2012 12th International Conference on Control, Automation and Systems Oct. 17-21, 2012 in ICC, Jeju Island, Korea 1. INTRODUCTION Mixing of two fluids is one of the most significant phenomena in the µTAS (micro-Total Analysis System) devices and in the microfluidic processes. Many biomechanical and biomedical systems need mixing processes for their development. For instance, enzyme reaction [1], protein folding [2] DNA extraction and purification [3] are the processes involve mixing for their reactions. Moreover, since governed regime in micro-fluid flows is laminar flow with very low Reynolds number, the progression of mixing and the design for mixers may be not easy. Therefore, there are lots of tries and researches in this field, to create a good mixer which can be useful in any case; also it does not affect other components of micro-fluid flows. In order to carry out this idea, many tries have been done. Chang and Yang presented a micro-channel with patterned blocks in it which it could enhance mixing efficiency of the system and helped to reduce the length of micro-channel, also they utilized heterogeneous zeta potential surface to get better mixing[4]. In 2008 Fu studied the influence of coating surface of micro-channel with and without nano-film. By this method, heterogeneous zeta potential on the boundaries generate different Helmholtz- Smoluchowski boundary velocity which it created some disturbances in the fluid flow and therefore mixing process got better[5]. These two micro-mixers were classified as passive micro-mixer. Passive micro-mixers are groups of mixers which by manipulating the structure and geometry of the mixers passively the mixing efficiency can be increased. In contrast with this category, active micro-mixers are another classification for mixer that the process of mixing can control directly by varying parameters like voltages applied to the electrodes, zeta potential of boundaries, AC electric field applied to the fluid flow and etc. Lue and his colleagues offered an active micro-mixer with perturbation in intensity of electric field applied to the micro-channel[6]. Quan and Bau in 2002, presented their chaotic electro-osmotic stirrer which by changing the zeta potential on the boundaries can produce chaotic advection in the micro-channel [7]. Based on their works Chabreyrie and their colleagues in 2011, by utilizing a technique which it targeted the parameter values at which complete mixing occurred. They applied their technique to a time periodic, two-dimensional electro-osmotic flow with temporally and spatially varying Helmholtz-Smoluchowski boundary velocity [8]. The induced-charge electrokinetic (ICEK) phenomena are novel region of research in microfluidics. In the last decade there were many attempts of using these phenomena in micro-devices such as, pumps and mixers. Zhao and Bau Theoretically showed that Induced-Charge-Electro-Osmotic-Flow (ICEOF)-based micro-mixing could be improved by broken symmetries [9,10] topological shape optimization [11], or by the utilizing polarisable hurdles in dielectric micro-channels[12]. To get better view of ICEOF-based micro-mixing, study of review paper on induced-charge Control of mixing process in a novel micro-mixer Behzad Otrodi 1 , Mohammad Eghtesad 2 , Mojatba Mahzoon 3 , Saeid movahed 4 1 Department of Mechanical Engineering, Shiraz, Fars, 71348-13668; Iran (Email:Behzad_otrodi@ymail.com) 2 Department of Mechanical Engineering, Shiraz, Fars, 71348-13668; Iran (Email:eghtesad@succ.shirazu.ac.ir)* Corresponding author 3 Department of Mechanical Engineering, Shiraz,Fars, 71348-13668; Iran (Email:mahzoon@succ.shirazu.ac.ir) 4 Department of Mechanical and Mechatronics Engineering, University of Waterloo, Canada (Email:smovahed@uwaterloo.ca) Abstract: There are many different types of micro-mixers which have been designed to enhance mixing efficiency of fluid flow in micro-channels. The output of micro-channels integrated with micro-mixers in some cases may need to be in a certain range. In this article we design a new type of micro-mixer by utilizing conductive surfaces and walls with variable zeta potential. Interaction of the induced charged electro-kinetic (ICEK) phenomenon (due to existence of conductive surfaces) and producing diverse electro-osmotic boundary velocity (because of presence of walls with changeable zeta potential) together lead to increase mixing efficiency of the system significantly. Numerical simulation are performed to analyze the system and the results show that by using this micro-mixer with different zeta potential applied to walls, we can have a wide range of mixing efficiency between 30% and 85%. Moreover, we applied a fuzzy logic controller (FLC) to the system to manage the percentage of mixing efficiency within this range. This controller based on desired mixing efficiency; determine the amount of zeta potential on each wall and thus we can reach the amount of required mixing efficiency. Keywords: Fuzzy Control, Micro-Mixers, Feedforward-Feedback controller, Induced charge. 337