Surfactant-mediated preparation of fully waterborne robust superamphiphobic coatings for anti-icing

Abstract

Superamphiphobic coatings, capable of repelling both water and low-surface-tension liquids, hold immense potential for applications in self-cleaning, anti-fouling, and anti-icing. However, their widespread adoption is hindered by reliance on organic solvents, poor mechanical durability, and complex fabrication processes. Herein, fully waterborne superamphiphobic coatings are developed using waterborne polyurethane and fluorinated polysiloxane-modified silica nanoparticles (F-POS@SiO₂). The F-POS@SiO₂ dispersion is synthesized via acid-catalyzed hydrolysis and condensation of silanes in water mediated by fluorinated surfactants, eliminating the need for any organic solvents. When combined with waterborne polyurethane and applied sequentially via simple spray-coating, the resulting coatings exhibit hierarchical micro-/nanostructures and low surface energy. These features collectively endow the coatings with excellent static and dynamic repellency toward water and oils, robust mechanical durability, chemical resistance, thermal and UV stability, and anti-icing behavior. The coatings maintain performance across a range of substrates, offering a sustainable and scalable strategy for fabricating superamphiphobic surfaces with broad practical potential.

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New concepts

This work presents a concept for creating fully waterborne superamphiphobic coatings by integrating fluorinated polysiloxane-modified SiO₂ nanoparticles (F-POS@SiO₂) with waterborne polyurethane (WPU), without the use of any organic solvents. Unlike conventional superamphiphobic systems that rely on toxic VOCs and suffer from poor mechanical durability, we demonstrate a surfactant-mediated aqueous synthesis method that not only enables stable dispersion of fluorinated low-surface-energy materials in water but also facilitates the formation of robust hierarchical micro-/nanostructures through a simple spray process. The key innovation lies in the use of a fluorinated surfactant to mediate both surface energy control and nanoparticle organization, resulting in coatings that exhibit extreme repellency toward both water and oils, as well as exceptional mechanical, chemical, and environmental robustness. This eco-friendly, scalable approach introduces a conceptual advance in sustainable coating fabrication, opening a new avenue for practical, durable superamphiphobic surfaces applicable in anti-icing and self-cleaning technologies.

Introduction

Superamphiphobic surfaces, which exhibit simultaneous repellency to both water and low-surface-tension liquids, i.e. high contact angles (CA ≥ 150°) and low sliding angles (SA ≤ 10°), have garnered significant interest due to their promising potential in a wide range of applications.^1,2 Compared to superhydrophobic surfaces, superamphiphobic surfaces exhibit superior performance in applications demanding extreme liquid repellency, including self-cleaning,^3,4 anti-fouling,^5,6 anti-corrosion,⁷ and anti-bacterial.⁸ The realization of superamphiphobicity typically relies on two critical factors: the construction of a hierarchical micro-/nanostructured surface and the modification with low-surface-energy chemical groups.^9,10 Numerous fabrication techniques have been developed to achieve such features, including spray-coating,^11,12 dip-coating,¹³ self-assembly,¹⁴ chemical etching,⁷ and vapor deposition.¹⁵ Despite their promise, the practical deployment of superamphiphobic surfaces remains hindered by several key challenges.

First, achieving superamphiphobicity demands two critical factors to stabilize the Cassie–Baxter state: hierarchical surface roughness and ultra-low surface energy materials. A pivotal design strategy involves re-entrant textures-geometric features that thermodynamically hinder liquid penetration, enabling repellency toward liquids with surface tensions as low as 20–30 mN m⁻¹.^16–18 However, these re-entrant structures are inherently susceptible to mechanical and chemical degradation. Their delicate geometry is often compromised under physical abrasion, environmental aging, or exposure to destructive liquids, leading to a rapid decline in superamphiphobicity.^19,20 Additionally, scaling up such complex structures in a cost-effective manner remains a major bottleneck.^18,21 Therefore, the development of superamphiphobic surfaces with high durability and scalability continues to be a pressing research priority in both academia and industry.

