Symposium Organizers
Jikou Zhou Lawrence Livermore National Laboratory
Antonio G. Checa Universidad de Granada
Oludele O. Popoola Zimmer, Inc.
E. Dianne Rekow New York University, College of Dentistry
GG1: Multiscale Mechanical Behavior of Bone and Tissues
Session Chairs
Antonio Checa
Oludele Popoola
Dianne Rekow
Jikou Zhou
Tuesday PM, March 25, 2008
Room 3009 (Moscone West)
9:15 AM - **GG1.1
How Really Tough is Human Bone?
Robert Ritchie 1 2 , Kurt Koester 1 2 , Joel Ager 2
1 Materials Science & Engineering, University of California, Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractHuman bone has evolved to be more difficult to break than split. However, appropriate fracture-toughness measurements to break bone (in the transverse direction) are rare. Most measurements focus on crack initiation, whereas human bone principally derives its fracture resistance during crack growth; moreover, the few crack-growth toughness (R-curve) measurements are for longitudinal “splitting” orientations. Here we use nonlinear-elastic fracture mechanics to determine crack-resistance R-curves for both orientations in human cortical bone, using in situ testing within an environmental scanning-electron microscope to simultaneously examine the salient damage/toughening mechanisms. We find that stress-intensities up to 5 MPa√m are required to propagate large cracks along the bone long axis, whereas to propagate a crack only 500 microns in transverse directions requires stress-intensities five times higher. Such toughnesses are far larger than previously thought, yet represent a truer depiction of conditions to break, rather than split, bone. Mechanistically, this behavior results from microcracking at osteon/interstitial interfaces, which promotes gross crack deflections for transverse cracking and crack bridging for longitudinal orientations.
9:45 AM - **GG1.2
The Bone Diagnostic Instrument: Correlations with Conventional Measurements of Materials Properties.
Paul Hansma 1 , Nadder Sahar 2 , Alexander Proctor 1 , Phillip Mathews 1 , Eugene Yurtsev 1 , Patricia Turner 1 , David Kohn 3 2
1 Physics, University of California, Santa Barbara, California, United States, 2 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biologic and Materials Sciences, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe Bone Diagnostic Instrument1 is designed to measure materials properties of bone even if it is covered with soft tissue such as periosteum, connective tissue and skin. It uses 1) a probe assembly, consisting of a reference probe that penetrates soft tissue and stops on the surface of the bone and a test probe that is inserted into the bone, 2) an actuation system that can move the test probe into and out of the bone, 3) a sensing system that can determine the dynamics of the test probe as it moves in the bone, and 4) a measurement system to record the data that is sensed during the motion. In our current prototypes, a sharpened, solid test probe slides inside a sharpened hypodermic needle that serves as the reference probe. A load cell senses the force as a function of the distance that the test probe is inserted into the bone relative to the position of the reference probe that rests on the surface of the bone. Cyclic force vs. distance curves can be analyzed by custom software based, in part, on instrumented indentation analysis2. The parameters from such an analysis were compared to the parameters from conventional analysis of 4 point bending tests on the same pieces of bone, specifically, bone from 10 human donors ranging in age from 17 to 83 years old. There were correlations between parameters obtained in the two ways. The long range goal for research on the Bone Diagnostic Instrument is to develop a diagnostic tool to help physicians assess fracture risk in their patients: specifically the contribution to fracture risk due to deterioration of materials properties such as fracture toughness. The availability of this tool could also help in the development and monitoring of new therapies to mitigate or reverse deterioration3 based on microscopic understanding of bone mechanical properties4.References:1. Hansma, P.K., Turner, P., & Fantner, G.E. Bone Diagnostic Instrument. Review of Scientific Instruments 77, 075105 (2006). 2. W. C. Oliver and G. M. Pharr, Journal of Materials Research 19, 3 (2004).3. Nalla, R.K., Kruzic, J.J., Kinney, J.H. & Ritchie, R.O. Effect of aging on the toughness of human cortical bone: evaluation by R-curves. Bone 35, 1240 (2004).4. Gupta,H. S., Fratzl, P., Kerschnitzki, M., Benecke, G., Wagermaier, W., and Kirchner, H.O. K., Evidence for an elementary process in bone plasticity with an activation enthalpy of 1 eV. J. R. Soc. Interface 4, 277–282 (2007.This work supported in part by NIH grant RO1 GM 065354-05 and DoD/US Army DAMD17-030100556. PH and AP have a financial interest in Active Life Technologies, founded by Davis Brimer, which intends to market Bone Diagnostic Instruments.
10:15 AM - GG1.3
Cohesive Finite Element Based and Fractal Dimension Related Analyses of Microstructure Dependent Dynamic Fracture in Trabecular Bone.
Vikas Tomar 1
1 Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, United States
Show AbstractTrabecular bone fracture is closely related to the trabecular architecture and microdamage accumulation. In the presented research a cohesive finite element method (CFEM) based approach that can be used to model microstructure and loading rate dependent fracture in the trabecular bone is developed. Recently, it has been proven that 3-D micro-CT histomorphometry of trabecular bone can be correlated easily to the fractal dimension of the corresponding 2-D micro-CT image. Accordingly, this research tries to explore how the dynamic fracture in 2-D morphologies of trabecular bone can be used to histomorphometric properties of 3-D trabecular bone architectures. The use of recently reported methods on fracture analyses of trabecular bone is made for this purpose, [1, 2]. Crack propagation analyses are carried out in two different 2-D slices cut from a three dimensional 8 mm diameter cylinder of trabecular bone from an ovine (sheep) femur. Bone tissue is modeled as an orthotropic material with the cohesive parameters calculated from the fracture properties measured in experiments. The emphasis of analyses is on understanding the effect of the rate of loading and its correlation with the bone microstructure on the microdamage accumulation and fracture behavior in the trabecular bone. Besides the obvious dependence of the trabecular bone fracture behavior on the rate of loading and the microstructure, it is found that the mean trabeculae thickness is an important parameter that can strongly influence the fracture properties. The trabecular bone architecture with less apparent density and higher trabeculae thickness is more resistant to fracture than the trabecular bone architecture with high apparent density and with lower trabeculae thickness. Clearly, apparent density alone is not an appropriate failure strength characterizing parameter for trabecular bone. Microstructure with higher mean trabeculae thickness and lower apparent density is more fracture resistant than the one with lower mean trabeculae thickness and higher apparent density. Under the conditions studied, the simultaneous formation of microcracks and their coalescence in a material with lesser fracture strength allow more energy to be dissipated than in a material with higher fracture strength. The results also show that the damage evolution, crack growth and energy release rate are strongly dependent on loading rate. References:1. Tomar, V. "Modeling of dynamic fracture and damage in 2-Dimensional trabecular bone microstructures using the cohesive finite element method.", 2007, to appear in ASME J. Biomech. Engg.2. Dubey, D. K., and Tomar, V., 2007, Microstructure dependent dynamic fracture analyses of trabecular bone based on nascent bone atomistic simulations", 2007, to appear in Elsevier Mechanics Research Communications Special Issue on Multiscale Modeling.
