Publications

Articles in scientific journals

Books

Theses
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1. Articles in scientific journals
 Flexoelectric fluid membrane vesicles in spherical confinement
Niloufar Abtahi, Lila Bouzar, Nadia SaidiAmroun, Martin Michael Müller 
Abstract
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EPL, 131(1): 18001, 2020. See also 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.
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Math. Mech. Solids, 24: 4051, 2019. See also arXiv:1904.05855.
 Helical Superstructure of Intermediate Filaments
Lila Bouzar, Martin Michael Müller, René Messina, Bernd Nöding, Sarah Köster, Hervé Mohrbach, Igor M. Kulić 
Abstract
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Phys. Rev. Lett., 122: 098101, 2019. See also 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 
Abstract
Phys. Rev. E, 98: 043111, 2018. See also arXiv:1810.04500.
 Confining a fluid membrane vesicle of toroidal topology in an adhesive hard sphere
Lila Bouzar, Ferhat Menas, Martin Michael Müller 
Abstract
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IOP Conf. Series: MSE, 186: 012021, 2017.
 Squeezed helical elastica
Lila Bouzar, Martin Michael Müller, Pierre Gosselin, Igor M. Kulić, Hervé Mohrbach 
Abstract
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Eur. Phys. J. E, 39: 114, 2016. See also arXiv:1606.03611.
 How biofilaments twist membranes
Julien Fierling, Albert Johner, Igor M. Kulić, Hervé Mohrbach, Martin Michael Müller 
Abstract
Soft Matter, 12: 5747, 2016.
 Toroidal membrane vesicles in spherical confinement
Lila Bouzar, Ferhat Menas, Martin Michael Müller 
Abstract
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Phys. Rev. E, 92: 032721, 2015. See also 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.
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Int. J. NonLinear Mech., 75: 115, 2015. See also arXiv:1503.05030.
 Crunching Biofilament Rings
Julien Fierling, Martin Michael Müller, Hervé Mohrbach, Albert Johner, Igor M. Kulić 
Abstract
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Europhys. Lett., 107(6): 68002, 2014. See also arXiv:1408.6787.
 Confotronic dynamics of tubular filaments
Osman Kahraman, Hervé Mohrbach, Martin Michael Müller, Igor M. Kulić 
Abstract
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Soft Matter, 10(16): pp. 28362847, 2014. See also arXiv:1312.3106.
 Whirling skirts and rotating cones
Jemal Guven, J. A. Hanna, Martin Michael Müller 
Abstract
New J. Phys., 15: 113055, 2013. See also 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 
Abstract
J. Cell Sci., 126(8): 1806, 2013.
 Dipoles in thin sheets
Jemal Guven, J. A. Hanna, Osman Kahraman, Martin Michael Müller 
Abstract
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Eur. Phys. J. E, 36: 106, 2013. See also arXiv:1212.3262.
 Fluid membrane vesicles in confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller 
Abstract
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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 
The growth of a thin elastic sheet imposes constraints on its geometry such as its Gaussian curvature K_{G}.
In this paper, we construct the shapes of sympetalous bellshaped flowers with a constant Gaussian curvature. Minimizing the bending energies
of both the petal and the veins, we are able to predict quantitatively the global shape of these flowers. We discuss two toy problems
where the Gaussian curvature is either negative or positive. In the former case the axisymmetric pseudosphere turns out to mimic the correct
shape before edge curling; in the latter case, singularities of the mathematical surface coincide with strong veins. Using a variational
minimization of the elastic energy, we find that the optimal number for the veins is either four, five or six, a number which is deceptively
close to the statistics on real flowers in nature.
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New J. Phys., 14: 085014, 2012. Also featured in the Highlights of 2012.
 Morphogenesis of membrane invaginations in spherical confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller 
We study the morphology of a fluid membrane in spherical confinement. When the
area of the membrane is slightly larger than the area of the outer container, a single axisymmetric
invagination is observed. For higher area, selfcontact occurs: the invagination breaks symmetry
and deforms into an ellipsoidlike shape connected to its outer part via a small slit. For even
higher areas, a second invagination forms inside the original invagination. The folding patterns observed
could constitute basic building blocks in the morphogenesis of biological tissues and organelles.
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Europhys. Lett., 97(6): 68008, 2012. See also arXiv:1201.2518.
 Conical instabilities on paper
Jemal Guven, Martin Michael Müller, Pablo VázquezMontejo 
Abstract
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J. Phys. A: Math. Theor., 45(1): 015203, 2012. See also arXiv:1107.5008.
 Interfacemediated interactions: Entropic forces of curved membranes
Pierre Gosselin, Hervé Mohrbach, Martin Michael Müller 
Abstract
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Phys. Rev. E, 83(5): 051921, 2011. See also 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 
Abstract