Moreover, conventional superamphiphobic coatings are predominantly prepared using volatile organic solvents (VOCs), such as ethanol,^22,23 esters,²⁴ ketones,^25,26 benzene series²⁷ and fluorinated solvents^28,29 to help dispersion of fluorinated compounds. While effective, these solvents pose serious health and environmental concerns, limiting the sustainable development of the field. In response, growing efforts have focused on the development of waterborne superhydrophobic or superamphiphobic coatings as eco-friendly alternatives. Most existing studies have primarily focused on the development of waterborne superhydrophobic coatings,³⁰ while the advancement of waterborne superamphiphobic coatings is very challenging. A major challenge in the field of waterborne superamphiphobic coatings is the intrinsic incompatibility between low-surface-energy materials³¹ and aqueous systems due to larger surface energy mismatches compared with waterborne superhydrophobic coatings.³² To address this, special surfactants are often introduced to promote dispersion by reducing the surface tension of the aqueous medium.^30,33–36 Although the introduction of surfactant technologies has helped address the compatibility issues between low-surface-energy materials and aqueous media, achieving totally waterborne superamphiphobic coatings remain a significant challenge, especially those with high robustness.

In this work, we report the fabrication of fully waterborne superamphiphobic coatings based on waterborne polyurethane (WPU) and fluorinated polysiloxane-modified silica nanoparticles (F-POS@SiO₂) nanoparticles. The core innovation is the dual role of the fluorinated surfactant, which uniquely mediates the acid-catalyzed hydrolytic condensation and assembly of silanes in water while ensuring low surface energy. This synergistic approach eliminates volatile organic compounds, directly addressing a major sustainability challenge. The resulting coatings exhibit a hierarchical micro-/nanostructure that confers exceptional static and dynamic liquid repellency, high-pressure resistance, and outstanding durability. Comprehensive testing confirms that the coatings exhibit remarkable chemical stability, weather resistance, self-cleaning behavior, and anti-icing performance, making them versatile and environmentally friendly candidates for practical superamphiphobic applications.

Results and discussion

Preparation and characterization of WPU/F-POS@SiO₂ superamphiphobic coatings

Fig. 1a illustrates synthesis of the F-POS@SiO₂ nanoparticles and the pathway for constructing the WPU/F-POS@SiO₂ superamphiphobic coatings. First, a water-based synthesis strategy was employed to construct the F-POS@SiO₂ nanoparticles with low surface energy. Without the use of organic solvents, the F-POS@SiO₂ nanoparticles were achieved by introducing tetraethoxysilane (TEOS), 1H,1H,2H,2H-perfluorodialkyltriethoxysilane (PFDTES), and the water-dispersible fluorinated surfactant FS-3100 into an acidic aqueous phase. During the reaction, FS-3100 not only stabilized the reaction system but also facilitated the formation of a stable fluorinated shell on the nanoparticle surface, imparting superhydrophobic and superoleophobic properties. The TEM images proved conclusively the successful coating of fluorinated functional groups onto the SiO₂ nanoparticles and formation of free F-POS (Fig. 1b and c). Next, the F-POS@SiO₂ nanoparticles were integrated with the WPU adhesive to fabricate the totally waterborne WPU/F-POS@SiO₂ superamphiphobic coatings. The F-POS@SiO₂ particles were uniformly deposited onto the WPU-coated substrates via a spraying process, forming coatings with a dense and hierarchical micro-/nanostructure (Fig. 1d).

Fig. 1 (a) Schematic preparation of the WPU/F-POS@SiO₂ superamphiphobic coatings. TEM images of (b) SiO₂ and (c) F-POS@SiO₂ nanoparticles. (d) SEM image of the WPU/F-POS@SiO₂ coating.

