Abstract: In this talk, I will explore the dynamics of synthetic colloidal spheres driven either by external fields or by self-generated active forces in both Newtonian (viscous) and viscoelastic fluids. Unlike purely viscous fluids, viscoelastic media possess long stress-relaxation times (on the order of seconds), erasing any clear separation of timescales. As a result, the particle dynamics are dominated by pronounced memory effects, giving rise to striking behaviors—such as orders-of-magnitude enhancement of the rotational diffusion coefficient and persistent circular trajectories—that have no analogue in Newtonian environments. These phenomena, captured by a minimal theoretical model incorporating fluid memory, reflect the generic, non-Markovian nature of such baths, independent of the specific fluid or driving mechanism. I will conclude by presenting related findings on biological active matter.

About the Speaker: Dr. Narinder a Postdoctoral Fellow at Technische Universität Dresden, Germany, in the group of Prof. Elisabeth Fischer-Friedrich, within the Physics of Life cluster. Currently, â€‹his research investigates the non-equilibrium dynamics in the actin cortex of living cells, with emphasis on time irreversibility, entropy production, and effective temperature regulation—representing an interdisciplinary bridge between soft matter physics and cellular biophysics.

​He completed​ his B.Sc. (Honors) in Physics from Sri Venkateswara College, University of Delhi (2012–2015).​ Thereafter, went to Germany for MS and pursued a Master of Science in Physics at the University of Stuttgart, Germany (2015–2017). Continuing â€‹his further studies in Germany, â€‹he â€‹d​id his Ph.D. in experimental statistical Physics at the University of Konstanz, Germany (2018–2022), supervised by Prof. Clemens Bechinger.​ His doctoral thesis entitled “Active Particles moving in complex environments,” explored the dynamics of light activated self-propelled colloidal particles moving in and viscoelastic fluid and geometrically constrained conditions.

After completing his Ph.D., â€‹he joined the Indian Institute of Science (IISc), Bengaluru with the Institute of Eminence Postdoctoral Fellow (June 2022–December 2023) at the Department of Physics and Centre for Nano Science and Engineering (CeNSE), working with Prof. Ambarish Ghosh. â€‹His research focused on the dynamics of colloidal rods in viscoelastic media and led to both a peer-reviewed publication and an Indian patent for a technique involving magnetic probes to determine rheological fluid properties.

​Looking forward to your active participation.