Graph Neural Network-Accelerated Multitasking Genetic Algorithm for Optimizing PdxTi1-xHy Surfaces under Various CO2 Reduction Reaction Conditions

Palladium (Pd) hydride-based catalysts have been reported to have excellent performance in the CO2 reduction reaction (CO2RR) and hydrogen evolution reaction (HER). Our previous work on doped PdH and Pd alloy hydrides showed that Ti-doped and Ti-alloyed Pd hydrides could improve the performance of the CO2 reduction reaction compared with pure Pd hydride. Compositions and chemical orderings of the surfaces with only one adsorbate under certain reaction conditions are linked to their stability, activity, and selectivity toward the CO2RR and HER, as shown in our previous work. In fact, various coverages, types, and mixtures of the adsorbates, as well as state variables such as temperature, pressure, applied potential, and chemical potential, could impact their stability, activity, and selectivity. However, these factors are usually fixed at common values to reduce the complexity of the structures and the complexity of the reaction conditions in most theoretical work. To address the complexities above and the huge search space, we apply a deep learning-assisted multitasking genetic algorithm to screen for PdxTi1-xHy surfaces containing multiple adsorbates for CO2RR under different reaction conditions. The ensemble deep learning model can greatly speed up the structure relaxations and retain a high accuracy and low uncertainty of the energy and forces. The multitasking genetic algorithm simultaneously finds globally stable surface structures under each reaction condition. Finally, 23 stable structures are screened out under different reaction conditions. Among these, Pd0.56Ti0.44H1.06 + 25%CO, Pd0.31Ti0.69H1.25 + 50%CO, Pd0.31Ti0.69H1.25 + 25%CO, and Pd0.88Ti0.12H1.06 + 25%CO are found to be very active for CO2RR and suitable to generate syngas consisting of CO and H2.

Molecular Design for Vertical Phase Distribution Modulation in High-Performance Organic Solar Cells

Component distribution within the photoactive layer dictates the morphology and electronic structure and substantially influences the performance of organic solar cells (OSCs). In this study, a molecular design strategy is introduced to manipulate component and energetics distribution by adjusting side-chain polarity. Two non-fullerene acceptors (NFAs), ITIC-16F and ITIC-E, are synthesized by introducing different polar functional substituents onto the side chains of ITIC. The alterations result in different distribution tendencies in the bulk heterojunction film: ITIC-16F with intensified hydrophobicity aligns predominantly with the top surface, while ITIC-E with strong hydrophilicity gravitates toward the bottom. This divergence directly impacts the vertical distribution of the excitation energy levels, thereby influencing the excitation kinetics over extended time periods and larger spatial ranges including enhanced diffusion-mediated exciton dissociation and stimulated charge carrier transport. Benefitting from the favorable energy distribution, the device incorporating ITIC-E into the PBQx-TF:eC9-2Cl blend showcases an impressive power conversion efficiency of 19.4%. This work highlights side-chain polarity manipulation as a promising strategy for designing efficient NFA molecules and underscores the pivotal role of spatial energetics distribution in OSC performance.

Effect of Industrial Solid Waste as Fillers on the Rheology and Surface Free Energy of Asphalt Mastic

The continuous growth of industrial solid waste production has generated many environmental problems. We evaluated the potential of industrial solid waste as a substitute filler in asphalt mastic, with the aim of increasing the use of sustainable road construction materials. In this study, X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy (SEM) were used to characterize the oxide composition and micromorphology of limestone (LS), red mud (RM), steel slag (SS), and ground granulated blast-furnace slag (GGBFS). Four asphalt mastics containing LS, RM, SS, and GGBFS with a filler-to-binder weight ratio of one were prepared. An evaluation of the rheology and wetting of the solid-waste-filler asphalt mastic was conducted using a frequency sweep, temperature sweep, linear amplitude sweep (LAS), multiple stress creep and recovery (MSCR), and surface free energy (SFE) methods. The results showed that SS increased the complex modulus, elastic component of the asphalt mastic and decreased the nonrecoverable creep compliance at stress levels of 0.1 and 3.2 kPa, which improved the rutting resistance of the asphalt mastic and reduced deformation under high-temperature conditions. The RM and GGBFS increased the fatigue performance of the asphalt mastic under strain loading, enhanced its fatigue life, and maintained good performance under long-term loading. The dispersive component of the SFE parameter of the solid-waste-filler asphalt mastic was larger than the polar component for the largest share of the surface energy composition. The SFE of the asphalt mastic prepared from the industrial solid-waste filler was reduced; however, the difference was insignificant compared to the limestone asphalt mastic. Solid-waste-filler asphalt mastic has performance characteristics, and its actual application can be based on different performance characteristics to select an appropriate solid-waste filler. The results of this study provide new technological solutions for solving the utilization rate of solid waste materials and sustainable road construction in the future.

The Influence of the Chemical Composition of Flax and Hemp Fibers on the Value of Surface Free Energy

The article presents the exploration of flax and hemp fibers' surface free energy depending on the chemical composition of the fiber, which is closely related to the plant variety and the method of extracting the fiber. For this purpose, tests of the surface free energy (SFE), evaluation of the percentage content of individual fiber components and FTIR analyses were conducted. The research was carried out with the use of fibrous materials prepared in three different ways: 1. To analyze the effect of subsequent stages of flax fibers refining process on chemical composition and SFE, 2. to explore the dependence of fiber SFE on hemp variety, the water-retting hemp fibers were used, 3. To evaluate the influence of the retting method of hemp fibers BIAŁOBRZESKIE variety on SFE, the fibers extracted with the use of dew and water retting were used as the research material. The study confirmed that the content of individual components in the fiber influenced its sorption capacity and therefore determined its hydrophilic properties. The values of Pearson's linear correlation coefficients determined in the statistical analysis proved that the surface free energy was strongly correlated with the content of individual components in the fibers. Understanding the wettability characteristics of bast fibers will allow modeling the properties of products made of these fibers and designing surface modification processes in order to obtain specific functionality of textile products, depending on their intended utilization.

Research on the Adhesion Properties of Fast-Melting SBS-Modified Asphalt-Aggregate Based on Surface Free Energy Theory

In order to study the adhesion properties of fast-melting SBS-modified asphalt (SBS-T) at the interface with aggregates, the contact angles of three dosages of SBS-T asphalt with three liquids (distilled water, glycerol, and formamide) were determined by the sessile drop method based on surface free energy theory. The evaluation indexes such as cohesion, asphalt-aggregate adhesion, stripping work and energy ratio of the asphalt were analyzed and the adhesion properties of the asphalt-aggregate system were investigated with the help of micromechanical methods. The results indicate that SBS-T can improve the adhesion properties of the asphalt. Furthermore, as the dosage of the modifier increases, the cohesion work, adhesion work, and energy ratio of the SBS-T asphalt exhibit a similar rise. As the spalling work reduces and the adhesion between asphalt and aggregate improves, it is noteworthy that the SBS-T asphalt-aggregate system exhibits superior adhesion performance compared to the SBS-modified asphalt-aggregate system, despite the same dosage.

Performance matching of common pesticides in banana plantations on the surface of banana leaves at different growth stages

BACKGROUND

The effective deposition of pesticide droplets on a target leaf surface is critical for decreasing pesticide application rates. The wettability between the target leaf surface and the pesticide spray liquid should be investigated in depth, with the aim of enhancing the adhesion of pesticide solutions. The wetting and deposition behavior of pesticides on target leaves depends on the properties of the liquid and the physical and chemical properties of the leaves. The physical and chemical properties of leaves vary with growth stage. This study aims to investigate the wetting behavior of banana leaf surfaces at different stages.

RESULTS

The microstructures and chemical compositions of banana leaf surfaces at different stages were studied using modern methods. The surface structure of banana leaves exhibited a wide variety of characteristics at different growth stages, and the chemical composition changed marginally. The surface free energy (SFE) and polar and non-polar components of banana leaves at different growth stages were measured by examining the contact angles (CA) of different test solutions on the surface of banana leaves. Previous research has suggested that changes in the CA and SFE correlate with changes in leaf surface wettability. In general, the new upper leaves of banana trees are composed of polar components and exhibit hydrophobicity. Non-polar components become dominant as the leaf grows. The back surface of banana leaves was non-polar at all growth stages, with a trend that was opposite to that of the front surface. The critical surface tension of the banana leaf surface at different growth stages ranged from 7.83 to 24.22 mN m-1 , thus falling into the category of a low-energy surface.

