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Tensile Mechanical Properties of Isolated Collagen Fibrils Obtained by Microelectromechanical Systems Technology

Shen, Zhilei Liu
http://rave.ohiolink.edu/etdc/view?acc_num=case1278977802

Abstract Details

2010, Doctor of Philosophy, Case Western Reserve University, Biomedical Engineering.
Collagenous tissues (e.g. bone and tendon) have well organized hierarchical structures. To improve understanding of the mechanical behavior of collagenous tissues and to guide the development of multiscale models, mechanical testing at different length scales is required. Whole tissues, fascicles, and fibril bundles have been studied extensively, but little is known at the fibrillar level. Using microelectromechanical systems (MEMS) technology, tensile mechanical testing was performed on type I collagen fibril specimens isolated from the dermis of sea cucumbers. In air uniaxial tensile tests showed that the fibrils had a small strain elastic modulus of 860 ± 450 MPa, a yield stress of 220 ± 140 MPa, and a yield strain of 21% ± 13%. In vitro fracture tests showed that the fibrils had an elastic modulus of 470 ± 410 MPa, a fracture strength of 230 ± 160 MPa, and a fracture strain of 80% ± 44%. The fibrils displayed significantly lower elastic modulus in vitro than in air. Both the fracture strength/strain obtained in vitro and in air were significantly larger than those obtained in vacuo, indicating that the difference arises from the lack of intrafibrillar water molecules produced by vacuum drying. Fracture strength/strain of fibril specimens were different from those reported for collagenous structures of higher hierarchical levels, indicating the importance of obtaining these properties at the fibrillar level for multiscale modeling. In vitro coupled creep and stress relaxation tests demonstrated the intrinsic viscoelastic behavior of collagen fibrils. The stress-strain-time data were fitted using a Kelvin model consisting of a spring and a dashpot in parallel. The fibrils showed an elastic modulus of 180 ± 100 MPa, a viscosity of 4.7 ± 3.2 GPa*sec, and a relaxation time of 29 ± 16 sec. The fibrillar relaxation time was smaller than the tissue-level relaxation time, suggesting tissue relaxation is dominated by non-collagenous components (e.g. proteoglycans). To our knowledge, in vitro fracture and viscoelastic properties of isolated collagen fibrils were measured for the first time. The mechanical properties obtained in this work can be used as input parameters for multiscale modeling and help guide the development of synthetic biomaterials.
Steven J. Eppell, PhD (Committee Chair)
Roberto Ballarini, PhD (Committee Co-Chair)
Eben Alsberg, PhD (Committee Member)
Vincent C. Hascall, PhD (Committee Member)
Harold Kahn, PhD (Committee Member)
255 p.
Biomedical Research; Engineering; Mechanical Engineering
collagen; fibrils; biomechanics; mechanical properties; elastic modulus; fracture; strength; viscoelasticity; MEMS; microelectromechanical systems

Recommended Citations

Citations

  • Shen, Z. L. (2010). Tensile Mechanical Properties of Isolated Collagen Fibrils Obtained by Microelectromechanical Systems Technology [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1278977802

    APA Style (7th edition)

  • Shen, Zhilei. Tensile Mechanical Properties of Isolated Collagen Fibrils Obtained by Microelectromechanical Systems Technology. 2010. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1278977802.

    MLA Style (8th edition)

  • Shen, Zhilei. "Tensile Mechanical Properties of Isolated Collagen Fibrils Obtained by Microelectromechanical Systems Technology." Doctoral dissertation, Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278977802

    Chicago Manual of Style (17th edition)

case1278977802
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© 2010, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.