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Rheology and tribology at the nanoscale

Abstract : In this manuscript, we use a tuning fork based atomic force microscope to measure the mechanical response of various soft matter systems at the nanoscale. This instrument is used as a nano-rheometer, allowing quantitative measurements of viscoelastic material properties, and unprecedented characterization of friction and dissipation at the nanoscale. First, we show that ionic liquids can undergo a dramatic change in their mechanical properties when confined at the nanoscale, pointing to a capillary freezing transition. This transition is favored by the metallic nature of the confining substrates, suggesting the occurrence of subtle electrostatic effects in those dense electrolytes. Second, we probe plasticity at the individual atomic level, by measuring the viscoelastic rheological response of gold junctions of few atoms diameter. For increasing shear, we uncover a transition from a purely elastic regime to a plastic flow regime, up to the complete shear-induced melting of the junction. Our measurements give unprecedented insights on the plastic mechanisms at play in those molecular systems. Finally, we show that nanoscale interactions can have profound effects on the macroscopic behavior of soft materials. Focusing on the nonnewtonian flow behavior of concentrated suspensions of particles, we measure the nanoscale frictional force profile between pairs of particles of PVC and cornstarch suspensions. Our measurements highlight the dominant role of local interparticle interactions on the macroscale rheology of suspensions.
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Submitted on : Wednesday, April 17, 2019 - 5:33:08 PM
Last modification on : Wednesday, October 14, 2020 - 4:00:52 AM


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  • HAL Id : tel-02102888, version 1


Jean Comtet. Rheology and tribology at the nanoscale. Soft Condensed Matter [cond-mat.soft]. Université Paris sciences et lettres, 2018. English. ⟨NNT : 2018PSLEE027⟩. ⟨tel-02102888⟩



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