CONCLUSION

The surface roughness and chemical characteristics of banana leaves affected the wettability of the leaf surface. Differences in the free energy and the polar and non-polar components of the leaf surface at were seen at different growth stages. This study provides a favorable reference for the rational control of pesticide spraying parameters and the enhancement of wetting and adhesion of the solution on banana leaf surfaces. © 2023 Society of Chemical Industry.

Selected Properties of the Surface Layer of C45 Steel Samples after Slide Burnishing

This paper presents the experimental results of a study investigating the impact of the machining fluid type, the variable factor, used in slide burnishing on 2D and 3D surface roughness; surface topography; Abbott-Firestone curve shape; microhardness; and SFE (surface free energy). In the experiment, pre-ground, ringed samples of C45 steel were used. The results showed an over eight-fold decrease in the value of the Ra (arithmetical mean deviation) parameter and over a five-fold decrease in the Rt (total height of profile) parameter in relation to their values after grinding. The parameters Rpk (reduced peak height), Rk (core roughness depth), and Rvk (reduced valley depth) were also reduced. The Abbott-Firestone curve after slide burnishing changed its angle of inclination (it was more flattened), and the material ratio Smr increased. The reduction in the Rpk and Rk parameters and increased material ratio will most likely contribute to restoring the functionality of these surfaces (increased resistance to abrasive wear). After slide burnishing, the maximum 25% increase in microhardness was obtained compared to the value after grinding, while the layer thickness was 20 μm. The surface energy of elements subjected to slide burnishing using various machining fluids slightly increased, or its value was close to that of the ground surface. The most favourable properties of the surface layer in terms of mating between two elements were obtained for a part that was slide-burnished with a mixture of oil + polymethyl methacrylate (PMM) + molybdenum disulphide (MoS2).

Experimental Study on the Physicochemical Properties of Asphalt Modified by Different Anti-Stripping Agents and Their Moisture Susceptibility with Aggregates

Erosion and the stripping effect of moisture on asphalt mixtures is one of the main reasons for the shortened service life of asphalt pavements. The common mean of preventing asphalt pavements from being damaged by moisture is adding anti-stripping agents (ASAs) to asphalt mixtures. However, the effect regularity and mechanism of anti-stripping agents on the physicochemical properties of asphalt is not exactly defined. This study compared the physical properties of ASA-modified asphalt (AMAs) to determine the optimal dosage and investigated the rheological and adhesion properties. Based on the roller bottle method and water immersion method, the moisture susceptibility of AMAs with three particle sizes was investigated. The results showed that the modification of asphalt using anti-stripping agents was a physical modification. At the optimum dosage of anti-stripping agents (0.3%), the basic physical properties of AMA1 were the most desirable. ASA2 increased the resistance of asphalt for deformation at high temperature by 46%, and AMA3 had the best low-temperature performance. ASAs enhanced the dispersed and polar components in the asphalt binder, improving the adhesion energy of asphalt. AMA3 had the strongest adhesion to the aggregate, with an increase in adhesion work by 2.8 times and a 45% of increase in ER value. This was attributed to ASA3 containing with a large number of metal cations and polar functional groups. It was shown that ASAs provided the most improvement in the anti-stripping performance of asphalt mixtures with 9.5-13.2 mm particles. The amide ASA, phosphate ASA and aliphatic amine ASA improved the water damage resistance of asphalt by 65%, 45% and 78%, respectively. This study can help engineers realize the effects of different types of ASAs on the physicochemical properties of asphalt and select the most suitable type of ASAs according to the service requirements.

Evaluation of Human Gingival Fibroblasts (HGFs) Behavior on Innovative Laser Colored Titanium Surfaces

The use of ytterbium laser to obtain colored titanium surfaces is a suitable strategy to improve the aesthetic soft tissue results and reduce implant failures in oral rehabilitation. To investigate the relationship between novel laser-colored surfaces and peri-implant soft tissues, Human Gingival Fibroblasts (HGFs) were cultured onto 12 colored titanium grade 1 light fuchsia, dark fuchsia, light gold, and dark gold disks and their viability (MTT Assay), cytotoxicity (lactate dehydrogenase release), and collagen I secretion were compared to the machined surface used as control. Optical and electronic microscopies showed a HGF growth directly correlated to the roughness and wettability of the colored surfaces. A higher viability percentage on dark fuchsia (125%) light gold (122%), and dark gold (119%) samples with respect to the machined surface (100%) was recorded. All specimens showed a statistically significant reduction of LDH release compared to the machined surface. Additionally, a higher collagen type I secretion, responsible for an improved adhesion process, in light fuchsia (3.95 μg/mL) and dark gold (3.61 μg/mL) compared to the machined surface (3.59 μg) was recorded. The in vitro results confirmed the innovative physical titanium improvements due to laser treatment and represent interesting perspectives of innovation in order to ameliorate aesthetic dental implant performance and to obtain more predictable osteo and perio-osteointegration long term implant prognosis.

A Comparative Investigation of the Surface Properties of Corn-Starch-Microfibrillated Cellulose Composite Films

Starch-based materials seem to be an excellent alternative for conventional plastics used in various applications. Microfibralted cellulose can be used to improve the surface properties of starch-based materials. This study aims to analyze the surface properties of starch-microfibrillated cellulose materials. The surface properties of films were evaluated by ATR-FTIR, surface roughness, water wettability, and surface free energy. The surface homogeneity between corn starch and microfibrillated cellulose (MFC) fibers was confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Microscopic analyses of the film surfaces confirm good compatibility of starch and MFC. The addition of MFC increased the surface roughness and polarity of developed starch/MFC materials. The surface roughness parameter has increased from 1.44 ± 0.59 to 2.32 ± 1.13 for pure starch-based materials and starch/MFC material with the highest MFC content. The WCA contact angle has decreased from 70.3 ± 2.4 to 39.1 ± 1.0°, while the surface free energy is 46.2 ± 3.4 to 66.2 ± 1.5 mJ·m^-2, respectively. The findings of this study present that surface structure starch/MFC films exhibit homogeneity, which would be helpful in the application of MFC/starch materials for biodegradable packaging purposes.

Influence of the Application Time of Silane for the Bonding Performance between Feldspar or Lithium Disilicate Ceramics and Luting Resin Composites

A correct silanization time is essential for successful surface functionalization and sufficient bonding to dental ceramics. The shear bond strength (SBS) of lithium disilicate (LDS) and feldspar (FSC) ceramics and luting resin composite was investigated with respect to different silanization times, taking into account the physical properties of the individual surfaces. The SBS test was performed with a universal testing machine, and the fracture surfaces were evaluated by stereomicroscopy. The surface roughness of the prepared specimens was analyzed after etching. Changes in surface properties due to surface functionalization were evaluated by surface free energy (SFE) via contact angle measurement. Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical binding. The roughness and SBS of the control group (no silane, etched) were higher for FSC than for LDS. Regarding the SFE, the dispersive fraction increased and the polar fraction decreased after silanization. FTIR confirmed the presence of silane on the surfaces. The SBS of LDS showed a significant increase from 5 to 15 s, depending on the silane and luting resin composite. For FSC, cohesive failure was observed for all samples. For LDS specimens, a silane application time of 15 to 60 s is recommended. Based on clinical conditions, no difference between the silanization times was observed for FSC specimens, indicating that etching alone produces sufficient bonding.

