Self-cleaning Surfaces Research Articles

Effect of Plasma Treatment on Self-Cleaning Features of Acrylic Paint/TiO2-Coated Surfaces for Environmental Pollutant Removal

This study investigates the characterization and performance of self-cleaning TiO2 surfaces synthesized through a one-step preparation process, followed by enhancement via plasma treatment. The process involved coating aluminum foil with an acrylic paint mixture containing nanoparticles of different mass compositions and subsequent plasma treatment using a continuous plasma arc. Scanning electron microscopy revealed the morphology of the treated surfaces, showing an increase in surface area of plasma-treated materials. Energy-dispersive X-ray spectroscopy revealed changes in oxygen and titanium in acrylic paint/TiO2 surfaces as the TiO2 content increased, indicating successful TiO2 incorporation. Raman spectroscopy showed that the bulk structure of self-cleaning acrylic paints is mainly preserved after plasma treatment. Alternating current impedance spectroscopy assessed that plasma treatment reduced agglomeration and increased active sites, especially for the acrylic paint/TiO2 surfaces with 0.5 mg/cm3 TiO2. The contact angle measurements indicated that plasma treatment enhanced the superhydrophobic characteristics and potential self-cleaning abilities of produced acrylic paint/TiO2 surfaces. The efficacy of these plasma-treated surfaces in self-cleaning was evaluated by testing their performance against puddle sediment and automotive oil samples. The study demonstrated that plasma treatment positively impacted the self-cleaning ability of the acrylic paint/TiO2 surfaces, particularly those with 0.5 mg/cm3 TiO2. This enhancement was attributed to the formation of functional groups, improved water repellency, and possible increases in surface area, which collectively contribute to the sustainable self-cleaning properties of the treated surfaces.

Investigation of the Effects of Different Phases of TiO2 Nanoparticles on PVA Membranes

Introduction: PVA/TiO2 nanocomposite membranes are prepared by solution casting technique where different phases of TiO2 nanoparticles like brookite, brookiterutile and rutile are dispersed in PVA matrix. Sol-gel method was employed to prepare TiO2 nanoparticles, while different phases of TiO2 have been obtained by controlling the calcination temperature. Methods: PVA/TiO2 nanocomposite membranes were characterized by XRD, FTIR, AFM, TEM, UV-visible and PL techniques. XRD results confirmed the presence of different phases of TiO2, exhibiting 3.3 nm, 8.4 nm, and 35.7 nm mean crystalline size. The XRD studies also confirmed that TiO2 nanoparticles became properly dispersed to the PVA matrix, leading to increased PVA crystallinity after doping of different phases of TiO2 nanoparticles. UV-visible analysis revealed an increase in absorption intensity and peak position shifts slightly towards longer wavelengths, which indicates that nanofillers tuned the band gap of PVA. The doping of the TiO2 (brookite) phase in the PVA matrix results in a decreased in PL intensity. Results: This suggests that the PVA/TiO2 (brookite) membrane exhibits a greater degree of photocatalytic activity in comparison to the other two composites. According to the FTIR investigation, the hydroxyl (OH) groups present in PVA interact with the dopants Ti+ ions via intra- and intermolecular hydrogen bonds to produce charge transfer complexes (CTC). The AFM study shows surface roughness details for PVA and PVA/TiO2 composite membranes. The average grain size of TiO2 nanoparticles calculated from TEM images is in good agreement with the grain size calculated by XRD. Conclusion: By adjusting the phase of TiO2 nanoparticles into PVA matrix, composites can be developed that are optimized for a variety of applications such as water purification, UV protection, self-cleaning surfaces, lithium-ion batteries, and optoelectronic devices.

Exploring the photocatalytic and antibacterial activity of Ce-doped TiO2 nanoparticles with remarkable self-cleaning superhydrophilic surface for outdoor application

Exploring the photocatalytic and antibacterial activity of Ce-doped TiO2 nanoparticles with remarkable self-cleaning superhydrophilic surface for outdoor application

Water Droplet Equilibration on Silicone Elastomer Substrates Containing Mobile Silicones.

