Exploration of unique porous bone materials for candidacy in bioinspired material design
Date
2018
Authors
Seek, Timothy W., author
Donahue, Seth, advisor
Bradley, Thomas, committee member
Florant, Gregory, committee member
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Abstract
Bioinspired material design draws inspiration for improved technologies from unique functional adaptations found in nature. Grizzly bear (Ursus arctos horribilis), cave bear (Ursus spelaeus), edmontosaur (Edmontosaurus annectens) (Edmontosaurusregalis), and bighorn sheep (Ovis canadensis) exhibit unique functional examples of porous bone structures. Grizzly bear trabecular bone does not lose bone density during long periods of disuse. Cave bears, being larger than grizzly bears, give a unique perspective of trabecular bone property scaling relationships in animals from the near past. Edmontosaurs were expected to have grown to gigantic sizes weighing 7936±1991 kg creating a unique high force loading environment in dinosaur trabecular bone. Bighorn sheep butt heads during the mating season routinely generating near 100g accelerations and approximately 3400N forces in their horn core bone during impact. Morphological trabecular bone properties of bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and trabecular number (Tb.N) were examined using micro-computed tomography (µCT) imaging for the underlying trabecular bone in the proximal tibias of grizzly bear, cave bear, and edmontosaurus animals. Morphological bone properties were compared against body mass scaling relationships from extant mammals. Cave bear trabecular bone was found to have larger BV/TV and Tb.Th than modern grizzly bears. The larger BV/TV may indicate environmental drivers on cave bear trabecular bone properties. To our knowledge, the measurement of dinosaur trabecular bone properties is a novel concept. Adult edmontosaur BV/TV was measured at an average greater than 60% which was significantly different from extant species BV/TV values. Additionally, adult edmontosaurus Tb.Th, and Tb.Sp were measured at comparable values to small mammals. The difference in edmontosaur BV/TV from extant mammals may be a potential clue in why extant terrestrial animals do not reach the same levels of gigantism as dinosaurs. Additionally, mimicking the continuum properties of edmontosaur trabecular bone in an engineered foam may have potential usage in optimized high strength foams. Bighorn sheep horn core bone exhibits observational and morphological properties different from typical trabecular bone in thickness, separation and number. Due to these differences, the bighorn sheep horn core bone is being considered as a new type of porous bone architecture referred to as 'velar' bone. The velar bone morphology indicates that it is highly adapted to resist high impact bending through widely separated and thick bone formations. Future bioinspired engineering foam designs mimicking the structures of porous bone outlined in this research could be useful for energy absorption in repeated high impact loading. The work presented here does not include efforts to create a bioinspired structural foam. However, this research focuses on the quantification of porous bone structural properties optimized for unique mechanical environments for the purposes of guiding future research towards structural foam design.
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Subject
morphology
trabecular bone
bioinspired
Wolff's Law
structural foams