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1. Articles scientifiques
 Flexoelectric fluid membrane vesicles in spherical confinement
Niloufar Abtahi, Lila Bouzar, Nadia SaidiAmroun, Martin Michael Müller 
Résumé
Plus d'infos
EPL, 131(1): 18001, 2020. Cf. aussi arXiv:2006.04475.
 Isometric bending requires local constraints on free edges
Jemal Guven, Martin Michael Müller, Pablo VázquezMontejo 
While the shape equations describing the equilibrium of an unstretchable thin sheet that is free
to bend are known, the boundary conditions that supplement these equations on free edges have remained elusive.
Intuitively, unstretchability is captured by a constraint on the metric within the bulk. Naïvely one would then
guess that this constraint is enough to ensure that the deformations determining the boundary conditions on these
edges respect the isometry constraint. If matters were this simple, unfortunately, it would imply unbalanced torques
(as well as forces) along the edge unless manifestly unphysical constraints are met by the boundary geometry. In this
article, we identify the source of the problem: not only the local arclength but also the geodesic curvature need to
be constrained explicitly on all free edges. We derive the boundary conditions which follow. In contrast to conventional
wisdom, there is no need to introduce boundary layers. This framework is applied to isolated conical defects, both
with deficit as well, but more briefly, as surplus angles. Using these boundary conditions, we show that the lateral
tension within a circular cone of fixed radius is equal but opposite to the radial compression, and independent of
the deficit angle itself. We proceed to examine the effect of an oblique outer edge on this cone perturbatively
demonstrating that both the correction to the geometry as well as the stress distribution in the cone kicks in at
second order in the eccentricity of the edge.
Fermer
Plus d'infos
Math. Mech. Solids, 24: 4051, 2019. Cf. aussi arXiv:1904.05855.
 Helical Superstructure of Intermediate Filaments
Lila Bouzar, Martin Michael Müller, René Messina, Bernd Nöding, Sarah Köster, Hervé Mohrbach, Igor M. Kulić 
Résumé
Plus d'infos
Phys. Rev. Lett., 122: 098101, 2019. Cf. aussi arXiv:1803.04691.
 Vesicle dynamics in confined steady and harmonically modulated Poiseuille flows
Zakaria Boujja, Chaouqi Misbah, Hamid EzZahraouy, Abdelilah Benyoussef, Thomas John, Christian Wagner, Martin Michael Müller 
We present a numerical study of the timedependent motion of a membrane vesicle in a
channel under an imposed flow. In a Poiseuille flow the shape of the vesicle depends on the flow strength,
the mechanical properties of the membrane, and the width of the channel. In a wide parameter region, the
emerging snaking shape shows an oscillatory motion like a swimmer flagella even though the flow is
stationary. We quantify this behavior by the amplitude and frequency of the oscillations of the vesicle's
center of mass. The influence of an amplitude modulation of the imposed flow on the dynamics and shape of
the snaking vesicle is also investigated. We find that this modulationwhen sufficiently smallinduces
a modulation in amplitude and frequency of the center of mass of the snaking vesicle. For large
modulation amplitudes transitions to static shapes are observed.
Fermer
Phys. Rev. E, 98: 043111, 2018. Cf. aussi arXiv:1810.04500.
 Confining a fluid membrane vesicle of toroidal topology in an adhesive hard sphere
Lila Bouzar, Ferhat Menas, Martin Michael Müller 
Résumé
Plus d'infos
IOP Conf. Series: MSE, 186: 012021, 2017.
 Squeezed helical elastica
Lila Bouzar, Martin Michael Müller, Pierre Gosselin, Igor M. Kulić, Hervé Mohrbach 
Résumé
Plus d'infos
Eur. Phys. J. E, 39: 114, 2016. Cf. aussi arXiv:1606.03611.
 How biofilaments twist membranes
Julien Fierling, Albert Johner, Igor M. Kulić, Hervé Mohrbach, Martin Michael Müller 
Résumé
Soft Matter, 12: 5747, 2016.
