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The necessity for innovative biomaterials has been growing recently due to the rising cost of materials for intricate biomedical equipment. An important tactic to improve critical attributes like hemocompatibility, osseointegration potential, corrosion resistance, and antibacterial capabilities is surface modification. In this paper, an investigation has been made in the field of laser surface modification and the complex interactions between laser parameters and output performance metrics, such as contact angle and surface roughness. Surface modification by laser has been successful and, in this research, the laser parameters such as laser energy (Watts), standoff distance(mm), and frequency (kHz) along with dimple distance on the surface ($\mu$m) were considered on the output performance namely surface roughness in “$\mu$m” and contact angle in “degree”. The experiment has been carried out using the L16 orthogonal array to interpret the complex correlations between these factors and the resulting surface features. Non-dominated sorting genetic algorithm II (NSGA-II) has successfully navigated the complex parameter space and found the optimal combinations that yield the intended outcomes. The results show how important dimple distance and laser frequency are in creating hydrophobic surfaces, as well as how much of an impact they have on surface properties. It has been discovered that higher frequencies and longer standoff distances specifically reduce surface roughness, which is a crucial component in ensuring enhanced biomaterial performance. The result shows that the dimple distance and frequency of the laser have a significant effect on the development of hydrophobic surfaces. Moreover, high frequency and more standoff distance reduce the surface roughness. The predicted combination of laser parameters as per the NSGA-II is 102.91$\mu$m, 33.35W, 223.12mm, 50.01kHz, and gives a surface roughness of 0.86$\mu$m and contact angle of 158.83^∘. In essence, this study not only sheds light on the intricate dynamics governing laser-based surface modification but also paves the way for the design and development of advanced biomaterials with tailored surface properties, poised to revolutionize biomedical applications.

The plasma electrolytic polishing (PEP) process on Q235 low-carbon steel anode in $({\text{NH}}_4{)}_2$SO₄ electrolyte was investigated, and its surface properties under different PEP conditions were evaluated. The surface roughness of PEP samples under different electrolyte concentrations, initial roughness, voltages and treating times were measured. The surface morphologies and compositions of typical PEP samples were analyzed, and their wettability and surface free energy under different polishing times were evaluated. It was found that the near-surface temperature of the steel sample raised quickly with increasing the voltage, and then remained at about 100°C after 200V, which is beneficial to keep the microstructure and mechanical properties of Q235 low-carbon steel. Under the parameters of 3.0wt.% $({\text{NH}}_4{)}_2$SO₄ aqueous solution and applied voltage of 200V, the 8min PEP treatment could reduce the surface roughness of Q235 low-carbon steel from 2.100$\mu$m to 0.437$\mu$m. In addition, the polishing efficiency was the highest in the initial PEP stage, meanwhile, it also increased with the increase of initial roughness of the sample. After the PEP treatment, the contact angle of water on low-carbon steel decreased, and its surface free energy was slightly reduced. Moreover, the thickness of natural oxide film on Q235 low-carbon steel was reduced by about 30% after 8 min polishing treatment.

The surface wettability of laser-textured Ti-6Al-4V and 316L SS is compared in this work. The surface of Ti-6Al-4V and 316L SS was micro-laser textured with varying dimple distances with the help of a nanosecond fiber laser. The composition of the material is evaluated using Energy Dispersive Spectroscopy and the surface roughness of the laser-textured samples was evaluated using a 3D optical profilometer. The results of the measurement of contact angle reveal information on the substrate’s wettability. The contact angle of Ti-6Al-4V was significantly reduced from 9$4.99^{\circ }$ to $56.46^{\circ }$ for 100$\mu$m dimple distance at 98% energy while 316L SS contact angle was reduced from $150^{\circ }$ to $60.21^{\circ }$ for 200$\mu$m at 98% energy.

In the non-ideal gas lattice Boltzmann equation (LBE), the intermolecular forces between solid and fluid can be represented by the inclusion of the wall free energy in the expression of the total free energy. We derived and investigated three types of polynomial (linear, quadratic, and cubic) wall free energy based boundary conditions for the non-ideal gas LBE method. Static cases with a liquid drop sitting on solid surfaces are examined. All the proposed boundary conditions are able to predict the equilibrium states very well in the range of moderate contact angles by incorporating the potential form of the intermolecular forces and the bounce-back rule that guarantees mass conservation. Simulations with different boundary conditions are carried out and the results are compared concerning the accuracy as well as the applicability of different polynomial boundary conditions.

