Research
Colloidal peanuts made in BITS-Goa
Colloidal Legos for self-assembly
To build a complex architecture in the microscale or nanoscale, we need two things: a) a set of colloidal 'Legos': micrometer or nanometer sized colloidal particles of a variety of shapes and sizes and b) a set of specific, programmable interactions that can direct the assembly process to build the desired structure. By functionalizing anisotropic colloids with designable interactions, we can obtain an enormous variety of self-assembled micro and nanostructures. We can also direct the assembly by using external fields like electric and magnetic fields or light. The aim is to assemble a complex machine from simple building blocks step by step.
Platinum-polystyrene active particle made in BITS-Goa
Active particles
Active particles show directed propulsion on being activated by chemical gradients, and/or external fields. They are out of equilibrium systems which show rich emergent behaviours and are extremely relevant from the viewpoint of building micro-swimmers for targeted drug delivery and micro-robotics. At present, we are working on active particles driven by a) chemical gradients b) electric fields c) magnetic fields and d) light. For particles driven by chemcial (ion) gradients, we use Platinum-polystyrene Janus (two faced) particles, while for magnetic or electric field driven experiments, we use a variety of anisotropic dielectric and/or magnetic colloids.
Diffusion in a binary mixture of 1 and 3 micron particles
Diffusion in complex systems
Understanding diffusion of probe particles in a soft matrix is crucial to unravelling many biological processes and interactions. Colloidal particles diffusing in a matrix of ordered or randomly arranged micropillars have been shown to exhibit Fickian, yet non-Gaussian diffusion. At present we are using micro-rheological techniques to analyze the correlated motion of probe colloids in a dense, disordered matrix of obstacles. Our aim is to apply this technique to biological systems like actin filaments and diseased cellular matrix to explore the structure and dynamics of these systems.
Machine Learning based analysis of diffusion
We use machine learning to analyze diffusion in complex, crowded environments. Diffusion of probe colloids is an extremely powerful tool to explore many biological phenomena, but a major roadblock here is often the short length trajectories of nanometer sized fast moving probe colloids. This hampers the accuracy in determining several diffusion parameters, as well as the understanding of diffusion dynamics. We train a convolutional neural network with different known models of diffusion and test it on datasets involving the motion of colloids in a varied degree of environments to find out the diffusion model for each specific case. We are also attempting to improve the efficiency of particle tracking algorithms using machine learning.
Microchannel fabrication
Biosensors for probing biomolecular interactions
We are in the process of developing a magnetic sensor for detection of biomolecules (Biomagnetic sensors). In this project, paramagnetic colloidal particles are used as the carrier probes, and are functionalized with the protein, peptide, DNA or the relevant biomolecule that we want to detect. We aim to fabricate a lab-on-a-chip system in which the sensor element consists of a specific magnetic alloy that has been demonstrated to show excellent sensitivity to magnetic fields. Magnetic microbeads functionalized with biomolecules will be detected by this chip as they flow along a microfluidic channel passing over the chip. This will be a highly sensitive, and low cost alternative to many colorimetric sensors existing in the market.
Previous work (Before joining BITS-Goa)
DNA assisted assembly of colloidal joints-hinges, sliders and ball joints.
Flexible 'colloidal molecules' with tunable valence
Self-assembled clustered nanorod arrays: enhanced X-ray and field emission
Superhydrophobicity of clustered nanord arrays
Probing weak biological interactions using nanoparticle probes
Anomalous diffusion in a matrix of obstacles
New hexagonal close packed crystallographic phases of silver