0
Research Papers

Mechanical and Microstructural Investigation of the Cyclic Behavior of Human Amnion

[+] Author and Article Information
Michela Perrini

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Department of Obstetrics,
University Hospital Zurich,
Zurich 8091, Switzerland
Institute for Mechanical Systems,
Leonhardstrasse 21,
Zurich 8092, Switzerland
e-mail: perrini@imes.mavt.ethz.ch

Arabella Mauri

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Institute for Mechanical Systems,
Leonhardstrasse 21,
Zurich 8092, Switzerland
e-mail: mauri@imes.mavt.ethz.ch

Alexander Edmund Ehret

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Institute for Mechanical Systems,
Leonhardstrasse 21,
Zurich 8092, Switzerland
e-mail: ehret@imes.mavt.ethz.ch

Nicole Ochsenbein-Kölble

Department of Obstetrics,
University Hospital Zurich,
Zurich 8091, Switzerland
Department of Obstetrics,
Frauenklinikstrasse 10,
Zurich 8091, Switzerland
e-mail: nicole.ochsenbein@usz.ch

Roland Zimmermann

Department of Obstetrics,
University Hospital Zurich,
Zurich 8091, Switzerland
Department of Obstetrics,
Frauenklinikstrasse 10,
Zurich 8091, Switzerland
e-mail: roland.zimmermann@usz.ch

Martin Ehrbar

Department of Obstetrics,
University Hospital Zurich,
Zurich 8091, Switzerland
Department of Obstetrics,
Schmelzbergstrasse 12,
Zurich 8091, Switzerland
e-mail: martin.ehrbar@usz.ch

Edoardo Mazza

Department of Mechanical
and Process Engineering,
ETH Zurich,
Zurich 8092, Switzerland
Swiss Federal Laboratories
for Materials Science and Technology,
EMPA,
Dübendorf 8600, Switzerland
Institute for Mechanical Systems,
Leonhardstrasse 21,
Zurich 8092, Switzerland
e-mail: mazza@imes.mavt.ethz.ch

1M. Perrini and A. Mauri contributed equally to this work.

Manuscript received October 20, 2014; final manuscript received March 10, 2015; published online April 15, 2015. Assoc. Editor: Thao (Vicky) Nguyen.

J Biomech Eng 137(6), 061010 (Jun 01, 2015) (10 pages) Paper No: BIO-14-1526; doi: 10.1115/1.4030054 History: Received October 20, 2014; Revised March 10, 2015; Online April 15, 2015

The structural and mechanical integrity of amnion is essential to prevent preterm premature rupture (PPROM) of the fetal membrane. In this study, the mechanical response of human amnion to repeated loading and the microstructural mechanisms determining its behavior were investigated. Inflation and uniaxial cyclic tests were combined with corresponding in situ experiments in a multiphoton microscope (MPM). Fresh unfixed amnion was imaged during loading and changes in thickness and collagen orientation were quantified. Mechanical and in situ experiments revealed differences between the investigated configurations in the deformation and microstructural mechanisms. Repeated inflation induces a significant but reversible volume change and is characterized by high energy dissipation. Under uniaxial tension, volume reduction is associated with low energy, unrecoverable in-plane fiber reorientation.

FIGURES IN THIS ARTICLE
<>
Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

Deformation modes (a), (b), experimental setups (c), (d), and testing protocols (e), (f). (a) Sample geometry and deformation during inflation test (R: radius of curvature, dref: apex displacement at the reference configuration, d: current apex displacement measured with respect to dref); (b) sample geometry and deformation during uniaxial test (lref: length of the specimen at the reference configuration, l: current length measured during stretching, wref: central width of the specimen at the reference configuration, w: current width of the specimen measured during stretching); (c) inflation device in the MPM with inflated amnion (arrow); (d) stretching device in the MPM with amnion sample (arrow); (e) pressure profile applied for cyclic inflation tests and top view of the amnion sample (50 mm diameter). The region of interest where markers are tracked is a circular area with 10 mm diameter in the center of the specimens (scale bar: 10 mm, 0.39 in.); (f) nominal stretch profile applied for cyclic uniaxial tests and top view of the specimen with markers (scale bar: 10 mm, 0.39 in.). Initial: slack sample; ref1: reference configuration corresponding to a reference load of 1 mbar (inflation) and 0.01 N (uniaxial) and defining the beginning of the experiment; ref and max: cycles are applied between the reference load and the maximum load/stretch; end: end of the tenth cycle.

Grahic Jump Location
Fig. 2

Load-deformation curves for inflation (a), (c) and uniaxial (b), (d) experiments. (a) Pressure-apex displacement curves of the first loading cycle; (b) force-nominal stretch curves of the first loading cycle; (c) pressure-displacement curves normalized with respect to the maximum apex displacement reached in the first loading cycle dmax1; (d) force-nominal stretch curves normalized with respect to the maximum force reached in the first loading cycle Fmax1. Gray lines: curves of the seven tested specimens; black lines: mean curves.

Grahic Jump Location
Fig. 3

Mean tension-stretch loading curves (a), (b) and tangent stiffness curves (c), (d) from the first (darkest) to the tenth (lightest) loading cycle for inflation (a), (c) and uniaxial experiments (b), (d)

Grahic Jump Location
Fig. 4

Tension‐stretch curves of the first cycle of representative inflation (a) and uniaxial (b) tests (λbres and λ1res: residual stretches; ED: total energy dissipated during cycle; EL: energy dissipated during loading); (c) normalized residual strains ɛ¯bres and ɛ¯1res (mean ± standard deviation); (d) DER (mean ± standard deviation)

Grahic Jump Location
Fig. 5

Kinematic response of amnion during uniaxial cyclic tests. (a) The lateral contraction λ2 is plotted against the longitudinal stretch λ1 for the initial configuration (mean ± standard deviation), the first (black line), the second (dark gray) and the tenth (light gray) loading cycles (mean curves); (b) evolution of the lateral contraction during cycles (mean ± standard deviation). Values are referred to the reference configuration at the beginning of the first cycle (ref1).

Grahic Jump Location
Fig. 6

Thickness and volume changes during cyclic tests. (a) Representative transversal and sections of amnion (fluorescence of nuclei SHG of collagen, scale bar: 50 μm, 1.9 mils) imaged during in situ experiments in different loading states; (b) stretch in the thickness direction λ3 (mean ± standard deviation); (c) estimated volumetric stretch J (mean). Values are referred to the reference configuration at the beginning of the first cycle (ref1).

Grahic Jump Location
Fig. 7

Collagen orientation. (a) Representative 2D images of the fibroblast layer (fluorescence of nuclei and SHG of collagen, scale bar: 100 μm, 3.9 mils) imaged during in situ experiments in different loading states; (b) normalized collagen orientation index COI¯ (mean ± standard deviation).

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In