Effect Of Surface Hydrophilicity Research Articles

Addition of konjac glucomannan improves spraying efficiency on fruits and vegetables: Effect of surface hydrophilicity and molecular weight

Biomacromolecules have attracted interest as spraying additives due to their degradability, renewability, and non-toxicity. However, microscopic mechanism of the biomacromolecules regulating the droplet behavior on fruits and vegetables is still unclear. In this study, konjac glucomannan (KGM) was used to improve the spraying efficiency and the fresh-keeping performance of tea polyphenols solution. KGM increased effective spreading ratio on hydrophilic surfaces and retention ratio of the main droplet on hydrophobic surfaces, thus improving spraying efficiency. Computational fluid dynamics and Brown dynamics simulations were implemented to investigate KGM behaviors during droplets colliding on hydrophilic and hydrophobic surfaces. Most KGM molecules extended and then collapsed in gradually weakened shear flow. Meanwhile, on the hydrophobic surface, most KGM molecules were continuously stretched by the unstable flow field. As the KGM extended, the kinetic energy of droplets converted into elastic energy stored in the KGM, promoting the stability of droplets on target surfaces and improving the spraying efficiency. The KGM molecular weight of 3.8 × 105 Da was optimal from the point of energy storage density. This study provides more understanding of the mechanism of biomacromolecules on spraying efficiency and guidance to develop biomass spraying additives for fruit and vegetable preservation.

Effect of Surface Hydrophilicity on the Interfacial Properties of a Model Octane–Water–Silica System

We use molecular simulation to study the impact of substrate hydrophilicity on the wetting properties of water at a hydroxylated β-cristobalite (111) surface in a mother n-octane liquid. We employ ...

Effect of Surface Hydrophilicity on the Desulfurization Performance of ZnO/SiO2 Composite

Two kinds of ZnO/SiO2 composite (labled as SZ-1 and SZ-2) were synthesized by sol–gel method and characterized by X-ray diffraction (XRD) patterns, XPS (X-ray photoelectron spectroscopy) spectra and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra. Water adsorption on the prepared sample was studied by in situ DRIFT. The as-synthesized SZ-1 and SZ-2 sample have different surface property due to the various aging methods in the sample preparation processes, thus showing different results of water adsorption. The adsorption sites (Si atom in Si–O–Si bond) on the surface of SZ-2 for water molecule are occupied by the –OCH3 group and the hydrophilicity of SZ-2 is weaker, in comparison to SZ-1, which inhibits the formation of water film and ultimately decreases desulfurization performance of SZ-2. So, the desulfurization performance can be changed by altering the hydrophilicity of sorbent.

Effect of surface hydrophilicity on the supercapacitive performance of carbon paper

In this paper, the surface hydrophilicity of carbon paper was modified by use of Caro’s acid, and MnO2 electrodeposited on carbon paper (CP) or surface-modified carbon paper (SMCP) were prepared through an anodic electrochemical deposition method. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of CP, SMCP-30, SMCP-60, and SMCP-90 indicated that the peaks at 1054, 1214, 1722, and 3426 cm−1 correspond to the stretching vibrations of C–O, C–H, C=O, and –OH. Our study results show that with the extension period of oxidation treatment time, the corresponding content of these groups C–O, C–H, C=O, and –OH increased; then, their surface hydrophilic properties enhanced; and finally, their capacitances increased. This study results indicate that introducing these groups C–O, C–H, C=O, and –OH into the surface of electrode materials is an important strategy for improving their capacitances.

Influence of surface hydrophilicity on polytetrafluoroethylene flat sheet membrane fouling in a submerged membrane bioreactor using two activated sludges with different characteristics

This study focused on how membrane surface hydrophilicity affects fouling in a membrane bioreactor. A lab-scale membrane bioreactor incorporating immersed polytetrafluoroethylene flat-sheet membrane modules with different contact angles (approximately 70° and 130°) was operated using the inocula activated sludge taken from a lab reactor and from a municipal wastewater treatment plant (WWTP). The reactor also contained a polyvinylidene difluoride flat-sheet membrane module as a reference. The hydrophobicity of the WWTP sludge was higher than that of the lab-reactor sludge. Results showed that when lab-reactor sludge was used, increases in transmembrane pressure (TMP) for the hydrophobic membrane with a high contact angle occurred more rapidly than for the hydrophilic membrane with a low contact angle. In contrast, when the WWTP sludge was used, TMP increases for the hydrophilic membrane occurred more rapidly than for the hydrophobic membrane. These results indicate that the effects of surface hydrophilicity on membrane fouling depend on the hydrophobicity of the activated sludge. When the WWTP sludge was used, the hydrophobic membrane exhibited much higher cake layer resistance than did the hydrophilic membrane. Formation of a dense cake layer on hydrophobic polytetrafluoroethylene membranes may deter adhesion of foulants on membrane surfaces.

