title: Uncoupling shear and uniaxial elastic moduli of semiflexible biopolymer networks: compression-softening and stretch-stiffening.
abstract: Gels formed by semiflexible filaments such as most biopolymers exhibit non-linear behavior in their response to shear deformation, e.g., with a pronounced strain stiffening and negative normal stress. These negative normal stresses suggest that networks would collapse axially when subject to shear stress. This coupling of axial and shear deformations can have particularly important consequences for extracellular matrices and collagenous tissues. Although measurements of uniaxial moduli have been made on biopolymer gels, these have not directly been related to the shear response. Here, we report measurements and simulations of axial and shear stresses exerted by a range of hydrogels subjected to simultaneous uniaxial and shear strains. These studies show that, in contrast to volume-conserving linearly elastic hydrogels, the Young's moduli of networks formed by the biopolymers are not proportional to their shear moduli and both shear and uniaxial moduli are strongly affected by even modest degrees of uniaxial strain.
authors.affiliation: Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA.
authors.forename: Anne S G
authors.initials: AS
authors.lastname: van Oosten
authors.affiliation: Department of Physics and Astronomy, VU University, 1081HV Amsterdam, the Netherlands.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Vahabi
authors.affiliation: Department of Physics and Astronomy, VU University, 1081HV Amsterdam, the Netherlands.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Licup
authors.affiliation: Department of Physics and Astronomy, VU University, 1081HV Amsterdam, the Netherlands.|Third Institute of Physics, Georg August Universität, 37077 Göttingen, Germany.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA.|Department of Biomedical Engineering, Rowan University, Glassboro, NJ.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Galie
authors.affiliation: Department of Physics and Astronomy, VU University, 1081HV Amsterdam, the Netherlands.
authors.forename: Fred C
authors.initials: FC
authors.lastname: MacKintosh
authors.affiliation: Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Janmey
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D055119:Elastic Modulus; D004548:Elasticity; D011312:Pressure; D012212:Rheology; D033081:Shear Strength; D013314:Stress, Mechanical
chemical_list: D001704:Biopolymers