Biological Materials Science: Biological Materials Science Student Poster Contest
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Biomaterials Committee
Program Organizers: Po-Yu Chen, National Tsing Hua University; Francois Barthelat, McGill University; Michael Porter, Clemson University; Steven Naleway, University of Utah

Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr

H-19: Aligned Carbon Nanotubes Reinforced Electrospun Polymeric Scaffold for Peripheral Nerve Repair: Pallavi Gupta1; Murali Kumaraswamy1; Partha Roy1; Debrupa Lahiri1; 1IIT
    Carbon nanotubes (CNTs), due to their unique electrical properties, have potential to the repair the neural injuries. This study demonstrates the in vitro and in vivo efficacy of CNT-reinforced aligned polymer electrospun nanofibrous scaffold in the repair and regeneration of transected nerve. The in vitro study confirmed the HT-22 hippocampal neurites orientation in the direction along the aligned CNT–polymer scaffold and also that the CNT alignment increases the maximal neurite length significantly. The electrospun scaffolds were also characterized for their tensile strength and electrical conductivity. Four weeks after implantation of an aligned CNT–polymer nerve conduit into the 15 mm gap of a transected rat sciatic nerve, show that the scaffold had supported robust neural regeneration across the gap. Thus, the results strongly support the potential use of aligned CNT-reinforced polymer nanofibrous scaffolds as the interface between the nerve conduit and peripheral neural tissues.

H-20: Bioinspired by Porcupine Quills: Freeze Cast Porous Scaffolds Strengthened by Shrink Wrap and Infiltration with Biodegradable Materials: Michael Frank1; Ali Ismail1; Louis Guibert2; Jerry Ng1; Joyce Mok1; Cindy Ayala1; Sze Hei Siu1; Joanna McKittrick1; 1UC San Diego; 2École Polytechnique de l'Université de Nantes
    Porcupine quills are lightweight, keratinous biological materials that have a cortex sheath wrapped around a closed-cell foam. The quills can withstand large compression and flexure loads primarily due to the cortex layer. Freeze casting uses directional freezing of water to generate strengthened porous scaffolds along the ice growth axis, however, scaffolds are much weaker along the transverse axis. Biocompatible and biodegradable materials that can strengthen the composite structure include polylactic acid film (≈ 50 µm) shrink wrapped around the scaffold and polyethylene glycol gel infiltrated within the pores. The Brazilian Test method was used to measure splitting tensile strength along the scaffold transverse axis. Future avenues for research exploration may be in combination with extrinsic methods such as magnetic field assisted freeze casting. This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009) and by a National Science Foundation, Biomaterials Grant 1507978.

H-21: Bone Remodeling under Tooth Loading: Kangning Su1; Jing Du1; Li Yuan2; 1Pennsylvania State University; 2Shenzhen People's Hospital, 2nd Clinical Medical College of Jinan University
    The stability and success rate of orthopedic and dental implants are affected by their surrounding bone quality. Bone adapts to mechanical loads through remodeling activities to achieve new equilibrium in strain/stress state. The object of this study is to develop a numerical algorithm to simulate bone remodeling activities under mechanical loading. Finite element method is used to calculate the strain/stress distribution in the alveolar bone under toothloading. The bone density remains unchanged near the equilibrium point of the mechanical stimulus; under greater or smaller mechanical stimulus, it increases or decreases. Iterations are performed to simulate the evolution of bone density. Effects of model geometry and adjacent teeth are studied. Effects of various applied loads and boundary conditions are compared. Simulation results are validated using computed tomography (CT) data of human mandibles. The implications of the results on patient-specific treatment and the insights for clinical techniques are also discussed.

H-22: Design and Analysis of Beetle Wings Inspired Foldable Materials by the Origami Approach: Chi-Huan Tung1; Cheng-Chun Shih1; Po-Yu Chen1; 1National Tsing Hua University
    Beetles (Coleoptera) are known for the ability to fold their hind wings beneath the stiff protective elytra and unfold them immediately. These foldable hind wings have several significant properties that can be explained by analogizing its structure by origami models. This study reveals the relationship between folding-unfolding behavior and the mountain-valley fold creases distributing on the wings. The orientation of micro-pleats on the wing is determined by the order parameter which can be related to mechanical properties of different parts of the wings. We examine the origami properties: flat foldability, folding directions and vertex concavity of single vertex crease pattern, then compare these structures with some commonly used origami model. The hing wings are templated by PDMS, which then tested in tension to determine their fold-unfold trait. These features can be used to improve the design of bio-inspired materials and produce space efficient products with decent mechanical properties.