Using Different Surface Energy Models to Assess the Interactions between Antiviral Coating Films and phi6 Model Virus

High molecular weight chitosan (HMWCh), quaternised cellulose nanofibrils (qCNF), and their mixture showed antiviral potential in liquid phase, while this effect decreased when applied to facial masks, as studied in our recent work. To gain more insight into material antiviral activity, spin-coated thin films were prepared from each suspension (HMWCh, qCNF) and their mixture with a 1:1 ratio. To understand their mechanism of action, the interactions between these model films with various polar and nonpolar liquids and bacteriophage phi6 (in liquid phase) as a viral surrogate were studied. Surface free energy (SFE) estimates were used as a tool to evaluate the potential adhesion of different polar liquid phases to these films by contact angle measurements (CA) using the sessile drop method. The Fowkes, Owens-Wendt-Rabel-Kealble (OWRK), Wu, and van Oss-Chaudhury-Good (vOGC) mathematical models were used to estimate surface free energy and its polar and dispersive contributions, as well as the Lewis acid and Lewis base contributions. In addition, the surface tension SFT of liquids was also determined. The adhesion and cohesion forces in wetting processes were also observed. The estimated SFE of spin-coated films varied between mathematical models (26-31 mJ/m²) depending on the polarity of the solvents tested, but the correlation between models clearly indicated a significant dominance of the dispersion components that hinder wettability. The poor wettability was also supported by the fact that the cohesive forces in the liquid phase were stronger than the adhesion to the contact surface. In addition, the dispersive (hydrophobic) component dominated in the phi6 dispersion, and since this was also the case in the spin-coated films, it can be assumed that weak physical van der Waals forces (dispersion forces) and hydrophobic interactions occurred between phi6 and the polysaccharide films, resulting in the virus not being in sufficient contact with the tested material during antiviral testing of the material to be inactivated by the active coatings of the polysaccharides used. Regarding the contact killing mechanism, this is a disadvantage that can be overcome by changing the previous material surface (activation). In this way, HMWCh, qCNF, and their mixture can attach to the material surface with better adhesion, thickness, and different shape and orientation, resulting in a more dominant polar fraction of SFE and thus enabling the interactions within the polar part of phi6 dispersion.

Influence of Surface Structure on Ball Properties during a Professional Water Polo Game

The use of modern materials in sports, in terms of chemical composition and surface texture, entails both progress in results and an increasing discrepancy in the technical parameters of the equipment used. This paper aims to demonstrate the differences between balls admitted to a league and world championships in composition, surface texture, and the influence of these parameters on the water polo game. This research compared two new balls produced by top companies producing sports accessories (Kap 7 and Mikasa). To obtain the goal, the measurement of the contact angle, analysis of the material using Fourier-transform infrared spectroscopy, and optical microscopic evaluation were used. The analysis of the surface free energy shows significant differences (Kap 7 32.16 mJ/m², Mikasa 36.48 mJ/m²). In the case of both balls, anisotropies of the structure of the furrows were observed, however, the Mikasa ball is slightly more homogeneous than the Kap 7 ball. The obtained results from the analysis of the contact angle, as well as the composition and real feedback from the players, indicated the need to standardize the material aspect of the regulations so that the sports results are repeatable every time.

Determination of Hydrophobic Dispersive Surface Free Energy of Activated Carbon Fibers Measured by Inverse Gas Chromatographic Technique

Activated carbon fibers (ACFs) as one of the most important porous carbon materials are widely used in many applications that involve rapid adsorption and low-pressure loss, including air purification, water treatment, and electrochemical applications. For designing such fibers for the adsorption bed in gas and aqueous phases, in-depth comprehension of the surface components is crucial. However, achieving reliable values remains a major challenge due to the high adsorption affinity of ACFs. To overcome this problem, we propose a novel approach to determine London dispersive components (γSL) of the surface free energy of ACFs by inverse gas chromatography (IGC) technique at an infinite dilution. Our data reveal the γSL values at 298 K for bare carbon fibers (CFs) and the ACFs to be 97 and 260-285 mJ·m^-2, respectively, which lie in the regime of secondary bonding of physical adsorption. Our analysis indicates that these are impacted by micropores and defects on the carbon surfaces. Comparing the γSL obtained by the traditional Gray's method, our method is concluded as the most accurate and reliable value for the hydrophobic dispersive surface component of porous carbonaceous materials. As such, it could serve as a valuable tool in designing interface engineering in adsorption-related applications.

Bacterial Adhesion on Dental Polymers as a Function of Manufacturing Techniques

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (R_z; R_a) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = -0.240) and S. mutans (PC = -0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and R_z was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion.

Preparation and Surface Characterization of Chitosan-Based Coatings for PET Materials

Poly(ethylene terephthalate)-PET-is one of the most frequently used polymers in biomedical applications. Due to chemical inertness, PET surface modification is necessary to gain specific properties, making the polymer biocompatible. The aim of this paper is to characterize the multi-component films containing chitosan (Ch), phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), immunosuppressant cyclosporine A (CsA) and/or antioxidant lauryl gallate (LG) which can be utilized as a very attractive material for developing the PET coatings. Chitosan was employed owing to its antibacterial activity and also its ability to promote cell adhesion and proliferation favorable for tissue engineering and regeneration purposes. Moreover, the Ch film can be additionally modified with other substances of biological importance (DOPC, CsA and LG). The layers of varying compositions were prepared using the Langmuir-Blodgett (LB) technique on the air plasma-activated PET support. Then their nanostructure, molecular distribution, surface chemistry and wettability were determined by atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurements and the surface free energy and its components' determination, respectively. The obtained results show clearly the dependence of the surface properties of the films on the molar ratio of components and allow for a better understanding of the coating organization and mechanisms of interactions at the molecular level both inside the films and between the films and the polar/apolar liquids imitating the environment of different properties. The organized layers of this type can be helpful in gaining control over the surface properties of the biomaterial, thus getting rid of the limitations in favor of increased biocompatibility. This is a good basis for further investigations on the correlation of the immune system response to the presence of biomaterial and its physicochemical properties.

Surface Properties of Graffiti Coatings on Sensitive Surfaces Concerning Their Removal with Formulations Based on the Amino-Acid-Type Surfactants

Water-in-oil (w/o) nanoemulsions stabilized with amino acid surfactants (AAS) are one example of nanotechnology detergents of the "brush on, wipe off"-type for removing graffiti coatings from different sensitive surfaces. The high-pressure homogenization (HPH) process was used to obtain the nanostructured fluids (NSFs), including the non-toxic and eco-friendly components such as AAS, esterified vegetable oils, and ethyl lactate. The most effective NSF detergent was determined by response surface methodology (RSM) optimization. Afterwards, several surface properties, i.e., topography, wettability, surface free energy, and the work of water adhesion to surfaces before and after their coverage with the black graffiti paint, as well as after the removal of the paint layers by the eco-remover, were determined. It was found that the removal of graffiti with the use of the NSF detergent is more dependent on the energetic properties and microporous structure of the paint coatings than on the properties of the substrates on which the layers were deposited. The use of NSFs and knowledge of the surface properties could enable the development of versatile detergents that would remove unwanted contamination from various surfaces easily and in a controlled way.

Investigating the Effects of Nitric Acid Treatments on the Properties of Recycled Carbon Fiber

In this study, the chemical state change of recycled carbon fiber (rCF) surfaces and the mechanism of the oxygen functional groups according to nitric acid treatment at various times and temperatures were investigated to upcycle the carbon fiber recovered from used carbon composite. When treated with nitric acid at 25 °C, the carbon fiber surface demonstrated the same tensile properties as untreated carbon fiber (CF) for up to 5 h, and the oxygen functional group and polar surface energy of C-O (hydroxyl group) and C=O (carbonyl group) increased slightly compared to the untreated CF up to 5 h. On the other hand, at 100 °C, the tensile properties slightly decreased compared to untreated CF up to 5 h, and the amount of C-O and C=O decreased and the amount of O=C-O (lactone group) started to increase until 1 h. After 1 h, the amount of C-O and C=O decreased significantly, and the amount of O=C-O increased rapidly. At 5 h, the amount of oxygen functional groups increased by 92%, and the polar surface energy increased by 200% compared to desized CF. It was determined that the interfacial bonding force increased the most because the oxygen functional group, O=C-O, increased greatly at 100 °C and 5 h.

