The journal is making a noticeable progress in both the number of publications and their quality. We published seven issues in 2023, increased from six in 2022, with further projected expansion to eight issues in 2024. The ISI impact factor for Surface Innovations improved from about 2.4 in 2022 to 3.5 in 2023, with a projected further surge in 2024. Thank you to all the contributors, external editors, and readers! Special thanks to the journal editorial board members who have worked hard for the success of this international journal.
Several new members have been added to the journal Editorial Board in 2023 to expand a spectrum of expertise. The new members include Prof. Ali A. Atta (Jouf University, Saudi Arabia) with expertise in surface modification, functionalization and characterization, nanocomposite thin films, advanced materials, and electrical materials; Dr. Reza Bakhsheshi-Rad (Islamic Azad University, Iran) with expertise in nanostructured materials, corrosion, regenerative medicine and tissue engineering, and advanced materials; Prof. Alexandre Emelyanenko (Russian Academy of Science, Russia) with expertise in superhydrophobic surfaces, wetting, colloidal forces, thin liquid films, and physical chemistry of materials; Prof. Yun Hang Hu (Michigan Technological University, USA) with expertise in energy materials, photocatalytic materials, nano-structured materials, surface modification and functionalization; Prof. Ahmad Fauzi Ismail (Universiti Teknologi Malaysia, Malaysia) with expertise in membranes for water desalination, wastewater treatment, gas separation processes, and oil refining, and photocatalytic materials; and Prof. Seeram Ramakrishna (National University of Singapore, Singapore) with expertise in advanced materials, additive manufacturing, nanotechnology, biomaterials, and sustainable materials. Please join me in welcoming these distinguished scientists to the Editorial Board of Surface Innovations.
In the first (double) issue of 2024, we offer a review article on spreading and adhesion measurements for fluid droplets using a microbalance,1 a short letter on adhesion and friction between Johansson’s blocks,2 and ten original contributions on molecular dynamic simulation of self-crimping of polymers inside carbon nanotubes,3 formulation of antimicrobial cotton fabrics,4 instability of Leidenfrost drops,5 freezing phenomenon of water droplets,6 fabrication of wettability patterns on metal substrates,7 hydrogen-beam-irradiation of polydimethylsiloxane8 and polyvinyl alcohol,9 use of machine learning in predicting bacteria concentration in beach sand,10 preparation and testing corrosion resistance of polyurethane coating,11 and a colored titanium/zirconium-based conversion coating for aluminum alloys.12
Liquid spreading and adhesion have been typically analyzed through measurements of contact angles. However, significant drawbacks of contact angle measurements include a subjective and arbitrary selection of the stages of liquid spreading and wetting at which the contact angles are measured and more importantly, liquid adhesion is only estimated based on either ill-defined theoretical equations or experimental contact angle values. With the advent of sensitive micro-balances, the droplet (or bubble) spreading and its adhesion with a solid surface of varying shape, surface functionality and topography are measured directly, without a need for additional calculations, as reviewed in details by Jiang and Drelich.1 The profile of the forces with respect to surface position (and time) is recorded automatically by the software, and a camera is used for recording of attachment, spreading, adhesion, and detachment events, allowing the individual recorded frames to be used to analyze the droplet dimensions and to measure the contact angle at various stages of droplet/bubble spreading and retreat. The review summarizes the very recent literature reports on measurements and interpretation of fluid droplet spreading and adhesion. Two original contributions on the use of a microbalance in measurements fluid-solid interactions were published in this journal in 2018.13,14
In a letter, Breki and Nosonovsky2 introduce the phenomenon of adhesion between two Johansson's blocks, a tool used for the calibration of metrology equipment, and length measurements, amongst other applications. The authors discuss several adhesion mechanisms and conclude that the oxide film is a probable cause of changes in adhesion between blocks. After removing the oxide film from the steel surface, a strong adhesion between blocks was restored.
In a new original contribution, Gong et al.3 investigate the self-crimping behavior of multi-chain polystyrene inside carbon nanotubes through molecular dynamics simulation. They demonstrate that both van der Waals and π-π interactions between polystyrene chains and carbon nanotubes control self-assembling of the polymer in parallel arrangements and helix configurations. The factors that affect the self-assembling process include the length and chain number of polymer, the diameter of carbon nanotubes, and temperature. This theoretical work can inspire experimentalists to explore manufacturing polymer-carbon nanotube hybrid structures for advanced composites and functional devices. This work is a continuation of a previous contribution on molecular dynamics simulations of interactions between polymers and single-walled carbon nanotubes published in 2019.15
Antimicrobial fabrics, including wound dressing fabrics, that protect against a wide spectrum of bacteria, germs and mold, are in demand not only by healthcare and medical industries, but also in other sectors of our daily life and industrial applications.15–18 In a new contribution,4 an international research team from Malaysia and Pakistan offer antimicrobial functionality to cotton fabrics by treating the fabrics with the natural extract from pods of the Cupressaceae plant, known for antiseptic properties. After optimizing the fabric treatment technology with potash alum as a mordant, the authors demonstrate durable antimicrobial cotton fabric that shows promising activity against Gram-negative and Gram-positive bacteria. This invention is based on a natural antimicrobial agent and could find applications in wound dressing and hospital staff clothing.
