Surface Free Energy Of Substrate Research Articles

From Silver Nanoparticle to Thin Films Produced by Pulsed Laser Deposition: Effects of Ar Gas Pressure and Substrate Surface Free Energy

From Silver Nanoparticle to Thin Films Produced by Pulsed Laser Deposition: Effects of Ar Gas Pressure and Substrate Surface Free Energy

Femtosecond laser printing-assisted etching tailored hard and brittle micro-convex surface.

We report a femtosecond laser print-assisted dry etching technology for high-efficiency, high-quality, and tailored fabricating of a micro-convex surface (MCS) on hard and brittle materials. Liquid ultraviolet curing adhesive (UVCA) was transferred from a donor substrate to a receiving substrate by femtosecond laser-induced forward transfer, and the transferred microdroplet spontaneously has a smooth surface under the action of surface tension. And then an MCS with a high-quality surface was formed on hard and brittle materials by UV curing and dry etching. The effects of laser parameters and receiving substrate surface free energy on MCS morphology were investigated. According to the variation of the numerical aperture, the two methods to change the morphology of the MCS were divided into independent/joint regulation of diameter and height. We showed that a hexagonal array containing a variety of MCS morphologies can be fabricated on a fused silica by setting the appropriate parameters. And the fabrication time of an MCS in a large-area array was only 1.1s.

How changes to the substrate’s physical characteristics can influence the deposition of touch and salivary deposits

An in-depth study into the physical substrate characteristics such as substrate surface roughness, topography, and physicochemical characteristics like wettability and surface free energy (SFE) was conducted to investigate the impact on the deposition and adherence of touch and salivary deposits on aluminium and polypropylene. A robust protocol was established to generate a set of substrates with a controlled linear surface roughness range (0.5–3.5 µm) in order to identify the impact of surface roughness on DNA transfer, persistence, prevalence, and recovery (DNA-TPPR). The polypropylene substrate was shown to produce fibres when artificially roughened, becoming more prominent at a higher surface roughness range, and has shown to have a direct impact on the distribution of salivary and touch deposits. At the low to moderate surface roughness range 0.5–2.0 µm, salivary and touch deposits have generally shown to follow the topographical features of the substrate they were deposited on, before a plateau of the surface roughness measure on the deposit was observed, indicating that a saturation point was reached and the grooves in the substrate were beginning to fill. Touch deposits have shown to maintain a consistent deposition height pre-surface roughness threshold, irrespective of substrate surface roughness while the deposition height of salivary deposits was heavily influenced by substrate surface roughness and topography. The substrate SFE, wettability, hydrophobicity, and the surface tension of the deposit was shown to drive the adhesion properties of the saliva and touch deposits on the respective substrates, and it was observed that this may be of importance for the improvement of the current DNA-TPPR understanding, DNA sampling protocols, and DNA transfer considerations within casework.

Factors to control the alignment of surface-treated titanium dioxide powders to maximize performance of sunscreens.

Titanium dioxide powders are contained in a large class of colour cosmetics and sunscreen formulas. When they are used, the formation of a uniform functional powder layer on the skin is an important factor to show their functionality, such as aesthetic and UV protection. Attempts were made to extract the factors that affect the UV shielding ability of the deposited powder layer. Seven kinds of surface treatments were conducted on nano-sized titanium dioxide powder to modify the surface characteristics. Dispersion samples were prepared by mixing these powders with liquids, such as mixed solutions of cyclopentasiloxane, isododecane, coconuts alkane and dimethicone using a disperser and a bead mill. The dispersions were applied using an applicator on cellulose triacetate film, polycarbonate film and polymethyl pentene film. Laser microscope observation and micro-gloss glossmeter analysis were carried out to assess the flatness of the deposited powder layers, and the UV shielding ability was evaluated using SPF analyser. Factors whose influences on the structure and UV shielding ability of the deposited powder layer being analysed were pseudo-HLB of the powders, liquids for preparing the dispersions and material of the substrates. Higher UV shielding ability was attained when powders having pseudo-HLB at around 6 were employed independent from the kinds of liquids and substrates. Flatness of the deposited layer was found to enhance the UV shielding ability of the UV-B region, while that of the UV-A region was scarcely influenced by the flatness. Employing lower surface tension liquids for preparing the dispersions and materials exhibiting lower polar components of surface free energy as substrates tended to enhance the UV shielding ability. Surface treatments conducted on the powders in this study were found to change UV shielding ability, especially UV-B shielding ability, and the relation between pseudo-HLB and UV shielding ability was scarcely influenced by the kinds of liquids. Both surface tension of liquids and the polar component of surface free energy of substrates affected the UV shielding ability. It was suggested that pseudo-HLB calculated based on chemical structure becomes useful information to choose optimum surface treatment to make uniform powder alignment independent from the surrounding environment.