New Prediction Model of Surface and Interfacial Energies Based on COSMO-UCE

The nature and strength of intermolecular and surface forces are the key factors that influence the solvation, adhesion and wetting phenomena. The universal cohesive energy prediction equation based on conductor-like screening model (COSMO-UCE) was extended from like molecules (pure liquids) to unlike molecules (dissimilar liquids). A new molecular-thermodynamic model of interfacial tension (IFT) for liquid-liquid and solid-liquid systems was developed in this work, which can predict the surface free energy of solid materials and interfacial energy directly through cohesive energy calculations based on COSMO-UCE. The applications of this model in prediction of IFT for water-organic, solid (n-hexatriacontane, polytetrafluoroethylene(PTFE) and octadecyl-amine monolayer)-liquid systems have been verified extensively with successful results; which indicates that this is a straightforward and reliable model of surface and interfacial energies through predicting intermolecular interactions based on merely molecular structure (profiles of surface segment charge density), the dimensionless wetting coefficient R_A/C can characterize the wetting behavior (poor adhesive (non-wetting), wetting, spreading) of liquids on the surface of solid materials very well.

Use of Multi-Scale Investigation to Evaluate Adhesion Performance of Warm-Mix Polymer-Modified Asphalt

Warm Mix Asphalt (WMA) technology can effectively reduce carbon emissions and energy consumption during road project construction. However, it may have a negative impact on the binding properties of asphalt mixtures. In order to effectively evaluate the adhesion performance of asphalt binders and aggregates under the combined influence of WMA and traditional polymer-modified asphalt, this paper provides a comprehensive evaluation at the micro and macro levels. The adhesion between three different modified asphalts (warm mix crumb rubber/ Styrene-Butadiene-Styrene (SBS) composite modified asphalt, warm mix crumb rubber asphalt, and warm mix SBS modified asphalt) and two different aggregates (limestone and granite) under both virgin and short-term aging conditions were analyzed. Regardless of the type of modified asphalt, the results showed that limestone aggregates have better adhesion properties with asphalt binders. In addition, the short-term thermal oxidation aging behavior is conducive to enhancing the asphalt-aggregate adhesion characteristics. Furthermore, WMA additives, crumb rubber, and SBS compound modification can improve the adhesion performance between asphalt and aggregate.

Estimation of the work of adhesion between ITO and polymer substrates: a surface thermodynamics approach

Indium tin oxide (ITO) is one of the most widely used semiconductor among transparent conducting oxides (TCOs) due to their electrical conductivity and optical transparency properties. Since the development of low temperature deposition methods, coating of ITO on polymer substrates especially for use in flexible electronics has been a popular topic. The existence of adequate adhesion strength between ITO and polymer is critical in producing a successful film. Nowadays, polycarbonate (PC), poly(methyl methacrylate) (PMMA) and polyethyleneterephtalate (PET) are frequently used as substrates for such coatings. However, there may be other polymeric alternatives that have a potential to be used for this purpose in the future. To evaluate these alternatives, work of adhesion (Wa) knowledge between ITO and polymers is necessary, and it has not been handled systematically previously. In this study, the interphase interaction parameters and Wa values between ITO and various polymers were calculated based on the Dupré, Fowkes and Girifalco-Good equations. PC, PMMA, PET, polystyrene (PS), polyphenylene sulfide (PPS), Nylon 66, polypropylene (PP), polyvinylchloride (PVC), styrene-butadiene rubber (SBR), high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl acetate (PVAc), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polytrifluoroethylene (PTrFE) and polyperfluoroalkylethyl acrylate (PPFA) were considered as substrate material. Surface free energy (SFE) components calculated by acid-base, geometric mean and harmonic mean approaches for polymeric substrates were used during the calculations. In the present study, the polymers that can be used as substrates were evaluated in terms of adhesion ability to ITO, the significance of calculation methods on Wa values were also investigated simultaneously. It was determined that the Wa between ITO and polymer substrates was directly related with the total SFE value of the polymers.

Development of Water Repellent, Non-Friable Tannin-Furanic-Fatty Acids Biofoams

Tannin-furanic foams were prepared with a good yield using the addition of relatively small proportions of a polyflavonoid tannin extract esterified with either palmitic acid, oleic acid, or lauric acid by its reaction with palmitoyl chloride, oleyl chloride, or lauryl chloride. FTIR analysis allowed us to ascertain the esterification of the tannin, and MALDI-TOF analysis allowed us to identify a number of multi-esterified flavonoid oligomers as well as some linked to residual carbohydrates related to the equally esterified tannin. These foams presented a markedly decreased surface friability or no friability at all, and at densities lower than the standard foam they were compared to. Equally, these experimental foams presented a much-improved water repellence, as indicated by their initial wetting angle, its small variation over time, and its stabilization at a high wetting angle value, while the wetting angle of the standard foam control went to zero very rapidly. This conclusion was supported by the calculation of the total surface energy of their surfaces as well as of their dispersive and polar components.

Influence of Anodizing Parameters on Tribological Properties and Wettability of Al2O3 Layers Produced on the EN AW-5251 Aluminum Alloy

The article presents the effect of anodizing parameters of the EN AW-5251 aluminum alloy on the thickness and roughness of Al₂O₃ layers as well as their wettability and tribological properties in a sliding combination with the T7W material. The input variables were the current density of 1, 2, 3 A/dm² and the electrolyte temperature of 283, 293, 303 K. The tribological tests were performed on the T-17 tester in reciprocating motion, in conditions of technically dry friction. The tests were carried out on a 15 km road with a constant average slip speed of 0.2 m/s and a constant unit pressure of 1 MPa. The measurement of the wettability of the layers was performed using the sitting drop method, determining the contact angles on the basis of which the surface free energy was calculated. The profilographometric measurements were made. The analysis of the test results showed that the anodizing parameters significantly affect the thickness of the Al₂O₃ layers. The performed correlation analysis also showed a significant relationship between the roughness parameters and the wettability of the surface of the layers, which affects the ability to create and maintain a sliding film, which in turn translates into sliding resistance and wear of the T7W material. The analysis of friction and wear tests showed that the layer with hydrophobic properties produced at a current density of 1 A/dm² in an electrolyte at a temperature of 283 K is the most favorable for sliding associations with T7W material.

Nature-Inspired High Temperature Scale-Resistant Slippery Lubricant-Induced Porous Surfaces (HTS-SLIPS)

Scale formation is a longstanding and unresolved problem in a number of fields, including power production, petroleum exploration, thermal desalination, and construction. Herein, a high-temperature scale-resistant slippery lubricant-induced surface (HTS-SLIPS) is developed by one-step electrodeposition and lubricant infusion. The fractal cauliflower-like morphology with lubricant oil is conducive to forming an ultralow contact angle hysteresis of ≈1°. The 10-d real-world boiling trial indicates that by replacing the uncoated surface with HTS-SLIPS, the reduction in scale mass is greater than 200% because of the low surface free energy (4.3 mJ m^-2 ) and outstanding smoothness (R_a  = 41 ± 8 nm) of HTS-SLIPS. Thanks to the scale retardation, the bubble departure frequency of HTS-SLIPS is eightfold higher than that of uncoated surfaces, signifying superior heat transfer efficiency. In these demonstrations, HTS-SLIPS coated spiral tube exhibits better flowability and lower pressure drop than the uncoated one. In addition, favorable compatibility between HTS-SLIPS and mechanical vibration is experimentally verified to strengthen the descaling of SLIPS synergistically. It is anticipated that the simple and scalable coating fabrication approach will be applicable in numerous industrial high-temperature processes where scale formation is encountered.

Attachment Performance of Stick Insects (Phasmatodea) on Plant Leaves with Different Surface Characteristics

Herbivorous insects and plants exemplify a longstanding antagonistic coevolution, resulting in the development of a variety of adaptations on both sides. Some plant surfaces evolved features that negatively influence the performance of the attachment systems of insects, which adapted accordingly as a response. Stick insects (Phasmatodea) have a well-adapted attachment system with paired claws, pretarsal arolium and tarsal euplantulae. We measured the attachment ability of Medauroidea extradentata with smooth surface on the euplantulae and Sungaya inexpectata with nubby microstructures of the euplantulae on different plant substrates, and their pull-off and traction forces were determined. These species represent the two most common euplantulae microstructures, which are also the main difference between their respective attachment systems. The measurements were performed on selected plant leaves with different properties (smooth, trichome-covered, hydrophilic and covered with crystalline waxes) representing different types among the high diversity of plant surfaces. Wax-crystal-covered substrates with fine roughness revealed the lowest, whereas strongly structured substrates showed the highest attachment ability of the Phasmatodea species studied. Removal of the claws caused lower attachment due to loss of mechanical interlocking. Interestingly, the two species showed significant differences without claws on wax-crystal-covered leaves, where the individuals with nubby euplantulae revealed stronger attachment. Long-lasting effects of the leaves on the attachment ability were briefly investigated, but not confirmed.

