Harnessing Flagella Dynamics for Enhanced Robot Locomotion at Low Reynolds Number

Abstract

Navigating environments with low Reynolds numbers <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(Re)</i> , where viscous forces dominate, presents unique challenges, such as the need for non-reciprocal motion dynamics. Microorganisms like algae and bacteria, with their specialized structures such as asymmetrical and flexible cilia and flagella, inspire efficient propulsion in such media. However, the mechanism for enhancing the propulsion speed of these microorganisms remains not fully understood. This study introduces a quadriflagellated, algae-inspired, cable-driven robot that mirrors these biological locomotion mechanisms. A single DC motor actuates four multi-segmented flagella, modulating their stiffness throughout the propulsion cycle. We focus on enhancing propulsion speed, hypothesizing that strategic flexibility alterations in flagella increased during the backward stroke and decreased during the forward stroke–significantly improve propulsion speed. Our experimental results confirm this, showing a marked improvement in propulsion speed, achieving a rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.7\pm 0.11$</tex-math></inline-formula> cm/cycle. Additionally, we explore the impact of flagella length and number on propulsion, providing valuable insights for biomedical and microfluidic research applications.