Evidence for intermolecular forces involved in ladybird beetle tarsal setae adhesion

Why can beetles such as the ladybird beetle Coccinella septempunctata walk vertically or upside-down on a smooth glass plane? Intermolecular and/or capillary forces mediated by a secretion fluid on the hairy footpads have commonly been considered the predominant adhesion mechanism. However, the main contribution of physical phenomena to the resulting overall adhesive force has yet to be experimentally proved, because it is difficult to quantitatively analyse the pad secretion which directly affects the adhesion mechanism. We observed beetle secretion fluid by using inverted optical microscopy and cryo-scanning electron microscopy, which showed the fluid secretion layer and revealed that the contact fluid layer between the footpad and substrate was less than 10–20 nm thick, thus indicating the possibility of contribution of intermolecular forces. If intermolecular force is the main physical phenomenon of adhesion, the force will be proportional to the work of adhesion, which can be described by the sum of the square roots of dispersive and polar parts of surface free energy. We measured adhesion forces of ladybird beetle footpads to flat, smooth substrates with known surface free energies. The adhesive force was proportional to the square-root of the dispersive component of the substrate surface free energy and was not affected by the polar component. Therefore, intermolecular forces are the main adhesive component of the overall adhesion force of the ladybird beetle. The footpads adhere more strongly to surfaces with higher dispersive components, such as wax-covered plant leaves found in the natural habitat of ladybird beetles. Based on the present findings, we assume ladybird beetles have developed this improved performance as an adaptation to the variety of plant species in its habitat.

3-dimensional nucleation of Fe oxide induced by a graphene buffer layer.

Shaping the morphology of oxide nanolayers is of paramount importance in tailoring their physical and chemical properties. Here, the influence of a two dimensional graphene buffer layer on the growth of Fe oxide has been investigated by comparing the oxide deposition on a Ni(111) and a graphene/Ni(111) substrate. Scanning tunneling microscopy images acquired at a mesoscopic scale indicate that Fe oxide grows layer-by-layer on the bare Ni(111) surface, while the nucleation of three-dimensional clusters is induced by graphene. Atomically resolved images reveal that Fe oxide adopts an in-plane lattice constant similar to that of the FeO(111) surface when deposited on Ni(111) and graphene/Ni(111), indicating in both cases, a weak interaction between the overlayer and the substrate. Accordingly, it is suggested that the different growth mode is mainly driven by the graphene-induced lowering of the substrate surface free energy.

Screening effect of CVD graphene on the surface free energy of substrates.

The wettability of graphene has been a topic under constant discussion in the literature since 2012. In this work we measured the contact angle (CA) of six different types of substrates (glass, quartz, Si3N4, Si/SiO2, sapphire and Si) with varying dielectric constants and surface roughnesses in order to calculate the surface free energy of graphene films to evaluate how the wetting properties of graphene-coated substrates are changed according to the underlying substrate. We used a residual-free transfer process to remove the high-quality graphene (CVD-Gr) grown onto copper foil. Afterwards, we performed an inert thermal treatment (Ar, at 300 °C for 30 minutes) to remove airborne contaminants from the graphene surface and evaluate the roughness of substrates by atomic force microscopy, the advancing and receding contact angles of two liquids (water and ethylene glycol), hysteresis, and surface free energy (polar and dispersive components) calculations. The presence of high-quality monolayer graphene (free of any air contaminants, polymer residues, etc.) led to a common wettability behaviour for all coated surfaces, regardless of the nature of the underlying substrate. This result can be understood in terms of the screening of van der Waals and dipole interactions by the electrons in graphene.

