are intended to mean that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not occur. The indefinite article "a" or "an" and its corresponding definite article "the" as used herein means at least one, or one or more, unless specified otherwise.

Claim 1:
A method (<NUM>) for fabricating a structured surface, comprising:
providing a transparent substrate (<NUM>);
disposing a dewettable film (<NUM>) over the substrate (<NUM>);
annealing the dewettable film (<NUM>) to form a plurality of islands (<NUM>);
forming a coating (<NUM>) over the plurality of islands;
etching the plurality of islands (<NUM>) to form a structured array of surface features (<NUM>) in the coating (<NUM>);
transferring the structured array of surface features (<NUM>) from the coating (<NUM>) to the substrate (<NUM>); and
removing the coating (<NUM>);
wherein the coating (<NUM>) is a dewettable coating comprising at least one of: metals, alloys, metal oxides, polymers, organic materials, metal nitrides, or combinations thereof.