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Collagen fibrils, with diameters of the order of 100 nm, are the building blocks of mammalian tissues. Because of their ultra-small dimensions very few studies have been done to date to obtain their time-dependent mechanical properties. We developed in situ mechanical testing methods to obtain real time mechanical measurements on dry and fully hydrated (in vitro conditions) reconstituted mammalian collagen fibrils, Figure (a), with sub-millisecond resolution to obtain the strain rate response of individual fibrils. We showed for the first time the strain rate sensitivity of the properties of collagen fibrils resulting in outstanding mechanical behavior: Increasing strain rate increases the mechanical strength but does not compromise the ductility, Figure (b) allowing for engineering strains that exceed 40%! Using the same experimental methodologies we have shown for the first time that individual collagen nanofibrils behave as a non-linear viscoelastic material that does not obey the QLV model.

These behaviors hold for both fully hydrated and partially hydrated collagen fibrils. Interestingly, partially hydrated fibrils demonstrate the same ductility as those tested in PBS but reach tensile strengths that exceed the strength of common steels, Figure (c)! The publications below provide the details of these studies.

(c)

                                                                                                  Related Publications

1. F. Yang, D. Das, K. Karunakaran, S. Thomopoulos, G.M. Genin and I. Chasiotis, “In vitro Time Dependent Mechanical Behavior of Reconstituted Mammalian Collagen Fibrils”, Acta Biomaterialia, 163, pp. 63-77, (2023).

2. F. Yang, D. Das and I. Chasiotis, “Effect of Strain Rate on Mechanical Behavior of Collagen Fibrils”, Applied Physics Letters 120, p. 114101 (2022).

3. F. Yang, D. Das and I. Chasiotis, “Microscale Creep and Stress Relaxation Experiments with Individual Collagen Fibrils”, Optics and Lasers in Engineering 150, pp. 106869, (2022).

4. J. Liu, D. Das, Y. Fan, A. Schwartz, S. Thomopoulos, G.M. Genin, I. Chasiotis, “Energy Dissipation in Mammalian Collagen Fibrils: Cyclic Strain-induced Damping, Toughening, and Strengthening”, Acta Biomaterialia 80, pp. 217–227, (2018).

5. P. V. Kolluru, J. Lipner, L. Wenying, Y. Xia, S. Thomopoulos, G.M. Genin and I. Chasiotis, “Strong and Tough Mineralized PLGA Nanofibers for Tendon-to-bone Scaffolds”, Acta Biomaterialia 9, pp. 9442–9450, (2013).