This paper has reported the effect of oxygen and argon plasma treatments of CIIR rubber using Attenuated Total Reflectance (ATR) and surface energy measurements. Plasma treatment led to changes in the surface energy from 31 to 45.7 mN/m. Plasma treatment conditions influenced both the changes in surface energy and stability, and they also became more difficult to obtain good contact angle measurements. However, plasma treatments made the interfacial properties to be stabilized. ATR measurements revealed that changes in surface energy with treatment time are due mostly to increased oxygen functionality.

The wetting behavior of Ti-78Cu and Ti-50Cu alloys on graphite has been investigated by the sessile drop method in high vacuum. The contact angle of Ti-Cu alloys on graphite is influenced by the wetting temperature. The wetting of Ti-78Cu and Ti-50Cu alloys on graphite is chemical wetting. The microstructure and composition of the interfacial zone of the wetting samples were analyzed by SEM, EDX and XRD. Microstructure and phase analysis reveals that inter-diffusions and interfacial reactions take place in the wetting process. The reaction products include TiC and the intermetallic compounds composed of Ti and Cu. The inter-diffusions and interfacial reactions contribute to the interfacial bonding.

Different treatment time and bias voltage with RF Ar plasma were used to improve tribological properties of NBR (Nitrile Butadiene Rubber). Chemical structure analyses of NBR by Attenuated Total Reflectance (ATR) were performed to clarify the functionality modification after the plasma treatment. In addition, wetting experiments were carried out by measuring the contact angle of distilled water drops on the NBR surface. ATR analysis revealed that the number of -C=O, -C-O, O-H functional groups increased after the argon plasma treatment. The functional groups led to changes in the contact angle from 100 to 50 degrees. The results showed that form-like nanostructures on the NBR was observed at the bias voltage of -400 V. The friction test showed that coefficient of friction after modified NBR in lubricated condition decreased from 0.25 to 0.15 with the increasing bias voltage due to the surface structure formations and better bonding with grease lubricant.

The effects of polishing pressure, polishing speed and pH value of the polishing slurry on the chemical activity of quartz glass, the material removal rate (MRR) and surface roughness (Ra) of the workpiece were studied. Using MRR and Ra as evaluation indexes, three factors and four levels of the orthogonal test were used to perform chemical mechanical polishing on quartz glass. By measuring the contact angle between the polishing slurry and workpiece, the influence of different polishing slurries on the chemical activity of quartz glass surface was studied. The processing mechanism of CMP quartz glass was analyzed. The order of important factors affecting MRR of quartz glass was: pressure $>$ rotation speed $>$ pH value; the order of significant factors affecting Ra of quartz glass was: pressure $>$ pH value $>$ rotation speed. The optimum polishing process parameter combination of the MRR was: pressure 27.58 kPa, rotation speed 85 rpm, pH value 12; the optimum polishing process parameter combination of the Ra was: pressure 13.79 kPa, rotation speed 85 rpm, pH value 12. The MRR and Ra of the workpiece are evaluated from the mechanical action of pressure and speed and the chemical action of polishing slurry on the workpiece. The results proved that the effect of the alkaline polishing solution on MRR and Ra of quartz glass is more significant than that of the acidic polishing slurry.

A cold cathode plasma source is constructed for modifying PTFE surface characteristics. The source was easily built, had a consistent plasma discharge medium and acceleration system. A cylindrical Langmuir probe is also used to evaluate plasma parameters like density, temperature or even plasma potential. This probe is designed to be moveable so that it may approach any desired position in the plasma volume. The influences of nitrogen pressure and probe-cathode gap on plasma parameters were investigated. The electron temperature $T_e$ fluctuated from $7.73\times 10^4$ to $6.8\times 10^4$eV as the pressure rises from 0.2 to 0.4mbar. Further, by increasing the cathode-probe gap from 0.4 to 2cm, the electron densities increased from $0.46\times 10^{10}$cm${}^{-3}$ to $0.89\times 10^{10}$cm${}^{-3}$. Furthermore, the contact angles, work of adhesion and surface free-energy of pristine as well as irradiated PTFE films, were estimated. The results demonstrated that by extending the plasma exposure duration from 0 to 12min, the water contact angle is lowered from 82.2^∘ to 30.5^∘. At these conditions, the work of adhesion is raised from 81.9 to 134.1mJ/m², as the surface free energy is increased from 29.8 to 71.8mJ/m².

Wetting of droplets on homogeneous and spherical concave rough surfaces is investigated based on thermodynamics. In this study, neglecting the droplet gravity and the thickness of the precursor film of the liquid–vapor interface, the three-phase system is divided into six parts using Gibbs concept of dividing surface. The system Helmholtz free energy is established based on thermodynamics. Supposing the temperature and chemical potential to be constant, a new generalized Young’s equation of the equilibrium contact angle for a spherical droplet on a spherical concave rough surfaces is obtained including the line tension effects. Under certain conditions, this generalized Young’s equation is the same as the Rusanov’s equation.

