Titanium implant surface etching has proven an effective method to enhance cell attachment. Despite the frequent use of hydrofluoric (HF) acid, many questions remain unresolved, including the optimal ...etching time and its effect on surface and biological properties. The objective of this study was to investigate the effect of HF acid etching time on Ti topography, surface chemistry, wettability, and cell adhesion. These data are useful to design improved acid treatment and obtain an improved cell response. The surface topography, chemistry, dynamic wetting, and cell adhesiveness of polished Ti surfaces were evaluated after treatment with HF acid solution for 0, 2; 3, 5, 7, or 10 min, revealing a time-dependent effect of HF acid on their topography, chemistry, and wetting. Roughness and wetting increased with longer etching time except at 10 min, when roughness increased but wetness decreased. Skewness became negative after etching and kurtosis tended to 3 with longer etching time. Highest cell adhesion was achieved after 5-7 min of etching time. Wetting and cell adhesion were reduced on the highly rough surfaces obtained after 10-min etching time.
Texturization of surfaces is usually advantageous in biomaterial engineering. However, the details of the textured surfaces can be more determining on cell adhesion and proliferation, rather than ...their roughness degree. Titanium is extensively used as a dental implant material in the human body. In this paper, the effect of four surface treatments on commercially pure titanium has been evaluated. These treatments were polishing (pTi); hydrofluoric acid (HF) etching (eTi); Al
2O
3 blasting (bTi); Al
2O
3 blasting
+
HF etching (beTi). Roughness and fractal dimensions were obtained from atomic force microscopy. Wettability was measured using water sessile drops. Morphology and surface chemical composition were analyzed with scanning electron microscopy and energy dispersive X-ray (EDX). MG-63 cell cultures were performed at different times (180
min, 24
h, 48
h, 72
h). Lowest roughness was found in pTi samples followed by eTi, bTi and beTi samples. Etching generated surfaces with the highest fractal dimension and negative skewness. Young contact angles were similar except for pTi and bTi surfaces. Silicon and aluminum traces were found in pTi and bTi samples, respectively. Cell adhesion (≤24
h) was greater on bTi and beTi surfaces. After 48
h, cell proliferation, mediated by specific morphologies, was improved in eTi samples followed by beTi surfaces. For the same surface chemistry, cell growth was driven by topography features.
It is well-established that the equilibrium contact angle in a thermodynamic framework is an “unattainable” contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of ...the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid–liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie–Baxter equations accordingly or for the surface energy evaluation.
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•The most-stable contact angle is postulated as experimental equilibrium contact angle.•Monitoring the susceptibility of a sessile drop against a mechanical stimulus•Two different stimuli may be used with sessile drops: vibration and tilting.•The most-stable contact angle completes the description of physically realizable configurations.
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In this work, we studied the wettability of hydrophobic surfaces fabricated with three different materials (PTFE, PDMS and paraffin wax) over a wide range of roughness. We estimated ...the Advancing, Receding and Most-Stable contact angles and we identified the transition from a homogeneous wetting regime (Wenzel) to a hybrid wetting regime (Cassie-Baxter). Using a modified Cassie-Baxter equation which considers the chemical heterogeneity of the samples, we were able to determine the solid area fraction within the contact area. This way, we designed a methodology to identify the superhydrophobic degree of rough-hydrophobic surfaces.
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•The freezing delay of drops on solid surfaces is still a matter of controversy.•Surface roughness and drop geometry are considered as key factors.•The role of heat transfer driven by ...phase change phenomena is usually ignored.•Here, we studied the impact of roughness, contact angle and thermal conductivity.•The best efficiency was observed for smooth, hydrophobic and conductive materials.
