Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths

M. Taffetani, R. Gottardi, D. Gastaldi, R. Raiteri, P. Vena*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Citations (Scopus)

Abstract

Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests. To this purpose, multiload creep tests using spherical indenters have been carried out on saturated samples of mature bovine articular cartilage achieving two main quantitative results. First, the dependence of indentation modulus in the drained state (at equilibrium) on the tip radius: a value of 500kPa has been found using the large tip (400μm radius) and of 1.7MPa using the smaller one (25μm). Secon, the permeability at microscopic scale was estimated at values ranging from 4.5×10-16m4/Ns to 0.1×10-16m4/Ns, from low to high equivalent deformation. Consistently with a poroelastic behavior, the size-dependent response of the indenter displacement disappears when characteristic size and permeability are accounted for. For comparison purposes, the same protocol was applied to intrinsically viscoelastic homogeneous samples of polydimethylsiloxane (PDMS): both indentation modulus and time response have been found size-independent.

Original languageEnglish
Pages (from-to)850-858
Number of pages9
JournalMedical Engineering and Physics
Volume36
Issue number7
DOIs
Publication statusPublished - Jul 2014

Bibliographical note

Funding Information:
Italian Ministry of University and Research , through the PRoject of National Interests program ( PRIN2008 ), RiMED Foundation fellowship for RG.

Keywords

  • Articular cartilage
  • Nanoindentation
  • Poroelasticity size effect
  • Time-dependence

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