Biofilm

gro

wth

Morphogenesis of bacterial communities
Bio

con

vection

Light-controlled flows in active fluids
Bloom

for

mation

Irreversible collective migration of cyanobacteria in eutrophic conditions.

Welcome

I am a soft matter physicist working at the MSC lab at Paris Diderot University. I joined the DSHE team as a CNRS researcher in 2015.

Using theoretical and experimental tools, I study the morphogenesis of dense tissues such as biofilms or biomimetic systems. In collaboration with Philippe Brunet, I also work on collective effects, such as bioconvection or bloom formation, in suspension of micro-organisms. With Laurent Limat and Matthieu Roché, we investigate the physics of soft wetting.

Research

Bioconvection

Many photosynthetic micro-organisms are able to detect light and move towards optimal intensities. This ability, known as phototaxis, plays a major role in ecology by affecting natural phytoplankton mass transfers, and has important applications in bioreactor and artificial micro-swimmers technologies. We have shown that this property can be exploited to generate macroscopic fluid flows using a localized light source directed towards shallow suspensions of phototactic micro-organisms. These flows can thus be used as hydrodynamic tweezers to manipulate small floating objects.

Bloom formation

In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and signicantly degrade the quality of water resources. We successfully reproduced irreversible cyanobacterial blooms in vitro and by combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism allowing the sudden collective upward migration in test tubes of several cyanobacterial strains.

Biofilm growth

A general feature of mature biofilms is their highly heterogeneous architecture that partitions the microbial city into sectors with specific micro-environments. By constraining biofilms to grow approximately as two-dimensional layers, we found that the bacteria which differentiate to produce extracellular polymeric substances form tightly packed bacterial chains and that the biomass stickiness also strongly hinders the reorganization of cells within the biofilm. We also evidenced a process of kinetic roughening leading to the formation of a rough biofilm surface exhibiting self-similar properties.

Elastowetting

Soft substrates are deformed by placing liquid droplets on them. We experimentally studied both the static and dynamic surface deformations of very soft elastic PDMS gels by sessile or moving water droplets with a quantitative Schlieren optics. We rationalize our experiments with an analytical model accounting for the linear visco-elastic response of the gel bulk as well as its surface tension.

Morphogenesis

Much attention has been given to a noteworthy property of some soft tissues: their ability to grow. Many attempts have been made to model this behavior in biology, chemistry, and physics. Using the theory of finite elasticity, we have derived with Martine Ben Amar a set of equations describing the growth of thin elastic objects. Under appropriate scaling assumptions for the growth rates, the proposed model is of the Fo ̈ppl–von Ka ́rma ́n type.

Hydrogel swelling

Using swelling hydrogels, we have studied the evolution of a thin circular artificial tumor whose growth is confined at the periphery. When the volume of the outer proliferative ring increases, the tumor loses its initial symmetry and bifurcates towards an oscillatory shape. Depending on the geometrical and elastic parameters, we observe either a smooth large-wavelength undulation of the swelling layer or the formation of sharp creases at the free boundary.

Vesicle growth

We have studied the behavior of individual phospholipid vesicles in contact with fatty acids. We have show that spontaneous fatty acids insertion inside the bilayer is controlled by the vesicle size, osmotic pressure difference across the membrane and fatty acids concentration in the external bath. Depending on these parameters, vesicles can grow spherically or become unstable and fragment into several daughter vesicles. We establish the phase diagram for vesicle growth and we derive a simple thermodynamic model that reproduces the time evolution of the vesicle volume. Finally, we show that stable growth can be achieved on an artificial cell expressing a simple set of bacterial cytoskeletal proteins, paving the way toward artificial cell reproduction.

Nonlinear elasticity

Biological soft tissues develop mechanical stresses when they grow. In close association with biological factors, those stresses contribute to shape living objects. In this line of research, we have explored the coupling between growth and elasticity, with a strong focus on thin bodies, either free or confined in space. We have first derived a theory describing the deformations of a thin plate subjected to an arbitrary growth field. In this geometrical limit, the growth process has a simple and elegant interpretation : it is a source of mean and Gaussian curvatures. We have also studied a generic case of confined growth in which a thin sample is bounded on one side to an elastic substrate. The accessible deformations are drastically reduced and we investigate this physical situation in a mechanical model of melanoma development. In particular, we show that this confinement, frequently encoutered in animal tissues, can lead to a stress focusing during growth.

Internships

We are always looking for motivated students. If you are interested by our work and feel that you can contribute, please send us a mail.

