Synthesis of Hierarchical Superhydrophilic/Superhydrophobic Nanostructured Surfaces for Oil/Water Separation

Surface wetting, the phenomenon where a liquid spreads or adheres to a solid surface, plays a crucial role in both natural and technological fields. This study focuses on elucidating the relationship between surface properties and wetting behavior, emphasizing the significance of hierarchical structures. A 3D hierarchical structure is created by controlling shape and size through electroplating and chemical reactions, adjusted by current intensity, ammonium persulfate, and ammonium hydroxide concentrations. This modification is achieved by modifying the surface's chemical properties. This control directly impacted the surface wetting properties, providing a means to regulate wetting behavior by altering surface structure. Through control of surface chemistry, a superhydrophilic surface is able to successfully create with a contact angle of 0° and a superhydrophobic surface with a contact angle of 171.3.


Introduction
[3] This poses serious environmental pollution and has negative impacts not only on resources but also on human health.[13] Additionally, when incidents like crude oil spills occur, it is essential to have technologies with high separation efficiency, selectivity, stability, and low risk of secondary pollution.[16] This technology is associated with wettability, playing a crucial role.
Wettability [17] is a characteristic of a solid surface that indicates the wetting phenomenon when a liquid contacts the surface.It is determined by the interactions between substances, representing how well a liquid makes contact with a solid surface.Wettability can be broadly classified into two categories: hydrophilicity if the surface contact angle is less than 90°, and hydrophobicity if it is greater than 90°.These properties, influenced by the chemical characteristics of materials and surface roughness, are receiving considerable interest not only in oil/water separation but also in various industrial fields, [18][19][20][21] providing effects such as self-cleaning, [22][23][24] anti-reflective coatings, [25] corrosion prevention, [26,27] and anti-fogging. [28,29]Surface wettability determine by the chemical properties of the material and the roughness of the surface.The chemical property in question is the interfacial surface energy, which is derived from Young's equation, [30] as outlined below.This equation forms the foundation for describing the phenomenon of surface wetting.
Here,  s-g is the solid-gas free surface energy,  s-l is the solidliquid free surface energy, and  l-g is the liquid-gas free surface energy.If the sum of  s-l and  l-g is equal to  s-g , cos  = 1,  = 0°, and the surface energy is considered high.Conversely, a low  s-g theoretically results in  = 180.
cos  w = R cos , R = real surface area projected surface area > 1 Currently, the Wenzel [31] and Cassie-Baxter [32] models are used to account for the roughness of actual solid surfaces.Wenzel's model considers a state where the surfaces of the liquid and solid are in complete contact and incorporates surface roughness as a constant.The resulting equation suggests that hydrophobicity increases with the augmentation of roughness.Conversely, the Cassie-Baxter model assumes that an air gap exists between the liquid and solid surfaces.Here,  c denotes the apparent contact angle,  1 refers to the solid-liquid contact angle and  1 and  2 correspond to the respective surface area fractions of materials 1 and 2. cos [54] However, these approaches come with limitations such as high costs, specific environmental conditions like high temperature and vacuum, instability, complexity, difficulties in alignment, limited resolution, high energy requirements, challenges in control, and issues regarding stability, durability, and productivity, as well as constraints in the selection of metals and materials.
To overcome these limitations, this study focuses on the chemical processes of electrochemical deposition and solution immersion to form nanostructures and coatings.Electrochemical deposition enables the production of uniform and precise metal layers, applicable to various surface shapes and complex structures, allowing for the deposition of intricate particles and structures.Additionally, the deposition rate and electrical conditions adjust to control thickness. [55,56][59] Furthermore, copper sulfate electrolyte offers advantages such as relatively fast plating speed, cost-effectiveness, consistent film strength after plating, and high flexibility. [60,61]he chemical oxidation through solution immersion utilize for surface modification and functionalization of various materials.Precise control over solution parameters such as time, tempera-ture, and concentration enhances the surface stability and durability.
Lastly, the sol-gel process allows for the formation of diverse microstructures, control over shape and particle size, stable dispersion of nanoparticles, high moisture absorption, and regulation of surface roughness.Moreover, it exhibits excellent stability and durability. [62,63]hese processes perform at room temperature and atmospheric pressure, offering characteristics such as high productivity, reproducibility, speed, cost-effectiveness, and the ability to select from various metal materials, making them ideal for mass production in the field of materials engineering.
In this study, micro-and nanostructures were electrochemical formed in a hierarchical structure on a cost-effective copper mesh to maximize the surface roughness and coated with a hydrophobic material, Teflon, to achieve a superhydrophobic surface.To achieve the roughness, the microstructure was first formed by plating pure copper.The surface area was then decreased by creating a copper-based nano rod structure through oxidation, and silica nanoparticles were formed on the rod structure surface to create the hierarchical structure (Figure 1).
After undergoing the three-step process, the water contact angle (WCA) of the bare copper mesh decreased from 130°to 0°a nd creating a superhydrophilic copper mesh (Figure 1C).And after applying the Teflon coating, the WCA increased to 171°, and creating a superhydrophobic copper mesh (Figure 1C').The observed meshes displayed self-cleaning properties, maintained breathability, and exhibited a water separation efficiency surpassing 96%.
This study has effectively demonstrated the potential capabilities of superhydrophilic and superhydrophobic copper meshes in water separation.Additionally, the innovative surface wetting fabrication process developed here is expected to find versatile applications in critical industrial domains such as materials science, biomedical engineering, and energy storage (Figure 1).

