Wang and collaborators wrote an article on the design of cuddle fish like biomimetic fin using shape memory alloy wires. A link to the abstract for this article is given here: http://www.sciencedirect.com/science/article/pii/S0924424708001283. The design of a biomimetic fishtail has utilization in the underwater vehicles, since fishtails create a greater propulsive efficiency. Also, there may be uses in the areas of microsurgery or underwater exploration that requires a narrow vehicle. The inspiration comes from the cuddlefish fin which works through a combination of jet propulsion at high speed and fin undulatory/oscillation at low speed. The fin of the cuddlefish consists of a 3 layered-structure.
The structure on the left is of the cuddlefish fin and on the right is of the biomimetic fin. The biomimetic fin is made of an elastic substrate (plastic and/or rubber silicone) with skin containing embedded shape memory alloy wires attached to it. The SMA wires acts as transverse muscle fibers by providing a lateral compressive force. While, the elastic substrate stores elastic energy.
The biomimetic fin is incorporated into the micro-robot fish as seen in the picture above in the assembled and unassembled forms. The motion of the fish is controlled by batteries and a control circuit. The resulting fish structure can swim forward and turn.