Abstract: A noningestible separation barrier having one or more pores of micropores (of one or more diameters) therein, with the pores or micropores being initially plugged with one or more materials selected for its/their solubility and/or integrity characteristics relative to certain environmental conditions. Ordinarily, the pores or micropores of the noningestible separation barrier are initially filled with at least one material having greater erodibility, under a given environmental condition, than the material constituting the separation barrier itself. The combination of the release rate (if any) or other membrane characteristic of the separation barrier, combined with the release rate and/or erosion life of the plugged pores, enables complex separations including variable release of cells, colloids, solutes or solvents over time, such as when the plugged pores remain intact until erosion is triggered by an environmental change such as solvent addition or ionic conditions or pH or thermal change.