AFM cantilever with in situ renewable mercury microelectrode

We report here first results obtained on a novel, in situ renewable mercury microelectrode integrated into an atomic force microscopy (AFM) cantilever. Our approach is based on a fountain pen probe with appropriate dimensions enabling reversible filling with (nonwetting) mercury under changing the applied pressure at a connected mercury supply in a dedicated experimental setup. The fountain pen probe utilizes a special design with vertical pillars inside the channel to minimize mechanical perturbation. In proof of principle experiments, dropping and hanging mercury drop were observed as a function of the applied pressure at the external mercury supply. Electrical conductivity occurred only through the mercury after filling, and the empty fountain pen probe showed excellent electrical insulation. This was demonstrated by chronoamperometric measurements in the electrolyte and by mechanical and electrical contacting of an ITO substrate with a mercury-filled and empty probe in air. Finally, cyclic voltammetry and square wave voltammetry were done in a static mercury electrode fountain pen configuration, demonstrating the principle usability of the mercury probe for electrochemical studies. Our findings are of fundamental importance as they enable further integration of a renewable mercury electrode probe into an AFM setup, which is the subject of ongoing work.