THE USE OF FRACTAL GEOMETRY IN PHARMACEUTICAL SYSTEMS

The nature of surface irregularity affects many phenomena including adsorption/desorption, catalysis, crystal growth, drug dissolution and chromatography. Many excellent models have been developed with the oversimplified assumption that all particles are smooth spheres; fractal geometry allows these models to be expanded to irregular surfaces by providing a quantitative means of assessing surface roughness. An overview of fractal analysis is presented in the following and the state of the art, as far as pharmaceutical systems are concerned are outlined. Erroneous approaches, as well as the directions pharmaceutical research and technology might take in the area of fractal analysis are suggested. From a historical perspective, micromeritics (the science of particle size, shape and surface area) were first developed with the assumptions that all particles were smooth spheres. Much excellent work has been developed with such an oversimplified model. For example, numerous workers have shown that particle flow through an orifice is a function of ''particle [GRAPHICS] diameter'', and experiments have most often been carried out on particles as close to spherical as possible, and as monodisperse as possible. The science of micromeritics, the science of small particles, is the making of DallaValle (1943) who coined the term in a book of the same name which describes methods of particle size measurement, mostly used by soil scientists.1