Effect of surface geometry and morphic features on the flow characteristics of microsphere suspensions.

In this paper we present a study on the effect of surface ruggedness of microspheres on the rheological behavior of their suspensions. For this purpose, different types of ragweed pollen grains were selected as models of natural microspheres. A computer-image processing system based on Fourier and fractal analysis of the contour was used to quantitate the micromorphology and surface roughness. The viscosity of suspensions, prepared by the dispersion of the different types of microspheres in heavy liquid paraffin, was determined. It was found that an increase in surface roughness causes an increase in the viscosity of the suspension. Additional resistance to flow could be attributed to internal friction within the suspension due to an increase in the area of contact (during collision or aggregation) among the microspheres, and between microspheres and liquid environment. These findings suggest that the surface geometry of solid particles (e.g., microcapsules, beads, and microspheres) could have a significant effect on the performance of these microparticles in suspension.