Particle and Flow Manipulation via Electrokinetics in Micro/Nano-fluidics
Various particle manipulations including enrichment, movement, trapping, separation, and focusing by floating electrodes attached to the bottom wall of a straight microchannel under an imposed DC electric field have been experimentally demonstrated. In contrast to a dielectric microchannel possessing a nearly uniform surface charge, the metal strip (floating electrode) is polarized under the imposed electric field, resulting in a non-uniform distribution of the induced surface charge with a zero net surface charge along the floating electrode’s surface, and accordingly induced-charge electroosmotic flow near the metal strip. The induced induced-charge electroosmotic flow can be regulated by controlling the strength of the imposed electric field and affects both the hydrodynamic field and the particle’s motion. By using a single floating electrode, charged particles could be locally concentrated in a section of the channel or in an endreservoir and move toward either the anode or the cathode by controlling the strength of the imposed electric field. By using double floating electrodes, negatively charged particles could be concentrated between the floating electrodes, subsequently squeezed to a stream flowing in the center region of the microchannel toward the cathodic reservoir, which can be used to focus particles. After observing that particle enrichment and reversal of motion naturally occurs by using a single floating electrode, local control electrodes around floating electrodes have been added and the concentration, motion, and position of the concentrated particles in microfluidic channels have been controlled.
Then a low-voltage electroosmotic (EO) micropump based on an anodic aluminum oxide (AAO) nano-porous membrane with platinum electrodes coated on both sides has been designed, fabricated, tested, and analyzed. The maximum flow rate of 0.074 ml min-1 V-1 cm-2 for a membrane with porosity of 0.65 was obtained. A theoretical model, considering the head loss along the entire EO micropump system and the finite electrical double layer (EDL) effect on the flow rate, is developed for the first time to analyze the performance of the EO micropump. The resulting flow rate increases with increasing porosity of the porous membrane and the ratio of the radius of the nanopore to the Debye length.
Eren Yalcin, Ph.D
Sinan Eren Yalcin obtained his Ph.D. degree from Old Dominion University, Norfolk, VA, USA in May 2011. After graduation he worked as a post-doctoral research associate around 2 years at RWTH Aachen University in Germany. From December 2012, he is working at Ozyegin University at BSH funded project titled ‘Synthesis, Characterization and use of Nanofluids for Refrigeration Applications’. His research interests include experimental micro/nano-fluidics, electrokinetics, Lab on a Chip devices, diffusion coefficient measurements via microfluidics, and heat transfer enhancement via nanorefrigerants.