Spring with a plurality of elements, and actuator including such a spring

A spring comprising a plurality of elements, each element comprising a rigid portion and a flexible beam, the extremities of the flexible beam being supported by the rigid portion, the flexible beam having a single stable position, so that the flexible beam can be deformed when a pressure is exerted between said extremities in the direction of the rigid portion, and returns to said single stable position when the pressure is released, and wherein the rigid portion of at least one element is in contact with the flexible beam of the next element between said extremities of the flexible beam, so that the spring has a negative stiffness over an operating range.The arrangement ensures a pure radial compression/expansion of the spring.