10:30 AM - GG1.4
Correlating Changes in Bone Mechanics and Apatite Chemistry with Targeted Gene Disruptions.
Beril Kavukcuoglu 1 , Adrian Mann 1 2
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States, 2 Biomedical Engineering, Rutgers University, Piscataway, New Jersey, United States
Show Abstract10:45 AM - GG1.5
Variations in Indentation Modulus with Bone Tissue Age.
Jayme Burket 1 , Samuel Gourion-Arsiquaud 2 , Lorena Havill 3 , Shefford Baker 4 , Adele Boskey 2 5 6 , Marjolein van der Meulen 1 2
1 Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, United States, 2 Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, New York, United States, 3 Department of Genetics, Southwest Foundation for Biomedical Research, San Antonio, Texas, United States, 4 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 5 Department of Biochemistry, Weill Medical College of Cornell University, New York, New York, United States, 6 Graduate Program in Physiology, Biophysics, and Systems Biology, Weill Medical College of Cornell University, New York, New York, United States
Show AbstractOsteoporosis results in compromised bone strength and an increased risk of fracture. Numerous therapies have been developed but have failed to achieve adequate fracture prevention due to a lack of understanding of the bone tissue properties that lead to fracture. To characterize the changes that occur with disease and treatment, we must first understand these properties in normal bone and how they are affected by factors including both tissue and animal age. Human bone is constantly remodeling, and therefore tissue age is generally younger than animal age. Nonhuman primates provide an excellent model for human bone because they have a haversian microstructure that also undergoes secondary remodeling. In this study, osteons were used to model tissue age, as a natural gradient in tissue age exists from the center (youngest tissue) to the periphery (oldest tissue) of the osteon. The current study focuses on how indentation modulus and hardness, as measured by quasi-static nanoindentation, vary with tissue and animal age. Cross sections of female baboon femurs from animals of age 0.28 to 19.17 years were dehydrated, embedded in PMMA, and polished to a surface roughness of approximately 15 nm for nanoindentation. Each of these animals had died of natural causes and had no evidence of bone disease. Osteons were selected from the cross sections for FTIR microspectroscopy, AFM, and nanoindentation. For the nanoindentation studies, three radial lines of indentations were made from the center to the periphery for each osteon analyzed. A nanoindentation system with scanning force microscopy imaging allowed indents to be placed in the center of each lamella. Depending on the individual osteon’s size, 5 to 10 lamellae were indented along the radius. A maximum indentation load of 700 µN was used, producing an average contact depth on the order of 150 nm to minimize surface roughness effects. Indentation modulus initially increased with increasing tissue age and then remained constant across the older tissue of the osteon. This trend was similar across the animals of different ages and paralleled measurements of mineral content and crystallinity in these samples. This behavior also corresponds to tissue age results seen previously in the rat bone cortex. The relationship between these indentation moduli and the spectroscopy results will allow us to relate tissue material properties to composition as a function of tissue and animal age. These data provide normative information about osteonal behavior to which diseased and treated bone tissue can be compared in the future.This work was supported by the NSF and NIH.
11:30 AM - **GG1.6
Biomechanics of Human Skin Damage Processes.
Kemal Levi 1 , Robert Weber 2 , James Do 1 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry and Biochemistry, UCSC, Santa Cruz, California, United States
Show Abstract12:00 PM - GG1.7
Stress Relaxation of Skin Tissue under Hyperthermal Temperatures.
Feng Xu 1 , Tianjian Lu 2 , Keith Seffen 1
1 Engineering Department, Cambridge University, Cambridge United Kingdom, 2 School of Aerospace, Xi’an Jiaotong University, Xi'an China
Show Abstract12:15 PM - GG1.8
A Microstruture-Based Approach for Modeling the Large Deformation, Anisotropic, Nonlinear Viscoelastic Behavior of Fiber-Reinforced Soft Tissues.
Thao Nguyen 1
1 Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractFiber-reinforced soft tissues such as the cornea, tendons, and blood vessels are extraordinarily stiff, strong, flexible, and tough. The toughness of these tissues arises from the ability of both the soft fibers (e.g. collagen and elastin) and matrix to dissipate energy through large viscoelastic deformations. A microstructure-based constitutive model has been developed for the finite-deformation, anisotropic, nonlinear viscoelastic behavior of fiber-reinforced soft tissues that incorporates viscoelastic deformation mechanisms of both the fiber and matrix constituents. The tissue is modeled as a continuum mixture of one-dimensional fiber families embedded in a matrix phase. The constituents are assumed to deform according to the continuum deformation gradient of the tissue. Nonlinear stress relations and viscous flow rules are formulated for the both the matrix phase and fiber families. Then, the one-dimensional constitutive relations for the fiber families are homogenized over the density distribution of fiber orientations to formulate three-dimensional stress relations and viscous flow rules for the fiber phase. The sum of the stress response of the matrix and fiber phases gives the stress response of the tissue. The result is a microstructure-based approach for modeling soft tissues that incorporates the viscoelastic properties of the matrix and fiber materials and the fiber architecture into the tissue response. In addition, the approach allows for a thermodynamically consistent, fully nonlinear description of fiber viscoelasticity, which is in contrast to previous micostructure-based models (e.g., Lanir 1983 and Bischoff 2006) which relied on quasilinear viscoelastic formulations. The model has been applied to describe the anisotropic and nonlinear viscoelastic behavior of the cornea. Results show that the model can reproduce experimental data for the anisotropic nonlinear stress-dependent creep and rate-dependent stress-strain response of the tissue.
12:30 PM - GG1.9
Biomechanical Properties of Aorta and Vena Cava Determined by Scanning Acoustic Microscopy and Nanoindentation.
