Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2024 Feb 27;9(10):12204–12210. doi: 10.1021/acsomega.4c00170

Fabrication of Superhydrophobic Nanostructures on Glass Surfaces Using Hydrogen Fluoride Gas

Kohei Yasuda †,‡, Yasuo Hayashi ‡, Takayuki Homma †,§,*
PMCID: PMC10938581  PMID: 38496934

Abstract

graphic file with name ao4c00170_0015.jpg

Water-repellent glass surfaces have become increasingly important to ensure clear visibility in outdoor cameras, sensors, and automotive windows. In this study, we investigated a process for the formation of nanoscale structures on a glass surface using chemical reactions with hydrogen fluoride gas. Using this approach, nanostructures with superhydrophobicity, superhydrophilicity, and antireflective properties were formed on glass surfaces with minimal processing time. This mask-free method, working at atmospheric pressure, can be efficiently integrated within the float process, a mainstream manufacturing technique for flat glass, to introduce nanostructures onto the glass surface. Notably, after treatment with (1-H, 1-H, 2-H, 2-H-tridecafluorooctyl)trimethoxysilane (FAS-13), a typical hydrophobic agent, the resulting surface exhibited a maximum water contact angle of 162°. Owing to its low reflectivity and superhydrophobicity, this surface is anticipated to find applications in not only the design of architectural window glass and vehicle windows but also the development of solar panels and sensor cover glass for autonomous vehicles.

1. Introduction

Recent technological advancements have led to an increase in cameras and sensors being installed outdoors, for example, in drones and autonomous vehicles. This amplifies the importance of glass surfaces with water-repellent characteristics to ensure clear visibility. Furthermore, owing to environmental concerns, superhydrophobic solar panels are in great demand. As superhydrophobic surfaces can also be expected to be self-cleaning, the demand for superhydrophobic glass surfaces is growing rapidly.1

Generally, a superhydrophobic surface is defined as a surface with a static water contact angle greater than 150°. Some definitions also include a contact angle hysteresis of less than 10°.2 A common method to create such surfaces involves creating micro-to-nano scale structures with low surface energy.3−7 Several approaches to impart water repellency to glass surfaces have been proposed based on the creation of nanostructures on the glass surface and the subsequent deposition of a low surface energy material. These methods can be broadly categorized into two types: nanostructure coating methods8−13 or methods involving glass etching to create micro/nanostructures.14−19 However, existing methods are problematic for a variety of reasons. In nanostructure coating methods, the presence of different materials on the surface layer causes bond weakening and exfoliation problems owing to differences in thermal properties. In methods involving glass etching, creating micro-to-nanoscale roughness by surface etching requires the induction of localized etching rate differences on the surface. Moreover, to ensure sufficient visible light transmittance without causing light scattering, the nanostructures should have dimensions preferably not greater than 100 nm.20 Reactive ion etching (RIE) is a representative method for etching glass. Because RIE is an anisotropic etching process, microscale or nanoscale structures can be created by constructing a fine mask or sacrificial layer on the surface to produce localized etching rate differences. Reported examples include methods involving the annealing of nickel particles to form fine particles,14 use of polystyrene spheres as masks,15 and that of SiO2 films as sacrificial layers.16 However, all of these methods require complex procedures. Additionally, RIE requires a vacuum and, thus, necessitates placing the glass inside a chamber, which presents disadvantages in terms of productivity, size limitations, and cost. In contrast, attempts to create water-repellent nanostructures have been made using wet etching with hydrofluoric acid solutions, a method traditionally used for glass processing. This method involves spraying a hydrofluoric acid mist onto the glass surface to perform localized etching and create pillar structures on the surface.17 However, although this method excels in terms of material efficiency, as it does not require a mask, the resulting contact angle is less than 150°. Laser ablation is another effective method for creating micro-scale structures on glass surfaces.18,19 While highly hydrophobic surfaces have been formed using this method, structures formed via laser ablation have typically been on the order of micrometers, leading to the scattering of visible light. Moreover, the need to scan the entire glass surface with a laser renders this approach less efficient than chemical treatments.