 Toroidal membrane vesicles in spherical confinement
Lila Bouzar, Ferhat Menas, Martin Michael Müller 
Résumé
Plus d'infos
Phys. Rev. E, 92: 032721, 2015. Cf. aussi arXiv:1509.00765.
 Nonlinear buckling and symmetry breaking of a soft elastic sheet sliding on a cylindrical substrate
Norbert Stoop, Martin Michael Müller 
We consider the axial compression of a thin sheet wrapped around a rigid cylindrical substrate. In contrast to the wrinklingtofold transitions exhibited in similar systems, we find that the sheet always buckles into a single symmetric fold, while periodic solutions are unstable. Upon further compression, the solution breaks symmetry and stabilizes into a recumbent fold. Using linear analysis and numerics, we theoretically predict the buckling force and energy as a function of the compressive displacement. We compare our theory to experiments employing cylindrical neoprene sheets and find remarkably good agreement.
Fermer
Plus d'infos
Int. J. NonLinear Mech., 75: 115, 2015. Cf. aussi arXiv:1503.05030.
 Crunching Biofilament Rings
Julien Fierling, Martin Michael Müller, Hervé Mohrbach, Albert Johner, Igor M. Kulić 
We discuss a curious example for the collective mechanical behavior of coupled nonlinear monomer units entrapped in a circular filament. Within a simple model we elucidate how multistability of monomer units and exponentially large degeneracy of the filament's ground state emerge as a collective feature of the closed filament. Surprisingly, increasing the monomer frustration, i.e., the bending prestrain within the circular filament, leads to a conformational softening of the system. The phenomenon, that we term polymorphic crunching, is discussed and applied to a possible scenario for membrane tube deformation by switchable dynamin or FtsZ filaments. We find an important role of cooperative interunit interaction for efficient ring induced membrane fission.
Fermer
Plus d'infos
Europhys. Lett., 107(6): 68002, 2014. Cf. aussi arXiv:1408.6787.
 Confotronic dynamics of tubular filaments
Osman Kahraman, Hervé Mohrbach, Martin Michael Müller, Igor M. Kulić 
Résumé
Plus d'infos
Soft Matter, 10(16): pp. 28362847, 2014. Cf. aussi arXiv:1312.3106.
 Whirling skirts and rotating cones
Jemal Guven, J. A. Hanna, Martin Michael Müller 
Résumé
New J. Phys., 15: 113055, 2013. Cf. aussi arXiv:1306.2619.
 Myotubularin and PtdIns3P remodel the sarcoplasmic reticulum in muscle in vivo
Leonela Amoasii, Karim Hnia, Gaëtan Chicanne, Andreas Brech, Belinda Simone Cowling, Martin Michael Müller, Yannick Schwab, Pascale Koebel, Arnaud Ferry, Bernard Payrastre, Jocelyn Laporte 
The sarcoplasmic reticulum (SR) is a specialized form of endoplasmic reticulum (ER) in skeletal muscle
and is essential for calcium homeostasis. The mechanisms involved in SR
remodeling and maintenance of SR subdomains are elusive. In this study, we identified
myotubularin (MTM1), a phosphatase mutated in Xlinked centronuclear myopathy
(XLCNM), as a key regulator of phosphoinositide3monophosphate (PtdIns3P) levels at the
SR. Mtm1 deficient mouse muscles and myoblasts from XLCNM patients exhibit abnormal
SR/ER networks. In vivo modulation of MTM1 enzymatic activity in muscle using ectopic
expression of wildtype or a deadphosphatase MTM1 protein leads to differential SR
remodeling. Active MTM1 is associated to flat membrane stacks, while deadphosphatase
MTM1 mutant promotes highly curved cubic membranes originating from the SR and
enriched in PtdIns3P. Moreover, expression of the PtdIns3P binding module 2XFYVE also
modified the SR shape at triads. Our findings, supported by the parallel analysis of the Mtm1
null mouse and in vivo study, reveal a direct function of MTM1 enzymatic activity in SR
remodeling and a key role for its substrate PtdIns3P in promoting SR membrane curvature in
skeletal muscle. We propose that alteration in SR remodeling is a primary cause of Xlinked
centronuclear myopathy. The tight regulation of PtdIns3P on specific membrane subdomains
may be a general mechanism to control membrane curvature.
