Piezoelectric pump with annular valve arrangement

A piezoelectric pump, comprising:

• a first top board having a first aperture and a second aperture;
• a second top board spaced apart from the first top board and having a third aperture and a fourth aperture;
• a diaphragm disposed between the first top board and the second top board, and having a piezoelectric element attached thereto;
• a first side wall coupling the first top board and the diaphragm to define a first pump chamber between the first top board and the diaphragm;
• a second side wall coupling the second top board and the diaphragm to define a second pump chamber between the second top board and the diaphragm;
• a first valve having an annular shape to surround the first aperture while being spaced apart from the first aperture and the second aperture, and disposed in the first pump chamber between the first aperture and the second aperture when viewed in a plan view from a main surface of the first top board toward a main surface of the second top board;
• and
• a second valve having an annular shape to surround the third aperture while being spaced apart from the third aperture and the fourth aperture, and disposed in the second pump chamber between the third aperture and the fourth aperture when viewed in a plan view from the main surface of the second top board toward the main surface of the first top board.