A recent study investigated the use of hydrogen fluoride (HF) gas for etching, and this produced a rougher surface.21 If superhydrophobic structures can be constructed by using HF gas, the high-temperature environment required for the glass manufacturing process can be utilized, allowing the rapid construction of micro-to-nanoscale structures. However, there are limited studies on glass etching using HF gas and no reports on its use for achieving water repellency. In this study, we investigated a method to conveniently fabricate nanostructures with both superhydrophobic and antireflective properties by examining the conditions of the reaction between glass and hydrogen fluoride gas. Typically, flat glass is manufactured using the float process,22 wherein a continuous temperature change from 1000 °C to room temperature occurs during the formation process. Techniques to spray reactive gases during the float process have been realized,23 and nanostructure construction on the glass surface using this method would facilitate the integration of the glass manufacturing and nanostructure construction processes, resulting in an extremely productive superhydrophobic structure construction process. In this study, we adopted hydrochloric acid cleaning, a frequently used method in the glass manufacturing process, as a post-treatment, which should facilitate future process scale-up. We proposed this novel process and examined the nanostructure formation and control realized using the method.

2. Experimental Section

2.1. Surface Nanostructure Formation on Glass and Water-Repellent Treatment

Soda-lime silicate glass, the most common type of sheet glass, was chosen as the substrate material; the dimensions of the glass plates were 50 × 50 × 1 mm3. The substrate composition in mol % was SiO2:Na2O:CaO:MgO:Al2O3 = 72:13:9:5:1. The experimental flow is illustrated in Figure 1. After ultrasonically cleaning the glass substrate in pure water for 15 min, it was treated with HF gas under atmospheric pressure, while being heated in a conveyor-type electric furnace. A schematic of this furnace is shown in Figure 2. The furnace was designed to permit the reaction with HF gas only inside the treatment section. The dimensions of this section were 330 × 320 × 15 mm3. The reaction time was adjusted by changing the conveyance speed, with a typical speed of 80 mm/s corresponding to a 4-s reaction time. HF was supplied as a gas by heating its liquid form in a cylinder. Its flow rate was controlled using a mass flow controller, and its concentration was adjusted by mixing it with nitrogen. Following mixing, the gas flow rate was adjusted to 70 L/min. Half of the HF-treated substrates were cleaned in a 10% hydrochloric acid solution for 15 min. Subsequently, to remove adsorbed organic matter from the surface, the substrates were subjected to ultraviolet (UV)-ozone treatment for 15 min. Vapor deposition of (1-H, 1-H, 2-H, 2-H-tridecafluorooctyl)trimethoxysilane (FAS-13; FUJIFILM Wako Chemical Corporation), as a low-surface-energy coating, was then performed following reported methods.24 Specifically, 2 mL of FAS-13 and 10 substrates were placed in a SUS304 vessel (10 L capacity) under a nitrogen atmosphere and then heated at 100 °C for 2 h. After the deposition, the substrates were left in a nitrogen atmosphere at 25 °C for more than 4 h before being removed.

Figure 1.

Figure 1

Open in a new tab

Process flow. First, all of the substrates were ultrasonically cleaned in pure water. Subsequently, certain substrates were reacted with HF gas and cleaned with hydrochloric acid. Finally, all of the substrates were subjected to UV-ozone cleaning, followed by FAS-13 deposition.

Figure 2.

Figure 2

Open in a new tab

Schematic of a conveyor-type electric furnace. By adjusting the conveyance speed, the reaction time can be controlled.

2.2. Surface Characterization and Contact Angle Measurement

The morphology of the fabricated substrates was observed by using scanning electron microscopy (SEM; Hitachi High-Tech, SU8030) and atomic force microscopy (AFM; Bruker, Dimension Icon). The surface elemental composition was measured via X-ray photoelectron spectroscopy (XPS; ULVAC PHI, QuanteraII) using the Al Kα line and a measurement angle of 45°. During depth analysis, Ar+ sputtering and measurement acquisitions were alternated. To eliminate the effects of charging during chemical shift measurements, the C 1s peak was corrected to 285 eV. The crystals on the prepared surface were investigated by X-ray diffraction (XRD; Rigaku, SmartLab) using Cu Kα radiation. Transmittance measurements were conducted using a spectrophotometer (JASCO, V-670), and water contact angle measurements were conducted using a contact angle meter (KYOWA, DMo-702). The volume of the water droplet was set to 3 μL, and the average value was determined from 10 measurements. Advancing and receding contact angles, as well as contact angle hysteresis values, were measured using the expansion–contraction method, and five measurements were acquired and averaged for each sample. An initial droplet volume of 30 μL was used, and the advancing contact angle was measured by expelling water at 0.5 μL/s for 100 s. The receding contact angle was measured by withdrawing water for 100 s. The melting point of the fluorides was measured using thermogravimetry–differential thermal analysis (TG-DTA; Rigaku, TG8120); the substrate was heated from 25 to 900 °C at a rate of 10 °C/min, and the weight change and heat during this period were measured.

