Investigating the Influence of Helix Micro Swimmer’s Rotation Rate and Fluid Viscosity on Swimming Speed

Multiple factors affect microswimmers’ performance in the fluid. The Reynolds Number shows the relationship among fluid density, fluid viscosity, the swimmer’s shape, and the swimmer’s velocity (Purcell, 1976). For microswimmers, the Re number was minimal for their size, making it more difficult to change their swimming velocity or direction (Purcell, 1976). A scaled model with the helical tail was assembled and tested to understand better the relationship between the swimmer’s velocity, self-frequency, and fluid properties. Unlike microswimmers with one degree of freedom, such as scallops, a helical-shaped microswimmer has enough degrees of freedom to control and swim in the fluid. The testing model maintains a 45° pitch angle for best efficiency and keeps other physical dimensions unchanged (Magariyama and Kudo, 2002). Switching the motor speed modes in the scaled model provides different tail rotation rates, and using laundry soap changes the density and viscosity of the testing fluid from regular water. With the most efficient pitch angle, the rotation rate leaves more impression on swimmer velocity than the viscosity in water versus soapy water. All collected data on distance with time were used for comparison and analysis.