A liquid droplet can be levitated on its own vapor above a hot plate.19 This Leidenfrost effect was investigated, both theoretically and experimentally, in a circular configuration in the past by Mrinal et al.20 In the second contribution from the same research team, the authors study theoretically and experimentally a stability of Leidenfrost water drops in rectangular configurations of multiple rods and rectangular mesh elements.5 They demonstrate that the critical dimension for determining Leidenfrost is the diameter of the cylinder in a rectangular configuration. They also found that the threshold value of this diameter correlates with the capillary length of water. This work provides the foundation for a design of large rectangular containers that could stabilize Leidenfrost drops.
In the next contribution, the science and research shift from analysis of water drops exposed to a high temperature to drops under freezing conditions. Specifically, Starostin et al.6 address, both experimentally and theoretically, the problem of cooling and freezing of a sessile water droplet on a horizontal polymer surface, by considering the case of a relatively wettable polymer (PMMA) and that of a superhydrophobic surface (suitably coated PMMA). The authors describe a version of the classic Stefan problem, in which a growing ice front is limited by the diffusion of the latent heat of freezing back through the ice just formed. In this case, a peculiarity of the heat transfer induces the eventual tip of the frozen droplet to be canted at an angle to the surface normal. A new computational method proposed in this paper predicts the propagation of the freezing front in the droplet quite accurately.
Progress in patternable printing, and design of water collection and heat-dissipation devices depends on fabrication of extreme-wettability-patterned surfaces. The research team led by Prof. Liu reveal their innovation on fabrication of wettability patterns on copper substrates using chemical processing combined with masking technology.7 The authors were able to produce patterned surfaces with wettability contrasting from superhydrophilic to superhydrophobic using three different strategies. The tests on sandpaper abrasion, thumb pressing, flushing with water, and boiling in water confirm high durability of fabricated patterns. Both simplicity and low cost of patterning technologies developed should attract attention of researchers working on new devices designed to control both the water shape and direction of its transportation.
In two new contributions, Alotaibi et al. describe surface modification and the resulting optical properties of flexible polydimethylsiloxane8 and poly(vinyl alcohol)9 after the polymer is irradiated with hydrogen ion beams. The authors determined the optical band gaps as well as Urbach energies of pristine and treated polymer films utilizing Tauc's formula. Optic metrics such as extinction coefficients, refractive index, optical conductivities, and dielectric constants, as well as dielectric losses for pristine and irradiated samples were calculated. The studies demonstrate the positive effect of hydrogen ion irradiation on optical properties of both polydimethylsiloxane and poly(vinyl alcohol), opening opportunities for application of these irradiated polymeric films in optoelectronic devices. The ion irradiation and its benefits were also described by the same research group in several previous papers that we recommend to everyone who is exploring surface and thin film modifications through ion beam treatments.21,22
Machine learning is a relatively new field of study in which artificial intelligence and computer science are used to develop statistical algorithms and find complex correlations among different variables and provide more accurate predictions, typically not achievable by conventional analysis. The state-of-the-art review on machine learning approaches and data topology methods in the context of tribological applications was published in Surface Innovations by Hasan and Nosonovsky in 2022.23 Here, in an original contribution on machine learning, Hasan et al.10 describes the physicochemical, bacteriological, and wetting properties of beach sand and evaluate five machine learning regression models to predict E. coli concentrations. The authors conclude that artificial neural networks present the best performance, and their analysis identified the state of sand, processing temperature and contact angles as the important predictive parameters. This paper is devoted to an extremely important and actual topic and should inspire other researchers to explore machine learning methods.
In the next contribution, the research team from the Southwest Petroleum University in China describe the preparation of an anticorrosive titanate nanotubes-based polyurethane coating that could be used to protect petrochemical equipment, pipelines, ships and marine facilities, and other industrial equipment.11 The characterization of formulated coatings revealed a good dispersion of titanate nanotubes with surfaces grafted with aminopropyltriethoxysilane. The filler improved water resistance and slowed down decomposition of the polyurethane coating. It also improved corrosion resistance, although the study concentrated on short time effects.
Aluminum alloys are common lightweight metals used in construction, automotive, communication and consumer electronic applications. However, they are not resistant to corrosion and oxidation, which reduce their durability and aesthetic values. Titanium/zirconium-based coatings are among recently considered coatings but unfortunately, they are colourless, making the distinction between uncoated and coated parts practically impossible. In the final contribution to this issue, Liao et al.12 demonstrate that adding tannic acid to hexafluorozirconic acid, hexaflurotitanic acid, and sodium metavanadate during coating produces a palette of yellow to golden color in the coating, depending on the concentration of tannic acid. UV-Vis, IR and XPS analyses revealed that the organic complexes between tannic acid and metal ions during the aging process are responsible for rapid colored film formation. The coatings also demonstrate improved corrosion resistance.
We would appreciate any feedback and valuable suggestions from contributing authors and readers on any developments to the Surface Innovations journal that could make it more appealing to them in the years to come.
