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Complex, hierarchic microstructures are prepared by electrophoretic deposition of SiO2 microspheres. A subsequent functionalization via sol-gel technique using perfluorsilanes leads to superoleophobic surfaces. A crucial step of the used process is the application of laser-structured aluminum substrates for electrophoretic deposition leading to complex three-dimensional surface structures. After a chemical functionalization step surfaces are generated that exhibit a huge contact angle against diiodomethane of 157° in air. This is significantly larger than the typically used threshold angle for superoleophobicity of 150°.

Aim The aim of this study was to determine the effect of surface physico-chemico-biological modifications of titanium on critical and theoretical surface free energy. Materials and Methods Cylindrical commercially pure titanium rods (99.9%) 1.27 cm in diameter were sectioned into 2 mm thick disks and polished on silicon carbide paper from 240 to 600 grit. Discs were divided into 3 treatment groups as follows, (a) Chemical treatment group which were treated with HNO3, HF/HNO3, or H2O2/HCL; (b) Physical treatment group, which were treated with autoclaving, autoclaving + Plasma treatment, and HNO3 + Plasma Cleaning and (c) Biological treatment group which were treated with H2O2/HCl followed by attachment of Collagen II or Soaking in simulated body fluid (SBF) Kokubo recipe to form hydroxyapatite. Contact angles of three investigational liquids (20 μl), distilled water, formamide and diiodomethane on the disks were measured using a single-lens reflex camera. Six measurements were made for each treatment. Surface free energies (SFE) were determined using the Zisman method for critical surface energy, the geometric mean method and acid-base theory. Data were compared using Analysis of Variance (ANOVA) and Tukey’s honestly significant difference (HSD) test (α = 0.05). Results/Conclusion Chemical treatment with HNO3 and H2O2/HCl and physical treatment by plasma cleaning of Ti surfaces resulted in significantly higher SFE compared to untreated Ti in all the different approaches for surface free energy determination. The geometric mean method and acid-base theory revealed that increases in SFE were due to increases in the polar and base components of surface energy. Biologically treated surface showed consistent increases in the acid component of surface energy although not statistically significantly different from controls. Information about the effect of surface treatments on SFE and its components provide insights into the preferred surface characteristics for facilitation of cellular activities on implant materials for osseo- and chondro- integration.

Graphene has to be supported on a substrate in a variety of applications. The underlying substrate can exert a remarkable impact on the wettability of graphene, but the inherent mechanism remains elusive. By quantifying the static contact angles of water (polar liquid) and diiodomethane (nonpolar liquid) droplets on graphene supported on different kinds of substrate, we found that the apparent wetting transparency of the supported graphene with airborne hydrocarbon adsorption depends essentially on polarities of both the liquids and the underlying substrates, and that, in most cases, the supported graphene exhibits wetting translucency. With the Owens-Wendt theory, we then identified the specific components of the surface energy, which indicated that inserting graphene does not introduce a polar interaction and that the apparent transmitted polar energy of one layer of graphene is ∼20% for the investigated substrates. The apparent polarity of supported graphene can potentially be tuned by the underlying substrate. Practically, the wettability of graphene can be determined by investigating the competitive relationship between the reduced dispersive and polar interaction of the substrate and the increased dispersive one introduced via inserting the graphene layers. Our findings may have significant implications in designing functional nanostructures through tuning the surface properties of graphene by its surroundings.

In the oral cavity dental restorative biomaterials can act as a reservoir for infection with opportunistic Staphylococcus aureus pathogen, which can lead to the occurrence of secondary caries and treatment failures. Our aim was to evaluate the adhesion forces by S. aureus on four dental restorative biomaterials and to correlate this finding to differences in specific surface characteristics. Additionally, the influence of salivary conditioning films in exerted adhesion forces was investigated. The substrate hydrophobicity was measured by goniometer and the surface free energy was calculated using the equilibrium advancing contact angle values of water, formamide, and diiodomethane on the tested surfaces. The surface roughness was determined using atomic force microscope (AFM). Additionally, cell force spectroscopy was achieved to quantify the forces that drive cell-substrate interactions. S. aureus bacterium exerted a considerable adhesion forces on various dental restorative materials, which decreased in the presence of saliva conditioning film. The influence of the surface roughness and free energy in initial adhesion appears to be more important than the effect of hydrophobicity, either in presence or absence of saliva coating. Hence, control of surface properties of dental restorative biomaterials is of crucial importance in preventing the attachment and subsequent the biofilm formation.