Fig. 2 shows the effects of different surfactants (surfactant-free, FS-61, Zonyl321, and FS-3100) on the F-POS@SiO₂ suspensions and the WPU/F-POS@SiO₂ coatings. The F-POS@SiO₂ suspensions prepared with different surfactants exhibited significant differences in sedimentation behaviour (Fig. 2a). After standing for 6 h, the surfactant-free suspension had the fastest sedimentation rate, indicating the poorest dispersion stability. In contrast, the suspensions prepared with FS-61 and Zonyl321 showed moderate sedimentation rates, while the suspension with FS-3100 sedimented the slowest. Furthermore, particle size and TEM analyses revealed that the F-POS@SiO₂ particles prepared with FS-3100 had the smallest particle size, a more uniform size distribution, and lighter agglomeration (Fig. 2c–f and Fig. S1). This result can be attributed to the surfactant's ability to reduce the surface energy of F-POS@SiO₂ and inhibit particle agglomeration. The FS-3100-based coating exhibited the lowest surface free energy among all formulations, which directly corresponds to its optimal performance (Table S1). Moreover, the FS-3100-based coating exhibited the best superamphiphobicity (Fig. 2b). The CA_n-hexadecane was 163.4°, and the SA_n-hexadecane was only 4.1°, demonstrating excellent superamphiphobicity. The surfactant-free coating exhibited the lowest CA_n-hexadecane and the highest SA_n-hexadecane. SEM images of the coatings further confirmed the impact of different surfactants on the surface microstructure (Fig. 2g–j). The surfactant-free coating exhibited significant particle aggregation on the surface, while the coating prepared with FS-3100 showed a more uniform micro-/nanostructure, resulting in the best superamphiphobicity. The surfactant improves particle dispersion by reducing inter-particle attraction, promoting the formation of a more uniform microstructure on the coating surface, which in turn enhances superamphiphobicity.

Fig. 2 (a) Photographs of the F-POS@SiO₂ suspensions prepared with different surfactants. (b) CA and SA of n-hexadecane on the WPU/F-POS@SiO₂ coatings prepared with different surfactants. (c)–(f) TEM images of the F-POS@SiO₂ nanoparticles prepared with different surfactants and (g)–(j) SEM images of the WPU/F-POS@SiO₂ coatings prepared with different surfactants. Data in (b) are shown as mean ± SD, n = 5.

To optimize the hierarchical micro-/nanostructure essential for superamphiphobic surfaces, a series of the FS-3100-based WPU/F-POS@SiO₂ coatings were fabricated by increasing the concentration of SiO₂ nanoparticles. At low concentration (1.09 mg mL⁻¹), the coating showed incomplete coverage with irregularly distributed particles and visible flat areas, resulting in insufficient roughness (R_a = 1.16 µm) (Fig. 3a and f). With increasing the SiO₂ concentration up to 5.54 mg mL⁻¹, the surfaces showed distinct aggregation structures of micro-/nanoparticles, and the surface roughness (R_a) increases to 1.58 µm (Fig. 3c and g). The rough surface, in combination with low surface energy materials, facilitated stable formation of air pockets, reducing the contact area between liquid droplets and the solid surface, thereby significantly improving superamphiphobicity. At this point, the coating exhibited the best superamphiphobicity with a water CA of 163.2° and a SA below 1°. For n-hexadecane, the CA reached 163.0°, and the SA was 4.3° (Fig. 3i and j). When the concentration further increased to 13.09 mg mL⁻¹, although the surface roughness continuously increased to R_a = 2.84 µm (Fig. 3e and h) and the superhydrophobicity remained unchanged, the superamphiphobicity declined significantly. The increased roughness is due to excessive particle accumulation, which decreased the uniformity of the coatings. The decline in superamphiphobicity is most likely attributed to the presence of excessive unmodified or insufficiently fluorinated SiO₂ nanoparticles at high concentration of SiO₂. These under-modified particles expose hydrophilic silanol groups at the coating surface, thereby increasing the overall surface energy.³⁷

Fig. 3 (a)–(e) SEM images of the WPU/F-POS@SiO₂ coatings prepared with varying SiO₂ concentrations. (f)–(h) 3D surface profiles of the WPU/F-POS@SiO₂ coatings with varying SiO₂ concentrations. (i) Variation of CA_water and SA_water and (j) CA_n-hexadecane and SA_n-hexadecane of the WPU/F-POS@SiO₂ coatings with SiO₂ concentration. Data in (i) and (j) are shown as mean ± SD, n = 5.

