Direct visualization of free-volume-mediated diffusion in colloidal glass

The relationship between particle diffusion and free volume of colloidal glass was studied in real space by laser scanning confocal microscopy. By quantifying the particle diffusion distance and the free volume size, we found a strong spatial correlation between these two quantities. Large free-volume regions were observed to possess low elastic modulus and thus results in a low energy cost of diffusion-induced strain, indicating that a large free-volume region presents a low energy barrier to structural rearrangement, thereby benefiting particle diffusion.