3. Results and Discussion

3.1. Nanostructure Construction and Surface Characterization

Figure 3 shows surface and cross-sectional SEM images of the untreated substrate in (a) and (b), the HF-treated substrate in (c) and (d), and the substrate after HF treatment and then cleaning with 10% hydrochloric acid in (e) and (f). The HF treatment was conducted at 500 °C with 5% HF for 4 s. In the HF-treated glass shown in (c) and (d), a porous film, formed at the upper 500 nm of the surface, was apparent. Table 1 presents the surface composition analysis results obtained using XPS for all of the samples, and Figure 4 shows a plot of these results for the HF-treated substrate. The XPS profile of each substrate (Table 1) is shown in S1. In the HF-treated glass, the silicon and oxygen contents were significantly lower than those in the untreated glass, whereas the sodium, magnesium, calcium, and fluorine contents were substantially higher. This indicates that the fluorination of the oxide progressed and only silicon fluoride, which has a low boiling point, evaporated, leaving the other metal fluorides on the surface. These results indicate that the cationic elements in the glass are fluorinated by HF treatment, leading to the formation of a nanoporous structure. These findings are consistent with previous results.21Figure 5 shows the XRD patterns of three types of substrates: an untreated substrate, a substrate cleaned with HCl solution after HF treatment, and an HF-treated substrate. These results confirm the transformation of the cationic elements in the glass into fluoride crystals owing to their reaction with HF. Cleaning with an HCl solution removes these crystals, leading to the exposure of an amorphous surface.

Figure 3.

Figure 3

Open in a new tab

Scanning electron microscopy (SEM) images of the untreated substrate in (a,b), the HF-treated substrate in (c,d), and the substrate cleaned with 10% hydrochloric acid after HF treatment in (e,f).

Table 1. Surface Composition of Each Substrate as Measured by X-ray Photoelectron Spectroscopy (XPS).

  O (1s) F (1s) Na (1s) Mg (2p) Al (2p) Si (2p) Ca (2p)
untreated 61.3 0.1 9.2 2.1 1.0 24.8 1.6
HF 1.8 45.4 31.4 9.2 2.0 2.8 7.4
HCl sol. after HF 62.1 1.6 6.5 2.5 0.2 26.5 0.6
Open in a new tab

Figure 4.

Figure 4

Open in a new tab

Elemental composition as a function of depth in the substrate treated with 5% HF for 4 s at 500 °C.

Figure 5.

Figure 5

Open in a new tab

X-ray diffraction (XRD) patterns of untreated substrate, the substrate cleaned with HCl solution after HF treatment, and the substrate treated with 5% HF at 500 °C.

After the HF-treated substrate was cleaned with 10% hydrochloric acid, the SEM results revealed the presence of nanostructures on the surface. However, XPS surface analysis results indicated that the composition did not significantly differ from that of untreated glass. This suggests that the fluoride crystals formed on the surface were removed by a hydrochloric acid cleaning. In this substrate, a trace amount of fluorine was detected, which can be attributed to a small amount of fluorine being infused into the glass. Figure 6 shows the Si 2p XPS analysis results. It was confirmed that the Si 2p peak was shifted to the high-energy side compared to that of the untreated substrate, which is attributed to the formation of Si–F bonds.25

Figure 6.

Figure 6

Open in a new tab

X-ray photoelectron spectroscopy (XPS) spectra of the untreated substrate and the substrate treated with HF followed by cleaning with 10% hydrochloric acid.

