Soft granular particles sheared at a controlled volume: Rate-dependent dynamics and the solid-fluid transition

J. C. Tsai*, M. R. Chou, P. C. Huang, H. T. Fei, J. R. Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We study the responses of fluid-immersed soft hydrogel spheres that are sheared under controlled volume fractions. Slippery, deformable particles along with the density-matched interstitial fluid are sandwiched between two opposing rough cones, allowing studies for a wide range of volume fraction ϕ both above and below the jamming of granular suspension. We utilize sudden cessations of shearing, accompanied by refraction-matched internal imaging, to supplement the conventional flow-curve measurements. At sufficiently high volume fractions, the settling of particles after the cessations exhibits a continuous yet distinct transition over the change of the shear rate. Such changes back out the qualitative difference in the state of flowing prior to the cessations: the quasi-static yielding of a tightly packed network, as opposed to the rapid sliding of particles mediated by the interstitial fluid whose dynamics depends on the driving rate. In addition, we determine the solid-fluid transition using two independent methods: the extrapolation of stress residues and the estimated yield stress from high values of ϕ, and the settling of particles upon shear cessations as ϕ goes across the transition. We also verify the power law on values of characteristic stress with respect to the distance from jamming ϕ - ϕc, with an exponent close to 2. These results demonstrate a multitude of relaxation timescales behind the dynamics of soft particles, and raise questions on how we extend the existing paradigms of the flow of a densely packed system when the softness is actively involved.

Original languageEnglish
Pages (from-to)7535-7543
Number of pages9
JournalSoft Matter
Issue number32
Publication statusPublished - 2020 Aug 28
Externally publishedYes

ASJC Scopus subject areas

  • General Chemistry
  • Condensed Matter Physics


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