3.2.2. ICEO micromixer
Following the suggestion of Squires and Bazant (Bazant & Squires, 2004; Todd M Squires & Bazant, 2004) on demonstrating the capability of MVs generated around polarizable objects for ICEO mixing, Harnett et al. (Harnett et al., 2008) proved this capability numerically and experimentally. A numerical model was developed to determine optimal design parameters of ICEO mixing followed by fabricating the optimal design array of gold-coated hurdles of the triangular cross-section in microchannels under a low-frequency AC field applied on the sidewalls. A rapid increase in mixing from zero to almost perfectly mixed state (100%) in a small length scale was demonstrated (Fig. 3A ).
Wu and Li (Z. Wu & Li, 2008b) further simplified the design configuration to a triangle conducting hurdle pair on microchannel walls while enhanced the mixing performance. They optimized the system parameters and demonstrated 92% mixing efficiency. It was shown that the rectangular conducting objects placed on the microchannel walls generated the highest mixing efficiency (Fig. 3B ). Nevertheless, Jain et al. (Jain, Yeung, & Nandakumar, 2009) showed that a pair of near tight triangle hurdle present even a better mixing performance as 99% efficiency. The performance of various ICEO micromixers developed so far are highlighted in Table 2 .
The ICEK Micromixers have become popular for LOC applications due to their mixing efficiency (above 90%), simplicity and rapid mixing. However, the majority of studies are still limited to numerical studies to optimize electrodes shape and arrangement. Further experimental studies are needed to evaluate the performance of proposed mixing systems. Among various designs, the model of Daghighi and Li (Daghighi & Li, 2013) (Fig. 3C ) is attractive due to its simple structure and straightforward fabrication method (Kazemi, Nourian, Nobari, & Movahed, 2017; M. K. D. Manshadi et al., 2019; Shamloo, Madadelahi, & Abdorahimzadeh, 2017). Further experimental characterization on this design configuration would guarantee an affordable and scalable technique for high-performance ICEK mixing within microfluidics.