1 Novel Experiments and Models for the Nanomechanics of Polymeric and

• Main Authors: Biological Nanofibers, Ioannis Chasiotisa, Leonid Zhigileib, Roberto Ballarinic, Elias Aifantisd
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Cucumaria frondosa
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.596.8078; http://www.nseresearch.org/2005/NewFiles/ov17_0403876Virginia_Chasiotis.pdf

The mechanical response of biological materials reflects deformation mechanisms occurring within a hierarchical architecture extending over several length scales. This research program aims at filling the void in quantitative experimental/computational mechanics of soft nanofibers in the range of 10-200 nm that will help to predict and mitigate bone fracture, design improved synthetic bone replacements, ligaments and tendons, and lay the ground work for bioinspired and hierarchically structured multifunctional composite materials. Figure 1. Collagen nanofibril loaded in tension by a MEMS mechanical testing platform [1]. Figure 2. Stress-strain curve of a collagen nanofibril showing decreasing stiffness upon cyclic loading [1]. A microelectromechanical (MEM) platform for mechanical property measurements was designed and fabricated to obtain the first stress-strain (σ-ε) curves of type I collagen nanofibrils isolated from the sea cucumber Cucumaria frondosa [1], as seen in Figure 1. Sea cucumber fibrils are similar to those found in vertebrates having the same length, assembled with the same repeat period, possessing the same gap/overlap ratio and the same cross-linking chemistry. The challenge to manipulate isolated collagen nanofibrils onto the MEMS test platform was overcome by labeling the nanofibrils with fluorescently tagged antibodies. This procedure provided punctate staining concomitantly allowing for measuring the strain distribution along the fibril. The elastic moduli at small and large strains were estimated by converting the load-displacement data to true stress- logarithmic strain. At low strains, the nanofibrils displayed tangent moduli in the range 0.26-0.30 GPa. The true stress-logarithmic strain curves suggest a 2 µm