Superhydrophobic Copper Surface Research Articles

Effect of Surface Wettability on Nanoparticle Deposition during Pool Boiling on Laser-Textured Copper Surfaces

Prior studies have evidenced the potential for enhancing boiling heat transfer through modifications of surface or fluid properties. The deployment of nanofluids in pool boiling systems is challenging due to the deposition of nanoparticles on structured surfaces, which may result in performance deterioration. This study addresses the use of TiO2–water nanofluids (mass concentrations of 0.001 wt.% and 0.1 wt.%) in pool boiling heat transfer and concurrent mitigation of nanoparticle deposition on superhydrophobic laser-textured copper surfaces. Samples, modified through nanosecond laser texturing, were subjected to boiling in an as-prepared superhydrophilic (SHPI) state and in a superhydrophobic state (SHPO) following hydrophobization with a self-assembled monolayer of fluorinated silane. The boiling performance assessment involved five consecutive boiling curve runs under saturated conditions at atmospheric pressure. Results on superhydrophilic surfaces reveal that the use of nanofluids always led to a deterioration of the heat transfer coefficient (up to 90%) compared to pure water due to high nanoparticle deposition. The latter was largely mitigated on superhydrophobic surfaces, yet their performance was still inferior to that of the same surface in water. On the other hand, CHF values of 1209 kW m−2 and 1462 kW m−2 were recorded at 0.1 wt.% concentration on both superhydrophobic and superhydrophilic surfaces, respectively, representing a slight enhancement of 16% and 27% compared to the results obtained on their counterparts investigated in water.

Study of the Antibacterial Activity of Superhydrophilic and Superhydrophobic Copper Substrates against Multi-Drug-Resistant Hospital-Acquired Pseudomonas aeruginosa Isolates.

The global spread of multidrug-resistant (MDR) hospital-acquired pathogens is a serious problem for healthcare units. The challenge of the spreading of nosocomial infections, also known as hospital-acquired pathogens, including Pseudomonas aeruginosa, must be addressed not only by developing effective drugs, but also by improving preventive measures in hospitals, such as passive bactericidal coatings deposited onto the touch surfaces. In this paper, we studied the antibacterial activity of superhydrophilic and superhydrophobic copper surfaces against the P. aeruginosa strain PA103 and its four different polyresistant clinical isolates with MDR. To fabricate superhydrophilic and superhydrophobic coatings, we subjected the copper surfaces to laser processing with further chemosorption of fluorooxysilane to get a superhydrophobic substrate. The antibacterial activity of superhydrophilic and superhydrophobic copper surfaces was shown, with respect to both the collection strain PA103 and polyresistant clinical isolates of P. aeruginosa, and the evolution of the decontamination of a bacterial suspension is presented and discussed. The presented results indicate the promising potential of the exploitation of superhydrophilic coatings in the manufacture of contact surfaces for healthcare units, where the risk of infection spread and contamination by hospital-acquired pathogens is extremely high.

Trisodium citrate as a potential and eco-friendly corrosion inhibitor of copper in potable water

In this work, the mixture of trisodium cittrate and Zn2+ was used as binary (hetero type) inhibitor for corrosion inhibition of copper metal in potable water. The binary inhibitor system (Zn2+ and trisodium citrate) was used to form hydrophobic surfaces on copper submerged in potable water. Water contact angle (WCA) was found to be 155°4° when the inhibitor was present, whereas it was 84°2° when there was no inhibitor. These observations suggested the development of superhydrophobic layer on the surface of copper in drinkable water. Electrochemical impedance spectroscopy (EIS – AC mode), and potentiodynamic polarization (DC mode) experiments conveyed that the copper surface could be protected by utilizing the mixture of trisodium citrate and Zn2+ in potable water. The morphological studies including SEM (coupled with EDX), AFM, and WCA were evidenced the formulation of a hetero-type inhibitor for the corrosion inhibition of copper in potable water. In this study, the decline in the double-layer capacitance and the rise in the charge transfer resistance were due to the adsorption of inhibitor confirming the development of protective layer, which EIS, SEM, EDX, AFM, and WCA studies also supported. Thus, there was a synergism observed between TSC and Zn2+, and the formulation consisting of TSC and Zn2+ provided 83% of inhibition efficiency (IEp). So, it was suggested that the approach reported in this study could be a simple method for obtaining the superhydrophobic copper surface.

