Joanna McKittrick, University of California, San Diego
Eduard Arzt, INM - Leibniz-Institut für Neue Materialien
David Kisailus, University of California, Riverside
Yurong Ma, Peking University
SM9.1: Natural Materials I
Tuesday PM, March 29, 2016
PCC North, 200 Level, Room 229 B
2:30 PM - *SM9.1.01
Mechanical Investigation of Growing Twisting Cracks in Naturally-Occurring Bouligand Structures
Nobphadon Suksangpanya 1,Michael Jones 1,Nicolas Guarin 1,Nicholas Yaraghi 2,Steven Herrera 2,David Kisailus 2,Pablo Zavattieri 1
1 Purdue Univ West Lafayette United States,2 University of California Riverside Riverside United StatesShow Abstract
Most biological composite materials achieve higher toughness without sacrificing stiffness and strength. Interrogating how Nature employs these strategies and decoding the structure-function relationship of these materials is a challenging task that requires knowledge about the actual loading and environmental conditions of the material in their natural habitat, as well as a complete characterization of their constituents and hierarchical ultrastructure through the use of modern tools such as in-situ electron microscopy, small-scale mechanical testing capabilities, additive manufacturing, and advanced multiscale numerical models. In turn, this provides the necessary tools for the design and fabrication of biomimetic materials with remarkable properties. I will particularly focus my talk on the smashing stomatopod, Odontodactylus scyllarus. This species has been known for its heavily smashing blow creating the velocity and acceleration equivalent to a .22 caliber bullet with the forces up to 1.5 kilonewtons and the load-bearing part of its raptorial appendages, so-called dactyl club, having a capability of withstanding such tremendous forces. The focus of this research is on its extraordinary damage tolerant dactyl club. The dactyl club is mainly characterized by mineralized fiber layers resembled as a helicoidal arrangement, so-called Bouligand structure. The biomimetic helicoidal composite has shown great improvement in through-thickness damage resistance. In this study, a combined computational and experimental approach is carried out to investigate the structure-function relationship of the helicoidal composite based on fracture mechanics. In the experimental part, we 3D print prototypes of helicoidal composite for three-point bending experiments in which the toughening behavior is observed during fracture. The crack is found to propagate through the matrix of helicoidal arrangement and results in the twisted pattern. The crack propagation and toughening mechanism is further examined using analytical and numerical models. Additionally, the twisted crack pattern is investigated based on linear elastic fracture mechanics point of view to explain such toughening mechanism.
3:00 PM - SM9.1.02
Structural and Physical Properties of Nanofiber Silk Produced by Webspinners
Thomas Osborn Popp 2,Bennett Addison 2,Jacob Jordan 2,Warner Weber 2,Janice Edgerly-Rooks 4,Jeffery Yarger 2
1 University of California Berkeley Berkeley United States,2 Arizona State University Tempe United States,3 University of California Davis Davis United States,2 Arizona State University Tempe United States2 Arizona State University Tempe United States4 Santa Clara University Santa Clara United StatesShow Abstract
Insects of the order Embioptera, known as embiids or webspinners, spin sheets of very thin silk fibers from their forelimbs to build silken shelters in leaf litter, underground, or on bark where the climate is warm and humid. Their silk shelters are lightweight but tough and strong to keep out predators, and also hydrophobic to keep out rain. We have studied the molecular level structural properties of the silk material produced by the tropical embiid Antipaluria urichi using solid state nuclear magnetic resonance (NMR), wide angle X-ray diffraction (WAXD) and Fourier-transform infrared spectroscopy (FT-IR). These techniques have shown that the embiid silk protein secondary structure is dominated by β-sheet crystalline domains interspersed in a random coil matrix, similar to spider and silkworm silk fibers. Embiid silk differs from other silks in that approximately 70% of the silk material is comprised of β-sheet crystallites formed by serine-rich repetitive regions that are well-aligned with respect to the fiber axis. Embiid silk shows the highest crystalline fraction yet reported for any silk material. Using scanning and transmission electron microscopy, we have characterized the silk at the nanoscale, showing that the fibers are 90-100 nm in diameter—the thinnest diameter observed for silk produced by any arthropod. Using the aforementioned techniques, we have observed that each silk fiber is coated in an outer layer of lipid material, which gas-chromatography mass spectrometry (GC-MS) revealed to be comprised of fatty acids and other long chain alkane molecules. To investigate the hydrophobic properties of the silk, we performed contact angle studies for water on the silk surface. With an advancing contact angle of 150.0 ± 0.1° and an average hysteresis of 114°, the silk exhibits a property known as the rose petal effect, where water beads up on a hydrophobic surface but adheres to the surface due to nanoscale hierarchical roughness. We believe the results from our research into the structural and physical properties of this previously unstudied silk material will inspire the design of new lightweight, strong, and hydrophobic materials.
3:15 PM - SM9.1.03
A Model of Interfacial Permeability for Soft Seals in Marine-Organism, Suction-Based Adhesion
Michael Beckert 1,Brooke Flammang 2,Jason Nadler 1
1 Advanced Concepts Laboratory Georgia Tech Research Institute Atlanta United States,2 Biological Sciences New Jersey Institute of Technology Newark United StatesShow Abstract
Reversible, suction based adhesion employed by many marine organisms may provide unique, adaptable technologies for biologically inspired grasping devices that function in difficult submerged environments. Remora, lumpsuckers, clingfishes, and octopi are notable organisms capable of forming temporary robust seals against their host using only their soft tissues to create a region of sub-ambient pressure that facilitates attachment. In the past, many studies have focused only on the adhesive strength and neglected other measures of attachment performance such as the seal leakage rate which is critical for understanding prolonged attachment. Here a theoretical framework based on measurable material and topological properties is developed to better understand this critical parameter, and the utility of the approach is demonstrated on an experimental apparatus designed to mimic the flow conditions experienced by a suction-based grasper. Furthermore, the sealing effectiveness of a remora fish on sharkskin is investigated as an example of the model’s application. The model’s success in simulating the flow conditions within the artificial grasper demonstrates its appropriateness as a design tool for translating biological observations to biologically inspired devices.
3:30 PM - SM9.1.04
The Worlds Hardest Teeth: A Look into the Interfacial Strength of a Biologically Synthesized Magnetite Tooth to Soft Body Tissue in Cryptochiton stelleri
Steven Herrera 1,Jeffrey Geiger 1,Chris Salinas 1,Chanhue Jeong 2,Pablo Zavattieri 2,Richard Wuhrer 3,Leigh Sheppard 3,David Kisailus 1
1 Univ of California-Riverside Riverside United States,2 Civil Engineering Purdue University West Lafayette United States3 Advanced Materials Characterization Facility Western Sydney University Parramatta AustraliaShow Abstract
Biological organisms naturally synthesize complex, highly ordered, multi-functional materials that combine structures with drastically different mechanical properties. For instance, the teeth found in the radular belt of the giant chiton, Cryptochiton stelleri, are composed of the world’s hardest biologically produced mineral, yet they are connected to the soft body tissue in the mouth of the chiton by alpha-chitin fibers. The interface between the tooth and the stylus sharply defines each region across only a few microns, and yet this structure is able to repeatedly transfer load to jagged, rocky substrates that harbor chiton sustenance without failure or de-bonding of the two materials. The chiton’s ultra-hard, tricuspid tooth is composed of magnetite rods that are highly aligned parallel to the tooth surface. These rods are templated by alpha-chitin fibers that are also found in the stylus of the tooth. These fibers not only add to the fracture toughness of the tooth, but also increase the interfacial strength between the tooth and stylus by spanning the two regions, effectively stitching them together. By controlling chitin functionalization, the animal can create regions in the base of the stylus that prohibit nucleation of mineral, but can also encourage nucleation in other regions that experience higher stresses and require reinforcement during rasping. Toughening mechanisms at the junction zone will be revealed through the use of microscopic and spectroscopic techniques, and their mechanical properties will be tested with nano-indentation and verified with finite element modeling.
3:45 PM - SM9.1.05
Comparative Analysis of the Woodpecker Skull
Jae-Young Jung 1,Steven Naleway 1,Vincent Sherman 1,Kathryn Kang 2,Nicholas Yaraghi 3,Eric Bushong 4,Mark Ellisman 4,David Kisailus 3,Joanna McKittrick 5
1 Materials Science and Engineering Program UC San Diego La Jolla United States,2 Department of Bioengineering UC San Diego La Jolla United States3 Department of Chemical and Environmental Engineering UC Riverside Riverside United States4 National Center for Microscopy and Imaging Research and Department of Neurosciences UC San Diego La Jolla United States1 Materials Science and Engineering Program UC San Diego La Jolla United States,5 Department of Mechanical and Aerospace Engineering UC San Diego La Jolla United StatesShow Abstract
Woodpeckers peck at trees up to 20 times per second with speeds of 6-7 m/s all while avoiding brain injury despite undergoing decelerations up to 1200g's. Amongst the adaptations allowing this is a highly functionalized impact-absorption system consisting of the head, beak, tongue and hyoid bone. There have been a few attempts to characterize the effect of the shape and mechanical properties of skull on its anti-shock capability, and even these have focused mainly on finite element analysis and microstructural characterizations. This study aims to examine the anatomical structure, mechanical properties, and compositional constituents of the skull to determine its role in energy absorption and stress dissipation. Four different woodpeckers (Ivory-bellied Woodpecker, Golden-fronted Woodpecker, Whited-headed Woodpecker, and Acorn Woodpecker) were assessed through μ-CT to obtain a 3D model along with a control made up of chicken and turkey skulls. Scanning electron microscopy with energy dispersive X-ray spectroscopy was used to identify the structural and chemical components and nanoindentation was carried out to obtain mechanical properties. Results showed the skull bone from four different woodpeckers are very similar with a smooth and elliptical shape, while chickens and turkeys provided a significantly different structure. This structural difference is proposed to have been evolved to dissipate the stress waves created by pecking. Bioinspired applications will be suggested to prevent traumatic brain injury.
This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
4:30 PM - SM9.1.06
Characterization of the Cephalopod Structural Protein Reflectin
Kyle Naughton 1,Qiyin Lin 1,Long Phan 1,Erica Leung 1,Alon Gorodetsky 1
1 UC Irvine Irvine United States,Show Abstract
Cephalopods are well known for their remarkable camouflage abilities; they can modify their
coloration, texture, pattern, and reflectivity to blend into the surrounding environment. Such
dazzling camouflage abilities are enabled by specialized intracellular structures comprised of
unique structural proteins known as reflectins. However, the nano- and micro-scale organization
of these proteins within such structures remains poorly understood. We have fabricated reflectin-
based films and characterized them via environmental scanning electron microscopy (ESEM),
small-angle x-ray scattering (SAXS), grazing incidence small-angle x-ray scattering (GISAXS),
and grazing incidence wide-angle x-ray scattering (GIWAXS). These experiments allowed us to
formulate a model for the hierarchical organization of self-assembled structures from reflectins.
Our findings hold implications for gaining an improved fundamental understanding of the
mechanisms that cephalopods employ to dynamically control their coloration, as well as for the
development of improved cephalopod-inspired materials.
4:45 PM - SM9.1.07
Lightweight Biological Composites: The Feather Vane and Inspired Designs
Tarah Sullivan 1,Andrei Pissarenko 1,Steven Herrera 2,David Kisailus 2,Vlado Lubarda 1,Marc Meyers 1
1 University of California, San Diego La Jolla United States,2 University of California, Riverside Riverside United StatesShow Abstract
Feathers are lightweight, flexible, strong, and spring-like, facilitating a bird’s ability to fly. Flight feathers possess a tiered hierarchical structure consisting of the rachis (main shaft), barbs (beams that branch from the rachis) and barbules (beams that branch from barbs). Neighboring barbs adhere to each other via the Velcro-like barbule connections to form a “zipped” feather vane. This “zipped” vane traps air to allow for lift, but “unzips” and lets air through when forces become dangerously large. This mechanism allows for failure prevention in the feather. Results from previous experiments show that the adherence of barbs to one another via barbules enables a damage resistant structure due to minimized barb rotation in bending. We examine the mechanism of this adhesion and propose a feather inspired design. The unique structure of the feather has potential for the design and synthesis of new bio-inspired materials and devices. This research is funded by AFOSR MURI (AFOSR-FA9550-15-1-0009).
5:00 PM - SM9.1.08
Structural Features and Toughening Mechanisms of the Stomatopod Dactyl Club Exocuticle
Nicholas Yaraghi 1,Nicolas Guarin 2,Nobphadon Suksangpanya 2,Lessa Grunenfelder 1,Jae-Young Jung 4,Mike Davies 5,Tim Jochum 5,Jon Hiller 6,Mark Betts 6,Edward Principe 6,Joseph Lefebvre 7,Richard Wuhrer 8,Leigh Sheppard 8,Joanna McKittrick 4,Pablo Zavattieri 2,David Kisailus 1
1 Univ of California-Riverside Riverside United States,2 Purdue University West Lafayette United States3 University of Southern California Los Angeles United States,1 Univ of California-Riverside Riverside United States4 University of California, San Diego La Jolla United States5 Micro Materials Ltd Wrexham United Kingdom6 TESCAN Pleasanton United States7 Hysitron, Inc. Minneapolis United States8 Western Sydney University Sydney AustraliaShow Abstract
Stomatopods are a group of aggressive marine crustaceans that have evolved highly specialized raptorial appendages used for feeding and hunting prey. In the smashing variety, such as the species, Odontodactylus scyllarus, the terminal segment (dactyl) takes the form of a bulbous hammer-like club, which is used to smash through the tough exoskeletal structures of mollusks, crustaceans, and other shelled marine organisms with incredible force and speed. The dactyl club can reach speeds up to 23 m/s from rest and impact with up to 1500 N of force, generating tremendous stresses including cavitation at the club surface. The success of the dactyl club’s mechanical response, namely its resistance to catastrophic failure from repeated high-energy impacts, lies in its multi-regional and hierarchical composite architecture. This natural material features a compliant inner layer featuring helicoidal and sheet-like arrangements of alpha-chitin fibrils mineralized by amorphous forms of calcium carbonate and calcium phosphate. An enamel-like surface region that allows for momentum transfer to prey caps this soft core. Here we investigate ultrastructure-mechanical property relationships of this outer “impact” region. Using high-resolution electron microscopy, we identify unique fiber architecture in conjunction with a highly textured apatitic mineral phase. In-situ nano-mechanical testing in combination with finite element modeling reveals a number of fracture-mitigation strategies that yield toughness to an already stiff and hard biomaterial.
5:15 PM - SM9.1.09
Why be Rigid: Structural Analysis of the Boxfish Carapace
Steven Naleway 1,Bernd Gludovatz 2,Maryam Hosseini 3,Jae-Young Jung 1,Eric Schaible 2,Robert Ritchie 2,Pablo Zavattieri 3,Marc Meyers 5,Joanna McKittrick 4
1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,2 Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley United States3 School of Civil Engineering Perdue University West Lafayette United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States,5 Department of Nanoengineering University of California, San Diego La Jolla United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United StatesShow Abstract
The ostraciidae family (i.e., boxfish) is known for their slow, well controlled swimming motion and complex dermal armor that can be traced back 55 million years. Their carapace is made of rigid scutes (plates), consisting of a mineralized plate and compliant collagen base, which connect by interdigitating in suture structures as opposed to overlapping (the more common design in fish species). The complex scheme of this carapace is structurally examined through in-situ mechanical testing (SEM and SAXS/WAXD) as well as computational analysis. Results show that, in shear, the mineralized suture interfaces are capable of interlocking while they simply pull apart in tension. The underlying collagen fibers are oriented in a complex cross-hatched pattern so as to provide resistance against stresses in multiple directions. Application to impact and piercing resistant bioinspired materials are discussed.
