Journal of Biomechanics 39 (2006) 1677–1685 An extended modeling of the micropipette aspiration experiment for the characterization of the Young’s modulus and Poisson’s ratio of adherent thin biological samples: Numerical and experimental studies Thomas Boudou a , Jacques Ohayon a,Ã , Youri Arntz b , Ge´rard Finet c , Catherine Picart b , Philippe Tracqui a a Laboratoire TIMC-IMAG, Equipe DynaCell, CNRS UMR 5525, Institut de l’Inge´nierie et de l’Information de Sante´, Faculte´de Me´decine de Grenoble, 38706 La Tronche Cedex, France b Institut National de la Sante´et de la Recherche Me´dicale, Unite´595, Faculte´de Chirurgie Dentaire, Universite´Louis Pasteur, 11 rue Humann, 67085 Strasbourg Cedex, France c CREATIS—CNRS, UMR 5515 affiliated to INSERM, Departement of Hemodynamics and Interventional Cardiology, Hopital Cardiologique, BP Lyon-Montchat, 69394 Lyon Cedex 03, France Accepted 28 April 2005 Abstract The micropipette aspiration (MA) experiment remains a quite widely used micromanipulation technique for quantifying the elastic modulus of cells and, less frequently, of other biological samples. However, moduli estimations derived from MA experiments are only valid if the probed sample is non-adherent to the rigid substrate. This study extends this standard formulation by taking into account the influence of the sample adhesion. Using a finite element analysis of the sample aspiration into the micropipette, we derived a new expression of the aspirated length for linear elastic materials. Our results establish that (i) below a critical value, the thickness h of the probed sample must be considered to get an accurate value of its Young’s modulus (ii) this critical value depends both on the Poisson’s ratio and on the sample adhesivity. Additionally, we propose a novel method which allows the computation of the intrinsic Young’s modulus of the adherent probed sample from its measured apparent elasticity modulus. Thanks to the set of computational graphs we derived from our theoretical analysis, we successfully validate this method by experiments performed on polyacrylamide gels. Interestingly, the original procedure we proposed allows a simultaneous quantification of the Young’s modulus and of the Poisson’s ratio of the adherent gel. Thus, our revisited analysis of MA experiments extends the application domain of this technique, while contributing to decrease the dispersion of elastic modulus values obtained by this method. r 2005 Elsevier Ltd. All rights reserved. Keywords: Soft tissue; Finite element analysis; Mechanical properties; Mechanical model 1. Introduction Several experimental micromanipulation techniques have been proposed for characterizing the mechanical properties of thin biological samples as well as micro- films of polymers, extending from the simple micropip- ette aspiration (MA) method (Alexopoulos et al., 2003, 2005; Aoki et al., 1997; Engstro¨ m and Meiselman, 1996; Guilak et al., 2000; Heinrich and Rawicz, 2005; Hochmuth, 2000; Matsumoto et al., 2002; Nava et al., 2004; Ohashi et al., 1995; Sato et al., 1987, 1989; Thoumine et al., 1999; Trickey et al., 2005), to more recent techniques such as magnetic twisting cytometry (MTC) (Ohayon et al., 2004; Wang et al., 1993) or atomic force microscopy (AFM) (Charras et al., 2001; Charras and Horton, 2002; Dimitriadis et al., 2002; ARTICLE IN PRESS www.elsevier.com/locate/jbiomech www.JBiomech.com 0021-9290/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jbiomech.2005.04.026 Ã Corresponding author. Tel.: +33 456 52 01 24; fax: +33 456 52 00 22 E-mail address: Jacques.Ohayon@imag.fr (J. Ohayon).