Asymmetric Rectified Electric Fields (AREFs) Generate Flows that can Overwhelm Induced-Charge Electrokinetics*

Recent computational and experimental work has established that application of an oscillatory electric potential to a liquid generates a long-range steady field, provided the ions present have unequal mobilities.   These steady fields, referred to as asymmetric rectified electric fields (AREFs), will significantly alter the behavior of electrically induced fluid flows at the microscale.  Here we consider the flows generated around a conducting cylinder, specifically comparing the quadrapolar flow due to classical induced charge electrokinetics (ICEK) and electroosmotic flow generated by AREFs.   We demonstrate that the applied potential, frequency, ionic mobility mismatch, ionic strength, and even the precise placement of the cylinder between two electrodes all dramatically alter the relative magnitudes of the ICEK and AREF flows.  The results shed light on some long-standing discrepancies between classic ICEK theory and experimental observations.