Robust method of manufacturing rubber waste‐based water repellent surfaces

A novel method of rubber waste recycling is presented. Shredded rubber is processed into a biomimetic superhydrophobic material demonstrating high apparent contact angles (APCAs). Wetting properties of the obtained surfaces are reported. The presented method of rubber waste processing is robust, inexpensive and promises a good potential for building industry. Copyright © 2008 John Wiley & Sons, Ltd.     

Silica-stabilized gold island films for transmission localized surface plasmon sensing

Ultrathin gold films prepared by evaporation of sub-percolation layers (typically up to 10 nm nominal thickness) onto transparent substrates form arrays of well-defined metal islands. Such films display a characteristic surface plasmon (SP) absorption band, conveniently measured by transmission spectroscopy. The SP band intensity and position are sensitive to the film morphology (island shape and inter-island separation) and the effective dielectric constant of the surrounding medium. The latter has been exploited for chemical and biological sensing in the transmission localized surface plasmon resonance (T-LSPR) mode. A major concern in the development of T-LSPR sensors based on Au island films is instability, manifested as change in the SP absorbance following immersion in organic solvents and aqueous solutions. The latter may present a problem in the use of Au island-based transducers for biological sensing, usually carried out in aqueous media. Here, we describe a facile method for stabilizing Au island films while maintaining a high sensitivity of the SP absorbance to analyte binding. Stabilization is achieved by coating the Au islands with an ultrathin silica layer, ca. 1.5 nm thick, deposited by a sol-gel procedure on an intermediate mercaptosilane monolayer. The silica coating is prepared using a modified literature procedure, where a change in the reaction conditions from room temperature to 90 degrees C shortened the deposition time from days to hours. The system was characterized by UV-vis spectroscopy, ellipsometry, XPS, HRSEM, AFM, and cyclic voltammetry. The ultrathin silica coating stabilizes the optical properties of the Au island films toward immersion in water, phosphate buffer saline (PBS), and various organic solvents, thus providing proper conditions where the optical response is sensitive only to changes in the effective dielectric constant of the immediate environment. The silica layer is thin enough to afford high T-LSPR sensitivity, while the hydroxyl groups on its surface enable chemical modification for binding of receptor molecules. The use of silica-encapsulated Au island films as a stable and effective platform for T-LSPR sensing is demonstrated.     

On the Mechanism of Floating and Sliding of Liquid Marbles

Little hovercrafts: The mechanisms of floating and sliding of liquid marbles (see picture) are elucidated. It is demonstrated that floating and sliding liquid marbles are separated from their supporting media by an air layer, resembling Leidenfrost drops. An ESEM study of the marble surface shows a rugged surface facilitating the trapping of air.

     

Patterning in rapidly evaporated polymer solutions: formation of annular structures under evaporation of the poor solvent

Patterning in the intensively evaporated polymer solutions based on polystyrene and poor solvent (acetone) was investigated. SEM and AFM studies demonstrated that annular elements of the surface topography are formed in this case, in contrast to the honeycomb patterns obtained under the evaporation of the good solvent (chloroform). The authors suggest that the theory of viscous dewetting developed by de Gennes explains the phenomenon satisfactorily.     

The lattice of idempotent binary relations

Order-theoretic properties of the complete latticeE(A) of indempotent binary relations ρ=ρ² on the given setA are investigated. The elements ρ ofE(A) are classified according to theirfixed field I(ρ)={a∈A|(a, a)∈ρ} as being either offinite type, dense, or ofmixed type. When |A|>1E(A) is a non-atomic, non-coatomic lattice in which each element is a meet of meet-irreducible elements. The elements ofE(A) which are joins of join-irreducible elements form a compactly generated complete latticeF(A) which is a join-sublattice ofE(A) consisting of all elements having finite type. The setsD(A), M(A) of elements ρ ofE(A) which are dense (i.e., satisfy ρ≠ϕ andI(ρ)=ϕ) or of mixed type (i.e., are neither dense nor of finite type) resp. are non-empty only when |A| is infinite.D(A) is a partial meet-subsemilattice ofE(A) admitting no minimal elements. The group of order automorphisms of the latticeE(A) is isomorphic toS _A ×Z ₂ and each order automorphism ofE(A) preserves inverses. Presented by B. M. Schein.     

Static and dynamic analysis of the DCB problem in fracture mechanics

A finite difference scheme for treating the static and dynamic stress fields under plane-strain conditions in the DCB, is proposed. The adequacy of the scheme is established via the static solution by comparing the results obtained numerically with those obtained experimentally. Both the numerical and experimental results are also compared with data available in the literature. Discrepancies found are explained and discussed. For the numerical scheme adjusted to handle the propagating crack problem, the results represent a situation which is close to that observed experimentally; namely, an essentially constant steady state crack propagation speed from the start, with crack length at arrest and velocity values depending on the initial conditions. In addition, the velocities predicted by the analysis are shown to be in good agreement with those reported in the literature.     

Self-assembly in evaporated polymer solutions: influence of the solution concentration

Amorphous polymers were dissolved in chlorinated organic solvents and deposited on thin horizontal substrates. The solutions with various concentrations of polymers were deposited and evaporated under ambient conditions in a slow air current. Self-assembled oriented mesoscopically scaled patterns were observed. The patterns were studied with optical and atomic force microscopy. The concentration of the solution exerts a decisive influence on the mesoscopic cell characteristic dimension. Cell dimensions grow linearly with the polymer solution concentration for all kinds of tested polymers, chlorinated solvents and substrates. The dependence could be explained by a physical mechanism, based on the mass transport instability occurring under the intensive evaporation of the solvent. In situ FTIR study of the process was performed first. It was established with FTIR spectroscopy that film porosity is not due to water droplet condensation under evaporation.