3.2. Water Contact Angle

Figure 7 shows the water contact angles of each substrate after UV-ozone cleaning and subsequent exposure to the atmosphere for 30 d. After UV-ozone cleaning, all the substrates possessed hydrophilic surfaces with contact angles below 10°. However, after 30 d in the atmosphere, the contact angle of the untreated substrate had increased to approximately 30°. This is attributed to the adsorption of organic substances from the atmosphere, which reduces surface energy.26 In contrast, both the HF-treated substrates and those subsequently cleaned with hydrochloric acid maintained their hydrophilicity even after 30 d, which may be attributed to surface roughness. Wenzel introduced “r” to represent surface roughness, defined as the ratio of the actual surface area to the projected surface area:27

3.2. 1

Figure 7.

Figure 7

Open in a new tab

Water contact angle of each substrate immediately after ultraviolet-ozone cleaning and after subsequent exposure to atmosphere for 30 d.

The relationship between r and the apparent contact angle is expressed as

3.2. 2

where Inline graphic is the apparent contact angle and θY denotes the contact angle on a flat surface. As can be inferred from Wenzel’s equation, when the contact angle on a flat surface is less than 90°, the surface is considered hydrophilic. Figure 8a,b shows the AFM images of the surface after HF treatment followed by cleaning with hydrochloric acid. The r values calculated from the AFM images for the surface treated only with HF and for the surface after HCl post-treatment were 1.34 and 2.48, respectively. To achieve an apparent contact angle of 10° or less when the flat-surface contact angle is 30°, r must be 1.14 or higher; thus, these surfaces can retain sufficient hydrophilicity even when organic substances from the atmosphere are adsorbed. As condensation occurs when small liquid droplets adhere to the surface, this surface is useful for antifogging applications.28,29 Fogging due to condensation on automotive glass is a safety hazard. This method can be used to address this problem.

Figure 8.

Figure 8

Open in a new tab

Atomic force microscopy (AFM) images of the substrate after HF treatment (a) and of the substrate after HF treatment and then cleaning with hydrochloric acid (b); height histograms obtained from each AFM image with the average height set to zero (c).

Figure 9 shows the water contact angles of each surface after the FAS-13 coating had been applied. The untreated glass had a contact angle of 103°, which is the contact angle of FAS-13 on a flat surface and is consistent with previous results.24 However, the HF-treated glass and the glass treated with hydrochloric acid after the HF treatment had water contact angles of 131° and 152°, respectively. These increased contact angles cannot be explained by the Wenzel model alone. For a flat-surface contact angle of 103°, r must be 3.85° or higher to achieve a contact angle of over 150°, owing to the Wenzel effect. However, the presence of an air layer at the solid–liquid interface can increase the contact angle.30 The Cassie–Baxter model explains this effect with the following equation:

3.2. 3

where Inline graphic is the apparent contact angle and f is the solid–liquid contact area fraction. According to this equation, to achieve contact angles of 131° and 152° when the flat-surface contact angle is 103°, the f values were 0.44 and 0.15, respectively. Figure 8 shows the height histograms created by analyzing the AFM images with the average height set to zero. The surface treated with hydrochloric acid after HF treatment yielded a histogram with many low values and a few high values (protrusions from the surface). This is consistent with the SEM image results shown in Figure 3. On surfaces where a few sparse protrusions sparsely exist, water can be supported near the protrusion, thus reducing the solid–liquid contact area fraction f. Because of these shape differences, f decreased after hydrochloric acid cleaning, significantly increasing the surface hydrophobicity.

Figure 9.

Figure 9

Open in a new tab

Images of the water droplets placed on (a) the untreated substrate, (b) the substrate treated with HF, and (c) the substrate cleaned with hydrochloric acid after HF treatment and the subsequent deposition of FAS-13. (d) Water contact angles for each substrate.

