Influence Of Surface Free Energy Research Articles

Influence of surface free energy of the substrate and flooded water on the attachment performance of stick insects (Phasmatodea) with different adhesive surface microstructures.

Stick and leaf insects (Phasmatodea) are exclusively herbivores. As they settle in a broad range of habitats, they need to attach to and walk on a wide variety of plant substrates, which can vary in their surface free energy (SFE). The adhesive microstructures (AMs) on the euplantulae of phasmids are assumed to be adapted to such substrate properties. Moreover, the natural substrates can often be covered with water as a result of high relative humidity or rain. Although considerable experimental research has been carried out on different aspects of stick insect attachment, the adaptations to cope with the influence of flooded water on attachment performance remain unclear. To elucidate the role of AMs in this context, we here measured attachment forces in three species of stick insects with different AMs. The results show that attachment forces of the three species studied were influenced by the SFE and the presence of water: they all showed higher pull-off (vertical) and traction (horizontal) forces on dry surfaces, compared with when the surfaces were covered with a water film. However, the extent to which the surface properties influenced attachment differed depending on the species and its AMs. All three species showed approximately the same attachment performance on dry surfaces with different surface free energy but maintained attachment underwater to different extents.

Surface Free Energy of Titanium Disks Enhances Osteoblast Activity by Affecting the Conformation of Adsorbed Fibronectin

This study evaluated the influence of surface free energy (SFE) of titanium disks on the adsorption and conformation of fibronectin (FN) and the biological behavior of osteoblasts cultured on the FN-treated modified surfaces. High [H]-SFE titanium disks were irradiated by a 30 W UV light, while low (L)-SFE titanium disks received no treatment. The surface characteristics of the titanium disks were examined using scanning electron microscope, optical surface profilometer, X-ray photoelectron spectroscopy, and contact angle measurements. Adsorbed FN on different groups was investigated using attenuated total reflection-Fourier transform infrared spectroscopy. MG-63 cells were cultured on FN-treated titanium disks to evaluate the in vitro bioactivity. The experiment showed H-SFE titanium disks adsorbed more FN and acquired more ß-turn content than L-SFE group. MG-63 cells cultured on FN-treated H-SFE titanium disks showed better osteogenic responses, including adhesion, proliferation, alkaline phosphatase activity and mineralization than that on FN-treated L-SFE titanium disks. Compared to L-SFE titanium disks, integrin-β1, integrin-α5 and Rac-1 mRNA levels were significantly higher in MG-63 cells on FN-treated H-SFE after 3 h of culture. These findings suggest that the higher SFE of H-SFE compared to L-SFE titanium disks induced changes in the conformation of adsorbed FN that enhanced the osteogenic activity of MG-63 cells.

Modeling the Influence of Surface Free Energy on Moisture Damage of Recycled Asphalt Concrete

Recycling is a sustainable process for restoration of the pavement quality. In this investigation, aged binder was recycled by digestion with (0.5, 1.0, and 1.5) % of polyethylene and crumb rubber. The recycled binder was implemented in the preparation of Marshal specimens. The surface free energy of the control and recycled binder was determined using the Sessile drop method. Specimens were tested under repeated indirect tensile and double punching shear stresses with the aid of pneumatic repeated load system (PRLS). Another group of specimens was tested for moisture damage, then subjected to the same loading sequence. Specimens were subjected to 1200 load repetitions under stress level of 0.138 MPa at 25 °C. The load was sustained for 0.1 second followed by 0.9 seconds of rest period. The permanent deformation was measured before and after moisture damage process for each testing technique. Regression analysis is used to develop a model for the influence of surface free energy on the deformation and the moisture damage using the SPSS Software. It was concluded that the obtained model can explain 82 % of the variation in moisture damage due to the influence of surface free energy.

