Direct observation of origin of contact angle using super-lattice nanostructures

Abstract

Specifically arranged roughness on natural surfaces can be exciting and unique physical effect such as anisotropic de-wetting, pressure resistance and so on. However, precise investigation of the roughness arrangement effect is hard to be achieved since the geometrical wetting variables are differed with roughness arrangement variation and it induces significant difference of static contact angle, hysteresis and wetting state. In this study, to confirm the roughness arrangement effect on static contact angle we arranged the hexagon periodicity using Moir$acute{e}$ effect and phase shift photolithography. With fixed conventional wetting variables, apparent contact angles increase as hexagon periodicity decreases. In addition, as a result of combination the hexagon ridge and geometrical free energy distribution during liquid evaporation process we observed selectively aligning the surfactant at the hexagon ridge regardless of hexagon periodicity. Our result is expected to elucidate the key morphological factor that govern the physics of static contact angle on the structured solid surfaces.