Micro- and nanoscale characterization of hydrophobic and hydrophilic leaf surfaces

Bhushan B., Jung Y.C

Nanotechnology 17 (2006) 2758–2772

Purpose

 

Characterization of micro- and nanoscale topographic features of hydrophobic leaves, and analyze their roll in the superhydrophobic behavior. The study also makes a comparison of hydrophilic leaves with the purpose to understand the importance of low energy surface materials in the improvement of hydrophobic behavior.

Methods

 

Four type of leaves were studied: lotus and colocasia with hydrophobic characteristics and, fagus and magnolia with hydrophilic characteristics. Topographical characterization of the leaves was performed using SEM. Height of the micro and nano features was measured using optical profilometry and AFM in both modes, contact and tapping. Finally wetting properties were determined using a contact angle goniometer.

Key Findings

·         Comparison between hydrophobic and hydrophilic leaves revealed that the later have a thin wax film, which suggests that low energy constituents over this surfaces influence the hydrophobic behavior.

·         Combination of low surface energy materials and roughness are the responsible factors for superhydrophobic behavior.

·         Superhydrophobic behavior combines micro- and nanoscale roughness. However nanoscale roughness is the main responsible for the increase in the contact angle due to the increase of air pockets under the drops.