Riaz Akhtar 1 , Michael Sherratt 2 , Rachel Watson 2 , Paul Mummery 1 , Brian Derby 1
1 School of Materials, University of Manchester, Manchester United Kingdom, 2 Faculty of Medical and Human Sciences, University of Manchester, Manchester United Kingdom
Show Abstract12:45 PM - GG1.10
Zone-Specific Changes in Micromechanical, Biochemical, and Structural Properties in Articular Cartilage from a Rabbit Joint Flexion Model.
Cheng Li 1 , Karen King 2 , Lisa Pruitt 3
1 UCB&UCSF Joint Graduate Group in Bioengineering, UC Berkeley, Berkeley, California, United States, 2 Orthopedics-Bioengineering, University of Colorado at Denver and Health Sciences Center, Aurora, Colorado, United States, 3 Mechanical Engineering, UC Berkeley, Berkeley, California, United States
Show AbstractThe excellent load support and lubrication properties of articular cartilage are conferred by the characteristic organization of the extracellular matrix (ECM) (Figure 1). The cartilage ECM consists primarily of water (70-80%), Type II collagen fibrils (10-15%) and proteoglycan aggrecan (5-10%)[1]. Chondrocytes occupy only 3-5% of the volume of adult articular cartilage and are responsible for the turnover of the tissue’s ECM. Under normal conditions, cartilage ECM is in a state of dynamic equilibrium, balanced between synthesis and breakdown. Recently there has been strong evidence that physical forces in the chondrocyte environment affect the cellular function, and that excessive joint loading can lead to cartilage degeneration [2-4]. Since the function of cartilage is dependent on the integrity of its ECM, which also influences the activity of the resident chondrocytes, it is important to examine the local property changes in the ECM in order to render implications about mechanisms of cartilage metabolism in normal and disease conditions. Sadaat et al. have demonstrated in the rabbit metacarpophalangeal (MCP) joint that 80h of cumulative physiological joint loading leads to stimulation of proteoglycan synthesis localized to the deep zone of cartilage [5]. The goals of this study are two-fold: to understand the changes in structure-property and composition-property relations in cartilage due to physical forces; and to examine the effect of collagen network structure (random in the mid zone versus organized in the deep zone) on the micromechanical properties of cartilage. MCP proximal bone-cartilage specimens from the fourth digit are collected from loaded and contralateral control limbs of the New Zealand White rabbits (n=6). The specimens are cryofractured into two half specimens with complimentary sagittal surfaces. Suture markers, placed within the bone, should be visible on the surface and serve to establish proper orientation. On one half of the specimen, tissue stiffness is measured using a 100 micron spherical tip with a nanoindenter (Hysitron Inc., Minneapolis, MN). The region of interest (ROI) is approximately 500 microns wide x 100 microns deep, which includes the entire thickness of the cartilage. Six to eight indents are averaged for each of the mid and deep zones. The complimentary half specimens are decalcified, and three 7 um sections corresponding to the ROI for each specimen are evaluated for collagen and proteoglycan content with Fourier Transform Infrared microspectroscopy. The remaining sections are processed for histology to evaluate foroverall microstructure and to measure the middle and deep layer thicknesses at the ROI using light and polarized light microscopy respectively. Finally correlations are made for the structural, biochemical, and mechanical properties measured. Furthermore, comparison of results from control and loaded specimens can help to elucidate local property changes due to physiological loading.
GG2: Nanomechanical Behavior of Biological Materials
Session Chairs
Antonio Checa
Chwee Lim
Oludele Popoola
Jikou Zhou
Tuesday PM, March 25, 2008
Room 3009 (Moscone West)
2:30 PM - **GG2.1
Nanomechanical Testing of a Single Nanofiber.
Chwee Teck Lim 1
1 Division of Bioengineering, National University of Singapore, Singapore Singapore
Show AbstractNanoscale biomaterials such as nanofibers have been extensively used in biomedical applications including tissue engineering, molecular filters and controlled drug delivery. As these nanofibers are often subject to physical stresses during application, it is important to ensure their structural integrity remains intact and that they do not fail. Mechanical testing of a single nanofiber has not been widely performed due to its small size. However, such tests are important as the structural makeup and mechanical properties are found to vary significantly for nanofibers with diameters ranging from tens to hundreds of nanometers. These tests aim to help us better understand the structure-property relationship at the nanoscale. Here, we present tensile tests of single polymer nanofibers with varying diameters performed under a scanning electron microscope where the deformation and failure modes of the nanofiber were observed. It was noted that the mechanical properties of the nanofiber are diameter dependent. In terms of deformation, the nanofiber was observed to undergo multiple necking before failure. We also performed atomic force microscopy of a nanofiber undergoing stretching from elastic to plastic deformation and eventually to failure. It was observed that a nanofiber comprised both crystalline and amorphous states with crystallinity being higher for smaller fibers and this greatly affected the tensile strength of the nanofiber. Also, there was significant nanostructural rearrangement and fragmentation of the crystallites observed in the nanofiber during stretching. These results help us to better relate the nanomechanical properties to the nanostructural rearrangement and makeup of the nanofibers.
3:00 PM - GG2.2
Inhomogeneous Mechanical Properties of Articular Chondrocytes Measured by Atomic Force Microscopy.
Nadeen Chahine 1 , Todd Sulchek 1
1 , Lawrence Livermore National Lab, Livermore, California, United States
Show AbstractChondrocytes are responsible for the elaboration and maintenance of the extracellular matrix (ECM) in articular cartilage, and previous studies have demonstrated that mechanical loading modulates the biosynthetic response of chondrocytes in cartilage explants. Therefore, the mechanical properties in chondrocytes play a pivotal role in regulating the interaction between the cell and ECM in situ. The goal of this study is to investigate the indentation-dependent stiffness of chondrocytes using atomic force microscopy. Cells were isolated from young bovine joints, and plated pre-confluence on glass coverslips with media in a closed fluid cell. AFM cantilever tips were modified to approximate a spherical indenter by gluing a single 9μm polystyrene bead to the apex of each cantilever tip, resulting in mechanical properties representative of the bulk properties of the cell. For each measurement, the spherical bead and target cell were aligned with micrometer-actuated stage and visualized with an attached Zeiss inverted microscope. The mechanical behavior of single cells was determined by impinging the target cell with the probe and recording the force dependent deflection. Force-deflection curves were then analyzed using a non-hertzian technique (Costa K.D. et al, 2006), where no assumptions about the material properties of the cell were made a priori. This analysis yields a pointwise modulus, representing an indentation-dependent stiffness of the cell. Results indicate that chondrocytes exhibit significant indentation-dependent variation in the apparent modulus. The modulus was greatest at initial contact, and decreased monotonically with increasing compression. The apparent modulus was found to be 0.71±0.26 kPa initially, and decreased to a constant value of 0.22±0.02 kPa for indentation between 200 and 1000 nm. These findings suggest that chondrocytes behave as inhomogeneous elastic materials. The mechanical properties of chondrocytes may impact how these cells interact with their surrounding ECM. The results of this study may be incorporated into future finite element analyses of cell-matrix interactions, in order to account for this inhomogeneous response of chondrocytes to compression.
