On the use of viscous micropumps for the transport of thixotropic fluids

Abstract

A cylinder rotating in an off-center position across a microchannel is known to generate a net flow for highly viscous Newtonian fluids. The mechanism is also known to be a viable option for the transport of viscoelastic or viscoplastic fluids albeit with a slight drop in performance. In the present work, the applicability of this mechanism is numerically investigated for the transport of (inelastic) time-dependent fluids obeying the structural-based Quemada model. By numerically solving the equations of motion, it is predicted that viscous micropumps can be used for the transport of thixotropic fluids although the obtained numerical results suggest that there exists a critical thixotropy number (a dimensionless number related to the fluid’s natural time) at which the flow rate is at its lowest value. It is shown that the critical thixotropy number can be avoided from the response of the fluid by properly choosing the geometrical parameters of the device. The general conclusion is that viscous micropumps can be deemed as an efficient mechanism for the transport of thixotropic fluids in microfluidic systems provided that the thixotropy number is sufficiently small, i.e., the fluid is strongly thixotropic. The device is predicted to be more suitable for anti-thixotropic fluids.