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In this talk, I am going to discuss semiflexible colloidal filaments, which are analogous to semiflexible
polymers. Semiflexible polymers are ubiquitous in nature, such as they work as building blocks of the
cytoskeleton, and due to the ability to form ordered structure they also play an important role in various
materials. We aim to understand the single semiflexible chain’s dynamics and conformational changes in
different conditions. Our colloidal filaments provide us with the freedom to visualize the dynamics and
conformational changes as well as individual monomers in real-time under simple optical microscopy.
We assemble the colloids into permanent colloidal linear chains by different methods and we study (1) the
dynamical behaviors of passive and catalytically active chains and have demonstrated that the diffusion of
passive Brownian chains does not depend on chain flexibility, whereas the diffusion of "active" colloidal
chains is a function of their flexibility. (2) We prepare thermos-responsive colloidal chains by adhering
poly N-isopropyl acrylamide micro-gel particles to the colloidal surface and show that chains with
intermediate flexibility exhibit the formation of helical structures upon heating. (3) We also
experimentally investigate the propulsion and configurational changes of colloidal chains due to flow
(EHD, induced charge electro-osmosis) symmetry breaking. We control the flows around the colloids by
changing the surface of the colloids and demonstrate that contractile flow induces more conformational
changes, whereas extensile flows around the colloids lead to enhanced propulsions. (4) We aim to
understand the size, shape, and configurational changes of long polymeric chains under bacterial bath. We
use a home-built setup to control the environment of the sample chamber and regulate the activity of the
bath. In real-time under microscopy, we observe the chain's dynamical and conformational changes. By
controlling the concentration and the activity of the bacterial suspension we observe ‘softening’ of the
colloidal chains, the effective bending rigidity of the chains ranging over an order of magnitude. |