3:15 PM - GG2.3
AFM Nanomechanical Studies and the Potential Role of Amyloid-like Nanofibrils in the Toughness of the Barnacle Adhesive.
Ruby May Sullan 1 , Nikhil Gunari 2 , Gilbert Walker 1
1 Chemistry, University of Toronto, Toronto, Ontario, Canada, 2 Chemistry, University of Pittsburgh, Toronto, Pennsylvania, United States
Show Abstract3:30 PM - GG2.4
Advanced Mechanical Characterization of Biomaterials for Device Optimization.
Jill Powell 1
1 , CSM Instruments, Inc., Needham, Massachusetts, United States
Show AbstractUnderstanding the mechanical behavior of biological and biomaterials is essential to the development of these materials and the devices they are used in. In recent years, investigating these systems at a degree beyond the traditionally available macroscopic methods has become a great focus. This includes the use of micro- and nano-scale contact mechanical characterization such as indentation testing and scratch testing. CSM Instruments, through collaborative efforts with a number of well-recognized industry partners, has developed extensive experience in the varied analysis methods required by this quickly evolving field.The mechanical behavior of biomaterials (both biological and synthetic) span multiple magnitude levels, from the intracellular forces operating at the molecular level to macroscopic organization of multi-layer coating systems commonly employed. The purpose of this presentation is to introduce a number of theoretical and experimental studies, with the desire to create discussion that will lead to the further exploitation of mechanical characterization techniques.
3:45 PM - GG2.5
A New Method for Determining the Nano-scale Elastic Modulus of a Viscoelastic Biomaterial Through Quasi-static Large-amplitude Oscillatory Indentation.
Naoki Fujisawa 1 , Michael Swain 2
1 Department of Electronic Materials Engineering, Australian National University, Canberra, Australian Capital Territory, Australia, 2 Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, Sydney, New South Wales, Australia
Show Abstract4:00 PM - GG2: Nano
Break
4:15 PM - **GG2.6
A Single Molecule Approach Utilizing Linker Stiffness to Understand Multivalent Binding Kinetics.
Todd Sulchek 1
1 , LLNL, Livermore, California, United States
Show Abstract4:45 PM - GG2.7
The use of Dynamic Holographic Optical Tweezers for Force Measurements on Biomaterials.
Astrid van der Horst 1 , Nancy Forde 1
1 Physics, Simon Fraser University, Burnaby, British Columbia, Canada
Show Abstract5:15 PM - GG2.9
Microsecond Force Spectroscopy: Detailed Nanomechanical Measurements at the Microsecond Timescale in Air and Liquid Environments.
Ozgur Sahin 1
1 Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts, United States
Show Abstract5:30 PM - **GG2.10
Implementation of a Bio-chemo-mechanical Model for Cell Contractility.
Anthony Evans 1 , Vikram Deshpande 1 , Robert McMeeking 1
1 Materials, UCSB, Santa Barbara, California, United States
Show Abstract
Symposium Organizers
Jikou Zhou Lawrence Livermore National Laboratory
Antonio G. Checa Universidad de Granada
Oludele O. Popoola Zimmer, Inc.
E. Dianne Rekow New York University, College of Dentistry
GG4: Poster Session: Mechanical Behavior of Biological Materials and Biomaterials
Session Chairs
Wednesday PM, March 26, 2008
Exhibit Hall (Moscone West)
1:00 AM - GG4.1
Effect of Decellularization Protocols on the Mechanical Properties of Common Porcine Carotid Artery.
John Fitzpatrick 1 , Peter Clark 2 , Franco Capaldi 1
1 Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania, United States, 2 School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractDiseases of the human vascular system are the leading cause of death and hospitalization in the United States. Surgical treatments for vascular complications, such as bypassing or replacing occluded arteries, are complicated by the lack of healthy tissue available for grafting. The biomedical feasibility of using xenografts and allografts has recently been established as an alternative to Dacron® and expanded polytetraflouroethylene (ePTFE) biomaterials, which lose patency after a short time.
Through decellularization procedures, vascular tissue can be reduced to a sterilized scaffold, after which it can be seeded with the transplant recipient’s stem cells, and implanted with a low risk of rejection. Solvents used to break the bonds between vascular smooth muscle cells and the scaffold such as sodium deoxycholate, EDTA, and SDS, are known to denature collagen. This may have a significant impact on the mechanical properties of the scaffold, possibly causing a compliance mismatch at the graft anastomosis. Previous decellularization studies that investigated biomechanics of acellular tissue have found no significant changes in the rupture strength of these scaffolds, but the mechanical behavior of the vessels at physiological strains has not yet been studied. We will be comparing the mechanical effects of decellularization protocols published in Reider et al. 2004, Schaner et al. 2004 and Bader et al. 1998, at physiological strains.
The aim of this study was to compare decellularization techniques reporting complete or near-complete lysis of vascular smooth muscle cells and identify the protocol which minimizes the change in mechanical behavior. We analyzed rectangular parellepiped arterial wall samples as membranes in order to compare the tensile properties of native and acellular tissue samples cut from similar cross-sections. Least-squares curve fitting was used to fit experimental uniaxial stress-stretch data to a modified form of the Yeoh material model. The Yeoh parameters generated by the least squares fit for native and decellularized sections were then assessed for statistical significance using a paired t-test analysis.
The statistical analysis yielded a p statistic and 90% confidence limits for each protocol. Some protocols had a high p statistic (statistically similar native and acellular samples) while having wide confidence limits, and others vice-versa. Unfortunately no protocol was characterized by high p statistics and comparatively narrow confidence limits, which are ideal results. The decellularization method proposed by Reider et al. had the narrowest confidence limits among the protocols, though it did not show statistical significance. Despite its low p value, the data suggests that Reider decellularization produces more consistent results than the other protocols and is therefore the most effective option for minimizing the change in the mechanical properties of porcine carotid artery tissue.
1:00 AM - GG4.11
Mechanically Tunable Colloid-Liquid Crystal (CLC) Composites that Support Growth of Fibroblasts.
