arXiv subjects

Edward Bormashenko

Publications and source records attributed to Edward Bormashenko.

At least 37 records · Page 2Linked to original sources

arXiv2017

Magnetic Field Inspired Contact Angle Hysteresis Drives Floating Polyolefin Rafts

Displacement of floating polymer (polyolefin) rafts by steady magnetic field is reported. The effect is due to the interplay of gravity deforming the water/vapor interface, contact angle hysteresis and diamagnetic properties of the liquid support. Magnetic field (ca. 0.06 T) deformed the water/vapor interface and impacted the interfacial apparent contact angle. This deformation gave rise to the propulsion force, displacing the polymer raft. The velocity of displacement of the center of mass of rafts was registered. The effect is related to the contact angle hysteresis affected by the magnetic field, enabling the change in the apparent interfacial contact angle. The semi-quantitative model of the process is suggested

physics.flu-dyn↗

arXiv2017

Paradoxical Coffee-Stain Effect Driven by the Marangoni Flow Observed on Oil-Infused Surfaces

Formation of coffee stain deposits under evaporation of droplets containing aqueous solution of salts placed on silicone-oil impregnated substrates was observed. The formation of ring-like deposits was registered for various molar concentrations of salts for the droplets of 5-300 microlitres in volume. The effect occurred when the contact line was de-pinned, and the evaporation from the edge of a droplet was stopped by the silicone oil. The formation of the coffee stain deposit is related to the soluto-capillary Marangoni flow; the influence of the thermo-capillary flow taking place in parallel is negligible.

cond-mat.soft↗

arXiv2017

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 0.05 m/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.

cond-mat.soft↗

arXiv2017

Under-liquid Self-Assembly of Submerged Buoyant Polymer Particles

The self-assembly of submerged cold-plasma-treated polyethylene beads is reported. The plasma-treated immersed millimetrically-sized polyethylene beads formed well-ordered 2D quasi-crystalline structures. The submerged floating of light polyethylene beads is possible due to the energy gain achieved by the wetting of the high-energy plasma-treated polymer surface prevailing over the energy loss due to the upward climb of the liquid over the beads. The capillary immersion attraction force is responsible for the observed self-assembly. The observed 2D quasi-crystalline structures demonstrate dislocations and point defects. Mechanical vibration of self-assembled rafts built of polyethylene beads leads to the healing of point defects. The immersion capillary lateral force governs the self-assembly, whereas the elastic force is responsible for the repulsion of polymer beads.

cond-mat.soft↗

arXiv2017

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.

cond-mat.soft↗

arXiv2017

Self-Propelling Rotator Driven by Soluto-Capillary Marangoni Flows

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.

cond-mat.soft↗

arXiv2017

Friction, Free Axes of Rotation and Entropy

Friction forces acting on rotators may promote their alignment and therefore eliminate degrees of freedom in their movement. The alignment of rotators by friction force was demonstrated by experiments performed with different spinners, demonstrating how friction generates negentropy in a system of rotators. A gas of rigid rotators influenced by friction force is considered. The orientational negentropy generated by a friction force was estimated with the Sackur-Tetrode equation. The minimal change in total entropy of a system of rotators, corresponding to their eventual alignment, decreases with temperature. The reported effect may be of the primary importance for a phase equilibrium and motion of ubiquitous colloidal and granular systems.

cond-mat.soft↗

arXiv2017

Spatial Scales of Living Cells, their Energetic and Informational Capacity and the Origin of the Arrow of Time

Physical thermodynamic and kinetic, chemical and biological reasoning restrict the spatial dimensions of living cells and confine them to between one and one hundred micrometers. Cells should necessarily be macroscopic, dissipative objects, resisting thermal fluctuations and providing sufficient informational capacity. The upper limit of spatial dimensions of cells is supplied by their ability to withstand gravity and inertia forces under reasonable deformations. The upper limit of cell dimensions is also governed by the hierarchy of characteristic time scales, inherent for mass and heat transport. For micron-scaled cells, the traffic time (namely a typical time necessary for the migration of one enzyme to another) is on the order of magnitude of a millisecond, which coincides with the characteristic time scale of a single round of the catalytic enzyme cycle. Among other important consequences the macroscopic dimensions of living cells seen as dissipative systems) give rise to the irreversibility of biological processes, demonstrating the arrow of time.

physics.bio-ph↗

arXiv2015

Sagging Ropes Demonstrate the Transversality Conditions of Variational Problems

An account of the transversality conditions of variational problems gives rise to essential results in the analysis of different physical phenomena. This powerful and elegant approach has proven to be fruitful in a diversity of variational problems with free endpoints, when the endpoints are free to slip along preset curves. We illustrate the transversality condition by the study of a heavy inextensible rope sagging both symmetrically and asymmetrically between two steering variously-shaped guide wires without friction. In this case, the transversality conditions lead to the orthogonality of the rope to the wires at endpoints of the rope, which is confirmed experimentally. Freeing the endpoints of the rope yields exact and simple analytical equations predicting the tension of the rope. Heavy ropes whose endpoints are free to slip between variously-shaped wires are discussed.

cond-mat.soft↗

arXiv2015

A Generalized Electrowetting Equation: Its Derivation and Consequences

The thermodynamics of electrowetting is treated. A general equation of electrowetting is derived from the first principles. It is demonstrated that the well-known Lippmann Equation describes a particular case of electrowetting when the radial derivative of the capacitance of the double layer is constant. The apparent contact angle of electrowetting depends on the gradient of capacity of a double layer in the vicinity of the triple line. The role of the area adjacent to the triple line in constituting the equilibrium apparent contact angle of electrowetting is emphasized.

physics.chem-ph↗

arXiv2015

Surface Tension Supported Floating of Heavy Objects: Why Elongated Bodies Float Better?