A series of apparent advancing and receding contact angles of water and diiodomethane was measured on the phospholipid/cholesterol monolayers physisorbed on the mica surfaces. It was found that the contact angles and their hystereses vary significantly depending on the lipid film composition and mutual miscibility of both components. These changes were much greater for water than diiodomethane. When the phase separation occurred, the hysteresis of water contact angle significantly decreased whereas the diiodomethane contact angle hysteresis increased considerably. Different behavior of both liquids may result from different mechanisms of the liquid droplets penetration/retention and points to structural changes that occur within the monolayers, including molecules rearrangement when exposed to water. The structure of the studied monolayer surfaces was confirmed by means of the microscopic techniques. The images are a visual evidence of cholesterol precipitation out the binary films at their specific stoichiometry. The results provide a new insight into the advancing/receding contact angles origin (and contact angle hysteresis) of polar and apolar liquids depending on the phospholipid/cholesterol monolayer composition, as well explanation of the origin of the contact angle hysteresis on the model biological surfaces, which are molecularly smooth.

In this paper, a low-cost, high-efficiency and high-flexibility surface modification technology for polymer materials was achieved at high laser scanning speeds (600–1000 mm s−1) and using an all-solid state, Q-switched, high-average power, and nanosecond pulse ultraviolet (355 nm wavelength) laser. During the surface modification of a very important engineering plastic, i.e., black bisphenol A polycarbonate (BAPC) board, it was found that different laser parameters (e.g., laser fluence and pulse frequency) were able to result in different surface microstructures (e.g., many tiny protuberances or a porous microstructure with periodical V-type grooves). After the modification, although the total relative content of the oxygen-containing groups (e.g., C O and COO−) on the BAPC surface increased, however, the special microstructures played a deciding role in the surface properties (e.g., contact angle and surface energy) of the BAPC. The change trend of the water contact angle on the BAPC surface was with an obvious increase, that of the diiodomethane contact angle was with a most decrease, and that of the ethylene glycol contact angle was between the above two. It showed that the wetting properties of the three liquids on the modified BAPC surface were different. Basing on the measurements of the contact angles of the three liquids, and according to the Young equation and the Lifshitz van der Waals and Lewis acid–base theory, the BAPC surface energy after the modification was calculated. The results were that, in a broad range of laser fluences, pulse frequencies and scanning speeds, the surface energy had a significant increase (e.g., from the original of about 44 mJ m−2 to the maximum of about 70 mJ m−2), and the higher the laser pulse frequency, the more significant the increase. This would be very advantageous to fabricate the high-quality micro-devices and micro-systems on the modified surface.

Porous super-hydrophobic polyvinyl chloride (PVC) surfaces were obtained via a facile solvent/non-solvent coating process without introducing compounds with low surface energy. The microstructure, wetting behavior, and corrosion resistance of resultant super-hydrophobic PVC coatings were investigated in relation to the effects of dosage of glacial acetic acid and the temperature of drying the mixed PVC solution spread over glass slide substrate. As-prepared PVC coatings had porous microstructure, and the one obtained at a glacial acetic acid to tetrahydrofuran volume ratio of 2.5:10.0 and under a drying temperature of 17 °C had a water contact angle of 150 ± 1.5°, showing super-hydrophobicity. In the meantime, it possessed very small contact angles for liquid paraffin and diiodomethane and good corrosion resistance against acid and alkali corrosive mediums, showing promising applications in self-cleaning, waterproof for outer wall of building, seawater resistant coating, and efficient separation of oil and water.

In order to investigate the effect of the polyamide benzimidazole group on the surface wettability and interfacial adhesion of fiber/matrix composites, surface features of two kinds of aramid fibers, poly (p-phenylene terephthalamide) fiber (Kevlar-49) and poly-(polyamide benzimidazole-co-p-phenylene terephthalamide) (DAFIII), have been analyzed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle analysis (CAA) system, respectively. The results show that with the incorporation of the polyamide benzimidazole segment, more polar functional groups exist on DAFIII surface. The contact angles of water and diiodomethane on DAFIII surface get smaller. The surface free energy of DAFIII increases to 36.5 mJ/m2, which is 2.3% higher than that of Kevlar-49. In addition, DAFIII has a larger rough surface compared with that of Kevlar-49 due to different spinning processes. The interfacial shear strength (IFSS) of DAFIII/matrix composite is 25.7% higher than that of Kevlar-49/matrix composite, in agreement with the observed results from surface feature tests. SEM micrographs of failed micro-droplet specimens reveal a strong correlation between the fracture features and the observed test data.

