A novel micromixer based on the alternating current-flow field effect transistor

Abstract

Induced-charge electroosmosis (ICEO) phenomena have been attracting considerable attention as a means for pumping and mixing in microfluidic systems with the advantage of simple structures and low-energy consumption. We propose the first effort to exploit a fixed-potential ICEO flow around a floating electrode for microfluidic mixing. In analogy with the field effect transistor (FET) in microelectronics, the floating electrode act as a "gate" electrode for generating asymmetric ICEO flow and thus the device is called an AC-flow FET (AC-FFET). We take advantage of a tandem electrode configuration containing two biased center metal strips arranged in sequence at the bottom of the channel to generate asymmetric vortexes. The current device is manufactured on low-cost glass substrates via an easy and reliable process. Mixing experiments were conducted in the proposed device and the comparison between simulation and experimental results was also carried out, which indicates that the micromixer permits an efficient mixing effect. The mixing performance can be further enhanced by the application of a suitable phase difference between the driving electrode and the gate electrode or a square wave signal. Finally, we performed a critical analysis of the proposed micromixer in comparison with different mixer designs using a comparative mixing index (CMI). The novel methods put forward here offer a simple solution to mixing issues in microfluidic systems.

Chaotic advection and mixing by a pair of microrotors in a circular domain

“…Two interpretations are possible for the equations of advection of a fluid particle in the domain. The advection equations (7) can model a two dimensional time dependent dynamical system, where the explicit time dependence is through the positions of the N rotlets, which can be obtained from (4). Following this the trajectories of a fluid particle are allowed to self-intersect in the domain.…”

“…Following this the trajectories of a fluid particle are allowed to self-intersect in the domain. A second possible interpretation is that equations (4), (7) define a time independent 2N + 2 dimensional dynamical system, a restricted planar 3-rotlet system. We will adopt the first view and treat the advection of fluid particles as a two dimensional time dependent dynamical system, where the time dependence comes from the quasiperiodic motion of the rotors.…”

“…Various means of achieving rapid advective microfluidic mixing have been proposed over the years [4] which can be classified broadly into active and passive mixing methods. Active mixing mechanisms induce large scale motion of the fluid by directly influencing the fluid by means of mixing elements driven by force fields such as electric/magnetic or acoustic fields that compensate for the lack of fluid inertia [5][6][7] and can achieve high mixing quality especially in the vicinity of the mixing elements. Passive methods of mixing involve altering the boundary conditions of the flow so as to maximize the area of contact between fluids being mixed.…”

Subtractive Manufacturing of Microfluidic 3D Braid Mixers

“…In active mixers, an external force (e.g., magnetic, acoustic) is applied to the fluid, while passive mixers exploit diffusion and specific geometries for introducing flow folding, chaotic affects and inertial forces, and are typically simpler to design and use, at the price of reduced mixing efficiency. Recently, a novel active mixer was developed in which a fixed potential induced‐charge electro‐osmosis flow is used for mixing . Recent examples of passive mixers are a twisted 3D mixer, or a splitting and recombination micromixer with a self‐rotated contact surface.…”

Fluid Flow and Mixing Induced by AC Continuous Electrowetting of Liquid Metal Droplet

“…However, the microfabrication process involved in this approach is sophisticated and considerably challenging. Alternatively, active microfluidic mixers utilize external energy to stir or agitate the fluid flow to promote the mixing performance, such as, acoustic/ultrasonic [17,18], electro-hydrodynamic [19][20][21][22][23], magnetic [24,25], and laser techniques [26][27][28], et.al. Among them, electrokinetic flow has been extensively employed in microfluidic devices to accomplish pumping and mixing, which refers to generate the flow stream instabilities on the surface of the micromachined electrodes activated by electric field [29].…”