Results and Discussion
In the electrochemical plating process, the current density was chosen as the variable for operation.The primary variables in electrochemical plating include current density, electrolyte composition, temperature, and plating duration.Among these, current density significantly influences the thickness and quality of the deposited film.Higher current densities enable faster deposition, resulting in thicker coatings.However, excessively high currents may lead to irregular or diminished quality.Additionally, adjusting the surface characteristics of the plated layer allows for improvements in adhesion and durability.Therefore, current density was chosen as a variable to regulate surface properties and enhance adhesion and durability. [64,65]he electrochemical deposition was conducted using an AC/DC power supply (Model 6621; 50 MHz arbitrary waveform/function generator; Keithley, USA).The morphology of the nanostructure, coated surface was observed using a field emission scanning electron microscope (FE-SEM; Ultra Plus; ZEISS, Germany).
The surface structures formed on the copper mesh were visualized using FE-SEM at different electrochemical deposition current strengths.illustrating the deposition of copper nanoparticles on the copper mesh surface.At lower deposition currents, the deposited particles exhibited a pointed morphology.With an increase in deposition current, these particles transformed into more spherical shapes, altering the ratio of pointed to spherical particles.Simultaneously, there was an augmentation in the quantity of deposited particles, leading to the production of finer particles.Beyond deposition currents exceeding 75 mA, these fine particles aggregated, forming larger structures, on which fine particles were deposited.This evolution in copper nanoparticle deposition concerning current intensity was observed through incremental increases in current intensity.The copper nanoparticles exhibited a finer nature as the current strength amplified, while the quantity of copper increased proportionally to the current flowing through the identical sample size.
The sizing of the copper particles was assessed concerning the current strength.As the current intensified, the particles became finer, transitioning from 725 nm at low current to 250 nm at high current (Figure 3C).Upon dispensing 5 μL onto the deposited copper mesh surface with a SmartDrop Plus (Femtobiomed, Korea), the contact angle exhibited variation corresponding to the current strength, registering 146°at 25 mA (low current strength) and 162°at 100 mA (high current strength).Figure 3B depicts a graph illustrating the sliding angle concerning current strength.At 25 mA, an approximate slope of 11°was observed, while at 100 mA, the slope reduced to 4°.Additionally, the contact angle was monitored over time at a current strength of 100 mA.After 1 minute, copper particles commenced deposition, and the contact angle measured 147°.Subsequently, with continued deposition, the contact angle increased.However, beyond a certain duration, the contact angle ceased to escalate, exhibiting no substantial further alteration.
In the solution oxidation process, the concentration of ammonium persulfate was chosen as the variable for operation.Second, The primary variables in the liquid oxidation process are the concentration of the oxidizing agent, reaction temperature, and oxidation duration.Ammonium persulfate serves as a catalyst or activator, functioning as an oxidizer to generate active oxygen during the oxidation process.Furthermore, it plays a crucial role in generating active oxygen, accelerating chemical reaction rates, and initiating reactions, was selected as a variable. [66,67]igure 4 shows SEM images showcasing the surface of copper nanostructures after oxidation, revealing the growth of Cu(OH) 2 nanorods on the copper mesh.At an ammonium persulfate concentration of 0.01 M, a sheet-like structure was predominant.However, as the concentration increased, the formation of nanorods became more prominent.Beyond concentrations exceeding 0.07 M, the length of nanorods expanded, leading to contact between them.These contacted nanorods formed a mesh-like structure.To investigate the reaction trend from copper nanorods to Cu(OH) 2 concerning ammonium persulfate concentration, the concentration was incrementally increased.It was observed that with the rise in ammonium persulfate concentration, the number of reacting particles increased, accelerating the formation rate of Cu(OH) 2 and resulting in longer Cu(OH) 2 nanorods.
The lengths of the oxidized and grown rods were measured as a function of concentration (Figure 5).At a low ammonium persulfate concentration, the length of the sheets formed was 6 μm.At 0.05 M ammonium persulfate, there was a more pronounced formation of nanorods than sheets, growing up to 8.5 μm.The nanorods at ammonium persulfate concentrations of 0.07 M and higher exhibited intertwining between rods, making precise measurements challenging, yet they reached ≈9.7 μm.Furthermore, the contact angle on the copper mesh surface with grown Cu(OH) 2 nanorods increased from 167°to 170.3°with increasing concentration.However, at concentrations above 0.7 M, due to intertwining between the rods, it decreased to 168.7°.Moreover, the sliding angle decreased with increasing concentration, showing an approximate slope of 4°.It then increased again to around 6°at 0.07 M. Contact angles were measured concerning oxidation process time at 0.05 M concentration, peaking at 170.3°a t 30 minutes.Subsequently, with further progression, the contact angle decreased slightly, but with no significant difference.