This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
5:30 PM - SM9.1.10
The Structure and Mechanical Functions of Keratinous Materials: Pangolin Scales and the Feather Shaft
Bin Wang 1,Marc Meyers 1
1 Materials Science, Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States,Show Abstract
Keratins are among the toughest biological materials, which have been a continuing source of inspiration to develop new functional materials. The pangolins scales and the feather shaft stand out with interesting functions: the scales are strong and resilient to resist sudden and repeated loads from predators, and the feather shaft is light-weight, strong and stiff, yet reasonably flexible. The structure and mechanical properties of scales from Chinese and African pangolins were correlated for the first time. They consist of flattened keratinocytes and show crossed lamellar structure (2~8 µm). Tensile and compressive behaviors under different strain rates, and along different orientations were studied. The feather shaft shows a cross sectional change of cortex and a layered structure with differentially oriented fibers along the shaft length, which work in synergy to provide adjusted bending stiffness and reasonable flexibility optimized for flight. The structure and mechanical functions were investigated and correlated through nanoindentation, tension, compression and flexure tests.
5:45 PM - SM9.1.11
Complex Water Repellency of Prickly Pear Cacti (Opuntia): Impact of Species, Biogeography, and Age on Nano-to-Macroscale Structure and Wetting Properties
Erik Woods 1,Rubin Linder 1,Lucas Majure 2,Konrad Rykaczewski 1
1 SEMTE Arizona State University Tempe United States,2 Desert Botanical Gardens Phoenix United StatesShow Abstract
The Sonoran desert has an incredible diversity of cacti, which poses an equally diverse number of morphological and physical characters. Somewhat surprisingly considering the xeric climatic conditions, strong water repellency is one of these physical characteristics. In particular, Opuntia, also known as prickly pear cactus, is among numerous plants that poses superhydrophobic characteristics.1 This hydrophobic property stems from waxy exterior (cuticle) with hierarchical nanoscale and microscale texture.2-4 In addition, Opuntia microdasys has complex multi-level, hair-like spines with a gradient of wettability that may efficiently collect water droplets from fog.5 Besides efficient fog collection technology,6 this mechanism has also inspired a new route to separate oil droplets from water.7 These two examples illustrate the potential rich diversity of technological innovations that could be inspired by cacti.
We investigated wetting properties of over 100 species within the genus Opuntia at the Desert Botanical Gardens’ living plant collection and found that only some species are superhydrophobic. In fact, different Opuntia species display a rich variety of wetting properties ranging from superhydrophilic to superhydrophobic. We observed that wetting properties depend not only on the particular species investigated but also on the location and age of the stem tissue analyzed. For example, on some plants the wetting properties can involve a macroscopic gradient, with old cladodes being superhydrophilic while new ones being superhydrophobic. To gain an insight into this rich diversity of wetting behaviors, we correlated observed contact angles to age-dependent surface hierarchical nano-to-microscale topology. We also used genetic information to relate different wetting patterns to evolutionary relationships and biogeographic origins of prickly pear cacti8. We show how this information can be used to infer relationships among climate, wetting characteristics, and their functionality for the different species of Opuntia.
1. Neinhuis, C.; Barthlott, W., Annals of Botany 1997, 79, 667-677.
2. Koch, K.; Barthlott, W., Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 2009, 367, 1487-1509.
3. Koch, K.; Bohn, H. F.; Barthlott, W., Langmuir 2009, 25, 14116-14120.
4. Salem-Fnayou, A. B.; Zemni, H.; Nefzaoui, A.; Ghorbel, A., Micron 2014, 56, 68-72.
5. Ju, J.; Bai, H.; Zheng, Y.; Zhao, T.; Fang, R.; Jiang, L., Nature communications 2012, 3, 1247.
6. Cao, M.; Ju, J.; Li, K.; Dou, S.; Liu, K.; Jiang, L., Adv. Funct. Mater. 2014, 24, 3235-3240.
7. Li, K.; Ju, J.; Xue, Z.; Ma, J.; Feng, L.; Gao, S.; Jiang, L., Nature communications 2013, 4.
8. Majure, L.C.; Puente, R.; Griffith, M.P., Judd, W.s.; Soltis, P.S., Soltis, D.E., American Journal of Botany,2012,99,847-864.
SM9.2: Poster Session I: Natural Materials
Wednesday AM, March 30, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM9.2.01
Investigating Hierarchical Protein Structures in Spider Silk
Brian Cherry 1,Chengchen Guo 1,Warner Weber 1,Forrest Thompson 1,Jacob Jordan 1,Kaylyn Riggs 1,Samrat Amin 1,Jeffery Yarger 1
1 Arizona State University Tempe United States,Show Abstract
Spider silks are protein-based biopolymers with extraordinary physical and mechanical properties. Much is known about the secondary molecular structure of spider silk fibers and its relationship to physical and mechanical properties. However, even in the most heavily studied spider silks little is know about organization or secondary structural motifs or further hierarchical organization. It is known that in the major ampullate gland two proteins (MaSp1 & 2) are generated for dragline silk production. The relative amounts of these two proteins within the silk gland and resulting fiber are known and vary between species. This variation is well correlated with the resulting fiber physical and mechanical properties. Our research group has utilized several spectroscopy and imaging modalities to investigate the protein structure at several length scales to gain insight into protein-protein interactions and structure-function relationships in spider silks. In this presentation, we will show our recent investigation of spider silks probed using Nuclear Magnetic Resonance (NMR), Magnetic Resonance Imaging (MRI), x-ray diffraction (XRD) and imaging modalities to better understand the hierarchical proteins structures that make-up spider silk fibers.
9:00 PM - SM9.2.02
Structure and Mechanical Properties of a Compression Resistant Beetle Exoskeleton
Jesus Rivera 1,David Kisailus 1
1 University of California, Riverside Riverside United States,Show Abstract
Exploiting available resources, nature has developed formidable damage tolerant composites through centuries of evolution. Exemplifying these traits, beetles possess resilient hardened protective forewings known as elytra. One example, the exoskeleton from the diabolical ironclad beetle, Phloeodes diabolicus, exhibits an outstanding adaptation to resist external loads that would prove fatal to most insects. Composed of layered fibrillar chitinous bundles embedded in an organic protein matrix, the beetle’s exoskeleton represents a biological composite with hierarchical construction. We identified two distinct regions in the structure that contribute to the overall mechanical strength. The elytra consists of an organized layers of uni-directional a-chitin fibers in a helicoidal arrangement. The ventral cuticle possesses a similar fiber arrangement and acts in tandem with the elytra to prevent lateral expansion as force is applied to the architecture. Cross sectional analysis reveals a support mechanism that joins the elytra to the ventral cuticle and engages upon compression. Our analysis provides insight into structural and mechanical properties of the elytra through compression, puncture and nanoindentation. Revealing the organism’s evolutionary design, current optical and mechanical analysis will exposes the structure property relationship of the ironclad beetle’s exoskeleton and can lead to the development of tough light weight composite materials for industrial applications.
9:00 PM - SM9.2.03
Mechanical and Microstructural Properties of Sea Urchin Teeth at Various Ocean Depths
Michael Frank 1,Steven Naleway 1,Kirk Sato 3,Steven Herrera 4,Wei Gao 6,Jae-Young Jung 1,Sze Hei Siu 2,Jerry Ng 2,Ivan Torres 2,Ali Ismail 2,Lisa Levin 3,Horacio Espinosa 6,David Kisailus 7,Joanna McKittrick 2
1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,3 Center for Marine Biodiversity and Conservation, Integrative Oceanography Division Scripps Institution of Oceanography La Jolla United States4 Department of Chemical and Environmental Engineering University of California Riverside Riverside United States5 Department of Mechanical Engineering Northwestern University Evanston United States,6 Department of Theoretical and Applied Mechanics Northwestern University Evanston United States2 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States4 Department of Chemical and Environmental Engineering University of California Riverside Riverside United States,7 Materials Science and Engineering Program University of California, Riverside Riverside United StatesShow Abstract
Biogenic magnesia calcites (Ca1-xMgxCO3) with x > 0.11-0.13 have greater ion activity products than pure calcites (x = 0, CaCO3), which implies that natural materials with high x are more soluble in acidified waters. Literature values for the stone part of the grinding tips in sea urchin teeth have x > 0.4, the highest value found among Ca1-xMgxCO3 bearing species. Naturally low pH water in the California Current system off the coast of Southern California occurs largely due to natural oceanographic processes such as upwelling. Expanding regions of high CO2 and low O2 from respiration beneath productive upwelled waters in oxygen minimum zones (OMZs) necessitates further study of broad-area persisting species, such as pink sea urchins (Strongylocentrotus fragilis), that inhabit a depth range of 100-1200 meters in habitats subject to acidification. Pink sea urchin teeth, collected from 100, 300, 700 and 1100 meters are analyzed mechanically to assess differences between ocean depths. Polished cross-sections of the stone part of the tooth grinding tip are nanoindented to compare hardness and stiffness values. The natural process for maintenance of a sharp tooth grinding tip is also examined. Individual teeth mounted to a microindenter tip holder are scratch tested on a hard substrate to analyze the self-sharpening mechanism at the serrated edge, where calcite plates are removed from the grinding tip due to shear stress. The tooth grinding tip is observed with nano-computed tomography to provide further insights about the microstructure. This work is supported by Multi-University Research Initiative through the Air Force Office of Scientific Research of the United States (AFOSR-FA9550-15-1-0009).
9:00 PM - SM9.2.04
Ultrasonic Waves to Predict Fracture in Bone Lamellae
Matthew Brownell 1,Jacob Loving 1,Arun Nair 1
1 Mechanical Engineering University of Arkansas Fayetteville United States,Show Abstract
The changes associated with bone structure and properties can lead to fracture of bone. One of the clinical tests for detecting the quality of bone uses ultrasound waves propagating through the bone to measure the bone mineral density. The ultrasound wave interaction with the medium can lead to information about its microstructure and material properties. At the micrometer scale, bone is made up of fibers, which are indeed composed of mineralized collagen fibrils. The fibers are aligned in different orientations, which make up the osteons and Haversian canals within the bone. The orientation of fibers and defects in fibers could affect the wave propagation. To gain a fundamental understanding of the ultrasound wave interaction with fibers within the bone, we use a multiscale approach, where the elastic constants of the mineralized collagen fibrils are predicted using atomistic simulations, which serves as an input for the continuum model of the fibers. Ultrasound waves are modeled to propagate through bone lamellae using the finite element method along with the Newmark’s constant acceleration method.
In the bone lamellae model, two energy flux waves are produced in plane. The faster quasi-longitudinal (QL) and the slower quasi-shear (QT), both of them deviate from the normal direction depending on the fiber orientations. It has been found out that, wave interaction with defects in lamellae will split the ultrasound wave into two distinct waves and the distance between the peaks of the split waves correspond with the size of the defect found in the bone lamellae. The studies outlined here, would lead to gaining a fundamental understanding of how ultrasound waves can predict fracture properties of bone.
9:00 PM - SM9.2.05
Maize Arabinoxylan Gels: Effect of Alkaline Hydrolysis Conditions on the Rheology and Microstructure
Rita Paz-Samaniego 1,Elizabeth Carvajal-Millan 1,Agustin Rascon 1,Yolanda Lopez-Franco 1,Norberto Sotelo-Cruz 2,Jaime Lizardi-Mendoza 1
1 CIAD Hermosillo Mexico,2 UNISON Hermosillo MexicoShow Abstract
The purpose of this research was to extract arabinoxylans (AX) from maize wastewater generated under different maize nixtamalization conditions and to investigate the polysaccharide gelling capability, as well as the rheological and microstructural characteristics of the gels formed. The nixtamalization conditions were 1.5 hours of cooking and 24 hours of alkaline hydrolysis (AX1) or 30 minutes cooking and 4 hours of alkaline hydrolysis (AX2). AX1 and AX2 presented yield values of 0.9% and 0.5% (w/v), respectively. Both AX samples presented similar molecular identity (Fourier Transform Infra-Red) and molecular weight distribution but different ferulic acid (FA) content. AX1 and AX2 presented gelling capability under laccase exposure. The kinetics of gelation of both AX samples was rheologically monitored by small amplitude oscillatory shear. The gelation profiles followed a characteristic kinetics with an initial increase in the storage modulus and loss modulus followed by a plateau region for both gels. AX1 presented higher storage modulus than AX2. In scanning electron microscopy (SEM) images, both gels present an irregular honeycomb microstructure. The lower FA content in AX2 form gels presenting minor elasticity values and a more fragmented microstructure. These results indicate that nixtamalization process conditions can modify the characteristics of AX gels. Environmental concerns have triggered research on alternative nixtamalization processes rendering residues with less environment impact. AX recovering from this kind of less pollutant maize wastewater could be an interesting research subject in order to explore the structural and functional properties of this hydrocolloid.
9:00 PM - SM9.2.07
Piriform Spider Silk Production
Cole Peterson 1,Randolph Lewis 1
1 Utah State University Logan United States,Show Abstract
Spider silk from N. clavipes have a range of useful properties in addition to remarkable mechanical properties. These silks are uniquely suited for biomedical applications as they are generally biocompatible and biodegradable. Piriform silk is an adhesive protein used by the spider to adhere its web to a variety of substrates. Sequencing of mRNA extracted from the piriform silk gland of N. clavipes has revealed two unique amino acid motifs. The structural role of these motifs in the resulting piriform silk attachment disk is unknown. The specific aim of this project is to produce recombinant piriform spider silk in Escherichia coli. Three biosynthetic proteins will be produced, two based on individual amino acid motifs and one based on the overall piriform sequence. The resulting piriform-analogue proteins will be used to produce fibers, films and gels for mechanical testing. The structural role of piriform’s unique motifs will be characterized using X-Ray Diffraction and Circular Dichroism on solid samples. Elucidating the mechanical and structural roles of these motifs will add to the existing repertoire of characterized motifs for the production of tunable, chimeric spider silk materials.
9:00 PM - SM9.2.08
Gelling, Spinning, and Filming: Chemical and Physical Properties of Novel Recombinant Spider Silk Materials
Thomas Harris 1,Justin Jones 2,Randolph Lewis 3
1 Biological Engineering Utah State University Logan United States,2 Biology Utah State University Logan United States3 Biology/Biological Engineering Utah State University Logan United StatesShow Abstract
Spider silks are incredible natural materials that possess combinations of strength and elasticity that exceed man-made materials. Traditionally harsh chemicals and long processing times have been required to form materials from these proteins. However, with the development of a new aqueous solubilization method for recombinant spider silk proteins, new possibilities for these proteins have been unlocked. This solvation method is easy, cheap, fast, and has even allowed for novel materials and proteins be investigated and characterized. Most notable among these materials developed from this method are fibers, films, hydrogels, lyogels, and sponges. These materials have been investigated using several different protein types, both native-like and chimeric, which have been purified from different expression systems. Finally, the structure, orientation, and consequently the mechanical properties of these various materials were the primary focus of these studies. Using various techniques and processing methods these mechanical properties can be increased or tuned to a range of desired applications.
9:00 PM - SM9.2.09
Isolating a Gene for Spider Glue
Kyle Berg 1,Michael Hinman 1,Paula Oliveira 1,Randolph Lewis 1
1 Biology Utah State University Logan United States,Show Abstract
The spider aggregate gland from orb weaving spiders produces a glue from aggregate protein that helps the web keep insects immobile long enough for the spider to capture it. Very little is known about the glue other than a partial genetic sequence and that the glue is sticky when wet. This opens a variety possible applications for a synthetically produced aggregate protein rangeing from underwater adhesives to surgical glue. We are cloning the aggregate cDNA to confirm and extend existing knowledge about the aggregate gene(s). mRNA was extracted from aggregate glands using TRIzol reagent, and then reverse transcribed using MMLV-RT to create single stranded DNA. The second strand was synthesized employing DNA Polymerase I in conjunction with RNaseH to form cDNA. The cDNA was ligated into pBluescript II SK (+) and transformed into electrocompetent DH10B bacterial cells. Bacteria were plated on ampicillin containing media and plates used had a colony density of approximately 1000 colonies per plate. Library screening has commenced with a probe designed using data from two previously reported sequences for the aggregate gene. Preliminary screening of the library using a fluorescent labeled probe was unsuccessful, but screening with a positive control sequence using a biotinylated probe has yielded promising results. We expect to obtain 2.5-3Kb of clear aggregate sequence from this library in order to confirm previous sequences and to allow us to express this gene synthetically.