3.3. Changes Owing to Processing Conditions

The upper and lower rows of panels in Figure 10 show surface and cross-sectional SEM images of substrates prepared without and with the HCl post-treatment, respectively, processed by using different reaction temperatures. The processing conditions were 5% HF and a reaction time of 4 s. As the reaction temperature increased, the sizes of the grains and pores forming the nanoporous structure also increased. The reaction rate between HF and glass increases with increasing reaction temperature, leading to the formation of a thicker fluoride layer within a set time. Therefore, in this study, the fluoride layer thickens with an increase in reaction temperature up to 500 °C. However, when the temperature exceeds 550 °C, the thickness of the fluoride layer unexpectedly decreases. This suggests that from this temperature, the increase in the rate of fluoride sublimation surpasses the increase in the rate of formation. Figure 11 shows the DTA results for the fluoride produced at 500 °C, which features an endothermic peak without weight loss at approximately 730 °C, likely corresponding to the melting point of the fluoride layer. Therefore, at the experimental temperatures used in this study, the fluoride layer existed in the solid state, suggesting that its size and shape changed as a result of a solid-phase reaction. Figure 12 displays magnified SEM images of the substrates prepared by HF treatment at 500 and 600 °C, with and without hydrochloric acid post-treatment. The surface morphology after the hydrochloric acid treatment resembled that of the interface between the fluoride layer and the glass, and the feature size was similar to that of the formed fluoride layer before the hydrochloric acid treatment. These results suggest that the fluoride and glass undergo a reaction that results in the formation of nanostructures on the surface via HF gas etching. Therefore, to control the shape of the nanostructure after hydrochloric acid treatment, the shape of the fluoride layer should be properly controlled.

Figure 10.

Figure 10

Open in a new tab

Scanning electron microscopy (SEM) images of the surface and cross sections of the substrates treated at various temperatures. The upper row shows substrates treated with HF, and the lower row shows those further cleaned with hydrochloric acid.

Figure 11.

Figure 11

Open in a new tab

Thermogravimetry–differential thermal analysis (TG-DTA) results for the fluoride formed at 500 °C. The peak at approximately 730 °C indicates the melting point.

Figure 12.

Figure 12

Open in a new tab

Cross-sectional scanning electron microscopy (SEM) images of the substrates treated at 500 and 600 °C: (a,b) substrates after HF treatment, while (c,d) substrates after HF treatment followed by hydrochloric acid cleaning.

Figure 13 shows the water contact angles of the substrates reacted using various temperature conditions. Table 2 lists the advancing contact angle (CAA), receding contact angle (CAR), and contact angle hysteresis (CAH) values for surfaces that showed a static contact angle greater than 150°. After the HF treatment and subsequent hydrochloric acid cleaning, as the temperature increased, the static contact angle increased, reaching 162° for the substrate treated at 650 °C after hydrochloric acid cleaning. Furthermore, for each treatment temperature, the contact angles of the substrates after hydrochloric acid treatment were higher than those of the substrates after HF treatment alone. This demonstrates that the effect of hydrochloric acid cleaning, as discussed in Section 3.2, holds true under any temperature condition, emphasizing the importance of hydrochloric acid cleaning. Increasing the treatment temperature resulted in an increase in the size of the fluoride layer, leading to an increased surface roughness at the interface with the glass. This was maintained after the hydrochloric acid treatment, increasing the spacing between surface protrusions and reducing the solid–liquid contact area.

Figure 13.

Figure 13

Open in a new tab

Top: water contact angle vs treatment temperature. The lower images show images of a water contact angle of (a) 143° after HF treatment only at 650 °C and (b) 162° after HF treatment at 650 °C followed by hydrochloric acid cleaning.

Table 2. Advancing Contact Angle (CAA), Receding Contact Angle (CAR), and Contact Angle Hysteresis (CAH) Values of Surfaces Cleaned with Hydrochloric Acid after HF Treatment at Various Temperatures.

  CAA CAR CAH
untreated 113° 100° 13°
500 °C 170° 139° 30°
550 °C 169° 138° 31°
600 °C 169° 147° 22°
650 °C 167° 164° 3°
Open in a new tab

3.4. Optical Properties

Figure 14 presents the transmittance results of the substrates after hydrochloric acid treatment under various reaction conditions. The “theoretical max” transmittance value is the theoretical maximum transmittance for single-sided coated glass, derived using the following equation:13

3.4. 4

where Ttotal is the transmittance of the untreated substrate. These results indicate that the treatment increased the transmittance of the substrate. The effective medium theory can be used to calculate the effective refractive index, neff, as follows:31,32

