Osmotic dispense pump for operation at different temperatures and pressures

Three different osmotic pumping devices are designed, developed and tested. These devices are intended for an application, wherein a constant flow rate of 1 μL/h is required for a period of 1 year with capability to operate at different pressures and different temperatures. The devices are completely self-sustaining and self-contained, with a pressurized solvent supply to avoid phase changes that inhibit functionality of the devises, and to allow operation in any orientation. The designs of the osmotic devices utilize unique methods for: (i) membrane retention and (ii) onboard water reservoir containment. During development, two different semi-permeable materials are considered, polyimide and porous glass. The devices using polyimide as the semi-permeable membrane are capable of operation at temperatures up to and including 75 °C, and at pressures up to 1.03 MPa. The devices using porous glass operate at temperatures in excess of 121 °C, unless pressures above 172.4 kPa are applied, in which case, operation is limited to temperatures less than 50 °C.