Determination of potential landscapes using video microscopy

Video microscopy can be used for the detection of surface potentials, when colloidal particles are present and act as tracer particles for then surface corrugation. Here we present measurements on colloidal particles, which are confined in narrow channels on a substrate and interact with a barrier, which impedes the motion along the channel. The motion of the particles then contains information on the gravitational potential as well as on the potential defined by the presence of the barrier. Statistical analysis is performed in order to extract the potential shapes which arise from the two interactions. We use brownian dynamics simulations in order to complement the experiments with tests of a large range of scenarios, which cannot be accessed in experiments.