In-depth analysis of corrosion-resistance and dynamic stability of superhydrophobic copper developed by a green approach

This study gives a systematic analysis of corrosion resistant behaviour of superhydrophobic copper fabricated by two-step (electrodeposition followed by coating) and one-step (coating without electrodeposition) processes using behenic acid. Wetting and corrosion characteristics of coated copper have been continuously evaluated by abrasion with sand paper, immersion in acidic and alkaline solutions, and heating at elevated temperature. Although, wetting properties of coating have been obviously decreased with continuous abrasion, contact with acidic and alkaline ambiance, and hot temperature exposure, but corrosion properties of coated copper have not shown the similar trends which has been discussed through polarisation tests and EIS study in detail. Additionally aforesaid both processes generate durable superhydrophobic copper surface with excellent corrosion-resistant and anti-wetting characteristics; however, a two-step process is proved more efficient than the one-step process and promises to produce anti-wetting coatings for real-world applications.

Anticorrosion Properties of Superhydrophobic Copper Surface Coatings Obtained by Electrodeposition

Anticorrosion Properties of Superhydrophobic Copper Surface Coatings Obtained by Electrodeposition

Efficient defrosting on hybrid surfaces with heterogeneous wettability

Frosting behavior and dynamic defrosting characteristics of horizontally oriented hybrid surfaces with heterogeneous wettability were experimentally investigated. The developed hybrid surfaces with superhydrophobic patterns built on superhydrophilic background integrated the properties of frost retardation under frosting conditions and fast surface cleaning of residual water upon defrosting. Four types of hybrid surfaces with different pattern spacings were tested in this work. Hybrid surfaces exhibited superior anti-frosting performance compared with that of a bare copper surface but lower than a complete superhydrophobic surface. During defrosting process, surface energy gradient and Laplace pressure gradient enabled by heterogeneous wettability on hybrid surfaces could drive the mobile slush composites on superhydrophobic regions move to superhydrophilic areas to achieve quick cleaning even in the absence of gravity force. The proportion of surface clean time of one full cycle duration on hybrid surfaces was as low as 32.2%–41.5%. Compared to complete superhydrophobic and bare copper surfaces, hybrid surfaces exhibited a significant enhancement on defrost efficiency due to larger three phase contact line length on evaporation-mediated surface cleaning performance, especially the SSH-3 surface, achieving the largest defrost efficiency within the present frost mass range.

Experimental study of frosting cleaning process on superhydrophobic copper surface

Frosting cleaning process for dust removal is a simple and direct way to keep heat exchangers clean, and the dust removal effectiveness is strongly influenced by surface property. An object of this paper is to investigate the frosting cleaning process on super-hydrophobic surface and to determine the interaction between the frost layer and dust particles. Frosting-defrosting process on four kinds of test samples were studied by experiments. The results showed that, compared with the clean surfaces, the frost layer structure was denser and more uniform on dusty surfaces. On the super-hydrophobic surface, as a kind of heterogeneous nucleation point, the dust particle promoted frost layer growth by 57%. During the defrosting process on dusty test samples, the melted water and dust particles were reverse osmosed the frost layer. The reverse osmosed rate increased with frosting time, and it was over 0.5 under all experimental conditions. Compared with the bare surface, super-hydrophobic surface displayed a different defrosting behavior and had a shorter defrosting time. On the super-hydrophobic surface, deposited dust particles were encased in the frost-water mixture block and flaked off the surface under gravity, and the dust removal rate was up to 94.5% in this work. Because of the reverse osmosed dust movement, the wrap effect, and the weak adhesion of super-hydrophobic surface, the dust-frost mixture is easily removed. Thus, utilizing the frosting-defrosting characteristics of super-hydrophobic surface for promoting the dust removal has a good application prospect.