We present here an analysis of the regularity of minimizers of a variational model for epitaxially strained thin-films. The regularity of energetically-optimal film profiles is studied by extending previous methods and by developing new ideas based on transmission problems. The achieved regularity results relate to both the Stranski-Krastanow and the Volmer-Weber modes, the possibility of different elastic properties between the film and the substrate, and the presence of the surface tensions of all three involved interfaces: film/gas, substrate/gas, and film/substrate. Finally, geometrical conditions are provided for the optimal wetting angle, i.e. the angle formed at the contact point of films with the substrate. In particular, the Young–Dupré law is shown to hold, yielding what appears to be the first analytical validation of such law for a thin-film model in the context of Continuum Mechanics.

Spontaneous imbibition (SI) is a capillary-driven flow process, in which a wetting fluid moves into a porous medium displacing an existing non-wetting fluid. This process likely contributes to the loss of fracking fluids during hydraulic fracturing operations. It has also been proposed as a method for an enhanced recovery of hydrocarbons from fractured unconventional reservoirs. Numerous analytical and numerical approaches have been employed to model SI. Invariably, these idealize a fracture as the gap formed between parallel flat surfaces. In reality, rock fracture surfaces are rough over multiple scales, and this roughness will influence the contact angle and rate of fluid uptake. We derived an analytical model for the early-time SI behavior within a fracture bounded by parallel impermeable surfaces with fractal roughness assuming laminar flow. The model was tested by fitting it to experimental data for the SI of deionized water into air-filled rock fractures. Twenty cores from two rock types were investigated: a tight sandstone (Crossville) and a gas shale (Mancos). A simple Mode I longitudinal fracture was produced in each core by compressive loading between parallel flat plates using the Brazilian method. Half of the Mancos cores were fractured perpendicular to bedding, while the other half were fractured parallel to bedding. The two main parameters in the SI model are the mean separation distance between the fracture surfaces, $\bar{x}$, and the fracture surface fractal dimension $2\le D<3$. The $\bar{x}$ was estimated for each core by measuring the geometric mean fracture aperture width through image analysis of the top and bottom faces, while $D$ was estimated inversely by fitting the SI model to measurements of water uptake obtained using dynamic neutron radiography. The $\bar{x}$ values ranged from 45$\mu$m to 190$\mu$m, with a median of 93$\mu$m. The SI model fitted the height of uptake versus time data very well for all of the rock cores investigated; medians of the resulting root mean squared errors and coefficients of determination were 0.99mm and 0.963, respectively. Estimates of $D$ ranged from 2.04 to 2.45, with a median of 2.24. Statistically, all of the $D$ values were significantly greater than two, confirming the fractal nature of the fracture surfaces. Future research should focus on forward prediction through independent measurements of $D$ and extension of the existing SI model to late times (through the inclusion of gravity) and fractures with permeable surfaces.

This paper focuses on effects of roughness on wettability. According to Wenzel's equation, the transition of theoretical wetting contact angles is 90°, whereas many experimental results have indicated that such a transition takes place at contact angles smaller than 90°. A new model of wetting on roughness surface is established in this paper. The model indicates that the influencing factors of wetting on roughness surface include not only equilibrium contact angle θ₀ and surface roughness, but also the system of liquids and solid substrates. There is a corresponding transition angle for every surface roughness, and the transition angle is lower than 90°. Surface roughness is propitious to improve the contact angle only when θ₀ is lower than the transition angle. The effect of surface roughness on the contact angle increases with the increase of r_E. To engineer the surface with different roughnesses, a Ti test sample is polished with sandpaper with abrasive number 350, 500, 1000 and 2000; the contact angles of water on Ti are measured by the sessile drop method. The results of the theoretical analysis agree with experimental ones.

Controlled grafting of well-defined polymer brushes on the poly(vinylidene fluoride) (PVDF) films was carried out by the surface-initiated Atom Transfer Radical polymerization (ATRP). Surface-initiators were immobilized on the PVDF films by surface hydroxylation and esterification of the surface-tethered hydroxyl groups with 2-bromoisobutyrate bromide. Water contact angles on PVDF films were reduced by surface grafting of poly(ethylene glycol) monomethacrylate (PEGMA) and methyl methacrylate (MMA). Kinetics study revealed a linear increase in the graft concentration of PMMA and PEGMA with the reaction time, indicating that the chain growth from the surface, was consistence with a "controlled" or "living" process.

