Droplet Contact Angle Measurement on Microstructures of Octocoral Sclerites-ESEM Image Analysis

Abstract

This work explores the methodology for micron-scale water droplet contact angle derivation for the warty surface of octocoral sclerites. The calcite-made sclerites of the Red Sea octocoral Dendronephthya hemprichi have been chosen as a model for this study. Water droplet condensation on the sclerites has been in-situ investigated using Quanta 200 FEG (field emission gun) ESEM (environmental scanning electron microscope) under wet environmental conditions. Two different analysis methods of droplet top and side views have been applied to determine the contact angle based on the secondary electron images. The ESEM image analysis for the sclerites indicates that their surface is hydrophilic. The microscopic contact angle is measured to be 45.3? ± 6.3?. The macroscopic contact angle has been calculated by using the Wenzel model for the surface texturing of the sclerites