H-23: Development of 3D Template Freeze Casted Hydroxyapatite/Magnesium Alloy Biodegradable Implants: Yajur Maker1; Jae-Young Jung1; Kathryn Kang1; Michael Frank1; Joanna McKittrick1; 1UC San Diego
    Resorbable bone implant materials have been actively researched and developed for use in biomedical applications. One such biocompatible material is hydroxyapatite (HA), which provides exceptional osteoconductivity, but significantly lacks mechanical strength under freeze casting preparation. To compensate for the lack of mechanical strength we have proposed a new freeze casted HA scaffold encased inside a magnesium (Mg) alloy shell which safely biodegrades within the body. In this process three novel concepts are being explored: (1) the use of a new biocompatible Mg alloy that is shown to have a degradation rate similar to bone growth, (2) the fabrication of bone-like HA scaffolds with enhanced processing control of the macro/micro porosity using a 3D template, and (3) the preparation of the Mg alloy encasing the HA scaffold, in order to combine the positive characteristics of the two materials (Mg alloy’s strength and HA’s osteoconductivity) in forming a comprehensive biodegradable implant.

H-24: Image Processing Techniques for Testing of Soft Materials: an Example with Tensile Deformation of Pig Skin: Andrei Pissarenko1; 1UC San Diego
    Mammal skin is a biological material that exhibits a range of very interesting mechanical properties in order to resist loadings of various kinds, dynamics and intensity. Hence, our motivation is to extend our understanding of its behaviour and structural arrangement to gain a better understanding of processes such as wound healing. In our study, mechanical tests on samples of pig skin were ran - the pig skin being chosen for sharing a significant amount of features with human skin. Besides the data collected from the testing machine, we acquired high speed videos of the tested samples. This was done in order to perform image processing for 2D displacement and strain mapping, and to potentially compensate for the slipping of samples between grips. The presented work will discuss a range a Image Processing techniques that can be applied to map large displacements in 2D an assess anisotropy of a given material.

H-25: Mammal Horns as Natural Weapons: Yuchen Zhang1; 1UCSD
    Ruminant mammals use their horns for both defense from predators and intraspecific combat. Convergent evolution of horn materials and structures has been inferred in the families Bovidae and Antilocapridae. To investigate the composition and microstructure of horn sheaths, four representative species were examined (bighorn sheep, domestic sheep, mountain goat, and pronghorn antelope). Bighorn sheep and domestic sheep are from the same genus but have different impact fighting energy. The mountain goat, from the same family as the sheep (Bovidae), presents much lower impact fighting behavior. Pronghorn antelope, from a different family (Antilocapridae) also does not employ high impact ramming in intraspecific fights in contrast to the two sheep. Optical microscopy images show that the horns of all four species consist of keratin sheath formed by lamellar keratinized cells but differ in tubule densities and porosities. Mechanical tests results in the dry and hydrated conditions will be presented. This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).

H-26: Microstructural Origins of the Dynamic Behavior of Wood and Bioinspired Designs: Albert Matsushita1; Damian Gonzalez1; Michael Frank1; Jae-Young Jung1; Joanna McKittrick1; 1University of California, San Diego
    Sporting goods and historic weapons make ubiquitous use of impact resistant timbers, yet the microstructural origins of wood dynamic behavior are poorly understood. Drop weight testing was conducted on wood samples to determine how fracture toughness and failure mode scale with impact energy and strain rate. The different damage progressions of each wood were compared to the unique anatomy of their ray cells, vessels, fiber zones, and parenchyma. In addition, ceramic bio-templated structures using pyrolyzed timber were similarly tested to isolate geometrical effects and assess possible improvements to dynamic specific toughness over traditional cellular structures. These results provide new insight into the dynamic behavior of wood and how their microstructures may be replicated to improve the impact resistance of synthetic materials. This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).