Polytetrafluoroethylene (PTFE) has been increasingly used in many industries due to its low frictional coefficient and excellent chemical inertness. The surface properties of PTFE are of importance in various applications. The surface properties of PTFE can be modified by different techniques. In this study, PTFE film was treated in oxygen plasma for improving surface wettability. The effects of plasma treatment on dynamic wetting behavior were characterized using Scanning Probe Microscopy (SPM), Fourier transform infrared spectroscopy (FTIR), and dynamic contact angle (DCA) measurements. SPM observations revealed the etching effect of the plasma treatment on the film. The introduction of hydrophilic groups by plasma treatment was detected by FTIR. The roughened and functionalized surface resulted in the change in both advancing and receding contact angles. Advancing and receding contact angles were significantly reduced, but the contact angle hysteresis was obviously increased after plasma treatment.

The surface modification mechanism of polyvinyl chloride (PVC) by ozonation was investigated to study the selective hydrophilization of PVC surface among other plastics. Infrared analysis confirmed the increase of hydrophilic groups. XPS analysis revealed that the increase was due to the structural change in chlorine group in PVC to hydroxylic acid, ketone, and carboxylic groups by ozonation. This chemical reaction by ozone could occur only for polymers with chlorides in its structure and resulted in the selective hydrophilization of PVC among various polymers.

In this study, a thermodynamic analysis is conducted to investigate the chemical effect, in terms of intrinsic contact angle (CA), on the superhydrophobic behavior. It is theoretically revealed that the essential effect of intrinsic CA is to promote the composite transition. In particular, a large intrinsic CA more than 90° is necessary for such transition. Furthermore, for a pillar system with an intrinsic CA smaller than 90°, composite states are not impossible but is thermodynamically unstable. Once composite states are achieved, the advancing or maximum CA always approaches 180° whether an intrinsic CA is larger or smaller than 90°. In addition, the role of intrinsic CA in the water-repellent or self-cleaning behavior such as contact angle hysteresis (CAH) and equilibrium CA has been discussed in detail.

Surface tension is one of the fundamental properties of the colloids, which can be altered by concentration and size of colloidal particles. In the current work, modeling of the surface tension of suspension as it would be analyzed by maximum bubble pressure method has been performed. A new modified equation to correlate the surface tension with the bubble pressure is derived by applying fundamental thermodynamic relation considering the presence of particles in suspension and curvature of the interface between the particles and bubbles inside liquid. Moreover, the change of particles concentration in air–water interface due to capillary force is also considered. The predicted surface tension using the developed model has been verified by numerous experimental data with deviation less than 5% in most of cases. It was found that the calculated surface tension is altered by contact angle and particle radius as well as particle concentration. The obtained model may have potential application to predict the surface tension of colloidal suspension.

Additive manufacturing (AM) of titanium (Ti) alloys has always fascinated researchers owing to its high strength to weight ratio, biocompatibility, and anticorrosive properties, making Ti alloy an ideal candidate for medical applications. The aim of this paper is to optimize the AM parameters, such as Laser Power (LP), Laser Scan Speed (LSS), and Hatch Space (HS), using Analysis of Variance (ANOVA) and Grey Relational analysis (GRA) for mechanical and surface characteristics like hardness, surface roughness, and contact angle, of Ti6Al4V ELI considering medical implant applications. The input parameters are optimized to have optimum hardness, surface roughness and hydrophilicity required for medical implants.

Reclusive single crystals of ammonium dihydrogen phosphate (ADP) and 0.1mol.% Acid Blue 22 dye-incorporated ADP were harvested by using a standard slow cooling mechanism. The skeletal framework of the anisotropic materials was analyzed by using single crystal X-ray diffraction cram. The powder X-ray diffraction examines the phase growth and incorporation of substituents in the crystalline matrices. The incorporation of additives in the system was examined by employing Fourier Transform Infrared Spectroscopy. The analysis of vibrational bands gives insights into the incorporation of additives in ADP crystal system. The transmission window of the specimen and optical bandgap of the given material were analyzed by using UV–Vis spectroscopic analysis. The incorporation of additives to parent crystals was examined by using Scanning Electron Microscope. The quantification of elements in the grown specimen was investigated by using Energy Dispersive X-ray spectroscopy. The mechanical rigidity of the material was inspected by using Vickers microhardness analysis. The piezoelectric charge coefficient of dye-incorporated ADP is higher than pristine ADP. The wettability of the material was identified by contact angle measurements. The optical stress was identified by employing photoelastic measurements. The second- and third-order nonlinear optical properties of pristine and dye-incorporated ADP crystals were investigated by using Kurtz–Perry powder technique and Z-scan technique.