DIELECTRIC MEASUREMENT OF A SINGLE SUBMILLIMETER SIZE MICROCAPSULE

A new technique is described for measuring dielectric dispersion of a single microcapsule in suspension over a frequency range from 1 kHz to 10 MHz. It was applied to polystyrene microcapsules which showed a tw o-step dielectric dispersion, that is, a superposition of two Debye ty pe dispersions. The dielectric dispersion was analyzed by an electrica l model in which a spherical core covered with a shell is immersed in a continuous phase, yielding the phase parameters related to the micro capsule: the wall thickness, the permittivity and conductivity of the core phase. The advantage of this technique is that it can characteriz e individual microcapsules, whereas the conventional method provides a verage properties of many microcapsules. Hence, the technique enables us to directly determine the distributions of the phase parameters and to exactly examine the relationship between the dielectric behavior a nd the microcapsule structure simultaneously observed by microscopy.