Polymer Crystallization on Nanocurved Substrates: Distortion Versus Dewetting

The crystallization of a model semicrystalline polymer, namely, poly-3-hexylthiophene (P3HT), was studied as a function of the curvature at the nanometric scale and substrate surface free energy (SFE). Nanostructured substrates with a controlled local curvature were prepared by deposition of a 235 nm SiO2 particle monolayer, and their SFE was modulated by functionalization with octadecyltrichlorosilane, followed by radiofrequency plasma oxidation. The crystallization of ultrathin P3HT thin films, on the curved portions of the substrate, was found to mostly depend on the substrate SFE, while spontaneous wetting occurred in all cases. The effect is analyzed in terms of the interplay of polymer wetting (affecting the interfacial free energy) and lamellar crystallization, implying the modulation of crystallization enthalpy, demonstrating that the balance between SFE minimization and crystallization enthalpy maximization governs the phenomenon. The results highlight the role played by the surface nanostructuri...

Corrosion protection properties and interfacial adhesion mechanism of an epoxy/polyamide coating applied on the steel surface decorated with cerium oxide nanofilm: Complementary experimental, molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods

The effect of cerium oxide treatment on the corrosion protection properties and interfacial interaction of steel/epoxy was studied by electrochemical impedance spectroscopy, (EIS) classical molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods X-ray photoelectron spectroscopy (XPS) was used to verify the chemical composition of the Ce film deposited on the steel. To probe the role of the curing agent in epoxy adsorption, computations were compared for an epoxy, aminoamide and aminoamide modified epoxy. Moreover, to study the influence of water on interfacial interactions the MD simulations were executed for poly (aminoamide)-cured epoxy resin in contact with the different crystallographic cerium dioxide (ceria, CeO2) surfaces including (100), (110), and (111) in the presence of water molecules. It was found that aminoamide-cured epoxy material was strongly adhered to all types of CeO2 substrates, so that binding to ceria surfaces followed the decreasing order CeO2 (111)>CeO2 (100)>CeO2 (110) in both dry and wet environments. Calculation of interaction energies noticed an enhanced adhesion to metal surface due to aminoamide curing of epoxy resin; where facets (100) and (111) revealed electrostatic and Lewis acid-base interactions, while an additional hydrogen bonding interaction was identified for CeO2 (110). Overall, MD simulations suggested decrement of adhesion to CeO2 in wet environment compared to dry conditions. Additionally, contact angle, pull-off test, cathodic delamination and salt spray analyses were used to confirm the simulation results. The experimental results in line with modeling results revealed that Ce layer deposited on steel enhanced substrate surface free energy, work of adhesion, and interfacial adhesion strength of the epoxy coating. Furthermore, decrement of adhesion of epoxy to CeO2 in presence of water was affirmed by experimental results. EIS results revealed remarkable enhancement of the corrosion resistance of epoxy coating applied on the steel specimens treated by cerium oxide.

Ice accretion by spraying supercooled droplets is not dependent on wettability and surface free energy of substrates

Three different characterization tests namely, ice adhesion strength, drop freezing time and a newly developed ice accretion method were applied to surfaces which were commonly used in anti-icing research such as aluminum, stainless steel, copper, styrene butadiene rubber, polypropylene and polytetrafluoroethylene in order to investigate the effect of their water wettability and surface free energies on their anti-icing performances. It was found that ice adhesion strengths increased and drop freezing times decreased with the increase of the total surface free energies and decrease of the water contact angles on these surfaces similar to previously published reports however, no direct relationship was found between the ice accretion results and solid wettability, surface free energies and the reasons were discussed in terms of heterogeneous nucleation mechanisms.

