GAS DRIVEN CONTROLLED RELEASE DEVICE

摘要

A controlled release device adapted to contain a material and to release it over an extended period of time, includes a hollow body (11) adapted to contain the material, and egress means (14) in the body adapted to allow egress of the material. Means for urging the material towards the egress means for egress therefrom includes an expandable chamber (22) in the body separated from the environment external to the body by gas permeable partition means (16, 116, 119'). The gas permeable partition means is arranged to be differentially permeable for selected gases in the chamber and the external environment, whereby the gas pressure in the chamber increases above and is maintained above a level sufficient to produce a driving force for sustaining egress of the material over the extended period of time.