Paper SS-TuP4
Evaluation of Dynamic Wettability on 2D Inverse Opal Structure

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

Static wettability of smooth solid surface is determined by balance of surface energy of each solid-liquid, liquid-gas, and solid-gas interface, and surface roughness. However, dynamic wettability is thought to be involved by various factors, e. g., the non-uniformity of composition and surface structure. We fabricated inorganic oxide surface with 2D inverse opal structure and homogeneity of the composition and surface structure, and evaluated their static and dynamic wettabilities.

At first, uniformed 2D colloidal particle film was fabricated on a glass substrate in the similar manner to LB method. SiO₂ thin films with 2D inverse opal structure were fabricated by using a precursor solution (tetraethoxysilane in ethanol and 2-ethoxyethanol) by spin coating and heating at 500°C. The prepared samples were stored in a constant temperature and humidity chamber. These samples were characterized by scanning electron microscope (SEM), optical microscope, and contact angle meter.

SEM images of fabricated samples are shown in figure 1. Film thickness and structure were different depending on the concentration of the precursor solution. Wettability seemed to depend on the film structure, especially in terms of dynamic wetting process; on several samples, thin water film was obviously observed at the outside of a droplet edge. Furthermore, pinning of a water droplet by large defects was also observed.

We fabricated SiO₂ thin films with various 2D inverse opal structures, and their static and dynamic wettabilities were evaluated. In this presentation, details of them and wetting processes will be discussed.