Building a macroscopic, low Reynolds number three-link swimmer

One of the simplest robots that can swim at low Reynolds number is Purcell’s three-link swimmer, which consists of three hinged links in a chain. The work of Hatton and Choset (IEEE Trans. Robot, 2013) provides a theoretical framework to predict the displacement and rotation of such a swimmer, but assumes the robot links are slender. They use a phase space of the two joint angles and a 3-D map known as a height function derived from the Navier-Stokes equations to determine the motion of the swimmer. However, to our knowledge, no one has tested this theory experimentally, which is the goal of our study. We are building a macroscopic three link robotic swimmer that will swim in highly viscous silicone oil so the Reynolds number is small. We will compare the motion of our robot to that predicted using the theoretical height function. We will also determine the height function for our robot empirically (Hatton et al., PRL 2013) to understand the error introduced by our robot not being a truly slender body. We will also be able to systematically change the aspect ratio and length of the swimmer using 3-D printed body parts to understand the how the performance of the swimmer is affected by body shape.