In the silica coating process, the concentration of ammonium persulfate was chosen as the variable for operation.Last, The primary variables influencing silica particle formation include precursor concentration, catalysts and activators, reaction  temperature and time, pH, among others.Ammonia solution is commonly used in silica formation and serves as a pH adjuster.It plays a role in both the formation and stabilization of silica particles, inducing silica particle formation and polymerization while maintaining an alkaline environment.Moreover, it affects particle size and dispersion.Aimed at particle formation and stabilization, ammonia solution was chosen as a variable. [68,69]igure 6 shows SEM images displaying silica nanoparticles formed on nanostructures produced via coating.With an increase in ammonium hydroxide concentration, the particles transitioned into spherical shapes, concurrently enlarging in size and resulting in a higher quantity of particles generated.Consequently, uniform-shaped silica nanoparticles were formed.The genesis of these silica nanoparticles is subject to factors like TEOS amount, DI water quantity, ammonium hydroxide concentration, and temperature.To explore SiO 2 reaction tendencies concerning ammonium hydroxide concentration, other variables were held constant while progressively elevating ammonium hydroxide concentration.As the concentration increased, a noticeable escalation in the number of reactive particles was observed, promoting the formation of SiO 2 and confirming an increase in both particle size and quantity.
The size of the silica nanoparticles expanded from 32.5 nm to 69.8 nm (Figure 7C).Concurrently, the contact angle on the copper mesh surface witnessed a rise from 169.2°to 171.3°as silica nanoparticles grew with increasing ammonium hydroxide concentration.However, beyond a concentration of 0.68 M, it decreased to 164°(Figure 7A).This decline in contact angle is attributed to enhanced coverage of the surface by silica nanoparticles as the ammonium hydroxide concentration increased.Correspondingly, the sliding angle exhibited a decreasing trend with rising concentration, showing an approximate slope of 2.5°.Beyond 0.68 M, it subsequently ascended to about 4.3°.When examining the contact angle concerning coating process time at a concentration of 0.51 M, it peaked at 171.3°after 1 hour, subsequently declining to 168°, exhibiting a similar contact angle.
SEM imaging at a magnification of 300x was conducted to quantify the changes in porosity in the copper mesh.The ImageJ software from the U.S. NIH was employed for the quantitative assessment of the area ratio.
The surface structure, porosity, and the size of mesh pores are crucial factors determining the efficiency and functionality of oil/water separation filter.Following each electroplating, oxidation, and coating process, significant changes occurred on the surface, resulting in a significant increase in the measured area ratio of the mesh.Figure 8 visually illustrates these changes in area ratio, where the black area represents the mesh structure, and the white space indicates the gaps within the mesh.
Figure 8A depicts the area ratio of the untreated mesh, confirming a ratio of 50.85%.Figure 8B, captured after the electroplating process, shows an increase in the mesh diameter due to the deposition of copper particles, resulting in an increased area ratio of 80.87%.Additionally, an examination of the border of the black area representing the mesh structure reveals an increase in roughness.After the oxidation process, copper particles grew into rod-like shapes, further filling the mesh pores.Following the final coating process, the area ratio increased by 37% compared to the untreated mesh, reaching 87.13%.The surface roughness of the coated mesh was also observed to be higher than that of the original mesh.
As the processing stages progressed, the grown nanostructures formed a hierarchical arrangement in the mesh, leading to a continuous increase in the area ratio.The structural changes suggest the potential enhancement of the filter's structure and porosity.It implies that such structural alterations could contribute to an improvement in filtration efficiency and performance.The results presented here demonstrate the durability and stability of the coated mesh against pH, temperature, abrasion, bending fatigue (Figure 10).Sandpaper abrasion test was conducted to evaluate the mechanical durability of a coated mesh.The mesh was placed on sandpaper (600 grit and 1000 grit) with a 200 g weight on top.The surface durability was then checked by moving the distance (5, 10, and 15 cm) (Figure 10A).The contact angle was maintained at 150°for all distances when the mesh was abraded with 1000 grit sandpaper.This indicates that the coating is able to withstand the abrasive action of the sandpaper without significantly compromising the surface hydrophobicity.