Ankit Agarwal 1 , Sean Palecek 1 , Nicholas Abbott 1
1 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show Abstract1:00 AM - GG4.12
Structure-Based Modeling of Vascular Smooth Muscle Cell Mechanics.
Scott Wood 1 , Jason Hemmer 1 , Martine LaBerge 1 , Delphine Dean 1
1 Bioengineering, Clemson University, Clemson, South Carolina, United States
Show AbstractMany attempts have been made to understand the complex mechanical behavior of the cell. Vascular smooth muscle cells (VSMCs) in particular are constantly under dynamic load due to arterial pressure in normal healthy conditions. In response to the injurious mechanical loading that can occur during stent placement, VSMCs can undergo significant cytoskeletal remodeling. This remodeling leads to changes in the cells mechanical properties that may eventually lead to some restenosis. In general, the ability to predict the behavior of cells from the nanoscale structures could elucidate the mechanisms behind many tissue mechanical properties. Previous attempts to model the mechanical behavior of cells have relied on simplified assumptions for cell behavior, such as assuming a linear elastic or Hertzian behavior. Even when more complex mechanical viscoelastic behavior models have been attempted, the cell was treated as a continuum. In this study, we modeled cells as a viscoelastic material and take into consideration the mechanical effects of actin filaments, microtubules, and cytoplasm. We obtained laser-confocal images of the actin and microtubule networks in VSMCs. These images were converted to model structures. The mechanical properties of the different filaments were approximated using previous measurements of actin and microtubule mechanics and the mechanical response of the model cell was then calculated using finite element analysis. To validate these model results, we performed Atomic Force Microscopy (AFM) stress relaxation tests on living VSMCs in media. We found good agreement between our model and the data. Since the VSMCs were found to be viscoelastic, our model more accurately represented the mechanical response of VSMC than the simple elastic solid model. In future studies, we are incorporating other cytoskeletal structures (e.g., intermediate filaments) into our structure model. These types of cytoskeletal models would be a good starting point for multiscale models of tissue that include not only cells but their nanoscale structures as well.
1:00 AM - GG4.13
Probing the Hydrodynamic Response of Soft Interfaces at the Nanometer Scale.
David Barbero 1 , Ulli Steiner 1
1 Physics, University of Cambridge, Cambridge United Kingdom
Show Abstract1:00 AM - GG4.14
Design of a Dielectrophoretic Mechanical Testing Device.
Greeshma Manomohan 2 , Kavitha Rajendran 2 , Alisa Morss 1 2
2 School of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, Pennsylvania, United States, 1 Mechanical Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show Abstract1:00 AM - GG4.15
New Nanocomposite Biomaterials Controlling Surface and Bulk Properties using Supercritical Carbon Dioxide.
Toru Hoshi 1 , Takashi Sawaguchi 2 , Ryosuke Matsuno 1 , Tomohiro Konno 1 , Madoka Takai 1 , Kazuhioko Ishihara 1
1 , The university of Tokyo, Tokyo Japan, 2 , Nihon university, Tokyo Japan
Show Abstract1:00 AM - GG4.16
Physicochemical Mechanics of Autodegradable Nanobiomembranes.
James Ferri 1 2
1 , Lafayette College , Easton, Pennsylvania, United States, 2 , Max Planck Institute for Colloids and Interfaces, Golm-Potsdam Germany
Show Abstract1:00 AM - GG4.17
A Novel Strategy for Preparation of Multi-functional Micelles from Supramolecular Manipulation.
Ging-Ho Hsiue 1
1 , National Tsing Hua University, Hsinchu Taiwan
Show Abstract1:00 AM - GG4.19
Chemical Tailoring and Characterization of Cellulose Nanofibrils.
Nico Bordeanu 1 , Francisco Lopez-Suevos 1 , Christian Eyholzer 1 , Tanja Zimmermann 1 , Klaus Richter 1
1 , EMPA, Duebendorf Switzerland
Show Abstract1:00 AM - GG4.2
Mechanical Properties of Electrospun Vascular Grafts during In Vitro Degradation.
Xing Zhang 1 , Vinoy Thomas 2 , Aaron Catledge 2 , Yogesh Vohra 2
1 Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama, United States, 2 Physics, University of Alabama at Birmingham, Birmingham, Alabama, United States
Show Abstract1:00 AM - GG4.20
Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites.
Yibin Xue 1 , Kunpeng Wang 1 2 , Hongwu Zhang 2 , Mark Horstemeyer 1
1 Center for Advanced Vehicular Systems, Mississippi State University, Starkville, Mississippi, United States, 2 Department of Engineering Mechancis, Dalian University of Technology, Dalian, Liaoning, China
Show Abstract1:00 AM - GG4.21
Imprinting and Characterization of Soft Biological Gels Down to Submicron Regime.
Parul Agrawal 1 2 , Jian Gu 1 , Cedric Hurth 1 , Nan Iyer 1 , Jianing Yang 1 , Frederic Zenhausern 1 2
1 Center for Applied Nanobioscience, Biodesign Institute at Arizona State University, Tempe, Arizona, United States, 2 Ira A. Fulton School of Engineering, Arizona State University, Tempe, Arizona, United States
Show Abstract1:00 AM - GG4.22
Self-Assembly of Multi-domain Peptides: Effects of Chemical Structure on Mechanical Properties.
Lorenzo Aulisa 1 , Jeffrey Hartgerink 1
1 Chemistry, RICE University, Houston, Texas, United States
Show Abstract1:00 AM - GG4.23
The Mechanical Properties of Mixed Self Assembled Adlayers on InP Substrate.
Heeyeon Wampler 1 , Albena Ivanesevic 1
1 Chemistry, Purdue University, West Lafayette, Indiana, United States
Show Abstract1:00 AM - GG4.24
Stability Of Inserted Proteins In Blm By Vesicle Fusion Process On Porous Silicon Substrates.
Vishnu Baba Sundaresan 1 , M. Austin Creasy 1 , Stephen Sarles 1 , Donald Leo 1
1 Mechanical Engineering Department, Virginia Tech, Blacksburg, Virginia, United States
Show Abstract1:00 AM - GG4.26
Enhancement of Biomechanical Properties of Electrospun Poly(ε-caprolactone) Scaffolds Using Thermal Treatment for Tissue Engineering Applications.
Sang Jin Lee 1 , Se Heang Oh 1 , Jie Liu 1 , Shay Soker 1 , Atala Anthony 1 , James Yoo 1
1 Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, North Carolina, United States
Show Abstract1:00 AM - GG4.28
Effect of Nanofiber Alignment on Myotube Formation of Human Skeletal Muscle Cells on Electrospun Poly(ε-caprolactone)/collagen Nanofiber Meshes.
