Electrophoresis in dilute polymer solutions

Non-Newtonian effects on the slip and mobility of a self-propelling active particle

“…polymers with low molecular weight () and radius of gyration smaller than the interaction layer thickness which is typically (Sharifi-Mood et al 2013). The qualitative insights obtained through such continuum models can also be extended to the cases of larger polymers as their segments would experience strong shear, which can result in modification of the dynamics in the interaction layer (Li & Koch 2020). We also assume the solute molecules, inside and outside the interaction layer, to follow Fickian diffusion with constant diffusivity.…”

“…Interestingly, there have been similar observations in the context of electrophoresis. Recently, Li & Koch (2020) reported that, in weakly viscoelastic fluids, polymer elasticity in the inner region changes the electrophoretic particle into a puller-type squirmer: the strong shear flow in the double layer causes the polymers to be stretched tangentially, resulting in a pulling flow at the front and rear end, and a pushing flow from the sides. Since electrophoretic and diffusiophoretic mechanisms share qualitative similarities (such as strong shear inside the thin layer), it is plausible that the effects of elasticity, observed in electrophoresis, emerge in diffusiophoresis as well.…”

“…Khair, Posluszny & Walker (2012) demonstrated that the modification in slip due to shear-thinning can alter the mobility of an electrophoretic particle and the flow field around it. Very recently, through the use of various continuum-level rheological models (Oldroyd-B, Giesekus, FENE-P, and FENE-CR), Li & Koch (2020) showed that the electrophoretic particle (similar to a neutral squirmer in Newtonian fluid) behaves like a puller-type squirmer at low Weissenberg numbers. Such behaviour arises primarily due to the elastic effects in the thin electrical double layer.…”

“…These studies show that the high shear rate inside the thin layer generates significant polymer extension and deformation which needs to be accounted for in the prediction of phoretic motion. Motivated by these recent developments in the context of electrophoresis (Khair et al 2012; Zhao & Yang 2013; Li & Koch 2020), we aim to investigate the modification due to complex rheology in both the slip and mobility of a self-propelling active particle.…”

Electrophoretic motion of a non-uniformly charged particle in a viscoelastic medium in thin electrical double layer limit

“…This phenomenon has been a prominent area of research over decades owing to its wide gamut of applications such as colloid science (Ohshima 2006; Khair, Posluszny & Walker 2012) and separation of particles (Ghosal 2006), DNA analysis (Khair & Squires 2009), gel electrophoresis (Babnigg & Giometti 2004), particle deposition (Besra & Liu 2007) among many others. In many instances, electrophoretic motion occurs in complex media (Ramautar, Demirci & de Jong 2006), such as bio-fluids (Babnigg & Giometti 2004; Kremser, Blaas & Kenndler 2004), polymeric solutions (Li & Koch 2020; Barron, Sunada & Blanch 1995) etc., whose constitutive behaviours show strong deviations from the Newtonian paradigm. These facets have been progressively becoming important in recent times (Berli 2010; Bandopadhyay & Chakraborty 2012 b ; Bandopadhyay, Ghosh & Chakraborty 2013; Zhao & Yang 2013; Ghosh & Chakraborty 2015; Ghosh, Chaudhury & Chakraborty 2016), because of their key roles in medical diagnostics (Madou et al.…”