Fabrication of Silica/PMMA Composite Based Superhydrophobic Coating by Drop Casting Method

The dirt particles are detached and carried away by freely rolling water drops from superhydrophobic surfaces performing self-cleaning ability. Hence, the self-cleaning superhydrophobic surfaces are gaining huge attention of industries due to their useful day-to-day applications. Herein, we synthesized the hydrophobic silica nanoparticles by sol-gel processing of methyltrimethoxysilane (MTMS). The nanocomposite solution consisting suspension of silica nanoparticles in poly(methylmethacrylate) (PMMA) was applied on glass substrate by simple drop casting method. The microscale roughness of the coating facilitated air trapping in the rough protrusions resulting water contact angle higher than 168°. The self-cleaning ability and mechanical durability of the superhydrophobic coating were also evaluated

Superhydrophobic al2o3-polymer composite coating for self-cleaning applications

Superhydrophobic coatings have a huge impact in various applications due to their extreme water-repellent properties. The main novelty of the current research work lies in the development of cheap, stable, superhydrophobic and self-cleaning coatings with extreme water-repellency. In this work, a composite of hydrothermally synthesized alumina (Al2O3), polymethylhydrosiloxane (PMHS) and polystyrene (PS) was deposited on a glass surface by a dip-coating technique. The Al2O3 nanoparticles form a rough structure, and low-surface-energy PHMS enhances the water-repellent properties. The composite coating revealed a water contact angle (WCA) of 171 ± 2° and a sliding angle (SA) of 3°. In the chemical analysis, Al2p, Si2p, O1s, and C1s elements were detected in the XPS survey. The prepared coating showed a self-cleaning property through the rolling action of water drops. Such a type of coating could have various industrial applications in the future.Funding: This research was funded by Department of Science and Technology (DST), Goernment of India. [DST/INSPIRE/04/2015/000281] and National Natural Science Foundation of China (21950410531).Scopu

Superhydrophobic Surfaces Developed by Mimicking Hierarchical Surface Morphology of Lotus Leaf

The lotus plant is recognized as a ‘King plant’ among all the natural water repellent plants due to its excellent non-wettability. The superhydrophobic surfaces exhibiting the famous ‘Lotus Effect’, along with extremely high water contact angle (>150°) and low sliding angle (<10°), have been broadly investigated and extensively applied on variety of substrates for potential self-cleaning and anti-corrosive applications. Since 1997, especially after the exploration of the surface micro/nanostructure and chemical composition of the lotus leaves by the two German botanists Barthlott and Neinhuis, many kinds of superhydrophobic surfaces mimicking the lotus leaf-like structure have been widely reported in the literature. This review article briefly describes the different wetting properties of the natural superhydrophobic lotus leaves and also provides a comprehensive state-of-the-art discussion on the extensive research carried out in the field of artificial superhydrophobic surfaces which are developed by mimicking the lotus leaf-like dual scale micro/nanostructure. This review article could be beneficial for both novice researchers in this area as well as the scientists who are currently working on non-wettable, superhydrophobic surfaces

Superhydrophobic Surfaces Developed by Mimicking Hierarchical Surface Morphology of Lotus Leaf

The lotus plant is recognized as a ‘King plant’ among all the natural water repellent plants due to its excellent non-wettability. The superhydrophobic surfaces exhibiting the famous ‘Lotus Effect’, along with extremely high water contact angle (>150°) and low sliding angle (<10°), have been broadly investigated and extensively applied on variety of substrates for potential self-cleaning and anti-corrosive applications. Since 1997, especially after the exploration of the surface micro/nanostructure and chemical composition of the lotus leaves by the two German botanists Barthlott and Neinhuis, many kinds of superhydrophobic surfaces mimicking the lotus leaf-like structure have been widely reported in the literature. This review article briefly describes the different wetting properties of the natural superhydrophobic lotus leaves and also provides a comprehensive state-of-the-art discussion on the extensive research carried out in the field of artificial superhydrophobic surfaces which are developed by mimicking the lotus leaf-like dual scale micro/nanostructure. This review article could be beneficial for both novice researchers in this area as well as the scientists who are currently working on non-wettable, superhydrophobic surfaces

Transparent, Adherent, and Photocatalytic SiO2-TiO2 Coatings on Polycarbonate for Self-Cleaning Applications

Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO2-TiO2 coatings on polycarbonate (PC) substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO2-TiO2 coatings. The effect of different vol% of SiO2 in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO2 in TiO2 showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO2 in TiO2. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20) of SiO2 in TiO2 showed high transparency in the visible range

Dynamic Electrowetting-on-Dielectric (DEWOD) on Unstretched and Stretched Teflon

Dynamic electrowetting-on-dielectric (DEWOD) of the unstretched and stretched Teflon is reported in the experiments with water drop impact and rebound. We explore experimentally and theoretically the situation with the capacitance different from the standard static electrowetting. Deionized water drops impact onto either an unstretched hydrophobic Teflon surface or Teflon stretched up to 250% strain normally to the impact direction. The surface roughness of the unstretched Teflon increased after stretching from 209.9 to 245.6 nm resulting in the increase in the equilibrium water contact angle from 96 ± 4° to 147 ± 5°, respectively. The electric arrangement used in the drop impact experiments on DEWOD results in a dramatically reduced capacitance and requires a much higher voltage to observe EW in comparison with the standard static case of a drop deposited on a dielectric layer and attached to an electrode. In the dynamic situation we found that as the EW sets in it can greatly reduce the superhydrophobicity of the unstretched and stretched Teflon. At 0 kV, the water drop rebound height (<i>h</i>_max) is higher for the stretched Teflon (<i>h</i>_max ≈ 5.13 mm) and lower for the unstretched Teflon (<i>h</i>_max ≈ 4.16 mm). The EW response of unstretched Teflon is weaker than that of the stretched one. At the voltage of 3 kV, the water drop sticks to the stretched Teflon without rebound, whereas water drops still partially rebound (<i>h</i>_max ≈ 2.8 mm) after a comparable impact onto the unstretched Teflon. We found a sharp dynamic EW response for the stretched Teflon. The contact angle of deionized water ranged from 147 ± 5° (superhydrophobic) to 67 ± 5° (partially hydrophilic) by applying external voltage of 0 and 3 kV, respectively. Dynamic electrowetting introduced in this work for the first time can be used to control spray cooling, painting, and coating and for drop transport in microfluidics