Fabrication of robust superhydrophobic copper surface via highly efficient nanosecond laser-based surface functionalization

Creation of superhydrophobic surface via laser-based surface texturing has received considerable attention during the past decades. However, processing efficiency of the fabrication technique and robustness of the fabricated surface have been the major barriers that limit their wider applications. In this work, a laser-based surface functionalization technique was developed for fabrication of robust superhydrophobic surface with a highly efficient processing manner. Laser surface texturing was firstly employed to generate hierarchical surface structures, and silicone oil dripping and heat treatment were further utilized to modify the surface chemistry which ensures the realization of superhydrophobicity. The laser-based functionalized superhydrophobic surface also exhibits remarkable stability and durability subject to long-time storage in air and tape peeling test. More importantly, the developed technique only requires a total post-process treatment duration of ∼5–10 min, which takes significantly less time than the conventional chemical modification methods such as prolonged aging in air, deposition of chemical coating and low-temperature annealing. The high processing efficiency and surface robustness of the laser-based surface functionalization technique could potentially enable more practical applications in diverse areas.

Mechanically robust superhydrophobic copper surface with self-cleaning, anti-icing, and corrosion resistance

This paper uses a new method combining nanosecond laser processing technology and sol-gel to design and manufacture mechanically robust micro-nano structure and modified SiO2@PDMS coating on copper substrate. The superhydrophobic composite surface was successfully synthesized with a water contact angle of 159.5° and a sliding angle of 0.5°. The characterization of the prepared superhydrophobic surface #3 (laser-textured@SiO2@PDMS protective layer) was studied by optical profilometry, scanning electron microscopy, FT-IR spectroscopy, and X-ray photoelectron spectroscopy. The composite structure of micron/nano and organic/inorganic 3D interwoven network can be observed to improve the hydrophobic, wear-resistant, and compressive properties of the substrate surface. FT-IR spectra fully indicate the presence of PDMS and Si (CH3) grafted onto SiO2 particles on the copper surface, and the presence of SiO and SiC detected by XPS fully proves the FT-IR results. In addition, self-cleaning, wear resistance, anti-icing, corrosion resistance, and NaCl deliquescence behavior were evaluated. The results show that surface #3 can efficiently remove contaminants within 200 s. In the anti-icing experiment, the delayed icing time and ice adhesion strength of surface #3 are 3.33 times and 1.99 % of that of the ordinary copper surface, respectively, which can make the icicle slide easily. In the electrochemical test, the corrosion current density decreased by an order of magnitude, and the corrosion inhibition efficiency reached 90.57 %. Based on its excellent self-cleaning, mechanical robustness, anti-icing, and anti-corrosion properties, we believe that the composite modified surface of the laser-textured@SiO2@PDMS protective layer designed and manufactured in this study is expected to be used in engineering fields such as refrigeration heat exchangers.

Superhydrophobic Electrodeposited Copper Surface for Robust Condensation Heat Transfer.

Superhydrophobic surfaces have great potential for various applications owing to their superior dewetting and mobility of water droplets. However, the physical robustness of nano/microscale rough surface structures supporting superhydrophobicity is critical in real applications. In this study, to create a superhydrophobic surface on copper, we employed copper electrodeposition to create a nano/microscale rough surface structure as an alternative to the nanoneedle CuO structure. The rough electrodeposited copper surface with a thin Teflon coating shows superhydrophobicity. The enhancement of dewetting and mobility of water droplets on copper surfaces by electrodeposition and hydrophobization significantly improved the condensation heat transfer by up to approximately 78% compared to that of copper substrates. Moreover, the nano/microscale rough surface structure of the electrodeposited copper surface exhibits better tolerance to physical rubbing, which destroys the nanoneedle-structured CuO surface. Therefore, the condensation heat transfer of the superhydrophobic electrodeposited copper surface decreased by only less than 10%, while that of the nanoneedle-structured CuO surface decreased by approximately 40%. This suggests that an electrodeposited copper surface can lead to the stable performance of superhydrophobicity for real applications.

