A Simple Method to Prepare Superhydrophobic Surfaces Based on Bamboo Cellulose, and an Investigation of Surface Properties

Abstract

The present work introduces a sustainable, low-carbon method to fabricate durable, non-toxic superhydrophobic surfaces using bamboo-derived cellulose. Uniform TEMPO-carboxylated cellulose particles (TOC-Ps), approximately 2 μm in diameter, were synthesized through thermal polymerization and spray drying. These particles, featuring a nano-scale convex structure formed by intertwined TOC nanofibers, were applied to substrates and modified with low-surface-energy materials to achieve superhydrophobicity. At an optimal TOC-P mass ratio of 6%, the surface displayed a water contact angle of 156.2° and a sliding angle of 7°. The coating maintained superhydrophobicity after extensive mechanical testing—120 cm of abrasion, 100 bending cycles, and continuous trampling—and exhibited robust chemical stability across harsh conditions, including subjection to high temperatures, UV irradiation, and corrosive solutions (pH 2–12). The hierarchical micro–nano structure was found to enhance both hydrophobicity and durability, offering an environmentally friendly alternative for self-cleaning surfaces, textiles, and building applications.

1. Introduction

Superhydrophobic surfaces, defined by water contact angles exceeding 150° and sliding angles falling short of 10° [1], which can be induced by simulating the hierarchical geometry of substances with low surface energy, have attracted significant attention in materials science due to their potential in applications such as self-cleaning [2,3], anti-fouling [4,5], anti-icing [6,7], oil separation from water, and corrosion resistance [8,9]. These surfaces, inspired by natural phenomena like the lotus effect, enable water droplets to roll off, removing contaminants and enhancing material functionality [10]. However, conventional fabrication methods often rely on fluorinated compounds or energy-intensive processes which pose environmental and health risks and contribute to carbon emissions [11]. As global demand for sustainable technologies grows, there is an urgent need for eco-friendly alternatives that maintain high performance while adhering to principles of green chemistry [12].

Cellulose, the most abundant biopolymer on Earth, offers a promising solution. Due to its reproducibility and high mechanical strength [13,14,15], cellulose is considered a very promising candidate material for the fabrication of superhydrophobic surfaces [16,17,18]. Among cellulose sources, bamboo is particularly advantageous because of its rapid growth, high cellulose content, and sustainability [19,20,21]. Recent studies have demonstrated the potential of bamboo-derived cellulose in creating superhydrophobic materials. For instance, Liu et al. developed a superhydrophobic bamboo cellulose foam for oil/water separation, highlighting its environmental benefits [22]. Similarly, Wu et al. fabricated a superhydrophobic film from Moso bamboo cellulose nano-fibrils, showcasing its self-cleaning and waterproof properties [23]. At present, most of the cellulose-based superhydrophobic coatings reported in the literature are obtained by modifying cellulose on the surface of biomass substrates using methods such as grafting long-chain silane [24,25], esterification [26,27], and covering low-surface-energy substances [6,28]. These modification methods are suitable for the treatment of small specimens. However, the application of superhydrophobic surfaces is not limited to this. One of the most important applications of superhydrophobic surfaces is improving the anti-fouling performance of indoor and outdoor surfaces by spraying large areas of various surfaces [29,30,31]. The key problem with applying a superhydrophobic coating based on cellulose to the surface of inorganic materials is poor mechanical durability [16,32,33,34]. Compared with the above-mentioned cellulose modification methods, 2,2,6,6-tetramethylpiperidinyl-1-oxyl(TEMPO)-mediated oxidation is a mild and selective method that operates under ambient conditions, preserving the structural integrity and mechanical strength of cellulose while introducing carboxyl groups specifically at the C₆ position of glucose units. Furthermore, TEMPO oxidation aligns with principles of green chemistry, as it employs environmentally benign reagents and generates minimal by-products, reducing the ecological footprint of the fabrication process. Using TEMPO to modify bamboo-derived cellulose might enable the production of superhydrophobic surfaces that are not only high-performing but also environmentally friendly and mechanically robust.

