Position: Professor at Ensem, Nancy, France.
LEMTA (Laboratory of Energetics and Theoretical and Applied Mechanics).
Group of Biomechanics and Bioengineering.
Email : jean-francois.Ganghoffer@ensem.inpl-nancy.fr
The main actual research topic is biomechanics and bioengineering. Activities are intended to cover a large spectrum of disciplines required in this field (biology, mechanics of materials, continuum mechanics, applied mathematics, computational methods) in a pluridisciplinary approach by essence. From a fundamental viewpoint, sophisticated methods from micromechanics (homogenization methods), Eshelbian mechanics and continuous symmetries, thermodynamics of irreversible processes or shape / topology optimization, are currently used and developed. Models for soft living tissue are elaborated, from the cell level (cell adhesion and motility) up to tissue level, including the simulation of morphological evolutions such as surface growth (bones) and volumetric growth (soft tissues). Tissue engineering is also an important multidisciplinary research activity. The anterior cruciate ligament (ACL) is the most commonly injured ligament of the knee. Some limitations of current treatment options, especially in terms of mechanical properties, have prompted a growing interest in tissue-engineered solutions. A tissue-engineered ACL must fulfil precise specifications: it has to be biodegradable, biocompatible, porous, very similar to the native ACL in terms of overall mechanical behaviour, and it must promote the formation of ligamentous tissue. Our works aim at designing, simulating and elaborating a new tissue-engineered ACL which best fulfils those expectations.
1. Growth of soft and hard biological tissues: volumetric growth models suitable for soft living tissues and surface growth models appropriate for hard tissues (with a special emphasis of bone) are currently developed, within the framework of chemomechanics. In the case of bone growth and remodelling, the proposed framework involves multiphysical models coupling the kinetics of dissolution of HA (Hydroxyapatite), the temporal evolution of the superficial density of minerals, and the determination of the surface growth velocity in relation to the driving force for growth. Those driving forces are established within the framework of the irreversible thermodynamics of open systems and under the umbrella of configurational mechanics; they reflect both the chemical and mechanical antagonist factors responsible for bone remodelling. The mechanical properties of bone are predicted from the homogenization of the trabecular architecture, and surface growth models are currently developed to predict bone internal and external remodelling. Works in progress aim at modelling the internal remodelling at the trabecular level.
2. Mechanics of biological membranes.
Biological membranes are essential constituents of biological cells, as they play both a protective, chemical (they are semi-permeable, allowing diffusion of chemical species) and structural role (mechanical resistance to deformation). Many biological tissues can be considered from a mechanical point of view as a membrane, i.e., as a sheet-like structure because of their small thickness from a geometrical viewpoint. Many bio-membranes present a fibrous structure, with stiff fibers, sometimes with preferential orientations, embedded in a more compliant matrix. Typical examples of those tissues include the arterial walls, the amniotic membrane, or the skin. Biomembranes accordingly display a rich behavior on mesoscopic length scales, and our goal is to construct micromechanical or statistical models accounting for the presence of a fibrous structure. Especially, we have developed discrete homogenization techniques to construct the effective continuum from the initially discrete structure. FE2 simulations are currently developed to simulate the shape evolutions of membranes.
3. Conception, characterization and simulation of substitutes for ligaments and tendons.
The anterior cruciate ligament (ACL) is the most commonly injured ligament of the knee. Some limitations of current treatment options, especially in terms of mechanical properties, have prompted a growing interest in tissue-engineered solutions. A tissue-engineered ACL must fulfil precise specifications: it has to be biodegradable, biocompatible, porous, very similar to the native ACL in terms of overall mechanical behaviour, and it must promote the formation of ligamentous tissue. Our works aim at designing, simulating and producing a new tissue-engineered ACL which best fulfils those expectations. Mechanotransduction is a fundamental aspect to be investigated in the near future, involving close interactions between appropriate experiments and models to be developed at the cellular level.
4. Mechanical models of fibrous media.
Multiscale mechanical models for fibrous artificial (scaffolds) and biological media (biomembranes) are developed, starting from the level of the yarn. Such structures are discrete by nature and show strong couplings and interactions (contact, friction) between the structural elements (yarns), leading overall to nonlinear behaviours. Micromechanical techniques are currently developed to construct hyperelastic anisotropic models from the homogenization of the (discrete) architecture of the armour for plain weave and fabric built as mono or multilayers.
