Abstract
In this investigation, the transient electroosmotic flow of multi-layer immiscible viscoelastic fluids in a slit microchannel is studied. Through an appropriate combination of the momentum equation with the rheological model for Maxwell fluids, an hyperbolic partial differential equation is obtained and semi-analytically solved by using the Laplace transform method to describe the velocity field. In the solution process, different electrostatic conditions and electro-viscous stresses have to be considered in the liquid-liquid interfaces due to the transported fluids content buffer solutions based on symmetrical electrolytes. By adopting a dimensionless mathematical model for the governing and constitutive equations, certain dimensionless parameters that control the start-up of electroosmotic flow appear, as the viscosity ratios, dielectric permittivity ratios, the density ratios, the relaxation times, the electrokinetic parameters and the potential differences. In the results, it is shown that the velocity exhibits an oscillatory behavior in the transient regime as a consequence of the competition between the viscous and elastic forces; also, the flow field is affected by the electrostatic conditions at the liquid-liquid interfaces, producing steep velocity gradients, and finally, the time to reach the steady-state is strongly dependent on the relaxation times, viscosity ratios and the number of fluid layers.
Highlights
Microfluidics is a term that is used in fields of science with miniaturized systems where fluids are used as key components of control and sensing [1]
To validate the performance of the semi-analytical solution found in this work for the transient velocity distribution, a comparison was made with two investigations reported by the scientific community, considering the transport of Newtonian and Maxwell fluids, respectively
In the research carried out by Yang et al [10], they model an electroosmotic flow of an aqueous 1:1 electrolyte (NaCl) in a slit microchannel with the following physical properties: a density of ρ = 998 kg m−3, a viscosity of η=0.90×10−3 kg m −1 s−1, a relative electrical permittivity of r = 80, and a concentration of 10−4 M, at a temperature of T = 298 K; the microchannel size and the wall zeta potential were set at 2H = 10 μm and 50 mV, respectively
Summary
Microfluidics is a term that is used in fields of science with miniaturized systems where fluids are used as key components of control and sensing [1]. Applications cover the areas of mechanics, biology, chemistry, and medicine, seeking to improve technologies to preserve human health and improve the quality of life [4]. In this context, and to cover the different applications above mentioned, the electroosmotic flow has emerged as an electrokinetic phenomenon to transport fluids in microsystems. The electroosmosis represents the movement, due to an applied electric field, of an electrolyte solution relative to a stationary charged surface [5] This transport method has been theoretically studied since many years ago in small channels with Newtonian fluids, as the early works carried out by Burgreen and Nakache [6] and Rice and Whitehead [7]. Since and until now, the scientific community has continued studies on the electroosmotic flow behavior using Newtonian [8,9,10,11,12] and non-Newtonian fluids [13,14,15,16,17,18,19], addressing emerging issues regarding the rheology of the fluids and ionic concentrations, channel geometry, wall zeta potentials effects, boundary slip effects, among other topics, and their implications on the flow characteristics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