The effect of enzymes: lipase from Candida cylindracea (L Cc ), phospholipase A 2 from hog pancreas (PLA 2 ) and phospholipase C from Bacillus cereus (PLC) to modulate wetting properties of solid supported phospholipid bilayers was studied via advancing and receding contact angle measurements of water, formamide and diiodomethane, and calculation of the surface free energy and its components from van Oss et al. (LWAB) and contact angle hysteresis (CAH) approaches. Simultaneously, topography of the studied layers was determined by Atomic Force Microscopy (AFM). The investigated lipid bilayers were transferred on mica plates from subphase of pure water by means of Langmuir–Blodgett and Langmuir–Schaefer techniques. The investigated phospolipid layers were: saturated DPPC (1,2-dipalmitoyl- sn -glycero-3-phosphocholine), unsaturated DOPC (1,2-dioleoyl- sn -glycero-3-phosphocholine), and their mixture DPPC/DOPC. The obtained results revealed that the lipid membrane degradation by the enzymes caused increase in its surface free energy due to the amphiphilic hydrolysis products, which may accumulate in the lipid bilayer. In result activity of the enzymes may increase and then break down the bilayer structure takes place. It is likely that after dissolution of the hydrolysis reaction products in the bulk phase, patches of bare mica surface are accessible, which contribute to the apparent surface free energy changes. Comparison of AFM images and the free energy changes of the layers gives better insight into changes of their properties. The observed gradual increase in the layer surface free energy allows controlling of the hydrolysis process to obtain the surfaces of defined properties.

Advancing and receding contact angles of water, formamide, glycerol and diiodometane were measured on the two polymers; EGDMA (dimethacrylate of ethylene glycol) and TRIM (trimethacrylate-1,1,1-trihydroksymethylopropane) which were polymerized next to glass, silanized glass, stainless steel, mica and silicon surfaces as the matrices. Then from the contact angle hystereses (CAH) and van Oss, Good, Chaudhury (LWAB) approaches the apparent surface free energies were evaluated. The measured contact angles not only depend solely on the polymer chemical structure but also, to some extent, on the solid matrix next to whose surface the sample has polymerized. Surface free energy of the polymer samples calculated from the LWAB approach shows that they interact mainly by dispersive forces. The apparent surface free energy of the polymers calculated from the diiodomethane contact angles hysteresis is practically the same irrespective of the kind of the matrix used. Therefore it can be concluded that the observed weak polar interactions in the surface free energy of the samples depend on the polymer surface preparation. The AFM images show that the obtained surfaces are of different roughness. The RMS values of roughness range between 3.7–90.2 nm for EDGMA, and 5.3–124.5 nm for TRIM. However, as reported in literature, rather protrusions bigger than 1 μm may significantly affect the contact angles, especially the receding ones.

An investigation of wetting and energetic properties of different lipid layers deposited on the glass surface was carried out by contact angles measurements and determination of the apparent surface free energy. The topography of the lipid layers was also determined with the help of atomic force microscopy (AFM). Two synthetic phospholipids were chosen for these studies, having the same phosphatidylcholine headgroup bound to the apolar part composed either by two saturated chains (1,2-dipalmitoyl- sn -glycero-3-phospshocholine – DPPC) or two unsaturated chains (1,2-dioleoyl- sn -glycero-3-phosphocholine – DOPC) and one lipid (1,2,3-trihexadecanoyl- sn -glycerol – tripalmitoylglycerol – TPG). The lipid layers, from the 1st to the 5th statistical monolayer, were deposited on the glass surface from chloroform solutions by spreading. The apparent surface free energy of the deposited layers was determined by contact angles measurements (advancing and receding) for three probe liquids (diiodomethane, water, and formamide), and then two concepts of interfacial interactions were applied. In the contact angle hysteresis approach (CAH) the apparent total surface free energy was calculated from the advancing and receding contact angles and surface tension of probe liquids. In the Lifshitz–van der Waals/acid–base approach (LWAB) the total surface free energy was calculated from the determined components of the energy, which were obtained from the advancing contact angles of the probe liquids only. Comparison of the results obtained by two approaches provided more information about the changes in the hydrophobicity/hydrophilicity of the layers depending on the number of monolayers and kind of the lipid deposited on the glass surface. It was found that the most visible changes in the surface free energy took place for the first two statistical monolayers irrespectively of the kind of the lipid used. Additionally, in all cases periodic oscillations from layer-to-layer in the lipid surface free energy were observed. The changes in the surface free energy correlated with those in the topography and roughness of lipid layers.