However, the contact angle remained above 140°at 5 and 10 cm, but decreased to 133.2°when 15 cm was moved on the 600 grit sandpaper (Figure 10A').The decrease in contact angle with decreasing sandpaper grit is likely due to the increased roughness of the sandpaper.The rougher sandpaper is more likely to damage the coating, which can lead to a decrease in surface hydrophobicity.Bending fatigue is a type of mechanical degradation that can occur when a surface is repeatedly bent.This type of degradation lead to the loss of superhydrophobicity, as the surface can become damaged or delaminate.The bending fatigue performance of a coated mesh was evaluated.The mesh was subjected to repeated bending cycles with a radius of curvature of 0.5 mm (Figure 10B).The contact angle was measured after every 10 bending cycles to assess the durability of the surface.The mesh was clamped at two points and then bent to a radius of curvature of 0.5 mm.The bending cycles were repeated 10 times, and the contact angle was measured after each 10 cycles.The results showed that the contact angle decreased gradually with increasing bending cycles.The mesh maintained its superhydrophobicity (contact angle of 150°) for 50 bending cycles, but the contact angle decreased to 134°after 100 bending cycles (Figure 10B').Coated mesh was subjected to experiments to evaluate its hydrophobicity in pure water and resistance to acidic and alkaline conditions.The coated mesh was immersed in beakers containing water samples with different pH for 5 minutes each.Then, the specimens were dried naturally without washing and the contact angle was measured.As shown in Figure 10C, it was observed that the contact angle decreased significantly to about 120°when immersed in strong acid.It was also found to decrease when exposed to strong alkaline solutions, but to maintain 150°.These observations indicate that the coated mesh has stability against acidity.To investigate the effect of temperature, the mesh was placed on a hot plate for 5 minutes at various temperature intervals.It was observed that the contact angle gradually decreased without significant change from 50°C to 200°C, but maintained a contact angle of more than 160°.However, the contact angle began to decrease significantly from 250°C, and it was observed to decrease to 120°at 300°C (Figure 10D).
The oil-water separation capabilities of the fabricated superhydrophilic and superhydrophobic copper meshes were assessed in the experimental setup.For the oil-water separation experiment, I conducted trials using commonly used edible oils, not emulsified oils typically found in household wastewater.Each individually fabricated copper mesh was affixed to the base of a beaker, positioned above another vessel.The experimental procedure was conducted under atmospheric pressure, whereby water or oil was individually introduced into each beaker.In the case of the superhydrophilic copper mesh-equipped beaker, water permeated through the mesh, gradually filling the lower vessel (Figure 11A).However, the oil, unable to penetrate the wetted superhydrophilic copper mesh, remained confined at the top of the beaker (Figure 11A').Subsequent introduction of water, while the oil remained in place, demonstrated the capability of water to effectively pass through the copper mesh.The permeation rate of water achieved a minimum of 96%.
In contrast, the beaker equipped with the superhydrophobic copper mesh displayed different behavior.Water was retained in the upper section of the beaker, while the oil effectively permeated through the mesh, filling the lower vessel (Figure 11B, B').Within a span of 2 minutes, all the oil had entirely seeped through, leaving only water in the upper beaker.The observed flow rate of oil was determined to be 0.833 cm 3 s −1 , while the permeation rate reached at least 95%.
These findings distinctly underscore the potential functionality of both superhydrophilic and superhydrophobic copper meshes as viable filtration systems for segregating oil and water.It is noteworthy to emphasize the indispensability of a wetted mesh for conducting the superhydrophobic experiment (Figure 11).The properties of the superhydrophobic copper mesh were studied by applying various solutions to its surface.In addition to water, liquids such as cider, milk, juice, and coffee were observed to maintain their hydrophobicity on the mesh.Water droplets were also applied to a crumpled mesh to study its macro-level mechanical properties.The crumpled mesh surface retained its hydrophobicity.The self-cleaning effect of superhydrophobicity was demonstrated by applying foreign substances to the mesh and observing their removal as water droplets rolled off the surface (Figure 12B).Despite its net-like structure, suggesting high permeability and breathability, the superhydrophobicity of the copper mesh implies water impermeability.A breathability test was conducted using acetic acid and litmus paper (Figure 12C).Acetic acid vapors passed through the superhydrophobic copper mesh and reacted with the litmus paper, causing a color change from blue to red (Figure 12C').This outcome demonstrates that the fabricated superhydrophobic copper mesh maintains hydrophobic, mechanical, and breathable characteristics (Figure 12C).

