Configuration Evolution of a Particle Raft with a Preprepared Crack Driven by the Diffusion of a Surfactant.

In the present study, the morphology evolution of a particle raft with a preprepared crack, which is caused by injecting the surfactant sodium dodecyl sulfate (SDS) into water, is demonstrated. Experimental results on the process of crack closure and configuration evolution are captured and are in excellent agreement with the numerical simulations. Then a surface diffusion model on SDS is proposed to quantify the detailed physical scenario. The surface diffusion factor is determined through the shooting method based on the experimental result of dynamic surface tension. As a result, the analytical solution for the SDS concentration distribution is given. The theoretical result on the dependence relationship between the profile shrinkage ratio and the time variable is consistent with the experimental result. At last, the relation between the initial surface tension difference of SDS and the profile shrinkage ratio is obtained in the light of experiments and dimensional analysis, and the two results are very close. These analyses provide a comprehensive understanding of the coupling between chemicals and mechanical behaviors of soft matter, and the modulation of defects in the particle raft provides some inspiration for engineering new devices at the microscale.