Fermer
J. Cell Sci., 126(8): 1806, 2013.
 Dipoles in thin sheets
Jemal Guven, J. A. Hanna, Osman Kahraman, Martin Michael Müller 
Résumé
Plus d'infos
Eur. Phys. J. E, 36: 106, 2013. Cf. aussi arXiv:1212.3262.
 Fluid membrane vesicles in confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller 
Résumé
Plus d'infos
New J. Phys., 14: 095021, 2012.
 Petal shapes of sympetaleous flowers: the interplay between growth, geometry and elasticity
Martine Ben Amar, Martin Michael Müller, Miguel Trejo 
Résumé
Plus d'infos
New J. Phys., 14: 085014, 2012. Choisi pour les Highlights of 2012.
 Morphogenesis of membrane invaginations in spherical confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller 
Résumé
Plus d'infos
Europhys. Lett., 97(6): 68008, 2012. Cf. aussi arXiv:1201.2518.
 Conical instabilities on paper
Jemal Guven, Martin Michael Müller, Pablo VázquezMontejo 
Résumé
Plus d'infos
J. Phys. A: Math. Theor., 45(1): 015203, 2012. Cf. aussi arXiv:1107.5008.
 Interfacemediated interactions: Entropic forces of curved membranes
Pierre Gosselin, Hervé Mohrbach, Martin Michael Müller 
Particles embedded in a fluctuating interface experience forces and torques
mediated by the deformations and by the thermal fluctuations of the medium.
Considering a system of two cylinders bound to a fluid membrane we show that
the entropic contribution enhances the curvaturemediated repulsion between
the two cylinders. This is contrary to the usual attractive Casimir force in
the absence of curvaturemediated interactions. For a large distance between
the cylinders, we retrieve the renormalization of the surface tension of a
flat membrane due to thermal fluctuations.
Fermer
Plus d'infos
Phys. Rev. E, 83(5): 051921, 2011. Cf. aussi arXiv:1011.1221.
 SelfContact and Instabilities in the Anisotropic Growth of Elastic Membranes
Norbert Stoop, Falk K. Wittel, Martine Ben Amar, Martin Michael Müller, Hans J. Herrmann 
We investigate the morphology of thin discs and rings growing in circumferential direction. Recent analytical results suggest that this growth produces symmetric excess cones (econes). We study the stability of such solutions considering selfcontact and bending stress. We show that, contrary to what was assumed in previous analytical solutions, beyond a critical growth factor, no symmetric econe solution is energetically minimal any more. Instead, we obtain skewed econe solutions having lower energy, characterized by a skewness angle and repetitive spiral winding with increasing growth. These results are generalized to discs with varying thickness and rings with holes of different radii.
Fermer
Plus d'infos
Phys. Rev. Lett., 105(6): 068101, 2010. Cf. aussi arXiv:1007.1871.
 Cell Model Approach to Membrane Mediated Protein Interactions
Martin Michael Müller, Markus Deserno 
Résumé
Plus d'infos
Prog. Theor. Phys. Suppl., 184: pp. 351363, 2010.
 Hamiltonian formulation of surfaces with constant Gaussian curvature
Miguel Trejo, Martine Ben Amar, Martin Michael Müller 
Dirac's method for constrained Hamiltonian systems is used to describe surfaces of constant Gaussian curvature. A geometrical free energy, for which these surfaces are equilibrium states, is introduced and interpreted as an action. An equilibrium surface can then be generated by the evolution of a closed space curve.
