Surface Tension Gradients as a Mechanism for Self-Propulsion

Abstract

This TFG explores the physical mechanisms that enable certain insects to walk and move across the water surface. It focuses on Microvelia, an aquatic insect known for its propulsion method. Microvelia, secretes surfactants from its rear that generate a localized gradient in the water’s surface tension pulling the insect forward and allowing it to move rapidly without active movements. This study analyses the fundamental thermodynamic and mechanical principles governing surface tension and the the role of surfactants in modifying it. Via dimensional analysis and the deduction of the equations of motion, this study demonstrates that the Marangoni force is the dominant propulsive mechanism for the Microvelia enabling the insect to reach peak speeds within milliseconds, highlighting the remarkable efficiency of the Marangoni Propulsion.