Related Experiment Video
Updated: Jul 7, 2026

Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
Buoyant force and sinking conditions of a hydrophobic thin rod floating on water
Jian-Lin Liu1, Xi-Qiao Feng, Gang-Feng Wang
1FML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Abstract:
Owing to the superhydrophobicity of their legs, such creatures as water striders and fisher spiders can stand effortlessly, walk and jump quickly on water. Directed toward understanding their superior repellency ability, we consider hydrophobic thin rods of several representative cross sections pressing a water surface. First, the shape function of the meniscus surrounding a circular rod is solved analytically, and thereby the maximal buoyant force is derived as a function of the Young's contact angle and the rod radius. Then we discuss the critical conditions for a rod to sink into water, including the maximal volume condition and the meniscus-contact condition. Furthermore, we study the sinking conditions and the maximal buoyant forces of hydrophobic long rods with elliptical, triangular, or hexagonal cross-section shapes. The theoretical solutions are quantitatively consistent with existing experimental and numerical results. Finally, the optimized structures of water strider legs are analyzed to elucidate why they can achieve a very big buoyant force on water.
Related Concept Videos
Buoyancy
To get...
Density and Archimedes' Principle
Buoyancy and Stability for Submerged and Floating Bodies
Archimedes' Principle
Hydrostatic Pressure Force on a Curved Surface
Hydrostatic Pressure Force on a Plane Surface

