Abstract: An osmotic pump comprises a first chamber (8) comprising an osmotically active substance (18), a second chamber (15) arranged to be filled with a solvent (17), and a semi-permeable barrier (14) separating the first chamber (8) from the second chamber (15). The semi-permeable barrier (14) is impermeable to the osmotic active substance and permeable to the solvent (17). The osmotic pump further comprises a pressure device (60) in fluid communication with the second chamber (15), wherein the pressure device (60) is arranged for pressurizing the solvent in the second chamber.

Abstract: The invention refers to a method for control of a volume flow in an osmotic micropump and an osmotic micropump. According to the invention, the osmotically driven volume flow of the solvent through the sempipermeable diaphragm of an osmotic micropump is controlled by the transfer of a solute, which is not freely permeable through the diaphragm, from a source chamber to the pump's delivery chamber. According to the invention, the delivery chamber is formed as a dilution chamber, wherein the solution is flow out along a convective dilution path close to the semipermeable diaphragm. Due to the entrance of the solvent, a stationary osmotic gradient can be achieved along the convective flow path in the dilution chamber. The invention allows the maintenance and control of the flow rate. It is able to move a volume which is large in comparison to the combined volume of the source chamber and the dilution chamber.