Self-cleaning Behavior Research Articles

Development of self-cleaning cement mortar exposed to indoor and outdoor environment

The presence of volatile organic compounds and other gaseous contaminants in both the indoor and outdoor environments causes the building's aesthetics and human health to deteriorate. It is vital to clean the indoor and outdoor environments to address this difficult problem. The development of self-cleaning concrete will provide a remedy for this issue. Self-cleaning characteristics can be incorporated in to cement with the addition of photocatalytic substances, such as Titanium Dioxide (TiO2). This enables the preservation of building surfaces and the decrease of air pollution in the environment. In the present study, TiO2 in cement mortar containing barites powder is utilized to evaluate the self-cleaning behavior and setting time of cement mortar. The self-cleaning experiment was conducted in two ways: coating mortar samples with dye and dipping mortar samples in Methylene Blue dye. The samples of mortar are then subjected to sunlight and LED light. The efficacy of self-cleaning was measured by measuring the concentration of Methylene Blue and observing it physically. In all situations, the self-cleaning ability of mortar samples was greater when exposed to sunlight than LED light. Moreover, coated samples were more efficient than immersion samples. Higher TiO2 dosage has demonstrated enhanced performance.

Biochar based self cleaning superhydrophobic surface with aqueous DESphobic properties

In this work, facile fabrication of chemically stable superhydrophobic surfaces based on biocompatible, fluorine free, carbon rich biochar has been reported. Biochar synthesized from dried rice straw by pyrolysis at 550˚C, which was characterized using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). The biochar coated surface demonstrated superhydrophobic behaviour with static water CA > 150°. Aqueous drops remain in superhydrophobic state due to stability of Cassie-Baxter wetting regime and can shows very high-water contact angle (WCA > 160°) and self-cleaning behaviour. Such a very high WCA have been achieved typically by combination of low energy chemicals (fluorine based) and surface textures. However, no harsh chemical treatment of biochar was performed and a simple methodology of creating biochar layer onto the substate was adopted. Such surface also demonstrated repellent properties against aqueous mixtures of deep eutectic solvent (DES). A spherical aqueous DES drop can be easily formed onto the biochar surface for image analysis. The density of the liquid sample with a small sample volume can be assessed using this drop shape that was measured on the superhydrophobic biochar surface.

Mechanical, chemical and wetting properties of a superhydrophobic surface based on functionalized ZrO2 on stainless steel

A stable superhydrophobic FAS-ZrO2 (FZr-ESS) surface was created by chemically etching and modifying a 304 stainless steel substrate. The effect of etching parameters such as time and temperature on the surface wetting properties was studied and optimized. The etched steel surface exhibited a honeycomb-like microstructure that, coupled with the low surface energy of the fluorinated ZrO2 nanoparticles, produced a FZr-ESS surface with a surface contact angle (CA) of 165.9° and a sliding angle (SA) of 1.7°. The presence of highly stable functionalized ZrO2 conjugated to the steel matrix contributed to the surface's outstanding mechanical stability, as confirmed by tape peeling and sandpaper abrasion tests. Furthermore, the FZr-ESS surface demonstrated exceptional chemical stability under a variety of pH conditions due to its excellent water repellency. An electrochemical test showed that the resulting surface was highly resistant to corrosion, with the corrosion current density reduced by nearly two orders of magnitude compared to bare stainless steel. The superhydrophobic FZr-ESS surface also displayed excellent long-term stability, wetting diversity, and self-cleaning behavior, making it highly versatile for a range of applications.

Waterborne superhydrophobic coating with abrasion and corrosion resistant capabilities

Superhydrophobic materials have been extensively exploited for corrosion protection because of their unique non-wetting properties, but restricted by the complicated fabrication process, fluorinated chemicals usage, weak interfacial binding force, low hardness, and poor abrasion/scratch resistance. In this paper, we designed a waterborne superhydrophobic coating based on modified Al2O3 nanoparticles (M-Al2O3) and waterborne epoxy resin through a versatile spray-coating approach. When the mass ratio of epoxy/M-Al2O3 was 1.5, the coating features both superhydrophobic properties (water contact angle ∼ 150.8 ± 0.6° and sliding angle ∼ 4.9 ± 0.2°) and optimal abrasion-resistant stability. The coating can maintain its water-repellent superhydrophobicity after 90 abrasion cycles and 120 tape-peeling cycles, indicating reinforced interfacial robustness. Moreover, the coating exhibits excellent self-cleaning, anti-fouling, and corrosion-resistant behaviors with greatly enhanced charge transfer resistance (Rct) and lowest frequency impedance values (|Z|0.01Hz). The corrosion inhibition efficiency of the original coating, coating after 90 abrasion cycles and coating after 120 tape-peeling cycles were 99.99 %, 97.54 %, and 97.52 % respectively, confirming a durable anti-corrosion stability. In addition, the coating retains its superhydrophobic properties after a 6 H pencil hardness test and knife scratch test, which demonstrates its robustness and stability against mechanical damage.

