A shape memory alloy actuator, comprising: a shape memory alloy torque tube having a first end, a second end, and an elongate surface extending between the first end and the second end; and a heat transfer structure, wherein the heat transfer structure: (i) is in mechanical and thermal contact with the elongate surface of the SMA torque tube; (ii) extends at least partially between the first end and the second end of the SMA torque tube; and (iii) has a natural characteristic dimension and a modified characteristic dimension, and an intermediate conformation in which an intermediate characteristic dimension of the heat transfer structure is between the modified characteristic dimension and the natural characteristic dimension, wherein the heat transfer structure exerts a retention force on the SMA torque tube in said intermediate conformation so that the heat transfer structure is retained in mechanical and thermal contact with the elongate surface of the SMA torque tube solely by said retention force, characterized in that the heat transfer structure includes an elongate conductive body, wherein the elongate conductive body has: a plurality of helical surface-contacting regions that are in mechanical and thermal contact with the elongate surface of the SMA torque tube, and a plurality of deviation regions that deviate from a helical shape and project away from the elongate surface of the SMA torque tube, wherein a corresponding deviation region of the plurality of deviation regions extends between each adjacent pair of surface-contacting regions of the plurality of surface-contacting regions. a shape memory alloy torque tube having a first end, a second end, and an elongate surface extending between the first end and the second end; and a heat transfer structure, wherein the heat transfer structure: (i) is in mechanical and thermal contact with the elongate surface of the SMA torque tube; (ii) extends at least partially between the first end and the second end of the SMA torque tube; and (iii) has a natural characteristic dimension and a modified characteristic dimension, and an intermediate conformation in which an intermediate characteristic dimension of the heat transfer structure is between the modified characteristic dimension and the natural characteristic dimension, wherein the heat transfer structure exerts a retention force on the SMA torque tube in said intermediate conformation so that the heat transfer structure is retained in mechanical and thermal contact with the elongate surface of the SMA torque tube solely by said retention force, (i) is in mechanical and thermal contact with the elongate surface of the SMA torque tube; (ii) extends at least partially between the first end and the second end of the SMA torque tube; and (iii) has a natural characteristic dimension and a modified characteristic dimension, and an intermediate conformation in which an intermediate characteristic dimension of the heat transfer structure is between the modified characteristic dimension and the natural characteristic dimension, wherein the heat transfer structure exerts a retention force on the SMA torque tube in said intermediate conformation so that the heat transfer structure is retained in mechanical and thermal contact with the elongate surface of the SMA torque tube solely by said retention force, characterized in that the heat transfer structure includes an elongate conductive body, wherein the elongate conductive body has: a plurality of helical surface-contacting regions that are in mechanical and thermal contact with the elongate surface of the SMA torque tube, and a plurality of deviation regions that deviate from a helical shape and project away from the elongate surface of the SMA torque tube, wherein a corresponding deviation region of the plurality of deviation regions extends between each adjacent pair of surface-contacting regions of the plurality of surface-contacting regions. a plurality of helical surface-contacting regions that are in mechanical and thermal contact with the elongate surface of the SMA torque tube, and a plurality of deviation regions that deviate from a helical shape and project away from the elongate surface of the SMA torque tube, wherein a corresponding deviation region of the plurality of deviation regions extends between each adjacent pair of surface-contacting regions of the plurality of surface-contacting regions.