Effect of Surface Hydrophilicity on the Formation of Nafion Thin Films Inside PEMFC Catalyst Layers: A Computational Study

Structure of Nafion inside Polymer Electrolyte Membrane Fuel Cells (PEMFC) catalyst layers is suspected to have a significant impact on the electrochemical activity and transport phenomena that determine the overall cell performances. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic character of these surfaces on the structural formation of the films has not been explored in details yet. Here, we report about our Molecular Dynamic computer simulations studies of the formation of Nafion thin films in contact with unstructured continuous surfaces, characterized by their global wetting properties only. We investigate changes of morphology and nanostructure of the perfluorosulfonic acid polymer as a result of water and polymer-surface affinities. Charge and water distributions are also analyzed. Possible impact of Nafion thin film self-assembly on the actual activity properties of realistic catalysts layers is shortly discussed.

Effect of Surface Hydrophilicity on the Formation of Nafion Thin Film Inside PEMFC Catalyst Layers: A Computational Study

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Plasma surface modification of electrospun fibers for adhesion-based cancer cell sorting

Personalized cancer therapies drive the need for devices that rapidly and accurately segregate cancer cells from solid tumors. One potential sorting strategy is to segregate populations of cells based on their relative strength of adhesion. To investigate the effect of surface hydrophilicity and cell phenotype on adhesion, primary human breast skin fibroblasts and keratinocytes and MCF-7 breast cancer cells were seeded onto air and CF(4) plasma-treated nanofibers followed by exposure to three shear stresses (200, 275 and 350 dynes per cm(2)) 1 hour after inoculation. No difference in strength of adhesion was measured in either fibroblasts or keratinocytes on either plasma treated-surface: all exhibited >60% of the initial cell count after a 5 minute exposure to 350 dynes per cm(2) of shear stress. In contrast, a significant difference between relative strength of adhesion on air versus CF(4) plasma-treated surfaces was observed for MCF-7 cells: 26% and 6.6% of cells remained on the air and CF(4) plasma-treated surfaces, respectively. The ability to sort this cancer cell line from two non-cancerous primary human cells was evaluated by inoculating a mixture of all three cell types simultaneously onto CF(4) treated nanofibers followed by 1 hour of culture and exposure to 350 dynes per cm(2) shear stress. The majority of MCF-7 cells were removed (0.7% remained) while a majority of fibroblasts and keratinocytes remained adhered (74 and 57%). Post-sorted MCF-7 viability and morphology remained unchanged, preserving the possibility of post-separation and analysis. These data suggest that the plasma treatment of electrospun scaffolds provides a tool useful in sorting cancer cells from a mixed cell population based on adhesion strength.

Tuning the cellular uptake and cytotoxicity of carbon nanotubes by surface hydroxylation

Multi-walled carbon nanotubes named CNTan, CNTox, and CNTir were prepared by high temperature annealing, acid oxidation and gamma irradiation, respectively. Their morphology, metal contents and surface properties were characterized by a series of techniques. The effects of surface hydrophilicity on their cell uptake efficiency and cytotoxicity were evaluated by radio-labeling techniques and several biological assays. Results showed that the CNTs possess similar diameters, lengths and metal contents, but different surface hydrophilicity. All of these CNT samples were readily taken up by Hela cells within 2 h, and their cell uptake ratio showed a positive correlation with their surface hydrophilicity in the following order: CNTir > CNTox > CNTan. Among these CNT samples, CNTan exhibited the lowest cytotoxicity to Hela cells due to its severe agglomeration. Although the cell uptake efficiency of CNTir was greater than that of CNTox, their cytotoxicity showed no significant difference, and other factors such as serum protein coating, and incubation time could also influence their cytotoxicity. These conclusions demonstrated that surface hydrophilicity of MWCNTs could alter their cell uptake efficiency, underlining the possibility for rational design of CNT-specific surface properties for their further development in biomedical fields and a mechanistic understanding of observed CNT toxicity.