Since the underlying action depends on second derivatives, the velocity of the curve and its conjugate momentum must be included in the set of phase space variables. Furthermore, the action is linear in the acceleration of the curve and possesses a local symmetryreparametrization invariancewhich implies primary constraints in the canonical formalism. These constraints are incorporated into the Hamiltonian through Lagrange multiplier functions, that are identified as the components of the acceleration of the curve. The formulation leads to four first order partial differential equations, one for each canonical variable.
With the appropriate choice of parametrization only one of these equations has to be solved to obtain the surface which is swept out by the evolving space curve. To illustrate the formalism, several evolutions of pseudospherical surfaces are discussed.
Fermer
Plus d'infos
J. Phys. A: Math. Theor., 42(42): 425204, 2009.
 Local Membrane Mechanics of PoreSpanning Bilayers
Ingo Mey, Milena Stephan, Eva K. Schmitt, Martin Michael Müller, Martine Ben Amar, Claudia Steinem, Andreas Janshoff 
The mechanical behavior of lipid bilayers spanning the pores of highly ordered porous silicon substrates was studied by local indentation experiments as a function of surface functionalization, lipid composition, solvent content, indentation velocity, and pore radius. Solventcontaining nanoblack lipid membranes (nanoBLMs) as well as solventfree porespanning bilayers were imaged by fluorescence and atomic force microscopy prior to force curve acquisition, which allows distinguishing between membranecovered and uncovered pores. Force indentation curves on porespanning bilayers attached to functionalized hydrophobic porous silicon substrates reveal a predominately linear response that is mainly attributed to prestress in the membranes. This is in agreement with the observation that indentation leads to membrane lysis well below 5% area dilatation. However, membrane bending and lateral tension dominates over
prestress and stretching if solventfree supported membranes obtained from spreading giant liposomes on hydrophilic porous silicon are indented.
Fermer
Plus d'infos
J. Am. Chem. Soc., 131(20): pp. 70317039, 2009.
 Elasticity Mapping of PoreSuspending Native Cell Membranes
Bärbel Lorenz, Ingo Mey, Siegfried Steltenkamp, Tamir Fine, Christina Rommel, Martin Michael Müller, Alexander Maiwald, Joachim Wegener, Claudia Steinem, Andreas Janshoff 
Résumé
Plus d'infos
Small, 5(7): pp. 832838, 2009.
 Conical Defects in Growing Sheets
Martin Michael Müller, Martine Ben Amar, Jemal Guven 
Résumé
Plus d'infos
Phys. Rev. Lett., 101(15): 156104, 2008. Cf. aussi arXiv:0807.1814.
 How paper folds: bending with local constraints
Jemal Guven, Martin Michael Müller 
A variational framework is introduced to describe how a surface bends when it is subject to local constraints on its geometry. This framework is applied to describe the patterns of a folded sheet of paper. The unstretchability of paper implies a constraint on the surface metric; bending is penalized by an energy quadratic in mean curvature. The local Lagrange multipliers enforcing the constraint are identified with a conserved tangential stress that couples to the extrinsic curvature of the sheet. The framework is illustrated by examining the deformation of a flat sheet into a generalized cone.
Fermer
Plus d'infos
J. Phys. A: Math. Theor., 41(5): 055203, 2008. Cf. aussi arXiv:0712.0978.
 Contact lines for fluid surface adhesion
Markus Deserno, Martin Michael Müller, Jemal Guven 
Résumé
Plus d'infos
Phys. Rev. E, 76(1): 011605, 2007. Cf. aussi condmat/0703019. Choisi pour le Virtual Journal of Biological Physics Research.
 Balancing torques in membranemediated interactions: Exact results and
numerical illustrations
Martin Michael Müller, Markus Deserno, Jemal Guven 
Torques on interfaces can be described by a divergencefree tensor
which is fully encoded in the geometry. This tensor consists of two
terms, one originating in the couple of the stress, the other capturing
an intrinsic contribution due to curvature. In analogy to the description
of forces in terms of a stress tensor, the torque on a particle can be
expressed as a line integral along any contour surrounding the particle.
