Numerical models for the evaluation of the contact angle from axisymmetric drop profiles: a statistical comparison.

Axisymmetric drop shape analysis (ADSA) is a well-established methodology for estimating the contact angle value and the surface tension of liquids starting from sessile drops images. It consists of an iterative procedure in which a best fit between a theoretical axisymmetric Laplacian curve and an experimental drop profile is performed. When only an evaluation of the geometric contact angle value is needed, a similar numerical approach can be adopted by using simpler algebraic models in place of a Laplace profile, thus allowing more straightforward implementations and shorter computation times.

Contact angle analysis on polymethylmethacrylate and commercial wax by using an environmental scanning electron microscope.

The environmental scanning electron microscope (ESEM) represents one of the most exciting breakthroughs in electron microscopy since the invention of the electron microscope. Its ability to observe uncoated and hydrated samples enhances the possibility for investigating the wettability of surfaces at a microscopic level; by varying the relative vapour pressure or the temperature inside the chamber, it is possible to condense water drops on a micron scale. A large problem in measuring contact angles by ESEM is that the observation angle is not parallel or perpendicular to the surface; thus, the study of the droplets profile using the common algorithms such as spherical approximation or axisymmetric drop shape analysis (ADSA) is not possible, because only a spherical cap shape is commonly observed.

Effects on interfacial properties and cell adhesion of surface modification by pectic hairy regions.

Polystyrene Petri dishes, aminated by a plasma deposition process, were surface modified by the covalent linking of two different enzymatically modified hairy regions (HRs) from pectin containing, for example, rhamnogalacturonan-I and xylogalacturonan structural elements. The two polysaccharide preparations share the same structural elements of apple pectin, but the relative amounts and lengths of the neutral side chains present differ. Surface analysis by X-ray photoelectron spectroscopy, contact angle measurement, and atomic force microscope (AFM) force-separation curves was used to characterize the effects on surface chemistry and interfacial forces of the surface modification process.

Correct use of the contact angle in the evaluation of the protective action induced from polymer coating on the stone.

The control of the protective efficacy obtained on the stone by treatments with polymers is commonly performed through the measure of the static contact angle as it is described by the norm UNI 10921. However this approach does not allow an easy interpretation of the results, because of the porosity and of the heterogeneity of the stone surface, which represent an obstacle to the analysis. Moreover the commonest interpretation of this technique can often bring to important errors.