I am a researcher in Soft Matter and enthusiastic about the rheology,  transport, and structure of soft amorphous materials. These materials include dense frictional suspensions (like Oobleck), confined colloidal suspensions (like the interior of a cell), granular materials (like sand). Few practical applications of these systems can include engineered solutions of therapeutic proteins used to treat cancer and autoimmune illnesses, and elaborately concocted slurries and pastes used for atomic precision polishing of silicon wafers and the reinforcement of bulletproof vests. The main focus of my research is a deep understanding of how and why these materials behave close to the liquid-solid transitions, such as jamming, or yielding under shear. I aim to unravel the microscopic constituents of such materials that dictate their properties and ultimately their utility to society. I also collaborate with theoretical physicists and mathematicians to explore how the mesoscale force network is affected by constraints and how that affects the bulk flow.

 

Shear-thickening suspensions

Non-newtonian behavior exhibited by dense suspensions like (Oobleck) has been a mystery for ages. The mystery has finally been unraveled. In collaboration with Romain Mari and Ryohei Seto, we have developed the numerical scheme lf_dem that marries lubrication flow with DEM. In an ongoing study, I corroborate our numerical simulations with experiments and have demonstrated the critical role of constraints in quantitatively reproducing experimental behavior.

 

 

Diffusion and structure of confined colloidal suspensions

Confined suspensions like macromolecules often exhibit slower than linear increases with time. Various hypotheses had been suggested but no numerical scheme could reproduce this behavior. We have designed a Continuum-Particle Simulation Suite COPSS. We perform Brownian Dynamics simulations using ImmersedBoundary (IB) method to represent the suspended particles. Using COPSS, we show how steric repulsion, short-and long-range hydrodynamic interactions, confinement, volume fraction and particle shape affect the structure and the diffusion.

 

Network Theory and discrete particle simulations

Previous studies have linked shear-thickening with a growing number of frictional contacts. In this project, I explore the change in the force network as the suspension shear thickens. At DST, loops begin to form that resists the applied shear. In collaboration with Lou Kondic, we use network theory measures to quantify such changes to study connections between network theory and the rheology of dense suspensions.