A Tribological Model for Chocolate in the Mouth: General Implications for Slurry-Lubricated Hard/Soft Sliding Counterfaces

We have investigated the rheological and lubrication properties of molten chocolate samples. To this end, a series of chocolate samples having various textural/compositional features have been prepared. The rheological properties of the chocolate samples are discussed in terms of the Casson model. The lubrication properties of the molten chocolate samples have been characterized by means of pin-on-disk tribometry. For the tribo-pairs, zirconia (ZrO2) and poly(tetrafluoroethylene) (PTFE) have been used in all permutations for both slider (pin) and track (disk), providing the four tribo-pair combinations; ZrO2/ZrO2, PTFE/ZrO2, ZrO2/PTFE, and PTFE/PTFE. The results showed that both the rheological and lubrication properties of the chocolate samples are strongly influenced by the textural and compositional characteristics. The lubrication properties are further influenced by the choice of the tribo-pair. The different lubrication properties of the chocolate samples at different tribo-pairs are discussed in terms of particle behavior in the surrounding region of the inlet of the sliding tribo-pair

Sensors on Textile Fibres Based on Ag/a-C:H:O Nanocomposite Coatings

In this contribution we present a study of the vacuum deposition process of metal/plasma polymer nanocomposite thin films monitored using plasma diagnostics (optical emission spectroscopy). We investigate the electrical properties of the nanocomposite structures suitable for their application as humidity sensors. Furthermore, the film microstructure is characterized by transmission electron microscopy and electron diffraction analysis. The amount of silver in the nanocomposite is evaluated using inductively coupled plasma optical emission spectrometry and the morphology of the structured system of metal electrodes and nanocomposite films on monofilament textile fibres is visualized using scanning electron microscopy. Ageing of nanocomposite coatings and the influence of an aqueous environment on their internal structure and properties are discussed

Confined hydration in nanometer-graded plasma polymer films: Insights from surface-enhanced infrared absorption spectroscopy

To shed light on recently explored long-range surface forces generated by subsurface-confined water, the structural characteristics of water molecules penetrating into nanoporous homogeneous and nanograded siloxane plasma polymer films (PPFs) over the time scale of 24 hours are studied by surface-enhanced IR spectroscopy (SEIRAS). Chemically graded PPFs, with embedded hydrophobic-to-hydrophilic gradient, are found to significantly change the average interfacial water orientation due to a unique nanoporous morphology and silanol group coordination. Diffusion of water through the hydrophobic SiO:CH matrix creates an evolution of the coordination of matrix silanol groups, which are eventually deprotonated as soon as the hydration network connects to the aqueous environment. This occurs after -6 hours of water immersion and coincides with the change of average interfacial water orientation. Both effects are present on hydrophobic samples, but are significantly amplified by the presence of the subsurface vertical amphiphilic gradient (Vgrad), whereas enhanced water uptake in oxygen-plasma modified graded PPFs is covering such effects

Optical sensing and determination of complex reflection coefficients of plasmonic structures using transmission interferometric plasmonic sensor

The combination of interferometry and plasmonic structure, which consists of gold nanoparticle layer, sputter coated silicon oxide spacer layer, and aluminum mirror layer, was studied in transmission mode for biosensing and refractive index sensing applications. Because of the interferometric nature of the system, the information of the reflection amplitude and phase of the plasmonic layer can be deduced from one spectrum. The modulation amplitude in the transmission spectrum, caused by the interference between the plasmonic particle layer and the mirror layer, increases upon the refractive index increase around the plasmonic particles due to their coherent backscattering property. Our proposed evaluation method requires only two light sources with different wavelengths for a stable self-referenced signal, which can be easily and precisely tuned by a transparent spacer layer thickness. Unlike the standard localized surface plasmon sensors, where a sharp resonance peak is essential, a broad band plasmon resonance is accepted in this method. This leads to large fabrication tolerance of the plasmonic structures. We investigated bulk and adsorption layer sensitivities both experimentally and by simulation. The highest sensitivity wavelength corresponded to the resonance of the plasmonic particles, but useful signals are produced in a much broader spectral range. Analysis of a single transmission spectrum allowed us to access the wavelength-dependent complex reflection coefficient of the plasmonic particle layer, which confirmed the reflection amplitude increase in the plasmonic particle layer upon molecular adsorption

Seclusion of molecular layers in a confined simple liquid

We provide theoretical evidence by using molecular dynamics that a nanoconfined film of octamethylcy-clotetrasiloxane divides into manifolds of secluded thermodynamic substates. We find equivalence between the splitting into substates and the formation of molecular layers. The seclusion of layers is validated in drainage experiments using an extended surface forces apparatus (eSFA). Furthermore, per-molecule evaluations of the configurational entropy provide evidence for an increased molecular packing upon confinement. The increasing trends in both layer seclusion and molecular packing with confinement explain the exponentially increasing surface forces measured in eSFA.ISSN:2643-156