Roman Grynyov

Cold Radiofrequency Plasma Treatment Modifies Wettability and Germination Speed of Plant Seeds

We report the possibility to modify the wetting properties of the surfaces of a diversity of seeds including: lentils (Lens culinaris), beans (Phaseolus vulgaris) and wheat (Triticum, species C9) by cold radiofrequency air plasma treatment. Air plasma treatment leads to the dramatic decrease in the apparent contact angle. Moreover, the speed of germination and yield (germination rate) of seeds can be modified by preliminary plasma treatment. The change in the wetting properties of seeds is at least partially due to oxidation of their surface under plasma treatment. Significant growth of the peaks corresponding to the nitrogen containing groups in the mass spectra of air plasma treated seeds was registered by TOF-SIMS spectroscopy.

Interaction of cold radiofrequency plasma with seeds of beans (Phaseolus vulgaris)

Highlight The impact of cold plasma on the wetting, water absorption, and germination of beans (Phaseolus vulgaris) is reported. Plasma treatment accelerated the water absorption and germination of seeds.

Low voltage reversible electrowetting exploiting lubricated polymer honeycomb substrates

Low-voltage electrowetting-on-dielectric scheme realized with lubricated honeycomb polymer surfaces is reported. Polycarbonate honeycomb reliefs manufactured with the breath-figures self-assembly were impregnated with silicone and castor oils. The onset of the reversible electrowetting for silicone oil impregnated substrates occurred at 35 V, whereas for castor oil impregnated ones it took place at 80 V. The semi-quantitative analysis of electrowetting of impregnated surfaces is proposed.

Superoleophobic Surfaces Obtained via Hierarchical Metallic Meshes

Hierarchical metallic surfaces demonstrating pronounced water and oil repellence are reported. The surfaces were manufactured with stainless-steel microporous meshes, which were etched with perfluorononanoic acid. As a result, a hierarchical relief was created, characterized by roughness at micro- and sub-microscales. Pronounced superoleophobicity was registered with regard to canola, castor, sesame, flax, crude (petroleum), and engine oils. Relatively high sliding angles were recorded for 5 μL turpentine, olive, and silicone oil droplets. The stability of the Cassie-like air trapping wetting state, established with water/ethanol solutions, is reported. The omniphobicity of the surfaces is due to the interplay of their hierarchical relief and surface fluorination.

Elastic properties of liquid marbles

AbstractLiquid marbles are non-stick droplets coated with colloidal particles. Liquid marbles do not coalesce when pressed one to another or when colliding. The paper is devoted to the study of the quasi-elastic properties of liquid marbles under collisions. It was established that the contact time under collision is independent of the velocity of the cue marble. The liquid marble was modeled by a droplet coated by an elastic shell, representing the colloidal layer covering the marble. The elasticity of the shell is due to the capillary interaction between colloidal particles. The physical model of collisions is proposed. Pathways of viscous dissipation are discussed. Scaling laws describing the collision are derived. The proposed scaling laws governing the marbles’ collisions were verified experimentally. The contact time of the collision scales as the square root of the marbles’ volume as it occurs under bouncing of droplets. Pathways of viscous dissipation are discussed. Graphical abstractNon-coalescent collision of liquid marbles

Plasma treatment allows water suspending of the natural hydrophobic powder (lycopodium).

Lycopodium particles which are spores of the plant Lycopodium clavatum were exposed to cold oxygen and nitrogen plasma irradiation. Wetting properties of the particles changed dramatically from hydrophobic to hydrophilic. Plasma treatment allowed obtaining stable water suspensions of lycopodium. Plasma treatment did not affect the morphology of lycopodium particles. The reported results open the way for surfactants-free manufacturing suspensions of hydrophobic particles.

Self-propulsion of a metallic superoleophobic micro-boat.

The self-propulsion of a heavy, superoleophobic, metallic micro-boat carrying a droplet of various aqueous alcohol solutions as a fuel tank is reported. The micro-boat is driven by the solutocapillary Marangoni flow. The jump in the surface tension owing to the condensation of alcohols on the water surface was established experimentally. Maximal velocities of the self-propulsion were registered as high as 0.05m/s. The maximal velocity of the center mass of the boat correlates with the maximal change in the surface tension, due to the condensation of alcohols. The mechanism of the self-locomotion is discussed. The phenomenological dynamic model describing the self-propulsion is reported.

Floating of heavy objects on liquid surfaces coated with colloidal particles

Floating of heavy objects supported by water coated with colloidal hydrophobic powders was studied. Critical weight of rectangle plate (micro-boat) supported by water coated by lycopodium, polyethylene, polyvinylidene fluoride, polytetrafluoroethylene, and silicon dioxide was established. All water surfaces coated with colloidal particles demonstrated larger supporting ability of floating than clear water. This observation may be related to air trapping occurring when the object contacts with a liquid surface coated by colloidal particles and also to the strengthened pinning of the triple line in this situation. We observed essential strengthening of pinning effects, when floating rectangular plate was supported by water coated with hydrophobic particles, resulting in the enhanced supporting ability of floating.

Sagging ropes demonstrate transversality conditions of variational problems

We present an account of transversality conditions of variational problems and show how they give rise to essential results in the analysis of different physical phenomena. We find such conditions to be a powerful and elegant approach to a diverse number of variational problems with free endpoints. In this work, we illustrate such condition with the study of a heavy inextensible rope sagging both symmetrically and asymmetrically between two variously shaped, steering-guide wires without friction. In such a situation, the transversality conditions lead to the orthogonality of the rope to the wires at endpoints of the rope, which we confirm experimentally. Freeing the endpoints of the rope yields exact analytical equations that predict the tension of the rope. Heavy ropes whose endpoints are free to slip between arbitrarily shaped, steering wires are discussed.

Camphor-Engine-Driven Micro-Boat Guides Evolution of Chemical Gardens

A micro-boat self-propelled by a camphor engine, carrying seed crystals of FeCl3, promoted the evolution of chemical gardens when placed on the surface of aqueous solutions of potassium hexacyanoferrate. Inverse chemical gardens (growing from the top downward) were observed. The growth of the “inverse” chemical gardens was slowed down with an increase in the concentration of the potassium hexacyanoferrate. Heliciform precipitates were formed under the self-propulsion of the micro-boat. A phenomenological model, satisfactorily describing the self-locomotion of the camphor-driven micro-boat, is introduced and checked.