Surface Characterization as a Tool for Identifying the Factors Affecting the Dissolution Rate of Amorphous Solid Dispersion Tablets

An amorphous solid dispersion (ASD) is a commonly used approach to enhancing the dissolution of poorly aqueous soluble drugs. Selecting the desired polymer and drug loading can be time-consuming. Surface properties, such as surface composition and wetting behavior, are essential factors controlling the dissolution of ASD tablets. Thus, our study aims to use surface characterization to understand the factors that affect the dissolution rate of ASD tablets. In this work, we prepared ASDs with itraconazole and hypromellose acetate succinate (HPMCAS) using spray drying. ASDs were prepared using three grades of HPMCAS and different drug loading levels (10%, 30%, and 50%). We prepared ASD tablets with two porosities. For each tablet, contact angles were measured using the Drop Shape Analyzer; surface free energies, disperse, and polar fractions were calculated based on the contact angles. We conducted near-infrared (NIR) and dissolution measurements of ASD tablets. Principal component analysis (PCA) was carried out to investigate the NIR spectra further. The relative PCA scores were reported with other sample properties. A partial least square (PLS) model using NIR scores, tablets' wetting properties, and dissolution rates revealed that water and buffer contact angles, surface free energy, and polar fraction are the most significant factors attributing to the dissolution rate of ASD tablets. This work understood the interplay between the surface properties and the dissolution rate of ASD tablets. Moreover, surface characterization can be the tool to screen the formulation and compaction process of ASD tablets in early development.

Quantitative Analysis of Adhesion Characteristics between Crumb Rubber Modified Asphalt and Aggregate Using Surface Free Energy Theory

The utilization of waste rubber tires is of great value for environment protection and resource recovery, which can also improve the properties of matrix asphalt. The adhesion characteristics were evaluated for crumb rubber modified asphalt and limestone aggregate using the surface free energy (SFE) approach. Four types of matrix asphalt and four rubber contents were used to prepare the crumb rubber modified asphalt. The contact angle of matrix and crumb rubber modified asphalt was obtained, and the SFE indicators (dispersion, polar component, and compatibility rate-CR) were calculated. Moreover, the water stability tests were conducted using one matrix and rubber modified asphalt in order to investigate the relationship between SFE and water stability indicators. Results showed that the total SFE, dispersion component, adhesion work, and CR increased with the addition of crumb rubber, while the polar component and spalling work decreased. The types of asphalt had different influences on SFE indicators. The results from analysis of variation (ANOVA) indicated asphalt type and rubber content had significant influence on the adhesion work, spalling work and CR, and the influence of asphalt type was greater than that of rubber content. Additionally, the retained Marshall Stability and tensile strength ratio had better correlation with adhesion work and CR, but less with spalling work. The presented results demonstrated that the type of matrix asphalt played an important role in the adhesion characteristics for the crumb rubber modified asphalt.

New Segmented Poly(Thiourethane-Urethane)s Based on Poly(ε-Caprolactone)Diol Soft Segment: Synthesis and Characterization

New segmented poly(thiourethane-urethane)s (SPTURs) were synthesized by the reaction of 1,1′-methanediylbis (4-isocyanatocyclohexane) (Desmodur W^®, HMDI) and poly(ε-caprolactone)diol (PCL) and (methanediyldibenzene-4,1-diyl)dimethanethiol as nonconventional polymer chain extender. FTIR spectroscopy was used for the structural analysis of obtained polymers. The molecular weight distribution was examined by GPC chromatography. Based on the measured contact angles, free surface energy parameters were calculated. Thermal properties of polymers were examined by DSC and TGA, while viscoelastic properties were measured by DMTA. The tensile, adhesive and optical properties were also investigated for the obtained polymers. It was shown that SPTURs were transparent or partially transparent solids with high molar masses up to 84,300 Da. These polymers showed a good resistance to hydrolysis during incubation in Optylite^® physiological saline over 8 weeks. Obtained polymers possessed a tensile strength of up to 43.26 MPa, hardness of up to 96.25/59.00 Sh A/D and adhesion to copper of 14.66 MPa. The surface properties of the obtained polymers show that all obtained SPTURs were hydrophilic (CAs for water between 64.07° and 73.12°) with calculated SFE up to 46.69 mN/m.

Effects of Heat Treatment Atmosphere and Temperature on the Properties of Carbon Fibers

In this study, carbon fibers were heat-treated in a nitrogen and oxygen atmosphere according to temperature to elucidate the mechanism of chemical state changes and oxygen functional group changes on the carbon fiber surface by analyzing the mechanical and chemical properties of carbon fibers. Carbon fibers before and after heat treatment were analyzed using FE-SEM (Field Emission Scanning), UTM (Universal Tensile Testers), XPS (X-ray Photoelectron Spectroscopy), and surface-free energy. In the nitrogen atmosphere, which is an inert gas, the tensile strength was equivalent to that of the virgin up to 500 °C but decreased to 71% with respect to the virgin at 1000 °C. Furthermore, as the temperature increased from room temperature to 1000 °C, the oxygen functional group and the polar free energy gradually decreased compared with the virgin. On the other hand, in the oxygen atmosphere, which is an active gas, the tensile properties were not significantly different from those of the virgin up to 300 °C but gradually decreased at 500 °C. Above 600 °C, the carbon fibers deteriorated, and measurement was impossible. The oxygen functional group decreased at 300 °C, but above 300 °C, among the oxygen functional groups, the hydroxyl group and the carbonyl group increased. Furthermore, the lactone group formed and rapidly increased compared with the virgin, and the polar free energy increased as the temperature increased.

Effect of the Composition of Copolymers Based on Glycidyl Methacrylate and Fluoroalkyl Methacrylates on the Free Energy and Lyophilic Properties of the Modified Surface

This study proposes to use reactive copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates with a low fluorine content in the monomer unit as agents to reduce the surface free energy (SFE). This work reveals the effect of the structure and composition of copolymers on the SFE and water-repellent properties of these coatings. On a smooth surface, coatings based on copolymers of glycidyl methacrylate and fluoroalkyl methacrylates with fluorine atoms in the monomer unit ranging from three to seven are characterized by SFE values in the range from 25 to 13 mN/m, which is comparable to the values for polyhedral oligomeric silsesquioxanes and perfluoroalkyl acrylates. On textured aluminum surfaces, the obtained coatings provide time-stable superhydrophobic properties with contact angles up to 170° and sliding angles up to 2°. The possibility of using copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates for the creation of self-cleaning polymer coatings is shown.

Silver Nanowires and Silanes in Hybrid Functionalization of Aramid Fabrics

New functionalization methods of meta- and para-aramid fabrics with silver nanowires (AgNWs) and two silanes (3-aminopropyltriethoxysilane (APTES)) and diethoxydimethylsilane (DEDMS) were developed: a one-step method (mixture) with AgNWs dispersed in the silane mixture and a two-step method (layer-by-layer) in which the silanes mixture was applied to the previously deposited AgNWs layer. The fabrics were pre-treated in a low-pressure air radio frequency (RF) plasma and subsequently coated with polydopamine. The modified fabrics acquired hydrophobic properties (contact angle Θ_W of 112-125°). The surface free energy for both modified fabrics was approximately 29 mJ/m², while for reference, meta- and para-aramid fabrics have a free energy of 53 mJ/m² and 40 mJ/m², respectively. The electrical surface resistance (R_s) was on the order of 10² Ω and 10⁴ Ω for the two-step and one-step method, respectively. The electrical volume resistance (R_v) for both modified fabrics was on the order of 10² Ω. After UV irradiation, the Rs did not change for the two-step method, and for the one-step method, it increased to the order of 10¹⁰ Ω. The specific strength values were higher by 71% and 63% for the meta-aramid fabric and by 102% and 110% for the para-aramid fabric for the two-step and one-step method, respectively, compared to the unmodified fabrics after UV radiation.

