# Axelle Amon

Associate Professor

Email : axelle [dot] amon [at] univ-rennes1 [dot] fr

Phone : +33 223235038

Office number : 032/1 bât. 11A

## Latest news

Thermocapillary instability of an ionic liquid-water mixture in a temperature gradient

We have just published in Physical Review Fluids the experimental and theoretical study of a thermocapillary instability. We study a binary ionic liquid/water mixture which has the property to exhibit a phase separation around 30°C. By placing this mixture in a microfluidic cavity heated at its center, we have observed different phase separation dynamics that we have rationalized. In particular, we have given an interpretation in terms of a scaling law of the wavelength of the pattern observed in the regime presented in the figure as a function of the experimental parameters.

reference : M. Pascual, A. Amon, and M.-C. Jullien, Thermocapillary instability of an ionic liquid-water mixture in a temperature gradient, Phys. Rev. Fluids 6, 114203 (2021)

Nano-earthquakes at the scale of the lab.

We have just published in Communications Earth&Environment a study of plasticity fluctuations within a stationary shear band. We show that the macroscopic slip along the band is the result of the accumulation of local micro-slips whose sizes follow a scaling law distribution. Those local plastic events are correlated with each other. By studying their statistical properties, we show that these micro-slips share all the properties of earthquakes: the scaling laws we observe have the same exponents as those of the empirical laws describing earthquakes.

reference : D. Houdoux, A. Amon, D. Marsan, J. Weiss, and J. Crassous, Micro-slips in an experimental granular shear band replicate the spatiotemporal characteristics of natural earthquakes, Communications Earth & Environment 2, 90 (2021)

## Research interests

I am interested in modeling complex dynamics and self-organization problems in different phenomena by combining experimental, theoretical and numerical approaches.

My current research activities are mainly devoted to the mechanical response of granular material, including the question of the jamming/unjamming transition, the localization of the deformation and slow dense flows. One of the specificities of my activities in this field comes from the use of an original measurement method based on multiple light scattering in heterogeneous media and allowing to measure very small deformations.

I also work on the modeling of various nonlinear systems. In this last field my activity is theoretical and numerical in close collaboration with experimentalists.

Main research thematics
Avalanche precursors

We have studied quasi-periodic micro-failures occurring before the avalanche in a quasi-statically inclined granular material. We have proposed a model reproducing these events with only solid friction and elasticity as ingredients.

references :

Plasticity of amorphous materials

A granular material is a model medium to study the plasticity of amorphous materials. We have observed experimentally that the way plasticity organized in a granular media is in agreement with the theoretical scenario commonly accepted to describe the organization of plasticity in amorphous materials. We also studied numerically the response of a granular material to an imposed local event.

references :

• numerical study of the response of a granular medium to a local rearrangement: S. McNamara, J. Crassous, and A. Amon, Eshelby inclusions in granular matter: theory and simulations, Phys. Rev. E 94, 022907 (2016)
• experimental observation of the coupling between local events: A. Le Bouil, A. Amon, S. McNamara, and J. Crassous, Emergence of cooperativity in plasticity of soft glassy materials, Phys. Rev. Lett. 112, 246001 (2014)
• experimental observation of the local plastic events at the origin of the total macroscopic deformation of the material: A. Amon, V. B. Nguyen, A. Bruand, J. Crassous and E. Clément, Hot Spots in an Athermal System, Phys. Rev. Lett. 108, 135502 (2012)
Mechanical noise and fluidization of a granular material

In collaboration with E. Clément and A. Pons at the PMMH in Paris we studied the effect of mechanical noise on the creep response of a granular material. In particular, I proposed a multiple time scale approach modeling the action of the mechanical noise injected in the system in a conceptually different way than an Eyring model.

references :

• A. Pons, T. Darnige, J. Crassous, E. Clément, and A. Amon, Spatial repartition of the local processes at the origin of activated creep in a granular material, EPL 113, 28001 (2016)
• A. Pons, A. Amon, T. Darnige, J. Crassous, and E. Clément, Mechanical fluctuations suppress the threshold of soft-glassy solids: the secular drift scenario, Phys. Rev. E 92, 020201(R) (2015)
Localization of the deformation in a granular material

We study the way plasticity self-organizes during the loading of a granular material. We have identified the different steps of this organization, from the elastic coupling between local events to the concentration of plasticity in a stationary band.

references :

