|M.Sc Student||Lellouche Alexandre|
|Subject||Non-Linear Electrokinetic Phenomena in Asymmetric|
|Department||Department of Nanoscience and Nanotechnology||Supervisor||Professor Gilad Yossifon|
|Full Thesis text|
Concentration polarization or ion filtering effects are observed in channels where one dimension is less than several hundred nanometers. Furthermore, funnel-shaped nanochannel arrays have been demonstrated to exhibit ion current rectification inversion above a threshold voltage, corresponding to the Ohmic to over-limiting current transition. Previous experimental studies have examined rectification at either low voltages (Ohmic region) for conical nanopores or funnel-shaped nanochannels, or at high voltages (over-limiting region) for straight nanochannels with asymmetric entrances/microchannel chambers.
This thesis provides, for the first time, an experimental evidence, supported also by numerical simulations, of how rectification at the two extreme voltages occurs in the opposite direction for a funnel channel. This study also shows that the critical voltage for rectification inversion increases with ionic strength and that this inversion occurs as a result of the intra-channel ion depletion/enrichment phenomenon, which is responsible for Ohmic rectification and which is reversed via interaction with the opposite external concentration polarization, that develops beyond the threshold voltage.