The effects of substrate surface properties on tack performance of acrylic Pressure-Sensitive Adhesives (PSAs)

The effects of substrate surface free energy (SFE) and substrate roughness on tack performance of adhesive tapes containing synthesized model acrylic pressure-sensitive adhesive (PSA) have been investigated. In order to study the influence of substrate SFE on tack the adherents with the same surface roughness (expressed by selected amplitude parameters) were used: PTFE, PP, PE, ABS, PC, PMMA, stainless steel and glass. The relationship between substrate roughness and tack was investigated using two polypropylene plates (PP and PPrough) characterized as having the same wettability (SFE). For tack determination the most common method in the PSA tapes industry was employed (loop tack test). The conducted experiments showed that substrate SFE is a crucial factor governing tack properties of acrylic PSAs. In general, a larger difference between the SFE values of the substrate and adhesive were correlated with greater tack values. The dependence of tack and SFE was significantly influenced by crosslinking degree and layer coat weight of model acrylic PSA. The experiments carried out in the second part of the study revealed that the adhesive׳s viscoelastic properties control the tack properties on rough substrates, however, the final tack performance was found to be strongly affected by the level of substrate roughness and PSA thickness.

Effect of surface free energy to control the deposit morphology during evaporation of graphite/SDS dispersion drops

Uniform spherical cap shaped graphite/sodium dodecyl sulfate surfactant (SDS) micro-deposits were formed after the complete evaporation of aqueous graphite/SDS dispersion drops containing 2 and 4mM of SDS and 10, 20, 40, 60, 80 and 110mg/ml graphite micro-powder on hydrophobic surfaces such as Teflon-FEP and tridecafluorooctyltriethoxysilane coated glass slides. The shapes and sizes of the graphite/SDS micro-deposits were also investigated on polypropylene, polymethyl methacrylate, and polyvinyl alcohol surfaces. A good linear relationship was found between the surface free energy of the substrates and the diameters of the graphite/SDS deposits. The volumes and heights of the spherical cap shaped deposits can be controlled by varying the substrate surface free energy, concentration of graphite and SDS in the dispersion drop. SDS adsorption on graphite resulted in better surface packing of the microparticles on hydrophobic substrates. Effect of particle size on the deposit shape and size was also investigated by comparing SDS/graphite deposits formed from carbon microparticles with SDS/fullerene deposits formed from carbon nanoparticles. In addition, “stick-slip” motion of a (graphite+water) dispersion droplet on a polypropylene surface was investigated by the model proposed by Shanahan et al. and the potential energy barrier was calculated to be small for graphite microparticles on this surface.

Self-organised patterns in polymeric films solidified from diluted solutions – The effect of the substrate surface properties

Abstract The effect of the substrate surface free energy on the formation of organised structures developed during solvent evaporation was studied. Aqueous solution of 2-hydroxyethyl cellulose in temperature gradient under the Benard–Marangoni convective flow conditions was used as a model system. Polystyrene was used as a model substrate and its surface properties were modified with the low-temperature plasma. Changes in the substrate surface and their stability were monitored with contact angle measurement and atomic force microscopy. Solidification of the polymeric solutions was carried out in the specially constructed apparatus (Micro-condensation drying system) at defined temperature gradient and solvent evaporation rate. The effect of molecular weight distribution width, time of substrate surface plasma treatment, homogeneity of plasma treatment, size of the container with the polymeric solution and polymeric solution initial height was examined. Experimental results indicate crucial influence of the substrate surface energy on the development of self-organised patterns in films solidified from diluted polymeric solutions with broad molecular weight distribution.

Lattice plane control of liquid crystal blue phase

A correlation between the orientation of the lattice plane of liquid crystal blue phase (BP) and the surface free energy of the solid substrates which were coated with a polyimide thin layer or treated by a silane coupling reagent was investigated. The lattice plane was identified from the optical texture observation and the reflection spectra of BP. It was confirmed that the orientation of the lattice plane of BP was closely related to the surface free energy of the substrate. In particular, the area fraction of the lattice plane {110} of BP I increased as the polar component (γp) decreased.

Forced Wetting Dynamics of Sodium Dodecyl Sulfate Glycerol Solution on Solid Substrates

The forced wetting dynamics of a sodium dodecyl sulfate glycerol solu- tion on both intermediate hydrophilic and hydrophilic solid substrates was studied by using the Wilhelmy plate method. The dynamic contact angle θD at different contact line velocities U (θD-U relationship) was measured. The influences of the macro- scopic properties including the surfactant solution concentration, the substrate surface free energy, and the surface tension on the θD-U relationship were investigated, and all three properties are important. An interesting phenomenon that θD initially increases then decreases with U was found in the experiment, which could not be explained by modern theoretical models. The microscopic effect of the surfactant adsorption on the solid-vapor interface near the three-phase contact line was used to explain this phenomenon. A modified molecular-kinetic model was proposed, and the model can well describe the experimental results.

