Piezoelectrically actuated fluid pumps

A pump, comprising:

• a pump housing surrounding a pump housing interior;
• a first deformable member, said first deformable member being disposed within said pump housing interior;
• wherein said first deformable member comprises a first piezoelectric layer, said first piezoelectric layer having opposing first and second major faces;
• wherein said first deformable member further comprises a first pre-stress layer, said first pre-stress layer being bonded to said first major face of said first piezoelectric layer;
• wherein said first pre-stress layer normally applies a compressive force to said first piezoelectric layer;
• wherein said first deformable member partially encloses a variable volume pump chamber;
• and wherein said pump housing partially encloses said variable volume pump chamber;
• a second deformable member, said second deformable member being disposed within said pump housing interior;
• wherein said second deformable member comprises a second piezoelectric layer, said second piezoelectric layer having opposing first and second major faces;
• wherein said second deformable member further comprises a second pre-stress layer, said second pre-stress layer being bonded to said first major face of said second piezoelectric layer;
• wherein said second pre-stress layer normally applies a compressive force to said second piezoelectric layer;
• and wherein said second deformable member partially encloses said variable volume pump chamber;
• a first port in said pump housing communicating said variable volume pump chamber with the exterior of said pump housing;
• a second port in said pump housing communicating said variable volume pump chamber with the exterior of said pump housing;
• valving means in communication with said first port for temporarily opening and closing said first port;
• and energizing means in communication with said first piezoelectric layer and said second piezoelectric layer for electrically energizing said first piezoelectric layer and said second piezoelectric layer;
• wherein said energizing means comprises means for applying a first alternating voltage difference at a first frequency between said first major face of said first piezoelectric layer and said second major face of said first piezoelectric layer;
• and wherein said energizing means further comprises means for applying a second alternating voltage difference at a second frequency between said first major face of said second piezoelectric layer and said second major face of said second piezoelectric layer.