Biological Materials Science: Biological Materials Science III
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Biomaterials Committee
Program Organizers: David Restrepo, University of Texas at San Antonio; Steven Naleway, University of Utah; Jing Du, Pennsylvania State University; Ning Zhang, Baylor University
Thursday 8:30 AM
March 18, 2021
Room: RM 12
Location: TMS2021 Virtual
Session Chair: Santiago Orrego, Temple University; Alexander Ossa, Universidad EAFIT
8:30 AM Invited
Microstructural Variations in Mammalian Enamel: An Exploration of Decussation from the Micro- to the Macro-scale: Cameron Renteria1; Juliana Fernández-Arteaga2; Alexander Ossa2; Dwayne Arola1; 1University of Washington; 2Universidad EAFIT
Enamel serves as the outermost tissue of mammalian teeth and must endure millions of masticatory cycles over an animal’s lifetime. Most mammals are diphyodonts and possess acellular enamel, which is incapable of repair by cellular regeneration. Damage tolerance of this tissue is essential to resist tooth failure and is primarily achieved by decussation, a meso-scale structural feature involving complex weaving of the enamel rods over their course from the tooth surface to the dentin-enamel junction (DEJ). The decussation pattern controls the path of crack extension by guiding cracks to regions where they can be arrested. While the decussation patterns of tooth enamel from different animal clades are unique, relatively limited work has been performed to characterize this unique aspect of microstructure. This study explores the variations in decussation patterns of tooth enamel across six mammals in an attempt to identify key aspects of enamel that can serve as bioinspiration.
9:00 AM
On the Structure and Mechanical Properties of Aprismatic Enamel in Crocodilian Teeth: Jack Grimm1; Cameron Renteria1; Savannah Camacho1; Xitlalit Sanchez-Martinez1; Dwayne Arola1; 1University of Washington
The enamel of mammalian teeth is a remarkable biological material that is renowned for its ability to resist fracture over millions of masticatory cycles over the animal’s lifetime. This excellent performance arises from the complex hierarchical structure, which involves the hydroxyapatite (HA) nanocrystals (~50nm diameter), their assembly into rods (~5μm), and their decussating structure. Reptilian enamel, particularly that of crocodilians, is ‘aprismatic,’ meaning that it consists of nanocrystalline HA without the complimentary higher levels of hierarchy. The structure of reptilian enamel provides a means for understanding the importance of one isolated level of hierarchy on toughness, and additional inspiration for the design of synthetic materials. The present effort is focused on understanding the mechanical properties of crocodilian enamel through nanoindentation, nanoscratch, indentation fracture toughness, and in-situ microcantilevers milled by focused ion beam (FIB). A comparison of the properties is made with those of human enamel at the same hierarchical level.
9:20 AM
Tough Enlightenments From the Prayer Bead: Fracture-tolerant Endocarp of Elaeocarpus Ganitrus Seed (Rudraksha): Ashish Ghimire1; Po-Yu Chen1; 1National Tsing Hua University
Seed and nut shells, also called endocarp show remarkable hardness and toughness. Grown in the foothills of Himalayas, Nepal, the Elaeocarpus ganitrus seed is locally known as an unbreakable seed and is widely used for religious purposes. Here, we present the microstructural observations and mechanical performance of previously unexplored and inconspicuous seed endocarp of Elaeocarpus ganitrus. The endocarp exhibits high fracture strength with mean and maximum fracture forces of 3777± 651N and 5023N respectively. Suture interface includes layers of sclereid cells, longitudinally, and randomly oriented fiber bundles that contribute to extreme fracture tolerance. The outer region consists of thick lignified sclereid cells and is harder than the inner region with polygonal, elongated sclerenchyma fiber cells. The layered cellular microstructure promotes a torturous intercellular crack path often deflected upon reaching elongated cells and entangled fiber bundles. This structure-mechanism-property relation provides critical insights and inspiration for developing high fracture-resistant materials.
9:40 AM Invited
Bioinspired Graphene Nanocomposites with Exceptionally High Mechanical Performance: Xiaodong Li1; 1University of Virginia
Nacre (mother of pearl), commonly referred to as nature’s armor, has served as a blueprint for engineering stronger and tougher bioinspired materials. Nature organizes a brick-and-mortar-like architecture in nacre, with hard bricks of aragonite sandwiched with soft biopolymer layers. Graphene is a game changing material. We cloned nacre’s hierarchical architecture and reinforcing mechanisms in engineered materials by simply shear mixing, freeze drying, and sintering of metal powders and graphene sheets. Such man-made nacre-like graphene/metal composites achieved an exceptional enhancement in both strength and toughness. Additionally, we demonstrate that a small amount of graphene can minimize porosity/defects and reinforce carbon fibers. The 0.075 weight % graphene-reinforced carbon fiber exhibits 225% increase in strength and 184% enhancement in Young’s modulus. Such design strategy and model material system should guide the synthesis of bioinspired materials to achieve exceptionally high mechanical performance.
10:10 AM Invited
Tapes: An Overlooked Biological Material Archetype: Hannes Schniepp1; 1College of William & Mary
Fibers and fibrils are the dominant structural biomaterial archetype in plants and animals and make some of Nature’s strongest and toughest materials. Fibrils are typically embedded into a matrix to form a composite, where fiber/matrix interfacial breakdown is an issue, as is anisotropy of the obtained mechanical properties. Substantial flattening of fibers can significantly increase the surface area and thus alleviate some of these issues by enhancing interfacial bonding. Existence of such materials systems in Nature has largely been overlooked. We have further explored extreme cases of this archetype: tapes. We found that tape/tape bonding exhibits an unexpected behavior that can lead to self-strengthening adhesive bonds, and we have developed an analytical description that fully explains it. Employing this effect, we have further realized matrix-free “composites” with tunable stiffness, strength, and toughness.
10:40 AM Invited
Mechanical Properties of Tough, Mechanochemically Active Hydrogels and Hydrogel-based Composites: Jamie Kruzic1; Yuwan Huang1; Bhakthi Jayathilaka1; Shariful Islam1; Meredith Silberstein2; Kristopher Kilian1; 1University of New South Wales; 2Cornell University
Inspired by how forces in biological tissues guide matrix deposition, we have developed bioinspired hydrogel chemistry where an applied force facilitates molecule immobilization from the surrounding environment. We have demonstrated this concept using poly(ethylene glycol) (PEG) hydrogels that are formed through model force-responsive disulphide linkages where bond scission is able to catalyze reactions with complementary groups (e.g., acryloyl and/or maleimide). Furthermore, recognizing that single network hydrogels suffer from inherent brittleness that make them poor choices for load bearing bioengineering applications, we have incorporated these mechanochemically active networks into tough, double network hydrogels reinforced with alginate to mimic the interpenetrating networks of biomolecules found in living tissue. This presentation will report on the mechanical and functional properties of single and double network mechanochemically active hydrogels and how different network structures and composite architectures control the mechanical properties and mechanochemical response.