Herein, we propose a novel method to fabricate durable, non-toxic, low-carbon-emission superhydrophobic surfaces using bamboo-derived cellulose. By transforming cellulose into TEMPO-carboxylated particles (TOC-Ps) through thermal polymerization and spray drying, followed by surface modification with low-energy materials, we developed a coating with a clear micro–nano hierarchical structure that achieved a water contact angle of 156.2° and exhibited exceptional mechanical and chemical stability. The resulting surfaces maintained superhydrophobicity under rigorous conditions, including sandpaper abrasion, bending, and exposure to harsh chemicals, due to the intertwined and embedded structure of the TOC-Ps, thus making them potentially suitable for widespread application in products such as self-cleaning glass, textiles, and building materials.

2. Experimental Section

2.1. Synthesis of Materials

Bamboo (5-year-old) was harvested in Hangzhou China. The following substances were procured from Tianjin Sinopharm Chemistry Co., Ltd. (Tianjin, China): 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO), sodium bromide (NaBr), sodium hypochlorite (NaClO), and sodium hydroxide (NaOH). Hydrochloric acid (HCl), methyltrichlorosilane (MTCS), toluene, ethanol, and n-hexane were obtained from McLean Chemical Reagent Co., Ltd. (Shanghai, China) Water-based wood paint (with acrylate as its main component) was purchased from Hangzhou Heshi Wood New Material Co., Ltd. (Hangzhou, China) All the above chemical reagents were analytical grade.

2.1.1. Fabrication of TOC Particles

Bamboo-derived TEMPO carboxylated cellulose nanofibers were obtained according to methods previously reported [35]. A 2 wt% TOC-nanofiber aqueous solution was added to prepare TOC-Ps using the following spray drying mechanism: Firstly, 2 wt% TOC aqueous solution is sent into the atomizer at a certain speed to form droplets with diameters of several tens of micrometers. The atomized TOC droplets enter the drying chamber and meet the preheated hot air (the temperature of the heating tube is set to 240 °C to ensure that the temperature of the air in contact with the droplets is between 95 and 100 °C). The drying chamber is similar to the internal-combustion chamber of a car engine. The atomization of the TOC solution is like the atomization of gasoline after passing through a nozzle. In spray drying, unlike in a car engine, hot air is introduced and there is no ignition process. In the drying chamber, hot air flows at a speed of 5 m/s and comes into full contact with the fog droplets. Hot air transfers heat to the TOC droplets, causing the water in the droplets to evaporate. Due to the continuous evaporation of water inside the droplets, the droplets gradually contract, and the solid and liquid phases separate; TOC then accumulates, forming particles with a rough surface structure on a micrometer-to-nanometer scale. The process is shown in Scheme 1. In this study, the working parameters of the spray dryer were as follows: fan speed: 90%; unclogging the needle: once every 10s; peristaltic pump speed: 20%.

2.1.2. Fabrication of Superhydrophobic Surface

Superhydrophobic coating materials are applied to glass materials. In this study acrylic waterborne paint was first sprayed onto the surface of a glass slide and allowed to stand for 2 min. Then, an ethanol suspension of the TOC-Ps (with mass percentages from 1–8 wt%) was sprayed onto the surface of the substrate using a spray gun with a spray distance of about 50 cm and a spray volume of 10 mL. The air pressure of the small air pump was controlled at about 0.8 MPa.

A 0.1 mL amount of methyltrichlorosilane was added to 100 mL anhydrous toluene with the above specimens and sealed with a preservative film. Experimental conditions were as follows: a magnetic stirring speed of 300 r/min, and a reaction time of 50 min. During the induction period, a drop of deionized water was added every 5 min with a syringe (needle diameter 0.3 mm). After the reaction, the samples were washed five times with anhydrous toluene and anhydrous ethanol separately, and dried at 80 °C. The preparation process is shown in Scheme 1.

2.2. Measurements and Characterizations

The surface morphology of the samples was studied by means of a scanning electron microscope (SEM, Hitachi S4800, Hitachi, Ibaraki, Japan). The contact angles and sliding angles were detected with a contact angle measurement instrument (SL200, KINO, Somerville, MA, USA). The chemical structure was characterized by a Fourier infrared spectrometer (Nicolet Magna-IR 750, Nicolet, Madison, WI, USA). The wavenumber spectrum of the measurements was found to span a range of 4000–500 cm⁻¹.

2.3. Mechanical Durability and Chemical Stability Experiments

Sandpaper rubbing, repeated washing, and repeated bending were used to evaluate the durability and stability of the superhydrophobic surface. To study friction resistance, weight loads of 20 g, 50 g, and 100 g were used in conjunction with 500-grit sandpaper. The slide was moved at a speed of 1 cm/s.