Simple Method for Creating Hydrophobic Ultraflexible Photovoltaics.

Optoelectronic devices, such as photodetectors and photovoltaics, are susceptible to surface contamination or water damage that can lead to reductions in performance or stability. Applying superhydrophobic coatings to these devices can introduce self-cleaning behavior and water resistance to extend their lifetime and improve their efficiency. However, existing methods for inducing superhydrophobicity have not been compatible with ultraflexible devices because of their thickness and complexity requirements. In this work, we introduce a procedure for inducing superhydrophobic and self-cleaning behavior on ultraflexible components using a combination of shrinkage-induced wrinkles and a low-surface-energy coating. We apply these techniques to an ultraflexible organic photovoltaics and demonstrate excellent hydrophobicity and self-cleaning behavior.

Experimental investigation of self-cleaning behaviour of 3D-printed textile fabrics with various printing parameters

Self-cleaning of textile fabrics is defined as the ability that the pollutants particles can be removed from the fabric surface without any external source. The application of the technology is beneficial to the environment since it conserves water, energy and laundry costs. In the past, it is typically obtained by chemical coatings, which develop low surface energy and high roughness on the fabric surface, allowing the pollutant particles or droplets to float over the surface rather than adhesion. These chemical coating methods are effective for fabrics manufactured by traditional woven-based textile technology. However, the recent advancements in 3D printing technology have evolved the manufacturing of textile fabrics but with equal challenges in self-cleaning as previous chemical coating-based methods are not useful for printed fabrics. A recent study has successfully established a linear regression model to demonstrate the relationship between secondary 3D printing parameters and the self-cleaning properties of different polymeric fabrics. This paper is intended to analyse the impact of the primary printing parameters on the self-cleaning attributes, including infill rate (IR), flow rate (FR), printing temperature (PT), printing speed (PS), and printing acceleration (PA). The experimental results were used to construct a regression polynomial to quantify the self-cleaning behaviour of the selected thermoplastic polyurethane (TPU) fabric. The models were validated experimentally to highlight the critical values of considered primary parameters for optimal self-cleaning behaviour. The obtained results indicated that FR was the most significant parameter, and all parameters affected the fabric's wettability almost equally.

Effect of Superhydrophobic Surface on Corrosion Resistance of Magnesium-Neodymium Alloy in Artificial Hand Sweat

A superhydrophobic surface can endow metals with some intriguing characteristics such as self-cleaning behavior. In this study, a simple solution-immersion method based on the concept of predesigned corrosion is developed to enhance the corrosion resistance of a magnesium-neodymium alloy. The Mg alloy is directly soaked in potassium dihydrogen phosphate solution with the addition of ultrasound, and a layer of rough but dense coating is uniformly formed on the Mg-Nd alloy after the immersion process, which is mainly composed of MgHPO4∙3H2O. A superhydrophobic surface with an average wetting angle of 150.5° and a sliding angle of about 4.5° can be obtained on the Mg alloy by further chemical surface modification with perfluorodecyltriethoxysilane. This superhydrophobic surface has an interesting self-cleaning effect as well as good corrosion resistance in artificial hand sweat. In brief, this study provides a feasible way to prepare a superhydrophobic surface on the Mg-Nd alloy and reveals the effect of a superhydrophobic surface on the corrosion behavior of the Mg-Nd alloy, offering new technical insights into the corrosion protection of magnesium alloys.

