Robotic models of swimming bacteria

The swimming of microorganisms is typically studied using biological experiments and/or numerical simulations. However, numerical simulations of microorganisms are often not compared to precise measurements because of the difficulty of making microscopic measurements of forces and torques in biological experiments, which are typically ∼ 10 μm. Instead, our research group uses robotic models that are about 10 cm in size and match the Reynolds number of swimming microorganisms by using highly viscous silicone oil that is 100,000X more viscous than water. We can then measure the forces and torques more easily and scale the results from our dynamically similar experiments to biologically relevant sizes. We have used our experiments to calibrate the method images for regularized Stokeslets and found excellent agreement between our data for both cylinders and helices. Our results also have confirmed the theory of Jeffrey and Onishi (1981) for the torque on a cylinder near a plane wall, as reported in Shindell et al., Fluids (2021).