Granular Character of Particle Rafts

Abstract

We consider a monolayer of particles floating at a horizontal liquid-gas interface -- a particle raft. Upon compressing the monolayer in a Langmuir trough, the particles at first pack but ultimately the monolayer buckles out of the plane. We measure the stress profile within the raft at the onset of buckling and show for the first time that such systems exhibit a Janssen effect: the stress decays exponentially away from the compressing barriers over a length scale that depends on the width of the trough. We find quantitative agreement between the rate of decay and the simple theory presented by Janssen and others. This demonstrates that floating particle rafts have a granular, as well as elastic, character, which is neglected by current models. Finally, we suggest that our experimental setup may be suitable for exploring granular effects in two dimensions without the complications of gravity and basal friction.

4 pages, 4 figures, revised according to referees comments

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Cited by in corpus (16)

• Compressive consolidation of strongly aggregated particle gels
• Heterogeneous structure of granular aggregates with capillary interactions
• Wrinkles, folds and plasticity in granular rafts
• Shock driven jamming and periodic fracture of particulate rafts
• Amorphous to amorphous transition in particle rafts
• Buckling of self-assembled colloidal structures
• Strain localization and failure of disordered particle rafts with tunable ductility during tensile deformation
• The compression of a heavy floating elastic film
• From antinode clusters to node clusters: The concentration dependent transition of floaters on a standing Faraday wave
• Elasticity of Interfacial Rafts of Hard Particles with Soft Shells
• Progressive friction mobilization and enhanced Janssen's screening in confined granular rafts
• Collective motion of macroscopic spheres floating on capillary ripples: Dynamic heterogeneity and dynamic criticality
• Towards predicting shear-banding instabilities in lipid monolayers
• Cluster Formation and Relaxation in Particle Rafts under Uniform Radial Expansion
• Unjamming strongly compressed particle rafts
• Rheology of Granular Rafts