Analytica Chimica Acta 763 (2013) 28–37 Contents lists available at SciVerse ScienceDirect Analytica Chimica Acta jou rn al hom epa ge: www.elsevier.com/locate/aca Numerical study of a novel induced-charge electrokinetic micro-mixer Yasaman Daghighi, Dongqing Li ∗ Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 h i g h l i g h t s ◮ A novel micro-mixer is developed based on induced-charge electroki- netic (ICEK). ◮ Produced vortices around the electri- cally conducting particle enhance the mixing. ◮ Designed micro-mixer is very effi- cient and fast. ◮ This micro-mixer is simple to fabri- cate for lab-on-a-chip applications. ◮ Mixing efficiency is studied as a func- tion of applied electric field. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 8 February 2012 Received in revised form 27 September 2012 Accepted 4 December 2012 Available online 13 December 2012 Keywords: Induced-charge Conducting particle Electrokinetic flow Micro-mixer Vortices a b s t r a c t A novel micro-mixer based on the induced-charge electrokinetic motion of an electrically conducting particle is proposed and numerically demonstrated in this paper. For most microfluidic applications, it is desired to mix different streams of solutions rapidly in a continuous flow mode. Therefore, in this work, we consider a mixing chamber containing an electrically conducting particle and the mixing chamber is located in the middle of a microchannel. Vortices are generated around the electrically conducting particle in an aqueous solution due to the interaction of the applied electric field and the induced surface charge on the particle. These vortices will enhance significantly the mixing of different solutions around the particle. The effectiveness of mixing the two streams entering the mixing chamber is numerically studied as functions of the applied electric field. Excellent mixing can be achieved in this system under two perpendicularly applied electric fields. The proposed micro-mixer is simple and easy to be fabricated for lab-on-a-chip applications. © 2012 Elsevier B.V. All rights reserved. 1. Introduction For many lab-on-a-chip (LOC) applications, mixing different solutions to obtain a homogeneous mixture in a short period of time is very important. However, effectively mixing different liq- uids or mixing biological samples with reagents in microchannels is not a simple task. Poor mixing is generally due to the nature of laminar flow in the microchannels where the mixing depends on the molecular diffusion. In the literature, various methods were ∗ Corresponding author. Tel.: +1 519 888 4567x38682. E-mail address: dongqing@mme.uwaterloo.ca (D. Li). proposed for enhancing the mixing processes by disrupting the laminar flow field in the microchannels. Some methods focused on designing special geometries of microchannels to enhance the mixing [1,2]. Using sequential grooves on the channel base [3] or inserting non-conducting obstacles into the microchannel [4] is another group of mixing methods. Coleman and Sinton [5] pro- posed a micro-mixer using a sequential injection connected to an expansion chamber. Biddiss et al. [6] demonstrated that the hetero- geneous surface charge patterns along the walls can induce local flow circulations to improve the mixing performance. Some micro- mixers use an active miniature flow stirrer [7,8]. However, using the stirrer introduces moving parts in the micro-systems and has many drawbacks and fabrication difficulties. 0003-2670/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aca.2012.12.010