Self-cleaning and corrosion-resistant superamphiphobic coating with super-repellency towards low-surface-tension liquids

In this paper, we designed and fabricated a liquid-repellent coating that features both superhydrophobicity and superoleophobicity, viz. Superamphiphobic properties, based on dual adhesive tape binding layer and 1H,1H,2H,2H-perfluorodecyltriethoxysilane modified aluminum oxide nanoparticles (Al2O3@PDFTES NPs). The constructed superamphiphobic coating presented non-wetting, high contact angles (CA), and low sliding angles (SA) towards various liquids with different surface tensions including water (CA = 167.6 ± 3.5°, SA = 2.9 ± 0.6°), glycerol (CA = 154.2 ± 2.7°, SA = 4.7 ± 0.4°), ethylene glycol (CA = 156.1 ± 2.4°, SA = 5.8 ± 0.2°), and peanut oil (CA = 155.2 ± 2.8°, SA = 6.5 ± 0.7°). The dynamic self-cleaning behaviors driven by water-, oil-, and hot water droplets verified the super-repellency, ultra-low surface energy, and interfacial adhesion force. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements showed >250 mV positive shifting of Ecorr, 4 orders of magnitude lower Icorr, 7 orders of magnitude higher Rct and |Z| modulus values, demonstrating a significantly improved corrosion resistance of the superamphiphobic coating. The synergistic effect of the Al2O3@PDFTES NPs with low surface energy and the adhesive tape layer with interfacial binding force contribute to the development of stably self-cleaning and anti-corrosion superamphiphobic coating, which will be a potential candidate for protective interfacial materials for marine and industrial applications.

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.

Experimental Investigation of Self-Cleaning Behavior of 3D-Printed Textile Materials with Different Printing Parameters

Experimental Investigation of Self-Cleaning Behavior of 3D-Printed Textile Materials with Different Printing Parameters

Recent advances in photocatalytic self-cleaning performances of TiO2-based building materials.

TiO2-based photocatalytic building materials can keep the building surface clean, and have decontamination, antibacterial effects and so on, which greatly reduces the maintenance cost and the risk of cleaning work, and these materials have great application potential in pollution and carbon reduction in the future. However, due to the wide band gap of TiO2, the low utilization of solar energy and the instability of super hydrophilicity have always been the difficulties in the field of photocatalysis. Based on the relevant research of TiO2-based photocatalytic materials in recent years, this review summarizes the modification strategies that can effectively improve the photocatalytic activity of TiO2-based photocatalytic materials. At the same time, the influence of complex environmental factors and substrate properties on the self-cleaning behavior of TiO2-based building materials was analyzed. This paper aims to provide effective guidance for the future application of TiO2-based photocatalysts in the construction field, improve people's understanding of photocatalytic building materials (PBM) and photocatalytic self-cleaning characteristics, and provide more possibilities for the extensive application of photocatalysis technology in the construction field, as well as to promote the realization of global carbon neutrality and other strategic goals of pollution and carbon reduction.

Zinc oxide nanoparticles as photo-catalytic and anti-bacterial pigment for alkyd resin based coating

Recently, there has been an upsurge among people around the world in maintaining a sustainable and hygienic environment. This is due to the over-exploitation of recourses causing environmental pollution and spreading bacterial infections. In this regard, scientists are motivated to develop smart coatings where environmental pollutants and bacterial cells are degraded when in contact with their surfaces.In our previous report, ZnO nanoparticles (NPs) were prepared using the precipitation technique, showing good photocatalytic and antibacterial activity [1]. In this context, the present study details the use of ZnO NPs as pigment for the fabrication of alkyd resin-based self-cleaning coating. The coating was developed by mixing ZnO NPs and alkyd resin along with the additives using the ball milling technique. The developed coating was characterized using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and water contact angle measurements.To elucidate the self-cleaning and hygienic behaviour of the ZnO/alkyd resin coating, the dried coating was exposed to crystal violet (CV) solution as a model dye pollutant and bacterial strains to assess its photocatalytic and antibacterial activity. The droplets of CV solution placed over the coating almost degraded after 360 min of exposure to sunlight owing to the presence of ZnO NPs in the coating. Further, the coating exhibits reasonable antibacterial activity against E. coli and P. aeruginosa whereas it displays low antibacterial activity against S. aureus.Even though, the self-cleaning coating shows promising results, tuning the activity of the photo-catalytic pigment can improve the pollutant degradation efficiency and elevate bactericidal activity.ZnO NPs-impregnated alkyd resin coating for self-cleaning applications is novel.