A super-hydrophobic and super-oleophilic silica film on stainless steel mesh was obtained by simple sol–gel method using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as precursors. The super-hydrophobic and super-oleophilic properties were achieved owing to the hierarchical structure of the silica film with methyl groups terminated domains constructed on the mesh. The effects of the particle size, molar ration of MTES/TEOS, molar concentration of TEOS and aging of the silica sol on the hydrophobicity of the silica film were discussed. With increasing the dimensional size of silica particle, molar ration of MTES/TEOS, molar concentration of TEOS and aging period, the hydrophobicity of the silica film can be enhanced due to the increase of the surface roughness or coverage of the methyl groups. Besides, diiodomethane droplet can spread out on the silica film within 6.71 s for the capillary force and intrinsic oleophilicity of the methyl groups.

Advancing and receding contact angles of water, formamide, glycerol and diiodomethane were measured on polypropylene (PP) and polycarbonate (PC) sample surfaces which solidified at Teflon, glass or stainless steel as matrix surfaces. Then from the contact angle hystereses (CAH) the apparent free energies γ s tot of the surfaces were evaluated. The original PP surface is practically nonpolar, possessing small electron donor interaction ( γ s − = 1.91 mJ/ m 2 ), as determined from the advancing contact angles of these liquids. It may result from impurities of the polymerization process. However, it increases up to 8–10 mJ/m2 for PP surfaces contacted with the solids. The PC surfaces both original and modified show practically the same γ s − = 6.5 6.7 mJ/ m 2 . No electron acceptor interaction is found on the surfaces. The γ s tot of modified PP and PC surfaces depend on the kind of probe liquid and contacted solid surface. The modified PP γ s tot values determined from CAH of polar liquids are greater than that of original surface and they increase in the sequence: Teflon, glass, stainless steel surface, at which they solidified. No clear dependence is observed between γ s tot and dielectric constant or dipole moment of the polar probe liquids. The changes in γ s tot of the polymer surfaces are due to the polymer nature and changes in its surface structure caused by the structure and force field of the contacting solid. It has been confirmed by AFM images.

The modification induced in polystyrene (PS) by the ArF excimer laser radiation has been investigated. Various numbers of the laser pulses of the energies below the material ablation threshold were applied. Changes in the chemical composition of the PS surface layer were studied by the X-ray photoelectron spectroscopy (XPS). Analysis of the morphological changes in the polymer surface layer was performed via the atomic force microscopy (AFM). The contact angles of test liquids (water and diiodomethane) were measured with use of a goniometer while the surface energy (SE) was calculated by the Owens–Wendt method. It was found that the surface energy change was mainly affected by surface roughness caused by the laser radiation and that surface oxidation had not considerably contributed to this change. The increase in the SE was mostly due to its disperse component.

The surface properties of poly(vinyl alcohol) (PVA) films in the presence of 1%, 3% and 5% of collagen before and after UV-irradiation have been studied by atomic force microscopy (AFM) and by contact angle measurements. PVA films have been obtained by solvent evaporation from water solution of PVA and PVA containing small amount of collagen. After drying, the samples were irradiated with UV light wavelength λ = 254 nm in air. Surface properties before and after UV-irradiation were observed using AFM. Contact angles of two liquids: diiodomethane (D) and glycerol (G) on polymeric films were measured at constant temperature using goniometer. The results have shown that the contact angle and the surface free energy for PVA films were altered by UV-irradiation. These alterations indicate photooxidation and an increase of polarity of the surface. The comparison of surface properties of PVA films and PVA containing collagen points out that collagen is more sensitive to photooxidation than PVA and PVA/collagen blends. PVA films containing collagen easier undergo photooxidation process with formation of new polar groups than pure PVA films.