To elucidate the surface chemical composition, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) mapping analyses of the WPU/F-POS@SiO₂ coating were conducted. The XPS survey spectrum confirmed the presence of key elements including fluorine (F), oxygen (O), carbon (C), and silicon (Si), indicative of the fluorinated and siloxane components into the coating (Fig. 4a). The high-resolution C1s spectrum further revealed multiple chemical environments, including -CF₂ (∼290.6 eV), -CF₃ (∼292.9 eV), and C–C backbones (∼284.8 eV) (Fig. 4b), verifying the presence of fluorinated moieties critical for low surface energy. Complementary FTIR analysis further corroborated these findings (Fig. 4c). The bands at 1210 and 1147 cm⁻¹ are attributed to symmetric and asymmetric stretching of C–F groups, while the peaks at 811 and 1106 cm⁻¹ are associated with Si–O–Si bonds, confirming the SiO₂ network structure. Furthermore, the EDS elemental mapping revealed uniform distribution of C, F, O, and Si elements over the coating surface (Fig. 4d), indicating consistent chemical composition throughout the coatings. High uniformity is particularly important for maintaining consistent surface energy across the coating. Collectively, these results confirmed that the WPU/F-POS@SiO₂ coating achieved excellent superamphiphobicity through a synergistic combination of low-surface-energy fluorinated groups and a stable, hierarchical micro-/nanostructure.

Fig. 4 (a) XPS survey spectrum, (b) high-resolution C 1s spectrum, (c) FTIR spectrum and (d) elemental mapping of the WPU/F-POS@SiO₂ coating.

Moreover, the coating demonstrated excellent versatility and adhesion across diverse substrates, including magnesium alloy, stainless steel, aluminum alloy and copper alloy, achieving CA_n-hexadecane exceeding 154.0° and SA_n-hexadecane below 10° (Fig. S2 and Table S2).

Wetting properties of WPU/F-POS@SiO₂ coatings

To evaluate the liquid repellency of the WPU/F-POS@SiO₂ coating, both static and dynamic wettability tests were performed. As shown in Fig. 5a, the water and n-hexadecane droplets showed near-spherical shape. The water and n-hexadecane rebound behavior on the coating demonstrated a low adhesion nature of the surface (Fig. 5b and c). Immersion tests in water and n-hexadecane revealed that the coating maintained a silvery appearance due to retained air layers, known as the plastron effect, which prevented direct liquid penetration and supported long-term repellency under submerged conditions (Fig. 5d and e). All these phenomena demonstrated high repellency to both high and low surface tension liquids with minimal solid–liquid contact area and stable Cassie–Baxter states.

Fig. 5 (a) Water and n-hexadecane droplets on the WPU/F-POS@SiO₂ coating. (b) and (c) Bouncing of water and n-hexadecane jets on the coating. (d) and (e) Resistance of the coating to liquid infiltration. (f) High-speed snapshots showing water droplet rebound for four consecutive bounces on the coating and (g) enlarged sequence of the initial rebound. (h) Height-time trajectory of a bouncing water droplet on the coating over multiple cycles. (i) Impact of a water droplet released from a height of 1 m on the coating.

