The role of Near-Wall Drag Effect on the Dynamics of a Tethered Polymer under Shear Flow

Einat Chetrit, Chemical Engineering, BGU University, Ashkelon, Israel

G. Nir¹, E. Chetrit², A. Vivante³, Y. Garini⁴ and R. Berkovich⁵

Local interactions at the polymer-surface interface under external shear flow conditions govern the dialogue that ultimately affects the dynamical macroscopic behavior. This kind of interaction is Interactions of such kind are associated with numerous phenomena, ranging from melt fracture to DNA interactions with the nucleus envelope, all of which are manifestation of visco-elastic instabilities. Simplified descriptions of such systems, in terms of force acting on a polymer in the vicinity of a surface have proven to be valuable for modeling. However, crucial features of such systems still remain elusive, partially due to challenges in decoupling the intrinsic diffusion of a polymer from surrounding affects, such as, surface proximity. Here we used a Tethered Particle motion setup with a microfluidic device to monitor the time evolution of single dsDNA molecules, as a model polymer, under shear flow, for probing near-wall effects. The proximity of the tethered spherical body under flow parallel to a wall results in an increased drag force, and reduction of velocity. We introduce an explicit model that incorporates near–wall hydrodynamic effects (Faxén corrections) with the polymer nonlinear elasticity. Applying this model to the relaxation dynamics of the chain, we probe through the internal diffusion of the system and the near–wall drag effect on the Faxén correction factors. Together with characteristic-time analysis subjected to various flow rates, we show through the interplay between the external flow and the near-wall viscous restraining effects, that the latter is prominent to the tension along the chain until a turnover that takes place at a relative extension of ~0.8 of the chain.