Devices are provided for controlled release of chemical molecules, such as drugs or diagnostic agents. The devices comprises a substrate; a plurality of discrete reservoirs located in the substrate, wherein the reservoirs each have at least one opening at a surface of the substrate; chemical molecules, for release, disposed in the reservoirs; a rupturable barrier layer closing the at least one opening; and a pressure generating material disposed in the reservoirs, the pressure generating material being selected from the group consisting of water-swellable materials, osmotic pressure generating materials, and combinations thereof, wherein the chemical molecules can be selectively released from each reservoir by rupturing of the barrier layer, due to pressure generated by the pressure generating material.