Wetting of isotropic mickrotextures formed on the surface of glass and aluminium

The paper studies the wetting of aluminum and glass surfaces with disordered roughness created by technologically simple methods: chemical deposition with simultaneous self-organization of nanoparticles on microprotrusions and valleys, as well as the application of thin coatings using polymer-dispersed systems with polymodal particle size distribution. Super-hydrophobic coatings with an edge wetting angle of 160–170° and a wetting hysteresis of no more than 10° on electrochemically nanostructured aluminum, processed by the dispersion with the polymodal distribution of aerosil microparticles, silicon oxide nanoparticles SiDB and carbon nanocomposite SHDB (Nanosintal, Belarus) in fluorinated varnish. The regularities of changes in the wetting angle of silicate glass with the coating of the same varnish with small additives were established, showing its significant growth with an increase in the content of aerosil microparticles and a decrease in the lacquer concentration. The increase in the content of SiDB and SHDB does not significantly affect the contact angle, but it significantly reduces the hysteresis of its wetting, which gives the glass the effect of “lotus”.

Estimation of anti-icing properties of coatings

The proposed composition for anti-icing coating of metal structures. The composition contains as the filler used aerosil brand R 972 with a density of 2360 kg / m3, particle size of 16 nm and a specific surface 12000 m2 / kg. Silicone resin SILRES® MSE 100 with a 10% concentration was used as a binder. The degree of hydrophobicity was estimated by the value of the wetting angle. In order to characterize the anti-icing properties of the coatings, we used the static and dynamic (advancing and retreating) wetting angle, as well as wetting hysteresis, for which we measured the angles of leakage, and the angles of drift from. Studies of the dynamics of freezing drops on the surface were performed using a TESTO 875-1 thermal imager. It is shown, that the hysteresis of wetting of the superhydrophobic surface based on the developed composition is 3.7 degrees. The critical angle of rolling drops of water from an inclined surface is determined. In the study of the kinetics of freezing of a drop of water on a metal surface, an uneven distribution of temperature on the surface of a drop of water is observed. The process of freezing drops is multistage. In the initial period, there is a transfer of heat from the surface to a drop of water. This stage is followed by the process of freezing the drop, which is manifested in the movement of the freezing front from the substrate upwards.

Mechanical phase inversion of Pickering emulsions via metastable wetting of rough colloids

We exploit the surface-roughness-induced wetting hysteresis of individual colloids to achieve Pickering emulsions undergoing phase inversion upon mechanical energy inputs.

Wetting hysteresis induced by nanodefects

Wetting of actual surfaces involves diverse hysteretic phenomena stemming from ever-present imperfections. Here, we clarify the origin of wetting hysteresis for a liquid front advancing or receding across an isolated defect of nanometric size. Various kinds of chemical and topographical nanodefects, which represent salient features of actual heterogeneous surfaces, are investigated. The most probable wetting path across surface heterogeneities is identified by combining, within an innovative approach, microscopic classical density functional theory and the string method devised for the study of rare events. The computed rugged free-energy landscape demonstrates that hysteresis emerges as a consequence of metastable pinning of the liquid front at the defects; the barriers for thermally activated defect crossing, the pinning force, and hysteresis are quantified and related to the geometry and chemistry of the defects allowing for the occurrence of nanoscopic effects. The main result of our calculations is that even weak nanoscale defects, which are difficult to characterize in generic microfluidic experiments, can be the source of a plethora of hysteretical phenomena, including the pinning of nanobubbles.

Cryogenic Focused Ion Beam Milling for Studying Wetting Hysteresis Behavior

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.