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Phys. Rev. Lett., 105(6): 068101, 2010. See also arXiv:1007.1871.
 Cell Model Approach to Membrane Mediated Protein Interactions
Martin Michael Müller, Markus Deserno 
Abstract
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Prog. Theor. Phys. Suppl., 184: pp. 351363, 2010.
 Hamiltonian formulation of surfaces with constant Gaussian curvature
Miguel Trejo, Martine Ben Amar, Martin Michael Müller 
Abstract
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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.
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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 
Abstract
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Small, 5(7): pp. 832838, 2009.
 Conical Defects in Growing Sheets
Martin Michael Müller, Martine Ben Amar, Jemal Guven 
A growing or shrinking disc will adopt a conical shape, its intrinsic geometry characterized by a surplus angle φ_{e} at the apex. If growth is slow, the cone will find its equilibrium. Whereas this is trivial if φ_{e}≤0, the disc can fold into one of a discrete infinite number of states if φ_{e} is positive. We construct these states in the regime where bending dominates, determine their energies and how stress is distributed in them. For each state a critical value of φ_{e} is identified beyond which the cone touches itself. Before this occurs, all states are stable; the ground state has twofold symmetry.
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Phys. Rev. Lett., 101(15): 156104, 2008. See also 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.
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J. Phys. A: Math. Theor., 41(5): 055203, 2008. See also arXiv:0712.0978.
 Contact lines for fluid surface adhesion
Markus Deserno, Martin Michael Müller, Jemal Guven 
Abstract
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Phys. Rev. E, 76(1): 011605, 2007. See also condmat/0703019. Also featured in the Virtual Journal of Biological Physics Research.
 Balancing torques in membranemediated interactions: Exact results and
numerical illustrations
Martin Michael Müller, Markus Deserno, Jemal Guven 
Abstract
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Phys. Rev. E, 76(1): 011921, 2007. See also condmat/0702340. Also featured in the 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 
Abstract
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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 
Abstract
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Phys. Rev. E, 74(6): 061914, 2006. See also condmat/0602662. Also featured in the 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.
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Biophys. J., 91(1): pp. 217226, 2006.
 Interface mediated interactions between particles  a geometrical approach
Martin Michael Müller, Markus Deserno, Jemal Guven 
Particles bound to an interface interact because they deform its shape.
The stresses that result are fully encoded in the geometry and described
by a divergencefree surface stress tensor. This stress tensor can be
used to express the force on a particle as a line integral along any
conveniently chosen closed contour that surrounds the particle. The
resulting expression is exact (i.e., free of any 'smallness' assumptions)
and independent of the chosen surface parametrization. Additional surface
degrees of freedom, such as vector fields describing lipid tilt, are readily
included in this formalism. As an illustration, we derive the exact force
for several important surface Hamiltonians in various symmetric twoparticle
configurations in terms of the midplane geometry; its sign is evident in
certain interesting limits. Specializing to the linear regime, where the
shape can be analytically determined, these general expressions yield
forcedistance relations, several of which have originally been derived
by using an energy based approach.
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Phys. Rev. E, 72(6): 061407, 2005. See also condmat/0506019. Also featured in the Virtual Journal of Biological Physics Research.
 Geometry of surfacemediated interactions
Martin Michael Müller, Markus Deserno, Jemal Guven 
Soft interfaces can mediate interactions between particles bound to
them. The force transmitted through the surface geometry on a
particle may be expressed as a closed line integral of the surface
stress tensor around that particle. This contour may be deformed to
exploit the symmetries present; for two identical particles, one
obtains an exact expression for the force between them in terms of
the local surface geometry of their midplane; in the case of a
fluid membrane the sign of the interaction is often evident. The
approach, by construction, is adapted directly to the surface and is
independent of its parameterization. Furthermore, it is applicable
for arbitrarily large deformations; in particular, it remains valid
beyond the linear smallgradient regime.
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Europhys. Lett., 69(3): pp. 482488, 2005. See also condmat/0409043.
2. Books

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

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

Theoretical studies of fluid membrane mechanics, dissertation (2007).

Symmetry breaking in bioelasticity, habilitation thesis (2015).
