title: Determination and validation of the elastic moduli of small and complex biological samples: bone and keratin in bird beaks.
abstract: In recent years, there has been a surge in the development of finite-element (FE) models aimed at testing biological hypotheses. For example, recent modelling efforts suggested that the beak in Darwin's finches probably evolved in response to fracture avoidance. However, knowledge of the material properties of the structures involved is crucial for any model. For many biological structures, these data are not available and may be difficult to obtain experimentally given the complex nature of biological structures. Beaks are interesting as they appear to be highly optimized in some cases. In order to understand the biomechanics of this small and complex structure, we have been developing FE models that take into account the bilayered structure of the beak consisting of bone and keratin. Here, we present the results of efforts related to the determination and validation of the elastic modulus of bone and keratin in bird beaks. The elastic moduli of fresh and dried samples were obtained using a novel double-indentation technique and through an inverse analysis. A bending experiment is used for the inverse analysis and the validation of the measurements. The out-of-plane displacements during loading are measured using digital speckle pattern interferometry.
authors.affiliation: Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, B2020 Antwerpen, Belgium. joris.soons@ua.ac.be
authors.forename: Joris
authors.initials: J
authors.lastname: Soons
authors.forename: Anthony
authors.initials: A
authors.lastname: Herrel
authors.forename: Peter
authors.initials: P
authors.lastname: Aerts
authors.forename: Joris
authors.initials: J
authors.lastname: Dirckx
mesh_terms: D000818:Animals; D001502:Beak / Q000737:chemistry* / Q000502:physiology*; D001842:Bone and Bones / Q000737:chemistry* / Q000502:physiology*; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D046369:Finches; D007633:Keratins / Q000737:chemistry* / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical
chemical_list: D007633:Keratins
references.citation: Proc Biol Sci. 2010 Jul 22;277(1691):2193-8
references.pmid: 20236981
references.citation: J Biomech. 2009 Jun 19;42(9):1224-9
references.pmid: 19394021
references.citation: Anat Rec A Discov Mol Cell Evol Biol. 2005 Apr;283(2):259-74
references.pmid: 15747355
references.citation: Philos Trans R Soc Lond B Biol Sci. 2010 Apr 12;365(1543):1093-8
references.pmid: 20194171
references.citation: J R Soc Interface. 2012 Feb 7;9(67):351-61
references.pmid: 21752810
references.citation: Anat Rec A Discov Mol Cell Evol Biol. 2005 Apr;283(2):275-87
references.pmid: 15747346
references.citation: Anat Rec A Discov Mol Cell Evol Biol. 2005 Apr;283(2):253-8
references.pmid: 15754323
references.citation: J Mech Behav Biomed Mater. 2008 Jul;1(3):208-26
references.pmid: 19627786
references.citation: J Anat. 2011 Jan;218(1):47-58
references.pmid: 20846282
references.citation: J Anat. 2011 Jan;218(1):1-2
references.pmid: 21197696
references.citation: J Anat. 2011 Dec;219(6):676-95
references.pmid: 21999913
references.citation: Science. 1981 Oct 2;214(4516):82-5
references.pmid: 17802577
references.citation: J Morphol. 2011 Nov;272(11):1388-98
references.pmid: 21755526
references.citation: Hear Res. 2010 May;263(1-2):33-7
references.pmid: 19818840
references.citation: J Anat. 2011 Jan;218(1):75-86
references.pmid: 20584094
references.citation: J Biomech Eng. 2012 Jan;134(1):011005
references.pmid: 22482660
references.citation: J Biomech. 2010 May 28;43(8):1603-11
references.pmid: 20176361