various nonlinear phenomena unpredictable using the conventional single-intrachain
approach. The finite shear elasticity means that the flow is obtained at the price of an
overpassing an elastic threshold. Correlatively the shear viscosity indicates that the
fluid recovers its “static” elasticity after cessation of the constraint. The
low-frequency elasticity may explain unpredictable large time scale relaxations,
flow-induced instabilities (spurt effect, “shark-skin” instability), shear-induced
phases (Pujolle-Robic and Noirez 2001), the correlation between nanoparticles for
polymer melt reinforcement (Cassagnau 2003), nonlocal dielectric relaxation (Pronin et al. 2011) or nonuniform temperatures near a solid wall (Noirez et al. 2017),
and dynamic heterogeneities (Tracht et al. 1998a, b; Fischer 1983, 2002) involved in
the glass process (Brand and Kawasaki 2003).
The consideration of this neglected elastic property enables to predict novel
liquid properties as the shear-induced cooling or the establishment of coexisting
temperatures under microfluidic conditions. The microfluidic scale is certainly
the scale at which the elastic effects are the more visible. The shear elasticity has
been mainly detected at the submillimeter scale increasing as the sample dimension decreases. This dimension dependence is coherent with theoretical models
predicting static shear elasticity in fluids. On the basis of a survey of various
published results, Volino proposed a non-extensive model to describe the liquid
shear elasticity and where its dimension dependence is foreseen (Volino 1997).
Revisiting the Frenkel model, Trachenko shows the viscous term and the solidlike term can be treated on equal footing in the Maxwell interpolation (Trachenko
2017, Baggioli et al. 2019) Trachenko et al. introduce the concept of local
dynamic compressive stress and revisits the Maxwell approach showing that a
solid-like approach is also valid by introducing the notion of finite shear wave
propagation length (gapped momentum states) (Trachenko et al. 2016; Pronin
et al. 2011). These models converge in interpreting the macroscopic liquid
behavior as an asymptotic branch of a wider scheme where, at a smaller scale,
liquid molecules behave elastically and where the dynamic role of intermolecular
interactions is central (Zaccone 2011).
The existence of elastic correlations opens a new route in the approach of the
liquid state. The liquid behavior is impacted by more parameters (lengthscale
dependence, interfacial force boundaries, compressibilty effects) making its
applitive potential richer in particular thermal applications tuning, the flow energy
in a shear-induced cooling; and concern the flow mechanisms up to the most
confined physiological fluid of the chain of life.
Acknowledgments This work has benefited from the AAP2014 “Instrumentation aux limites”
CNRS funding. The author is very pleased to thank her collaborators, Patrick Baroni, Hakima
Mendil, Philipp, Kahl, Eni Kume and Ursula Windberger. She also would like to thank F. Volino,
F. Aitken, D. Aubry, K. Trachenko and A. Zaccone for discussions and theoretical feedback, and
R. Ewoldt for stimulating discussion around surface tension. A special thought to the late P.G. de
Gennes who chaired the first PhD thesis (www-llb.cea.fr/theses/mendil_2006.pdf) on the
low-frequency shear elasticity in fluids.
268
L. Noirez
approach. The finite shear elasticity means that the flow is obtained at the price of an
overpassing an elastic threshold. Correlatively the shear viscosity indicates that the
fluid recovers its “static” elasticity after cessation of the constraint. The
low-frequency elasticity may explain unpredictable large time scale relaxations,
flow-induced instabilities (spurt effect, “shark-skin” instability), shear-induced
phases (Pujolle-Robic and Noirez 2001), the correlation between nanoparticles for
polymer melt reinforcement (Cassagnau 2003), nonlocal dielectric relaxation (Pronin et al. 2011) or nonuniform temperatures near a solid wall (Noirez et al. 2017),
and dynamic heterogeneities (Tracht et al. 1998a, b; Fischer 1983, 2002) involved in
the glass process (Brand and Kawasaki 2003).
The consideration of this neglected elastic property enables to predict novel
liquid properties as the shear-induced cooling or the establishment of coexisting
temperatures under microfluidic conditions. The microfluidic scale is certainly
the scale at which the elastic effects are the more visible. The shear elasticity has
been mainly detected at the submillimeter scale increasing as the sample dimension decreases. This dimension dependence is coherent with theoretical models
predicting static shear elasticity in fluids. On the basis of a survey of various
published results, Volino proposed a non-extensive model to describe the liquid
shear elasticity and where its dimension dependence is foreseen (Volino 1997).
Revisiting the Frenkel model, Trachenko shows the viscous term and the solidlike term can be treated on equal footing in the Maxwell interpolation (Trachenko
2017, Baggioli et al. 2019) Trachenko et al. introduce the concept of local
dynamic compressive stress and revisits the Maxwell approach showing that a
solid-like approach is also valid by introducing the notion of finite shear wave
propagation length (gapped momentum states) (Trachenko et al. 2016; Pronin
et al. 2011). These models converge in interpreting the macroscopic liquid
behavior as an asymptotic branch of a wider scheme where, at a smaller scale,
liquid molecules behave elastically and where the dynamic role of intermolecular
interactions is central (Zaccone 2011).
The existence of elastic correlations opens a new route in the approach of the
liquid state. The liquid behavior is impacted by more parameters (lengthscale
dependence, interfacial force boundaries, compressibilty effects) making its
applitive potential richer in particular thermal applications tuning, the flow energy
in a shear-induced cooling; and concern the flow mechanisms up to the most
confined physiological fluid of the chain of life.
Acknowledgments This work has benefited from the AAP2014 “Instrumentation aux limites”
CNRS funding. The author is very pleased to thank her collaborators, Patrick Baroni, Hakima
Mendil, Philipp, Kahl, Eni Kume and Ursula Windberger. She also would like to thank F. Volino,
F. Aitken, D. Aubry, K. Trachenko and A. Zaccone for discussions and theoretical feedback, and
R. Ewoldt for stimulating discussion around surface tension. A special thought to the late P.G. de
Gennes who chaired the first PhD thesis (www-llb.cea.fr/theses/mendil_2006.pdf) on the
low-frequency shear elasticity in fluids.
268
L. Noirez