Molecular organization of the tear fluid lipid layer

The tear fluid protects the corneal epithelium from drying out as well as from invasion by pathogens. It also provides cell nutrients. Similarly to lung surfactant, it is composed of an aqueous phase covered by a lipid layer. Here we describe the molecular organization of the anterior lipid layer of the tear film. Artificial tear fluid lipid layers (ATFLLs) composed of egg yolk phosphatidylcholine (60 mol %), free fatty acids (20 mol %), cholesteryl oleate (10 mol %), and triglycerides (10 mol %) were deposited on the air-water interface and their physico-chemical behavior was compared to egg-yolk phosphatidylcholine monolayers by using Langmuir-film balance techniques, x-ray diffraction, and imaging techniques as well as in silico molecular level simulations. At low surface pressures, ATFLLs were organized at the air-water interface as heterogeneous monomolecular films. Upon compression the ATFLLs collapsed toward the air phase and formed hemispherelike lipid aggregates. This transition was reversible upon relaxation. These results were confirmed by molecular-level simulations of ATFLL, which further provided molecular-scale insight into the molecular distributions inside and dynamics of the tear film. Similar type of behavior is observed in lung surfactant but the folding takes place toward the aqueous phase. The results provide novel information of the function of lipids in the tear fluid

Atomic layer deposition and characterization of vanadium oxide thin films

In this study, VOx films were grown by atomic layer deposition (ALD) using V(NEtMe)4 as the vanadium precursor and either ozone or water as the oxygen source. V(NEtMe)4 is liquid at room temperature and shows good evaporation properties. The growth was investigated at deposition temperatures from as low as 75 °C, up to 250 °C. When using water as the oxygen source, a region of constant growth rate (ca. 0.8 Å/cycle) was observed between 125 and 200 °C, with the ozone process the growth rate was significantly lower (0.31–0.34 Å/cycle). The effect of the process conditions and post-deposition annealing on the film structure was investigated. By varying the atmosphere under which the films were annealed, it was possible to preferably form either VO2 or V2O5. Atomic force microscopy revealed that the films were smooth (rms <0.5 nm) and uniform. The composition and stoichiometry of the films were determined by X-ray photoelectron spectroscopy. Conformal deposition was achieved in demanding high aspect ratio structure

Atomic layer deposition and characterization of vanadium oxide thin films

In this study, VOx films were grown by atomic layer deposition (ALD) using V(NEtMe)4 as the vanadium precursor and either ozone or water as the oxygen source. V(NEtMe)4 is liquid at room temperature and shows good evaporation properties. The growth was investigated at deposition temperatures from as low as 75 °C, up to 250 °C. When using water as the oxygen source, a region of constant growth rate (ca. 0.8 Å/cycle) was observed between 125 and 200 °C, with the ozone process the growth rate was significantly lower (0.31–0.34 Å/cycle). The effect of the process conditions and post-deposition annealing on the film structure was investigated. By varying the atmosphere under which the films were annealed, it was possible to preferably form either VO2 or V2O5. Atomic force microscopy revealed that the films were smooth (rms <0.5 nm) and uniform. The composition and stoichiometry of the films were determined by X-ray photoelectron spectroscopy. Conformal deposition was achieved in demanding high aspect ratio structure

Compressed Metal Powders that Remain Superhydrophobic After Abrasion

Superhydrophobic “lotus effect” materials are typically not sufficiently robust for most real world applications because their small surface features are both easily damaged and vulnerable to fouling. Here, a method for preparing a new type of superhydrophobic (θ > 162°) composite material by compression of superhydrophobic metal particles is reported. This material, which has no natural analogue, has low-surface-energy microstructures extending throughout its whole volume. Removing its outer layer by abrasion or cutting deep into it does not result in loss of superhydrophobicity because it merely exposes a fresh portion of the underlying superhydrophobic material. The high contact angle is therefore retained even after accidental damage, and vigorous abrasion can be used to restore hydrophobicity after fouling