A linear motion device includes a rod extending along a longitudinal axis, and a plurality of actuator units. Each of the plurality of actuator units includes at least one Shape Memory Alloy (SMA) element that is attached to a coupling mechanism. The at least one SMA element of each if the plurality of actuator units moves the coupling mechanism along the longitudinal axis, and into grasping engagement with the rod. Each actuator unit moves the rod a unit movement distance along the longitudinal axis in response to a control signal. The plurality of actuator units are actuated repeatedly in a cyclic order to move the rod in a continuous linear motion a distance greater than the unit movement distance of each of the plurality of actuator units.