Prof. Michael S Triantafyllou

What can deep-sea fish -- those highly maneuverable and seemingly effortless swimmers -- teach us about the physics of underwater propulsion? That is the question that drives the research in Michael Triantafyllou’s laboratory. We use biomimetics to produce and study synthetic systems that emulate the functions of biological organisms. Our goal is to use swimming fish as a model system to study the sensing, mechanics, fluid mechanics and control of swimming. This work involves an intense study of material engineering to help us select appropriate materials for our models, coupled with an intense study of muscle structure, arrangement and control to allow us to engineer robotic systems that emulate swimming behavior. Research is providing us with a deeper understanding of the structure, mechanics and control of natural swimming, and with robots that better emulate this behavior.

The first model fish was six-foot-long Charlie, the Robotuna, but most of our current studies use a three-foot-long robot, Pike. The challenge is to design and produce robots that are strong enough to swim and turn, flexible enough to mimic a fish’s movements, light enough to float and waterproof enough to endure underwater testing. Our models are constructed from fiberglass, steel mesh, and foam and sheathed in latex Lycra.

One focus of current investigation is the development of skin-like materials that are strong enough and flexible enough to withstand experimental conditions in our study tanks. Robotic fish, like live fish, flex their body around as they swim. None of the waterproof synthetic materials that we have used so far to cover the robot fish can flex well without wrinkling or can resist damage caused by water pressure. We are collaborating with Bob Langer’s tissue engineering laboratory to develop a skin-like material derived from fish cells that we can wrap around our robot fish. Eventually, we hope to develop synthetic materials that will be robust enough to use on flexible underwater robots.

Another focus of study is on the control and fabrication of synthetic muscles that emulate the behavior of animal muscles. Muscles produce large forces, but motors need complex gears to produce comparable forces; hence, the use of muscles in robots would greatly enhance their performance efficiency. We are working with shape memory alloys and are collaborating with Ian Hunter’s bioinstrumentation laboratory to investigate the use of conducting polymers to construct artificial muscles.

Studies of robotic fish have obvious applications in developing effective sensing control and actuation devices for robots, and for underwater propulsion systems. However, we are primarily interested in discovering basic principles of function and control of swimming behavior and understanding the control of flow around bodies in water.