3.4. 5

where f represents the filling factor and ng and nair are the refractive indices of glass and air, respectively. This equation suggests that the effective refractive index gradually decreases from the inside of the glass surface owing to the pores formed on the glass surface, which indicates an antireflective surface. Additionally, as the treatment temperature was increased to 600 °C, the transmittance improved. This is believed to be because the proportion of pores on the surface increased, approaching the ideal value for an antireflection film. At a treatment temperature of 650 °C, the transmittance in the low-wavelength range decreased, suggesting that the increased roughness scattered low-wavelength light. Therefore, when constructing an antireflection layer on glass using this method, it is essential to carefully consider the processing conditions to appropriately control the shape of the interface between the fluoride and glass layers.

Figure 14.

Figure 14

Open in a new tab

Transmittance results for substrates cleaned with hydrochloric acid after HF treatment at various temperatures. The transmittance in the visible light range was improved with respect to the untreated surface for the surfaces treated at each temperature.

4. Conclusions

In this study, we introduced a novel approach to control and modify glass surfaces at the nanoscale to impart superhydrophilic, superhydrophobic, and antireflective properties. The method involved the formation of a nanostructure on the glass surface through a brief treatment with HF gas, followed by cleaning with hydrochloric acid, which produced a surface with long-lasting superhydrophilicity. This can be converted into a superhydrophobic surface with the addition of a hydrophobic treatment. By carefully adjusting the treatment parameters, superhydrophobicity can be combined with visible-light antireflective properties.

This technique offers several advantages over conventional microfabrication technologies such as RIE. Notably, it can be conducted under standard atmospheric conditions without the need for a mask. Moreover, it achieves contact angles larger than those via wet etching methods and offers higher visible light transmittance and productivity than those of laser processing. Moreover, it can be seamlessly integrated into the widely used process for manufacturing soda-lime silicate glass, providing a cost-effective solution.

Furthermore, we emphasize the importance of controlling the shape of the fluoride layer formed in order to tune the surface properties. Considering environmental regulations designed to support the development of ecofriendly hydrophobic films, our technology offers a sustainable solution by forming structures directly within the glass, thereby eliminating the constraint of the requirement for a coating material. The versatility of this technique renders it suitable for a variety of applications, not only in traditional contexts such as building and automotive windows but also in new fields, including autonomous vehicle sensors, solar panels, and medical optical devices.

Glossary

Abbreviations

CAA

advancing contact angle

CAH

contact angle hysteresis

CAR

receding contact angle

RIE

reactive ion etching

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.4c00170.

  • XPS profile of substrate treated with 5% HF at 500 °C, untreated substrate, and substrate cleaned with HCl solution after HF treatment (PDF)

Author Contributions

K.Y. and Y.H. conceived the experiments; K.Y. designed and performed the experiments; K.Y. wrote the manuscript; T.H. revised the manuscript; Y.H. and T.H. performed the data analysis.

This research did not receive any specific grant from funding agencies.

The authors declare no competing financial interest.

Supplementary Material

ao4c00170_si_001.pdf (281.1KB, pdf)