Peritoneal retention of liposomes: Effects of lipid composition, PEG coating and liposome charge

In the treatment of peritoneal carcinomatosis, systemic chemotherapy is not quite effective due to the poor penetration of cytotoxic agents into the peritoneal cavity, whereas intraperitoneal administration of chemotherapeutic agents is generally accompanied by quick absorption of the free drug from the peritoneum. Local delivery of drugs with controlled-release delivery systems like liposomes could provide sustained, elevated drug levels and reduce local and systemic toxicity. In order to achieve an ameliorated liposomal formulation that results in higher peritoneal levels of the drug and retention, vesicles composed of different phospholipid compositions (distearoyl [DSPC]; dipalmitoyl [DPPC]; or dimiristoylphosphatidylcholine [DMPC]) and various charges (neutral; negative, containing distearoylphosphatidylglycerol [DSPG]; or positive, containing dioleyloxy trimethylammonium propane [DOTAP]) were prepared at two sizes of 100 and 1000 nm. The effect of surface hydrophilicity was also investigated by incorporating PEG into the DSPC-containing neutral and charged liposomes. Liposomes were labeled with 99mTc and injected into mouse peritoneum. Mice were then sacrificed at eight different time points, and the percentage of injected radiolabel in the peritoneal cavity and the tissue distribution in terms of the percent of the injected dose/gram of tissue (%ID/g) were obtained. The ratio of the peritoneal AUC to the free label ranged from a minimum of 4.95 for DMPC/CHOL (cholesterol) 100 nm vesicles to a maximum of 24.99 for DSPC/CHOL/DOTAP 1000 nm (DOTAP 1000) vesicles. These last positively charged vesicles had the greatest peritoneal level; moreover, their level remained constant at approximately 25% of the injected dose from 2 to 48 h. Among the conventional (i.e., without PEG) 100 nm liposomes, the positively charged vesicles again showed the greatest retention. Incorporation of PEG at this size into the lipid structures augmented the peritoneal level, particularly for negatively charged liposomes. The positively charged PEGylated vesicles (DOTAP/PEG 100) had the second-greatest peritoneal level after DOTAP 1000; however, their peritoneal-to-blood AUC ratio was low (3.05). Overall, among the different liposomal formulations, the positively charged conventional liposomes (100 and 1000 nm) provided greater peritoneal levels and retention. DOTAP/PEG100 may also be a more efficient formulation because this formulation can provide a high level of anticancer drug into the peritoneal cavity and also can passively target the primary tumor.

Effect of surface hydrophilicity on the nanofretting behavior of Si(100) in atmosphere and vacuum

With an atomic force microscopy, the effect of surface hydrophilicity on the nanofretting behavior of Si(100) against SiO2 microsphere was investigated under vacuum and atmosphere conditions, respectively. The surface hydrophilicity revealed a strong effect on the motion behavior, adhesion force, friction force, and nanofretting damage of Si(100)/SiO2 pairs. The increase in the hydrophilicity of Si(100) surface could expand the stick regime of Si(100)/SiO2 pairs into a higher value of displacement amplitude. While the nanofretting ran in atmosphere, both adhesion and friction forces in the initial cycle would be larger when the Si(100) surface was more hydrophilic. However, because of the in situ chemical modification of SiO2 tip in nanofretting, they might reveal a decrease with increasing nanofretting cycles. Either in vacuum or in atmosphere, the nanofretting damage was weaker when the Si(100) surface was more hydrophobic. Because of the lack of oxygen and vapor in vacuum, the nanofretting damage on the Si(100) surface was dominated by mechanical interaction. The damage was characterized as the depression of 0.1–0.2 nm in depth on hydrophilic Si and the hillocks of 0.8–0.9 nm in height on hydrophobic Si and original Si. However, the nanofretting damage in atmosphere was much more serious, which was identified as the grooves of 8–11 nm in depth on Si(100) surfaces. Analysis indicated that even if the nanofretting damage in atmosphere was the coupled results of mechanical interaction and tribochemical reaction, the tribochemical reaction played a dominated role. These results will help us to understand the effect of surface properties on nanofretting of silicon and optimize the surface treatment technology to minimize the potential nanofretting failure of microdevices in microelectromechanical system (MEMS).