9:00 PM - SM9.2.11
Strength and Failure of Eggshells
Andrei Pissarenko 1,Eric Hahn 1
1 UCSD La Jolla United States,Show Abstract
Eggshells can be easily broken by striking them at a local point. However, breaking it by squeezing the egg with a distriuted load, such as using one's hand to do so, is nearly impossible. Although the shell is a very thin porous calcium carbonate structure, its compressive resistance is an interesting feature. In this study, a new insight on these mechanical properties is provided through a series of experiments of compression of various kinds of bird eggs along their long-axis. Failure force scales with the thickness of the shell reaching loads upwards of five-thousand Newtons for ostrich eggs. Failure occurs by axial splitting parallel to the loading direction, spaced by a characteristic length. The spacing is the result of radial tensile stresses that develop from the applied compressive traction. These observations were then compared with calculations executed on a finite element model of an ovoide volume under compression using a maximum tensile stress criterion.
9:00 PM - SM9.2.12
The Ganoid Scales of Atractosteus spatula: Potential for Bioinspired Flexible Armor
Vincent Sherman 1,Marc Meyers 1
1 Materials Science and Engineering UC San Diego La Jolla United States,Show Abstract
The alligator gar (A. spatula) is covered with bony scales and an enamel-like surface layer. The scales form a tridimensional pattern in which neighboring scales overlap in such a manner that the thickness conforms and the sum of the overlaps is constant. The mechanical properties and structure are correlated and the tridimensional pattern revealed by computerized tomography is transferred by additive manufacturing to a magnified array of idealized, identical tiles. It is demonstrated that flexibility is maintained while protection is retained. This design is proposed as a model for bioinspired flexible ceramic composite personal armor. Research funded by AFOSR MURI.
9:00 PM - SM9.2.13
Structure and Toughening Mechanisms of the Coelacanth Fish (Latimeria chalumnae) Scales
Haocheng Quan 1,Wen Yang 2,Marc Meyers 1
1 UCSD La Jolla United States,2 Department of Materials ETH Zurich SwitzerlandShow Abstract
Coelacanths (Latimeria chalumnae) are known as living fossils because their morphology has little change in the last 300 million years. This lob-finned fish plays an important role in evolution because it bridges an evolutionary gap between fish and tetrapods. They have highly modified scales which are known as cosmoid scales which are typically found on extinct species of fish. The surface of the fish body with overlapped scales is rough and hard, which help protect the fish from predators. The scales are overlapped to each other and the degree of imbrication is about 0.3. The exposed part bears spines of denticles and annular ridges centerd on the apex of the scale are apparent on the surface of the overlapped part. The intervals of the ridges are about 30 μm. The out layer of the scales shows higher mineralization than the inner layers and provide protection.The major component of the overlapped region is isopedine, which is composed of layers of parallel collagen bundles. Each bundle is composed of collagen fibrils with typical 67nm d spacing. These bundles form layers with a double twisted system in which the directions of bundles in neighboring layers are almost perpendicular to each other, but successive bilayers show right-handed twisting arrangement. This double twisted arrangement can be clearly illustrated in 3D models and such unique structure results in an isotropic mechanical behavior. Such hierarchical structure does not provide much different tensile strength in longitudinal and transverse directions as the collagen bundles contribute equally in both orientations.
9:00 PM - SM9.2.14
Temperature Replica Exchange Simulations of Major Ampullate Spidroin 1 Minifibrils
Arjan van der Vaart 1,Jeffery Yarger 2,Geoffrey Gray 1,Brian Cherry 2
1 University of South Florida Tampa United States,2 Chemistry and Biochemistry Arizona State University Tempe United StatesShow Abstract
Dragline spider silk is one of the strongest biomaterials known and is primarily composed of major ampullate spidroin 1 (MaSp1) proteins. This long repetitive protein forms fibrils with alternating crystalline and non-crystalline regions, but many aspects of its structure and dynamics remain unclear. We have performed temperature replica exchange simulations of MaSp1 minifibrils consisting of one non-crystalline region surrounded by crystalline regions. The simulations show significant residual structure in the non-crystalline regions, consisting of 310 helical structures. In addition, persistent clusters of tyrosines were found. The occurrence of these clusters may help explain the anomalously large barrier of Tyr ring flips observed in solid state NMR measurements.
Joanna McKittrick, University of California, San Diego
Eduard Arzt, INM - Leibniz-Institut für Neue Materialien
David Kisailus, University of California, Riverside
Yurong Ma, Peking University
SM9.3: Natural Materials II
Wednesday AM, March 30, 2016
PCC North, 200 Level, Room 229 B
9:30 AM - *SM9.3.01
Architectured Materials in Engineering and in Nature
Francois Barthelat 1
1 McGill Univ Montreal Canada,Show Abstract
Architectured materials are characterized by specific structural features which are larger than what is typically considered microstructure (i.e. grains) but smaller than the size of the component. This class of materials includes lattice materials and foams, but also dense materials composed of building blocks of well-defined size and shape. While the deformations of the blocks typically remain small and within elastic limits, their interfaces can channel cracks and undergo large deformations. These features lead to building blocks which can slide, rotate, separate or interlock collectively, provide a wealth of tunable mechanisms. Well-designed architectured materials can therefore generate new and attractive combinations of properties which are unattainable in monolithic materials. Interestingly, there are many analogies between emerging architectured materials and hard biological materials such as bone, teeth or mollusk shells. I will particularly discuss nacre and fish scales, two examples or architectured natural materials which demonstrate how the interplay between the properties, shape, size and arrangement of the building blocks and nonlinear behaviors at the interfaces generates high properties. Duplicating these structures and mechanisms into engineering materials is very attractive, but the assembly of building blocks from the bottom-up and into highly ordered structures still presents major challenges. The top-down approach is a new strategy whereby weak interfaces are carved within the bulk of hard materials such as glass. This architectured / bio-inspired approach leads to materials with highly unusual combinations of properties which usually conflict: High stiffness and high toughness in a nacre-like glass, hardness and flexural compliance in fish scale-inspired coatings.
10:00 AM - SM9.3.02
Structure and Mechanical Properties of Selected Protective Systems in Marine Organisms
Steven Naleway 1,Jennifer Taylor 2,Michael Porter 3,Marc Meyers 5,Joanna McKittrick 4
1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,2 Marine Biology Research Division Scripps Institution of Oceanography La Jolla United States3 Department of Mechanical Engineering Clemson University Clemson United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States,5 Department of Nanoengineering University of California, San Diego La Jolla United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United StatesShow Abstract
Marine organisms have developed a wide variety of protective strategies to thrive in their native environments. These biological materials, although formed from simple biopolymer and biomineral constituents, take on many intricate and effective designs. The specific environmental conditions that shape all marine organisms have helped modify these materials into their current forms: complete hydration, and variation in hydrostatic pressure, temperature, salinity, as well as motion from currents and swells. These conditions vary throughout the ocean, being more consistent in the pelagic and deep benthic zones while experiencing more variability in the nearshore and shallows (e.g., intertidal zones, shallow bays and lagoons, salt marshes and mangrove forests). Of note, many marine organisms are capable of migrating between these zones. In this, the basic building blocks of these structural biological materials and a variety of protective strategies in marine organisms are discussed with a focus on their structure and mechanical properties. These protective strategies can be organized based upon their primary defensive and structural function into four distinct categories: crushing, flexure, piercing and impact resistant structures. Finally, the bioinspired potential of these biological materials is discussed.
This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
10:15 AM - SM9.3.03
Nano-Mechanical Experiments and Microstructure Analysis of Diatom Frustules and Diatom-Mimetic Structures Reveal Exceedingly High Specific Strength and Provide Insights into Evolutionary Design
Shi Luo 1,Zachary Aitken 1,Stephanie Reynolds 1,Christian Thaulow 2,Julia Greer 1
1 California Inst of Technology Pasadena United States,2 Norwegian University of Science and Technology Trondheim NorwayShow Abstract
Diatoms are single-cell algae that form a hard cell wall made of a silica/organic composite. One fascinating aspect of such silica glass shells is their intricate, varied and detailed architecture. It is well accepted that the diatom frustules mainly serve as protection, among other evolutionary functions. The question remains that how do the geometry and the microstructure of diatom frustules each contribute to their amplified structural resilience.
We conducted three-point bending on extracted lammelae from the Coscinodiscus sp. frustule with approximate square cross-section with dimensions ~3-4 µm. We observe failure by brittle fracture at an average stress of 1.1 GPa. Analysis of crack propagation and shell morphology reveals a differentiation in the function of the frustule layers with the basal layer pores seen deflecting crack propagation. We calculate the relative density of the frustule beam samples to be ~30% and show that the frustule has the highest strength to density ratios among reported biologic materials, at 1702 kN-m/kg. We also performed nanoindentation on both the single basal layer of the frustule and the girdle band and show that these components display similar mechanical properties that agree well with bending tests. TEM analysis reveals that the frustule is composed almost entirely of amorphous silica with a 275 nm-thick proximal layer displaying nanocrystalline microstructure. No flaws are observed down to 2 nm. FEM simulations of the three-point bending experiments reveal the stress distribution with a frustule beam sample and show that the load is carried primarily by the basal layer, while stresses within the cribrum and areolae layer are an order of magnitude lower.
We further fabricated silica architectures that fully replicate the diatom geometry using two-photon lithography. These biomimetic diatoms have a completely amorphous microstructure, and its elastic modulus matches that of the natural diatom biosilica. Three-point bending experiments of these synthetic diatoms reveal that cracks initiated and propagated in the same fashion as in Coscinodiscus sp. samples. Analysis of specific strength show that geometry does not solely account for the exceptional strength of natural diatom frustules. Comparison of failure strength also reveal potential mechanisms for the microstructure and silicification process of diatom frustules and provide insights to their evolutionary design.
10:30 AM - SM9.3.04
Mechanical Behavior of Tubular Structures in Horns and Hooves
Wei Huang 1,Alireza Zaheri 2,David Restrepo 3,Horacio Espinosa 2,Pablo Zavattieri 3,Marc Meyers 1,Joanna McKittrick 1
1 University of California, San Diego La Jolla United States,2 Northwestern University Evanston United States3 Purdue University West Lafayette United StatesShow Abstract
Tubular structure are one of the most impact resistant and energy absorbent structural designs and although studied for many years, remains an attractive research interest. Among the biological materials that have tubular structures, horns and hooves are excellent examples of impact resistant structures that have evolved for fighting or galloping of bovidae and equidae, respectively. Microstructures and mechanical behavior of the bighorn sheep (Ovis Canadensis) horn and African zebra (Equus burchelli) hoof were studied to examine mechanisms of impact resistant. Hooves and horns are composed of α–keratin crystalline intermediate filaments embedded in an amorphous matrix. Both have a tubular structure and a surrounding laminated structure. Optical and electronic microscope images showed the shape of tubule cross section in both horn and hoof are ellipses, ∼80μm (major axis) and ∼40μm (minor axis). However, the porosity in the horn is ∼7%, while in the hoof is ∼3.5%. The intertubular lamellae area is much larger in the hoof than that in the horn. Since anisotropy is an important factor in material properties, mechanical properties of horns and hooves were evaluated in three orthogonal directions (longitudinal, transverse and radial). Quasi-static compression test results showed strength and Young’s modulus were much higher in longitudinal and transverse direction than that in radial direction, while the radial direction was more energy absorbent because of the tubule collapse. Comparing horn and hoof structures, although the porosity in horn is two times that of the hoof, the compressive yield strength and Young’s modulus are higher in the horns in all the three directions, which demonstrated that horn structure was more energy absorbent in a quasi-static load. To determine how porosity affects the mechanical properties of tubular structures, 3D printed models of two different tubular densities (7% and 3.5%) were fabricated. At the same time, quasi-static and dynamic simulation of these two kinds of tubular models were carried out using finite element analysis, which showed a more uniformly distributed stress in transverse direction, leading to a higher stiffness. Kolsky bar dynamic test results as well as further finite element analysis on the tubular models will be presented. This work is supported by funding provided by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
10:45 AM - SM9.3.05
Catecholamine as a Reinforcing Agent in Mechanically Hard Grasshopper Mandibles
Kyueui Lee 1,Haeshin Lee 1
1 Department of Chemistry Korea Advance Institute of Science and Technology (KAIST) Daejeon Korea (the Republic of),Show Abstract
Hard biomaterials such as horn, teeth and jaws are essential in food digestion, defense, or prey hunting for survival. In particular, grasshoppers need strong mandibles (the organ functioning as teeth) to eat tough leaves. Herein, we propose a chemical mechanism demonstrating the mechanically strong mandible formation in grasshopper. The hardness of mandibles was approximately 0.4 Gpa, which is stronger than that of insect cuticle (approximately 0.25 Gpa). The mechanical strength of mandibles was exclusively achieved by the organic sources (i.e. carbon, nitrogen and oxygen), which is dissimilar from the teeth of other animals containing abundant inorganic elements. We found that catecholamine (i.e. dopamine) is the key molecule in hardening mandibles and presents in the protein chains as a form of dopamine-histidine. It has been reported that the acetylated-dopamine, N-acetyl-dopamine or N-β-alanyl-dopamine, plays a role in cuticular sclerotizaiton and tanning. The use of chemically unprotected dopamine for hardening tissues is the first report, suggesting that the air-sensitive dopamine might be an alternative molecule for constructing hard surfaces via prompt oxidation.
11:30 AM - *SM9.3.06
Revealing the Exceptional Deformability and Toughness of Reptilian Eggshells
Yin Chang 1,Po-Yu Chen 1
1 Department of Materials Science and Engineering National Tsing Hua University Hsinchu Taiwan,Show Abstract
Eggshells serve as multifunctional shields for successful embryogenesis, such as protection, moisture control and thermal regulation. Unlike calcareous avian eggshells which are brittle and hard, reptilians have leathery eggshells that are tough and flexible. Reptilian eggshells can withstand collision damages when laid in holes and dropped onto each other, and reduce abrasion caused by buried sand. In this study, we investigate structure and mechanical properties of eggshells of Taiwan cobra snake (Naja atra) which composed mainly of keratin. Mechanical tests showed that snake eggshells are highly extensible and reversible. The exceptional deformability (110-230% tensile strain) and toughness of snake eggshells are contributed by the wavy and random arrangement of keratin fibers as well as collagen layers. Multi-scale toughening mechanisms of snake eggshells were observed and elucidated, including crack deflection and twisting, fibers reorientation, sliding and bridging, inter-laminar shear effect, as well as the a-b phase transition of keratin. Inspirations from the structural and mechanical designs of snake eggshells may lead to the synthesis of tough, extensible, lightweight composites which could be further applied in the flexible devices, packaging and bio-medical fields.
12:00 PM - SM9.3.07
Nano- and Micromechanics of the Radular Teeth of the Chiton
Enrique Escobar de Obaldia 1,Chanhue Jeong 1,Steven Herrera 2,Lessa Grunenfelder 2,David Kisailus 2,Pablo Zavattieri 1
1 Purdue Univ West Lafayette United States,2 University of California, Riverside Riverside United StatesShow Abstract
The unique mechanical properties observed in biological materials distinguish themselves from common engineering materials. Some naturally occurring high-performance ceramics, like the external veneer of the Chiton tooth show a common feature, a rod-like microstructure. Nanoindentation tests not only provide some key mechanical properties of the surface of the tooth but are also an effective test to induce and analyze damage mechanisms at the nano- and micron-scale level. Despite these advantages, our ability to make direct observations about the potential abrasion resistance mechanisms acting at these small scales during these tests remains a challenging task. In this presentation, we will present a 3D finite element-based micromechanical model for the simulation of nanoindentation cracking in a fully mineralized tooth. This proposed model is capable of capturing damage, fracture and fragmentation of the mineral rods, and energy dissipation at the organic interfaces. A correlation between the rod-like ultrastructure and the abrasion tolerant properties will be discussed. A comparison of the model with indentation test in a 3D printing prototypes with similar features confirms the key role of the interactions between organic and mineral phases in the mechanical properties of biomaterials.
