AC field driven interactions in concentrated electrolytes

Abstract Using a surface force balance, we measure the force between two crossed-cylinder electrodes for different electrolyte systems and different geometrical configurations under the influence of an AC field. When an AC field is applied to concentrated mixtures of an ionic liquid (IL) in a polar solvent, a force arises that is at least an order of magnitude larger and slower to reach steady state than the static response of the electrolyte. We demonstrate that this AC field effect persists in concentrated electrolytes beyond what has already been observed in pure ILs or aqueous electrolytes. Furthermore, we show that the magnitude of the electric field force response is dependent on the electrode radius of curvature. In experiments with pure ILs, a stronger force magnitude is observed for a smaller radius of curvature, implying that these interactions can be fine-tuned through geometrical design. These observations should guide the application of AC electric fields for the control of colloids and the design of passive control mechanisms in microfluidics and nanotribology.