Design of multi-layer coated particles with sigmoidal release pattern

In order to design and control the release pattern of an active solid component, we investigated the release characteristics of core particles coated with multiple layers of fine permeable particles surrounding soluble particles dispersed in layers of impermeable wax. We examined the effect of operational conditions on the parameters of the release profile by multivariate analysis, and obtained simplified correlations for the maximum release rate and the lag time of the release curve as a function of the volume fraction of permeable particles and the thickness of the permeable- and soluble-particle layers. The results confirmed that the desired release rate could be obtained in the first place by adjusting the volume fraction and the thickness of the permeable-particle layer, while it was also possible to attain the required lag time by changing the thickness of the soluble layer. Finally, the calculation examples successfully illustrated the possibility of our being able to design the controlled-release particles with a prescribed sigmoidal release.