12:15 PM - SM9.3.08
Toughness-Enhancing Structure of the Recluse Spider Web
Sean Koebley 1,Fritz Vollrath 2,Hannes Schniepp 1
1 The College of William amp; Mary Williamsburg United States,2 Oxford University Oxford United KingdomShow Abstract
Spider silk is the toughest known biomaterial, and its energy absorption capacity is known to be further enhanced if the silk is arranged into an orb-web structure. The webs of non-orbweaving spider species, which are often more disorganized, have been less studied. But these alternatives offer potentially intriguing designs that are just as superbly adapted to their respective evolutionary niches. The recluse genus of spiders (Loxosceles) is one such non-orbweaver that spins an especially curious silk: instead of a cylindrical strand spun by most other spiders, it produces a flat ribbon 6–8 µm wide and only 40–80 nm thick. We show that Loxosceles spins these flat ribbons into a web structure that enhances toughness. Modeling of ideal elastic and strain-hardening plastic fibers arranged into this structure confirmed that the advantage is generally applicable, and key design parameters were identified. In addition to enhancing toughness, the Loxosceles web design was also found to contribute to the unique prey capture capacity of a ribbon-like silk. These advantages make the recluse silk-web system an ideal candidate for biomimicry in future synthetic materials.
12:30 PM - SM9.3.09
Nanocomposite Nature of Bone Drives Its Strength and Damage Resistance
Ottman Tertuliano 1,Julia Greer 1
1 California Institute of Technology Pasadena United States,Show Abstract
The hierarchical organization of components within bone has been credited with its remarkable combination of strength and toughness that outperforms those of its two main constituents, hydroxyapatite and collagen. Investigations of the mineral phase in other biogenic minerals revealed their amorphous microstructure in the mineralization stage. It has been proposed that in human bone, an amorphous mineral serves as a precursor to the formation of crystalline hydroxyapatite, i.e. bone growth, yet the mechanism for amorphous-to-crystalline transformation remains unknown. We use Transmission Electron Microscopy (TEM) to provide direct evidence of 100-300 nm-sized amorphous calcium phosphate (ACP) regions present in the disordered phase within the bone, which is located in the nodes of the trabecular network. We deprotinate the disordered phase and observe crystallization within the ACP. We extracted site-specific, cylindrical samples with diameters between 250 nm and 3000 nm from each phase, ordered and disordered, and performed dry, nanomechanical compression experiments on them. These experiments revealed a transition from plastic deformation to brittle failure and at least a factor of 2 higher strength in the nano-sized samples compared with micro-sized ones. We postulate that this ductile to brittle transition is caused by a suppression of interfibrillar shearing, and the emergent size effect of “smaller is stronger” is attributed to the scaling of the distribution of flaws with sample size. These findings have significant implications in our understanding of the multi-scale nature of bone, establishing a link between the microstructural detail and macroscopic properties of bone, as well as provide insights into its biomineralization process.
12:45 PM - SM9.3.10
Nano-Mechanical and Deformation Properties of Shell Structures
Edward Ampaw 1,Emmanuel Arthur 2,Tunji Owoseni 3,Adaviriku Malik 4,Ting Tan 5,Winston Soboyejo 7
1 Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria,1 Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria,2 Department of Materials Science and Engineering Kwara State University Malete-Ilorin Nigeria1 Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria,3 Department of Mechanical Engineering Kwara State University Malete-Ilorin Nigeria1 Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria,4 Department of Mechanical Engineering McGill University Montreal Canada5 Department of Civil and Environmental Engineering The University of Vermont Burlington United States1 Department of Materials Science and Engineering African University of Science and Technology Abuja Nigeria,6 Department of Mechanical and Aerospace Engineering Princeton University Princeton United States,7 Princeton Institute of Science and Technology of Materials (PRISM) Princeton University Princeton United StatesShow Abstract
The nano-mechanical properties of tortoise shell will be elucidated in this paper. This material experiences, and has been designed to endure, very different loading conditions in their environment and during their function. This work will explore the deformation and failure mechanisms of tortoise shell with interfaces between relatively "hard" and "soft" layers. Nano-indentation experiments will be used to study the hardness and deformation of the different layers. The work will also develop mechanics-based models for the design of robust materials. Insights from this work will be explored for the design of energy-absorbing materials such as helmets for motorcyclists and polo players which protect them from injury due to falls or hammer impact
SM9.4: Bioinspired Materials I
Wednesday PM, March 30, 2016
PCC North, 200 Level, Room 229 B
2:30 PM - *SM9.4.01
Smart Interfacial Materials from Super-Wettability to Binary Cooperative Complementary Systems
Lei Jiang 2
1 Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing China,2 School of Chemistry and Environment Beihang University Beijing China,Show Abstract
Learning from nature and based on lotus leaves and fish scale, we developed super-wettability system: superhydrophobic, superoleophobic, superhydrophilic, superoleophilic surfaces in air and superoleophobic, superareophobic, superoleophilic, superareophilic surfaces under water . Further, we fabricated artificial materials with smart switchable super-wettability , i.e., nature-inspired binary cooperative complementary nanomaterials (BCCNMs) that consisting of two components with entirely opposite physiochemical properties at the nanoscale, are presented as a novel concept for the building of promising materials [3-4].
The smart super-wettability system has great applications in various fields, such as self-cleaning glasses, water/oil separation, anti-biofouling interfaces, and water collection system .
The concept of BCCNMs was further extended into 1D system. Energy conversion systems that based on artificial ion channels have been fabricated . Also, we discovered the spider silk’s and cactus's amazing water collection and transportation capability , and based on these nature systems, artificial water collection fibers and oil/water separation system have been designed successfully .
Learning from nature, the constructed smart multiscale interfacial materials system not only has new applications, but also presents new knowledge: Super wettability based chemistry including basic chemical reactions, crystallization, nanofabrication arrays such as small molecule, polymer, nanoparticles, and so on .
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3:00 PM - SM9.4.02
Bioinspired Patterned Adhesives: From Science to Product Development
Eduard Arzt 1,Rene Hensel 1,Karsten Moh 1,Peter de Oliveira 1
1 INM – Leibniz Institute for New Materials Saarbruecken Germany,Show Abstract
Bioinspired adhesive surfaces have received much attention in scientific research over the last decade. Observation of adhesion organs in animals such as insects, spiders and geckos has led to important patterning concepts to enhance adhesion (the so-called contact splitting concept). Several laboratories have successfully fabricated artificial gecko structures, with 3D features in the range between sub-micron and hundreds of microns, on a laboratory scale and thus demonstrated that the principles from nature can be emulated with different polymeric materials. What is missing, however, is the link from small-scale laboratory samples to prototype products that demonstrate the feasibility of artificial gecko surfaces for targeted applications and the step to economic large-scale fabrication of such surfaces. At INM, we have recently taken the step to realistic engineering of such structures and thus created prototype demonstrators of our newly created Gecomer® technology. Advanced Gecomer® surfaces were implemented in pick-and-place procedures, including commercial robotic systems. Several release mechanisms were integrated to enable the handling of materials ranging from wafers to glass and paper. Realistic field and endurance tests were carried out under conditions of e.g. vacuum or higher temperatures. The talk will describe some of the critical issues whose solution may make Gecomer® technology one of the first successful examples of commercialized bioinspiration.
3:15 PM - SM9.4.03
Condensation on Slippery Asymmetric Bumps
Kyoo-Chul Park 2,Philseok Kim 3,Joanna Aizenberg 2
1 Harvard University Cambridge United States,2 Wyss Institute for Biologically Inspired Engineering Cambridge United States,3 SLIPS Technologies Inc. Cambridge United StatesShow Abstract
Controlling dropwise condensation is fundamental to water harvesting systems, desalination, thermal power generation, air conditioning, distillation towers, and numerous other applications. For any of these, it is essential to design surfaces that enable droplets to grow rapidly and be shed as quickly as possible. However, state-of-the-art approaches based on micro/nano or molecular scale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach based on principles derived from Namib desert beetles, cacti, and pitcher plants that synergistically couples both aspects of condensation and significantly outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle’s bumpy surface geometry in promoting condensation, and based on theoretical modeling, we show how to maximize vapor diffusion flux at the apex of convex millimetric bumps by optimizing radius of curvature and cross-sectional shape. Integrating this apex geometry with a widening slope analogous to cactus spines directly couples facilitated droplet growth with fast directional transport, by creating a free energy profile that drives the droplet down the slope before its growth rate can decrease. This coupling is further enhanced by a slippery, pitcher plant-inspired nanocoating that facilitates feedback between coalescence-driven growth and capillary-driven motion on the way down. Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity. We further observe an unprecedented six-fold higher exponent in growth rate, much faster shedding time and an order of magnitude greater volume of water collected compared to other surfaces. We envision that our fundamental understanding and rational design strategy can be applied to a wide range of water harvesting and phase change applications.
3:30 PM - SM9.4.04
Dynamics Self-Cleaning of Gecko Feet and Their Bioinspired Micromanipulator
Yiyang Wan 1,Zhenhai Xia 1
1 Univ of North Texas Denton United States,Show Abstract
Geckos have the extraordinary ability to keep their sticky feet from fouling while running on dusty walls and ceilings. Understanding gecko adhesion and self-cleaning mechanisms is essential for elucidating animal behaviors and rationally designing gecko-inspired devices. We report a unique self-cleaning mechanism possessed by the nano-pads of gecko spatulae in both dry and wet conditions. This study has provided direct evidence that the unique shape of nanoscale spatula pads plays a crucial role in generating robust and stable adhesion while permitting efficient self-cleaning capabilities in dynamic regimes. Inspired by this natural design, we have fabricated micro/nano-pad-terminated artificial spatulae and micromanipulators that show similar effects, and that provide a new way to manipulate microparticles in dry and aqueous environments. By simply tuning the pull-off velocity, our gecko-inspired micromanipulators, made of synthetic microfibers with graphene-decorated micro-pads, can easily pick up, transport, and drop off microparticles for precise assembling. This work should open the door to the development of novel highly-efficient biomimetic self-cleaning adhesives, smart surfaces, MEMS, tunable micro/nano-manipulators, biomedical devices, and more.
3:45 PM - SM9.4.05
Nonsolvent-Induced Phase Separation Synthesis of Biomimetic PVDF Microspheres for Superhydrophobic Coatings
Lance Brockway 2,Liam Berryman 2,Hayden Taylor 2
1 University of California Berkeley Berkeley United States,2 BEARS Singapore Singapore,Show Abstract
Polyvinylidene difluoride (PVDF) microsphere aggregate films with exceptionally high specific surface area have been synthesized using the Nonsolvent-Induced Phase Separation (NIPS) method. These structures are similar to the highly hydrophobic leaves of the plant Colocasia esculenta (Taro) in both geometry and physical properties. The individual spheres mimic the rough micro-nodules of the leaf, while clustering of the microspheres provides an additional layer of hierarchy, emulating the water-shedding capabilities of Colocasia esculenta.
The microsphere aggregates have been created by spinodal decomposition of a ternary solution of PVDF, dimethylformamide (DMF), and water, initiated by submerging spin-cast films in a water bath. The sphere diameter has been varied from 250 nm to 4 µm by modulating the initial composition of the system, while the film thickness is determined by the spinning speed. Additionally, the sphere surface roughness has been controlled by changing the phase separation temperature, and consequently, the relative diffusion rates of DMF and water.
These microsphere clusters are among the most superhydrophobic pure polymer structures produced to date, with contact angles in excess of 171°, contact angle hysteresis less than 12°, and a slide angle of 3°. Furthermore, the synthesis technique is reproducible and easily scalable, and the coating can be sprayed on to any surface to impart anti-microbial, self-cleaning, chemical-resistant, and water-repellent properties.
4:30 PM - *SM9.4.06
Biomimetic Materials and Structures for Innovative and Sustainable Bioinspired Building Construction
Thomas Speck 3
1 Plant Biomechanics Group Freiburg, Botanic Garden University of Freiburg Freiburg Germany,2 Competence Network Biomimetics Freiburg Centre for Interactive Materials and Bioinspired Technologies (FIT) Freiburg Germany,3 Freiburg Materials Research Centre (FMF) Freiburg Germany,Show Abstract
During the last decades biomimetics has attracted increasing attention as well from basic and applied research as from various fields of industry, architecture and especially from building construction. Biomimetics has a high innovation potential and offers the possibility for the development of sustainable technical products and production chains. The huge number of organisms with the specific structures and functions they have developed during evolution in adaptation to differing environments represents the basis for all biomimetic R&D-projects. Novel sophisticated methods for quantitatively analysing and simulating the form-structure-function-relationship on various hierarchical levels allow new fascination insights in multi-scale mechanics and other functions of biological materials and surfaces. On the other hand, new production methods enable for the first time the transfer of many outstanding properties of the biological role models into innovative biomimetic products for reasonable costs. Within the framework of the new Collaborative Research Centre CRC 141 “Biological Design and Integrative Structures” an interdisciplinary team aims to explore the potential of biomimetics for a new smart kind of bioinspired architecture.
After a short introduction into the topic, the interdisciplinary approach and the different process sequences for the development of biomimetic materials for building construction are presented, using examples from CRC 141 and PBG Freiburg. Main focus is laid on bioinspired light-weight and damping materials and structures as well as on self-x-materials. Examples include branched and un-branched fiber-reinforced light-weight composite materials and jackets for concrete pillars, structural materials with a high energy dissipation capacity as fiber-reinforced graded foams and thin-layer compound materials, bioinspired high-load bearing adhesive as well as anti-adhesive materials and surfaces; and various bioinspired materials and structures with self-x-properties as self-repairing structural materials and the biomimetic façade-shading systems flectofin® and flectofold inspired by the bird of paradise flower and the waterwheel plant, respectively.
5:00 PM - SM9.4.07
3D Printed Templating of Freeze Casting for Hierarchical Mimetic Bone
Steven Naleway 1,Jae-Young Jung 1,Sung Sik Hur 3,Yajur Maker 3,Kathryn Kang 4,Michael Ix 4,Shu Chien 3,Marc Meyers 5,Joanna McKittrick 4
1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,2 Institute of Engineering in Medicine University of California, San Diego La Jolla United States,3 Department of Bioengineering University of California, San Diego La Jolla United States3 Department of Bioengineering University of California, San Diego La Jolla United States4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United States,5 Department of Nanoengineering University of California, San Diego La Jolla United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,4 Department of Mechanical and Aerospace Engineering University of California, San Diego La Jolla United StatesShow Abstract
The recent interest in biocompatible and bioabsorbable bone implants over permanent devices has driven a multitude of research into bioinspired designs. Key to these designs is mimicking the complex hierarchical structure of cortical bone, which displays porosity on multiple length scales including larger osteons and smaller lacuna spaces. It is this porosity that promotes healthy bone growth. We present a novel method for the fabrication of bioinspired, hydroxyapatite-based materials that mimic this complex and hierarchical porosity. In this, smaller porosity is created by the freeze casting technique, where a ceramic scaffold is templated by the growth of ice crystals, while larger porosity is templated through the use of 3D printed structures. This results in final scaffolds with interpenetration between porosity at two length scales. The 3D printing process allows for a high level of control over the final porosity size and shape. Results show that cell viability is good and scaffolds have not shown toxicity. Cell proliferation and differentiation will be assessed. Applications as biomedical implants and structural materials will be discussed.
