Existing materials with low surface energy can produce a non-wetting surface with a contact angle reaching up to 120°, but the lotus leaf portrays contact angles in excess of 165°. This super hydrophobicity (or non-wetting) is related to the ideal spread of micro-protrusions, which are covered with nanohairs and impart two levels of surface roughness.

Researchers based in India and the US are using computational fluid dynamics (SimDrop) to investigate the effect in more detail. Their work correlates the non-wetting phenomena of the lotus leaf with its mechanical properties (Young's modulus and critical flexing stress) and the areal spread of micro-protrusions on the leaf surface.

Quasistatic nanoindentation of nanohairs on the lotus-leaf surface has shown a variation of elastic modulus between 359 and 870 MPa, which in turn dictates the critical flexing strength and consequent non-wetting. A qualitative model is proposed for the way nature has chosen to render the lotus-leaf surface non-wetting.

The researchers presented their results in Nanotechnology.