A miniature unidirectional valve configured to restrict the free flow of fluid through the valve includes a valve body having an inlet and an outlet. A flexible membrane is movably disposed over the inlet and outlet, and movable between an open position and a closed position. The flexible membrane is movable by a pressure from the inlet to move the membrane to the open position. A control chamber is disposed in the valve body adjacent the fluid flow path, and configured to apply a pressure against the membrane to move the membrane to the closed position to restrict fluid flow through the valve. A preload structure is associated with the flexible membrane, and biases the flexible membrane toward the closed position.
