Polyelectrolyte layer grafting effect on the rotational electroosmotic flow of viscoplastic material

Abstract

Due to growing importance of study of bio-fluids in rotational microfluidic platforms, discussion of flow of viscoplastic materials in such situations becomes very important. Bio-fluids also generally flow in soft channel microfluidic environment and therefore studying the effect of softness of channels on flow of such viscoplastic bio-fluids becomes critical. We, in the present study, investigate the effect of the rotation of the channel and yield stress of the fluid on the flow of viscoplastic material in a soft microchannel for three constitutive models viz. Bingham, Casson and Herschel–Bulkley models. It is found that the soft grafted layer, the channel rotation and the fluid yield stress play vital roles in determining the flow behaviour. We find that that larger rotational speeds tend to destabilize the flow. We also find the critical rotational speed for which secondary flow magnitude is maximum. We also find that this non-linear interaction between rotation of channel and fluid yield stress leads to the generation of multiple yield planes within the flow domain. Our study will help in obtaining good designs of rotational microfluidic platforms for studying bio-fluids with yield stress.