References

  1. Parkin I. P.; Palgrave R. G. Self-cleaning coatings. J. Mater. Chem. 2005, 15, 1689. 10.1039/b412803f. [DOI] [Google Scholar]
  2. Roach P.; Shirtcliffe N. J.; Newton M. I. Progress in superhydrophobic surface development. Soft Matter. 2008, 4, 224–240. 10.1039/B712575P. [DOI] [PubMed] [Google Scholar]
  3. Onda T.; Shibuichi S.; Satoh N.; Tsujii K. Super-water-repellent fractal surfaces. Langmuir 1996, 12, 2125–2127. 10.1021/la950418o. [DOI] [Google Scholar]
  4. Feng L.; Li S.; Li Y.; Li H.; Zhang L.; Zhai J.; Song Y.; Liu B.; Jiang L.; Zhu D. Super-hydrophobic surfaces: From natural to artificial. Adv. Mater. 2002, 14, 1857–1860. 10.1002/adma.200290020. [DOI] [Google Scholar]
  5. Yoshimitsu Z.; Nakajima A.; Watanabe T.; Hashimoto K. Effects of surface structure on the hydrophobicity and sliding behavior of water droplets. Langmuir 2002, 18, 5818–5822. 10.1021/la020088p. [DOI] [Google Scholar]
  6. Öner D.; McCarthy T. J. Ultrahydrophobic surfaces. Effects of topography length scales on wettability. Langmuir 2000, 16, 7777–7782. 10.1021/la000598o. [DOI] [Google Scholar]
  7. Nakayama K.; Tsuji E.; Aoki Y.; Park S.-G.; Habazaki H. Control of surface wettability of aluminum mesh with hierarchical surface morphology by monolayer coating: From superoleophobic to superhydrophilic. J. Phys. Chem. C 2016, 120, 15684–15690. 10.1021/acs.jpcc.5b09722. [DOI] [Google Scholar]
  8. Tadanaga K.; Katata N.; Minami T. Super-water-repellent Al2O3 coating films with high transparency. J. Am. Ceram. Soc. 1997, 80, 1040–1042. 10.1111/j.1151-2916.1997.tb02943.x. [DOI] [Google Scholar]
  9. Mahadik S. A.; Kavale M. S.; Mukherjee S. K.; Rao A. V. Transparent superhydrophobic silica Coatings on glass by sol-gel method. Appl. Surf. Sci. 2010, 257, 333–339. 10.1016/j.apsusc.2010.06.062. [DOI] [Google Scholar]
  10. Deng X.; Mammen L.; Butt H. J.; Vollmer D. Candle soot as a template for a transparent robust Superamphiphobic coating. Science 2012, 335, 67–70. 10.1126/science.1207115. [DOI] [PubMed] [Google Scholar]
  11. Zuo Z.; Gao J.; Liao R.; Zhao X.; Yuan Y. A novel and facile way to fabricate transparent superhydrophobic film on glass with self-cleaning and stability. Mater. Lett. 2019, 239, 48–51. 10.1016/j.matlet.2018.12.059. [DOI] [Google Scholar]
  12. Janowicz N. J.; Li H.; Heale F. L.; Parkin I. P.; Papakonstantinou I.; Tiwari M. K.; Carmalt C. J. Fluorine-free transparent superhydrophobic nanocomposite Coatings from mesoporous silica. Langmuir 2020, 36, 13426–13438. 10.1021/acs.langmuir.0c01767. [DOI] [PubMed] [Google Scholar]
  13. Isakov K.; Kauppinen C.; Franssila S.; Lipsanen H. Superhydrophobic antireflection coating on glass using grass-like alumina and fluoropolymer. ACS Appl. Mater. Interfaces 2020, 12, 49957–49962. 10.1021/acsami.0c12465. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Son J.; Kundu S.; Verma L. K.; Sakhuja M.; Danner A. J.; Bhatia C. S.; Yang H. A practical superhydrophilic self cleaning and antireflective surface for outdoor photovoltaic applications. Sol. Energy Mater. Sol. Cells 2012, 98, 46–51. 10.1016/j.solmat.2011.10.011. [DOI] [Google Scholar]
  15. Yu E.; Kim S.-C.; Lee H. J.; Oh K. H.; Moon M.-W. Extreme wettability of nanostructured glass fabricated by non-lithographic, anisotropic etching. Sci. Rep. 2015, 5, 9362. 10.1038/srep09362. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Nguyen B. D.; Cao B. X.; Do T. C.; Trinh H. B.; Nguyen T.-B. Interfacial parameters in correlation with anti-icing performance. J. Adhes. 2021, 97, 860–872. 10.1080/00218464.2019.1709172. [DOI] [Google Scholar]
