A pump comprises a diaphragm assembly which includes a first diaphragm (22) having a first diaphragm edge (28) and a second diaphragm (24) having a second diaphragm edge (30). The first diaphragm edge (28) and the second diaphragm edge (30) are bonded together so that a bellows chamber (26) is formed between the first diaphragm (22) and the second diaphragm (24). At least one and possibly both of the first diaphragm (22) and the second diaphragm (24) is a piezoelectric diaphragm which displaces in accordance with application of an electrical signal. A driver applies the electrical signal to whichever of the first diaphragm (22) and the second diaphragm (24) is the piezoelectric diaphragm. The first diaphragm and the second diaphragm bow outwardly together and shrink in diameter during a suction stroke but flatten out and increase in diameter during a pump stroke.