The chemical stability test was carried out by immersion in different solutions (pH = 2–13) for 24 h. Following a thorough process of rinsing and immersion using deionized water, the superhydrophobic surface was dried at 100 °C for a period of two hours. The CA was then measured immediately.

3. Results and Discussion

3.1. Fabrication of the TOC Particles and Superhydrophobic Surface

The process by which TOC nanofibers change from wet state to solid particles involves many disciplines such as fluid mechanics, thermodynamics, and kinetics. The formation mechanism is complex. According to Huinink et al., the morphology of particles prepared by spray drying of nanosuspensions is determined by the mass transfer rate and the drying rate of nanomaterials which can be expressed by the Pe number [36] calculated as in Equation (1):

$$Pe{\displaystyle \frac{t_{diff}}{t_{dry}}}={\displaystyle \frac{R^2}{{Dt}_{dry}}}={\displaystyle \frac{R^2}{t_{dry}}}\times {\displaystyle \frac{6\pi \eta r}{k_{B}T}}$$

(1)

where t_diff is the mass transfer time; t_dry is the drying time; R is the radius of the atomized droplet; D is the total diffusion coefficient of nanomaterials; η is the solvent viscosity; T is the solute temperature (K); r is the radius of nanoparticles; and k_B is the Boltzmann constant (1.38 × 10⁻²³ J/K).

The Pe number can be used to represent morphological changes in prepared particles. However, because the spray drying process is a ‘black box’ function, an accurate drying time cannot be directly measured by experiments. Therefore, the time t_dry-Max during which the droplet stays in the spray dryer can be used instead. This can be calculated using Equation (2):

$$t_{dry\text{-}max}={\displaystyle \frac{h}{v_j}}={\displaystyle \frac{hp\pi r^2}{V_m}}$$

(2)

where h is the height of the spray drying collector; v_j is the velocity of the droplet into the collector; V_m is the velocity of the suspension; r is the radius of the atomized droplet; p is the density of the suspension.

When the drying process is very slow, t_diff > t_dry, and the evaporation of water is relatively slow. Therefore, the TOC nanofibers remaining at the gas–liquid interface of the droplets migrate from the gas–liquid interface to the inside of the droplets before the end of drying. As the drying progresses, the water in the droplets continues to evaporate, and the droplets always maintain uniform shrinkage in all directions. The TOC nanofibers then accumulate and interlace to form relatively uniform spherical particles.

When the drying process is very short, t_diff < t_dry, and the water evaporates very quickly. During this time, the TOC nanofibers at the gas–liquid interface of the droplet do not have enough time to migrate from the gas–liquid interface to the inside of the droplet, but are immediately dried and accumulated at the gas–liquid interface of the droplet. With the rapid and continuous evaporation of water, TOC nanofibers accumulate at the gas–liquid interface of the droplets, and finally form a shell formed by the interlaced nanofibers, which encapsulates the remaining nanofiber suspension. As the drying progresses, water continuously evaporates from the gap between the TOC nanofibers in the shell, driving the TOC nanofibers inside the droplet to continuously move towards the outside of the droplet, and finally accumulates on the inner surface of the shell. After the formation of the shell at the gas–liquid interface of the droplet, the droplet volume continues to shrink as the water continues to evaporate. When the amount of droplet volume reduction is lower than the volume of water evaporated, the solvent forms a concave surface in the shell, so that the droplet is subjected to an outward–inward capillary force. As the drying progresses, the capillary force continues to increase, and the rheological properties of the shell gradually change from viscoelasticity to elasticity. Finally, spherical particles with a local concave structure are formed. The surface structure is dense, entangled and interlaced by TOC nanofibers, forming a micro/nano double coarse structure which showed in Figure 1.

Methyltrichlorosilane exhibits very active chemical properties. Organosilicon compounds can be hydrolyzed in the presence of water. The hydroxyl group replaces the chlorine element in the silane to form a multi-hydroxyl silicon compound CH₃Si(OH)₃, which further dehydrates and condenses, cross-linking to form a polysiloxane. At the same time, the polysiloxane undergoes a dehydration condensation reaction with the hydroxyl groups on the cellulose particles and is fixed on the surface of the cellulose, so that the surface of the cellulose particles is covered with a layer of polysiloxane layer connected by chemical bonds. The modification principle is shown in Figure 2. When the hydrolysis product CH₃Si(OH)₃ of methyltrichlorosilane is cross-linked to produce polysiloxane, three hydroxyl groups on each C atom participate in dehydration condensation, so the polysiloxane skeleton can grow in a three-dimensional direction to form a three-dimensional porous structure. This structure further strengthens the micro/nanostructures on the surface of TOC-Ps, and at the same time exhibits low surface energy, resulting in a superhydrophobic surface.

