arXiv subjects

V Madhurima

Publications and source records attributed to V Madhurima.

4 recordsLinked to original sources

arXiv2019

1D roughness driven depinning of breath figures on PDMS

The influence of surface constraints on the self-assembly of liquid droplets is investigated. A semi-quantitative explanation for large scale pattern formation consisting of small scale closely arranged droplets inside the large scale distorted ring of droplets is presented in this paper. The scale at which the influence of constraints become dominant is also determined in this study. It is seen that the underlying roughness has a larger impact than the nature of polymer on pore size. Comparative studies of pore patterns formed on smooth and constrained substrates are reported. The simulated energy minimized shape of the droplets on smooth and constrained substrates are obtained using \textit{Surface Evolver}.

cond-mat.soft↗

arXiv2018

Controlling breath figure patterns on PDMS by concentration variation of ethanol-methanol binary vapors

In this paper, the self-assembly of condensed droplets on smooth and constrained surfaces under saturated vapor atmosphere of ethanol and methanol binary system is reported. Hexagonally ordered array of pores are obtained on smooth surfaces with saturated vapors of binary liquids without the assistance of any additives. The results show that the addition of small amount of ethanol to methanol plays a role very similar to that of surface active agents in inducing the formation of regular droplet array. The effect of constraints on self-assembled droplet pattern such as movement of contact line and depinning of contact line is also investigated. It is observed that the pore size, pore shape, pore depth and ring diameter are influenced by the atmosphere of binary vapors in addition to the commonly held attribution to the surface tension of the solvent. Contact angle studies of the patterned substrates showed hydrophobicity with very high adhesiveness to water and Wenzel's state of wetting.

cond-mat.soft↗

arXiv2016

Study of complex properties of binary system of ethanol-methanol at extreme concentrations

At low concentrations of methanol in ethanol-methanol binary system, the molecular interactions are seen to be uniquely complex. It is observed that the ethanol aggregates are not strictly hydrogen-bonded complexes; dispersion forces also play a dominant role in the self- association of ethanol molecules. On the addition of small amount of methanol to ethanol, the dipolar association of ethanol is destroyed. The repulsive forces between the two moieties dominate the behavior of the binary system at lower concentration of methanol. At higher concentration of methanol (> 30%), the strength and extent (number) of formation of hydrogen bonds between ethanol and methanol increases. The geometry of molecular structure at high concentration favors the fitting of component molecules with each other. Intermolecular interactions in the ethanol-methanol binary system over the entire concentration range were investigated in detail using broadband dielectric spectroscopy, FTIR, surface tension and refractive index studies. Molecular Dynamics simulations show that the hydrogen bond density is a direct function of the number of methanol molecules present, as the ethanol aggregates are not strictly hydrogen-bond constructed which is in agreement with the experimental results.

physics.chem-ph↗

arXiv2016

De-pinning of contact line of droplets on rough surfaces

The present study reports the formation of self-assembled droplet pattern on the PDMS polymer coated over grooved side of DVD under saturated vapours of alcohols. Comparison of the results with breath figures formed over unconstrained side of DVD is made. Four different environments namely methanol, ethanol, 2-propanol and n-butanol are used for the analysis. It is observed that the pattern formation occurs with methanol and ethanol vapours and not with 2-propanol and n-butanol. The difference is pattern formation with different alcohols is attributed to the variation in chain length and the presence of hydrophobic groups in alcohols, as given by Traube's rule. The distortion of patterns over constrained surface is attributed to the depinning of contact lines.

cond-mat.soft↗