Computing the local ion concentration variations for electric-double-layer-modulation microscopy

Modulating the electric potential on a conducting electrode is presented to generate an optical contrast for scattering microscopy that sensitive both surface charge and local topography. We dub this method Electric-Double-Layer-Modulation microscopy. numerically compute change in ion concentration origin of three experimentally relevant geometries: nanosphere, nanowire, nanohole. In absence plasmonic effects physical absorption, observable proportional derivative with respect modulated potential. demonstrate depends size object and, less intuitively, also its charge. This dependence key measuring charge, absolute way, using method. Our results help identify experimental conditions such as dynamic range sensitivity will be necessary detecting elementary jumps. conclude nanohole most suitable geometry among these achieving sensitivity.