Understanding interfacial behavior at the water/silicone elastomer interface is vital in many applications, including microfluidics, antibiofouling, and self-cleaning surfaces. Silicone elastomers are not always static systems, however. Unreacted silicone molecules within a substrate may change the water-wetting behavior compared to fully reacted substrates. To investigate the impact of free silicone species at the interface, we systematically studied water wettability as a function of contact time with various silicone elastomer substrates. One set of Sylgard 184 substrates was prepared from curing at optimal stoichiometry and included doses of silicone molecules of varying molecular weights. Another set of substrates was made by mixing Sylgard 184 in imbalanced ratios to provide incomplete cross-linking. In the absence of added silicone oils, we observe a linear decrease in contact angle with time due to the evaporation of water. However, within certain molecular weight and loading levels of additional inert oils, nonlinear wetting behavior occurs as oils migrate to the interface and the system stabilizes. Similar nonlinear wetting behavior occurs without including silicone oils by mixing pure Sylgard 184 in very imbalanced mixing ratios, resulting in incomplete cross-linking. Such substrates contain unbound mobile silicone species that diffuse to the water-substrate interface. We show how the water contact angle technique can elucidate the presence of unbound silicone oils in the substrate.

Hierarchical Micro/Nanostructures with Anti-Reflection and Superhydrophobicity on the Silicon Surface Fabricated by Femtosecond Laser

In this paper, hierarchical micro/nano structures composed of periodic microstructures, laser-induced periodic surface structures (LIPSS), and nanoparticles were fabricated by femtosecond laser processing (LP). A layer of hydrophobic species was formed on the micro/nano structures through perfluorosilane modification (PM). The reflectivity and hydrophobicity’s influence mechanisms of structural height, duty cycle, and size are experimentally elucidated. The average reflectivity of the silicon surface in the visible light band is reduced to 3.0% under the optimal parameters, and the surface exhibits a large contact angle of 172.3 ± 0.8° and a low sliding angle of 4.2 ± 1.4°. Finally, the durability of the anti-reflection and superhydrophobicity is also confirmed. This study deepens our understanding of the principles of anti-reflection and superhydrophobicity and expands the design and preparation methods for self-cleaning and anti-reflective surfaces.

Advancing Solar Power Efficiency: Innovations in Material Science and System Optimization for Enhanced Solar Energy Conversion

This study aims to advance solar power efficiency through innovations in material science, surface engineering, and system optimization. The research integrates experimental testing and computational modeling to assess improvements in energy conversion efficiency. The methodology includes testing photovoltaic materials such as perovskite and multi-junction cells, anti-reflective coatings, self-cleaning surfaces, and optimizing panel orientation, cooling systems, and Maximum Power Point Tracking (MPPT) algorithms. Perovskite cells demonstrated a 22% increase in efficiency, while multi-junction cells achieved up to 35% efficiency. Anti-reflective coatings and self-cleaning surfaces improved energy capture by 4% and 7%, respectively. System optimization, including dual-axis trackers and AI-enhanced MPPT algorithms, provided additional efficiency gains of up to 25% and 10%, respectively. These findings demonstrate significant advancements in solar panel performance, providing a clear path for enhancing scalability and commercial viability in diverse environmental conditions. The integration of innovative materials and system optimizations presents a promising solution for making solar energy more sustainable and cost-effective. Future research should focus on improving the durability and reducing the costs of these technologies for widespread adoption.

Titanium Dioxide and Photocatalysis: A Detailed Overview of the Synthesis, Applications, Challenges, Advances and Prospects for Sustainable Development

The term “photocatalysis” has recently gained high popularity, and various products using photocatalytic functions have been commercialized. Of all the materials that may be used as photocatalysts, titanium dioxide (TiO2) is virtually the only one that is now and most likely will remain appropriate for industrial application. Water and air purification systems, sterilization, hydrogen evolution, self-cleaning surfaces, and photoelectrochemical conversion are just a few of the products and applications in the environmental and energy domains that make extensive use of TiO2 photocatalysis. This is due to the fact that TiO2 has the lowest cost, most stability, and most effective photoactivity. Furthermore, history attests to its safety for both people and the environment because it has been used as a white pigment since antiquity. This review discusses some important aspects and issues concerning different synthesis methods and their influence on the structure and properties of TiO2, as well as the concept of photocatalysis based on it as a promising biocompatible functional material that has been widely used in recent years. The advantages of TiO2 applications in various fields of science and technology are discussed, including environmental protection, photocatalysis including self-cleaning surfaces, water and air purification systems, hydrogen liberation, photovoltaic energy, cancer diagnosis and therapy, coatings and dental products, etc. Information on the structure and properties of TiO2 phases is presented, as well as modern methods of synthesizing functional materials based on it. A detailed review of the basic principles of TiO2 photocatalysis is then given, with a brief introduction to the modern concept of TiO2 photocatalysis. Recent advances in the fundamental understanding of TiO2 photocatalysis at the atomic-molecular level are highlighted, and advances in TiO2 photocatalysis from the perspective of design and engineering of new materials are discussed. The challenges and prospects of TiO2 photocatalysis are briefly discussed.