• characterization of the bifurcation at the origin of the localization in a granular medium : T. B. Nguyen and A. Amon, Experimental study of shear band formation: Bifurcation and localization, EPL 116, 28007 (2016)
• experimental observation of the local plastic events at the origin of the total macroscopic deformation of a granular material: A. Amon, V. B. Nguyen, A. Bruand, J. Crassous and E. Clément, Hot Spots in an Athermal System, Phys. Rev. Lett. 108, 135502 (2012)
• organization of plasticity in a granular medium before failure, coupling between local events: A. Le Bouil, A. Amon, S. McNamara, and J. Crassous, Emergence of cooperativity in plasticity of soft glassy materials, Phys. Rev. Lett. 112, 246001 (2014)
• co-existence of two orientations in the spatial distribution of the plasticity field during the loading of a granular medium: D. Houdoux, T. B. Nguyen, A. Amon, and J. Crassous, Plastic flow and localization in an amorphous material: Experimental interpretation of the fluidity, Phys. Rev. E 98, 022905 (2018)
Wave propagation in disordered materials

We have developed an interferometric method for measuring microstrain by multiple light scattering. This method allows to obtain spatially resolved maps of the local deformation with a deformation resolution of the order of 10-5, a resolution difficult to reach with other methods. This technique can be applied to any medium with index heterogeneities leading to strong light scattering. The light scattered by the medium then forms speckle patterns (see figure, right) which are modified when the material is deformed. The correlation in intensity between two speckle patterns is therefore related to the deformation and it is possible to quantify this dependence through a model. In a backscattering configuration, we have shown that it is possible to obtain spatially resolved correlation maps allowing to image the deformation in the medium with a resolution fixed by the transport length of the light in the medium (250 µm for Teflon, some grain sizes for glass beads).

references :

• review article on imaging techniques in granular media: A. Amon, P. Born, K. E. Daniels, J. A. Dijksman, K. Huang, D. Parker, M. Schröter, R. Stannarius, and A. Wierschem, Focus on Imaging Methods in Granular Physics, Rev. Sci. Instrum. 88, 051701 (2017)
• article detailing the method for measuring microstrain in a granular media: A. Amon, A. Mikhailovskaya, and J. Crassous, Spatially-resolved measurements of micro-deformations in granular materials using Diffusing Wave Spectroscopy, Rev. Sci. Instrum. 88, 051804 (2017)
• M. Erpelding, B. Dollet, A. Faisant, J. Crassous and A. Amon, Diffusing-Wave Spectroscopy Contribution To Strain Analysis, Strain 49, 167 (2013)
• M. Erpelding, A. Amon, and J. Crassous, Diffusive wave spectroscopy applied to the spatially resolved deformation of a solid, Phys. Rev. E 78, 046104 (2008)
Traffic of droplets in a microfluidic circuit

In collaboration with P. Panizza and L. Courbin from IPR, I modeled droplets traffic at a microfluidic junction. In this system, complex dynamics emerge from memory effects.

references :

• A. Amon, A. Schmit, L. Salkin, L. Courbin, and P. Panizza, Path selection rules for droplet trains in single-lane microfluidic networks, Phys. Rev. E 88, 013012 (2013)
• D. A. Sessoms, A. Amon, L. Courbin, and P. Panizza, Complex dynamics of droplet traffic in a bifurcating microfluidic network: Periodicity, multistability, and selection rules, Phys. Rev. Lett. 105, 154501 (2010)
•

