3.2. ICEK micromixers
Rapid and homogeneous mixing of different solutions in microfluidics is vital for numerous LOC applications, such as biochemical reactions (S.-J. Kim, Wang, Burns, & Kurabayashi, 2009), drug delivery (X. Jia et al., 2016), biological agent detection (Cho, Chung, Kim, Jung, & Seo, 2015), and DNA hybridization (R. H. Liu, Lenigk, & Grodzinski, 2003). Diffusion is the primary mechanism of fluid mixing in microscale due to the low convective mass transfer (M. K. D. Manshadi et al., 2019). Various types of passive and active micromixers have been developed to increase the contact surface area (interface) and reduce the mixing path, therefore enhancing the mixing in microchannels (Lee, Chang, Wang, & Fu, 2011; Lee, Wang, Liu, & Fu, 2016). Electrokinetic micromixers have demonstrated to be one of the most effective mixing methods in microfluidics where their performance is dependent on mixing time, length, and index (Lee et al., 2011; Rashidi, Bafekr, Valipour, & Esfahani, 2018). ICEK electrokinetic-based micromixers, in specific, have shown their potential for active mixing in microchannels due to their high flexibility, controllability, and easy usage (Harnett, Templeton, Dunphy-Guzman, Senousy, & Kanouff, 2008; Rashidi et al., 2018). The generated MVs around polarizable surfaces (electrodes or objects) increase chaotic movement in the electrolyte and therefore induce notable mixing. Similar to ICEK micropumps, two primary categories of ACEO and ICEO have shown high performance for microfluidic applications and are discussed below.