Various application are provided for an enclosure having a first wall and
two or more second walls surrounding a cavity. The enclosure also has an inlet
and outlet each in fluid communication with the cavity. The second walls each have
at least a portion shaped such that a force acting on the first wall tending to
deflect the element causes an amplified deflection of the second walls into the
cavity. Such applications include a pump, a structure comprised of one or more
enclosures, structural elements, and apparatus for storing and releasing energy.