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

An actuator comprising an annular spring and an annular electroactive polymer layer laminated to said spring in a radial configuration, said spring comprising a plurality of elements, each element comprising a rigid portion and a flexible beam, the extremities of the flexible beam being supported directly by the rigid portion, and electrodes operating the electroactive polymer layer,

• 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, so that the spring and electroactive film combination has a negative stiffness over an operating range,
• 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.