Electrical Double-Layer Forces Measured with an Atomic Force Microscope while Electrochemically Controlling Surface Potential of the Cantilever

The atomic force microscope was used to detect electrostatic forces and estimate surface potentials of samples in aqueous solution by applying voltage to a conducting tip. We controlled surface potential of a Au-coated cantilever electrochemically, and measured force vs distance curves on monolayers with different kinds of functional groups. As a result, we detected force variation with applied voltage to the tip, and the direction of force variation was found to agree with the polarity of surface charges due to the dissociation of the functional groups.