Improving Surface Functionality, Hydrophilicity, and Interfacial Adhesion Properties of High-Density Polyethylene with Activated Peroxides

Polyolefins have had limited application in advanced technologies due to their low surface energy, hydrophobicity, and weak interfacial adhesion with polar coatings. Herein, we propose the use of transition metals at their lowest oxidation state and inorganic peroxides to improve the functionality, surface free energy, hydrophilicity, and adhesion properties of high-density polyethylene (HDPE). Among the nine combinations of transition metals and peroxides used in this study, the combination of Co(II) and peroxymonosulfate (PMS) peroxide was the most effective for surface modification of HDPE, followed closely by the combination of Ru(III) and PMS. After chemical treatment, HDPE's surface functionality, composition, and energy were analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Hydroxyl, carbonyl, and carboxylic acid functional groups were detected on the surface, which explained the improved hydrophilicity of the modified HDPE surface; the contact angle of HDPE with DI water decreased from 94.31 to 51.95° after surface treatment. To investigate the effect of HDPE's surface functionality on its interfacial properties, its adhesion to a commercial epoxy coating was measured via pull-off strength test according to ASTM D54541. After only 20 min of surface treatment with Co(II)/PMS solution, the adhesion strength at the interface of HDPE and the epoxy coating increased by 193%, confirming the importance of polyolefins' surface functionality on their interfacial adhesion properties. The method outlined herein can improve HDPE's surface functionality by introducing sulfate radicals. It improves HDPE's hydrophilicity and adhesion properties without requiring strong acids or time-consuming pre- or post-treatment processes. This process has the potential to increase the use of polyolefins in various industries, such as for protective coatings, high performance lithium-ion battery separators, and acoustic sensors.

A Nanoindentation Approach for Time-Dependent Evaluation of Surface Free Energy in Micro- and Nano-Structured Titanium

Surface free energy (SFE) of titanium surfaces plays a significant role in tissue engineering, as it affects the effectiveness and long-term stability of both active coatings and functionalization and the establishment of strong bonds to the newly growing bone. A new contact–mechanics methodology based on high-resolution non-destructive elastic contacting nanoindentation is applied here to study SFE of micro- and nano-structured titanium surfaces, right after their preparation and as a function of exposure to air. The effectiveness of different surface treatments in enhancing SFE is assessed. A time-dependent decay of SFE within a few hours is observed, with kinetics related to the sample preparation. The fast, non-destructive method adopted allowed for SFE measurements in very hydrophilic conditions, establishing a reliable comparison between surfaces with different properties.

Investigations on the Influence of Collagen Type on Physicochemical Properties of PVP/PVA Composites Enriched with Hydroxyapatite Developed for Biomedical Applications

Nowadays, a great attention is directed into development of innovative multifunctional composites which may support bone tissue regeneration. This may be achieved by combining collagen and hydroxyapatite showing bioactivity, osteoconductivity and osteoinductivity with such biocompatible polymers as polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA). Here PVA/PVP-based composites modified with hydroxyapatite (HAp, 10 wt.%) and collagen (30 wt.%) were obtained via UV radiation while two types of collagen were used (fish and bovine) and crosslinking agents differing in the average molecular weight. Next, their chemical structure was characterized using Fourier transform infrared (FT-IR) spectroscopy, roughness of their surfaces was determined using a stylus contact profilometer while their wettability was evaluated by a sessile drop method followed by the measurements of their surface free energy. Subsequently, swelling properties of composites were verified in simulated physiological liquids as well as the behavior of composites in these liquids by pH measurements. It was proved that collagen-modified composites showed higher swelling ability (even 25% more) compared to unmodified ones, surface roughness, biocompatibility towards simulated physiological liquids and hydrophilicity (contact angles lower than 90°). Considering physicochemical properties of developed materials and a possibility of the preparation of their various shapes and sizes, it may be concluded that developed materials showed great application potential for biomedical use, e.g., as materials filling bone defects supporting their treatments and promoting bone tissue regeneration due to the presence of hydroxyapatite with osteoinductive and osteoconductive properties.

Surface Electric Fields Increase Human Osteoclast Resorption through Improved Wettability on Carbonate-Incorporated Apatite

Osteoclast-mediated bioresorption can be an efficient means of incorporating the dissolution of biomaterials in the bone remodeling process. Because of the compositionally and structurally close resemblance of biomaterials with the natural mineral phases of the bone matrix, synthetic carbonate-substituted apatite (CA) is considered as an ideal biomaterial for clinical use. The present study therefore investigated the effects of electrical polarization on the surface characteristics and interactions with human osteoclasts of hydroxyapatite (HA) and CA. Electrical polarization was found to improve the surface wettability of these materials by increasing the surface free energy, and this effect was maintained for 1 month. Analyses of human osteoclast cultures established that CA subjected to a polarization treatment enhanced osteoclast resorption but did not affect the early differentiation phase or the adherent morphology of the osteoclasts as evaluated by staining. These data suggest that the surface characteristics of the CA promoted osteoclast resorption. The results of this work are expected to contribute to the future design of cell-mediated bioresorbable biomaterials capable of resorption by osteoclasts and of serving as a scaffold for bone regeneration.

A Method for Measuring the Surface Free Energy of Topical Semi-solid Dosage Forms

Our aim was to determine the surface free energy (SFE) of semi-solid dosage forms (SSDFs) by establishing a reproducible method for measuring the contact angle of liquids to SSDFs. Four SSDFs were used: petrolatum, an oil/water (O/W) and a water/oil (W/O) cream, and an alcohol-based gel. The SSDFs were evenly spread on a glass slide, and the change in contact angle over time was measured by dropping water, glycerol, diiodomethane and n-hexadecane as the test liquids. Depending on the combination of test liquid and SSDF, the contact angle was either constant or decreased in an exponential manner. Contact angles may have decreased in an exponential manner because the reaction between the test liquid and the SSDF altered the interfacial tension between the two phases and changed the surface tension of the test liquid and the SFE of the SSDF. The contact angle of the test liquid to the SSDF could be determined reproducibly using the initial contact angle immediately after dropping the liquid on the SSDF as the contact angle before reaction. Using the obtained contact angles and the Owens-Wendt-Rabel-Kaelble equation, we calculated the SFE and its component for the SSDFs tested and found that the results reflect the physicochemical properties of SSDFs. Furthermore, the work of adhesion (W_A) of the SSDF to Yucatan micropig skin was calculated using the SFE for the SSDFs. Interestingly, the W_A values for all SSDFs tested were comparable.

Plasma Modification of Carbon Coating Produced by RF CVD on Oxidized NiTi Shape Memory Alloy under Glow-Discharge Conditions

Our previous work has shown that for cardiac applications, combining low-temperature plasma oxidation with an amorphous carbon coating (a-C:N:H type) constitutes a prospective solution. In this study, a short-term modification by low-temperature oxygen plasma is proposed as an example and a method for shaping the topography and surface energy of the outer amorphous carbon coating, produced via the Radio-Frequency Chemical Vapour Deposition (RFCVD) method on NiTi alloy oxidized under glow-discharge conditions. This treatment alters the chemical composition of the outer zone of the surface layer. A slight increase is also noted in the surface roughness at the nanoscale. The contact angles were shown to increase by about 20% for water and 30% for diiodomethane, while the surface free energy decreased by ca. 11%. The obtained results indicate that even short-term contact with low-temperature plasma can shape the surface properties of the carbon coating, an outcome which shows potential in terms of its use in medical applications.