3.2. Chemical Analysis and Surface Characterization

Firstly, the chemical structure of TOC-Ps before and after modification with methyltrichlorosilane was characterized by FTIR spectroscopy. It can be seen in Figure 3 that in the FTIR spectrum of TOC-Ps before modification, the peaks at 3334 cm⁻¹ and 2870 cm⁻¹ correspond to the stretching vibrations of the –OH group and –CH₂ group [37], respectively. The peak at 1027 cm⁻¹ corresponds to the bending vibration of −OH and the stretching vibration of C–O–C. A strong peak appears at 1732 cm⁻¹, which is the characteristic peak of the carboxyl group in TOC. In the FTIR spectra of TOC-Ps modified by methyltrichlorosilane, two new absorption peaks can be seen at 1273 cm⁻¹ and 781 cm⁻¹, corresponding to the asymmetric stretching vibration of the Si–CH₃ group and the characteristic vibration of the Si–O–Si group, respectively. These results show that methyltrichlorosilane and TOC-Ps are bonded together in the form of chemical bonds.

The microstructure of the TOC-Ps before and after modification was characterized by SEM. In Figure 4a,b, SEM images show TOC nanofibers agglomerated after spray drying into particles with high sphericity and a diameter of about 2 μm. Figure 4c is an SEM image of enlarged TOC-Ps which shows the surface of a particle covered with a dense and fine nanoscale rough structure. This is because when the atomized TOC fiber droplets come into contact with high-heat air, the free water on the surface of the droplets evaporates rapidly, and the surface can cause nanofibers to accumulate on the surface of the droplets. At the same time, the size of the droplets decreases sharply, and the fibers shrink and entangle to form hollow and wrinkled particles.

In Figure 4d,e, it can be seen that the surface of the superhydrophobic coating is composed of micro/nano-scale rough structures, and the surface layer presents a three-dimensional spatial skeleton structure. In addition, countless nano-scale convex bodies can be observed on the spatial skeleton (Figure 4f). This is similar to the structure found on the surface of the lotus leaf, and constitutes the structural basis of the hierarchical size required for the superhydrophobic surface.

3.3. Wettability of TOC-P Superhydrophobic Surface

TOC-Ps have a micro/nano hierarchical structure and so exhibit a certain hydrophobicity after modification with methyltrichlorosilane. In Figure 5a, it can be seen that water droplets are almost tiled on the surface of untreated glass, showing strong hydrophilicity. When the glass surface was coated with water-based paint, the contact angle increased to 50° (Figure 5b). After the pure glass was modified by methyltrichlorosilane, the surface droplets were semi-circular, and the contact angle was further increased to 70° (Figure 5c). In Figure 5d, it can be seen that, after the glass surface was modified by TOC-Ps and methyltrichlorosilane, the water droplets were spherical and the contact angle was 156°, fully demonstrating that the coating had superhydrophobic properties under the synergistic effect of TOC-P micro/nanostructures and low surface modification.

The preparation of the superhydrophobic surface was achieved by means of dispersing TOC-Ps in anhydrous ethanol, followed by application of this dispersion to the treated surface. Therefore, the concentration of TOC-P/ethanol suspension had a direct effect on the wettability of the surface. A single-factor test was carried out with suspension concentration as the variable, and the results are shown in

Table 1. Relationships between concentrations of TOC-Ps and wettability.

