Surface roughness of the colloidal particles affects various microscopic and macroscopic properties of the colloidal suspensions. Especially in concentrated systems, the microscopic behavior of particle-particle frictional contacts has been recently proposed as being responsible for the macroscopic behavior of discontinuous shear thickening and jamming . Within the perspective of microscopic behavior, in concentrated systems, particles experience a crowded environment where the dynamical arrest due to the caging with the neighboring particles emerges. The effect of introduced surface roughness in this regime is believed to be dominant and play a key role in the mobility of the particles. A systematic research focusing on the concentrated systems’ colloidal dynamics is believed to shed light on the underlying reasons for rough particles jamming behavior via providing information about particles’ mobility in microscopic point of view.
Your research objective will be to explore the effect of surface roughness in colloidal dynamics by means of characterizing translational diffusion via measuring the mean square displacements of particles in dense systems. Initial experiments will be focused on hard sphere colloidal systems with smooth surface . You will perform particle tracking experiments with a systematic variation of volume concentrations. After that, focus will be given to the dispersions of rough particles. Again, a systematic variation of volume concentrations will be investigated to probe the effect of roughness in translational diffusion especially in dense systems and a comparison will be made with smooth particles’ results. Experiments will be done via confocal scanning laser microscopy (CSLM) and standard particle tracking routines in Matlab. In parallel with particle tracking experiments, you will conduct maximum packing concentration determination experiments to observe the effect of surface roughness in maximum packing fraction, which will provide useful complementary information about onset of jamming in terms of volume concentrations.
§ Daily supervision: MSc Beybin Ilhan, (firstname.lastname@example.org )
§ Supervision: Dr. Michel Duits, (email@example.com )
1. Hsu, Chiao-Peng, et al. "Roughness-dependent tribology effects on discontinuous shear thickening." Proceedings of the National Academy of Sciences 115.20 (2018): 5117-5122.
2. Ottewill, R. H., & Williams, N. S. J. (1987). Study of particle motion in concentrated dispersions by tracer diffusion. Nature, 325(6101), 232-234.