Baaijens, F.P.T.

Bouten, C.V.C.

Cox, M.A.J.

Driessen, N.J.B.

English

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 Mechanical characterization of planar soft biological tissuesCitation for published version (APA):Cox, M. A. J., Driessen, N. J. B., Bouten, C. V. C., & Baaijens, F. P. T. (2006). Mechanical characterization ofplanar soft biological tissues. Poster session presented at Mate Poster Award 2006 : 11th Annual PosterContest.Document status and date:Published: 01/01/2006Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 08. Feb. 2024/mhjMechanical characterization of planar soft biologicaltissuesMartijn A.J. Cox, Niels J.B. Driessen, Carlijn V.C. Bouten, Frank P.T. BaaijensEindhoven University of Technology, Department of Biomedical EngineeringIntroductionCurrent methods for mechanical characterization are insuf-ficient for a full characterization of the typical non-linear,anisotropic and inhomogeneous material behavior of planarsoft biological tissues, such as skin, blood vessels or heartvalve leaflets.ObjectiveDevelopment, validation and application of a method for thenon-destructive, local mechanical characterization of planarsoft biological tissues using spherical indentation.MethodsAn indentation device is mounted on top of an inverted confo-cal microscope (CLSM). The indentation depth and force aremeasured by the indentation device. Digital Image Correla-tion (DIC) is applied to the confocal images to quantify tissuedeformation during indentation (Fig. 1).Figure 1 Indentation device on top of an inverted CLSM (left).Tissue engineered (TE) construct during indentation, first principalstretch directions are indicated with arrows (right).A numerical model is coupled to the experimental results formechanical parameter estimation. The tissue is modeled asan incompressible fiber-reinforced material [1]. The extrastress τ is given by an isotropic matrix stress τm and a fiberstress ψf , which works in the fiber direction ~ef only:τ = τm +Nf∑i=1φif[ψif − ~e if · τm · ~e if]~e if~eif . (1)A Gaussian fiber distribution is modeled by a discrete num-ber of fibersNf with a volume fraction of φif each.ResultsA computational study showed that one single indentationtest provides sufficient information to characterize the local,nonlinear, anisotropic behavior of soft biological tissues [2].Indentation depth and force alone suffice for characterizationof the isotropic behavior. Experimental validation was per-formed on linear elastic PDMS rubbers and identical resultswere found for indentation and uniaxial tensile tests.Mechanical characterization was performed of epiderm andbioartificial muscle (BAM), (Fig. 2). The experimental datawas fit well by a nonlinear Neo-Hookean model. Results indi-cated that BAM’s seeded with cells were significantly stifferandmore nonlinear than without cells after 4 weeks of cultur-ing.Figure 2 Numerical fit of an indentation test on epiderm (left) andBAM (right) using a nonlinear Neo-Hookean material model.Indentation tests revealed inhomogeneous mechanical be-havior for tissue engineered heart valve (TEHV) leaflets after 4weeks of culturing. Different behavior was found for the belly(center) and the commissure (edge) of TEHV leaflets (Fig. 3).Figure 3 Indentation test (left) on the belly (red) and commissure(green) of a TEHV leaflet (right) after 4 weeks of culture time.Future workFor the estimation of anisotropic mechanical properties, aquantitative agreement needs to be found between deforma-tion gradients during indentation from experiments and sim-ulations. Preliminary findings on TE constructs indicate a rea-sonable qualitative agreement (Fig. 4). Parameter estimationwill be performed to achieve a quantitative fit.−0.2 −0.1 0 0.1 0.2−0.2−0.100.10.20.3x [mm]y [mm]1.181.21.221.24−0.2 0 0.2−0.2−0.100.10.20.3x [mm]y [mm]1.31.321.341.36Figure 4Magnitude and direction of first principal stretch at 20%indentation of a TE construct: experiment (left) and simulation(right).References:[1] DRIESSEN NJB, ET AL. : JBME, 127(3), 2005[2] COX MAJ, ET AL.: JBME, 128(3), 2006

Mechanical characterization of planar soft biological tissues

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Mechanical characterization of planar soft biological tissues

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