TOC-P Concentration (wt%)	Static Contact Angle/CA (°)	Rolling Contact Angle/SA (°)
1 wt%	113.4 (±2.1)°	-
2 wt%	126.6 (±1.7)°	46 (±5)°
4 wt%	143.8 (±0.9)°	25 (±3)°
6 wt%	156.2 (±1.9)°	7 (±2)°
8 wt%	151.3 (±1.1)°	8 (±3)°

. It can be seen that in the concentration range of 1 wt%–4 wt% the surface does not achieve a superhydrophobic effect. This is because the lower concentration makes the surface of the slide incapable of being completely covered by micro/nano bumps, exposing structural defects. When the concentration is greater than 6 wt%, the static contact angle of the slide surface reaches 156.2°, and the rolling contact angle is 7°, so that superhydrophobic properties are exhibited. When concentration increases further, to 8 wt%, the static contact angle decreases and the rolling contact angle increases. This is because excessive concentration leads to the accumulation of particles sprayed on the surface of the substrate, and the surface micro/nano bulge structure is not uniform enough. In addition, the binding force between the stacked TOC-Ps is weak, and it is easy for the outermost particles to fall off, resulting in loss of low-surface-energy substances and a reduction in superhydrophobic properties.

3.4. Mechanical and Chemical Stability and Durability

The wear resistance of a superhydrophobic surface is the main factor affecting its mechanical durability. Figure 6a,b show variations in the contact angle of the superhydrophobic surface with the wear distance. When the wear distance reaches 120 cm, the contact angle of the surface is estimated to be approximately 150°, while the rolling angle is approximately 5°, so that a certain hydrophobic property is maintained and excellent mechanical stability indicated. This is due to the strong bonding force between the adhesive and the cellulose particles, as well as the compact and strong micro/nano structure on the surface of the particles.

In order to test the bending fatigue resistance of the superhydrophobic surface, TOC-Ps were deposited on the filter paper by the spraying method and then modified with methyltrichlorosilane. After several bending cycles, the contact angle within the bending radius of the coating was tested, and the results are shown in Figure 6c. It can be seen that after 100 cycles of bending, the coating still maintains superhydrophobic properties. This is because the siloxane chain of the three-dimensional skeleton structure can resist the mechanical damage caused by wear through the structural regeneration mechanism. At the same time, in order to simulate a real-life damage scenario, individual people weighing 70 kg or above continuously stamped on the superhydrophobic coating for 10 min. After this, the droplets on the coating surface were still spherical, and the contact angle was 149° (Figure 6d).

When considering the use of glass in high-temperature, high-humidity places such as family bathrooms and public saunas, the chemical durability of superhydrophobic surfaces is particularly important. Figure 7a illustrates the influence of hot water immersion on the contact angle of the superhydrophobic coating. After immersion in water at different temperatures, the static contact angle and rolling angle of the coating were almost unchanged, and the contact angle was above 152°. This shows that during the soaking process, although the coating is infiltrated, it is only because the air in the microstructure is squeezed out by water, so that the micro-roughness structure is not destroyed and good water resistance is exhibited.

In glass used for curtain walls of outdoor buildings or for automobile windshields, resistance to rain and snow erosion and aging caused by sunlight directly affect the service life of superhydrophobic surfaces. In order to reflect real-world effects as much as possible, the superhydrophobic surface was either soaked in a rainwater, acid, and base solution or exposed to an ultraviolet environment. The results showed that changing the contact angle of the coating resulted in negligible change following immersion in rainwater for up to 18 h. Generally speaking, cellulose absorbs ultraviolet, inducing aging and degradation to some measure. In this study, the contact angle of the superhydrophobic coating was found to remain above 153° after long-term ultraviolet light irradiation, due to the high energy of the siloxane group. Contrarily, due to the high ultraviolet durability of acrylic water-based paint, high-strength ultraviolet light does not cause such paint to fall off or crack. In addition, the superhydrophobic coating can provide excellent anti-corrosion medium protection. The superhydrophobic coating was immersed in an aqueous solution with a pH value between 2 and 12, and the contact angle was found to decrease in both strong acid and strong alkali environments (Figure 7c). This is mainly because polysiloxane is easy to hydrolyze under strong acid and strong alkali conditions, and strong alkali has a greater impact than strong acid. Therefore, under strong alkali conditions, hydrophobic substances are destroyed in a short time, some particles fall off, and hydrophobicity may even be lost completely.

3.5. Self-Cleaning Properties and Mechanism

In practical applications, superhydrophobic coatings may contact different liquids. In order to verify the universality of superhydrophobic coatings for commonly found liquids, common liquids with different surface tensions, such as green tea, coffee, milk, and mineral water, were selected to measure the corresponding contact angles. It can be seen in Figure 8a,b that droplets of all of the above liquids are spherical on the surface of the superhydrophobic coating and all contact angles are greater than 150°, proving that the superhydrophobic coating is universal for most liquids commonly used in everyday life. The glass slides loaded with superhydrophobic coating and pure glass slides were immersed in a mixture of soil, ink, and sawdust for 20 min and then taken out. It was found that the surface of the superhydrophobic coating was clean, as before (Figure 8c left), while some water droplets and mud remained on the surface of the slide (Figure 8c right), proving the excellent anti-fouling performance of the superhydrophobic coating.