Designing lotus-like superhydrophobic self-cleaning surface using carbon nanotubes

Designing lotus-like superhydrophobic self-cleaning surface using carbon nanotubes

Development of Self-Cleaning Aluminum Surface through an Eco-Friendly Process

Development of Self-Cleaning Aluminum Surface through an Eco-Friendly Process

Durable self-cleaning superhydrophobic cotton fabrics for wearable textiles

Cotton fabric is widely used in various industrial goods due to its ability to enhance aesthetic appeal, but preserving its shine and genuine appearance presents a significant challenge. In this work, a durable self-cleaning superhydrophobic surface suitable for wearable textiles was achieved on cotton fabrics by applying a composite coating of stearic acid-modified titanium oxide (TiO2) nanoparticles and polydimethylsiloxane (PDMS) through a simple dip/spray coating technique. The fabric surface displayed an exceptional water contact angle (WCA) of 165 ± 2° and a minimal slide angle (SA) of approximately 2°, demonstrating outstanding water repellency and sliding characteristics. The surface exhibited impressive self-cleaning abilities for both dust particles and muddy water. The coated cloth maintained its exceptional superhydrophobic properties even after being subjected to 40 abrasion cycles, 30 adhesive tape peels, nearly 60 min of ultrasound treatment, and 30 washing cycles. Additionally, the as-coated cotton showed excellent chemical stability, tensile strength, flexibility, air permeability and breathability. The model trials with a baby doll have proven the high possibility of commercializing self-cleaning clothing in this research.

Functionalization of Polypropylene by TiO2 Photocatalytic Nanoparticles: On the Importance of the Surface Oxygen Plasma Treatment.

A new two-step method for developing a nanocomposite of polypropylene (PP) decorated with photocatalytically active TiO2 nanoparticles (nTiO2) is proposed. This method involves the low-temperature plasma functionalization of polypropylene followed by the ultrasound-assisted anchoring of nTiO2. The nanoparticles, polymeric substrate, and resultant nanocomposite were thoroughly characterized using nanoparticle tracking analysis (NTA), microscopic observations (SEM, TEM, and EDX), spectroscopic investigations (XPS and FTIR), thermogravimetric analysis (TG/DTA), and water contact angle (WCA) measurements. The photocatalytic activity of the nanocomposites was evaluated through the degradation of methyl orange. The individual TiO2 nanoparticles ranged from 2 to 6 nm in size. The oxygen plasma treatment of PP generated surface functional groups (mainly -OH and -C=O), transforming the surface from hydrophobic to hydrophilic, which facilitated the efficient deposition of nTiO2. Optimized plasma treatment and sonochemical deposition parameters resulted in an active photocatalytic nTiO2/PP system, degrading 80% of the methyl orange under UVA irradiation in 200 min. The proposed approach is considered versatile for the functionalization of polymeric materials with photoactive nanoparticles and, in a broader perspective, can be utilized for the fabrication of self-cleaning surfaces.

Bioinspired Hierarchical T Structures for Tunable Wettability and Droplet Manipulation by Facile and Scalable Nanoimprinting.

Developing surfaces that effectively repel low-surface-tension liquids with tunable adhesive properties remains a pivotal challenge. Micronano hierarchical re-entrant structures emerge as a promising solution, offering a robust structural defense against liquid penetration, minimizing area fraction, and creating narrow gaps that generate substantial upward Laplace pressure. However, the absence of an efficient, scalable, and tunable construction method has impeded their widespread applications. Here, drawing inspiration from springtail epidermal structures, octopus suckers, and rose petals, we present a scalable manufacturing strategy for artificial micronano hierarchical T-shaped structures. This strategy employs double-transfer UV-curing nanoimprint lithography to form nanostructures on microstructured surfaces, offering high structural tunability. This approach enables precise control over topography, feature size, and arrangement of nano- and microscale sections, resulting in superamphiphobic surfaces that exhibit high contact angles (>150°) and tunable adhesive forces for low-surface-energy liquids. These surfaces can be applied to droplet-based microreactors, programmable droplet-transfer systems, and self-cleaning surfaces suitable for various liquids, particularly those with low surface tension. Remarkably, we have also succeeded in fabricating the hierarchical structures on flexible and transparent substrates. We demonstrate the advantages of this strategy in the fabrication of hierarchical micronanostructures, opening up a wide range of potential applications.

