An actuator that includes a shell, a ring structure within the shell, a shape-memory material wire fixed at opposite points of the ring structure to extend in a first direction across a width of the ring structure, and a cooling fluid provided within the shell and in fluid communication with the shape-memory material wire. When the shape-memory material wire is heated, the shape-memory material wire contracts in the first direction to reduce the width of the ring structure and increases a height of the ring structure extending in a second direction perpendicular to the first direction.