Super-Hydrophobic Surface Prepared by Lanthanide Oxide Ceramic Deposition Through PS-PVD Process

Super-hydrophobic surface has received widespread attention in recent years. Both the surface morphology and chemical composition have significant impact on hydrophobic performance. A novel super-hydrophobic surface based on plasma spray-vapor deposition was introduced in the present paper. Samaria-doped ceria, which has been proved as an intrinsic hydrophobic material, was used as feedstock material. Additionally, in order to investigate the influence of surface free energy on the hydrophobicity, chemical modification by low surface free energy materials including stearic acid and 1,1,2,2-tetrahydroperfluorodecyltrimethoxysilane (FAS) was used on coating surface. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the coating surface. The results show that the obtained surface has a hierarchical structure composed by island-like structures agglomerated with angular-like sub-micrometer-sized particles. Moreover, with the surface free energy decreases, the hydrophobic property of the surface improves gradually. The water contact angle of the as-sprayed coating surface increases from 110° to 148° after modification by stearic acid and up to 154° by FAS. Furthermore, the resultant surface with super-hydrophobicity exhibits an excellent stability.

Chromium-doped DLC for implants prepared by laser-magnetron deposition.

Diamond-like carbon (DLC) thin films are frequently used for coating of implants. The problem of DLC layers lies in bad layer adhesion to metal implants. Chromium is used as a dopant for improvement of adhesion of DLC films. DLC and Cr-DLC layers were deposited on silicon, Ti6Al4V and CoCrMo substrates by a hybrid technology using combination of pulsed laser deposition (PLD) and magnetron sputtering. The topology of layers was studied using SEM, AFM and mechanical profilometer. Carbon and chromium content and concentration of trivalent and toxic hexavalent chromium bonds were determined by XPS and WDS. It follows from the scratch tests that Cr doping improved adhesion of DLC layers. Ethylene glycol, diiodomethane and deionized water were used to measure the contact angles. The surface free energy (SFE) was calculated. The antibacterial properties were studied using Pseudomonas aeruginosa and Staphylococcus aureus bacteria. The influence of SFE, hydrophobicity and surface roughness on antibacterial ability of doped layers is discussed.

Influence of surface free energy of denture base and liner materials onCandida albicansbiofilms

This study aimed to evaluate the influence of surface free energy (SFE) of denture base and liner materials on Candida albicans biofilm development. Discs were fabricated using poly(methyl methacrylate) acrylic resin and poly(ethyl methacrylate) denture liner, according to the manufacturers' instructions. For SFE test, discs were pellicle-coated with saliva alone, saliva+blood plasma, or blood plasma alone. Candida albicans biofilms were allowed to form on pellicle-coated discs for 48h. Biofilms were evaluated for cell counts, metabolic activity, and structural characteristics at adhesion phase (after 1.5h of development) and at biofilm maturity (after 48h of development). Data were analyzed by anova and Tukey tests using a significance level of 5%. Saliva+blood plasma pellicles had a higher SFE compared to pellicles of saliva or blood plasma alone (P<0.001). Differences in SFE by pellicle-coating did not affect the cell counts, metabolic activity, or structure at the adhesion phase (P>0.05). In contrast, the presence of blood plasma resulted in higher cell counts, biovolume, and thickness of mature biofilms on both materials (P<0.001). Increases in SFE from pellicle-coating leads to robust mature C.albicans biofilms on both denture materials.

多層カーポンナノチューブの分散性とコンポジットの導電'性に及ぼすポリマーの表面自由エネルギーの影響

多層カーポンナノチューブの分散性とコンポジットの導電'性に及ぼすポリマーの表面自由エネルギーの影響

Rigid frictionless indentation on elastic half space with influence of surface stresses