Jin San Choi 1 , Sang Jin Lee 1 , George Christ 1 , Anthony Atala 1 , James Yoo 1
1 , Wake Forest Institute for Regenerative Medicine, Winston-Salem, North Carolina, United States
Show Abstract1:00 AM - GG4.29
Elasticity of Twisted Biopolymer Assemblies and their Networks.
Moneesh Upmanyu 1 2
1 Engineering Division, Materials Science Program, Colorado School of Mines, Golden, Colorado, United States, 2 Bioengineering and Life Sciences Program, Colorado School of Mines, Golden, Colorado, United States
Show Abstract1:00 AM - GG4.3
Evaluation of Tissue Holding Strength for Different Suturing Techniques in Human and Animal Models.
Meng Deng 1 , Amitha Kumar 1 , David Stoloff 1
1 , Ethicon, Johnson & Johnson, Somerville, New Jersey, United States
Show AbstractSurgery involves closing a wound or incision in muscle, fascia, fat, skin, etc. Although great progress has been made in developing alternative wound closure devices such as adhesives, sealants, tapes and staples, sutures continue to be the materials of choice in surgery. There are generally two types of suturing patterns used to close a wound or incision (i.e., interrupted and continuous suture patterns). The holding strength of the suture determines the effectiveness of a sutured wound closure. To evaluate tissue-holding strength of a suture, various models or media (such as animal tissue, human cadaver, or synthetic materials) may be used. Few studies compare the holding strength of an interrupted suture pattern to a continuous suture pattern in tissue models. We conducted a series of studies to determine the holding strength of a polydiaxone suture used to close an incision. The main purposes of this study was to determine if animal tissues could be used to replace human tissue in the early phase of the development of new sutures. In this study, interrupted and continuous suture patterns were used to close incisions in human cadaver and porcine tissues. During testing, tissues were held in a special fixture that was designed in-house. An Instron mechanical tester was used to measure breaking strength. The relationship between the number of sutures and loops and the tissue holding strength was evaluated. Failure mechanisms were determined. Results from the two tissue models were compared. This study showed the possibility of using porcine tissue to determine tissue-holding strength with sutures. The main findings of the study are summarized as follows.1.For both interrupted and continuous suture patterns, both human and porcine tissue models yielded similar trends between the tissue holding strength and the number of interrupted sutures placed, or number of loops in a continuous suture pattern.2.For the interrupted suture pattern, the holding strength increased as the number of the interrupted sutures increased in conformance with the following equation: Si=A+Bln(Ni), where Si is the holding strength, Ni is number of loops, and A and B are constants. 3.For the continuous suture pattern, the holding strength increased as the number of the loops increased in conformance with the following equation: Sc=C exp(DNc), where Sc is strength, Nc is number of interrupted sutures, and C and D are constants. 4.Failure is a gradual process.5.For the interrupted suture pattern, most failures occurred first at the knot.6.For the continuous suture pattern, failure occurred at the knot or in the middle of the strand.7.During testing, some minor tissue damage was present that did not impact on the testing.
1:00 AM - GG4.30
Buckling and Bulging Mechanical Measurements of Nanoscale Silk Fibroin Films.
Ray Gunawidjaja 1 , Chaoyang Jiang 1 , XianYan Wang 2 , Yen-Hsi Lin 1 , Maneesh Gupta 3 , Kaplan David 2 , Rajesh Naik 3 , Vladimir Tsukruk 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States, 3 , Materials and Manufacturing Directorate Air Force laboratory Wright-Patterson Air Force Base, Dayton, Ohio, United States
Show Abstract1:00 AM - GG4.4
Investigation and Modeling of the Elastic Properties of Lobster Cuticle Depending on its Grade of Mineralization.
Christoph Sachs 1 , Svetoslav Nikolov 1 , Helge Fabritius 1 , Dierk Raabe 1
1 Microstructure Physics and Metal Forming, Max-Planck-Institut fuer Eisenforschung, Duesseldorf Germany
Show AbstractThe cuticle of the American lobster Homarus americanus represents a multilayer, chitin-protein-based biological composite containing variable amounts of nanoscopic biominerals. In the cuticle, three structurally different layers can be distinguished: an outermost epicuticle and an inner procuticle consisting of exocuticle and endocuticle. The epicuticle is a thin, waxy layer while the mechanically relevant layers, the exocuticle and the endocuticle, are made up of mineralized chitin-protein fibers. Local variations in composition and structure of the material provide a wide range of mechanical properties. Particularly, the grade of mineralization affects the mechanical properties of the cuticle. In the claws of the lobster the endocuticle makes up around 90 vol.% of the cuticle. The test specimens studied here originate from the claws of the lobster and are tested in both dry and wet state to evaluate the effect of moisture. By performing cyclic compression-tension tests as well as bending tests, the elastic properties of both the exocuticle and the endocuticle were examined. The grade of mineralization was determined by thermo-gravimetric analysis of the samples. The experimental data for effective elastic properties are compared to the predictions of a model based on continuum micromechanics where the overall properties are obtained via step-by-step homogenization from lower to higher levels of structural hierarchy.
1:00 AM - GG4.5
Deformation at Large Strains of Hydrophobically Modified Hydrogels: a Molecular Interpretation of Hysteresis.
Costantino Creton 1 , Guillaume Miquelard-Garnier 1 , Dominique Hourdet 1
1 Laboratoire PPMD, ESPCI-CNRS-UPMC, Paris France
Show AbstractAlthough most hydrogels are very weak and soft materials, recent studies have reported the design of mechanically tough hydrogels(1-2). The underlying reason of these differences remains difficult to generalize and must be related in particular to the large strain response of these materials. We have synthesied as series of chemically crosslinked polyacrylic acid hydrogels, with and without C12 side groups grafted along the main chain. Such hydrophobic side groups form clusters in water which have been shown to greatly increase the viscosity in solution and make the hydrogel much more dissipative in linear viscoelasticity(3). We have explored here the large strain properties of the same hydrophobically modified and chemically crosslinked polyelectrolyte hydrogels and have found a clear evidence of increasingly dissipative processes as the gel is strained to larger deformations. These dissipative processes are associated with the formation of nanoclusters. These clusters appear to have two origins: the presence of hydrophobic side groups which can form micelles in water, and the attractive potential that same charge polyelectrolyte chains experience at close range due to ion condensation. We systematically investigated the macroscopic mechanical properties of the gel with compression experiments up to strain levels of several hundred percent and found a very significantly increasing hysteresis in the loading/unloading cycles as the maximum compressive strain was increased above 150%. Fracture stresses of the gels in compression exceeded twenty times their modulus and fracture toughnesses in tension were five times higher for the modified hydrogels than for the unmodified.(1) Gong, J. P.; Katsuyama, Y.; Kurokawa, T.; Osada, Y. Adv. Mater. 2003, 15, 1155-1158.(2) Haraguchi, K.; Li, H. J. Macromolecules 2006, 39, 1898-1905.(3) Miquelard-Garnier, G.; Demoures, S.; Creton, C.; Hourdet, D. Macromolecules 2006, 39, 8128-8139.