Conclusion
In this study, we proposed an electrodeposition and solution process for creating hierarchical microstructures to achieve superhydrophilic and superhydrophobic surfaces.We successfully fabricated a superhydrophilic surface with a contact angle of 0°and transitioned it into a superhydrophobic surface with a contact angle of ≈172°by coating it with a prepared Teflon solution.During the electrodeposition process, we discovered that increasing the current intensity led to faster deposition rates and the formation of finer copper particles, resulting in delicate copper structures.The solution oxidation process involved oxidizing copper particles to form Cu(OH) 2 nanorods, and we found that higher ammonium persulfate concentrations led to faster reaction rates and longer nanorods.To create a porous structure with reduced surface area, we manipulated the concentration of ammonium persulfate.
Finally, we formed SiO 2 particles on Cu(OH) 2 nanorods, and higher NH 4 OH concentrations accelerated the reaction rate, resulting in larger SiO 2 particles.After each process, we observed that the surface roughness increased, leading to an increase in the water contact angle on the mesh surface.This indicates that surface wettability can be controlled through induced surface roughness by the formed nanostructures, as confirmed by EDS and XRD analyses of the chemical composition.
The performance of the produced superhydrophilic and superhydrophobic meshes was validated through durability and stability tests under varying pH, temperature, abrasion, and bending fatigue conditions.Chemical resistance tests revealed a decrease in contact angle at pH 2, but contact angles above 150°were maintained at other pH levels.Thermal resistance Figure 12.Fabricated superhydrophobic copper mesh characterization experiments: A) superhydrophobic copper mesh with various solutions applied, (A') crumpled superhydrophobic copper mesh, B) self-cleaning effect demonstrated using superhydrophobicity, C) breathability test of superhydrophobic copper mesh using acetic acid, and (C') litmus paper before and after the breathability test.tests showed that superhydrophobicity was maintained below 250°C.Furthermore, abrasion resistance and bending fatigue tests demonstrated the mechanical durability and stability of the meshes.Self-cleaning ability, breathability, and an oil/water separation efficiency exceeding 96% were also confirmed.This study emphasizes the promising role of superhydrophilic and superhydrophobic copper meshes in water separation, highlighting their potential applications in materials science for improved mechanical and chemical stability, self-cleaning properties, and the fabrication of micro/nanostructures.In the biological field, superhydrophobicity can find applications in biocompatible materials.Additionally, optimizing surface nanostructures in the energy storage field can enhance efficiency.The improved performance of surface characteristics holds potential for diverse industrial applications, promoting the development of new technologies.
Characterization: The electrochemical deposition was conducted using an AC/DC power supply (Model 6621; 50 MHz arbitrary waveform/function generator; Keithley, USA) and Platinum wire counter electrode(ALS, Japan).Copper(II) hydroxide nanorods growth was conducted using a digital shaker(SHO-10, LK LABKOREA, Korea) for 15 rpm.The morphology of the nanostructured, coated surface was observed using a field emission scanning electron microscope (FE-SEM; Ultra Plus; ZEISS, Germany) and characterized by energy dispersive spectroscopy (EDS) (FlatQuard; Bruker, USA).An X-ray diffractometer(XRD) (Smartrap, Rigaku, Japan) was used to analyze the type and arrangement of atoms in the material, as well as diffraction patterns.The contact angle of the surface was assessed by dispensing 5 μL onto the copper mesh surface with a SmartDrop Plus (Femtobiomed, Korea).The area fraction was determined in ImageJ (NIH, USA) using photographs captured by the SEM.
Fabrication of The Rough Superhydrophobic Surface: Electrochemical Deposition of Copper Nanoparticles: Before and after electrochemical deposition, the copper mesh was cleaned with deionized water.In a 0.1 M CuSO 4 solution, a constant current was applied for 4 minutes at a distance of 25 mm between the copper mesh and the platinum counter electrode.
Copper ions in the CuSO 4 solution formed copper nanoparticles on the copper mesh surface through a Faradaic reaction, as shown in the following reaction equation: Copper(II) Hydroxide Nanorods Growth: The copper mesh, on which copper nanoparticles were deposited, was immersed in a solution of 1.25 M NaOH and varying concentrations of ammonium persulfate, and then placed on a digital shaker and stirred at 15 rpm for 30 minutes.Afterward, it was washed with deionized water and dried.The copper nanoparticles deposited by ammonium persulfate was oxidized and reacted with the hydroxide in the mixed solution containing copper ions to form Cu(OH) 2 nanorods.A solution of AFs, diluted with fluorocarbon oil at a ratio of 1:59, was dropped onto the copper mesh with a highly coarse nanostructure.It was then dried in an oven at 80°C for 30 minutes to form a superhydrophobic surface (Figure 13).