This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
5:15 PM - SM9.4.08
Composites Reinforced via Mechanical Interlocking of Surface-Roughened Microplatelets
Rafael Libanori 1,Davide Carnelli 1,Luc Nicoleau 2,Bernhard Feichtenschlager 2,Gerhard Albrecht 2,Andre Studart 1
1 ETH Zurich Zurich Switzerland,2 BASF Construction Solutions Trostberg GermanyShow Abstract
Load-bearing reinforcing elements in continuous matrices allow for improved mechanical properties and can reduce the weight of structural composites. As the mechanical performance of the system is heavily affected by interfacial properties, tailoring the interactions between polymer matrices and reinforcing elements is a crucial problem. Recently, several studies using bio-inspired model systems suggested that interfacial mechanical interlocking can lead to an efficient energy dissipation mechanism in platelet-reinforced composites. While cheap and effective solutions are available at the macroscale, modifying the surface topography of micron-sized reinforcing elements still represents a challenging task. In this study, we report a simple method to create nanoasperities with tailored sizes and densities on the surface of alumina reinforcing platelets and investigate their effect on the energy dissipation mechanisms of bioinspired nacre-like materials. Epoxy-based composites reinforced with surface-roughened platelets exhibited enhanced energy dissipation during fracture, leading to values of work of fracture and resistance against crack propagation that are 110% and 30% higher than its non-roughened counterpart, respectively. Understanding the role of surface nanoasperities in mechanically-interlocked interfaces provides valuable design guidelines for the development of advanced and lightweight materials with a potential impact on the minimization of energy demand and carbon footprint in the transportation and construction sectors.
5:30 PM - *SM9.4.09
Bioinspired Multifunctional Materials
Rajesh Naik 1
1 Air Force Research Laboratory Wpafb United States,Show Abstract
Nature has many examples of protein-based composites that are optimized for mechanical strength and durability. Silkworm silk fibers are protein composites made up of sericin and silk fibroin where the two proteins are spun together in a coaxial arrangement. The arthropod endocuticle is a tough, flexible component of the exoskeleton and is made up of chitin and proteinaceus layers forming a protein/polysaccharide composite. Due to their complexity and diversity, proteins and carbohydrates hold great promise in the creation of novel biomaterials. This is largely related to their chemical versatility which can result in programmable and complex functions. The knowledge gained in understanding how biological materials are constructed will enable bio-inspired design and fabrication of functional materials with tailored properties. In this talk I will cover research undertaken by our group in exploring the structure-property relationships of silk and other biopolymers, and their use in creating multifunctional materials. I will also discuss our results on the use of 3D direct write processes for protein-based materials. The utilization of proteinaceous materials in direct write processes is particularly attractive as these polymers offer aqueous processability, robust mechanical properties, chemical functionality, biomolecular recognition motifs, and self-assembly capabilities not found in synthetic inks.
SM9.5: Poster Session II: Bioinspired Materials
Thursday AM, March 31, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM9.5.01
Fabrication of Bio-Inspired Dry Adhesive Pads Using CNT/PDMS Composite
Minho Seong 1,Hoon Yi 1,Hangil Ko 1,Insol Hwang 1,Hoon E. Jeong 1
1 UNIST Ulsan Korea (the Republic of),Show Abstract
Micro- or nanostructures with thin-film-like tips on the feet of climbing creatures contribute to their remarkable adhesion capabilities. Micro- or nanostructures with a protruding thin-film tip can exhibit superior adhesion properties in comparison to chemical-based ones because the adhesion force mainly originates from intermolecular interactions owing to the attractive van der Waals forces between the tips and the contact surface.
Motivated by such fascinating structures, many research groups have developed fabrication methods based on various top-down and bottom-up approaches for designing similar artificial structures. We have demonstrated beetle-inspired microscale structures with mushroom-shaped tips as a biomimetic dry adhesive, which can produce 2−30 times higher pull-off force than pillars with simple flat or hemispherical heads because of the enhanced contact area, pollution tolerance, homogeneous stress distribution, and prevention of crack propagation. Furthermore, these microscale structures are relatively easy to produce in a scalable manner and are mechanically more durable as compared with the slanted hierarchical hairy nanostructures. Therefore, these adhesive pads show a strong potential to replace existing gripping techniques such as vacuum suction or electrostatic chucks since dry adhesives enable precise transportiation of various substrates without any surface contamination in a reversible, repeatable, and durable manner.
To fabricate mushroom-like microstructures, poly-dimethylsiloxane (PDMS) is generally utilized because its favorable mechanical properties (low elastic modulus and high elongation at break) allow for simple prototyping and enhanced normal and shear adhesion strength. Nonetheless, it shows inherent limitations in maintaining its form and adhesion strength at high temperatures (>200°C), which restricts high-temperature applications. To address this problem, we fabricated mushroom-like microstructures using carbon nanotube (CNT)/PDMS composites, which enables enhanced thermal stability (>300°C) while maintaining proper adhesive forces. Furthermore, this composite microstructure exhibits good electrical conductivity (10 S/m). As a result, this bio-inspired composite adhesive pad has a strong potential to be used for a variety of applications from functional adhesives for high-temperature processing to conductive adhesives for sensory or electrical devices. To demonstrate unique applications of the composite adhesives, we used the composite adhesive pads for precise transportation of delicate Si wafers at a high temperature (250°C).
9:00 PM - SM9.5.02
Tree Frog-Inspired Friction Pads for Delicate Substrate Transportation in Dry/Wet Conditions
Hangil Ko 1,Minho Seong 1,Hyun-ha Park 1,Joosung Lee 1,Hoon E. Jeong 1
1 UNIST Ulsan Korea (the Republic of),Show Abstract
Tree frogs are widely known for their abilities to stick on the vertical surface of trees using their feet, which contain micro-scaled hexagonal pillars that lead to high friction in dry/wet conditions. Inspired by this amazing and useful feature of tree frogs, in this research, we fabricated bio-inspired friction pads having micro-hexagonal pillars for transportation of various substrates in both dry and wet conditions.
During the manufacturing process of semiconductor or display devices, silicon wafer or glass substrates ought to be carefully transported with high speed and reliability avoiding any surface contamination, slip, or fracture, because the substrates are usually very thin, large in size, sensitive, and fragile. However, the existing equipments for substrate transportation, such as electrostatic chuck, mechanical chuck, and vacuum suction have very limited performance. In the case of electrostatic chuck, very high voltage (~3 kV) is used; many contaminates such as dust can gather around the substrates by electrostatic force and this system is also expensive. In the case of mechanical chuck, the substrates should be in contact with the chuck, which could lead to mechanical failure and surface contamination.
As a solution to the limitations mentioned above, we propose the use of tree frog-inspired friction pad with micro-hexagonal pillars. This system not only requires low energy consumption but also prevents contamination and provides high friction with short manufacturing time and low cost. Using this technique, silicon wafers or glass substrates could be transported in dry and wet conditions with high speed and reliability, avoiding any slipping movement or contamination through contact. Artificially manufactured micro-scaled hexagonal pillars on the pad showed excellent frictional properties, which meets the industrial criteria, and proves their ability to prevent stick-slip of the substrate, realized by controlling parameters including diameter, spacing ratio, and aspect ratio of the micro-scaled pillars. Moreover, the bio-inspired friction pad is made of poly-dimethylsiloxane through photolithography and molding/demolding process. Therefore, it exhibits a dry-adhesive property, which shows no contamination by contact under repeated cycles of transportation test. Consequently, the tree frog-inspired friction pad with micro-hexagonal pillars has a great potential for industrial application due to its high friction in dry/wet conditions, dry-adhesive property, and ability to prevent slipping of the substrates.
9:00 PM - SM9.5.03
Octopus-Inspired Omni-Stick Patches Using Programmable Multiscale Architectures
Sangyul Baik 1,Dawan Kim 1,Taekyung Min 2,Changhyun Pang 1
1 Sungkyunkwan Univ. SUWON-SI Korea (the Republic of),2 Advanced Institute of Nanotechnology (SAINT) Sungkyunkwan Univ. Suwon-si Korea (the Republic of)2 Advanced Institute of Nanotechnology (SAINT) Sungkyunkwan Univ. Suwon-si Korea (the Republic of),1 Sungkyunkwan Univ. SUWON-SI Korea (the Republic of)Show Abstract
Bio-inspired artificial attachments from various biology systems have extensively applied in various fields such as smart dry-adhesives, medical patches, and robotics. To improve reversible dry and wet adhesion on rough surfaces, the intimate contact between two different surfaces is essential for the amplification of van der Waals force, capillarity, and suction effect. Here, we demonstrated octopus sucker-like 3-dimensional microstructures which resulted in high Omni-adhesion in dry, water, oil condition. Particular architectures of micro-hills of octopus suckers are known to interplay with adjunct surfaces and generate secondary pressure-responsible chambers for dry and wet surface adhesions. After the investigations of underlying mechanisms of adhesion process of octopus suckers, we developed Omni-stick patches of artificial 3D micro-suckers and the lift-off is extremely simple and effortless by peeling off one of the layers in contact. The various unique micro-suckers can be fabricated by simple replication and partial-curing techniques with polydimethysiloxane and UV-curable poly-urethane. To control of particular 3-dimensional nano-architectures, we introduced the air-trap technique in micro-hole chambers, allowing mimicking micro-hill of octopus suckers. We analyzed the adhesion in various dry and wet conditions depending on the hierarchical shape of suckers and preload effect. We proceed to demonstrate that the thin patches which has densely populated micro-sucker is capable of high adhesion on human skin, leading to develop the less-irritating skin-patches with beads of sweat for skin-attachable devices and wound-healing systems.
9:00 PM - SM9.5.04
Beyond the Fiber: Novel Spider Silk Coatings and Adhesives
Breton Day 1,Danielle Gaztambide 1,Thomas Harris 1,Ashley Ruben 1,Randolph Lewis 1
1 Utah State University North Logan United States,Show Abstract
This research investigates the use of aqueous-based recombinant spider silk proteins as coatings and adhesives. Biodegradability, biocompatibility, and functionality are the hallmarks of these revolutionary materials. Spider silks have the ability to adhere to several different substrates, including silicone and hydrophobic plastics, and these coatings can be modified depending on the potential applications. Drug-eluting coatings have the ability to release consistent dosages of antibiotics, growth factors, hormones, and antimycotics in addition to preventing blood clotting and biofouling. This highlights their potential to revolutionize medical implants and in vivo materials. Furthermore, biodegradable spider silk adhesives are strong enough to rival and outperform conventional glues on the market and display low immunogenicity. Applications for these aqueous materials are broad, ranging from the textile and military industries to the medical field. The absence of harsh organic solvents increases cost effectiveness, safety, and decreases the environmental impact of these materials.
9:00 PM - SM9.5.05
Synthesis and Characterization of Monetite with Thin Nacre-Like Structure
Song Chen 1,Shun Yu 2,Hakan Engqvist 1,Wei Xia 1
1 Uppsala University Uppsala Sweden,2 KTH Royal Institute of Technology Stockholm SwedenShow Abstract
Introduction: Nacre-like structures, due to their outstanding toughness, stiffness and impact resistance, have attracted great interest in recent years. However, engineering nacre-like calcium phosphate crystals still remains a challenge. Although monetite with different morphologies and sizes have been prepared by different techniques, there are no reports regarding the synthesis of monetite with a nano-layered structure. In this paper, we synthesized monetite crystals with thin nacreous structure via a self-assembly process. A possible mechanism for this biomimetic process has been discussed.
Experimental: 17.71 g Ca(NO3)2.4H2O and 1 g cetyl-trimethyl ammonium bromide (CTAB) were dissolved in 25 ml pure water, marked solution 1.1 ml NH3.H2O was added in the solution. 7.49 g (NH4)2HPO4 was dissolved in anther beaker with 25 ml pure water, marked solution 2. Solution 2 was dropped into solution 1 and the final solution was stirred at 90 °C for 3 h. The resultant powder was washed with ethanol and isolated by centrifugation. When preparing monetite in lower concentration precursor solutions, 0.59 g Ca(NO3)2.4H2O, 0.6 g CTAB and 1 g NH3.H2O were dissolved in 25 ml pure water and 0.198 g (NH4)2HPO4 was dissolved in another 25 ml pure water. (NH4)2HPO4 solution was dropped into Ca(NO3)2.4H2O solution and the final solution was stirred at 90 °C for 3 h. The final powder was characterized by X-ray diffraction (XRD) analysis, Scanning electron microscopy (LEO 1550-SEM) and Small Angle X-ray scattering (SAXS).
Results and Discussion: Monetite sheets with a nacre-like structure were synthesized. The nanolayer thickness was calculated around 2.6 nm on a basis of the SAXS. Under lower concentration the monetite sheets were stacked with well-oriented small fibers. Despite of variations in temperature, pH and amounts of CTAB, the resultant crystals were all single-phase monetite. However, without CTAB, only irregular sheet-like monetite could be observed, indicating that CTAB was essential in forming such layered nanostructures. Temperature also played a vital role in the self-assembly process of monetite. No nacre-like structure could be observed at 25°C and 60°C. The morphology of monetite changed with initial pH of the Ca(NO3)2 solution. The reaction should be carried out in a basic solution in order to form the nacre-like structure.
Conclusions: Thin nacre-like monetite sheets were successfully synthesized in solutions guided by surfactant. The monetite sheets could be assembled either from nano sheets or fibers. The distance between nano layers was around 2.6 nm. The concentration of CTAB, initial pH and temperature played key roles in forming monetite with nacre-like structures.
Acknowledgements: We gratefully acknowledge support from VR (Swedish Research Council (2013-5419) and China Scholarship Council (CSC) for the PhD study.
9:00 PM - SM9.5.06
Kidding Around: Making Spider Goats
Richard Decker 1,Dylan Memmott 2,Brittany Patterson 1,Randolph Lewis 1
1 Biological Engineering Utah State University Logan United States,2 Biology Utah State University Logan United States2 Biology Utah State University Logan United States,1 Biological Engineering Utah State University Logan United StatesShow Abstract
Synthetic spider silk has an array of potential uses, ranging from high-end athletic gear to replacement ligaments. The major limiting factor in synthetic spider silk research is the quantity of available silk proteins. Currently, expression in transgenic goats’ milk is the best method available for large-scale production of silk proteins, but the silk protein purification process is long, expensive, and inefficient. In order to increase the yield and purification efficiency of synthetic spider silk proteins in goat milk, "spider goats" are being created that will produce proteins designed for improved purifications. Multiple systems for incorporating spider silk genes into the goat genome are being employed: two commercially available random integration systems, PiggyBac and pBC1, have been combined to create a suitable expression system, and two methods of targeted genomic editing, CRISPR/Cas9 and TALENs, are also being used. Both the CRISPR/Cas9 and TALEN systems can be engineered to create targeted cuts in a genome. The goat alpha-s2-casein gene, which codes for a native milk protein, is being targeted for gene replacement with spider silk coding genes. The silk coding regions will contain a poly-histidine tag to allow for faster, more efficient purification than the current system. These new “spider goats” will allow more research to be done regarding spider silk applications, improving the commercialization potential of synthetic spider silk.
9:00 PM - SM9.5.07
Functionally Graded Adhesive Bonding of Additively Manufactured Components
Edem Dugbenoo 1,Muhamad Arif 1,Kumar S 1
1 Masdar Institute Abu Dhabi United Arab Emirates,Show Abstract
Functionally graded structures found in nature are known to exhibit mechanical properties superior to that of similar ungraded structures. These functionally graded structures are characterized by varying levels of stiffness across some length of the body, resulting in a uniform distribution of stresses when mechanical forces are applied to it. Several analytical models and finite element simulations carried out for adhesive joints have shown that varying the stiffness of the adhesive along the bond length significantly improves the bond strength by reducing the peak stresses at the ends of the overlap. The practical implementation of such functionally graded adhesive bondlines has however proved challenging due to difficulties in controlling the flow of the adhesive when forming the joint using traditional manufacturing processes.
Leveraging on the flexibility provided by additive manufacturing technologies, a single lap joint consisting of 3D printed adherends, bonded by a layer of epoxy which was carefully controlled to a predetermined thickness and length has been successfully fabricated. The level of control provided by this method allows for the development of a functionally graded adhesive joint, where the stiffness of epoxy along various sections of the bondlength is tailored using varying weight fractions of carbon nanofillers in these sections.
Given that additive manufacturing is increasingly being adopted by the aerospace and automotive industries for the fabrication of end products, this ability to bond parts – which are too large to produce in a single build – with a functionally graded adhesive would allow for the development of stiffer structures without the significant weight penalty usually associated with such improvements in mechanical properties.
9:00 PM - SM9.5.08
Bioinspired Geometrically Interlocked Design of 3D Printed Joints
Noel Oliva 1,Kumar S 2
1 Masdar Institute Abu Dhabi United Arab Emirates,1 Masdar Institute Abu Dhabi United Arab Emirates,2 Mechanical MIT Cambridge United StatesShow Abstract
The mechanical behavior of adhesive joints is strongly dependent on the morphology of the adhesive-adherend interface. The human skull, tooth and nacre are some examples of biocomposites found in nature which exhibit enhanced mechanical properties due to strengthening and toughening mechanisms associated with the geometrically interlocking architecture of interfaces. Inspired by the nature, and driven by the unlimited possibilities that the additive manufacturing offers, this study is focused on computational and experimental performance evaluation of a single lap joint with a wavy interface, containing a positive and a negative semicircular shape teeth per cycle, in such a way that the thickness along the bondlength is kept constant and the joint is symmetric about the mid-bondlength. The undulating configuration of joining surfaces of both adherends accomplishes the mechanical interlocking. Finite element analysis (FEA) indicates that a complex state of stress/strain is created due to the changes in geometry from that of the flat interface. It was observed that the adhesive stresses in the interlayer of the joint depends on the number of cycles, the radius of the tooth, its distribution over the bond length, and if the cycle starts with a negative tooth or a positive one. This dependence is also evaluvated by performing tensile tests on 3D printed joints. Both experimental and computational results indicate that the joints with wavy interface have higher strength and damage tolerance than those of joints with flat interface. A systematic parametric study is conducted by varying the geometric and material properties of the non-flat interface in order to identify an optimal design configuration of the wavy interface.
9:00 PM - SM9.5.09
Large Scale Production of Spider Silk Protein in E. coli
Gargi Bhattacharyya 1,Paula Oliveira 1,Randolph Lewis 1
1 Utah State University Logan United States,Show Abstract
Spider silks have long been a focus of research due to their remarkable mechanical properties including strength, toughness and elasticity. Moreover, biodegradability and biocompatibility of spider silks make them beneficial to use in biomedical applications. Spiders cannot be farmed because of their territorial and cannibalistic nature. Hence, production of recombinant spider silks is the only feasible solution for large scale production. Various heterologous hosts including microbial system have been explored to produce recombinant spider silk. Though new advances in genetic engineering have paved the path to produce various kinds of recombinant spider silks, large scale production is still challenging due to the small recombinant protein size, low yield and low water solubility of bio-synthetic spider silk. The current study reports our recent progress in bio-synthetic production of spider silk protein in E. coli. We have constructed different vector systems with various spider silk protein genes. We have used the consensus motif of naturally occurring highly repetitive spider silk sequences along with a non-repetitive sequence at the C-terminal of the protein from the golden orb weaving spider Nephila Clavipes. In order to increase expression levels of recombinant spider silks that are rich in glycine or proline, an additional plasmid was incorporated into E. coli to produce higher levels of tRNAs for glycine and proline. In another vector system a gene that results in the expression of serine hydroxyl methyl transferase (SHMT), which converts the amino acid serine to glycine, was incorporated along with the t-RNA expression genes. With media optimization and protein induction studies, we have developed a fermentation process, which can express spider silk proteins in E. coli in the level at or above 1.0 g/L.
9:00 PM - SM9.5.10
Development and Evaluation of Hydrocolloid Wound Dressing Using Synthetic Rubber and Sodium Carboxymethylcellulose (CMC)
Oh Hyeong Kwon 1,Won ho Park 2,Donghwan Cho 1
1 Kumoh National Institute of Technology Gumi Korea (the Republic of),2 Chungnam National University Daejeon Korea (the Republic of)Show Abstract
To develop functional hydrocolloid wound dressing, synthetic rubbers and sodium carboxymethylcellulose (CMC) was used as based materials. Incorporation of an absorption agent with optimum ratio in a hydrocolloid matrix is a critical issue as a wound healing material to manage exudation. To determine optimum mixing ratio of hydrocolloid and CMC, 5 kinds of samples were prepared by varying CMC amount (10~50 wt%). Surface morphology of each hydrocolloid containing CMC was analyzed by scanning electron microscopy. Elongation at break and adhesive force were measured using an universal testing machine. Cell viability was analyzed by MTT assay. And wound recovery rate was evaluated by in vivo animal (rats) model experiment. Furthermore, skin irritation test were carried out using in vivo rabbit model. Hydrocolloid wound dressing prepared in this study showed increased absorptivity, decreased elongation at break and adhesive forces with increasing content of CMC, consistently. Hydrocolloid with 40% of CMC is determined as the optimum composition and its elongation at break, adhesive force, water absorptivity and moisture vapor transmission rate were more than 400%, 1.78 kgf/25 mm, 327% and 547 g/m2/day, respectively. Hydrocolloid group containing 40% of CMC showed 87% of cell viability after 7 days of in vitro cell culture test (ISO 10993-5) and in vivo animal study demonstrated significant wound recovery rate than control groups (commercialized hydrocolloid wound dressing products). Also it was no stimulation from in vivo irritation test on a naked rabbit skin. From these investigations, it is confirmed that hydrocolloid containing 40% of CMC will provide the crucial clue as advanced wound healing materials.
Joanna McKittrick, University of California, San Diego
Eduard Arzt, INM - Leibniz-Institut für Neue Materialien
David Kisailus, University of California, Riverside
Yurong Ma, Peking University
SM9.6: Bioinspired Materials II
Thursday AM, March 31, 2016
PCC North, 200 Level, Room 229 B
9:00 AM - *SM9.6.01
Understanding of Bacterial Magnetite Formation toward Designed Synthesis of Magnetic Nanocrystals
Atsushi Arakaki 1,Ayana Yamagishi 1,Tadashi Matsunaga 1
1 Tokyo University of Agriculture amp; Technology Tokyo Japan,Show Abstract
Living organisms produce inorganic nano-materials possessing unique structure and property. This bioprocess called biomineralization is an attractive strategy for development of diverse inorganic material production in mild condition, whereas the regulation of biomineralization is still challenging.
Magnetotactic bacteria synthesize nano-sized single crystalline magnetite (Fe3O4) within the cell. Various crystal morphologies observed in nature are species or strain dependent, which implies a high degree of biological control. During the analyses of surface proteins from bacterial magnetites, we identified a group of proteins, termed Mms proteins, which play key roles in crystal growth and morphological regulation of cubo-octahedral magnetite.
In this talk, we present in vivo function of Mms proteins. We show that the morphology, size, and surface structure of the magnetite crystal in the bacteria are regulated by the cooperative action of multiple proteins localized on the crystal surface. Our results also suggest that the morphology, size and surface structure of magnetite crystals can be fine-tuned by controlling the expression of these proteins and that it is possible to design magnetic materials with desired morphological and magnetic characteristics. A new strategy for the production of magnetite crystals to use biological system will be introduced.
9:30 AM - SM9.6.02
Bioinspired Composites by Vacuum Assisted Magnetic Alignment
Madeleine Grossman 1,Florian Erni 1,Florian Bouville 1,Rafael Libanori 1,Andre Studart 1
1 ETH Zurich Zurich Switzerland,Show Abstract
The rational design of high strength composites with high fracture toughness is a major challenge in materials science because the molecular origins of strength and toughness tend to conflict . Yet, nature demonstrates that it is possible to create composite materials that avoid molecular level conflicts between strength and fracture toughness by arranging their building blocks in interconnected, hierarchical meso-structures. Inspired by the brick and mortar meso-structure of nacre, this work aims to materialize an example of a structural fracture-toughening mechanism in a high strength composite.
Using the new technique of Vacuum Assisted Magnetic Alignment (VAMA), it is now possible to quickly and easily produce nacre-like ceramic scaffolds, of several cubic centimeters volume, with uniform micro-scale brick and mortar architecture and controlled mineral connectivity. Using titania-coated alumina platelets as a starting material exploit the fact that titania dewets the surface of of alumina platelets at high temperatures to create tunable connections and asperities at platelet-platelet interfaces within the nacre- like structure. Through systematic variation of the sintering temperature, a series of interfacial morphologies have been produced; ranging from frictional contacts between interlocking nano-asperities to fully sintered mineral contacts. Infiltration with toughened epoxy yields series of composites with similar mineral volume content, yet very different mechanical properties: the flexural moduli range from 90-180GPa and flexural strength 270-370 MPa. As the interfacial mineral contacts approach their optimum strength, the fracture toughness of the composite, KIC, increases up to 50%, however composites with over-sintered mineral contacts become more brittle. These results support the hypothesis that platelet-platelet interfaces with optimised surface morphology have central importance in the fracture resistance mechanisms of natural nacre.
 Ritchie, R.O., The conflicts between strength and toughness. Nature Materials, 2011. 10(11): p. 817-822.
9:45 AM - SM9.6.03
Bioinspired by Bone: Magnetized Alumina for Strengthened Porous Scaffolds by Magnetic Freeze Casting
Michael Frank 1,Steven Naleway 1,Tsuk Haroush 2,Chin-Hung Liu 1,Sze Hei Siu 2,Jerry Ng 2,Ivan Torres 2,Ali Ismail 2,Joanna McKittrick 2
1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,2 Department of Mechanical and Aerospace Engineering, University of California, San Diego La Jolla United States1 Materials Science and Engineering Program University of California, San Diego La Jolla United States,2 Department of Mechanical and Aerospace Engineering, University of California, San Diego La Jolla United StatesShow Abstract
Bone consists of a hard mineral phase and a compliant biopolymer phase resulting in a composite material that is both lightweight and strong. Osteoporosis is a disease that degrades spongy bone preferentially over time and leads to bone brittleness in the elderly. The current solution is a bone implant made of titanium that is often too stiff and requires follow-up surgery. A porous ceramic material that can mimic spongy bone for a one-time implant is a much better solution for future needs of an aging population. One method to produce porous scaffolds is freeze casting of ceramic powders. Freeze casting with an applied magnetic field provides a unique method for making a porous scaffold that resembles spongy bone. The fabrication process uses the freezing of water to separate a slurry of magnetized ceramics (alumina particles or platelets) into lamellae between growing ice crystals. A weak magnetic field applied at the same time throughout the freezing induces alignment of those lamellae structures. The frozen block is then freeze dried to extract the ice and sintered to produce a porous scaffold with aligned pores in both the longitudinal (ice growth direction) and transverse (magnetic field direction) axes. Compression testing of scaffolds in the transverse axis, which were subject to an applied magnetic field, revealed a two to three times stiffness enhancement due to the visible alignment of the pores. This result mirrors how spongy bone pores naturally align within the load bearing direction of the ball-and-socket hip joint. Alumina particles and platelets surface magnetized with charged ferrofluid are new functional materials that can be used for fabrication of multi-axis strengthened porous structures. Magnetic properties of magnetized materials with different sizes and aspect ratios are compared with theoretically derived values. The ideal magnetic field strength needed to induce alignment throughout the scaffold center, rather than just at the poles will be presented. This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
10:00 AM - SM9.6.04
Bio-Inspired Synthesis of Multifunctional Diatomite-Based Scaffolds by Freeze Casting and Polymerization
Chi-Wei Huang 1,Pang-Hsuan Lee 1,Haw-Kai Chang 1,Chih-Hsiang Chang 2,Po-Yu Chen 1
1 Department of Materials Science and Engineering National Tsing Hua University Hsinchu Taiwan,2 Industrial Technology Research Institute, Taiwan Hsinchu TaiwanShow Abstract
Cellular solids are widely applied in various fields due to their lightweight, high surface/volume ratio and energy absorbing ability. Natural foams, such as bird feathers, beaks and bones, possess lightweight and superior mechanical properties due to their anisotropic, hierarchically porous structure. In this study, we synthesized ultra-lightweight, multifunctional scaffolds mimicking natural porous composites by the freeze casting technique utilizing diatomaceous earth (DE) as raw materials. By controlling the cooling rate, sintering condition and the formation of ice dendritic structures, scaffolds with aligned micro-scaled channels and nano-scaled pores were synthesized. Structural characterization was carried out by SEM and the compositional analysis was identified by XRD. Mechanical properties of DE scaffolds were measured by compressive tests and compared with silica scaffolds. Results showed that two scaffolds had similar ultimate compressive stress and elastic modulus yet DE scaffolds have better toughness and deformability. DE scaffolds were further infiltrated by various types of polymers, such as PMMA, PVA, and PDMS, to improve their mechanical properties. The water adsorption, water retention and thermal insulating properties of DE scaffolds were also evaluated. The bio-inspired, hierarchically porous scaffolds can be further applied in various fields.
10:15 AM - SM9.6.05
Bioinspired 3D Printed Hybrid Grippers
Kitty Kumar 1,Jia Liu 1,Caleb Christianson 2,Mustafa Ali 2,Michael Tolley 2,Joanna Aizenberg 3,Donald E. Ingber 1,James Weaver 3,Katia Bertoldi 1
1 Harvard University Cambridge United States,2 University of California, San Diego San Diego United States1 Harvard University Cambridge United States,3 Wyss Institute for Biologically Inspired Engineering Boston United States3 Wyss Institute for Biologically Inspired Engineering Boston United States,1 Harvard University Cambridge United States3 Wyss Institute for Biologically Inspired Engineering Boston United StatesShow Abstract
Hybrid grippers comprising of completely rigid components interfaced with fully flexible soft substrates span out a new set of robots that have benefits of both soft robots and their traditional rigid counterparts. They are compliant and resilient owing to their soft bodies but can also cut and hold solid objects with the fully rigid parts. We design and fabricate a synthetic hybrid gripper based on the design principles of grippers found in nature. We start by studying and optimizing an important component of the gripper design, i.e., the “tooth” for gripping ability and minimum stress at the interface between the fully rigid parts and completely soft substrate under shear and compressive loading conditions, both experimentally and via computer simulations. To validate the design, we incorporate the optimized tooth into the synthetic gripper and demonstrate its ability to apply localized force to grasp or crush solid objects using pneumatic actuation without any visible permanent damage under mechanical loading.
10:30 AM - SM9.6.06
Radially Aligned and Concentric Freeze Casting Inspired by the Porcupine Fish Spine
Frances Su 1,Joyce Mok 1,Joanna McKittrick 1
1 University of California San Diego La Jolla United States,Show Abstract
Porcupine fish dermal spines must be rigid and tough enough to prevent predators from breaking the spines and ingesting the fish. The spines are composed of radially aligned mineral pillars embedded in a protein matrix. Radial alignment has been shown to increase material strength when loaded in the direction of alignment. The spines also have a concentric structure that is similar to that of tree trunk growth rings. In addition to the porcupine fish, many other biological organisms also have tissue with concentric ring structures, including horse hoof tubules and human bone lacunae. This concentric ring structure likely helps with crack deflection to absorb more energy for impact resistance. For this project, a bioinspired ceramic scaffold was created using novel freeze casting techniques to create a structure with both concentric and radial patterns. Mechanical properties such as compressive strength and elastic modulus of the scaffold were compared with mechanical properties of unidirectional freeze casted scaffolds and scaffolds with radial alignment. This work is supported by funding provided by the Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).
10:45 AM - SM9.6.07
Direct Correlation of Single Molecule Properties with Bulk Mechanical Performance for Biomimetic Design of Advanced Polymers
Zhibin Guan 1
1 Univ of California-Irvine Irvine United States,Show Abstract
For rational design of advanced polymeric materials, it is critical to establish a clear mechanistic link between the molecular structure of a polymer and the emergent mechanical properties in bulk. Despite significant progress made towards this goal, it remains a major challenge to directly correlate the bulk mechanical performance of solid polymers to the nanomechanical properties of individual constituent macromolecules. In this study, we show a direct correlation between the single molecule nanomechanical properties of a biomimetic modular polymer and the mechanical characteristics of the resulting bulk material (Nature Materials 2014, 13, 1055). The multi-cyclic single molecule force spectroscopy (SMFS) data enabled quantitative analysis of the asymmetric potential energy profile of individual module rupture and re-folding, in which a steep dissociative pathway accounted for the high yield stress and ductile behavior, while a shallow associative well explained the energy-dissipative hysteresis in cyclic tensile measurements. These results demonstrate a direct correlation of SMFS with the final bulk material properties, allowing SMFS to serve as a guide for future rational design of advanced multifunctional polymeric materials.
11:30 AM - *SM9.6.08
Biomineral-Inspired Composites Based on Calcium Carbonates with Organic Molecular Templates
Takashi Kato 1
1 Univ of Tokyo Tokyo Japan,Show Abstract
Biomineralization is the preparation of inorganic/organic composites by living organisms. Several minerals such as calcium carbonate, hydroxyapatite, silicate, and iron oxide have been used for their components. Biomineralization has recently received much attention from materials scientists. We have reported a variety of crystalline and amorphous calcium carbonate-based composite materials with organic molecular templates obtained in mild conditions.[1-3] Our strategy is to control hierarchical and ordered structures for bioinspired composites to obtain highly functional and high performance materials. Here we report on our recent approaches to biomineral-inspired composite materials: (i) helically ordered structures based on cholesteric liquid-crystalline chitin templates ; (ii) transparent thin-film composites based on cellulose nanofibers and amorphous calcium carbonate ; (iii) ordered composites composed of aragonite nanorods . We also describe our recent approaches to the development of calcium carbonate nanorods exhibiting liquid crystalline properties. These new inorganic colloidal liquid crystals show ordered assembled structures with anisotropic properties.
 T. Kato, T. Sakamoto, and T. Nishimura, MRS Bull., 35, 127 (2010).
 T. Kato, A. Sugawara, and N. Hosoda, Adv. Mater., 14, 869 (2002).
 A. Arakaki, K. Shimizu, M. Oda, T. Sakamoto, T. Nishimura, and T. Kato, Org. Biomol. Chem., 13, 974 (2015).
 S. Matsumura, S. Kajiyama, T. Nishimura, and T. Kato, Small, 11, 5127 (2015).
 T. Saito, Y. Oaki, T. Nishimura, A. Isogai, and T. Kato, Mater. Horiz., 1, 321 (2014).
 S. Kajiyama, T. Nishimura, T. Sakamoto, and T. Kato, Small, 10, 1634 (2014).
 M. Nakayama, S. Kajiyama, T. Nishimura, and T. Kato, Chem. Sci., 6, 6230 (2015).
12:00 PM - SM9.6.09
Mechanical Properties of Porcine Cortical Bone and Bioinspired Bone: Verification of the Interpenetrating Composite Structure of Bone
Frances Su 1,Yik Tung Ling 2,Peter Shyu 2,Michael Tolley 1,Iwona Jasiuk 2,Joanna McKittrick 1
1 University of California San Diego La Jolla United States,2 University of Illinois at Urbana-Champaign Champaign United StatesShow Abstract
Bone is composed of biopolymers (collagen and non-collagenous proteins) and biogenic hydroxyapatite. However, there is debate as to the structure of bone on the nanostructural level. While the bone has been previously thought to be composed of mineral particles suspended in a biopolymer matrix, it is hypothesized here that the biopolymers and mineral in bone actually form an interpenetrating composite. Mechanical properties, such as ultimate compressive strength and elastic modulus of demineralized, deproteinized, and untreated porcine femoral bone at different levels of maturity were compared. Bioinspired composite materials based on the interpenetrating composite model were created. First, a micro-computed tomography was used to obtain a 3-D reconstruction of the bone. Then, the bone model was 3-D printed and tested for its mechanical properties and compared to the model with suspended mineral particles, which was created using computer-aided design software and 3-D printing. This research is supported by the National Science Foundation (DMR-1507978).
12:15 PM - SM9.6.10
Epitaxial Growth of Vertically Aligned Piezoelectric Diphenylalanine Peptide Microrods with Uniform Polarization
Vu Nguyen 1,Kory Jenkins 1,Rusen Yang 1
1 Univ of Minnesota Minneapolis United States,Show Abstract
Energy harvesting with piezoelectric nanomaterials spurred the development of self-powered nanosystems, and piezoelectric biomaterials are expected to play an important role in the biomedical field. Bio-inspired piezoelectric diphenylalanine (FF) peptide microstructures were fabricated on various substrates through a novel epitaxial growth approach. The low-temperature process produced vertically aligned FF peptide microrods with hexagonally arranged nanochannels and uniform polarization. Direct measurement of the piezoelectricity was achieved for the first time from a solid FF peptide single crystal and yielded an effective piezoelectric coefficient at 9.9 pm/V. The dense and aligned FF peptide microrods are advantageous for energy and sensing applications.
12:30 PM - SM9.6.11
Bio-Inspired Solar Energy Materials from Structural Design Principles
Han Zhou 1,Runyu Yan 1,Tongxiang Fan 1,Di Zhang 1
1 Shanghai Jiaotong Univ Shanghai China,Show Abstract
Materials found in nature combine many inspiring properties. A notable feature of natural systems is that they exhibit highly organized hierarchical structures from the nano- to the macrometer scale. Many of these hierarchical structures are barely attainable by man-made materials. Thus, inspiration from nature’s repertoire to organize and assemble materials or biomimic nature’s elaborate architectures to construct complicated structures with related functions has brought about a promising area of bio-inspired materials.
Natural leaves have demonstrated the perfect assembly of hierarchical levels of porosity into 3D elaborated architectures with high porosity, high connectivity and high surface areas for efficient mass flow including gas exchange and water transportation. Furthermore, the whole architecture of natural leaves strongly favors light harvesting. We demonstrate a design strategy for a promising 3D artificial photosynthetic system architecture as an efficient mass flow/light harvesting network relying on the morphological replacement of a concept prototype-leaf’s 3D architecture into perovskite titanates for CO2 photoreduction into hydrocarbon fuels. The process uses artificial sunlight as the energy source, water as an electron donor and CO2 as the carbon source, mimicking what real leaves do.
We report a promising photocatalytic system with both desirable morphology and suitable band-gap configuration for efficient water splitting. Such photocatalyst is realized by the inspiration from leaf’s morphology and Z scheme reaction. The hierarchical macro/mesoporous morphology of natural leaves are retained to enhance overall light harvesting. The CdS/Au/N-TiO2 heterostructures are served as a prototype here to demonstrate this concept, in which N-TiO2 and CdS serve as PS II and PS I, respectively, while Au acts as the electron transfer mediator.
we report the demonstration of a new strategy, based on adopting nature’s NIR light responsive architectures, for an efficient far red-to-NIR plasmonic hybrid photocatalytic system. The system is constructed by controlled assembly of light-harvesting plasmonic nanoantennas (gold nanorods) on a typical photocatalytic unit having butterfly wings’ 3D architectures. Experiments and FDTD simulations demonstrate the structural effects on obvious far red-to-NIR photocatalysis enhancement which originates from the synergetic effects of (1) Enhancing far red-to-NIR light harvesting ability, up to 25%. (2) Enhancing electric-field amplitude of localized surface plasmon to more than 3.5 times than that of the non-structured one.
 H. Zhou, T. X. Fan, D. Zhang, ChemSusChem, 2011, 4, 1344-1387.
 H. Zhou, X. F. Li, T. X. Fan, F. E. Osterloh, D. Zhang, Advanced Materials, 2010, 22, 951-956.
 H. Zhou, T. X. Fan, D. Zhang, J. H. Ye, Scientific Reports, 2013, 3, 1667.
 H. Zhou, T. X. Fan, D. Zhang, Applied Catalysis B: Environmental, 2014, 147, 221-228.
12:45 PM - SM9.6.12
Synthesis of Nanostructured Electrocatalysts through CaCO3 Mineralization
Jong Wan Ko 1,Chan Beum Park 1
1 KAIST Daejeon Korea (the Republic of),Show Abstract
In biomineralization, ordered assemblies of macromolecules such as peptides and polysaccharides are considered to concentrate mineral ions, and initiate spontaneous nucleation and oriented growth of inorganic materials. Macromolecules stabilize amorphous phase minerals which can be transformed to diverse crystalline phases, even in an extremely low level of supersaturation. In producing new mollusk shell grooves, thin organic layer called periostracum is considered to be responsible for initiating CaCO3 mineralization. Periostracum is proteinaceous layer which exists at outer surface of shell and mainly consist of DOPA (3,4-dihydoxyphenylalanine) with a minor amount of chitin. Polydopamine (PDA) has been known as a biomimetic adhesive inspired from mussel foot proteins containing high content of DOPA. Since the universal adhesive properties of PDA were reported, there have been many researches on promising applications in biomedicine, energy harvesting, water treatment and sensors. Catechol groups in PDA have been also known as a redox active ligand which can chelate multivalent cations (Ti4+, Fe2+/3+, Zn2+ and Cu2+), and are suitable for electrochemical applications such as Li-ion batteries, photocatalysts and capacitors. Herein, we demonstrate that PDA, one of the derivatives of quinone-tanned protein, is used as a biomimetic organic mediator for CaCO3 mineralization. In addition to this, the resulting CaCO3 could serve as a novel sacrificial template for synthesis of nanostructured electrocatalysts. As an example, we demonstrate the development of cobalt based electrocatalysts and their superior catalytic performances.
Cobalt base electrocatalysts have been intensively studied for water oxidation with diverse forms such as cobalt hydroxide, cobalt oxides, cobalt oxyhydroxide and cobalt phosphate (CoPi) due to catalytic efficiency and earth abundance. However, cobalt based electrocatalysts have critical issues for performance stability and durability, and these issues are necessary to be improved for efficient and stable water oxidation system. In our present work, we report novel synthesis of nanostructured cobalt based electrocatalysts (i.e., CoPi, cobalt carbonate) from CaCO3 mineralization for stable and improved water oxidation reaction.
Our paper related to this presentation
J. W. Ko, C. B. Park, Manuscript in preaparation
F. Nudelman, H. H. Chen, H. A. Goldberg, S. Weiner, and L. Addadi, Faraday discussions 136, 9-25 (2007)
J. R. Young, S. A. Davis, P. R. Bown, S. Mann, Journal of structural biology 126, 195-215 (1999)
P. J. Smeets, K. R. Cho, R. G. Kempen, N. A. Sommerdijk, J. J. De Yoreo, Nature materials 14, 394-399 (2015)
Y. Liu, K. Ai, L. Lu, Chemical Reviews 114, 5057-5115 (2014)
SM9.7: Synthesis and Characterization I
Thursday PM, March 31, 2016
PCC North, 200 Level, Room 229 B
2:30 PM - *SM9.7.01
Structure and Mechanical Properties of Bio-Related Materials
Oden Warren 1
1 Hysitron, Inc. Minneapolis United States,Show Abstract
This presentation will focus on examining the relationships between structure and mechanical properties of biological materials and biomaterials, as well as of engineered materials and structures that have been inspired by biology. Although no simple statement can adequately describe the full range of structure in biological materials, there does exist a prevalent theme that biological materials tend to be hierarchical in their construction. When that is indeed the case, the natural comparison to make to materials science is to composite and interface engineering, a field that emphasizes feature recognition, site specificity, and the ability to span multiple length scales as important aspects of mechanical property measurements. Bio-relevant mechanical testing, however, can involve all of those aspects plus additional complexities such as high sensitivity of the sample to environmental conditions, an enormous range of possible elastic moduli, and time-dependent behavior (e.g., viscoelasticity or poroelasticity) too dominant to be ignored. This presentation will address using nanoindenter-based techniques that are commonplace in the materials science community to investigate biological materials, biomaterials, and biomimetic materials with the intent to elucidate structure-mechanical property correlations. However, numerous improvements have been made recently to bioindenter instruments deploying nanoindenter-based techniques, for example, better ways of mitigating the influence of the fluid in which the sample is immersed. Additionally, there has been considerable progress in recent years in extending nanoindenter-based techniques to the various “in-” modes of operation such as in-situ, in-vitro, in-vivo, and in-operando. The latest technologies and techniques will be described, and several research examples will be given. Finally, the prospect of meaningful in-situ mechanical tests in electron microscopes on bio-related samples will be discussed.
3:00 PM - SM9.7.02
Multiscale Characterization of Biomimetic Materials with Structural Hierarchy
Eric Meshot 1,Edgar Dimitrov 2,Thomas Riis 2,Ngoc Bui 1,KuangJen Wu 1,Francesco Fornasiero 1
1 Lawrence Livermore National Lab Livermore United States,2 University of California at Berkeley Berkeley United StatesShow Abstract
Superior mechanical properties of natural, hierarchical materials have motivated research in developing synthetic materials with biomimetic structures. Carbon nanotubes (CNTs) are a promising synthetic analog to structural biomolecules like collagen, because individual CNTs boast exceptional mechanical properties (100-GPa strength, 1-TPa stiffness), form packed bundles analogous to collagen microfibrils, and can be assembled into more complex 1D (fiber, yarn), 2D (sheet) [1, 2], and 3D (foam, scaffold)  structures. The hierarchical organization of these CNT materials is reminiscent of that of collagen fibers in diverse tissues like tendons and ligaments (1D), skin (2D), and vitreous (3D).
Unfortunately, despite advances in design and processing of bioinspired CNT materials, their macroscale properties have fallen short from those of both individual CNT building blocks as well as their biological counterparts, likely due to inefficient load transfer between hierarchical levels. Drawing structure-property relationships across length scales for hierarchical CNT materials is critical to guide the rational design of their multiscale organization toward resolving these shortcomings, but probing structural characteristics across orders-of-magnitude differences in length scale is challenging.
To address this need, we have developed advanced metrology to map size and order in hierarchically organized, 1D nanostructures spanning four orders of magnitude in length scale – atomic, nano, meso, micro. Using a suite of novel soft and hard X-ray scattering beamlines at the Advanced Light Source (ALS) and Linac Coherent Light Source (LCLS), we quantitatively mapped structural characteristics in self-aligned, anisotropic CNT forests grown by chemical vapor deposition, both spatially within the CNT material and across several length scales (0.1-1000 nm).
Furthermore, we developed a unified analytical model to quantitatively describe the structural hierarchy of aligned CNTs and to extract key structural parameters via curve-fitting of our X-ray scattering data. From the bottom up, our model parameters define the graphitic lattice and wall number (atomic), CNT diameter (nano), CNT bundling and spacing (meso), regular corrugations (micro), and number density (macro), and comparison with electron microscopy reveals good agreement for forests with a wide range of characteristics (e.g., 1-11 walls, 1.5-15 nm diameter, 1010-1012 cm-2 density). Finally, we offer insights into how our methodology and results can inform existing mechanical models and advance hierarchical CNT materials design to match not only the structure but also the properties of biological materials.
This work was performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
1. E.R. Meshot et al. Adv Func Mater 22, 577, 2012.
2. F. Fornasiero et al. Carbon, in revision.
3. R. Thevamaran, E.R. Meshot, C. Daraio. Carbon 84, 390, 2015.
3:15 PM - SM9.7.03
Characterization of Silk Fiber-Reinforced Polyesters Synthesized by Bees in the Colletidae Family
Christine Dimke 1,Debbie Chachra 1
1 Materials Science Olin College Needham United States,Show Abstract
A subfamily of ground-nesting bees, Colletes, have been observed to make a cellophane-like nest cell lining. This lining protects the egg and the associated provisions (primarily pollen and nectar) from parasites, fungi, and pathogens while the egg hatches into a larva and then develops into an adult bee. Hefetz et al. demonstrated  that the cell lining of Colletes thoracicus was made of a polyester (leading to the nickname of ‘polyester bees’).
