Water forms ordered hexagonally symmetric structures (snow crystals) in its solid state, however not as liquid. Typically, mists and clouds are composed of randomly moving small droplets lacking any ordered structure. Self-organized hexagonally patterned microdroplet clusters over locally heated water surfaces have been recently observed. However, many aspects of the phenomenon are far from being well understood including what determines droplets size, arrangement, and the distance between them. Here we show that the Voronoi entropy of the cluster tends to decrease indicating to their self-organization, while coupling of thermal effects and mechanical forces controls the stability of the clusters. We explain the balance of the long-range attraction and repulsion forces which stabilizes the cluster patterns and established the range of parameters, for which the clusters are stable. The cluster is a dissipative structure similar to self-organized Rayleigh–Bénard convective cells. Microdroplet formation plays a role in a variety effects from mist and clouds to aerosols. We anticipate that the discovery of the droplet cluster phenomenon and its explanation will provide new insights on the fundamental physical and chemical processes such as microdroplet role in reaction catalysis in nature as well as new tools for aerosol analysis and microfluidic applications.

Physical mechanisms of the interaction of cold plasmas with organic surfaces are discussed. Trapping of plasma ions by the CH 2 groups of polymer surfaces resulting in their electrical charging is treated. Polyethylene surfaces were exposed to the cold radiofrequency air plasma for different intervals of time. The change in the wettability of these surfaces was registered. The experimentally established characteristic time scales of the interaction of cold plasma with polymer surfaces are inversely proportional to the concentration of ions. The phenomenological kinetic model of the electrical charging of polymer surfaces by plasmas is introduced and analyzed.

Electrowetting of silicone oil lubricated PC + EC substrates. (A) U = 0 V; (B) U = 55 V.

Low‐density polyethylene, polypropylene, and polycarbonate were exposed to cold air plasma treatment. The decay of electret response, hydrophobic recovery, and mechanical relaxation of polymers were studied experimentally. The three‐exponential decay kinetic model was used for the treatment of mechanical and electret responses. The characteristic time scales of mechanical and electret responses turned out to be very close. The “longest” relaxation time, extracted from the experimental study of the hydrophobic recovery, was also close to the corresponding characteristic time spans of electret and mechanical responses. The kinetics of surface processes taking place in polymers is controlled by the mobility of their functional groups, represented by the bulk relaxation spectra. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 198–205

The self-propelled, longstanding rotation of the polymer tubing containing camphor continuing for dozens of hours is reported. The rotator is driven by the solutocapillary Marangoni flows owing to the dissolution of camphor. The phenomenological model of self-propulsion is suggested and verified. Scaling laws describing the quasi-stationary self-propulsion are proposed and tested experimentally. The change in the surface tension, arising from the dissolution of camphor and driving the rotator is estimated as 0.3 mN/m.