Nanosecond laser fabrication of superhydrophobic copper and anti-frost surface on copper

The frost phenomenon on metal surfaces seriously reduces the system operation efficiency, and the research of robust and effective waterproof protective layer on metal surfaces has become a focus of attention. The ability of superhydrophobic surfaces to stay dry is attractive for frost suppression performance on metal surfaces. However, when subjected to external pressure, the waterproof protective layer is highly susceptible to damage, resulting in the loss of superhydrophobicity. Therefore, a copper surface possessing superhydrophobicity and mechanical robustness was designed and fabricated in this study. The design of robust micro-nano structures on copper surfaces using finite element analysis. The combined modification of the copper surface using nanosecond laser and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES). Or refilled nano-silica to form the combined surface. The contact angle of the combined surface was 160.3°, and the rolling angle was 1°, both of which helped to obtain superhydrophobicity. The mechanical robustness of the superhydrophobic copper surface was tested by knife, stainless steel wire ball, and tape. The freezing and anti-freezing properties of the droplet on the superhydrophobic copper surface and ordinary copper surface were observed by experiments. The results show that the surface of superhydrophobic copper still keeps superhydrophobicity after repeated mechanical durability tests. When the frost thickness is 0.9 mm (cooling temperature of −7 °C, horizontal placement), the superhydrophobic copper surface (composite surface) has excellent frost suppression performance compared to the ordinary copper surface, and the growth of frost could be delayed by 1.75 times. Meanwhile, the hydrophobicity of the superhydrophobic copper surface remained essentially unchanged after 50 freeze-thaw cycle experiments (a single cooling time of 30 min). We believe that the practical aspects of anti-frost design strategies on the copper surface show a great advantage.

An Anti-Corrosion Superhydrophobic Copper Surface Fabricated by Milling and Chemical Deposition

The development of anticorrosion coatings on copper has raised tremendous interest in material science. Using a milling method, regular rough structures were fabricated, and after chemical deposition with AgNO3 solution and the modification of stearic acid, a superhydrophobic copper substrate could be obtained. The surface morphological study showed a dendritic microstructure, and a rectangular surface bulge produced by milling was distributed on the copper substrate. The coatings showed the surface water contact angle could be as high as 158.4°. The best anti-corrosion coating was the sample milled with the cutter tip distance of 0.30 mm. The as-prepared superhydrophobic sample has a good self-cleaning effect. Scratched with a knife and abraded by friction, the copper substrate still maintained good superhydrophobic nature. The coating was mechanically stable and possessed good corrosion resistance.

Study on Preparation of Superhydrophobic Copper Surface by Milling and Its Protective Performance.

Using milling method, a 0.1 mm flat-bottom sharp knife was used to mill the surface of Cu substrate in a CNC engraving machine to construct the microstructure of rectangular bumps, and rectangular bumps with different sizes and different distances were prepared by changing the distance between cutter tips. After deburring and stearic acid modification, a superhydrophobic Cu surface with excellent mechanical durability and stability was successfully prepared. Through friction and wear experiments, the contact angle of the superhydrophobic Cu surface decreased slightly while retaining excellent corrosion resistance.