Visualization of Activated Area on Polymers for Evaluation of Atmospheric Pressure Plasma Jets

The treatment of a polymer surface using an atmospheric pressure plasma jet (APPJ) causes a local increase of the surface free energy (SFE). The plasma-treated zone can be visualized with the use of a test ink and quantitatively evaluated. However, the inked area is shrinking with time. The shrinkage characteristics are collected using activation image recording (AIR). The recording is conducted by a digital camera. The physical mechanisms of activation area shrinkage are discussed. The error sources are analyzed and methods of error reduction are proposed. The standard deviation of the activation area is less than 3%. Three polymers, acrylonitrile butadiene styrene (ABS), high-density polyethylene (HDPE), and polyoxymethylene (POM), are examined as a test substrate material. Due to a wide variation range of SFE and a small hydrophobic recovery, HDPE is chosen. Since the chemical mixtures tend to temporal changes of the stoichiometry, the pure formamide test ink with 58 mN/m is selected. The method is tested for the characterization of five different types of discharge: (i) pulsed arc APPJ with the power of about 700 W; (ii) piezoelectric direct discharge APPJ; (iii) piezoelectric driven needle corona in ambient air; (iv) piezoelectric driven plasma needle in argon; and (v) piezoelectric driven dielectric barrier discharge (DBD). For piezoelectrically driven discharges, the power was either 4.5 W or 8 W. It is shown how the AIR method can be used to solve different engineering problems.

Evaluation of Dihedral Angle Twin Boundaries in Cu10 wt%Zn Alloy Using Atomic Force Microscopy

Atomic force microscopy (AFM) measurements of dihedral angles are conducted for the first time to characterize the ratio of the twin-boundary energy (γΤ) to the surface free energy (γS). In plane, twin morphology is measured with AFM, verified by scanning electron microscopy, optical microscopy, and found to be consistent. The chemical composition and homogeneity of annealed Cu10 wt%Zn sample are confirmed by energy-dispersive spectroscopy. AFM data indicate that the average depth and height of the grooves and peaks are 118 ± 45 and 158 ± 45 nm, respectively. Surface roughness parameters, Sq and Sa, are measured by a factor of two to four less than the depth and height of the twin boundaries. Both surface roughness parameters are less with no planar defects present compared with selected areas containing twin boundaries. The average dihedral angle is found to be 167 ± 5° for the grooves and 193 ± 4° for the peaks. The twin to surface interfacial free energy ratio, γT/γS, is 0.0018. The comparison of AFM-based results to the other method-based results obtained on pure metals is discussed.

Surface topography and free energy regulate osteogenesis of stem cells: effects of shape-controlled gold nanoparticles

The surface free energy of a biomaterial plays an important role in the early stages of cell-biomaterial interactions, profoundly influencing protein adsorption, interfacial water accessibility, and cell attachment on the biomaterial surface. Although multiple approaches have been developed to engineer the surface free energy of biomaterials, systematically tuning their surface free energy without altering other physicochemical properties remains challenging. In this study, we constructed an array of chemically-equivalent surfaces with comparable apparent roughness through assembly of gold nanoparticles adopting various geometrically-distinct shapes but all capped with the same surface ligand, (1-hexadecyl)trimethylammonium chloride, on cell culture substrates. We found that bone marrow stem cells exhibited distinct osteogenic differentiation behaviours when interacting with different types of substrates comprising shape-controlled gold nanoparticles. Our results reveal that bone marrow stem cells are capable of sensing differences in the nanoscale topographical features, which underscores the role of the surface free energy of nanostructured biomaterials in regulating cell responses. The study was approved by Institutional Animal Care and Use Committee, School of Medicine, University of South Carolina.

Chemical Modification as a Method of Improving Biocompatibility of Carbon Nonwovens

It was shown that carbon nonwoven fabrics obtained from polyacrylonitrile fibers (PAN) by thermal conversion may be modified on the surface in order to improve their biological compatibility and cellular response, which is particularly important in the regeneration of bone or cartilage tissue. Surface functionalization of carbon nonwovens containing C–C double bonds was carried out using in situ generated diazonium salts derived from aromatic amines containing both electron-acceptor and electron-donor substituents. It was shown that the modification method characteristic for materials containing aromatic structures may be successfully applied to the functionalization of carbon materials. The effectiveness of the surface modification of carbon nonwoven fabrics was confirmed by the FTIR method using an ATR device. The proposed approach allows the incorporation of various functional groups on the nonwovens’ surface, which affects the morphology of fibers as well as their physicochemical properties (wettability). The introduction of a carboxyl group on the surface of nonwoven fabrics, in a reaction with 4-aminobenzoic acid, became a starting point for further modifications necessary for the attachment of RGD-type peptides facilitating cell adhesion to the surface of materials. The surface modification reduced the wettability (θ) of the carbon nonwoven by about 50%. The surface free energy (SFE) in the chemically modified and reference nonwovens remained similar, with the surface modification causing an increase in the polar component (ɣ_p). The modification of the fiber surface was heterogeneous in nature; however, it provided an attractive site of cell–materials interaction by contacting them to the fiber surface, which supports the adhesion process.

Curcuminoid-Tailored Interfacial Free Energy of Hydrophobic Fibers for Enhanced Biological Properties

The ability of mimicking the extracellular matrix architecture has gained electrospun scaffolds a prominent space into the tissue engineering field. The high surface-to-volume aspect ratio of nanofibers increases their bioactivity while enhancing the bonding strength with the host tissue. Over the years, numerous polyesters, such as poly(lactic acid) (PLA), have been consolidated as excellent matrices for biomedical applications. However, this class of polymers usually has a high hydrophobic character, which limits cell attachment and proliferation, and therefore decreases biological interactions. In this way, functionalization of polyester-based materials is often performed in order to modify their interfacial free energy and achieve more hydrophilic surfaces. Herein, we report the preparation, characterization, and in vitro assessment of electrospun PLA fibers with low contents (0.1 wt %) of different curcuminoids featuring π-conjugated systems, and a central β-diketone unit, including curcumin itself. We evaluated the potential of these materials for photochemical and biomedical purposes. For this, we investigated their optical properties, water contact angle, and surface features while assessing their in vitro behavior using SH-SY5Y cells. Our results demonstrate the successful generation of homogeneous and defect-free fluorescent fibers, which are noncytotoxic, exhibit enhanced hydrophilicity, and as such greater cell adhesion and proliferation toward neuroblastoma cells. The unexpected tailoring of the scaffolds' interfacial free energy has been associated with the strong interactions between the PLA hydrophobic sites and the nonpolar groups from curcuminoids, which indicate its role for releasing hydrophilic sites from both parts. This investigation reveals a straightforward approach to produce photoluminescent 3D-scaffolds with enhanced biological properties by using a polymer that is essentially hydrophobic combined with the low contents of photoactive and multifunctional curcuminoids.

Facile Exfoliation for High-Quality Molybdenum Disulfide Nanoflakes and Relevant Field-Effect Transistors Developed With Thermal Treatment

Molybdenum disulfide (MoS₂), a typical member of the transition metal dichalcogenides (TMDs) group, is known for its excellent electronic performance and is considered a candidate next-generation semiconductor. The preparation of MoS₂ nanoflakes for use as the core of semiconducting devices depends on mechanical exfoliation, but its quality has not yet been optimized. In this paper, a novel exfoliation method of achieving MoS₂ nanoflakes is proposed. We find that the size and yield of the exfoliated flakes are improved after thermal treatment for 2 h at a temperature of 110°C followed by precooling for 10 min in ambient air. The new method has the advantage of a 152-fold larger size of obtained MoS₂ flakes than traditional mechanical exfoliation. This phenomenon may be attributable to the differences in van Der Waals force and the increase in surface free energy at the interface induced by thermal treatment. In addition, a field-effect transistor (FET) was fabricated on the basis of multilayer MoS₂ prepared according to a new process, and the device exhibited a typical depleted-FET performance, with an on/off ratio of ~10⁵ and a field-effect mobility of 24.26 cm²/Vs in the saturated region when V_G is 10 V, which is generally consistent with the values for devices reported previously. This implies that the new process may have potential for the standard preparation of MoS₂ and even other 2D materials as well.