Interactions between particles mediated by a fluid membrane are studied
within this framework. In particular, torque balance places a strong
constraint on the shape of the membrane. Symmetric twoparticle
configurations admit simple analytical expressions which are valid
in the fully nonlinear regime; in particular, the problem may be
solved exactly in the case of two membranebound parallel cylinders.
This apparently simple system provides some flavor of the remarkably
subtle nonlinear behavior associated with membranemediated interactions.
Fermer
Plus d'infos
Phys. Rev. E, 76(1): 011921, 2007. Cf. aussi condmat/0702340. Choisi pour le Virtual Journal of Biological Physics Research.
 Aggregation and vesiculation of membrane proteins by curvaturemediated
interactions
Benedict J. Reynwar, Gregoria Illya, Vagelis A. Harmandaris, Martin Michael Müller, Kurt Kremer, Markus Deserno 
Résumé
Plus d'infos
Nature 447(7143): pp. 461464, 2007.
 How to determine local elastic properties of lipid bilayer membranes
from atomicforcemicroscope measurements: A theoretical analysis
Davood Norouzi, Martin Michael Müller, Markus Deserno 
Résumé
Plus d'infos
Phys. Rev. E, 74(6): 061914, 2006. Cf. aussi condmat/0602662. Choisi pour le Virtual Journal of Biological Physics Research.
 Mechanical Properties of PoreSpanning Lipid Bilayers Probed by Atomic Force Microscopy
Siegfried Steltenkamp, Martin Michael Müller, Markus Deserno, Christian Hennesthal, Claudia Steinem, Andreas Janshoff 
We measure the elastic response of a freestanding lipid membrane to a local indentation by using an atomic force microscope. Starting point is a planar
goldcoated alumina substrate with a chemisorbed 3mercaptopropionic acid
monolayer displaying circular pores of very well defined and tunable size, over
which bilayers composed of N,N, dimethyl N,N, dioctadecylammonium bromide or
1,2  dioleoyl  3  trimethylammonium  propane chloride were spread.
Centrally indenting these 'nanodrums' with an atomic force microscope tip yields
forceindentation curves, which we quantitatively analyze by solving the
corresponding shape equations of continuum curvature elasticity. Since the
measured response depends in a known way on the system geometry (pore size, tip
radius) and on material parameters (bending modulus, lateral tension), this opens
the possibility to monitor local elastic properties of lipid membranes in a
wellcontrolled setting.
Fermer
Plus d'infos
Biophys. J., 91(1): pp. 217226, 2006.
 Interface mediated interactions between particles  a geometrical approach
Martin Michael Müller, Markus Deserno, Jemal Guven 
Résumé
Plus d'infos
Phys. Rev. E, 72(6): 061407, 2005. Cf. aussi condmat/0506019. Choisi pour le Virtual Journal of Biological Physics Research.
 Geometry of surfacemediated interactions
Martin Michael Müller, Markus Deserno, Jemal Guven 
Résumé
Plus d'infos
Europhys. Lett., 69(3): pp. 482488, 2005. Cf. aussi condmat/0409043.
2. Livres

New Trends in the Physics and Mechanics of Biological Systems
Lecture Notes of the Les Houches Summer School, vol. 92 (Oxford University Press, 2011),
éd. par Martine Ben Amar, Alain Goriely, Martin Michael Müller et Leticia Cugliandolo.
Chapitre 9 :
The physics of the cell membrane
Martin Michael Müller et Martine Ben Amar.
3. Mémoires

Theoretical examinations of interface mediated interactions between colloidal particles,
mémoire (2004).

Theoretical studies of fluid membrane mechanics, thèse de doctorat (2007).

Symmetry breaking in bioelasticity, thèse d'habilitation à diriger des recherches (2015).
