Method of manufacturing an implantable pressure-actuated drug delivery system

A method of fabricating an implantable, pressure-actuated drug delivery system, the method comprising:

• fabricating a frangible layer of one or more materials over a substrate surface;
• forming a cavity within the substrate, including an opening through the substrate surface to expose at least a portion of the frangible layer to the cavity;
• disposing a drug within the cavity;
• sealing the cavity;
• pressurizing the cavity;
• and
• fabricating a substantially non-frangible layer of an implant-environment-dissipative material over the frangible layer to prevent premature rupture of the frangible layer an at an ambient environment pressure and to dissipate within an implant environment,
• wherein the frangible layer is fabricated to have a rupture threshold within a range of approximately 200 millimeters of mercury (mmHg) to 1200 mmHg, and a rupture time of at least 15 seconds, and
• wherein the pressurized cavity is pressurized to a pressure that exceeds the rupture threshold by a rupture pressure within a range of approximately 20 mmHg to 50 mmHg relative to one atmosphere to cause the frangible layer to rupture when the implant environment pressure falls below and remains below the rupture pressure for at least 15 seconds.