title: Nonlinear elasticity of microsphere heaps.
abstract: Thermal fluctuations, geometric exclusion, and external driving all govern the mechanical response of dense particulate suspensions. Here, we measure the stress-strain response of quasi-two-dimensional flow-stabilized microsphere heaps in a regime in which all three effects are present using a microfluidic device. We observe that the elastic modulus and the mean interparticle separation of the heaps are tunable via the confining stress provided by the fluid flow. Furthermore, the measured stress-strain curves exhibit a universal nonlinear shape, which can be predicted from a thermal van der Waals equation of state with excluded volume. This analysis indicates that many-body interactions contribute a significant fraction of the stress supported by the heap.
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Carlos P
authors.initials: CP
authors.lastname: Ortiz
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Daniels
authors.affiliation: Department of Physics, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Riehn
mesh_terms: D004548:Elasticity; D046210:Microfluidic Analytical Techniques; D008856:Microscopy, Fluorescence; D008863:Microspheres; D008962:Models, Theoretical; D017711:Nonlinear Dynamics