Electrostatic Actuation of AFM Cantilevers in Aqueous Solutions

Performing electrical Atomic Force Microscopy measurements in aqueous solutions is of paramount importance in a vast range of scientific fields. As with operation at ambient conditions, it is important to ensure that the force on the cantilever is purely of electrostatic origin. However, with the insertion of water and therefore mobile ions and polar molecules into the tip-sample system come several unwanted effects. Here, an experimental study is carried out, analyzing the influence of parameters such as drive-frequency, -amplitude and ionic concentration on the feasibility to perform electrical AFM measurements in aqueous solutions. To this end the system is theoretically modelled and parameter sweeps are preformed, leading to transition frequencies above which the electrostatic force has the predominant impact on the cantilever.