  17. Wang L.; Li L.; Liu Y.; Wang S.; Cai H.; Jin H.; Tang Q.; Sun W.; Yang D. The preparation and characterization of uniform nanoporous structure on glass. R. Soc. Open Sci. 2020, 7, 192029. 10.1098/rsos.192029. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Wang B.; Hua Y.; Ye Y.; Chen R.; Li Z. Transparent superhydrophobic solar glass prepared by fabricating groove-shaped arrays on the surface. Appl. Surf. Sci. 2017, 426, 957–964. 10.1016/j.apsusc.2017.07.169. [DOI] [Google Scholar]
  19. Lin Y.; Han J.; Cai M.; Liu W.; Luo X.; Zhang H.; Zhong M. Durable and robust transparent superhydrophobic glass surfaces fabricated by a femtosecond laser with exceptional water repellency and thermostability. J. Mater. Chem. A 2018, 6, 9049–9056. 10.1039/C8TA01965G. [DOI] [Google Scholar]
  20. Rahmawan Y.; Xu L.; Yang S. Self-assembly of nanostructures towards transparent, superhydrophobic surfaces. J. Mater. Chem. Mater. 2013, 1, 2955–2969. 10.1039/C2TA00288D. [DOI] [Google Scholar]
  21. Ono Y.; Hayashi Y.; Urashima S.-H.; Yui H. Glass etching with gaseous hydrogen fluoride: Rapid management of surface nano-roughness. Int. J. Appl. Glass. Sci. 2022, 13, 676–683. 10.1111/ijag.16577. [DOI] [Google Scholar]
  22. Pilkington L. A. B. Review lecture: The float glass process. Proc. R. Soc. London A 1969, 314, 1–25. 10.1098/rspa.1969.0212. [DOI] [Google Scholar]
  23. Miyasaka S.; Nakada H.; Hayashi Y.; Fukawa M.; Nihei T.; Shirai M.; Okahata N.; Nakagawa K.; Yamanaka K.; Watanabe K.; Tanii S.; Ikawa N.; Kobayashi D.; Miyashita J.; Kato R.. Glass sheet capable of being inhibited from warping through chemical strengthening. Google Patent US9663396B2, 2017, 396 B2.
  24. Hozumi A.; Ushiyama K.; Sugimura H.; Takai O. Fluoroalkylsilane monolayers formed by chemical vapor surface modification on hydroxylated oxide surfaces. Langmuir 1999, 15, 7600–7604. 10.1021/la9809067. [DOI] [Google Scholar]
  25. Metzler D.; Bruce R. L.; Engelmann S.; Joseph E. A.; Oehrlein G. S. Fluorocarbon assisted atomic layer etching of SiO2 using cyclic Ar/C4F8 plasma. J. Vac. Sci. Technol. A 2014, 32, 020603. 10.1116/1.4843575. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Takeda S.; Yamamoto K.; Hayasaka Y.; Matsumoto K. Surface OH group governing wettability of commercial glasses. J. Non-Cryst. Solids 1999, 249, 41–46. 10.1016/S0022-3093(99)00297-5. [DOI] [Google Scholar]
  27. Wenzel R. N. Resistance of solid surfaces to wetting by water. Ind. Eng. Chem. 1936, 28, 988–994. 10.1021/ie50320a024. [DOI] [Google Scholar]
  28. Grosu G.; Andrzejewski L.; Veilleux G.; Ross G. G. Relation between the size of fog droplets and their contact angles with CR39 surfaces. J. Phys D: Appl Phys. 2004, 37, 3350–3355. 10.1088/0022-3727/37/23/019. [DOI] [Google Scholar]
  29. Chen Y.; Zhang Y.; Shi L.; Li J.; Xin Y.; Yang T.; Guo Z. Transparent superhydrophobic/superhydrophilic coatings for self-cleaning and anti-fogging. Appl. Phys. Lett. 2012, 101, 033701. 10.1063/1.4737167. [DOI] [Google Scholar]
  30. Cassie A. B. D.; Baxter S. Wettability of porous surfaces. Trans. Faraday Soc. 1944, 40, 546. 10.1039/tf9444000546. [DOI] [Google Scholar]
  31. Xu C.; Wang L.; Li D.; Zhang S.; Chen L.; Yang D. Improving the solar cell module performance by a uniform porous antireflection layer on low iron solar glass. Appl. Phys. Express 2013, 6, 032301. 10.7567/APEX.6.032301. [DOI] [Google Scholar]
  32. Ono Y.; Kimura Y.; Ohta Y.; Nishida N. Antireflection effect in ultrahigh spatial-frequency holographic relief gratings. Appl. Opt. 1987, 26, 1142–1146. 10.1364/AO.26.001142. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao4c00170_si_001.pdf (281.1KB, pdf)

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES