Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session C49: Biomaterials 3: Structure, Function, DesignFocus
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Sponsoring Units: DBIO DCP Chair: Debora Frigi Rodrigues, University of Houston Room: LACC 511A |
Monday, March 5, 2018 2:30PM - 2:42PM |
C49.00001: Apatite X-ray linear dichroism reveals mesoscale crystal orientations in parrotfish bone and teeth Cayla Stifler, Chang-Yu Sun, Matthew Marcus, Michel Sassi, Kevin Rosso, Pupa Gilbert Apatites are an important biomineral, being a major component of bone, dentin, enamel, and enameloid in a variety of organisms. Yet, the use of x-ray linear dichroism in the study of these minerals remains largely unexplored. We observed x-ray linear dichroism at the Calcium L and K edge in geologic hydroxyapatite (Ca5(PO4)3OH), fluorapatite (Ca5(PO4)3F), and their biogenic counterparts in parrotfish bone, dentin, and enameloid. Furthermore, we explain this phenomenon with detailed models of the apatite crystal and calculated spectra, in excellent agreement with experimental spectra1. This discovery enables visualization of the nano- to micro-scale structure of apatite crystals in human teeth and bone using Polarization-dependent Imaging Contrast (PIC) maps2. Illustrative new PIC maps of parrotfish enameloid show a most complex arrangement of fluorapatite crystals, bundled and interwoven3, which makes parrotfish enameloid uniquely capable of biting stony corals. |
Monday, March 5, 2018 2:42PM - 2:54PM |
C49.00002: Mesoscale structure of human and mouse enamel Pupa Gilbert, Elia Beniash, Cayla Stifler, Chang-Yu Sun, Hajime Yamazaki, Henry Margolis We recently discovered that apatite exhibit X-ray linear dichroism [1,2] at the Ca L-edge, an effect that enables Polarization-dependent Imaging Contrast (PIC) mapping [3,4] of apatite, to quantitatively measure and display nanocrystal orientations. Here we present PIC maps revealing unexpected and unprecedented observations in the structure and orientation of crystals in human and mouse dental enamels, at the mesoscale, that is, between 10 nm and 10 µm. |
Monday, March 5, 2018 2:54PM - 3:06PM |
C49.00003: Parrotfish Teeth: Stiff Biominerals Whose Microstructure Makes Them Tough and Abrasion-Resistant to Bite Stony Corals Matthew Marcus, Shahrouz Amini, Cayla Stifler, Chang-Yu Sun, Nobumichi Tamura, Hans Bechtel, Dilworth Parkinson, Harold barnard, Xiyue Zhang, Ali Miserez, J. Q. Isaiah Chua, Pupa Gilbert Parrotfish feed by biting stony corals. To investigate how their teeth endure such contact stress, we examine the composition, nano/micro- structure, and mechanical properties of the steephead parrotfish Chlorurus microrhinos tooth. Its enameloid is a fluorapatite biomineral with outstanding mechanical properties: the mean elastic modulus and hardness near the biting surface: 124 GPa and 7.3 GPa, resp., making it among the stiffest and hardest biominerals known; mean indentation yield strength is >6 GPa, and mean fracture toughness is 2.5 MPa.m1/2. This combination of properties yields high abrasion resistance. Fluorapatite shows X-ray linear dichroism at the Ca L-edge, enabling polarization-dependent contrast mapping1-2 of apatite, to quantitatively measure nanocrystal orientations. Parrotfish enameloid consists of 100-nm-wide, microns-long crystals, co-oriented and bundled into interwoven fibersm which decrease in average diameter from 5 µm at the back to 2 µm at the tooth tip. This size change is spatially correlated with an increase in hardness.3 |
Monday, March 5, 2018 3:06PM - 3:42PM |
C49.00004: Bone hierarchical structure and mechanics through 3D X-ray imaging techniques Invited Speaker: Henrik Birkedal Bone is an anisotropic hierarchical composite material that is special amongst biominerals in that it contains living cells called osteocytes that acts as sensors of damage. The multi-length-scale structures of bone remain far from understood. We have harnessed recent developments in X-ray imaging including X-ray nanotomography and X-ray multimodal imaging to shed new light on bone structure and mechanics. |
Monday, March 5, 2018 3:42PM - 3:54PM |
C49.00005: Characterization of Fracture Resistance and Robustness in Network-Based Models of Bone Avik Mondal, Chantal Nguyen, Xiao Ma, Ahmed Elbanna, Jean Carlson
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Monday, March 5, 2018 3:54PM - 4:06PM |
C49.00006: Spider Silk Fibers Solely Composed out of 20-nm Thin Fibrils Qijue Wang, Hannes Schniepp The origin of spider silk’s outstanding mechanical properties, combining high strength and high extensibility, has been intensively studied for decades. Its hierarchical structure has been recognized to play a significant role. Due to the lack of unambiguous experimental evidence, competing and incompatible structural models of natural silk fibers have been proposed, some of them including various types of fibrillar components. To fully understand the hierarchical structure of silk, we study the silk of the recluse (Loxosceles) spider. While exhibiting the outstanding mechanical properties of a typical spider silk, Loxosceles silk is not cylindrical, but ribbon-like, with a width of 6–8 μm and a thickness of less than 50 nm, only a few protein layers thin. Our work found that the Loxosceles ribbons are entirely composed of 20-nm thin protein fibrils that are several micrometers long and oriented parallel to the fiber axis. Hence, a single nanofibril embodies all key properties of spider silk. The idea of nanofibrils as the major building blocks suggests a paradigm change in both the investigation and the understanding of structure-property relationships of silk, which will further the state of the art in silk research and silk-inspired high-performance materials. |
Monday, March 5, 2018 4:06PM - 4:18PM |
C49.00007: Effect of Pigment and Microstructure on the Elastic Properties of Anomia ephippium Shells Dhanya Radhakrishnan, Mengjing Wang, Daniel Williams, Kristie Koski Biological evolution has achieved the ultimate optimization of material structure, properties, and performance which can be an inspiration for many biomimetic materials. Most biological materials are hierarchical structures consisting of an inorganic and a small quantity of polymeric component. Several combinations of these materials form the enormous hybrid structures observed in nature. Among the various biological materials, shells are of intense mechanical interest for its remarkable strength and toughness. Anomia ephippium, commonly known as “jingle shells” is nearly optically transparent and exhibit colored hues ranging from white to orange to dark black, which is due to the presence of polyenes. We have studied the full stiffness tensor and elastic properties of A. ephippium as determined using Brillouin scattering, which is a non-invasive tool. Our studies show that the presence of pigments influences the mechanical properties of the shell, which is unusual for an organism exhibiting color polymorphism. We have also studied the influence of microstructure on the elastic properties of the shells by comparing the nacre and prismatic layers of red abalone with the foliated calcite structure of A. ephippium. |
Monday, March 5, 2018 4:18PM - 4:30PM |
C49.00008: Effect of Organic-inorganic Interface in Mechanical Properties of Nacre Sina Askarinejad, Nima Rahbar Enhanced mechanical and fracture properties of biological composites encourage researchers to focus on the problem-solving strategies of these naturally growing materials. Bone and nacre are prime examples of natural composites with high strength, stiffness, and toughness. In addition to nano-scale features, nature has evolved complex and effective functionally graded interfaces. Particularly in nacre, the organic-inorganic interface in which the proteins behave stiffer and stronger in the proximity of minerals provide an impressive role in structural integrity and mechanical deformation of the natural composite. However, further research on the toughening mechanisms and the role of the interface properties is essential. In this study, a micromechanical analysis of the mechanical response of these composites is presented considering interface properties. The well-known shear-lag theory was employed on a simplified two-dimensional unit-cell of the multilayered composite. The results solve the important mysteries about nacre and emphasize the role of organic-inorganic interface properties. |
Monday, March 5, 2018 4:30PM - 4:42PM |
C49.00009: Coral Biomineralization via Amorphous Calcium Carbonate Particle Attachment Christopher Colla, Tali Mass, Anthony Giuffre, Chang-Yu Sun, Cayla Stifler, Matthew Frazier, Maayan Neder, Nobumichi Tamura, Camelia Stan, Matthew Marcus, Pupa Gilbert New evidence suggests corals form their skeletons via particle attachment of amorphous calcium carbonate (ACC) precursors.1 Evidence for this comes from photoemission electron spectromicroscopy (PEEM) and polarization-dependent imaging contrast (PIC)-mapping.1,2 Coral growth was previously thought to occur via ion-by-ion growth.1 Elemental and isotopic ratios show vital effects in corals, indicating ion-by-ion growth is not a suitable mechanism for skeletal growth. Furthermore, ion-by-ion growth is relatively slow compared to ACC particle attachment, which could have physiological advantages.1 The current viewpoint of skeletal growth by particle attachment of amorphous calcium carbonate precursors could shed light on this highly debated topic as well as elucidate a mechanism of biomineralization.1 Thus far this formation mechanism has been demonstrated in only one species, Stylophora pistillata. But is it general? In this talk I will briefly review recent results and discuss future planned experiments to probe how other species of corals form their skeletons. |
Monday, March 5, 2018 4:42PM - 4:54PM |
C49.00010: Different Growth Modes Of Coral Skeletons Revealed By Crystal Orientation Map Chang-Yu Sun, Cayla Stifler, Matthew Marcus, Tali Mass, Stefano Goffredo, Giuseppe Falini, Pupa Gilbert Coral skeletons were assumed based on morphology to grow spherulitically, that is, as radially distributed acicular aragonite (CaCO3) crystals, with their c-axes radiating from points. Recently we showed with Polarization-dependent Imaging Contrast (PIC) maps [1,2] that Stylophora pistillata (Sp) coral skeleton indeed grow spherulitically [3,4]. Is this true for other species? We tested Balanophyllia europaea (Be) and found that Be and Sp differ: Sp has only spherulites, whereas Be has spherulites and randomly oriented equant crystals, we named “sprinkles”. We show here that sprinkles grow slowly, and spherulites grow rapidly, but both grow by particle attachment [6], and are faster than ion-by-ion aragonite growth. We propose that a new class of proteins exists, which we named crystal Growth Rate Influencing Proteins (GRIPs), based on the observation in PIC maps that they make crystals grow faster or slower. |
Monday, March 5, 2018 4:54PM - 5:30PM |
C49.00011: Biomaterials and their isotopes through geologic time Invited Speaker: Kristin Bergmann Calcitic and phosphatic biomaterials provide a critical record of Earth's past ocean and climate conditions. Here we explore the nature of the materials including their structure and isotopic composition. Specifically we consider the secular increase in δ18O values of both calcitic and phosphatic marine fossils through time. This trend suggests either that 1) early Paleozoic surface temperatures were high, in excess of 40°C (tropical MAT), 2) the δ18O value of seawater has increased by 7–8‰ VSMOW through Paleozoic time, or 3) diagenesis has altered secular trends in early Paleozoic samples. Carbonate clumped isotope analysis, in combination with petrographic and elemental analysis, can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular δ18O increase. Clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late Cambrian- to Middle-late Ordovician-aged strata–the first paired fossil study of its kind–document tropical sea surface temperatures near modern temperatures (26-38°C) and seawater oxygen isotope ratios similar to today’s ratios. |
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