Design and Analysis of a Helically Propelled Microswimmer

Bacteria can navigate through microscopic environments, which are highly viscous. The secret of their movement lies in the flagella on the body. These flagella spin in a spiral way in the fluid to propel the body forward. This provides the scientists an efficient strategy for propulsion under low Reynolds number. Grasping the mechanism behind is crucial for designing artificial micro swimmers. This work brings together theoretical modelling and scaled prototyping to analyse the underlying principles. First, a resistive-force-theory (RFT) model that links helical geometry to thrust was first developed. The optimal flagellar pitch angle that maximizes the speed was also obtained. The question then shifted to scalability. In reality, we can only manufacture macroscopic models. Buckingham Pi Theorem, a method of nondimensionalization, guided the scaling laws to bridge the micro to macro level. A low-cost physical model was then constructed—a plastic hull powered by a twisted rubber band driving a wire helix. The model successfully achieved forward thrust through helical rotation. Collectively, this work provides an integrated framework—combining theory and experiment—for developing bio-inspired helical propulsion systems in viscous, inertia-dominated environments.