In the experiments where particle cracked after poking, a quarter sphere model with a sharp edge was used as the initial geometry. The viscosity in the simulations was adjusted until the sharp edge moved by 0.5 µm for the observation time of the experiment. A distance of 0.5 µm corresponded to the resolution of the microscope. Since 0.5 µm is an upper limit to the movement in our experiments, the corresponding viscosity extracted from these simulations is considered a lower limit to the true SOA viscosity.