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Research Papers

Characterization of Mechanical Properties of Tissue Scaffolds by Phase Contrast Imaging and Finite Element Modeling

[+] Author and Article Information
Nahshon K. Bawolin

Department of Mechanical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: nkb845@mail.usask.ca

Allan T. Dolovich

Department of Mechanical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: allan.dolovich@usask.ca

Daniel X. B. Chen

Mem. ASME
Department of Mechanical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: xbc719@mail.usask.ca

Chris W. J. Zhang

Mem. ASME
Department of Mechanical Engineering,
University of Saskatchewan,
57 Campus Drive,
Saskatoon, SK S7N 5A9, Canada
e-mail: chris.zhang@usask.ca

1Corresponding author.

Manuscript received October 27, 2014; final manuscript received April 14, 2015; published online June 9, 2015. Assoc. Editor: Guy M. Genin.

J Biomech Eng 137(8), 081004 (Aug 01, 2015) (8 pages) Paper No: BIO-14-1535; doi: 10.1115/1.4030409 History: Received October 27, 2014; Revised April 14, 2015; Online June 09, 2015

In tissue engineering, the cell and scaffold approach has shown promise as a treatment to regenerate diseased and/or damaged tissue. In this treatment, an artificial construct (scaffold) is seeded with cells, which organize and proliferate into new tissue. The scaffold itself biodegrades with time, leaving behind only newly formed tissue. The degradation qualities of the scaffold are critical during the treatment period, since the change in the mechanical properties of the scaffold with time can influence cell behavior. To observe in time the scaffold's mechanical properties, a straightforward method is to deform the scaffold and then characterize scaffold deflection accordingly. However, experimentally observing the scaffold deflection is challenging. This paper presents a novel study on characterization of mechanical properties of scaffolds by phase contrast imaging and finite element modeling, which specifically includes scaffold fabrication, scaffold imaging, image analysis, and finite elements (FEs) modeling of the scaffold mechanical properties. The innovation of the work rests on the use of in-line phase contrast X-ray imaging at 20 KeV to characterize tissue scaffold deformation caused by ultrasound radiation forces and the use of the Fourier transform to identify movement. Once deformation has been determined experimentally, it is then compared with the predictions given by the forward solution of a finite element model. A consideration of the number of separate loading conditions necessary to uniquely identify the material properties of transversely isotropic and fully orthotropic scaffolds is also presented, along with the use of an FE as a form of regularization.

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Figures

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Fig. 1

(a) PDMS scaffolds employed for ultrasonic radiation force bending and imaging, (b) PDMS scaffolds employed for compressive testing, and (c) coordinate system

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Fig. 2

Finite element model geometry and exaggerated scaffold deflection under ultrasonic loading

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Fig. 3

Beamline arrangements for (a) DEI [17] and (b) PIC [18]

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Fig. 4

Subtraction of image with and without ultrasound radiation force to reveal scaffold displacement in the direction of the ultrasound beam

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Fig. 5

Gray scale intensity value along horizontal line in planar image of scaffold with periodic microstructure

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Fig. 6

Magnitude component Fourier transform of intensity signal

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Fig. 7

Average compressive stress–strain curve for PDMS scaffold in both the x-direction and the z-direction

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