Polymers have been studied extensively due to the wonderful array of properties presented by them. Polymer materials can be coated/deposited by various techniques like sputtering (magnetron, ion beam, RF or dc), plasma polymerization, etc. and can be used in coatings, paint industries, etc. The present study deals with the RF sputter deposition of poly(tetrafluoro ethylene) (PTFE), commonly known as Teflon. Depositions were carried out on mirror polished silicon 〈1 0 0〉 substrates at different powers in the range of 100–200 W. The deposition time was kept constant at 60 min. The sputtered film shows lower contact angle of 50° with water and 44° with diiodomethane, a lower interfacial tension value of 0.76 dyne/cm, indicating hydrophilicity and good adhesion of the film with the substrate. FTIR indicates presence of C F, C F 2 bonding groups in the deposited film. Further, XPS study shows presence of CF 3 (292.2 eV), CF 2 (290.8 eV), C−F (288.0 eV) and C CF (286.4 eV) moieties indicating deposition of PTFE films at higher power levels of plasma.

The measurements of the contact angle for water (W), glycerol (G), formamide (F), ethylene glycol (E) and diiodomethane (D) on a bare cellulose acetate membrane and covered by adsorptive bovine serum albumin (BSA) films were made. The adsorption was performed from solutions in concentration range 0–100 mg/ml. An influence of the membrane porosity on an apparent contact angle was discussed and Cassie and Baxter equation was used for that purpose. It was suggested that some liquids could penetrate in to membrane pores reducing its apparent porosity. To explain such behaviour, the spreading coefficient and the work of adhesion was calculated for the studied liquids. Components and parameters of the surface free energy of a bare cellulose acetate membrane and covered by an adsorptive BSA film were determined for W–G–D, W–F–D and G–F–D three-liquid systems and they were similar for these systems. However, for the hydrated BSA layer those components and parameters for the systems W–G–D, W–F–D were different than those for the system G–F–D. It was stated that after BSA adsorption on that membrane percentage of empty pores decreased, reducing their number almost to 0, at the highest BSA concentrations.

A copolymer of polyethylene–polypropylene (PP/EPR) was irradiated using alpha particles under three different atmospheres. First, samples were irradiated by alpha particles (4.3 MeV) in a gas-tight chamber under either dry or moist air. Next, irradiation was carried out under a 4×10−4 Pa vacuum. Pristine and treated sample surfaces were studied by Attenuated Total Reflectance infrared spectroscopy (FT-IR/ATR). It was possible to ascertain that the chemical modifications produced differ according to the atmosphere during irradiation. Under vacuum, vinylic bonds were created. In moist air, carbonyl bonds were formed; and in dry air, both kinds of bonds were produced. In each case, a decrease in the number of CH bonds after irradiation was noted. As polypropylene is widely used in the automobile industry for parts like dashboards and bumpers, this study could be useful for many of the industry's applications. Indeed, it has been determined that, along with chemical modifications generated from the surface of the irradiated copolymer, an increase in its surface free energy results in greater wettability to certain liquids, such as water, formamide and diiodomethane.

Measurements of the contact angle for water, formamide and diiodomethane on pellets of cadmium sulfide were made. Also, the thin-layer wicking technique was used with n-decane, water and formamide as the penetrating liquids. The measurements were used to determine apolar, Lifshitz-van der Waals (γLW) and polar, acid-base (Lewis) (γAB) surface free energy components of monosized, spherical CdS colloidal particles. The results were compared with those obtained on a pure, commercial sample of cadmium sulfide. They both are monopolar materials, although synthetic CdS has a slightly higher electron-donor character (Lewis base) (γ-S=61.4 mJ/m2) than commercial cadmium sulfide (γ-S=56.0 mJ/m2). The γLW component has a similar value for both samples, in the range of 44–47 mJ/m2. ΔGTOT121, the free energy of interaction between particles in aqueous medium is for both synthetic and commercial CdS around 34.0 mJ/m2. In spite of the (small) attractive contribution due to the Lifshitz-van der Waals interaction (ΔGLW121), the large acid-base repulsion would ensure stability of CdS dispersions. Surface characteristics of the synthesized cadmium sulfide are similar to those of polydispersed commercial particles concerning their wetting properties. In consequence, the stability of dispersions of either kind of particles is expected to be the same. However, the use of perfectly spherical particles of this material is still valuable for testing model theories concerning interactions between particles in suspension.