In most reports in the literature, the self-cleaning effect of a superhydrophobic coating is indicated by the fact that water droplets roll off the surface, taking away pollutants (sawdust, dust, etc.) from the surface. In this study, as shown in Figure 9, the modified slide was slightly raised, and it was observed that the water droplets rolled off the surface of the slide and took away the sand on the slide, indicating that the coating had a good self-cleaning effect.

However, self-cleaning should not be achieved by only relying on water droplets to roll off the coating surface, taking pollutants with them. This is especially the case when the superhydrophobic coating is destroyed, the surface micro–nano structure is damaged, and the droplet stops when it rolls to the damaged position, thus losing the self-cleaning effect. In fact, it is easier to achieve the self-cleaning effect using impact rebound behavior of water droplets rather than their rolling behavior. When the droplets impact the superhydrophobic surface, the liquid–gas interface formed during the spreading and retraction process can adhere to the solid particles, and the kinetic energy stored during the impact process can cause the droplets to rebound. The entire ‘adhesion + rebound’ process can take away the solid particles on the coating surface, thereby achieving a self-cleaning effect.

The self-cleaning properties of superhydrophobic coatings can be studied by experiments with water droplets impacting inclined surfaces. In such experiments, Weber numbers are usually used for characterization [38]: the positive-impact Weber number (We_N) and the oblique-impact Weber number (We_T), as expressed as in Formulas (3) and (4):

$${\mathit{We}}_N={\displaystyle \frac{{\rho }_w{V}_N^2{D}_0}{\gamma }}$$

(3)

$${\mathit{We}}_T={\displaystyle \frac{{\rho }_w{V}_T^2{D}_0}{\gamma }}$$

(4)

where ρ_w is the density of the water droplets, which is the surface tension of the water droplets; V_N is the forward impact velocity; and V_T is the tangential impact velocity. Under the premise that ρ_w and γ are determined, the impact Weber number is proportional to the impact velocity. In this study, the self-cleaning effect of water droplet rebound was studied, and the relationship between water droplet rebound with different Weber numbers and the self-cleaning effect was tested. Only a qualitative analysis was performed; therefore, the size of We_N was regulated by changing the vertical distance between water droplets and superhydrophobic surfaces.

Due to the large retreat angle of water droplets on a superhydrophobic surface, retraction kinetic energy can easily overcome surface adhesion energy, so that water droplets rebound and take away dust. Figure 10 shows the process of removing sawdust particles from the superhydrophobic surface of a quilt. Water droplets were dropped freely from heights of 60 mm, 40 mm, and 20 mm onto the surface. In Figure 10a–c, it can be seen that the larger the vertical distance between the water droplet and the superhydrophobic surface is, the greater the gravitational potential energy is, and the faster the droplet falls to the surface, so the higher the We_N is, the larger the area spread on the superhydrophobic surface is, and the more solid particles can be taken away during the rebound process, so that the surface is cleaned.

4. Conclusions

TEMPO-carboxylated cellulose nanofibers were recombined and agglomerated by spray drying technology to prepare spherical particles with a micro–nano hierarchical structure on the surface. Cellulose particles were about 2 μm in size, with surfaces characterized by irregular wrinkles, protrusions, and staggered structures, as well as an intrinsic micro–nano hierarchical structure. These were sprayed on a matrix surface to obtain a superhydrophobic coating. After 120 cm of wear, the contact angle of the superhydrophobic coating was approximately 150°, and the rolling angle was around 5°. Moreover, after up to 100 cycles of bending, the coating still maintained superhydrophobic properties, proving excellent mechanical durability. After soaking in water at different temperatures, the water contact angle of the coating remained above 152°. After long-term UV irradiation, the contact angle remained above 153°. After soaking in a corrosive solution with a pH value between 2 and 12, the water contact angle remained above 150° and the rolling angle remained below 12°, indicating excellent chemical aging resistance. The outstanding finding of the present work is that the micro–nano structure is constructed by the cellulose nanofibers themselves, reducing the need for synthetic materials.