Research Projects

Dynamics of Janus Colloid Interacting with Giant Lipid Vesicles

2018 - 2021 , PhD Institute Charles Sadron, Universite de Strasbourg

Summary

The behavior of self-propelling artificial or biological particles, known as Janus colloids (Image (A)) , when they interact with cell membranes is important for understanding various processes such as microbial infections, drug delivery, and nanomaterial toxicity.

In this research, the behavior of Janus colloids was studied under both thermal equilibrium and non-equilibrium conditions when they encountered a type of cell membrane called a Giant Unilamellar Vesicle (GUV, Image (B)).

The interaction dynamics of the colloids in active and passive states were also examined using spontaneous and force-driven methods. Techniques such as centrifugation and optical tweezers were used to study the factors that influence the engulfment of a spherical colloid by a GUV. The diffusion of the colloids, both in rotation and translation, near a solid boundary and in spontaneous interaction with a GUV were also investigated. It was found that when an active Janus colloid encountered a GUV, it displayed a striking orbital motion (Image (C)). The engulfment of Janus/bare colloids by a GUV, triggered by an external force, resulted in a significant slowing of the colloids' rotational and translational diffusion, as well as a severe confinement effect. The activity of a Janus colloid was also found to be significantly hindered when it was engulfed by a GUV, However in rare cases membrane transportation was observed (Image (D)).

Keywords : Janus colloids, phospholipid, GUV, Optical Tweezers, self-propulsion, engulfment

Drainage Behavior of Liquid-Thin-Films of Polymer-Melts of Modified Silicone Polymers

Oct. 2017 - Feb. 2018 , Masters in Polymer Science and Sustainable Materials - University of Strasbourg & University of Freiburg

Foams are mixtures of gas and liquid stabilized by surfactant molecules. They are thermodynamically unstable and can be short-lived or long-lived. The stability of foams, particularly those with a longer lifetime, is of interest in industries such as firefighting and food production. The stability of foams is related to the thin films of liquid that separate the gas bubbles, and the drainage of these films can be complex and difficult to study. One way to study the stability of foam films is to use a vertical, free-standing film of liquid on a vertical frame. There has been a lot of research on the drainage of thin films made from surfactant solutions, but less attention has been paid to films made from pure polymer melts.

This study investigates the drainage behavior of modified silicone polymer melts in order to understand the role of molecular structure on the drainage and stability of free-standing vertical thin films and liquid foams made from these melts and their mixtures with solvents like polyol. The molecular structure affects physical properties such as surface tension and viscosity, which impact the drainage behavior of these films and foams. The study also analyzes the effect of surface tension and viscosity on initial film thickness and attempts to understand the deviations from conventional Frankel law. Additionally, the study looks at the use of polyol as a surfactant in mixtures with polymer melts, which have very long film lifetimes of around one day and are widely used in the solid foam industry. This research aims to provide insight into the drainage dynamics of films and foams made from these melts and their mixtures with solvents.

Linking molecular structure and thin film stability of modified silicon melts

Feb. 2018 - July 2018 , Masters in Polymer Science and Sustainable Materials - University of Strasbourg & University of Freiburg

This study analyzed the effect of various parameters on the drainage process and lifetime of films made from modified silicone polymers with different molecular structures. It was found that the thickness of different domains inside horizontal films remains constant over the drainage period, but thinner domains grow significantly, leading to a stepwise thinning behavior known as stratification. The lifetime of films made from polymers with longer side chains was found to be longer or similar to commercially available melt DBP, possibly due to the rigidity of the long polymer backbone preventing shear. Stratification in horizontal films for modified silicone polymer melts was found to require high film stability, potentially arising from structures at the surface with a molecular structure length scale. The stratification length scale was found to be 16 nm for one type of molecule, but 12 nm when analyzed using reflectivity data, possibly due to repulsive forces between layers coming into close proximity. Further analysis is needed to fully understand these findings.

Hydrodynamic studies of a Pulsed Packed column

Jan. 2014 - April 2014, Chemical Engineering, Institute of chemical Technology Mumbai.

The project studied the effect of pulsation on packed columns used for liquid-liquid extraction in single-phase and multiphase systems. Liquid-liquid extraction is a method of separating compounds based on their relative solubility in two immiscible liquids, and has a variety of applications including nuclear reprocessing, ore processing, production of fine organic compounds, perfume processing, and the production of vegetable oils and biodiesel. This work was conducted under the supervision of Dr. VK Rathor, Professor and Head of the Department of Chemical Engineering at ICT- Mumbai.