We continued this work by investigating Colletes inaequalis, which is endemic to the northeast United States. Our earlier work indicated that the nest cell linings were stable to ~72°C (by differential scanning calorimetry.) They are resistant to degradation, insoluble in many compounds such as ethanol, isopropyl alcohol, and methylene chloride. This is consistent with their ecological role (remaining intact while buried in many months, over a wide range of temperatures), and adds to the interest in this bee polyester as an exemplar of a bioderived, biodegradable polymer that is nonetheless displays good thermal and chemical resistance.
Scanning electron microscopy of the nest cell linings revealed the presence of multiple layers, as well as fibers. Fourier-transform infrared spectroscopy of the fibers suggested that they were proteinaceous; this was confirmed by confocal microscopy of nest cell linings stained with a protein-specific stain (KRYPTON, Thermo Scientific, Rockford, IL) which resulted in clear visualization of the fibers, distinct from the polyester background. Amino acid analysis of the nest cell linings indicates that the protein component is consistent with silk. The presence of silk fibers was also observed in another Colletes species, halophilus . The fibers of both species were located on the outside of the nest cell linings, suggesting that they were synthesized by the adult bee (not the larva), and tha they likely play a role in the construction of the nest cell lining by serving as a scaffold over which the polyester component (derived from macrocyclic lactones in the Dufour’s gland) is ‘painted’ by the bee, using their characteristic bilobed glossa (tongue). The nest cell lining therefore appears to be a silk fiber-reinforced polyester composite.
We are extending this work to the parent family of Colletes, Colletidae, with nest cell linings from species from four of the five subfamilies: Colletes, Hylaeus, Xeromessilinae, and Diphaglossinae (sourcing of nest cell linings from the fifth subfamily, Euryglossinae, is in progress). Preliminary optical microscopy suggests that fibers are present in nest cell linings from all four Colletidae species; confocal and scanning electron microscopy is in progress, to be followed by amino acid analysis and other chemical analyses to investigate how widespread the silk-reinforced polyester is in the family Colletidae.
1. A Hefetz et al., Science 204:415-7 (1979)
2. R Belisle et al., Journal of Material Science (2001)
3:30 PM - SM9.7.04
An Aqueous Solvation Method for Recombinant Spider Silks: More than Just Fibers
Justin Jones 1
1 Biology Utah State University Logan United States,Show Abstract
Spider silk is a striking and robust natural material that has an unrivaled combination of strength and elasticity. There are two major problems in creating materials from recombinant spider silk proteins (rSSp): expressing sufficient quantities of the large, highly repetitive proteins and solvating the naturally self-assembling proteins once produced. To address the second problem, we have developed a method to rapidly dissolve rSSp in water in place of harsh organic solvents and accomplish nearly 100% solvation and recovery of the protein. Our method involves generating pressure and temperature in a sealed vial by using repetitive 5 second bursts from a countertop microwave. From these easily generated aqueous solutions of rSSp, a wide variety of materials have been produced. Production of fibers, films, hydrogels, lyogels, sponges, and adhesives are now possible and we have studied their mechanical abilities and structural components. This solvation method allows a choice of the physical form of product to take advantage of spider silks’ mechanical properties without using costly and problematic organic solvents. To our knowledge, our aqueous solvation technique is the only method that is cost-effective and will scale to industrial levels to solubilize rSSp.
3:45 PM - SM9.7.05
Enhancing the Mechanical Properties of Nylon 6,6 Electrospun Yarns by Annealing and Addition of Spider Silk Proteins
Ibrahim Hassounah 1,Ethan Abbott 1,Dan Gil 1,Cameron Copeland 1,Thomas Harris 1,Justin Jones 1,Randolph Lewis 1
1 Biology USTAR BioInnovations Center Logan United States,Show Abstract
Nylons have gained great interest in the industrial field due to their applicability and desired mechanical properties. They possesses extremely strong mechanical properties that are capable of being applied in technical textiles, bullet proof vests, etc. In this research work, the mechanical properties of the electrospun nylon 6,6 is improved by the addition of tiny amounts of the main ambulate spider silk protein (MaSp1). The addition of only 2.5-10 wt.% of MaSp1 leads to an increase in the mechanical properties of electrospun nylon yarns by almost 50%. The mechanical properties of the electrspun yarns are further enhanced by annealing at 120°C for an hour as a postreatment process. Annealing increased the mechanical properties in terms of tensile strength, elastic modulus and ultimate tensile strength while the strain of the yarns is shrank significantly. Dopes of nylon 6,6 and MaSp1 are prepared in formic acid and are electrospun into nanofibers. The formed mats are twisted into yarns, which are characterized by SEM, FTIR, DSC, XRD, and mechanical test measurements. The prepared electrospun nanofibers can be applied in technical textiles, tires, tents, ropes, ponchos, fishing lines and parachutes.
4:30 PM - SM9.7.06
Adhesion of Fibrillar Dry Adhesives on Rough Substrates
Rene Hensel 1,Viktoriia Barreau 2,Animangsu Ghatak 3,Robert McMeeking 5,Eduard Arzt 2
1 INM - Leibniz Institute for New Materials Saarbrücken Germany,1 INM - Leibniz Institute for New Materials Saarbrücken Germany,2 Department of Materials Science and Engineering Saarland University Saarbrücken Germany1 INM - Leibniz Institute for New Materials Saarbrücken Germany,3 Department of Chemical Engineering Indian Institute of Technology Kanpur India1 INM - Leibniz Institute for New Materials Saarbrücken Germany,4 Materials Department and Department of Mechanical Engineering University of California Santa Barbara United States,5 Engineering School University of Aberdeen, King’s College Aberdeen United KingdomShow Abstract
All natural and almost all artificial surfaces have a roughness on one or more different length scales. To date, the adhesion of micropatterned gecko-inspired surfaces has predominantly been tested on hard, smooth substrates. A detailed understanding of the influence of surface roughness is critically important for practical use of such dry adhesives. Toward this aim, the normal adhesion was experimentally studied at a set of rough glass substrates using micropatterned PDMS samples. The results obtained reveal adhesive and non-adhesive states depending on the pillar geometry and the surface roughness profile. Normal adhesion increases with smaller pillar diameter and higher aspect ratio. However, the adhesion undergoes a transition from adhesive to non-adhesive state when the pillar diameter become smaller than the lateral roughness parameter, S, that reflects the mean distance between adjacent peaks of the surface roughness profile. The results obtained unravel the decisive role of pillar dimension of single-level fibrillar dry adhesives with regard to the adhesive characteristics on fibrillar dry adhesives for rough substrates, and explain how to design such mimics, either for adhesive or non-adhesive applications.
4:45 PM - SM9.7.07
Nanoscale Chemical Composition of Biomaterials Using Nano IR Spectroscopy
Curt Marcott 1,Eoghan Dillon 2,Craig Prater 2,Kevin Kjoller 2,Roshan Shetty 2,Alex Dazzi 3
1 Light Light Solutions Seabrook Island United States,2 Anasys Instruments Santa Barbara United States3 Université Paris-Sud Orsay FranceShow Abstract
Infrared (IR) spectroscopy is a powerful tool for obtaining chemical information about materials. Unfortunately, the wavelength of light used to make the measurement limits the size of structures that can be reliably identified by IR spectroscopy. Diffraction typically limits the spatial resolution of IR microspectroscopy to 3-10 µm, making this technique problematic for identifying small structures in samples such as tissue sections and single cells. Atomic force microscopy (AFM), on the other hand, provides exquisite spatial resolution (as small as one nanometer), but this technique does not provide any chemical information. A new technique which combines AFM and IR spectroscopy is described. It is based on the combination of a tunable infrared laser with an atomic force microscope that can locally map and measure thermal expansion of nanoscale regions of a sample resulting from the absorption of infrared radiation. Because the AFM probe tip can map the thermal expansion on very fine length scales, the AFM-IR technique provides a robust way to obtain interpretable IR absorption spectra at spatial resolution scales well below the diffraction limit. Several types of tissue and biomaterials samples, including hair, skin, and bone cross sections have been examined by AFM-IR spectroscopy and imaging. The technique has also been shown to be useful for chemically characterizing structures inside single cells and for identifying secondary structure and orientation of sub-micrometer-diameter protein fibers.
5:00 PM - SM9.7.08
Engineered Elastin-Like Polypeptide Hydrogels with Enhanced Mechanical Tunability
Malav Desai 2,Kyle Joyner 2,Tae Won Chung 2,Eddie Wang 2,Seung-Wuk Lee 2
1 Bioengineering Univ of California-Berkeley Berkeley United States,2 Biological Systems and Engineering Lawrence Berkeley National Laboratory Berkeley United States,Show Abstract
Water swollen networks or hydrogels can be created using a variety of polymers by designing specific chemical and/or physical crosslinks. In this work, we engineered elastin-like polypeptides (ELPs) with bio-derived sequence to create a synthetically simple, highly elastic and resilient hydrogel material. Unlike tissue-derived materials such as collagen and gelatin, recombinantly expressed ELPs are monodispersed and their chemical and physical properties can be precisely tuned via genetic engineering. We designed three ELPs composed of ‘VPGVG’ repeats with molecular weights 21, 31 and 41 kDa. We show that the failure strain increases with larger PBPs to as high as 16 with increasing ELP length. Additionally, we also explore the hydrogel characteristic of incredibly high elastic recovery even at strain as high as 6 and show that the hydrogels composed of the smallest ELPs recover 95% of energy upon relaxation. An advantage of recombinantly expressed polypeptides is that unlike synthetic polymers that tend to be broadly dispersed, PBPs can be used to clearly show how polymer properties such as the friction between chains affects overall hydrogel dynamics. We investigated this phenomenon using the denaturing effects of guanidinium as well as the synergistic effects of a pair of ELPs that from modular hydrogels and combine this knowledge to create a material with tunable mechanical properties.
5:15 PM - SM9.7.09
Observations of a Core-Shell Structure in Single Bioproduced, Biodegradable Electrospun Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) Nanofibers by AFM-IR Spectroscopy and Imaging
John Rabolt 1,Liang Gong 1,D. Bruce Chase 1,Isao Noda 2
1 Univ of Delaware Newark United States,1 Univ of Delaware Newark United States,2 MHG Bainbridge United StatesShow Abstract
The combination of atomic force microscopy (AFM) and infrared (IR) spectroscopy is an extremely powerful tool that can provide topographic information that can be correlated with chemical, conformational and molecular orientation information at a spatial resolution of 50-100 nm. Using an AFM-IR instrument (Anasys Instruments), we have explored the correlation between structure, processing and chain orientation/crystallinity in biodegradable and biocompatible poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) electrospun nanofibers and tested the hypothesis that different processing protocols can alter the concentration of the stable α-crystalline form and the metastable β-crystalline form. The ability to obtain IR spectra at high spatial resolutions has allowed us to probe crystalline populations as a function of nanofiber diameter and as a function of location within the fiber, and we have observed, for the first time, the existence of a core-shell structure in a single electrospun nanofiber. In addition, the spectroscopic imaging capability of the AFM-IR instrument has been utilized to create a map of α and β crystalline content as a function of location within the nanofiber, verifying the existence of a core-shell structure.
5:30 PM - SM9.7.10
Transition Metal Nanoparticles and Quantum Dots with Tunable Electronic Properties by Bacterial Precipitation
Katherine Marusak 1,Yaying Feng 1,Yangxiaolu Cao 1,Stephen Payne 2,Lingchong You 1,Stefan Zauscher 1
1 Duke Univ Durham United States,2 Greenlight Biosciences Medford United StatesShow Abstract
We present a new method for the fabrication of semiconducting, transition metal nanoparticles (NPs) with tunable bandgap and useful photoelectric properties, through bacterial precipitation. Escherichia coli bacteria have been genetically engineered, by overexpression of a cysteine desulfhydrase gene, to precipitate transition metal NPs from solution, here more specifically, cadmium sulfide (CdS). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) revealed that the bacterially precipitated NPs are agglomerates of mostly quantum dots (QDs), with a diameter of 4-5 nm, in a carbon-rich matrix. We discovered that the precipitation conditions of the bacteria can be tuned to produce NPs with bandgaps that range from quantum-confined to bulk CdS. Inducing precipitation at varying stages of bacterial growth allows for control over whether the precipitation occurs intra- or extracellularly. This control is critically important for using the bacterial precipitation system for the environmentally-friendly fabrication of functional nanomaterials. Notably, the measured photoelectrochemical current generated by these particles is comparable to values reported in the literature. This suggests that our bacterially precipitated CdS NPs have potential for applications ranging from photovoltaics to photocatalysis in H2 evolution.
5:45 PM - SM9.7.11
Discovery of β-Form Crystalline Structure in Poly ((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) (PHBHx) Thermoreversible Gel Film
Liang Gong 1,Brian Sobieski 1,D. Bruce Chase 1,Isao Noda 2,John Rabolt 1
1 Materials Science and Engineering University of Delaware Newark United States,1 Materials Science and Engineering University of Delaware Newark United States,2 MHG, Inc Bainbridge United StatesShow Abstract
Poly [(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) (PHBHx) is a new type of bioplastic which is produced by a wide variety of bacteria in plant oils as an intracellular carbon and energy storage media. Compared to its parent homopolymer, Polyhydroxybutyrate (PHB), PHBHx not only inherits the excellent biodegradability and biocompatibility, but also overcomes its stiffness and brittleness by adding a small amount of hydroxyhexanoate (Hx) units with medium-length side chains. These longer side chains would act as defects and interrupt the excessive crystallization of PHB caused by the near perfect stereoregularity, and thus largely improve the processing properties of the copolymer.
Previously we discovered that dilute solutions of PHBHx in 1.4-Dioxane transform to thermoreversible gels when cooling from 100°C to room temperature. During cooling/gelation, crystallites were formed, which physically cross-link the polymer chains when chain entanglement in the solution was sufficiently developed. Freeze-dried PHBHx gel showed a 3-D interconnected nanofibrous network with fiber diameters of 50-500 nm, which resembles the structure of the natural extracellular matrix (ECM). WAXD results showed that the crystal structure of the solid phase in the gel is the most common α-form, with the polymer chains adopting a 21 helical conformation. Surprisingly, when drying the PHBHx gel under ambient conditions, the β-crystalline form, with the polymer chains adopting a planar zig-zag conformation, was found to co-exist with the α-crystalline form in the resultant gel film. The β-form crystalline structure is recognized as a strain-induced paracrystalline structure and so far has only been observed in highly stretched PHBHx electrospun nanofibers . The effects of different parameters, including Hx content, solvent, drying temperature and polymer concentration, on the formation of the β-crystalline structure were investigated in an effort to elucidate the mechanism responsible for the generation of the β-crystalline structure in the gel film. In addition, an advanced characterization technique, AFM-IR, was utilized to investigate the inhomogeneous distribution of the two crystalline structures in the gel film. The discovery that the β-crystalline structure can be formed in PHBHx by simply drying the physical gel under ambient conditions may add to the previous observation that the β-crystalline structure could only be obtained in PHBHx when extra external stretching forces were artificially introduced on the polymer chains during post-processing procedures which involved winding up on a high speed mandrel.
 L. Gong, D. B. Chase, I. Noda, et al. Macromolecules, 2015, 48 (17), pp 6197–6205
SM9.8: Poster Session III: Synthesis and Characterization—Biomaterials for Medical Applications
Friday AM, April 01, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM9.8.01
Turn-On Fluorescence/MRI Platform for Tumor Cell Bimodal Imaging via MnO2 Nanotube
Qian Lu 2,Yang Song 1,He Li 1,Chengzhou Zhu 1,Dan Du 1,Songqin Liu 2,Yuehe Lin 1
1 School of Mechanical and Material Engineering Washington State University Pullman United States,2 School of Chemistry and Chemical Engineering Southeast University Nanjing China,1 School of Mechanical and Material Engineering Washington State University Pullman United States2 School of Chemistry and Chemical Engineering Southeast University Nanjing ChinaShow Abstract
Herein, a manganese dioxide (MnO2) nanotube was successfully synthesized by one-step route. Due to its similar properties with carbon nanotube, the MnO2 nanotube could be used as a fluorescence quenc