Dugyala Venkateshwar Rao, Lama Hisay, Satapathy Dillip K, Basavaraj Madivala G
Polymer Engineering and colloid Science Lab, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
Soft Materials Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India.
Sci Rep. 2016 Aug 1;6:30708. doi: 10.1038/srep30708.
Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments.
通过改变干燥条件，可以控制蒸发诱导干燥形成的胶体薄膜中的裂纹。我们首次表明，除了微观结构和颗粒组装外，胶体薄膜中的裂纹形态还取决于构成颗粒的形状。为了研究颗粒形状对裂纹图案的影响，在静滴实验中使用了单分散球形和椭球形颗粒。观察干燥后的静滴时，我们发现球形颗粒分散体沿径向出现裂纹，而椭球形颗粒分散体则出现圆形裂纹图案。裂纹图案的变化是形状各向异性颗粒自组装及其有序排列的结果。颗粒的排列决定了裂纹方向，裂纹沿着阻力最小的路径延伸，以释放颗粒薄膜中储存的多余应力。使用了不同纵横比（约3至7）的椭球体，并且在所有实验中都反复观察到圆形裂纹图案。