Publications

Papers

Nonlinear Phototaxis and Instabilities in Suspensions of Light-Seeking Algae.
Ramamonjy A, Dervaux J & Brunet P.
Phys. Rev. Lett. 128: 258101 (2022). online - PDF

Spontaneous localized fluid release on swelling fibres.
Van de Velde P, Dervaux J, Protière S & Duprat C.
Soft Matter 18: 4565-4571 (2022). online - PDF

Thickness of epithelia on wavy substrates: measurements and continuous models.
Harmand N, Dervaux J, Poulard C & Hénon S.
Eur. Phys. J. E 45: 53 (2022). online - PDF

Evaporation of liquid coating a fiber.
Corpart M, Dervaux J, Poulard C, Restagno F & Boulogne F.
EPL, 139: 43001 (2022). online - PDF

Tip growth in morpho-elasticity.
Dervaux J & Ben Amar M.
C. R. Mécanique, 348(6-7): 613-625 (2020). online - PDF

A criterion for the pinning and depinning of an advancing contact line on a cold substrate.
Herbaut R, Dervaux J, Brunet P, Royon L & Limat L.
Eur. Phys. J. Spec. Top., 229: 1867-1880 (2020). online - PDF

Trapping of swimming microalgae in foam.
Roveillo Q, Dervaux J, Wang Y, Rouyer F, Zanchi D, Seuront L & Elias F.
J. R. Soc. Interface, 17: 20200077 (2020). online - PDF

Nonlinear theory of wetting on deformable substrates.
Roché M, Limat L & Dervaux J.
Soft Matter, 16: 5157-5176 (2020) online - PDF

Elastocapillary Ridge as a Noninteger Disclination.
Masurel R, Roché M, Limat L, Ionescu I & Dervaux J.
Phys. Rev. Lett., 122: 248004 (2019). online - PDF

Extraction of Silicone Uncrosslinked Chains at Air−Water−Polydimethylsiloxane Triple Lines.
Hourlier-Fargette A, Dervaux J, Antkowiak A & Neukirch S.
Langmuir, 34(41): 12244-12250 (2018) online - PDF

Geometrical control of dissipation during the spreading of liquids on soft solids.
Zhao M, Dervaux J, Narita T, Lequeux F, Limat L & Roché M.
PNAS, 115(8): 1748-1753 (2018) online - PDF

Growth and relaxation of a ridge on a soft poroelastic substrate.
Zhao M, Lequeux F, Narita T, Roché M, Limat L & Dervaux J.
Soft Matter, 14: 61-72 (2018) online - PDF

Numerical multiscale modelling of nonlinear elastowetting.
De Pascalis R, Dervaux J, Ionescu I & Limat L.
Eur. J. Mech. A, 71: 151-164 (2018) online - PDF

Growth and instability of a phospholipid vesicle in a bath of fatty acids.
Dervaux J, Noireaux V, & Libchaber A.
Eur. Phys. J. Plus, 132(6): 284 (2017). online - PDF

Diffusiophoretic manipulation of particles in a drop deposited on a hydrogel.
Boulogne F, Shin S, Dervaux J, Limat L & Stone HA.
Soft Matter, 13: 5122-5129 (2017). online - PDF

Light-controlled flows in active fluids.
Dervaux J, Capellazzi Resta M, & Brunet P.
Nature Physics, 13: 306–312 (2017). online - PDF

Homogeneous deposition of particles by absorption on hydrogels.
Boulogne F, Ingremeau F, Dervaux J, Limat L & Stone HA.
EPL, 112(4): 48004 (2015). online - PDF

Irreversible collective migration of cyanobacteria in eutrophic conditions.
Dervaux J, Méjean A & Brunet P.
PLoS One, 10(3): e0120906 (2015). online - PDF

Contact lines on soft solids with uniform surface tension: analytical solutions and double transition for increasing deformability.
Dervaux J & Limat L.
Proc. R. Soc. A, 471: 20140813 (2015). online - PDF

On growth and form of Bacillus subtilis biofilms.
Dervaux J, Magniez JC & Libchaber A.
Interface Focus, 4(6): 20130051 (2014). online - PDF

Mechanical Instabilities of gels.
Dervaux J & Ben Amar M.
Annu. Rev. Cond. Mat., 3:311-332 (2012). online - PDF

Shape transition in artificial tumors: from smooth buckles to singular creases.
Dervaux J, Couder Y, Guedeau-Boudeville MA & Ben Amar M.
Phys. Rev. Lett., 107: 018103 (2011). online - PDF

Buckling condensation in constrained growth.
Dervaux J & Ben Amar M.
J. Mech. Phys. Solids, 59: 538-560 (2011). online - PDF

Localized growth of layered tissues.
Dervaux J & Ben Amar M.
IMA J. Appl. Math., 75: 571-580 (2010). online - PDF

Elastic growth in thin geometries.
Dervaux J & Ben Amar M.
in Origins of Life : Self-Organization and/or Biological Evolution, edited by M. Gérin and M.-C. Maurel, 79-90 (2009). online - PDF

Morphogenesis of thin hyperelastic plates : a constitutive theory of biological growth in the Föppl-von Karman limit.
Dervaux J, Ciarletta P & Ben Amar M.
J. Mech. Phys. Solids, 57: 458 (2009). online - PDF

Morphogenesis of growing soft tissues.
Dervaux J & Ben Amar M.
Phys. Rev. Lett., 101: 068101 (2008). online - PDF

Thesis

Morphogenèse et élasticité en géométrie mince.
Julien Dervaux, under the direction of Martine Ben Amar
online - PDF