On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing

Abstract

Induced-charge electroosmosis has attracted lots of attention from the microfluidic community over the past decade. Most previous researches on this subject focused on induced-charge electroosmosis (ICEO) vortex streaming actuated on ideally polarizable surfaces immersed in electrolyte solutions. Starting from this point, we conduct herein a linear asymptotic analysis on nonlinear electroosmotic flow next to leaky dielectric blocks of arbitrary electrical conductivity and dielectric permittivity in harmonic AC electric fields, and theoretically demonstrate that observable ICEO fluid motion can be generated at high field frequencies in the vicinity of nearly insulating semiconductors, a very low electrical conductivity, of which can evidently increase the double-layer relaxation frequency (inversely proportional to the solid permittivity) to be much higher than the typical reciprocal RC time constant for induced double-layer charging on ideally polarizable surfaces. A computational model is developed to study the feasibility of this high-frequency vortex flow field of ICEO for sample mixing in microfluidics, in which the usage of AC voltage signal at high field frequencies may be beneficial to suppress electrochemical reactions to some extent. The influence of various parameters for developing an efficient mixer is investigated, and an integrated arrangement of semiconductor block array is suggested for achieving a reliable mixing performance at relatively high sample fluxes. Our physical demonstration with high-frequency ICEO next to leaky dielectric blocks using a simple channel structure offers valuable insights into the design of high-throughput micromixers for a variety of lab-on-a-chip applications.

Electroosmotic flow of non‐Newtonian fluids in a constriction microchannel

“…For fluid electroosmosis, iDEP devices have thus far been almost entirely restricted to work with Newtonian fluids . The insulating structures can cause electrothermal flow and/or induced charge electroosmotic flow due to the amplified Joule heating in the fluid around them and their own electrical polarization, respectively . However, many of the chemical (e.g., colloidal suspensions and polymer solutions) and biological (e.g., blood, saliva, and DNA solutions) fluids are actually complex, exhibiting non‐Newtonian characteristics .…”

Asymmetrical Induced Charge Electroosmotic Flow on a Herringbone Floating Electrode and Its Application in a Micromixer

“…When immersed in an electrolyte, the electrical floating conductor attaching to the microchannel bottom wall becomes polarized with an electric field applied on the driving electrodes, causing the metal strip to become negatively charged near the anodic side while positively charged on the other side. The mobile charge carriers in the electrical double layer (EDL) interact with the tangential component of the imposed electric field and move to the oppositely neighboring charged electrode, inducing induce charge electroosmosis (ICEO) [ 35 , 48 , 58 , 59 ]. The ICEO enables a pair of symmetrical microvortices above the electrode surface, yielding liquid circulation motion.…”

Buoyancy-Free Janus Microcylinders as Mobile Microelectrode Arrays for Continuous Microfluidic Biomolecule Collection within a Wide Frequency Range: A Numerical Simulation Study

“…Recently, we have also investigated a time-averaged ICEO vortex flow adjacent to the sharp-corner-singularity of leaky dielectric blocks of both a finite conductivity and permittivity in external time-harmonic AC forcing [81]. In this paper, under the thin layer approximation and small double-layer voltage drop, we deal with the IDL as a thin capacitive skin induced at the dielectric wall/electrolyte interface by the applied AC field.…”