Dynamic bouncing behavior was assessed via high-speed imaging (Fig. 5f) A 10 µL water droplet dropped from 1 cm height underwent multiple continuous rebounds without pinning, confirming extremely low hysteresis and energy dissipation. The detailed bounce sequence showed an initial rebound height of ∼3.60 mm (Fig. 5g), and the trajectory over time illustrated consistent bouncing behavior up to 10 cycles before attenuation (Fig. 5h). Additionally, the coating could withstand the impact of a 10 µL water droplet released from 1 m height without any adhesion or impalement (Fig. 5i). Overall, these results demonstrated that the coating possessed excellent dynamic superamphiphobicity, crucial for applications in anti-fouling and self-cleaning, etc.

The coating's excellent static and dynamic superamphiphobicity enabled effective self-cleaning, repelling both water-based (e.g., muddy water) and oil-based (e.g., n-hexadecane) contaminants without wetting or adhesion (Fig. S3a and b). Dust and Cu(NO₃)₂ powders were effortlessly removed by rolling water droplets (Fig. S3c and d), leaving no residue-attributed to the hierarchical roughness, low surface energy, and the Cassie–Baxter state that minimized contact. These results demonstrate robust, force-free self-cleaning performance.

Mechanical robustness of WPU/F-POS@SiO₂ coatings

Mechanical robustness is a key prerequisite for the practical implementation of superamphiphobic coatings. To assess the mechanical durability of the WPU/F-POS@SiO₂ coating, two representative tests were performed: Taber abrasion and tape peeling. As shown in Fig. 6a, even after 100 cycles Taber abrasion under a 125 g load, the coating maintained a high CA_water >150° with an increase in SA_water from ∼3° to ∼22°, suggesting that the low surface energy and roughness were mainly preserved. Similarly, under repeated tape peeling (Fig. 6b), the coating retained its superhydrophobic character up to 200 cycles, though the SA_water gradually increased due to surface microstructure damage. After these two tests, surface morphology of the coating was analyzed via SEM. After 100 cycles Taber abrasion, the coating showed localized flattening and partial nanoparticle loss, but the overall hierarchical rough texture remained (Fig. 6c). After 200 cycles tape peeling (Fig. 6d), the coating surface showed denser packing and some compaction, but still preserved sufficient micro-/nanoscale features to sustain the Cassie–Baxter state. Even after being subjected to a water jet impact (4.3 m s⁻¹) for 10 min, the coating maintained a CA_water >150° and a SA_water <10° (Fig. S4). These results demonstrate excellent mechanical resilience of the coating, attributed to strong adhesion between the F-POS@SiO₂ network and WPU as well as the embedded hierarchical architecture, which resisted structural collapse even under repetitive mechanical stress.^38,39

Fig. 6 Variations of CA_water and SA_water on the WPU/F-POS@SiO₂ coating during (a) Taber abrasion and (b) tape peeling. SEM images of the WPU/F-POS@SiO₂ coating after (c) 100 cycles Taber abrasion and (d) 200 cycles tape peeling. Data in (a) and (b) are shown as mean ± SD, n = 5.

Chemical and environmental durability of WPU/F-POS@SiO₂ coatings

The long-term chemical stability of the WPU/F-POS@SiO₂ coating was evaluated under various harsh conditions, including exposure to corrosive chemicals, thermal treatment, UV irradiation, and natural outdoor environments. Due to potential degradation of surface structure and chemical composition, superamphiphobic coatings are typically prone to performance loss in such scenarios. However, the F-POS@SiO₂ coating demonstrated remarkable resistance to chemical and environmental stress.

