Bio-inspired Swimming Robot: How fixed bacteria move fluid

In the lab, I built a robot to study how fixed-position bacteria move the fluid around them. We designed it together with a bead system to visualise the flow. The robot has three parts, a body and two arms, connected by servos so that the arms move radially.

I drove the servos with cosine signals, with one of them offset by a phase angle. At a phase of 0° both arms move in sync and the beads stay still; at 180° there is still no net movement.

At 90°, however, the beads move in one direction, and at −90° they move in the opposite direction. The phase difference between the strokes is what breaks the symmetry and creates flow.

Before building it, I also wrote a small Python simulation of a three-rod swimmer to see how different stroke settings move the body.