This paper proposes an application of continuum-based concepts in the analysis of an axisymmetric rigid frictionless indentor acting on an isotropic, linearly elastic half-space accounted for surface energy effects. The influence of surface stresses is considered by employing a complete Gurtin–Murdoch continuum model for surface elasticity. With use of standard Love’s representation and Hankel integral transform, such boundary value problem is reduced to a set of dual integral equations that can be further transformed into an equivalent Fredholm integral equation of the second kind. Selected numerical procedures based on the solution discretization and standard collocation technique are then implemented to construct its solution numerically. Obtained numerical results for elastic fields within the bulk are shown and compared for indentors of different profiles and contact radii at various depths. It is found that the influence of surface free energy on bulk stresses and displacements and the size-dependency of solutions become more apparent in a region very near the free surface. The significant contribution of the residual surface tension on predicted responses is obviously observed in comparison with existing results. The proposed mathematical model not only offers an alternative for specifically studying both mechanical properties and elastic fields for indentors of arbitrary axisymmetric profiles but also provides, in general, a crucial basis for further investigations in the area of nano-mechanics.

Metastability in Pressure-Induced Structural Transformations of CdSe/ZnS Core/Shell Nanocrystals

The kinetics and thermodynamics of structural transformations under pressure depend strongly on particle size due to the influence of surface free energy. By suitable design of surface structure, composition, and passivation it is possible, in principle, to prepare nanocrystals in structures inaccessible to bulk materials. However, few realizations of such extreme size-dependent behavior exist. Here, we show with molecular dynamics computer simulation that in a model of CdSe/ZnS core/shell nanocrystals the core high-pressure structure can be made metastable under ambient conditions by tuning the thickness of the shell. In nanocrystals with thick shells, we furthermore observe a wurtzite to NiAs transformation, which does not occur in the pure bulk materials. These phenomena are linked to a fundamental change in the atomistic transformation mechanism from heterogeneous nucleation at the surface to homogeneous nucleation in the crystal core.

The Influence of Surface Free Energy and Microrugosity on the Adhesion of Bacteria to Polymer Monofilaments

The Influence of Surface Free Energy and Microrugosity on the Adhesion of Bacteria to Polymer Monofilaments

Analysis of Rigid Frictionless Indentation on Half--Space with Surface Elasticity

The formulation of a boundary value problem of an axisymmetric, rigid, frictionless indentation acting on an elastic half-space is presented. The novel feature of this formulation is associated with the treatment of surface energy effects by employing a complete Gurtin-Murdoch continuum model for surface elasticity. With use of standard Love's representation and Hankel integral transform, such boundary value problem can be reduced innto a set of dual integral equations associated with the mixed boundary conditions on the surface of the half-space. Once these dual integral equations are transformed into a Fredholm integral equation of the second kind, selected numerical procedures based upon Galerkin approximation and a collocation technique are proposed to construct its solution numerically. The complete elastic fields are to be obtained for punches of different profiles and with smooth and non-smooth contact. The insight into the influence of surface free energy and size-dependency on material properties, gained in this particular study, should indicate and shed some lights on the implications related to soft elastic solids and nanotechnology.

In vivo and in vitro biofilm formation on two different titanium implant surfaces