Temperature-dependent dynamic fouling on superhydrophobic and slippery nonwetting copper surfaces

• Presents, for the first time, temperature-dependent dynamic fouling on nonwetting surfaces. • Elucidates, for the first time, effects of texturing method and surface type on fouling behavior. • Nonwetting surfaces show up to 75% less scaling compared to regular surfaces. • Electrodeposited surfaces offer better scaling resistance compared to etched surfaces. • Presents Hill-Langmuir model, for the first time, to describe the time evolution of scaling. Bioinspired, superhydrophobic and slippery liquid infused surfaces that offer nonwetting characteristics have been explored in recent years for fouling mitigation. However, most of the studies are in the context of biofouling or under static immersion at ambient temperature conditions that are not reflective of the dynamic flow environment in practice. This article presents, for the first time, a systematic study of dynamic fouling of superhydrophobic (SHS) and slippery lubricant-infused surfaces (LIS) over a range of flow and temperature conditions. Copper metallic surfaces were textured via electrodeposition or etching and further functionalized to achieve SHS and, additionally, infiltrated with a lubricant to fabricate LIS. The nonwetting surfaces were studied for their fouling behavior in a rotating Couette flow of a supersaturated calcium sulfate solution at different rotational speed and temperature. Fouling mineral mass accumulation on the different surfaces was measured as a function of time over a period of days using inductively coupled plasma mass spectroscopy and the fouled surfaces were investigated using scanning electron microscopy. Both SHS and LIS showed superior anti-scaling performance at all ranges of variables. An analytical Hill-Langmuir model is presented, for the first time, to describe the time evolution of scaling within 20% accuracy over the range of parameters studied. The study is the first to juxtapose two surface texturing methods, electrodeposition and etching, and two nonwetting surface types, SHS and LIS, subject to a common suite of experiments to elucidate fundamental understanding of mineral fouling on nonwetting surfaces.

Experimental investigation of frosting behavior on superhydrophobic copper surface prepared by thermal evaporation Method

An experimental study is proposed to analyze the frosting behavior of ice on a superhydrophobic surface. Ice accumulation can result in performance problems and safety concerns for transmission lines, marine and offshore structures, refrigeration, cryogenics, wind turbines, and heat-exchangers. Wetting properties are important for ice formation on surfaces from the liquid phase, where the water repellency of the surfaces could enhance their anti-icing effect. Such surfaces will be prepared by using a nanotextured coating. A thermal evaporation system will be proposed for nanocoating on a copper surface. The prepared surface produces a contact angle of 162° ± 2°. The Low Bond Asymmetric Drop Shape analysis is used to measure the contact angle using imageJ software. The heat-transfer performance of an evaporator is affected by frost formation. In this work, the heat-transfer coefficient of the surface will be estimated in the defrosting process. The effect of hydrophobicity and superhydrophobicity of surfaces, surface chemistry, morphology, and roughness scale will be studied on the defrosting process. In particular, wetting characteristics of the superhydrophobic surfaces revealed defrosting performance. The experiments will be performed in controlled environmental conditions. The anti-icing properties of superhydrophobic surfaces with different topography but similar chemistry are studied.

Stable superhydrophobic and conductive surface: Fabrication of interstitial coral-like copper nanostructure by self-assembly and spray deposition

Water permeation is an important issue in both fundamental research and industrial applications. In this work, stable superhydrophobic copper surfaces were obtained by self-assembly and spray deposition on cotton fabrics. Scanning electron microscopy revealed that micro/nano dual-scale coral-like structures were established by the stacking of copper nanoparticles, thus forming a stable Cassie model for superhydrophobic feathers. The water contact angle of the surface was 161°, while the slide angle was as low as 3°. Chemical bonds were formed between substructures and copper nanoparticles by molecular grafting, which improved its mechanical stability, since the surface was verified to maintain a large contact angle after long-distance abrasion and folding. Compared with the superhydrophilic copper surface, the superhydrophobic coating showed better corrosion resistance in 3.5 wt% NaCl solution and artificial sweat. Combined with the inherent conductivity of copper, fabrics have potential applications in the new generation of advanced textiles.

