TCP works by contracting like a muscle when heated, converting the energy into mechanical motion. The TCP used in this work is warmed by Joule heating — the passing of current through an electrical conductor, which produces thermal energy and heats up the conductor. Minimizing the distance between the TCP on one side of the robot fish and the spring on the other, activates the fin at the rear, enabling the robot fish to reach new speeds. The undulating flapping of its rear fin was measured at a frequency of 2Hz, two waves per second. The frequency of the electric current is the same as the frequency of tail flap.