The Design and Analysis of the Fabrication of Micro- and Nanoscale Surface Structures and Their Performance Applications from a Bionic Perspective.

This paper comprehensively discusses the fabrication of bionic-based ultrafast laser micro-nano-multiscale surface structures and their performance analysis. It explores the functionality of biological surface structures and the high adaptability achieved through optimized self-organized biomaterials with multilayered structures. This study details the applications of ultrafast laser technology in biomimetic designs, particularly in preparing high-precision, wear-resistant, hydrophobic, and antireflective micro- and nanostructures on metal surfaces. Advances in the fabrications of laser surface structures are analyzed, comparing top-down and bottom-up processing methods and femtosecond laser direct writing. This research investigates selective absorption properties of surface structures at different scales for various light wavelengths, achieving coloring or stealth effects. Applications in dirt-resistant, self-cleaning, biomimetic optical, friction-resistant, and biocompatible surfaces are presented, demonstrating potential in biomedical care, water-vapor harvesting, and droplet manipulation. This paper concludes by highlighting research frontiers, theoretical and technological challenges, and the high-precision capabilities of femtosecond laser technology in related fields.

A comprehensive review on realization of self-cleaning surfaces by additive manufacturing

A comprehensive review on realization of self-cleaning surfaces by additive manufacturing

Reticulated mesoporous TiO2 scaffold for self-cleaning surfaces

Interest in self-cleaning coatings is rising due to their potential to enhance comfort and quality of life in polluted urban environments, driving the search for materials with optimal physical properties. Convergent with this goal, this study investigates the wetting properties and photo-catalytic efficiency of reticulated TiO2 layers. It shows that these properties are significantly influenced by the topographical characteristics of the TiO2 surface, which can be precisely controlled through variations in pulverization pressure and low-temperature post-annealing treatments. Post-deposition annealing of the TiO2 layers achieves 100 % self-cleaning efficiency for both thick and thin films, with optical transmission ranging from approximately 60 %–80 % in the visible spectrum. Additionally, the TiO2 layers exhibited promising capabilities for eliminating pathogenic microorganisms and disinfecting surfaces. The underlying causal factors of these remarkable and technologically promising surface features are explored and discussed.

Robust photopolymerized superoleophobic/superhydrophilic mesh for oil-water separation

Selective superwetting surfaces preserve the opposite superwetting properties of oil and water and have attracted considerable attention for their application in oil-water separation owing to their efficient surface energy since 2000. Among these surfaces, superoleophobic/superhydrophilic surfaces are considered remarkable because of their anti-oil properties. The coexistence of superoleophobicity and superhydrophilicity poses a challenge based on the traditional surface/interface theory. However, the fabrication of superoleophobic surfaces requires extremely low surface energy, which is achieved by introducing compounds with long fluorocarbon chains. However, these compounds are harmful to the environment. Herein, a mesh with superoleophobic/superhydrophilic properties was developed by coating a chemically etched copper mesh substrate with photopolymerized short fluorocarbon chains and water-insoluble hydrophilic monomers. This mesh can separate different types of oil-water mixtures with a separation efficiency of >99 %. The mesh demonstrated excellent underwater stability as well as chemical and mechanical durability. The water resistance and chemical durability of the mesh are stronger than those of the control copper mesh using metal ions and long fluorocarbon chains. Moreover, oil-water separation was achieved even after immersion in deionized water and salt, acid, and alkali solutions. In addition, the mesh preserves the ability of oil-water separation after being cleaned and reused for 10 times. The proposed superoleophobic/superhydrophilic mesh offers a solution for continuous oil-water separation and has prospects for developing anti-fouling/sweat-absorbing fabrics and self-cleaning surfaces.

