title: Stress controls the mechanics of collagen networks.
abstract: Collagen is the main structural and load-bearing element of various connective tissues, where it forms the extracellular matrix that supports cells. It has long been known that collagenous tissues exhibit a highly nonlinear stress-strain relationship, although the origins of this nonlinearity remain unknown. Here, we show that the nonlinear stiffening of reconstituted type I collagen networks is controlled by the applied stress and that the network stiffness becomes surprisingly insensitive to network concentration. We demonstrate how a simple model for networks of elastic fibers can quantitatively account for the mechanics of reconstituted collagen networks. Our model points to the important role of normal stresses in determining the nonlinear shear elastic response, which can explain the approximate exponential relationship between stress and strain reported for collagenous tissues. This further suggests principles for the design of synthetic fiber networks with collagen-like properties, as well as a mechanism for the control of the mechanics of such networks.
authors.affiliation: Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands;
authors.forename: Albert James
authors.initials: AJ
authors.lastname: Licup
authors.affiliation: Center for Medical Physics and Technology, Biophysics Group, Friedrich-Alexander Universität Erlangen-Nürnberg, 91052 Erlangen, Germany; School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138;
authors.forename: Stefan
authors.initials: S
authors.lastname: Münster
authors.affiliation: Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands;
authors.forename: Abhinav
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands;
authors.forename: Michael
authors.initials: M
authors.lastname: Sheinman
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA 02138.
authors.forename: Louise M
authors.initials: LM
authors.lastname: Jawerth
authors.affiliation: Center for Medical Physics and Technology, Biophysics Group, Friedrich-Alexander Universität Erlangen-Nürnberg, 91052 Erlangen, Germany;
authors.forename: Ben
authors.initials: B
authors.lastname: Fabry
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; Department of Physics, Harvard University, Cambridge, MA 02138.
authors.forename: David A
authors.initials: DA
authors.lastname: Weitz
authors.affiliation: Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands; fcmack@gmail.com.
authors.forename: Fred C
authors.initials: FC
authors.lastname: MacKintosh
mesh_terms: D001696:Biomechanical Phenomena; D024042:Collagen Type I / Q000737:chemistry*; D008954:Models, Biological; D013314:Stress, Mechanical
chemical_list: D024042:Collagen Type I
keywords: collagen networks; nonlinear elasticity; normal stress; tissue mechanics