Water filling of hydrophilic nanopores

Molecular dynamics simulations of water in cylindrical hydrophilic pores with diameters of 1.5 and 3 nm were performed to explore the phase behavior and the nucleation dynamics of the confined fluid as a function of the percentage of volume filled f. The interactions of water with the pore wall were considered to be identical to the interactions between water molecules. At low water contents, all the water is adsorbed to the surface of the pore. A second phase consisting of a liquid plug appears at the onset filling for capillary condensation, f(onset)=27% and 34% for the narrow and wide pores, respectively. In agreement with experimental results for silica pores, the liquid phase appears close to the equilibrium filling f(eq) in the 1.5 nm pore and under conditions of strong surface supersaturations for the 3 nm pore. After condensation, two phases, a liquid plug and a surface-adsorbed phase, coexist in equilibrium. Under conditions of phase coexistence, the water surface density Gamma(coex) was found to be independent of the water content and the diameter of the pore. The value of Gamma(coex) found in the simulations (approximately 3 nm(-2)) is in good agreement with experimental results for silica pores, suggesting that the interactions of water with silica and with itself are comparable. The surface-adsorbed phase at coexistence is a sparse monolayer with a structure dominated by small water clusters. We characterize the density and structure of the liquid and surface phases, the nucleation mechanism of the water plug, and the effect of surface hydrophilicity on the two-phase equilibrium and hysteresis. The results are discussed in light of experiments and previous simulations.

Interaction of biodegradable nanoparticles with intestinal cells: The effect of surface hydrophilicity

The aim of the present work was to study the influence of surface hydrophilicity of biodegradable polymeric nanoparticles on cellular uptake by Caco-2 cells. Poly( d, l-lactide-co-glycolide acid) particles loaded with a fluorescent dye, 3,3′-dioctadecyloxacarbo-cyanine perchlorate (DiO), were prepared by the emulsion–evaporation process. Three batches of particles with narrow size distribution (100, 300 and 1000 nm) were produced using selective centrifugation. One set of particles was coated by adsorption of chitosan to increase the hydrophilicity of the particles. The interaction of particles with Caco-2 cells was determined by fluorescence spectroscopy and the number of particles associated with one single cell was then calculated. Interaction with cells was clearly dependant on particle size and surface hydrophilicity. Particles in the range of 100 nm presented higher interaction when compared to larger particles. Approximately 6000 uncoated particles and more than 30,000 chitosan-coated particles were quantified per cell. Confocal microscopy confirmed the spectroscopic measurements and revealed the location of the particles in the cell monolayer. Only small particles were observed intracellularly, whereas particles larger than 300 nm were associated with the apical membranes. The location of particles <300 nm appeared to be intracellular and some particles colocalized with the nucleus.

Effect of surface hydrophilicity on the confined water film

The effect of surface hydrophilicity on the water film confined within a nanogap between a smooth plate and a highly polished steel ball has been investigated. It was found that the confined water film formed the thicker lubricate film than the prediction of elastic-isoviscous lubrication theory. Experimental results indicated that the hydrophobic surface induced the thicker water film than the hydrophilic one. It is thought that the “structured” interfacial water layer is formed between the solid surfaces and the hydrophobic group induces the more ordered hydrogen-bonding network of clathrate cages which forms the thicker water film than hydrophilic one.

Effect of Surface Hydrophilicity on Charging Mechanism of Colloids in Low-Permittivity Solvents

Electrophoretic mobilities of TiO2 colloids in an apolar solvent, toluene, were measured by differential-phase optical coherence tomography (DP-OCT). An electrode spacing of 0.18 mm, made possible by optical coherence tomography with transparent electrodes, enables measurement of the electrophoretic mobility with small samples (20 μL) of highly turbid colloids at low applied electric potential to avoid electrohydrodynamic instability and electrochemical reactions. In the presence of Aerosol-OT reverse micelles, which stabilized the countercharges, the zeta potential was positive for hydrophilic TiO2 (13 mV at 90 mM AOT) and negative for hydrophobic TiO2. The magnitudes of the zeta potentials were very similar for these two types of TiO2 and decreased at the same rate with AOT concentration. For both hydrophilic and hydrophobic TiO2, a general mechanism is presented to describe the zeta potential in terms of preferential partitioning of cations and sulfosuccinate anions between the particle surface and reverse micelle cores in bulk. This preferential partitioning is governed by the hydrophilicities and extents of the particle surfaces and reverse micelle cores, as a function of surfactant and water concentration. The emerging understanding of the complex charging and stabilization mechanisms for colloids in apolar solvents will be highly beneficial for the design of novel materials.

