THE SCANNING DIELECTRIC MICROSCOPE

This article describes a new instrument to image the local capacitance (or permittivity) and conductance (or conductivity) of colloidal particles and membranes in an aqueous environment. Capacitance and conductance are measured by the three-terminal (guarded electrode) method with a coaxial probe electrode, which is laterally scanned over samples on a plate electrode. The images of capacitance and conductance are obtained at frequencies between 1 kHz and 10 MHz, which enables the study of dielectric relaxation of individual particles and local areas of membranes.