3.1.2. ICEO micropumps
Bazant and Squires (Bazant & Squires, 2004; Todd M Squires & Bazant, 2004) suggested that the ICEO flow around polarizable obstacles has the potential for liquid pumping in microchannels. Zhang et al. (Kai Zhang, Tian, & Yu, 2012) numerically demonstrated that ICEO around conducting/Janus cylinders immersed in a microchannel could be used for efficient liquid pumping. Zhang et al. (Kai Zhang, Mi, & Sheng, 2013) showed, in a numerical study, the capability of inducing the ICEO-based pumping by employing a Janus cylinder in a T-shape microchannel. Nobari et al. (Nobari, Movahed, Nourian, & Kazemi, 2016) used a similar numerical strategy but using a conducting cylinder in a T-junction to drive fluid flow in microchannels. Paustian et al. (Paustian et al., 2014) used arrays of Janus micropillars to produce a pressure gradient in a microchannel under the AC electric field. Furthermore, Wu et al. (X. Wu, Ramiah Rajasekaran, & Martin, 2016) fabricated a conical-pore polyethylene terephthalate conducting membrane immersed in an electrolyte and used it for micro pumping in microfluidics under AC electric field.
The ICEK micropumps introduced so far are categorized as ACEO micropumps where the fluid velocity in the order of 0.1-2.5 mm/s has been reported with applying DC electric signals (Lian & Wu, 2009; Yang Ng et al., 2012). Huang et al. (C.-C. Huang et al., 2010) used ACEO micropumps functioning under AC voltage (V<1.5 amplitude) to generate fluid velocity in microchannels as high as 1.3 mm/s. Among the existing ICEO micropumps, Nobari et al. (Nobari et al., 2016) demonstrated an average fluid velocity of 1750 µm/s using DC electric field with E= 300V/cm strength in a microchannel. Altogether, both ACEO and ICEO micropumps can produce a wide range of fluid velocities and are exceptionally applicable for high-speed liquid pumping in microchannels.