H-27: Porous 45S5 Bioglass®-based Scaffolds Using Stereolithography: Effect of Partial Pre-sintering on Structural and Mechanical Properties of Scaffolds: Boonlom Thavornyutikarn1; Terence Turney1; Passakorn Tesavibul2; Kriskrai Sitthiiseripratip2; Nattapon Chatarapanich3; Bryce Frltis4; 1Monash University; 2National Metal and Materials Technology Center; 3Kasetsart University; 4RMIT University
    Scaffolds made from 45S5-Bioglass (BG) show clinical potential in bone regeneration due to their excellent bioactivity and ability to bond to natural bone tissue. However, porous BG scaffolds are limited by their mechanical integrity and by the substantial volume contractions occurring upon sintering. This study examines stereolithographic (SLA) methods to fabricate mechanically robust and porous Bioglass-based scaffolds, with regular and interconnected pore networks and with various computer-aided design architectures. It was found that a diamond-like (DM) architecture gave scaffolds the most controllable results without any observable closed porosity in the final scaffolds. When the pore dimensions of the DM scaffolds of the same porosity (~60 vol%) were decreased from 700 to 400 μm, the compressive strength increased from 3.5 to 6.7 MPa. Additionally, smaller dimensional shrinkage could be obtained by employing partially pre-sintered bioglass, compared to standard 45S5 Bioglass. Scaffolds derived from pre-sintered bioglass also showed marginally improved compressive strengths.

H-28: Production of Zinc-Magnesium Alloy Wires by Thermal Drawing for Pediatric Bioabsorbable Stent Applications: Injoo Hwang1; Daniel S. Levi2; Xiaochun Li1; 1Department of Mechanical and Aerospace Engineering, University of California, Los Angeles; 2Division of Pediatric Cardiology, Mattel Children’s Hospital, University of California Los Angeles
    Non-absorbable metallic stents are commonly used in pediatric pulmonary artery and coarctation stenting to assist revascularization and to prevent potential restenosis. As conventional stents are quickly “outgrown” by pediatric patients, there remains a need for a pediatric resorbable stent. A stent made from a material with the ideal mechanical properties, biocompatibility and corrosion rate would be of huge benefit to thousands of children with congenital heart disease. In this study, micro Zn-Mg wires were characterized in terms of mechanical properties by tensile testing and micro/nano-hardness testing and biodegradability by in vitro corrosion in a pseudo-physiological solution. The experimental results suggest that this novel material could have the ideal strength, ductility and resorption for stent applications.

H-29: Structure-property Quantification for the Bio-inspiration of the Great White (Carcharodon carcharias) and the Tiger (Galeocerdo cuvier) Shark’s Teeth: John Wood1; Hongjoo Rhee2; A. C. McIntosh1; R. D. Moser3; M. Horstemeyer1; R. Prabhu1; 1Mississippi State University; 2Center for Advanced Vehicular Systems; 3U.S. Army Engineer Research and Development Center
    In this study, the teeth of the Great White (Carcharodon carcharias) and the Tiger (Galeocerdo cuvier) sharks are analyzed to find their structure-property relationships for optimized shearing and bite force. Towards this extent, the teeth’s chemical composition, density, material variations, geometric optimization, and the potential reduction in shearing forces when penetrating materials are evaluated. The structure-property analysis was conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and optical microscopy in order to study the teeth’s hierarchical optimization. The structural property quantification also focused on the serrated edges of the teeth, which were captured in SEM and micrographs and were analyzed using ImageJ software. Macro- and nano-indentation will also be performed to determine the material’s hierarchy in optimizing the mechanical properties for ideal shearing and bite force. Further research will hopefully find a biological optimization for serration size, shape, and material.

H-30: Structure and Mechanical Behavior of Human Hair: Yang Yu1; Wen Yang1; Bin Wang1; Marc Meyers1; 1University of California, San Diego
    In this current study, we showed the structure and surface morphology of human hair with scanning electron microscopy. The effects of strain rate, relative humidity and temperature are investigated comprehensively, and the results show that the hair exhibits a changed tensile property under these influences. The elasticity and plasticity of hair after stretching to different strains are shown with cyclic tests. Finally, a constitutive equation is proposed based on the two-phase model and the experimental results. This model is considered to help to understand and analyze tensile behaviors of similar α-keratin fibers under certain conditions. Therefore, it is hoped that this study will be helpful in not only providing guidance in designing better cosmetic products, but also broadening our knowledge in the keratinous materials, which include wool, nail, horn and feathers.