The effect of surface hydrophilicity on the behavior of embryonic cortical neurons

The aim of this study was to investigate the interaction of mouse embryonic cortical neurons on P LLA and PLGA substrates, which were partially hydrolysed using potassium hydroxide (KOH). The chemical and topographical properties of the surfaces were characterized, and it was discovered that there was a decrease in the hydrophilicity for the P LLA with increasing concentration of KOH. This was due to chemical modifications to the surfaces of the substrates. Alternatively for the PLGA substrate, only the 0.1 M KOH treated sample had a significantly different hydrophilicity highlighting that surface erosion resulted at higher concentrations. The morphology of the neurons grown on the two substrates were compared to poly Dlysine (positive control). The neurons formed colonies on all of the substrates, but were dramatically reduced in size in the case of the 0.1 M KOH treated substrates. This finding was attributed to the increases in cell spreading and the size of the cells, as they were larger, more elongated and bipolar like those on the positive control. However, there was a significant decrease in the total number of live cells per unit area. Therefore, on these materials when there was increased cellular spreading there was significantly higher cell death. Furthermore, unlike the 0, 0.2, and 0.4 M KOH treated substrates, there was an absence of large bundles of axons that extended between colonies on the 0.1 M sample, instead exhibiting short axons that grew in free space.

Effect of surface hydrophilicity and water vapor pressure on the interfacial shear strength of adsorbed water layer

We investigated the effect of water vapor pressure and surface hydrophilicity on the tribological behavior in wearless sliding condition. Friction and interfacial shear strength of silicon surfaces with different water affinity (contact angles of &amp;lt;5°, 30°, and 85°) against a glass sphere (contact angle 40°) were examined under various water vapor pressure conditions. The friction of hydrophilic surface decreased as vapor pressure increased and the least hydrophilic surface showed stable and low friction force regardless of relative vapor pressure. However, it showed that the hydrophilic surface with high relative vapor pressure exhibited lower shear strength than a less hydrophilic surface independent of capillary effect. It was explained in terms of capillary wetting and the role of adsorbed water in contact area.

Effect of hydrophilicity on the biodegradability of polyesteramides

AbstractThe effect of surface hydrophilicity was induced from the amide units in the polyesteramide. The surface energies and compositions of the polyesteramides were studied by employing contact angle and interfacial tension measurements and ESCA analysis. Biodegradability was evaluated form various methods including activated sludge test, enzyme hydrolysis, and soil burial test, which determine the amount of evolved CO2, weight loss, and TOC values, respectively. It was found that the introduction of amide groups to the aliphatic polyester improved the biodegradability, although the increase of biodegradation rate was not directly proportional to the amide content. The biodegradability of aliphatic polyesters increased with the addition of amide functionality. Therefore, it can be concluded that the addition of appropriate contents of hydrophile enhanced the biodegradability of aliphatic polyesters as well as their physical properties. Also, the experimental results revealed the relation between hydrophilicity and biodegradability of polyesteramides. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2708–2714, 2003

Effect of surface hydrophilicity on ex vivo blood compatibility of segmented polyurethanes

The relationship between surface, bulk and ex vivo blood-contacting properties of segmented polyurethanes with various polyol soft segment was investigated. The polyols used in this study were poly(ethylene oxide), poly(tetramethylene oxide), hydrogenated poly(butadiene), poly(butadiene) and poly(dimethylsiloxane). The hard segment of these segmented polyurethanes was composed of 4,4' diphenylmethane diisocyanate and 1,4 butanediol, present at 50 wt%. An experimental polyurethane. Biostable PUR, which has shown excellent biostability, was used in this study. The segmented polyurethanes based on the hydrophobic polyols such as poly(dimethylsiloxane) and hydrogenated poly(butadiene) showed distinct microphase separation between hard and soft segments. X-ray photoelectron spectroscopy revealed the surface enrichment of the hydrophobic component at the air-solid interface. Dynamic contact angle measurements indicated that the poly(dimethylsiloxane)-based segmented polyurethane possessed a hydrophobic surface in water. The poly(dimethylsiloxane)-based segmented polyurethane had the lowest platelet adhesion among the segmented polyurethanes investigated in this study, whilst the platelet deposition on the poly(ethylene oxide)-based polymer increased with time.

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.