Mechanism of Operation
ALZET pumps operate because of an osmotic pressure difference between a compartment within the pump, called the osmotic layer, and the tissue environment in which the pump is implanted. The high osmolality of the osmotic layer causes water to flux into the pump through a semipermeable membrane which forms the outer surface of the pump. As the water enters the osmotic layer, it compresses the flexible reservoir, displacing the test solution from the pump at a controlled, predetermined rate. Because the compressed reservoir cannot be refilled, the pumps are designed for single-use only.