The aim of the present in vitro and human in vivo study was twofold: first, to evaluate the initial biofilm formation on different titanium implant surfaces by means of two highly sensitive fluorescent techniques and, second, to correlate these findings to different surface properties. In vivo biofilm formation was induced on purely machined (Pt) and on sand-blasted and acid-etched titanium (Prom) specimens, which were mounted buccally on individual splints and worn by six study participants for 12 h. In vitro bacterial adhesion was also investigated after incubation with Streptococcus sanguinis suspension (37 degrees C, 2 h). Adherent bacteria were quantified by the following fluorescence techniques: Resazurin staining in combination with an automated fluorescence reader or live/dead cell labeling and fluorescence microscopy. Surface roughness (R(a)) was determined with a perthometer, and surface free energy (SFE) was measured with a goniometer. Prom showed a significantly higher median R(a) (0.95 microm) and a significantly lower median SFE (18.3 mJ/m(2)) than Pt (R(a)=0.15 microm; SFE=39.6 mJ/m(2)). The in vitro and in vivo tests showed a significantly higher bacterial adhesion to Prom than to Pt, and the initial biofilm formation on Pt corresponded to the circular surface modifications on the machined substratum. Both observations may be attributed to the predominant influence of surface roughness on bacterial adhesion. No significant differences in the percentage of dead cells among all adhering bacteria were found between Prom (23.7%) and Pt (29.1%). Ectopic solitary epithelial cells from the oral mucosa - strongly adhering to the substratum - were found on each Prom specimen, but not on any of the Pt surfaces. Initial bacterial adhesion to differently textured titanium surfaces is primarily influenced by R(a), whereas the influence of SFE seems to be of only minor importance. Therefore, the micro-structured parts of an implant that are exposed to the oral cavity should be highly polished to prevent plaque accumulation. Both tested fluorometric techniques proved to be highly sensitive and reproducible in the quantification of biofilm formation on titanium implant surfaces.

Influence of surface free energy on the adhesion of marine benthic diatom Nitzschia closterium MMDL533

The self-assembled monolayers (SAMs) with gradient surface free energies were prepared by surface grafting of a binary mixture of methyl and vinyl terminated trimethoxysilanes on hydrophilic glass slides followed by in situ oxidation of vinyl groups into carboxyl groups. Characterized by contact angles, the SAMs combined with freshly cleaned glass slides bearing hydroxyl groups were used to study the adhesion behavior of marine benthic diatom Nitzschia closterium MMDL533. The attachment densities were much higher on hydrophobic CH 3-SAMs and lower on mixed SAMs with surface free energy of 40.1–50.4 mJ/m 2. More gregarious adhesion had been found on hydrophobic CH 3-SAMs. The percentage removal was in a narrow range of 63–80% on the engineered surfaces and was much lower with a value of 54% on the hydrophilic slides. Our studies have revealed some subtle but interesting differences in attachment and adhesion from the features reported for these benthic species, indicating the possible links to different diatom species.

Chemically mediated diffusion of d-metals and B through Si and agglomeration at Si-on-Mo interfaces

Chemical diffusion and interlayer formation in thin layers and at interfaces is of increasing influence in nanoscopic devices, such as nanoelectronics and reflective multilayer optics. Chemical diffusion and agglomeration at interfaces of thin Ru, Mo, Si, and B4C layers have been studied with x-ray photoelectron spectroscopy, cross section electron energy loss spectroscopy, high-angle annular dark field scanning transmission electron microscopy, and energy dispersive x-ray in relation to observations in Ru-on-B4C capped Mo/Si multilayers. Rather than in the midst of the Si layer, silicides and borides are formed at the Si-on-Mo interface front, notably RuSix and MoBx. The interface apparently acts as a precursor for further chemical diffusion and agglomeration of B, Ru, and also other investigated d-metals. Reversed “substrate-on-adlayer” interfaces can yield entirely suppressed reactivity and diffusion, stressing the influence of surface free energy and the supply of atoms to the interface via segregation during thin layer growth.

Biofilm formation on pyrolytic carbon heart valves: Influence of surface free energy, roughness, and bacterial species