Elucidating the predominant factors for the freezing delay of surfaces is still a matter of discussion and controversy. Freezing delay is explained in literature through the classical nucleation theory. It postulates that freezing delay of a surface is enhanced with low surface roughness and sessile drops of high contact angles. However, since surface roughness influences the wetting properties, a better understanding of how each factor affects the freezing delay requires to uncouple both effects systematically. This is indeed the reason why certain contradictions are found in literature. Besides, some works report that further factors, such as the surface-to-drop heat transfer might also be important. In this work, we analyzed independently how drop geometry, surface roughness and thermal conductivity influence the freezing delay of solid surfaces at unsaturated conditions. Our results show that the drop contact angle and surface roughness strongly influences the freezing delay on conductive and insulating materials. Although its importance is minor, we also found that conductive materials delay freezing more efficiently than insulating materials. In conclusion, our results point out that conductive, smooth and hydrophobic surfaces are the most efficient surfaces to delay freezing in unsaturated environments.
Quasi-static experiments using sessile drops and captive bubbles are the most employed methods for measuring advancing and receding contact angles on real surfaces. These observable contact angles ...are the most easily accessible and reproducible. However, some properties of practical surfaces induce certain phenomena that cause a built-in uncertainty in the estimation of advancing and receding contact angles. These phenomena are well known in surface thermodynamics as stick–slip phenomena. Following the work of Marmur (Marmur, A. Colloids Surf., A 1998, 136, 209–215), where the stick–slip effects were studied with regard to sessile drops and captive bubbles on heterogeneous surfaces, we developed a novel extension of this study by adding the effects of roughness to both methods for contact angle measurement. We found that the symmetry between the surface roughness problem and the chemical heterogeneity problem breaks down for drops and bubbles subjected to stick–slip effects.
•Dynamic adsorption curves reveal higher adsorption rates of NaTC than NaGDC.•Adsorption isotherms reveal different conformational regimes for NaTC and one conformational regime NaGDC.•The different ...conformational regimes imply different dilatational response: two maxima of the dilatational modulus for NaTC and one maximum for NaGDC.•Desorption profile of NaGDC shows higher desorption ratio than NaTC.•Conformational regimes suggest surface complexation.
Bile salts (BS) are bio-surfactants which constitute a vital component in the process of fat digestion. Despite the importance of the interfacial properties in their biological role, these have been scarcely studied in the literature. In this work, we present the adsorption–desorption profiles of two BS (NaTC and NaGDC) including dilatational rheology. Findings from this study reveal very different surface properties of NaTC and NaGDC which originate from different complexation properties relevant to the digestion process. Dynamic adsorption curves show higher adsorption rates for NaTC and suggest the existence of various conformational regimes in contrast to NaGDC which presents only one conformational regime. This is corroborated by analysis of the adsorption isotherms and more in detail by the rheological behaviour. Accordingly, the dilatational response at 1Hz displays two maxima of the dilatational modulus for NaTC as a function of bulk concentration, in contrast to NaGDC which displays only one maximum. The desorption profiles reveal that NaTC adopts an irreversibly adsorbed form at high surface coverage whereas NaGDC fully desorbs from the surface within the whole range of concentrations used. Analysis of the adsorption–desorption profiles provides new insight into the surface properties of BS, suggesting a surface complexation of NaTC. This knowledge can be useful since through interfacial engineering we might control the extent of lipolysis providing the basis for the rational design of food products with tailored digestibility.
It is known that non-ionic surfactants and phospholipids provide large protection in emulsions against lipase-induced destabilization as compared to proteins, even in the presence of bile salts. In ...relation to this, the aim of this study is to probe the ability of two surfactants of industrial interest, poloxamer Pluronic F68 (non-ionic) and Epikuron 145V (phospholipid), to modify the adsorption of lipases at an oil–water interface under the physiological conditions existing in the duodenum. We have designed an experimental procedure by means of a pendant drop film balance equipped with a subphase exchange technique, which allows sequential adsorption of the compounds. This allows the investigation of the interfacial behaviour of lipase in the presence and absence of surfactant. According to this experimental approach, the lipase is added directly into the subphase only after the surfactant has been adsorbed onto the oil–water interface. We have used interfacial dilatational and shear rheology techniques to characterise the interfacial layers. The results suggest that Pluronic F68 reduces the interfacial activity of lipase more efficiently than Epikuron 145V. Furthermore, it seems that Pluronic F68 affects the accessibility of the lipase to the oil–water interface, even in the presence of the bile salts. These results may have applications in the development of novel strategies to rationally control lipid digestion in the diet.
