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Published November 14, 2017 | Supplemental Material + In Press + Published
Journal Article Open

Direct observation of impact propagation and absorption in dense colloidal monolayers


Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as "billiard balls" in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder.

Additional Information

© 2017 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). https://creativecommons.org/licenses/by-nc-nd/4.0/ Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved October 3, 2017 (received for review July 10, 2017). Published ahead of print October 30, 2017. We thank Ramakrishna Shivaprakash Narve for the Atomic Force Microscopy friction and adhesion data and Michele Zanini and Svetoslav Anachov for particle roughness measurement and analysis. L.I. and I.B. acknowledge financial support from Swiss National Science Foundation Grant PP00P2_144646/1 and ETH Postdoctoral Fellowship FEL-02 14-1. S.J. acknowledges financial support from the Agence Nationale de la Recherche and the Fondation de Recherche pour l'Aéronautique et l'Espace, Project METAUDIBLE ANR-13-BS09-0003-01. C.D. acknowledges Air Force Office of Scientific Research Center of Excellence Grant FA9550-12-1-0091. Author contributions: I.B., C.D., and L.I. designed research; I.B., J.C., W.-H.L., and S.J. performed research; I.B., J.C., W.-H.L., S.J., and L.I. analyzed data; and I.B., J.C., S.J., C.D., and L.I. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1712266114/-/DCSupplemental.

Attached Files

Published - PNAS-2017-Buttinoni-12150-5.pdf

Supplemental Material - pnas.1712266114.sm01.avi

Supplemental Material - pnas.1712266114.sm02.avi

Supplemental Material - pnas.1712266114.sm03.avi

Supplemental Material - pnas.1712266114.sm04.avi

In Press - PNAS-2017-Buttinoni-1712266114.pdf


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August 21, 2023
October 17, 2023