The aim of this study was to analyze the interaction of surface free energy and roughness characteristics of different pyrolytic carbon heart valves with three bacterial species on biofilm formation. Three pyrolytic carbon heart valves (St Jude Medical [St Jude Medical Inc, Minneapolis, Minn], Sulzer Carbomedics [CarboMedics Inc, Austin, Tex], and MedicalCV [Medical Incorporated, Inver Grove Heights, Minn]) were tested. Roughness was measured by interferential microscopy and surface free energy by contact angle technique. To obtain a biofilm, prostheses were inserted into a bioreactor with Staphylococcus aureus P209, Staphylococcus epidermidis RP62A, or Pseudomonas aeruginosa PAO1. Adhesion was quantified by counting sessile bacteria. Morphologic characteristics of biofilms were evaluated with scanning electron microscopy. Roughness analysis revealed significant differences between the MedicalCV (35.18 +/- 4.43 nm) valve and St Jude Medical (11.03 +/- 3.11 nm; P < .0001) and Sulzer Carbomedics (8.80 +/- 1.10 nm; P < .0001) valves. Analysis of surface free energy revealed a higher level for the MedicalCV valve (41.03 mJ x m(-2)) than for both the Sulzer Carbomedics (38.93 mJ x m(-2)) and St Jude Medical (31.51 mJ . m(-2)) models. These results showed a correlation between surface free energy and bacterial adhesion for S epidermidis and P aeruginosa species. Regardless of the support, we observed significant adhesion differences for the three bacterial species. S aureus was the most adherent species, S epidermidis was the least, and P aeruginosa was intermediate. Our results suggest that adhesion of S epidermidis and P aeruginosa are dependent on pyrolytic carbon surface free energy and roughness, although S aureus adhesion appears to be independent of these factors. Improvement of pyrolytic carbon physicochemical properties thus could lead to a reduction in valvular prosthetic infections.

Clinical relevance of the influence of surface free energy and roughness on the supragingival and subgingival plaque formation in man

Previous clinical studies illustrated a positive correlation between the rate of “supragingival” plaque maturation and both the free energy and roughness of the intraoral hard surfaces (teeth, prostheses, implants). The present review of the literature aims to examine the clinical importance of these parameters especially in the “subgingival” environment, where plaque causes periodontitis. Despite the clear cut differences between supragingival and subgingival environments (with more possibilities for adhesion and fewer removal forces for the latter), both the surface roughness and the surface free energy remain important. This could be proven in an in vivo study in patients with implant-supported prostheses, where abutments (trans-mucosal connections between implant in the bone and prosthetic reconstruction) with different surface characteristics were examined. After an undisturbed subgingival plaque formation of 3 months, the roughened surfaces harboured significantly more bacteria (51 × 10 4 colony-forming units (CFU)) than both smooth abutments (3 × 10 4 CFU), and fluorinated ethylene-propylene (FEP) coated abutments with comparable roughness (11 × 10 4 CFU). The plaque composition was also slightly surface dependent, with a more pathogenic situation around the roughened titanium abutments. However, if the “in the pocket swimming flora” was considered, most differences disappeared.

The Influence of Surface‐Free Energy on Supra‐ and Subgingival Plaque Microbiology. An In Vivo Study on Implants

The influence of surface free energy on supra- and subgingival plaque microbiology was examined in 9 patients with functional fixed prostheses supported by endosseous titanium implants. Two abutments (trans-mucosal part of the 2 stage implant) were replaced by either a new titanium abutment or a fluor-ethylene-propylene (FEP) coated abutment per subject. After 3 months of habitual oral hygiene, plaque samples were taken. Supragingival plaque was examined by means of differential phase-contrast microscopy, whereas for the subgingivial plaque additional analyses (DNA probes analysis, culturing) were performed. The subgingival samples were taken by paper-points and by scraping of the subgingival abutment surface. Differential phase-contrast microscopy showed a significant difference in plaque composition, especially when supragingival plaque was considered (P = 0.05). FEP coated abutments frequently harbored more coccoid microorganisms, whereas spirochetes or motile organisms were only detected around titanium abutments. Subgingivally, the number of colony forming units (CFU) in paper-points was comparable for both types of abutments. If the to-the-abutment-adhering plaque was considered, the number of CFU was 5 times higher on the titanium abutments than on the FEP coated abutments. However, this difference did not reach a statistical level of significance (P = 0.38). The DNA probe analysis of the subgingival plaque collected with paper-points showed a slightly higher frequency and concentration of perio-pathogens around the titanium abutments. However, the inter-substratum differences were smaller than the inter-subject differences. The latter seemed to be related to patient's dental status.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of surface free energy and surface roughness on early plaque formation.

