The effect of drop size on contact angle measurements of superhydrophobic surfaces

In this study, the effect of drop volume on contact angle (CA) values and also on the applicability of the Cassie-Baxter equation is experimentally investigated. To do this, dimethyldichlorosilane (DMDCS) coated different sized square pillar surfaces with varying f(s)(CB)(geo) values were used. Varying water drop volumes between 0.5 mu l and 19 mu l were used to measure CA's on square pillar surfaces with different pattern sizes changing from 8 mu m to 40 mu m. It was found that experimental CA values remained constant for each drop volume, indicating that increase or decrease in drop volume had no significant effect on experimentally measured CA values of square pillar surfaces with varying pattern sizes and f(s)(CB)(geo) values. When the relationship between the applicability of the Cassie-Baxter equation and the drop volume was investigated, it was also found that variation in volume of the drop did not cause a significant change in deviations between the theory and the experiments. Delta theta(CB) values remained almost constant for all samples at varying drop volumes.