Our Science

We are an experimental group who like to infer the physics of soft materials by directly watching the phenomenon or process. To do this, we become photographers and record videos of the interested process using various microscopic techniques. We use microscopes that can resolve sizes ranging from micrometers "optical microscopy" to nanometers  "electron microscopy." We then use image processing and deep learning techniques to distill quantitative structural and dynamical information from the time series of images. 

Naively, we make complex fluids and solids with simple materials like emulsions, colloids and polymers and use statistical mechanics along with image processing as tools to discover rules of various physical phenomena.  Our studies are typically aimed at discovering novel phases, assemblies, and materials at the mesoscale or providing insights into different physical phenomena. 

Current and Past Research Projects

Active colloids are tiny particles that move on their own, exhibiting self-propulsion and complex behaviors. Their collective motion often mirrors the dynamics seen in living systems, like swarming insects or flocking birds, making them a fascinating platform for exploring the physics of life-like behavior. We use active colloidal systems both as models to study non-equilibrium statistical physics and as analogs for understanding living matter. At the same time, uncovering the rules that govern their motion opens the door to designing novel, autonomous, and functional materials.

Some of the current projects include designing and studying swimming wiggly filaments and motile patchy particle systems to uncover how fluid-structure interactions drive behaviors in active matter, guiding the design of adaptable, responsive materials. 

Colloidal filaments are colloidal particles strung into chains. These filaments form excellent model systems to understand the dynamics of active and passive filamentous materials.

For imaging soft systems like polymers and proteins, resolution beyond existing optical techniques are necessary. While conventional electron microscopy in dry state is used to get insights into the structural information up to Angstrom resolution, most soft materials’ behavior and properties are governed by the surrounding fluid and hence understanding dynamical features is imminent. So, how do we study soft matter structure and dynamics in the presence of a liquid at nanaoscale? We use a liquid cell in tandem with an electron microscope.

We use "glass" (the material) everyday in some form or the other. While engineering glasses is well know, the physics of its formation is still a puzzle. The transition from liquid to glass is unique since it is not associated with any structural changes. However, the viscosity and the relaxation times diverge as the material approaches glass. It is still unclear whether the glass transition is a phase transition, or it is a kinetic arrest. 

Our past projects have been using colloidal glass forming liquids, to distinguish between the disparate theories of the glass transition.

Our selected publications in this area: Nature Physics, 2015, 11,403; Nature Commun., 2014, 5, 4685; Physical Review E, 2014, 89,062308.

Moving forward we are working towards designing and understanding active glasses.

Commonly observed crystals are typically polycrystalline in nature. Defects like grain boundaries give polycrystalline materials their interesting mechanical properties. Hence, controlling defect microstructure has always been an important aspect of materials science and engineering. However, observing defect dynamics in real time is quite challenging in atomic crystals owing to the small sizes and fast dynamics of individual atoms. So, we use colloidal crystals as models to understand defect microstructure and its evolution.