Abstract Previous in vivo studies suggested that a high substratum surface free energy (s.f.e.) and an increased surface roughness facilitate the supragingival plaque accumulation. It is the aim of this clinical trial to explore the “relative” effect of a combination of these surface characteristics on plaque growth. 2 strips, one made of fluorethylenepropylene (FEP) and the other made of cellulose acetate (CA) (polymers with surface free energies of 20 and 58 erg/cm2, respectively) were stuck to the labial surface of the central incisors of 16 volunteers. Half the surface of each strip was smooth (Ra ± 0.1 μm) and the other half was rough (Ra ± 2.2 μm). The undisturbed plaque formation on these strips was followed over a period of 6 days. The plaque extension at day 3 and 6 was scored planimetrically from color slides. Finally, of 6 subjects samples were taken from the strips as well as from a neighbouring smooth tooth surface (s.f.e. 88 erg/cm2; Ra ± 0.14 μm). These samples were analysed with a light microscope to score the proportion of coccoid cells, and small, medium, and large rods or fusiform bacteria. At day 3, a significant difference in plaque accumulation was only obtained when a rough surface was compared with a smooth surface. However, at day 6, significantly less plaque was recorded on FEP smooth (19.4%) when compared with CA smooth (39.5%). Between FEP rough (96.8%) and CA rough (98.2%), no significant difference appeared. The latter were of course significantly higher than the scores of the smooth surfaces. Small differences in bacterial composition appeared: the highest % of coccoid cells was observed on FEP smooth (86.2%) and the lowest % on FEP rough (78.5%) and CA rough (82.8%). The results of this study suggested that the influence of the surface roughness on plaque accumulation and plaque composition is more prominent than the influence of the surface free energy.

The influence of surface free energy and surface roughness on early plaque formation

Previous in vivo studies suggested that a high substratum surface free energy (s.f.e.) and an increased surface roughness facilitate the supragingival plaque accumulation. It is the aim of this clinical trial to explore the "relative" effect of a combination of these surface characteristics on plaque growth. 2 strips, one made of fluorethylenepropylene (FEP) and the other made of cellulose acetate (CA) (polymers with surface free energies of 20 and 58 erg/cm2, respectively) were stuck to the labial surface of the central incisors of 16 volunteers. Half the surface of each strip was smooth (Ra +/- 0.1 microns) and the other half was rough (Ra +/- 2.2 microns). The undisturbed plaque formation on these strips was followed over a period of 6 days. The plaque extension at day 3 and 6 was scored planimetrically from color slides. Finally, of 6 subjects samples were taken from the strips as well as from a neighbouring smooth tooth surface (s.f.e. 88 erg/cm2; Ra +/- 0.14 microns). These samples were analysed with a light microscope to score the proportion of coccoid cells, and small, medium, and large rods or fusiform bacteria. At day 3, a significant difference in plaque accumulation was only obtained when a rough surface was compared with a smooth surface. However, at day 6, significantly less plaque was recorded on FEP smooth (19.4%) when compared with CA smooth (39.5%). Between FEP rough (96.8%) and CA rough (98.2%), no significant difference appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Solid/solid wetting in MoO 3/TiO 2 system

XRD, FT/IR and XPS studies of MoO 3/anatase and MoO 3-rutile systems showed that on heating MoO 3 spontaneously spreads under the influence of surface-free energy over both anatase and rutile, manifesting the phenomenon of solid/solid “wetting”. On anatase, where a crystallographic fit exists with MoO 3, an epitaxial layer is formed, exposing mainly the (010) plane with the Mo= O bonds strengthened in comparison to bulk MoO 3. In case of rutile MoO 3 platelets grow perpendicularly to the surface of rutile, exposing mainly the ( h00) and ( hk0) planes.