Floating of bodies heavier than the supporting liquid is discussed. Floating of cylindrical, ellipsoidal bodies and rectangular plates possessing lateral dimensions smaller than the capillary length is treated. It is demonstrated that more elongated bodies of a fixed volume are better supported by capillary forces, due to the increase in the perimeter of the triple line. Thus, floating of metallic needles obtains reasonable explanation.

physics.flu-dyn↗

arXiv2015

Phenomenological Model of Wetting Charged Dielectric Surfaces and its Testing with Plasma-Treated Polymer Films and Inflatable Balloons

Plasma treatment of polymer films results in their electrical charging, which in turn gives rise to an increase in their surface energy. The process results in pronounced hydrophilization of the polymer surfaces. A phenomenological theory relating the change in the apparent contact angle of charged solids to the surface density of the electrical charge is introduced. Partial wetting, inherent for polymer films, becomes possible until the threshold surface density of the electrical charge is gained. The predictions of the theory are illustrated by plasma-treated polymer films and inflatable latex balloons. Deflating the plasma treated latex balloons resulted in an essential increase in the surface charge density of the latex. This increase switched the wetting regime from partial to complete wetting. The kinetics of hydrophobic recovery follows the kinetics of the electrical charge leakage from the surfaces of the plasma treated polymers. The characteristic time of the surface charge leakage coincides with the time scale of the decay of the electret response of plasma treated polymer films.

cond-mat.soft↗

arXiv2015

Interpretation of Elasticity of Liquid Marbles

Liquid marbles are non-stick droplets covered with micro-scaled particles. Liquid marbles demonstrate quasi-elastic properties when pressed. The interpretation of the phenomenon of elasticity of liquid marbles is proposed. The model considering the growth in the marble surface in the course of deformation under the conservation of marbles volume explains semi-quantitatively the elastic properties of marbles in satisfactory agreement with the reported experimental data. The estimation of the effective Young modulus of marbles and its dependence on the marble volume are reported.

cond-mat.soft↗

arXiv2015

Surface Instabilities and Patterning in Liquids: Exemplifications of the "Hairy Ball Theorem"

Application of the "hairy ball theorem" to the analysis of the surface instabilities inherent for liquid/vapor interfaces is reported. When a continuous tangential velocity field exists on the surface of the liquid sample which is homeomorphic to a ball, zero velocity points will be necessarily present at the surface. The theorem is exemplified with the analysis of the instability occurring under the rapid evaporation of polymer solutions. Zero velocity points, accumulating pores, enable direct visualization of the instability. The patterning may be essentially different on the surface of a torus.

cond-mat.soft↗

arXiv2015

Elastic Properties of Liquid Surfaces Coated with Colloidal Particles

The physical mechanism of elasticity of liquid surfaces coated with colloidal particles is proposed. It is suggested that particles are separated by water clearings and the capillary interaction between them is negligible. The case is treated when the colloidal layer is deformed normally to its surface. The elasticity arises as an interfacial effect. The effective Young modulus of a surface depends on the interfacial tension, equilibrium contact angle, radius of colloidal particles and their surface density. For the nanometrically scaled particles the line tension becomes essential and has an influence on the effective Young modulus.

cond-mat.soft↗

arXiv2015

Physical Mechanisms of Interaction of Cold Plasma with Polymer Surfaces

Physical mechanisms of the interaction of cold plasmas with organic surfaces are discussed. Trapping of plasma ions by the CH2 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.

physics.plasm-ph↗

arXiv2015

Quantification and Physics of Cold Plasma Treatment of Organic Liquid Surfaces

Plasma treatment increases the surface energy of condensed phases: solids and liquids. Two independent methods of the quantification of the influence imposed by a cold radiofrequency air plasma treatment on the surface properties of silicone oils (polydimethylsiloxane) of various molecular masses and castor oil are introduced. Under the first method the water droplet coated by oils was exposed to the cold air radiofrequency plasma, resulting in an increase of oil/air surface energy. An expression relating the oil/air surface energy to the apparent contact angle of the water droplet coated with oil was derived. The apparent contact angle was established experimentally. Calculation of the oil/air surface energy and spreading parameter was carried out for the various plasma-treated silicone and castor oils. The second method is based on the measurement of the electret response of the plasma-treated liquids.

cond-mat.soft↗

arXiv2015

Self-Propulsion of Liquid Marbles: Leidenfrost-Like Levitation Driven by the Marangoni Flow

Self-propulsion of liquid marbles filled with aqueous alcohol solutions and placed on a water surface is reported. The characteristic of velocity of the marbles is about 0.1 m/s. The phenomenon of self-propulsion is related to the Marangoni solutocapillary flow caused by the condensation of alcohol, evaporated from the liquid marble, on a water surface. The Marangoni flow in turn enhances the evaporation of alcohol from marbles. Addition of alcohol to the water supporting the marbles suppresses the self-propulsion. The propulsion of liquid marbles is mainly stopped by water drag. The velocity of the center of mass of marbles grows with the increase of the concentration of alcohol in a marble. The velocity of marbles self-propulsion is independent on their volume.

physics.class-ph↗