1:00 AM - GG4.6
Initial Attachment and Orientation of Osteoblast-Like Cells on Laser Grooved Ti-6Al-4V Surfaces: Effects of Multiscale Surface Features Produced by Laser Processing.
Jianbo Chen 1 , Winston Soboyejo 1
1 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show AbstractThis paper presents the results of an experimental study of the effects of the micro and sub-micro surface features produced by laser irradiation on the initial attachment and adhesion of human osteo-sarcoma (HOS) cells on laser grooved Ti-6Al-4V surfaces. The multi-scale, micro and sub-micro surface features were characterized using scanning electron microscopy (SEM), stylus profilometry, and atomic force microscopy (AFM). Pre- and post-processing inspections of the surface chemical composition were performed using X-ray photoelectron spectroscopy (XPS). The initial cell spreading and orientations were observed and quantified after 15-min, 1-hour, 4-hours and 24-hour culture periods. Immuno-fluorescence staining of adhesion proteins (actin and vinculin) was used to study the spreading and adhesion of HOS cells in 1 hour and 4 hour culture experiments. The initial cell adhesion was also characterized using enzymatic detachment tests. The results show that cell spreading and adhesion were enhanced by micron-scale groove geometry and micro/sub-micron-scale surface feature in the initial 4 hours of cell culture. The effects increase with time, which were not remarkable after 1 hour, but very obvious after 4 hours. Contact guidance was found to promote cell adhesion. The increase is attributed to the interactions between the focal adhesions and the patterned extra-cellular matrix (ECM) proteins on the laser micro-grooved surfaces.
1:00 AM - GG4.7
Elastic Property Measurements of Bone Tissue using Atomic Force Microscope, Nanoindentation, and Atomistic Simulations.
Michelle Michalenko 1 , Albert Cerrone 1 , Devendra Dubey 1 , Vikas Tomar 1
1 Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, United States
Show Abstract1:00 AM - GG4.9
A Novel Method to Quantify the Drying Stresses of Human Stratum Corneum.
Kemal Levi 1 , James Do 1 , Allison Rhines 1 , Robert Weber 2 , Reinhold Dauskardt 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Chemistry and Biochemistry, UCSC, Santa Cruz, California, United States
Show AbstractGG3: Mechanics of Cells and Networks
Session Chairs
Antonio Checa
Oludele Popoola
Dianne Rekow
Jikou Zhou
Wednesday PM, March 26, 2008
Room 3009 (Moscone West)
9:30 AM - GG3.1
Immobilizing Biological Molecules for Recognition Imaging and Force Spectroscopy Applications.
Travis Johnson 1
1 Nanomeasurements Division, Agilent Technologies, Chandler, Arizona, United States
Show Abstract10:15 AM - GG3.3
A Miniaturized Cell Stretching Tool using Ionic Polymer Metal Composites Actuator.
Shin Hitsumoto 1 , Tadashi Ihara 2 , Keisuke Morishima 1
1 Department of mechanical systems engineering, Tokyo university of agriculture and technology, Koganei, Tokyo, Japan, 2 Faculty of medical engineering, Suzuka university of medical science, Suzuka, Mie, Japan
Show Abstract10:30 AM - GG3.4
Critical Shear Stress Study of Cell Attachment.
Aracely Rocha 1 , Mariah Hahn 2 , Zoubeida Ounaies 3 , Hong Liang 1
1 Mechanical Engineering, Texas A&M University, Bryan, Texas, United States, 2 Bioengineering, Texas A&M University, College Station, Texas, United States, 3 Aerospace, Texas A&M University, College Station, Texas, United States
Show Abstract10:45 AM - GG3.5
Characterisation of Cell Adhesion to Substrate Materials and the Resistance to Enzymatic and Mechanical Cell-Removal.
Helen Griffiths 1 , James Dean 1 , Athina Markaki 1 2 , Trevor Clyne 1
1 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 2 Department of Engineering, University of Cambridge, Cambridge United Kingdom
Show AbstractThe strength of adhesion at the cell-substrate interface is an important parameter in the design of many prosthetic implant material surfaces, due to the desire to create and maintain a strong implant-tissue bond. A systematic study has been carried out on a series of Ti-6Al-4V substrates with a range of surface morphologies and chemistries. Cells were seeded at a low concentration onto substrates and cultured for a set number of days to ensure adhesion of viable cells. The ease of removal of cells from these substrates via treatment with a dilute trypsin solution was compared to the ease of mechanical removal of cells from the same substrates. The resistance to removal by both shear forces, imposed by fluid flow, and normal forces, imposed via pressure though a micropipette, on individual cells was studied. Fluid dynamics modelling has been carried out to calculate the shear forces experienced by the cells during a range of fluid flow conditions. A comparison of the ease of detachment of cells via these methods and hence their validity as measures of the strength of cell-substrate adhesion is presented.
11:30 AM - **GG3.6
Modeling Interactions between Nanoparticles and Cells.
Huajian Gao 1 , Wendong Shi 1 , Jizeng Wang 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States
Show Abstract12:15 PM - GG3.8
Measurement of Contractile Forces From Cultured Muscle Fibers With a Bio-MEMS Device.
