Eur. Phys. J. E (2016) 39: 24
https://doi.org/10.1140/epje/i2016-16024-7

Regular Article

Surface roughness induced cracks of the deposition film from drying colloidal suspension

¹ School of Physics, Northwest University, 710069, Xi’an, China
² Department of Physics, The Hong Kong University of Science and Technology, Hong Kong, China
³ Siyuan Laboratory, Department of Physics, Jinan University, Guangzhou, 510632, Guangdong, China
⁴ Beijing Aeronautical Science & Technology Research Institute of COMAC, 102211, Beijing>, China
⁵ National Key Laboratory and Incubation Base of Photoelectric Technology and Functional Materials, Northwest University, 710069, Xian, China

^* e-mail: jing@nwu.edu.cn

Received: 6 June 2015
Accepted: 25 September 2015
Published online: 26 February 2016

Abstract

We investigate crack formation in deposition films from drying colloidal suspension drops, by varying the roughness and texture of the substrate. The experimental results indicate that the crack number or crack spacing presents a general dependence on the substrate roughness, despite the orientation of the substrate textures. Interestingly, the crack spacing decreases with the increase of the roughness. Two possible mechanisms are proposed to understand the dependence of the cracks on roughness. Firstly, the concentration reduction of the drying suspension due to collecting colloidal particles from the substrate textures decreases the crack spacing. Secondly, stress concentration resulting from the defects (the notches in textures) in the dried deposition enhances crack formation. However, a quantitative estimation by the calculation of the stress concentrating factors reveals that the notch of the substrate textures dominates crack variation. The results here bring forth a practical method for controlling the crack orientation and suppression, and a potential application to crack-free coatings, films and paintings during the drying of complex fluids.