arXiv subjects

Kislon Voïtchovsky

Publications and source records attributed to Kislon Voïtchovsky.

5 recordsLinked to original sources

arXiv2026

Stretching and Compressing Capillary Bridges on Hydrophilic, Hydrophobic, and Liquid-infused Surfaces

Aqueous capillary liquid bridges are ubiquitous in nature and in technological processes. Here, we comparatively investigate capillary bridges formed between three distinct types of surfaces: (i) hydrophilic glass, (ii) hydrophobic dichlorodimethylsilane (DMS)-functionalized glass, and (iii) silicone-oil-infused LIS. We combine experimental measurements and computer simulations of the capillary bridge evolution upon changes in the gap size between the surfaces, deriving in each case the bridge geometry and the resulting capillary force. The results, also compared with predictions from the existing theory, follow expected trends on glass and DMS-functionalized surfaces: contact line pinning dominates the bridge behavior on glass with a characteristic stick-slip motion, whereas a pronounced advancing and receding hysteresis is observed on DMS surfaces. On LIS, the absence of pinning leads to minimal force variation, gravity-driven breaking of the bridge symmetry, and possible liquid exchange between LIS through bridge cloaking. These effects become particularly significant in asymmetric bridge configurations combining LIS and DMS surfaces, where the transfer of lubricant from LIS to DMS modifies the effective surface tension and alters bridge-surface interactions. Our systematic comparison of the capillary bridge behavior across solid and liquid interfaces with varying wettability provides a foundation for designing functional surface applications with controlled bridge-surface interactions.

cond-mat.soft↗

arXiv2025

Comparative molecular dynamics simulations of charged solid-liquid interfaces with different water models

Aqueous solid-liquid interfaces (SLI) are ubiquitous in nature and technology, often hosting molecular-level processes with macroscopic consequences. Molecular dynamics (MD) simulations offer a tool of choice to investigate interfacial phenomena with atomistic precision, but there exists a large number of water models, each optimised for a different purpose. Here we compare the ability of common water models to accurately simulate the interface between a charged silica surface and an aqueous solution containing NaCl. We first compare the bulk dielectric constant of water and its dependence on salt concentration for SPC/Fw, SPC/e, TIPS3p, H2O/DC, TIP3P-Fw, OPC3, TIP3P, TIP3P-FB, TIP3P-ST, FBA/e, and TIPS3p-PPPM, revealing large variations between models. Simulating the interface with silica for the most suitable water models (SPC/Fw, H2O/DC, TIP3-ST and TIPS3p-PPPM) show some intrinsic consistency with continuum predictions (Poisson-Boltzmann) whereby the free energy minima obtained from MD and the analytical model are in agreement, provided the latter includes the MD-determined total charge of ions in the Stern layer and dielectric constant. This consistency stands even for water models with a dielectric constant off by 100%. For salt concentrations higher than 0.21 M NaCl, the formation of random ion-ion pairs limits the reproducibility of the MD results and the applicability of the analytical method. The results highlight the applicability of the analytical model down to the nanoscale, provided a priory knowledge of the Stern layer charge is available. The findings could have significant implications for MD simulations of SLIs, especially at charged or electrified interfaces.

cond-mat.soft↗

arXiv2025

Contact-induced molecular reorganization in E. coli model lipid membranes

Biological membranes are complex, dynamic structures essential for cellular compartmentalization, signaling, and mechanical integrity. The molecular organization of eukaryotic membranes has been extensively studied, including the lipid raft-mediated lateral organization and the influence of the specific molecular interactions. Bacterial membranes were traditionally viewed as compositionally simpler and structurally uniform. Recent evidence, however, reveals that they possess significant lipid diversity and can form functional microdomains reminiscent of eukaryotic lipid rafts, despite lacking sterols and sphingolipids. Yet, the impact of unspecific physical contacts on the local molecular organization and evolution of the prokaryotic membranes remains poorly understood. Here we use a model lipid membrane mimicking the composition of Escherichia coli's inner membrane to investigate the impact of contacting substrates on the membrane nanoscale evolution, when close to its transition temperature, $T_m$. As expected, the presence of a substrate lowers the $T_m$ by $\sim$10 °C and induces a differential leaflet transition. However, it also slows down the phase transition kinetics by almost 2 orders of magnitude while simultaneously enabling a spinodal-like lateral molecular reorganization. This creates local alterations of the phase of the membrane, with the emergence of mechanically stiffer, yet still fluid nanodomains evolving over substrate-dependent timescales, consistent with a substrate-biased lipid flip-flop mechanism. The results verify previous theoretical predictions and demonstrate that a general physical mechanism -- driven by membrane-surface interactions -- can spontaneously induce lipid domain formation in bacterial membranes. This is bound to have notable consequences for its function and mechanical role, including in processes like osmotic pressure regulation.

cond-mat.soft↗

arXiv2025

Droplet Removal by Capillary Lifting

The removal of liquid droplets from solid surfaces is central to cleaning, coatings and oil recovery. Here we investigate liquid droplets capillary lifted by an immiscible working liquid. The rising working liquid triggers the formation of a capillary bridge between the solid and the air interface, which can lead to full, partial, or no droplet dewetting. Our theoretical model predicts, and experiments confirm, that the effectiveness of droplet removal can be tuned by manipulating the droplet contact angle with the solid and the interfacial tensions at play. Significantly, dewetting can be enhanced by employing working liquids with high interfacial tension, in contrast to common surface cleaning strategies where surfactants are used to reduce interfacial tension. Our findings can open new avenues for droplet manipulation with reduced resources and more sustainable environmental impact.

cond-mat.soft↗

arXiv2018

In-situ molecular-level observation of methanol catalysis at the water-graphite interface

Methanol occupies a central role in chemical synthesis and is considered an ideal candidate for cleaner fuel storage and transportation. It can be catalyzed from water and volatile organic compounds such as carbon dioxide, thereby offering an attractive solution for reducing carbon emissions. However molecular-level experimental observations of the catalytic process are scarce, and most existing catalysts tend to rely on empirically optimized, expensive and complex nano- composite materials. This lack of molecular-level insights has precluded the development of simpler, more cost-effective alternatives. Here we show that graphite immersed in ultrapure water is able to spontaneously catalyze methanol from volatile organic compounds in ambient conditions. Using single-molecule resolution atomic force microscopy (AFM) in liquid, we directly observe the formation and evolution of methanol-water nanostructures at the surface of graphite. These molecularly ordered structures nucleate near catalytically active surface features such as atomic step edges and grow progressively as further methanol is being catalyzed. Complementary nuclear magnetic resonance analysis of the liquid confirms the formation of methanol and quantifies its concentration. We also show that electric fields significantly enhance the catalysis rate, even when as small as that induced by the natural surface potential of the silicon AFM tip. These findings could have a significant impact on the development of organic catalysts and on the function of nanoscale carbon devices.

physics.chem-ph↗