(6fc) Role of Species Transport on the Stability of Interfaces

Stability of and transport across interfaces are important in a diverse class of problems ranging from stability of inorganic fluid-fluid interfaces in lubricants to transport across bio-interfaces that are vital for life. In many situations, such as in foams or in the blood brain barrier – interfacial transport and stability are closely intertwined. My research seeks to establish a fundamental understanding of this class of important problems through experiments, theory and simulations.

Research Experience:

Stability of fluid-fluid interfaces in the presence of evaporation, Department of Chemical Engineering, Stanford University (advised by Prof. Gerald Fuller)

My dissertation research broadly explores the role of evaporation driven mass transport on the stability of systems having liquid-liquid interfaces utilizing a combination of experiments and theory. Utilizing optical measurement tools such as interferometry and shadowgraphy, we are studying two problems that clearly highlight the dual role of evaporation on the stability of such systems. The first problem concerns the stability of deleterious non-aqueous lubricant foams. Lubricants are often a mixture of various oils. When foams are generated in such lubricants, our experiments reveal that the heterogeneous evaporation of lubricant components lead to stabilizing Marangoni flows that dramatically enhances foam stability. The results from this study help the lubricant industry account for the foam stabilizing effects of lubricant blending and compensate for such effects through the addition of adequate ‘antifoam’ additives. Current research in this project focuses both on establishing thresholds on the adequate quantity as well as the mechanism of antifoam additives. The second problem concerns hydrodynamic instabilities in drying polymer films. Our experiments reveal that evaporation can drive Rayleigh-Taylor instabilities with the film leading to undesired heterogeneous redistribution of polymers. Theoretically we show that the onset time of the instability is bound by two power law scalings in polymer concentration dictated by the relative importance of diffusion. These results can be used to develop film drying protocols that avoid Rayleigh Taylor instabilities. Current research in this project looks at evaporation driven instabilities in phase seperated polymer solutions.

Selected Publications:

• Mossige*, V. Chandran Suja*, G.G. Fuller et.al, Evaporation driven Rayleigh-Taylor Instability in Aqueous Polymer Solutions, submitted (2019). *equal contribution
• V. Chandran Suja, G.G. Fuller et.al, Evaporation Induced Foam Stabilization in Lubricating Oils, PNAS (2018).
• V. Chandran Suja, J. F. Frostad, G.G. Fuller Impact of Compressibility on the Control of Bubble-Pressure Tensiometers, Langmuir (2016).

Selected Awards:

• Universite Paris-Saclay Outgoing Mobility scholarship (2015)
• Charpak Scholarship (2014-2015)
• Chemical Engineering Outstanding TA award (2019)
• Centennial TA award (2019)

Teaching Interests:

As a formally trained chemical engineer, I am excited and qualified to teach core coursework in thermodynamics, fluid mechanics and transport phenomena. I also look forward to leveraging my interdisciplinary research experience and interests to develop and teach electives in interfacial dynamics, soft matter physics, non-Newtonian fluid dynamics, and/or applied mathematics for chemical engineers.

Teaching Experience:

• Rheology short course in Beijing , Teaching Assistant (2019)
• Fluid Mechanics (ChemEng 120A), Teaching Assistant and Guest Lecturer (2018, 2019) s