– ‘Equivalent mechanical properties of auxetic lattices from discrete homogenization’. F. Dos Reis, J.F. Ganghoffer. Comput. Mat. Science. 2011, 51, 314-321.
– ‘Equivalent properties of monolayer fabric from mesoscopic modelling strategies’. M. Assidi, B. Ben Boubaker, J.F. Ganghoffer. Int. J. Solids Struct., 48, Issue 20, 1 October 2011, 2920-2930.
– ‘Mechanics and thermodynamics of surface growth viewed as moving discontinuities’. Mech. Res. Comm., 38, 2011, 372-377.
- ‘Equivalent properties of Biological Membranes from Lattice Homogenization’. M. Assidi, F. Dos Reis, J.F. Ganghoffer. Journal of the Mechanical Behavior of Biomedical Materials. 2011, doi: 10.1016/j.jmbbm.2011.05.040.
– ‘A contribution to the mechanics and thermodynamics of surface growth. Application to bone external remodeling’. Int. J. Engng Sci. 2011, doi: 10.1016/j.ijengsci.2011.08.004.
- ‘Eshelby tensors, thermodynamics and calculus of variations. Application to volumetric growth’. J.F. Ganghoffer. Int. J. Egng Sci. 48, Issue 12, 2010, 2081-2098.
- ‘Stochastic modelling of the aggregation of cells during their rolling’. N. Mefti, N. Kabouya, J.F. Ganghoffer. J. Biomechanics. 43, Issue 2, 2010, 248-253.
- ‘Discrete homogenization of architectured materials: implementation of the method in a simulation tool for the systematic prediction of their effective elastic properties’. F. Dos Reis, J.F. Ganghoffer. Technische Mechanik, 2010. 30, 1-3, 85-109.
- ‘Relevance of symmetry methods in mechanics of materials’. J.F. Ganghoffer, V. Magnenet, R. Rahouadj. Int. J. Engng Math. 66, 2010, 103-119.
– ‘Morphological characterization of a novel scaffold for anterior cruciate ligament tissue engineering’. C. P. Laurent, J.F. Ganghoffer, J. Babin, J.L. Six, X. Wang, R. Rahouadj. J. Biomechanical Engng, 133, 2011, 065001-1-065001-9.
– ‘Analytical description of the shapes of the beaded nerve fibers’. M.. Hadzhilazova, J.F. Ganghoffer, I. Mladenov. Compte Rendu Académie des Sciences Bulgares, Sofia, August 2010. 66, Issue 1-3, 103-119.
– ‘Mechanical modeling of growth considering domain variation Part II: volumetric and surface growth involving Eshelby tensors’. J.F. Ganghoffer. J. Mech. Phys. Solids. 2010. DOI: 10.1016/j.jmps.2010.05.003.
- ‘On the virial theorem and Eshelby stress’. J.F. Ganghoffer. Int. J. Solids Struct., 2010. 47, No. 9, 1209-1220.
- ‘Continuous symmetry analysis of a dissipative constitutive law: application to the time-temperature superposition’. V. Magnenet, R. Rahouadj, J.F. Ganghoffer, C. Cunat. European Journal of Mechanics - A/Solids, 28, Issue 4, 2009, 744-751.
- ‘Finite element simulation of interactions between pelvic organs: predictive model of the prostate motion in the context of radiotherapy’. M. B. Boubaker, J.-F. Ganghoffer, M. Haboussi, P. A.. Aletti. J. Biomechanics. 2009, 25;42(12):1862-1868.
– ‘Consideration of the yarn-yarn interactions in meso/macro discrete model of fabric. Part I: single yarn behaviour’. B. Ben Boubaker, B. Haussy, J.F. Ganghoffer. Mech. Res. Comm. 34, Issue 4, 2007, 359-370. Part II: Woven fabric under uniaxial and biaxial extension’. Mech. Res. Comm. 34, Issue 4, 2007, 371-379.