Eur. Phys. J. E (2014) 37: 84
https://doi.org/10.1140/epje/i2014-14084-3

Regular Article

Surface wrinkling and cracking dynamics in the drying of colloidal droplets

¹ State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, 710072, Xi’an, China
² Functional Soft Matter & Materials Group (FS2M), Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, School of Science, Northwestern Polytechnical University, 710129, Xi’an, China

^* e-mail: liuzht@nwpu.edu.cn
^** e-mail: dyzang@nwpu.edu.cn

Received: 26 April 2014
Revised: 17 July 2014
Accepted: 2 September 2014
Published online: 26 September 2014

Abstract

The cracking behavior accompanied with the drying of colloidal droplets containing polytetrafluoroethylene (PTFE) nanoparticles was studied. During evaporation, due to the stretching effect of the liquid zone, the receding wet front leads to the formation of radialized surface wrinkling in the gel zone. This indicates the building of a macroscopic stress field with a similar distribution. As a result, the cracks in the deposited films are in a radial arrangement. The propagation velocity of the cracks depends on the thickness of the film, ∼ H ^3/5 . In addition, sodium dodecylsulfate (SDS) additives can be used to tune crack behavior by causing a reduction of the capillary force between particles. The results highlight the significance of the receding wet front in building the drying deposition stress field and may be helpful in other fields related to drying and cracking processes.