Electronic-level deciphering of the desalination mechanism of high-performance graphenylene membranes

The insufficiency of available freshwater has surged as a major global concern in recent years, and the issue is raising ever more awareness. Meanwhile, the recent experimental synthesis of graphenylene has inspired researchers to pursue its applicative merits. The related properties regarding lithium-ion storage electrodes and gas separation membranes of graphenylene have been reported. However, the suitability of graphenylene as a desalination membrane has yet to be fully established. In the present study, with a view to delineating the action mechanism of graphenylene desalination membrane, we have dissected its structure and properties through first-principles and molecular dynamics. The results illustrate that graphenylene comprising dodecagonal, hexagonal, and tetragonal carbon rings contains 0.55 nm nanopores, which should permit outstanding desalination properties. In addition, the periodic pore distribution should support stress dispersion in service to preserve membrane integrity. The low water-molecule free-energy barrier, remarkable salt ion adsorption properties, and favorable anti-agglomeration ability endow graphenylene with desirable permeability and selectivity. Furthermore, we demonstrate that graphenylene is a 2D Dirac semi-metallic material. The interlinked electronic structure of which confers it with self-cleaning behavior, facilitating the restoration of water flux. The present research has elucidated the mechanism whereby effective desalination may be achieved on graphenylene membranes. Further, it has clarified the potential applicability of such membranes. They show good prospects for the advancement of seawater desalination technology.

Ultrasonic atomization based fabrication of superhydrophobic and corrosion-resistant hydrolyzed MTMS/PVDF coatings

A stable self-cleaning superhydrophobic coating with reliable corrosion resistance was coated on the aluminum alloy 6061. A dense polyvinylidene fluoride (PVDF) layer was first coated by the doctor blade method, and hydrolyzed methyltrimethoxysilane (HMTMS) nanospheres were then deposited on top of the PVDF using ultrasonic spray hydrolysis technique. Superhydrophobic coatings with a contact angle (CA) of 167° and a sliding angle of 7 ​± ​1° were obtained. The superhydrophobic coating exhibited self-cleaning behavior. The corrosion resistance of the layers was investigated in a 3.5 ​wt% NaCl aqueous solution using potentiodynamic polarization measurement and electrochemical impedance spectroscopy techniques, indicating the high corrosion resistance of the flat PVDF barrier and the excellent resistance of the superhydrophobic coating. The charge transfer resistance of the bare aluminum substrate measured as 6.572 ​kΩ ​cm 2 increased to 848.463 ​kΩ ​cm 2 and 3.411 ​× ​10 3 ​kΩ ​cm 2 with PVDF and HMTMS, respectively. The results showed that a proper superhydrophobic coating with good chemical stability could significantly increase the corrosion resistance of the substrate. We also showed the capability of the novel ultrasonic spray hydrolysis technique in fabricating stable superhydrophobic films for large-scale applications.

Preparation, characterization and performance assessment of antifouling L-Lysine (C, N codoped)-TiO2/WO3-PES photocatalytic membranes: A comparative study on the effect of blended and UV-grafted nanophotocatalyst

In this study, two sets of superior hydrophilic nanofiltration membranes, i.e., mixed matrix membranes and UV-grafted membranes by using L-Lysine (C, N codoped)-TiO2/WO3 (LTW) novel photocatalytic nanocomposite were prepared to amelioration the membrane performance and its antifouling properties. The structural and chemical characteristic, filtration performance, antifouling feature and photocatalytic behavior, and filtration reusability of the fabricated membranes were evaluated. All modified membranes showed better performance compared to the pristine ones. The LTW modified membranes via the UV-grafting method represented considerable enhancement in surface hydrophilicity and filtration performance (contact angle of 42.6º and flux of 49.65 kg/m2.h for optimal membrane). A significant improvement in flux recovery ratio (FRR, 96.96%) and other fouling resistance parameters after fouling was indicative of great antifouling property for these membranes. Also, the modified photocatalytic membrane exhibited excellent rejection of methyl red dye under visible light irradiation (99.01% for optimal UV-grafted membrane). The selected membrane demonstrated high self-cleaning behavior for dye photodegradation. Based on the findings of this study, UV-grafted photocatalytic membranes are expected to have a great potential for practical application in water treatment.

Investigation of chemical etching and surface modification effect on the superhydrophobic, self-cleaning and corrosion behaviour of aluminium substrate

Investigation of chemical etching and surface modification effect on the superhydrophobic, self-cleaning and corrosion behaviour of aluminium substrate

Developing Superhydrophobic Surface Using Multi Jet 3D Printing Durability Analysis

