The yellowfin tuna is a torpedo shaped fish capable of escaping most predators because of its speed that can reach up to 46 miles per hour, making it one of the fastest fish in the world.  In addition to this, it is known as a strong swimmer that is able to swim great distances, sometimes across an entire ocean.

These characteristics have inspired researchers in creating a robotic counterpart.  In a recent publication of Science Robotics, engineers explain how they studied the science behind how the yellowfin tuna swims so that they can apply this in propulsion systems.  Lead researcher and University of Virginia Department of Mechanical and Aerospace Engineering professor, Hilary Bart-Smith, stressed on their primary goal, which was not just to build an ordinary robot.  "Our goal wasn't just to build a robot. We really wanted to understand the science of biological swimming," she said. "Our aim was to build something that we could test hypotheses on in terms of what makes biological swimmers so fast and efficient."

The Tunabot is about 10 inches long, and looks like a fish.  Although it does not have fins, it has a tail, which is its key medium of movement.

To test their robot, the engineers from the University of Virginia worked with biologists from Harvard University.  They used a fishing line tether to keep the robot steady, while a green laser that cut across the midline of the plastic fish and measured the fluid motion for every sweep of the robot's tail.  With an increase in current, the Tunabot responded like an actual yellowfin tuna would.  Both its tail and its body moved in a rapid bending pattern.

While we can say that the Tunabot is inspired by biology, it was also inspired by the MantaDroid, another US Navy supported underwater robot.  And this time, the Tunabot is unique in an application where instead of using propellers for an underwater system, the tail fins could initiate an improved propulsion system at a speed, the same as that of a live yellowfin tuna.

Bart-Smith says that a further goal in their research would be to surpass nature-that is to build robots that are "more evolved" than the biological counterparts.  "We don't assume that biology has evolved to the best solution," she said. "These fishes have had a long time to evolve to a solution that enables them to survive, specifically, to eat, reproduce and not be eaten. Unconstrained by these requirements, we can focus solely on mechanisms and features that promote higher performance, higher speed, [and] higher efficiency. Our ultimate goal is to surpass biology. How can we build something that looks like biology but swims faster than anything you see out there in the ocean?"

Below is a video showing the speed of the Tunabot while being tested for efficiency.