The direct link between inter-particle force profiles and bulk rheology in dense suspensions: An experimental evidence using tuning-fork AFM.

Dense suspensions are soft-matter systems that might display not-fully-understood and complex flow behaviors (e.g. shear thickening, shear thinning). The microscopic interactions between the particles – especially pairwise frictional forces – can play a decisive role in explaining the bulk rheology of suspensions in dense regime.
By taking advantage of state-of-the-art techniques of tuning-fork AFM, we evidence the link between the microscopic friction coefficient of the particles and the jamming fraction of the bulk. We mesure the pairwise force profile of polystyrene particles (of diameter ranging from 40 μm to 500 μm), immersed in air and various Newtonian fluids (water, silicone oil, and PEG).
We find that their coefficient of friction varies with the matrix fluid. The correlation between particles’ friction and suspension's jamming fraction agrees with Chèvremont et al. [1]. Furthermore, our results show that friction coefficient decreases with an increasing normal load, following the model of Lobry et al. [2].
Ours works help to evidence the impact of particulate friction on the behavior of dense suspension.

[1] Chèvremont et al., PRF 4 (2019).
[2] Lobry et al., JFM 860 (2019).