Bulk permeability measurements provide an incomplete descriptor of permeability when considering heterogeneous or anisotropic membranes. By positioning a scanning force microscope (SFM) onto a specially mounted membrane, local variations in friction force can be measured directly at the surface, with nanoscale resolution. Analogous to a puck on an air hockey table, permeate flow in membranes contributes to a local reduction in surface friction. Plotting the friction force determined by SFM versus pressure gives a gradient that is nominally proportional to permeance. Here, this new technique coined Flux Lateral Force Microscopy (Flux-LFM) is applied to Zeolites, Nafion, and reverse selective super glassy polymer membranes. In polymer membranes the signal is shown to contain information on permeability, as well as local rheological changes resulting from sorption and phase transitions.