Colloidal Suspensions can have Non-Zero Angles of Repose below the Minimal Value for Athermal Frictionless Particles
Abstract
We investigate the angle of repose θr of dense suspensions of colloidal silica particles (d = 2 m to 7 m) in water-filled microfluidic rotating drum experiments, to probe the crossover between the thermal (colloidal) and athermal (granular) regimes. For the smallest particles, thermal agitation promotes slow creep flows, and piles always flatten completely regardless of their initial inclination angle, resulting in θr = 0. Above a critical particle size, piles of colloids stop flowing at a finite angle of repose, which increases with particle size but remains below the minimal value expected for athermal frictionless granular materials: 0 < θr < θath ≈ 5.8°. We quantify the arrest dynamics as a function of the gravitational Péclet number Peg, which characterizes the competition between particle weight and thermal agitation. Our measurements are consistent with a recent rheological model [1], in which the arrested state stems from a crossover between glass and jamming transitions as the granular pressure in the pile increases relative to the thermal pressure.
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BibTeX
@article{fernandez2026colloidal,
title = {{Colloidal Suspensions can have Non-Zero Angles of Repose below the Minimal Value for Athermal Frictionless Particles}},
author = {Jesús Fernández and Loïc Vanel and Antoine Bérut},
journal = {Physical Review Letters},
year = {2026},
month = aug,
doi = {10.1103/hgfn-k4ql},
eprint = {2601.02291},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05734141v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Colloidal Suspensions can have Non-Zero Angles of Repose below the Minimal Value for Athermal Frictionless Particles
AU - Jesús Fernández
AU - Loïc Vanel
AU - Antoine Bérut
PY - 2026
DA - 2026/08/31
JO - Physical Review Letters
DO - 10.1103/hgfn-k4ql
UR - https://hal.science/hal-05734141v1
AB - We investigate the angle of repose θr of dense suspensions of colloidal silica particles (d = 2 m to 7 m) in water-filled microfluidic rotating drum experiments, to probe the crossover between the thermal (colloidal) and athermal (granular) regimes. For the smallest particles, thermal agitation promotes slow creep flows, and piles always flatten completely regardless of their initial inclination angle, resulting in θr = 0. Above a critical particle size, piles of colloids stop flowing at a finite angle of repose, which increases with particle size but remains below the minimal value expected for athermal frictionless granular materials: 0 < θr < θath ≈ 5.8°. We quantify the arrest dynamics as a function of the gravitational Péclet number Peg, which characterizes the competition between particle weight and thermal agitation. Our measurements are consistent with a recent rheological model [1], in which the arrested state stems from a crossover between glass and jamming transitions as the granular pressure in the pile increases relative to the thermal pressure.
SN - 0031-9007
SN - 1079-7114
ER -