Micro-scale propulsion using multiple flexible artificial flagella

We propose a method to increase propulsion of a micro-scale swimming robot powered by an artificial flagellum through the use of multiple helices while retaining the simple actuation method of a single rotation axis. Scaled up experiments with similar Reynolds number are carried out to compare the performance of five different propulsion designs with pairs of stiff or flexible flagella. The designs feature stiff helices, straight flexible rods, and flexible helices inspired by bacterial flagella. Results indicate that for a given rotation frequency, thrust is proportional to the number of helices, but that the torque required to drive a flagellum offset from the common rotation axis is increased. Furthermore, shape deformation of flexible helices due to bending forces can positively affect thrust under certain conditions. Therefore, given the ease of fabrication, the use of multiple offset flexible flagella is a potential method to achieve increased thrust force in artificial bacteria flagella.