As shown in Fig. 7a, when monitored on the same sample, the coating maintained high CA and low SA for n-hexadecane even after immersion in 0.1 M HCl and 0.1 M NaCl solutions for up to 6 h. This resilience is primarily attributed to the formation of a stable air cushion at the coating-liquid interface, which effectively reduces the contact area and limits corrosion. Chemical resistance was further assessed by prolonged immersion in organic solvents. Notably, the coating retained superamphiphobicity (CA_n-hexadecane >150°, SA_n-hexadecane <10°) after 77 d in acetone and 45 d in acetate (Fig. 7b). This exceptional stability is a result of the chemical inertness of the coating, particularly due to the presence of strong C-F bonds in the fluoro-functionalized surface.⁴⁰ Furthermore, thermal durability was evaluated by heating the coating at 200 °C for 8 h, after which the coating retained CA_n-hexadecane >150° and SA_n-hexadecane <11.5°, confirming excellent thermal stability (Fig. S5). UV aging resistance was evaluated under continuous exposure to 365 nm UV light at 12 W. As shown in Fig. 7c, the coating exhibited only a slight degradation in superamphiphobicity after 144 h of irradiation, maintaining CA_n-hexadecane >150° and SA_n-hexadecane <20°, indicating robust photostability.

Fig. 7 CA_n-hexadecane and SA_n-hexadecane of the WPU/F-POS@SiO₂ coating after immersion in various (a) corrosive solutions and (b) organic solvents. Variation of CA_n-hexadecane and SA_n-hexadecane of the coating during the (c) UV irradiation test and (d) outdoor exposure test. Data are shown as mean ± SD, n = 5.

Finally, outdoor durability was tested under real environmental conditions up to 30 d. CA_n-hexadecane and SA_n-hexadecane did not show any obvious change. As shown in Fig. 7d, despite a gradual increase in the SA_n-hexadecane up to ∼25°, the CA_n-hexadecane remained ∼152°, suggesting that the coating retained high superamphiphobicity even in complex and unpredictable outdoor environments. The higher sensitivity to low surface tension liquids such as oils is likely due to structural degradation of the micro-/nanostructure under environmental exposure. Overall, the excellent chemical and environmental durability of the coating is attributed to its low surface energy, hierarchical surface morphology, and the intrinsic stability of the fluorinated SiO₂ network.

Anti-icing properties of WPU/F-POS@SiO₂ coating

The anti-icing performance of the WPU/F-POS@SiO₂ coating was evaluated by observing the freezing dynamics of dyed water droplets and measuring ice adhesion strength under repeated icing/deicing cycles (Fig. 8). Under –10 °C and 60% RH environment, a blue-dyed water droplet froze within ∼93 s on the bare Al plate (Fig. 8a). In contrast, on the WPU/F-POS@SiO₂ coated Al plate (Fig. 8b), freezing was significantly delayed to ∼236 s, more than 2.5 times longer. The statistical results in Fig. 8c confirm this enhancement, indicating that the low thermal conductivity and air-pocket of the porous superamphiphobic coating reduced heat transfer from the substrate.^11,41 The initial ice adhesion strength on the coated Al plate was as low as ∼25 kPa (Fig. 8d), which is markedly lower than that of the WPU coated Al plate (∼95.3 kPa) and bare Al plate (∼230 kPa) (Fig. S6). Even after 5 icing/deicing cycles, the adhesion increased gradually but remained within acceptable levels (∼65 kPa). Even after 5 icing/deicing cycles, the coating maintained a high CA_water >150° and low SA_water <10°. This demonstrates the coating's robustness and durability in resisting ice accumulation and facilitating easy removal. The prolonged freezing time and reduced ice adhesion can be attributed to the stable Cassie–Baxter state and low surface energy of the fluorinated polysiloxane-modified coating.⁴² The hierarchical roughness can effectively suppress nucleation sites and lower the solid–liquid interfacial contact area.⁴³

Fig. 8 Freezing process of water droplets colored with dyed blue using methylene blue on the (a) bare Al plate and (b) WPU/F-POS@SiO₂ coated Al plate in the −10 °C and 60% relative humidity (RH) environment. (c) Freezing delay time of water droplets on bare and coated Al plates. (d) Variations of ice adhesion strength on the WPU/F-POS@SiO₂ coated Al plate with icing/deicing cycles. (e) Variations of CA_water and SA_water on the WPU/F-POS@SiO₂ coated Al plate with icing/deicing cycles. Data in (c), (d) and (e) are shown as mean ± SD, n = 5.

