Electrokinetics in Microfluidics: Active Control of Ion Transport and Active Particles for Unified Label-Free Cargo Transport
The ability to induce regions of high and low ionic concentrations adjacent to a permselective membrane or a nanochannel subject to an externally applied electric field (a phenomenon termed concentration polarization) has been used for a broad spectrum of applications ranging from on-chip desalination, bacteria filtration to biomolecule preconcentration. But these applications have been limited by the ability to control the length of the diffusion layer that is commonly indirectly prescribed by the fixed geometric and surface properties of a nanofluidic system. Here, we demonstrate that the depletion layer can be dynamically varied by inducing controlled electrothermal flow driven by the interaction of temperature gradients with the applied electric field. To this end, a series of microscale heaters, which can be individually activated on demand are embedded at the bottom of the microchannel and the relationship between their activation and ionic concentration is characterized.
Utilization of active particles to transport both biological and inorganic cargo has been widely examined in the context of applications ranging from targeted drug delivery to sample analysis. In general, carriers are customized to load one specific target via a mechanism distinct from that driving the transport. Here we unify these tasks and extend loading capabilities to include on-demand selection of multiple nano/micro-sized targets without the need for pre-labelling or surface functionalization. An externally applied electric field is singularly used to drive the active cargo carrier and transform it into a mobile floating electrode that can attract (trap) or repel specific targets from its surface by dielectrophoresis, enabling dynamic control of target selection, loading and rate of transport via the electric field parameters.
Gilad Yossifon is Associate Professor in the faculty of Mechanical Engineering at the Technion – Israel Institute of Technology and the head of the micro- and nano-fluidics laboratory since 2009. Gilad completed his PhD (2008) at Tel-Aviv University, his MSc (1999) and BSc (1994, Summa Cum Laude) studies in Mechanical Engineering at the Technion, and an additional MSc (2003) in Electrical Engineering in Tel-Aviv University. Between 2007-2009 he was a postdoc research associate in the University of Notre Dame in the Chemical and Biomolecular department. His research interests lie in the area of electrokinetics in micro- and nano-fluidics. He has published over 60 peer-reviewed publications.