Mechanism of Selective Qβ Bacteriophage Inactivation under the Presence of <i>E. Coli</i> Using Ground Rh-Doped SrTiO₃ Photocatalyst

Photocatalysts have recently attracted attention for removing infectious-disease-causing bacteria and viruses. Among such photocatalysts, ground Rh-doped SrTiO3 (“g-STO:Rh”) has been found to have biospecificity that reduces the Qβ phage infectivity under conditions that did not decrease the E. coli survival rate. Elucidating the mechanism of selective antiphage activation is important for developing photocatalysts that act effectively against specific microorganisms. In this study, SDS-PAGE and quantitative PCR showed that a g-STO:Rh-treated Qβ phage preferentially inactivated the A2 protein involved in attachment to host cells. The analysis of the photocatalyst-treated ovalbumin using g-STO:Rh indicated that the protein’s isoelectric point significantly influenced the initial interaction with g-STO:Rh. However, once the protein is absorbed, it was decomposed without the release of intermediates. Furthermore, an inactivation assay for four different phages by photocatalyst treatment using g-STO:Rh revealed that phages with positively charged proteins are highly susceptible to inactivation, and the accessibility of critical components to g-STO:Rh influences susceptibility. We conclude that the selective antiphage activation of g-STO:Rh depends on the adsorption efficiency of the protein and g-STO:Rh

Fabrication of robust self-cleaning superhydrophobic coating by deposition of polymer layer on candle soot surface

A facile and inexpensive way have been developed to fabricate robust self-cleaning superhydrophobic coating by depositing polymer layer on candle soot (CS) surface using dip coating method. The stability and robustness of the CS deposited superhydrophobic surface is much weaker due to weak interaction and nonchemical bonding with the substrate. We introduced a thin layer of polystyrene, polyethylene, polypropylene (PP), and polyvinylidene fluoride on CS surface in order to improve its mechanical properties. The fabricated surfaces with the use of respective polymers exhibited water contact angles of nearly 170, 174, 175, and 171° with sliding angles of 2, 1, 1, and 3°, respectively. Although, all the polymers used in this work exhibited excellent superhydrophobic and self-cleaning surface property, we found that the PP deposited CS surface exhibit better stability against water jet hitting and water drop impact tests. The PP deposited CS surface almost maintained their surface properties even after 50 cycles of sandpaper abrasion and 20 cycles of adhesive tape peeling tests. The mechanical durability tests confirmed that PP is a better polymer to improve the long-term durability of CS surface. Therefore, this simple, time saving, and inexpensive method for fabricating superhydrophobic coating can be used for potential industrial application.National Natural Science Foundation of China, Grant/Award Number: 21950410531; Henan University; DST ? INSPIRE Faculty Scheme, Department of Science and Technology (DST), Govt. of India, Grant/Award Number: DST/INSPIRE/04/2015/000281 Funding informationScopu

Recent Advances in durability of superhydrophobic self-cleaning technology: A critical review

Self-cleaning concept has achieved significant attention because of their distinct features and inclusive range of probable applications in various fields. Inspired from the lotus effect; the self-cleaning properties showed by the leaves due to the micro and nanoscopic design which reduces the water droplets adhesion to the surface, self-cleaning technology (SCT) plays a significant role in the current time in various applications. One of its special features is its ability to keep the surface clean and maintain the self-cleaning property stable under severe environmental conditions over an intended period of time. This review introduces an overview of the fabrication techniques for superhydrophobic coating and self-cleaning (SC) applications in various fields. The SCT has applications in areas such as textiles, cotton-fabrics garments, buildings construction, lavatories, domestic-automobiles windows, architectural heritage, and photovoltaic and solar cells. As SCT has wide range of applications, there is a need for a deeper understanding of the resilience and preparation of SC surfaces. Therefore, we have discussed the major applications of SCT in building, toilet, mineral paints for architectural heritage, photovoltaic devices or solar cell, fabrics or textile industry in this review. Apart from this, we have also added information regarding the techniques of SC superhydrophobic surfaces and flexible self-cleaning materials and their applications. SCT naturally suffers from great issues in their durability and stability. As the durability of SCT is significant in daily human life, it is intensively reflected in this literature survey. Furthermore, the ongoing progress and potential efforts in the recent innovative applications of SCT along with the critical conclusions, forthcoming views, and obstacles on the field of the durability of SCT are discussed in the presented survey.Authors acknowledge the support provided by program carried out under the framework of Postdoctoral Fellowship, Henan University Kaifeng, China. This work is financially supported by DST ? INSPIRE Faculty Scheme, Department of Science and Technology (DST), Govt. of India. [DST/INSPIRE/04/2015/000281]. We greatly appreciate the support of the National Natural Science Foundation of China (21776061) and (21950410531), Foundation of Henan province (182102410090). S. Nagappan and C. S. Ha thanks to the financial support from the National Research Foundation of Korea (NRF) Grant funded by the Ministry of Science and ICT, Korea (NRF2017R1A2B3012961); Brain Korea 21 Plus Program (21A2013800002).Scopu