## Publications

1. M. Pascual, A. Amon, and M.-C. Jullien, Thermocapillary instability of an ionic liquid-water mixture in a temperature gradient, Phys. Rev. Fluids 6, 114203 (2021)
2. D. Houdoux, A. Amon, D. Marsan, J. Weiss, and J. Crassous, Micro-slips in an experimental granular shear band replicate the spatiotemporal characteristics of natural earthquakes, Communications Earth & Environment 2, 90 (2021)
3. D. Houdoux, T. B. Nguyen, A. Amon, and J. Crassous, Plastic flow and localization in an amorphous material: Experimental interpretation of the fluidity, Phys. Rev. E 98, 022905 (2018)
4. A. Amon, B. Blanc, and J.-C. Géminard, Avalanche precursors in a frictional model, Phys. Rev. E 96, 033004 (2017)
5. A. Amon, P. Born, K. E. Daniels, J. A. Dijksman, K. Huang, D. Parker, M. Schröter, R. Stannarius, and A. Wierschem, Focus on Imaging Methods in Granular Physics, Rev. Sci. Instrum. 88, 051701 (2017)
6. A. Amon, A. Mikhailovskaya, and J. Crassous, Spatially-resolved measurements of micro-deformations in granular materials using Diffusing Wave Spectroscopy, Rev. Sci. Instrum. 88, 051804 (2017)
7. T. B. Nguyen and A. Amon, Experimental study of shear band formation: Bifurcation and localization, EPL 116, 28007 (2016)
8. S. McNamara, J. Crassous, and A. Amon, Eshelby inclusions in granular matter: theory and simulations, Phys. Rev. E 94, 022907 (2016)
9. A. Pons, T. Darnige, J. Crassous, E. Clément, and A. Amon, Spatial repartition of the local processes at the origin of activated creep in a granular material, EPL 113, 28001 (2016)
10. A. Pons, A. Amon, T. Darnige, J. Crassous, and E. Clément, Mechanical fluctuations suppress the threshold of soft-glassy solids: the secular drift scenario, Phys. Rev. E 92, 020201(R) (2015)
11. R. Lehoucq, J. Weiss, B. Dubrulle, A. Amon, A. Le Bouil, J. Crassous, D. Amitrano, F. Graner, Analysis of image versus position, scale and direction reveals pattern texture anisotropy, Front. Phys. 2, 84 (2015)
12. A. Le Bouil, A. Amon, S. McNamara, and J. Crassous, Emergence of cooperativity in plasticity of soft glassy materials, Phys. Rev. Lett. 112, 246001 (2014)
13. A. Le Bouil, A. Amon, J.-C. Sangleboeuf, H. Orain, P. Bésuelle, G. Viggiani, P. Chasle, and J. Crassous, A biaxial apparatus for the study of heterogeneous and intermittent strains in granular materials, Granular Matter 16, 1 (2014)
14. A. Amon, A. Schmit, L. Salkin, L. Courbin, and P. Panizza, Path selection rules for droplet trains in single-lane microfluidic networks, Phys. Rev. E 88, 013012 (2013)
15. A. Amon, R. Bertoni, and J. Crassous, Experimental Investigation of Plastic Deformations Before Granular Avalanche, Phys. Rev. E 87, 012204 (2013)
16. M. Erpelding, B. Dollet, A. Faisant, J. Crassous and A. Amon, Diffusing-Wave Spectroscopy Contribution To Strain Analysis, Strain 49, 167 (2013)
17. S. Lecomte, L. Reverdy, C. Le Quement, F. Le Masson, A. Amon, P. Le Goff, D. Michel, E. Christians and Y. Le Dréan, Unravelling Complex Interplay Between Heat Shock Factor 1 And 2 Splicing Isoforms, PLoS One 8, (2) e56085 (2013)
18. A. Amon, V. B. Nguyen, A. Bruand, J. Crassous and E. Clément, Hot Spots in an Athermal System, Phys. Rev. Lett. 108, 135502 (2012)
19. J. Crassous, A. Amon and J. Crassous, Circular differential scattering of polarized light by a chiral random medium, Phys. Rev. A 85, 023806 (2012)
20. F. Nicol-Benoit, A. Amon, C. Vaillant, P. le Goff, Y. le Dréan, F. Pakdel, G. Flouriot, Y. Valotaire, and D. Michel, A Dynamic Model of Transcriptional Imprinting Derived from Vitellogenesis Memory Effect, Biophys. J. 101, 1557 (2011)
21. D. A. Sessoms, A. Amon, L. Courbin, and P. Panizza, Complex dynamics of droplet traffic in a bifurcating microfluidic network: Periodicity, multistability, and selection rules, Phys. Rev. Lett. 105, 154501 (2010)
22. M. Erpelding, A. Amon, and J. Crassous, Mechanical response of granular media: New insights from Diffusing-Wave Spectroscopy, Europhys. Lett. 91, 18002 (2010)
23. J. Crassous, M. Erpelding, and A. Amon, Diffusive Waves in a Dilating Scattering Medium, Phys. Rev. Lett. 103, 013903 (2009)
24. A. Amon, P. Suret, S. Bielawski, D. Derozier, and M. Lefranc, Cooperative Oscillation of Nondegenerate Transverse Modes in an Optical System: Multimode Operation in Parametric Oscillators, Phys. Rev. Lett. 102, 183901 (2009)
25. M. Erpelding, A. Amon, and J. Crassous, Diffusive wave spectroscopy applied to the spatially resolved deformation of a solid, Phys. Rev. E 78, 046104 (2008)
26. A. Amon and M. Lefranc, Mode hopping strongly affects observability of dynamical instability in optical parametric oscillators, Eur. Phys. J. D. 44, 547 (2007)
27. M. Brunel, A. Amon, and M. Vallet, Dual-polarization microchip laser at 1.53 $\mu$m, Opt. Lett. 30, 2418 (2005)
28. A. Amon and M. Lefranc, Topological signature of deterministic chaos in short nonstationary signals from an optical parametric oscillator, Phys. Rev. Lett. 92, 094101 (2004)
29. A. Amon, M. Nizette, M. Lefranc and T. Erneux, Bursting oscillations in optical parametric oscillators, Phys. Rev. A 68, 023801 (2003)

## Teaching

Continuum Mechanics

Nonlinear Dynamics and Chaos

M2 lectures, lectures note (in English): https://cel.archives-ouvertes.fr/cel-01510146v2