Potential induced adsorption/desorption of chloride ions on different functionalized gold surfaces. Schematics describe the relationship between surface stress change and available surface area. A, a bare and clean gold surface is shown. Chloride ions can freely interact with the whole surface and large surface stress changes are measured. Upon binding of some single-stranded oligonucleotide to the surface B, fewer ions can react with the surface leading to a smaller surface stress change. Once the layer is densely packed on the surface C, the surface stress change vanishes as no ions can reach the surface anymore.