Sol gel synthesis of TiO2@ZnO composites for self-cleaning and antimicrobial coating

Abstract In recent years, the development of advanced materials for applications in self-cleaning surfaces and antimicrobial coatings has received considerable attention due to its potential impact on environmental sustainability and public health. Among the emerging materials, metal oxide-based photocatalysts have shown promise in addressing these challenges. In this context, the present study focuses on the promise sol-gel synthesis and potential photocatalytic properties of TiO2@ZnO (x = 0.6 - 0.9) nano-scaled particles, with particular emphasis on their applications in self-cleaning and microbial coatings. The choice of TiO2@ZnO (x = 0.6 - 0.9) as the subject of investigation is driven by the advantageous properties of both titanium dioxide (TiO2) and zinc oxide (ZnO). TiO2 is known for its exceptional photocatalytic activity, while ZnO is known for its antimicrobial properties. By combining these two metal oxides in a controlled manner, we aim to harness their synergistic effects to create a multifunctional material with enhanced performance. A titanium (IV) isopropoxide and zinc acetate dihydrate have been used as precursors for the so-gel process. The synthesised powders were evaluated by X-ray diffraction analysis and Raman spectroscopy to determine the allotropy of TiO2 and possible lattice distortions. The optical band gap (Egap) was evaluated by molecular reflection UV-VIS spectroscopy. In addition, size and morphology were determined by scanning electron microscopy (SEM).

Fluorine-free Superhydrophobic Stearic Acid Modified Kaolin Nanoparticles for Self-cleaning Silicone Rubber Surface

This study introduces fluorine-free nanoparticles to innovate superhydrophobic surfaces for self-cleaning applications, addressing environmental concerns linked to fluorine-based compounds. The method involves modifying kaolin nanoparticles with stearic acid and integrating them into silicone. The surface of stearic acid-kaolin nanoparticles exhibits a contact angle of 149.4° ± 3.3, while the resulting composite film exhibits a contact angle of 113.9° ± 5.8. The surface roughness of the silicone rubber surfaces increases proportionally with higher concentrations of stearic acid-modified kaolin nanoparticles. Field Emission Scanning Electron Microscopy (FESEM) analysis demonstrates the successful coverage of kaolin nanoparticles-stearic acid on resulting film. Self-cleaning performance is evaluated by simulating the deposition of graphite powder onto the surfaces and subsequently observing the behaviour when water is dropped on them revealing their remarkable self-cleaning properties.

Excellent self-cleaning surface achieved through the synergistic effect of superhydrophilicity and photocatalysis of PVDF-TiO2-HAP coating

With the increasing demand for living environment, high-performance self-cleaning coatings have become an urgent need in the development of new building industry. Herein, a TiO2-HAP-PVDF self-cleaning coating was successfully developed using a facile precursor mixing method, where porous hydroxyapatite (HAP) was used to facilitate the adsorption of pollutants, TiO2 served as photocatalyst to decompose pollutants, and polyvinylidene fluoride (PVDF) served as adhesive to combine TiO2 with HAP. Owing to the synergistic effect of superhydrophilicity and photocatalysis, the TiO2-HAP-PVDF coating displays outstanding self-cleaning performance. Furthermore, the as-fabricated coating attached to aluminum veneer not only resists mechanical abrasion such as rainwater, sand flow and sandpaper, but also exhibits good stability in the extremely temperatures from -196 to 150 °C, as well as in strong acid and alkaline solutions, and even presents satisfactory performance after 8000 hours of outdoor service test. These merits open exciting possibilities for the industrial application of self-cleaning coating.

The Droplet Creeping-Sliding Dynamic Wetting Mechanism on Bionic Self-Cleaning Surfaces.

The dynamic wetting behavior of droplets has been of wide concern due to the hazards of accretion/icing of supercooled droplets on engineering components/systems served in low temperature freezing rain environment; thus, it is urgent to establish the relationship between droplet depinning/removing behaviors and surface characteristics. In this article, the actual rotation conditions of moving components such as wind turbine blades are simulated. The self-cleaning hydrophobic coating surface(S1) and bionic superhydrophobic coating surface(S2) show outstanding droplet removal performance compared to hydrophilic bare steel surface(S0), and the average speed of the droplet removal is increased by 400-500%. The "creeping-sliding" behavior of droplets on self-cleaning coatings is investigated by the change of droplet displacement(ΔD). The effect of the energy storage caused by the droplet creeping process provides initial kinetic energy for the droplet removal. Combined with the experimental data and theoretical model, the critical depinning resistance is calculated. The difference of the wetting interface free energy(ΔEx) during the dynamic wetting process of the droplets on the bionic superhydrophobic self-cleaning surface is researched. And the influence mechanism of the droplet embedded depth(x) on the creeping/sliding behavior in the nanotexture is clarified. Thus, the mechanical criterion of droplet depinning is proposed (the error is about 10%). The results can provide a theoretical basis for the design principle of antifreezing rain coatings on moving components.