Self-organized pattern formation of cracks perpendicular to the drying direction of a colloidal suspension

Abstract

A new cracking mode in silica colloidal films formed via quasi-one-dimensional directional drying is presented. Unlike typical cracking parallel to the drying direction, unique periodic cracks perpendicular to the drying direction are formed when a silica colloidal suspension dries in a thin glass cell. The mechanism of formation of the perpendicular cracks is discussed and a mathematical model based on the mass balance of water, which describes the experimental data well, is proposed. Our model reveals that the drying rate of water predominantly determines crack spacing and it is inversely related. Analogy of the inverse relation to the scaling law for the self-organized formation of columnar jointing, observed in desiccated corn starch and cooled lava, is also discussed.