The ability of two surfactants of industrial interest, Pluronic F68 (non-ionic) and Epikuron 145V (phospholipid), to modify the adsorption of lipases at an oil–water interface under the physiological conditions of the duodenum has been investigated by means of a pendant drop tensiometer equipped with a subphase exchange technique and the interfacial dilatational and shear rheology. The additional information provided by these experiments could be potentially used in the control of lipid digestion.
Currently, there is no conclusive evidence regarding the global equilibrium condition of vibrated drops. However, it is well-known that vibration of sessile drops effectively reduces the contact ...angle hysteresis. In this work, applying a recent methodology for evaluating the most-stable contact angle, we examined the impact of the type of excitation signal (random signal versus periodical signal) on the values of the most-stable contact angle for polymer surfaces. Using harmonic signals, the oscillation frequency affected the postvibration contact angle. Instead, the white noise signal enabled sessile drops to relax regardless of their initial configuration. In spite of that, the values of most-stable contact angle obtained with different signals mostly agreed. We concluded that not only the amount of relaxation can be important for relaxing a sessile drop but also the rate of relaxation. Together with receding contact angle, most-stable contact angle, measured with the proposed methodology, was able to capture the thermodynamic changes of “wetted” polymer surfaces.
Towards super-nonstick aluminized steel surfaces Ruiz-Cabello, F. Javier Montes; Rodríguez-Criado, J.C.; Cabrerizo-Vílchez, M. ...
Progress in organic coatings,
August 2017, 2017-08-00, 20170801, Letnik:
109
Journal Article
Recenzirano
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•A novel strategy to produce superhydrophobic surfaces on aluminized steel is proposed.•It enhances the nonstick properties of conventional polymer-filler coated aluminized steel ...surfaces used in cookware industry.•This strategy is based on a texturing process (sandblasting and/or soft-acid etching) followed by a hydrophobic film deposition using Teflon or silane.•This strategy is capable to provide superhydrophobicity to this material without damaging the aluminum protective layer on aluminized steel.
One of the main challenges in cookware and baking industry is the fabrication of enhanced nonstick coatings including two main features: highly hydrophobic, resistant and durable. In general, life-long release coatings are prepared with a polymer-filler composite of several microns thickness deposited on food-compatible metals such as aluminum, stainless steel or aluminized steel, as the dimensions and functionality of the product.
In this work we present several routes to fabricate water-repellent surfaces on aluminized steel as alternative to current nonstick coatings but with enhanced release properties and high durability. For this purpose, we explored two different strategies to directly create hierarchical texture on aluminized steel surfaces: sandblasting in combination to acid etching and single acid etching. The rough metal surfaces were further hydrophobized by using two different organic coatings: a Teflon film and a silane monolayer. The release properties were quantified through the study of the adhesion of water drops by means of sliding angle and contact angle measurements. We identified the most appropriate texturing process by assessing a balance between the water repellency properties and the lowest damage caused on the metal surface. This damage was quantified through thickness loss measurements of the aluminum layer. The durability of the samples was analyzed with Scotch-peeling test and next, with sliding angle measurements. We analyzed the roughness and morphology of the surface textures by contact profilometry and FE-SEM. The surface chemical composition was also analyzed by EDX. Our results pointed out to that the most durable repellent surfaces were those ones silanized. The combination of sandblasting and acid etching and the hydrophobization process with silane molecules enable to fabricate super-nonstick coatings on aluminized steel of high durability.
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