Conclusions

In summary, we have successfully developed fully waterborne robust superamphiphobic coatings composed of WPU and F-POS@SiO₂. The key innovations include the synthesis of F-POS@SiO₂ in fully aqueous conditions, the use of a fluorinated surfactant to optimize dispersion and surface structuring, and a straightforward spray-coating method compatible with scalable production. The resulting coatings demonstrate high repellency toward both water and low-surface-tension liquids (e.g., n-hexadecane), with water and oil CAs exceeding 160° and SAs below 5°. Comprehensive testing confirmed the coatings’ strong mechanical resilience (withstanding abrasion and tape peeling), outstanding chemical and environmental durability (resistance to acids, bases, solvents, UV exposure, and outdoor weathering), and good anti-icing performance. This study not only advances the design of eco-friendly waterborne superamphiphobic coatings but also provides a scalable, industrially viable solution for applications demanding extreme liquid repellency and durability.

Experimental section

Preparation of F-POS@SiO₂ aqueous dispersion

The F-POS@SiO₂ aqueous suspension was synthesized via an acid-catalyzed hydrolytic condensation reaction involving TEOS and PFDTES in the presence of SiO₂ nanoparticles. Typically, 0.5 mL of surfactant (FS-3100 or others) was first dispersed into 44.5 mL of deionized water and stirred for 10 min. Subsequently, 0.15 mL of TEOS and 0.5 mL of PFDTES were added sequentially into the solution, followed by an additional 10 min of magnetic stirring. Next, 0.25 g of hydrophilic SiO₂ nanoparticles were introduced into the mixture, and the dispersion was subjected to ultrasonication for 5 min to promote uniform particle distribution. After stirring for another 10 min, 0.25 mL of HCl was added as a catalyst to initiate hydrolysis and condensation reactions. The reaction mixture was continuously stirred at 600 rpm at room temperature for 48 h, resulting in the formation of a stable, homogeneous F-POS@SiO₂ aqueous suspension.

Fabrication of WPU/F-POS@SiO₂ superamphiphobic coatings

The superamphiphobic coatings were fabricated via a straightforward spray-coating process. Firstly, 10 g of the WPU adhesive was diluted in 10 g of deionized water by stirring for 30 min. Then, the Al plates (∼100 cm²) were sequentially ultrasonicated in ethanol and deionized water for 15 min each to remove organic contaminants and particulate matter. After drying under a N₂ stream, 1.0 mL of the diluted WPU adhesive was spray-coated onto the pre-treated Al plates using a pneumatic spray gun (SATA 4400 B) equipped with a 1.2 mm nozzle. The spraying was performed at a controlled air pressure of 0.15 MPa and a fixed distance of 15 cm, maintaining a perpendicular orientation to the substrate surface. The WPU layer was then allowed to air-dry at room temperature (∼20 °C) for 30 min. Next, 3.0 mL of the prepared F-POS@SiO₂ aqueous suspension was uniformly sprayed onto the WPU layer using the identical spraying parameters. After spraying, the coated substrates were allowed to cure at room temperature for 24 h to complete the formation of the WPU/F-POS@SiO₂ superamphiphobic coatings.

Author contributions

Yongtao Ren: investigation, methodology, formal analysis, writing original draft, and writing – review & editing; Bucheng Li and Junping Zhang: conceptualization, data analysis, writing and editing, and supervision.

Conflicts of interest

The authors declare no conflict of interest.

Data availability

The data supporting the findings of this study are available within the article and the supplementary information (SI). Supplementary information: detailed experimental procedures, supplementary Fig. S1–S6 and Tables S1–S2. See DOI: https://doi.org/10.1039/d5nh00516g.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (22275200), Gansu Provincial Natural Science Foundation (23JRRA580, 23JRRA600, and 25JRRA480), Gansu Province Top Leading Talents Program, and the Central Government-Guided Local Science and Technology Development Fund of Gansu Province (25ZYJA013).

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