MEMBRANE-MODERATED CONTROLLED RELEASE

The dynamic characteristics of the membrane-moderated controlled release with an excess active agent dispersed in the core zone are presented for both isothermal and nonisothermal systems. Effects of the void fraction, membrane thickness, concentration dependence of diffusivity, and step change in the temperature of the environment on the rate of release are comprehensively studied. The applicability of the quasisteady state assumption to estimation of the steady state release rate is examined by comparing the rates of release for both the exact and approximate solutions. Optimization of the controlled release in terms of the membrane thickness and void fraction is also discussed based on a simple but pertinent objective function.