Capillary equilibrium of bubbles in porous media

In geologic, biologic, and engineering porous media, bubbles (or droplets, ganglia) emerge in the aftermath of flow, phase change, or chemical reactions, where capillary equilibrium of bubbles significantly impacts the hydraulic, transport, and reactive processes. There has previously been great progress in general understanding of capillarity in porous media, but specific investigation into bubbles is lacking. Here, we propose a conceptual model of a bubble's capillary equilibrium associated with free energy inside a porous medium. We quantify the multistability and hysteretic behaviors of a bubble induced by multiple state variables and study the impacts of pore geometry and wettability. Surprisingly, our model provides a compact explanation of counterintuitive observations that bubble populations within porous media can be thermodynamically stable despite their large specific area by analyzing the relationship between free energy and bubble volume. This work provides a perspective for understanding dispersed fluids in porous media that is relevant to CO₂ sequestration, petroleum recovery, and fuel cells, among other applications.

Dependence of the Growth Mode in Epitaxial FePt Films on Surface Free Energy

Epitaxial thin films of L1₀-ordered FePt alloys are one of the most important materials in magnetic recording and spintronics applications due to their large perpendicular magnetic anisotropy (PMA). The key to the production of these required superior properties lies in the control of the growth mode of the films. Further, it is necessary to distinguish between the effect of lattice mismatch and surface free energy on the growth mode because of their strong correlation. In this study, the effect of surface free energy on the growth mode of FePt epitaxial films was investigated using MgO, NiO, and MgON surfaces with almost the same lattice constant to exclude the effect of lattice mismatch. It was found that the growth mode can be tuned from a three-dimensional (3D) island mode on MgO to a more two-dimensional (2D)-like mode on MgON and NiO. Contact angle measurements revealed that MgON and NiO show larger surface free energy than MgO, indicating that the difference in the growth mode is due to their larger surface free energy. In addition, MgON was found to induce not only a flat surface as FePt grown on SrTiO₃ (STO), which has a small lattice mismatch, but also a larger PMA than that of STO/FePt. As larger lattice mismatch is favored to induce a higher PMA into the FePt films, MgO substrates are exclusively used, but 3D island growth is indispensable. This work demonstrates that tuning the surface free energy enables us to achieve a large PMA and flat film surface in FePt epitaxial films on MgO. The results also indicate that modifying the surface free energy is pertinent for the flexible functional design of thin films.

The Influence of Starch Origin on the Properties of Starch Films: Packaging Performance

Starch films can be used as materials for food packaging purposes. The goal of this study is to compare how the starch origin influence the selected starch film properties. The films were made from various starches such as that from maize, potato, oat, rice, and tapioca using 50%_w of glycerine as a plasticizer. The obtained starch-based films were made using the well-known casting method from a starch solution in water. The properties of the films that were evaluated were tensile strength, water vapour transition rate, moisture content, wettability, and their surface free energy. Surface free energy (SFE) and its polar and dispersive components were calculated using the Owens-Wendt-Rabel-Kaelbe approach. The values of SFE in the range of 51.64 to 70.81 mJ∙m⁻² for the oat starch-based film and the maize starch-based film. The films revealed worse mechanical properties than those of conventional plastics for packaging purposes. The results indicated that the poorest tensile strength was exhibited by the starch-based films made from oat (0.36 MPa) and tapioca (0.78 MPa) and the greatest tensile strength (1.49 MPa) from potato.

Metal-Insulator Transition of Ultrathin Sputtered Metals on Phenolic Resin Thin Films: Growth Morphology and Relations to Surface Free Energy and Reactivity

Nanostructured metal assemblies on thin and ultrathin polymeric films enable state of the art technologies and have further potential in diverse fields. Rational design of the structure–function relationship is of critical importance but aggravated by the scarcity of systematic studies. Here, we studied the influence of the interplay between metal and polymer surface free energy and reactivity on the evolution of electric conductivity and the resulting morphologies. In situ resistance measurements during sputter deposition of Ag, Au, Cu and Ni films on ultrathin reticulated polymer films collectively reveal metal–insulator transitions characteristic for Volmer–Weber growth. The different onsets of percolation correlate with interfacial energy and energy of adhesion weakly but as expected from ordinary wetting theory. A more pronounced trend of lower percolation thickness for more reactive metals falls in line with reported correlations. Ex situ grazing incidence small angle X-ray scattering experiments were performed at various thicknesses to gain an insight into cluster and film morphology evolution. A novel approach to interpret the scattering data is used where simulated pair distance distributions of arbitrary shapes and arrangements can be fitted to experiments. Detailed approximations of cluster structures could be inferred and are discussed in view of the established parameters describing film growth behavior.

Physico-Mechanical and Rheological Properties of Epoxy Adhesives Modified by Microsilica and Sonication Process

Industrial waste from the production of metallic silicon and silicon–iron alloys, which includes silica fumes (microsilica), is subject to numerous applications aiming at its reuse in concrete and polymeric composites. Recycling solves the problem of their storage and adverse environmental impact. Six different formulas of epoxy resins were tested, differing in the type of polymer, the mixing process (sonication or not) and the presence of microsilica. The study showed that microsilica added to the epoxy resin changes its viscosity and free surface energy, and these are the parameters that determine the adhesion of the polymer to the concrete surface. Strength tests and SEM analysis have determined how microsilica molecules can penetrate the structure of polymer macromolecules by filling and forming temporary chemical bonds. Mixing the fillers with the adhesive was achieved by using a sonication process. The analysis of the obtained results showed that, depending on the initial composition of the polymer, the addition of microsilica can change the chemical, physical and mechanical properties of the hardened adhesive to varying degrees. In the case of adhesives used in the construction industry to strengthen and glue structural elements, these changes significantly affect the durability of the adhesive joints.

Surface Properties of Poly(Hydroxyurethane)s Based on Five-Membered Bis-Cyclic Carbonate of Diglycidyl Ether of Bisphenol A

Poly(hydroxyurethane)s (PHU) are alternatives for conventional polyurethanes due to the use of bis-cyclic dicarbonates and diamines instead of harmful and toxic isocyanates. However, the surface properties of poly(hydroxyurethane)s are not well known. In this work, we focus on the analysis of the surface properties of poly(hydroxyurethane) coatings. Poly(hydroxyurethane)s were obtained by a catalyst-free method from commercially available carbonated diglycidyl ether of bisphenol A (Epidian 6 epoxy resins) and various diamines: ethylenediamine, trimethylenediamine, putrescine, hexamethylenediamine, 2,2,4(2,4,4)-trimethyl-1,6-hexanediamine, m-xylylenediamine, 1,8-diamino-3,6-dioxaoctane, 4,7,10-trioxa-1,13-tridecanediamine, and isophorone diamine, using a non-isocyanate route. The structures of the obtained polymers were confirmed by FT-IR, ¹H NMR and ¹³C NMR spectroscopy, and thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses were performed. The rheological characteristic of the obtained polymers is presented. The static contact angles of water, diidomethane, and formamide, deposited on PHU coatings, were measured. From the measured contact angles, the surface free energy was calculated using two different approaches: Owens-Wendt and van Oss-Chaudhury-Good. Moreover, the wetting envelopes of PHU coatings were plotted, which enables the prediction of the wetting effect of various solvents. The results show that in the investigated coatings, a mainly dispersive interaction occurs.

Wettability of Asphalt Concrete with Natural and Recycled Aggregates from Sanitary Ceramics

In line with the current trend of seeking alternative methods for modification of the existing building composites, such as mineral–asphalt mixtures (MAMs), the materials from concrete and ceramics recycling are being used in increasingly wider applications. When added to MAMs as an aggregate, ceramic building material, which has different properties than the raw material (clay), may significantly influence the aggregate properties, including the wettability, porosity, asphalt adhesion, and consequently the mixture durability. The material’s microstructure was found using SEM. The wetting properties of mineral–asphalt mixtures were determined by measuring the contact angles (CA) of their surfaces, using water as the measuring liquid. The total surface free energy (SFE) values were determined using the Neumann method. When analyzing the research results, it can be noticed that the chemical composition of the ceramic aggregate has a significant influence on the adhesion of asphalt to its surface due to the chemical affinity. Waste ceramic aggregate, despite its acidic pH value being connected with its elevated silica content, exhibits good adhesive properties.