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Edoardo (2015) Time-dependent mechanical behavior of human amnion: Macroscopic and microscopic characterization. Acta Biomaterialia, 11 . pp. 314-323. ISSN 1878-7568 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/45411/1/mauri_actabiomaterialia2014_preprint.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the Creative Commons Attribution Non-commercial No Derivatives licence and may be reused according to the conditions of the licence. For more details see: http://creativecommons.org/licenses/by-nc-nd/2.5/ A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractCharacterizing the mechanical response of the human amnion is essential to understand and to eventually prevent premature rupture of fetal membranes. In this study, a large set of macroscopic and microscopic mechanical tests has been carried out on fresh unfixed amnion to gain insight into the time-dependent material response and the underlying mechanisms. Creep and relaxation responses of amnion were characterized in macroscopic uniaxial tension, biaxial tension and inflation configurations. For the first time, these experiments were complemented by microstructural information from nonlinear laser scanning microscopy performed during in-situ uniaxial relaxation tests. The amnion showed large tension reduction during relaxation and small inelastic strain accumulation in creep. The short-term relaxation response was related to a concomitant in-plane and out-of-plane contraction and was dependent on the testing configuration. The microscopic 2 investigation revealed a large volume reduction at the beginning, but no change of volume was measured long-term during relaxation. Tension-strain curves normalized with respect to the maximum strain were highly repeatable in all configurations and allowed the quantification of corresponding characteristic parameters. The present data indicate that dissipative behavior of human amnion is related to two mechanisms: (i) volume reduction due to water outflow (up to ~20 seconds) and (ii) long-term dissipative behavior without macroscopic deformation and no systematic global reorientation of collagen fibers. IntroductionThe fetal membrane (FM) surrounds the growing fetus and ensures its environment during gestation. Preterm premature rupture of the membrane affects about 3% of all pregnancies and increases the risk of morbidity in the newborn [1]. The etiology of preterm premature rupture of the membrane is complex and not completely understood. Repeated mechanical loading, such as that occurring as a result of fetal movement and labor, was recen...