H-31: Structure and Mechanical Implications of the Pectoral Fin Skeleton in Longnose Skates: Wei Huang1; Vlado Lubarda1; Watcharapong Hongjamrassilp1; Jae-Young Jung1; Phil Hastings1; Joanna McKittrick1; 1University of California, San Diego
    Animal propulsion systems are believed to show high energy and mechanical efficiency in assisting movement compared to artificial designs. The longnose skate (Raja rhina), one of the representative examples, shows an elegant undulatory swimming facilitated by its wing-like pectoral fins. The aim of this work is to illustrate the hierarchical structure of the pectoral fin of the longnose skate and explain the mechanical implications of the structural designs by nature. Micro-computed tomography images indicated that the pectoral fins comprise radially oriented fin rays, formed by staggered mineralized skeletal elements stacked end-to-end. Each skeletal element is composed of three tesserae chains, which consist of discrete segments of mineralized tesserae wrapped with unmineralized cartilage. A numerical model based on the morphological data was created to demonstrate how the specific structure affects certain mechanical behaviors. This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009).

H-32: Study of Formation of Passivating Oxides in Thin Films of Ti-Nb for Biomedical Applications: Ernesto Gonzalez Cruz1; Pedro Nascente1; Patricia Sato1; 1Universidade Federal de Sao Carlos
    The study of growth passive layers under atmospheric conditions as well as corrosion resistance materials for orthopedic implants is of great importance, not only because it determines the lifetime of the device, but also because of the harmfulness of corrosion processes occurring in the living organism. In this study, thin films of Ti-Nb were deposited on a stainless steel substrate by sputtering technique and characterized by XPS where besides the exploratory spectrum was obtained also the spectra of high-resolution C 1s, O 1s, Ti 2p and Nb 3d, and polarization curves in biological solutions. The results showed that the atmosphere has an effect in thin films, showing the growth of oxide layers from metal constituents of mainly titanium oxide and to a lesser extent, niobium oxides; Furthermore they showed large areas of passivation and showed no signs of pitting formation in the range of the potential characteristic of the body.

H-33: Surface Magnetized Hydroxyapatite for Multi-Axis Strengthened Bone Implants with Magnetic Freeze Casting: Michael Frank1; Cindy Ayala1; Louis Guibert2; Keyur Karandikar1; Chin-Hung Liu1; Sze Hei Siu1; Olivia Graeve1; Joanna McKittrick1; 1UC San Diego; 2École Polytechnique de l'Université de Nantes
    Degradation of the interior spongy bone layer due to erosion of the hard mineral phase can lead to bone brittleness over time. Preventative surgery to reinforce bone with titanium implants may be too strong, require follow-up surgeries and provide an insufficient 3D matrix for osteoblast integration. Surface magnetization of hydroxyapatite was first achieved by electrostatically pairing superparamagnetic particles from cationic charged ferrofluid with oppositely charged hydroxyapatite in water. Magnetized hydroxyapatite particles were then manipulated by a static magnetic field during magnetic freeze casting. Directional ice crystal growth segregated particles and a low magnetic field aligned their orientation to produce multi-axis strengthened porous scaffolds. Potential future applications for these porous scaffolds include serving as load bearing bone implants. This work is supported by a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009) and by a National Science Foundation, Biomaterials Grant 1507978.

H-34: Comparison of Deproteinization Methods for Porcine Femoral Cortical Bone: Frances Su1; Peter Shyu2; Yik Tung Tracy Ling2; Ekaterina Novitskaya1; Kyungah Seo1; Sofia Lambert3; Kimberlin Zarate4; Olivia Graeve1; Iwona Jasiuk2; Joanna McKittrick1; 1University of California, San Diego; 2University of Illinois at Urbana-Champaign; 3Centro de Enseñanza Técnica y Superior - Campus Mexicali; 4Hilltop High School
    Scientists and engineers have struggled to mimic the shape and size of biogenic hydroxyapatite for use in osteoconductive bone implants. While synthetic hydroxyapatite particles are round, biogenic hydroxyapatite are thin platelets. Instead of synthesizing platelet hydroxyapatite, deproteinization, or removing protein from bone, is a different method of producing biogenic hydroxyapatite. Previous studies have shown that 2.6 wt.% sodium hypochlorite, 7 wt.% hydrogen peroxide, 1N potassium hydroxide, and 1N sodium hydroxide are effective in deproteinizing bone. Since bone also contains fats, defatting using a 2:1 chloroform-methanol solution was added to the sodium hypochlorite treatment. Porcine femoral cortical bone samples were treated, and results were analyzed using x-ray diffraction to verify that the crystal structure of hydroxyapatite was not affected by the treatments. Thermogravimetric analysis and Raman spectroscopy were used to determine if there was remaining protein in the samples. This research is supported by the National Science Foundation (DMR-1507978).