This one looks really cool:
From the mission statement of the project that developed this fish (please excuse the poor English, I think it was written a native Chinese speaker):
In nature, fish has astonishing swimming ability after thousands years evolution. It is well known that the tuna swims with high speed and high efficiency, the pike accelerates in a flash and the eel could swim skilfully into a narrow hole. Such astonishing swimming ability inspires us to improve the performance of aquatic man-made robotic systems, namely Robotic Fish. Instead of the conventional rotary propeller used in ship or underwater vehicles, the undulation movement provides the main energy of a robotic fish. The observation on a real fish shows that this kind of propulsion is more noiseless, effective, and maneuverability than the propeller-based propulsion. The aim of our project is to design and build autonomous robotic fishes that are able to reactive to the environment and navigate toward the charging station. In other words, they should have the features such as fish-swimming behaviour, autonomously navigating ability, cartoon-like appearance that is not-existed in the real world.
It’s rather like the swimming snake from Japan that I wrote about earlier (unfortunately the youtube video for that one appears to have been taken down).
Where early ideas of mimicking animal locomotion to travel through foreign environments, for example the flapping wing designs of so many comical failures of early attempts at flight, often proved that simple imitation was the wrong starting point, once the full set of the physical principals underlying a form of motion are understood, often returning to mimicry results in some surprising new capabilities. We had to bludgeon our way through the air in fixed wing aircraft for a couple of decades before we were able to figure out how to make things like ornithopters a practical application.
The fact that one of the advantages to the undulant propulsion this robotic fish uses is its silence is not necessarily as ominous as it sounds. Of course one of the first things that comes to mind is its potential use as a guidance and propulsion system for underwater bombs. But there are many other reasons to be quiet under the sea. Using them as marine biology research tools, I imagine you’d be able to swim them right into the midst of other life without disturbing natural behavior, as a noisy propeller based submersible might do. Autonomously guided versions might be able to inspect undersea infrastructure around mining rigs or undersea cables, or even perform environmental cleanup tasks like oceanic Roombas.
The tradition of mimicking animal biology with automatons goes back at least as far as Vaucanson’s Duck in 1739. But where the purported mimicry in that device was digestion and in the end it turned out to be a not very elaborate hoax, there have been many profound advances in robotics since that have sprung from a close observation of evolved natural solutions to environmental challenges. Locomotion is only one of those. Simple self-awareness is another. Repairing injuries and self-replication is yet another.
I’m trying to come up with a system for classifying the various strategies of biological mimicry in evidence in contemporary robotics research. I’m sure someone smarter than me has done this already, but until I find theirs, I’ll keep working on mine.