Mechanically Robust Superhydrophobic Copper Surface with Self-Cleaning, Anti-Icing, and Corrosion Resistance

Mechanically Robust Superhydrophobic Copper Surface with Self-Cleaning, Anti-Icing, and Corrosion Resistance

Per-fluorinated chemical free robust superhydrophobic copper surface using a scalable technique

Robust superhydrophobicity is of immense practical interest in a wide range of applications including self-cleaning, anti-icing, anti-corrosion, atmospheric water harvesting, desalination, condensation, and oil-water separation. However, biohazard associated with the prevalent use of per-fluorinated synthetic chemicals in making these surfaces and the gradual loss of superhydrophobicity have been major roadblocks. Here we develop an environment-friendly and industrially scalable superhydrophobic copper surface using a combination of electrochemical deposition and Lauric acid functionalization. We optimized the synthesis process for ensuring the robustness of these superhydrophobic surfaces. The surface exhibits contact angles as high as 158° with excellent droplet rebounding, self-cleaning, anti-icing, and dropwise condensation abilities. Thermal stability in the range of −15°C to 150°C, mechanical robustness against abrasion, chemical stability under aqueous, acidic, and basic medium, and the excellent plastron layer stability under long-time underwater immersion attest to the high quality of superhydrophobic surfaces for large-scale applications. These coatings when implemented on the curved surface of a copper tube demonstrated appreciable improvement in condensation behavior. Our method provides a sustainable approach for suitable technological interventions in energy and potable water applications requiring robust environment-friendly superhydrophobic surfaces.

Onset of Boiling, Heat Transfer, and Flow Patterns of Flow Boiling on the Superhydrophobic Porous Copper Surface in a Microchannel

Abstract To explore the effect of microstructured porous surface on enhancing the heat transfer of flow boiling in a microchannel, the microporous copper surface was fabricated with microscale pores in ranges of 1–5 μm, which presented super-hydrophobicity. Subcooled flow boiling experiments were carried out to study the hydraulic and thermal transport performance in a single narrow rectangular microchannel. High-speed flow visualizations were conducted coupled with instrumental measurements to illustrate the effects of heat flux and mass flux on heat transfer performance and flow patterns for originally hydrophilic bare copper surface and superhydrophobic microporous structured surface. The onset of boiling (ONB) characteristics of both test surfaces was compared with predictive correlations with a good agreement and verified by the captured flow pattern images. Benefit from the superhydrophobic wettability provided by its microscale porous structures and a large number of potential nucleation sites, the required wall superheats, and imposed heat fluxes of onset of boiling both decreased for the modified surface. The flow patterns on the two surfaces varied, which resulted in the different trends of heat transfer coefficient (HTC) with mass fluxes and heat fluxes. Because of the strengthened bubble departure process, the enhancement of the porous surface compared to the original bare surface gradually increased with mass fluxes. The average two-phase heat transfer coefficients of the superhydrophobic porous copper surface were enhanced for up to 74.84%, due to the earlier onset of boiling, higher frequency of bubble nucleation, and strengthened boiling intensity.

Ultrasonic vibration assisted laser (UVAL) treatment of copper for superhydrophobicity

In this paper, a hybrid ultrasonic vibration assisted laser (UVAL) prepared copper surface of super-hydrophobic was reported. After UVAL treatment, the water contact angle (WCA) of copper surface to 3 μL water was 157.4°and the water slip angle (WSA) was less than 10°. The wettability, microstructure, chemical composition and durability of copper surface were measured by contact angle measuring instrument, field emission scanning electron microscopy (FESEM), surface predatory X-ray diffraction (XRD) and three-dimensional morphology. The results revealed that after UVAL treatment, the microcoral-like structure and nano-grass structure were formed on the surface of the sample, which were similar to the surface of lotus leaf. Ultrasonic vibration combined with laser treatment can accelerate the adsorption of airborne hydrocarbon contaminations on the surface of micro and nanostructures, and reduce the surface energy of copper particles on the surface. This study provides a fast, convenient and effective method for the rapid preparation of stable superhydrophobic copper surface.