Superhydrophobicity is a surface property used in several sectors, including self-cleaning, drag reduction, improved buoyancy, and antibacterial behavior of the surfaces. The majority of available approaches for creating superhydrophobic surfaces (SHS) are complex and time-consuming. Goal: This article aims to fabricate the SHS by using Multi jet printer three-dimensional (3D) printing. Methods: The texture of cylindrical protrusions (diameter 300 Micro Meter (µm), pitch 400 and 500 µm) and pyramidical (side 200 µm, side by side distance 200 µm, and height 800 µm) micro-pattern were created using Three-Dimensional Printing (3DP) to achieve the SHS. Results: The fabricated geometries yielded a water contact angle of 145 and 148°, respectively. In order to enhance the durability and Water Contact Angle (WCA), 3D printed geometry was treated with an aqueous solution of silica nanoparticles and Hexafor 644-D, which increased the contact angles to 161 and 160° for cylindrical and pyramid patterns, respectively. The reported geometries are durable against peeling tape tests. Hence MJP, based on 3DP, can be used to fabricate the SHS having the geometries height in micron (µm).

Sustainable Self-Cleaning Evaporators for Highly Efficient Solar Desalination Using a Highly Elastic Sponge-like Hydrogel.

Interfacial evaporation using light-absorbing hydrogels offers efficient solar evaporation performance under natural sunlight, ensuring an affordable clean water supply. However, achieving light-absorbing hydrogels with durable and efficient utilization is still a challenge due to inevitable salt accumulation, a difficult-to-control surface morphology, and poor mechanical properties on the surfaces of hydrogel-based evaporators. In this work, a photothermal sponge-like hydrogel with a 3D interconnected porous structure was constructed using low-cost activated carbon as a photothermal material, as well as a double-network polymer chain as the basic skeleton using a simple foaming polymerization strategy. The sponge-like hydrogel evaporator showed tailored surface topography, adequate water transport, excellent elasticity and toughness, good salt rejection, and thermal localization properties. Under the irradiation of simulated sunlight (1.0 kW/m2), a high evaporation rate of 2.33 kg·m-2·h-1 was achieved. Furthermore, efficient salt self-cleaning behavior was achieved due to the fast ion diffusion within the 3D interconnected porous structures. Even in highly concentrated brine of 15 wt %, continuous and efficient water evaporation was still achieved. The excellent evaporation and salt rejection properties of this photothermal sponge-like hydrogel indicated its promising long-term sustainable utilization in seawater desalination.

Wettability tailored superhydrophobic and oil-infused slippery aluminium surface for improved anti-corrosion performance

Inspired by the non-contact nature offered by the superhydrophobic surfaces of living creatures in nature, the superhydrophobic and slippery liquid-infused porous surfaces (SLIPS) have been fabricated to meet the engineering problems including metal corrosion. In this research, we fabricate the hydrophobic, superhydrophobic, hydrophobic lubricant-infused surface (H-SLIPS), and superhydrophobic lubricant infused surface (SH-SLIPS) onto aluminium alloy surfaces and explored their anti-corrosion properties. The hydrophobic and superhydrophobic surfaces are fabricated by hot-water treatment and silicon oil grafting onto the plain and superhydrophilic surface created by hot water treatment of the chemically etched aluminium surface, respectively. The corresponding SLIPS are fabricated by infusion of the silicone oil onto the prepared hydrophobic and superhydrophobic surfaces. Although the superhydrophobic surface exhibits self-cleaning behavior, the SLIPS shows excellent self-healing properties. In addition, the H-SLIPS shows better lubricant layer stability compared to the SH-SLIPS. The corrosion resistive and electrochemical impedance studies illustrate that H-SLIPS surfaces exhibit excellent anti-corrosive properties as compared to other substrates and show long-term performance, even after 30 days. Thus, the study illustrates that H-SLIPS performs better and the infused oil stability is a critical factor for applications like anti-corrosion properties.

Mesoporous silica/epoxy coated cotton fabric for durable oil-water separation

A simple, durable, superior UV-shielded, self-cleanable, hydrophobic/superoleophile cotton fabric was developed using SBA-15 mesoporous silica and epoxy coating (SE). The cotton fabric surfaces after coating with SE showed the highest water contact angle value of 146° and lowest surface free energy of 13.9 mN/m. As a filtration membrane, the developed SE/cotton delivered 95.8% oil–water separation efficiency with a notable flux value of 6800 L/m2h against diesel–water mixture. The presence of an epoxy and silica hybrid layer on the surfaces of cotton fabric induced self-cleaning behavior and notable durability against UV light (UPF-29), pH resistance, washing fastness, and mechanical abrasion. Hence, the present coating developed using mesoporous silica and epoxy can be applied to different types of textile substrates to construct durable low-cost membranes.