Cu
The resulting mesh demonstrated self-cleaning capabilities, maintained breathability, and achieved oil-water separation efficiency of over 96%.This study highlights the promising roles of superhydrophilic and superhydrophobic copper meshes in oil-water separation.Moreover, the developed surface-wetting fabrication process holds potential applications in crucial industrial sectors such as materials science, biomedical engineering, and energy storage.
Figure 2A-D presents SEM images

Figure 1 .
Figure 1.A) Schematic illustration of the three-step process for superhydrophobic surface fabrication, and B) SEM images of electrochemical copper nanostructures deposition, Copper (II) hydroxide(Cu(OH) 2 ) nanorods formed via the solution process, Silica(SiO 2 ) particles formed via the solution process.WCA measurement images of C) superhydrophilic copper mesh and (D) superhydrophobic copper mesh.

Figure 2 .
Figure 2. SEM images of copper particles on copper mesh for the different electrodeposition current A) 25 mA, B) 50 mA, C) 75 mA, and D) 100 mA.

Figure 3 .
Figure 3. A) Contact angle, B) Sliding angle, and C) Copper particles size of the different electrodeposition current for 25, 50, 75, 100 mA.And D) Contact angle of electrodeposition time for 100 mA.

Figure 5 .
Figure 5. A) Contact angle, B) Sliding angle and C) Cu(OH) 2 rods size of the different ammonium persulfate concentrations for 0.01, 0.03, 0.05, 0.07 M.And D) Contact angle of Oxidation time for 0.05 M.

Figure 6 .
Figure 6.SEM image of silica nanoparticles for the different ammonium hydroxide concentration A) 0.34 M, B) 0.51 M, C) 0.68 M, D) 0.85 M.

Figure 7 .
Figure 7. A) Contact angle, B) Sliding angle and C) SiO 2 particles size of the different ammonium hydroxide concentrations for 0.34, 0.51, 0.68, 0.85 M.And D) Contact angle of coating time for 0.51 M.

Figure 8 .
Figure 8. Area fraction analysis for each process: A) bare mesh, B) electrodeposited mesh, C) oxidated mesh, and D) coated mesh.

Figure 9 .
Figure 9. A) EDS spectrum of each process and XRD pattern of B) electrodeposition process, C) chemical oxidation process, D) coating process.

Figure 11 .
Figure 11.Fabricated superhydrophobic copper mesh oil-water permeation experiment.A, A') Oil-water permeation experiment of a superhydrophilic copper mesh.B, B') Oil-water permeation experiment of a superhydrophobic copper mesh.