Evaluation of the compatibility between low pressure melamine (LPM) film printing substrates and inkjet inks

Surface coated wood-based panels play a major role in the forest products industry as materials for construction and furniture elements in numerous interior and exterior applications. Their most important feature besides appropriate mechanical performance and chemical durability is an appealing visual appearance. In this contribution, recent research on the compatibility between two UV-curable inks and different melamine formaldehyde based surface films is presented. The surface texture properties of the printing substrates were investigated by roughness measurements. Substrate surface free energy was measured by contact angle measurements using three different testing liquids covering a wide range of polarities (glycerol, ethylene glycol and diiodomethane). The physical shape of the inkjet ink drops which were placed on the LPM printing substrates was monitored and recorded over time and used as an indicator for the wetting behavior of the tested inks and hence the printability. By combining contact angle and pendant drop measurements the surface tension of the inks was determined. The theoretical findings were confirmed by technological printing tests. To this end, as a hands-on method to establish ink-substrate wetting and compatibility flow coating tests were run and the most suitable ink was selected for printing. The printing results were closely related to the surface properties of the printing substrates.

INFLUENCE OF SURFACE FREE ENERGY ON ADHESION OF CrN THIN FILM DEPOSITED BY AIP METHOD

The purpose of this study is to examine the relationship between adhesion of CrN thin film and the surface free energy of substrate. CrN film was deposited on JIS SKH2 high speed tool steel by arc ion plating (AIP) method. The surface free energy of the substrate was measured with/without ion bombardment process using nitrogen and argon gas under various gas flow rate before CrN deposition. The surface free energy was measured by the sessile drop method using distilled water and methylene iodide. The adhesion was evaluated by scratch testing and the relationship between a critical load and the surface free energy in each ion bombardment condition was discussed. As a result, it was found that the adhesion increased with decreasing the surface free energy, in particular the polar component strongly affects the adhesion.

What Determines the Lamellar Orientation on Substrates?

The recrystallization behavior of poly(ethylene oxide) (PEO) on four amorphous films of poly(vinyl alcohol) (PVA), lysozyme (LYSO), poly(vinylpyrrolidone) (PVPY), and poly(acrylic acid) (PAA) was investigated using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The results show that both the degree of supercooling and PEO/substrate interactions have pronounced influence over the growth behavior of the PEO crystals. A thermodynamic model has been proposed accordingly, in which the lamellar orientation is associated with the favorite primary nucleation. We predict the lamellar orientation based on the degree of supercooling and the surface free energy of substrate. The transition of lamellar orientation from edge-on to flat-on is determined by a critical surface free energy of the substrate which is equal to the surface tension of the polymer melt.

Improved wetting of bare and pre-coated steels by aqueous alumina sols for optimum coating success

Alumina coatings are a promising candidate for the protection of metals prone to high temperature corrosion. If applied via sol–gel process, especially by using so called aqueous modified Yoldas-sols, the deposition is hardened by differences in surface free energy of substrate and sol. In this paper the apparent surface properties of samples to be coated and sols were examined by contact angle measurements, IR-spectroscopy and tensiometry. The results imply, after consideration of possible uncertainties, the use of surface tension reducing 2-butanol already present during hydrolysis of the sols to obtain an easy and successful coating process.

Substrate dependent buffer‐layer assisted growth of nanoclusters

AbstractThe role of the substrate on the morphology of nanometer size clusters fabricated by buffer layer assisted growth (BLAG) was studied using scanning tunneling microscopy. Clusters of Fe and Co were deposited on Ag(111), Cu(100), Rh(111), and Pt(111) surfaces using identical BLAG parameters, which are temperature, as well as metal and buffer layer coverage. Semi‐hemispherical clusters are found on Ag(111) and Cu(100), while flat monolayer high islands are observed on Rh(111) and Pt(111) due to complete wetting. The results of this study are in agreement with the common notion that BLAG is useful to deposit clusters of virtually any material on any substrate, however, the shape, size, and lateral distribution of the resulting clusters depend strongly on the substrate surface free energy and diffusion processes.