Kerry Wilson 1 , Mainak Das 1 , Peter Molnar 2 , Kathryn Wahl 3 , James Hickman 1 , James Hickman 1
1 NanoScience Technology Center, University of Central Florida, Orlando , Florida, United States, 2 Tribology Section, U.S. Naval Research Laboratory, Washington, District of Columbia, United States, 3 Chemistry Division, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractAdvances in biotechnology have opened new avenues for the application of semiconductor manufacturing technologies in the form of gene and protein arrays, lab-on-a-chip devices and biological micro-electromechanical systems (Bio-MEMS). To date application of these technologies has largely focused on the study of biomolecules and single cells or cell types. However, these technologies also hold great promise for the study of complex cellular and tissue interactions that are of critical importance when developing new drug therapies for disease and catastrophic injury. A tissue type of broad interest with regard to drug development and basic cell biology is skeletal muscle, which is affected by a variety of pathological conditions such as progressive muscular atrophy (PMA), amyotrophic lateral sclerosis (ALS), and muscular dystrophy. For this reason we have developed a Bio-MEMS device based on microfabricated silicon cantilevers for the controlled, real-time interrogation of embryonic rat muscle fibers as a high-throughput test bed for drug discovery and basic science. The cantilevers were fabricated using standard photolithographic and micromachining techniques. The surfaces of the cantilevers were then modified using the amine-terminated alkylsilane (3-Trimethoxysilyl propyl) diethylenetriamine (DETA) to improve cellular adhesion, growth and differentiation. Dissociated embryonic rat myocytes were cultured for 7-10 days in a defined serum-free medium until contractile muscle fibers had formed. Monitoring and interrogation of the muscle fibers was accomplished using an AFM detection system of our own design, which consisted of an electrophysiology microscope, photodiode laser, position sensitive detector, field stimulation chamber, and a computer with data acquisition and analysis software. This simple system has allowed the real-time, high-throughput analysis of the physiological properties of the contracting muscle fibers. With this system we have shown the ability to selectively control the frequency and magnitude of muscle fiber contraction as well as induce and observe physiological phenomena such as tetanus and fatigue. Contraction forces were calculated using a modified Stoney’s equation for bending of a cantilever due to thin film stress. The resulting stress values were found to be in good agreement with previously published results for cultured muscle fibers. Microfluidic channels were also integrated for the controlled introduction of exogenous factors (drugs, growth factors, etc). Ongoing work will allow the selective patterning and co-culture of neuronal cell types with muscle fibers for studying the neuromuscular junction and in vitro biological circuits.
12:30 PM - GG3.9
Mechanics of the Hysteretic Large Strain Behavior of Mussel Byssus Threads.
Brian Greviskes 1 , Katia Bertoldi 1 , Mary Boyce 1
1 Mechanical Eng., MIT, Cambridge, Massachusetts, United States
Show Abstract12:45 PM - GG3.10
Nanomechanics of Bacterial Spore Coat Folding.
Ozgur Sahin 1 , Adam Driks 2
1 Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, Illinois, United States
Show Abstract
Symposium Organizers
Jikou Zhou Lawrence Livermore National Laboratory
Antonio G. Checa Universidad de Granada
Oludele O. Popoola Zimmer, Inc.
E. Dianne Rekow New York University, College of Dentistry
GG7: Deformation and Microstructure of Biological Materials
Session Chairs
Antonio Checa
Oludele Popoola
Dianne Rekow
Jikou Zhou
Thursday PM, March 27, 2008
Room 3009 (Moscone West)
2:30 PM - **GG7.1
Deformation and Toughening Secrets of Seashells.
Xiaodong Li 1
1 Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractSeashells are natural nanocomposites with superior mechanical strength and toughness. What is the secret recipe that Mother Nature uses to fabricate seashells? What roles do the nanoscale structures play in the inelasticity and toughening of seashells? Can we learn from this to produce seashell-like nanocomposites? Here we limit our focus to nacre (mother-of-pearl). This presentation summarizes the recent discovery of nanoparticles in nacre and elucidates the roles that these nanoparticles play in nacre’s toughness. We found that aragonite nanoparticles can rotate, which contributes to energy dissipation in nacre’s deformation and fracture. The mechanical properties of nacre’s biopolymer layer were measured by in situ AFM mechanical testing. This presentation also presents future challenges in the study of nacre’s nanoscale structure and mechanical properties.
3:00 PM - **GG7.2
Investigation of the Lattice Strain Evolution in Tension and Compression of Different Phases in the Mineralized Lobster Cuticle.
Christoph Sachs 1 , Sangbong Yi 2 , Dierk Raabe 1
1 Microstructure Physics and Metal Forming, Max-Planck-Institut fuer Eisenforschung, Duesseldorf Germany, 2 Institute of Materials Science and Engineering, Clausthal University of Technology, Clausthal-Zellerfed Germany
Show AbstractThe cuticle of the American lobster Homarus americanus has to meet a wide range of mechanical properties according to its various biological functions. Like arthropod cuticles in general, the cuticle of the American lobster is a multilayered chitin-protein-based biological composite. Most crustaceans, including the lobster, additionally harden their cuticle by the incorporation of variable amounts of nanoscopic biomineral particles, in this case calcite and amorphous calcium carbonate (ACC). By performing tensile and compression tests combined with in-situ lattice strain measurements using synchrotron X-ray diffraction and strain analysis via digital image correlation, the elastic-plastic deformation behavior and the underlying microscopic deformation of the different phases of the cuticle were examined. In order to investigate the contribution of the different phases to the elastic and plastic deformation in tension and compression a set of Debye-Scherrer rings was repeatedly registered during the stepwise straining of the samples. Since the full Debye-Scherrer rings were recorded on the image plate, the lattice strain evolution along the loading direction as well as that perpendicular to the loading direction can be measured simultaneously. By testing the samples in different directions to the surface of the cuticle, anisotropy of the deformation behavior could be investigated. The test specimens originated from the claws of the lobster and were tested both in dry and wet state to evaluate the effect of moisture on the deformation behavior.
3:30 PM - GG7.3
Reversible Yield in an Extensible, Proteinaceous Material Found in Gastropod Egg Capsules.
Stephen Wasko 1 , Herbert Waite 1
1 Biomolecular Sciences and Engineering, University of California Santa Barbara, Goleta, California, United States
Show Abstract3:45 PM - GG7.4
A Statistical Model of Plasticity in Nacre.
Mark Jhon 1 2 , Daryl Chrzan 1 2
1 Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractThe inherently discrete brick-and-mortar structure of nacre is challenging to describe using traditional continuum modeling techniques. Most existing models focus on identification of the dominant small scale structure and its impact on the deformation process. These studies, however, are incomplete in that they do not directly address the large scale deformation patterns observed in nacre: deformation is not highly localized, but rather is spread over large volumes involving many platelets. In order to study the many-platelet interactions, a simplified mechanical system derived from a random spring model is introduced and analyzed via Monte Carlo simulations. The mechanical properties of the ensemble are related to the properties of the individual blocks. In particular, the dependence of the overall strength on the microscopic plasticity law is established. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
4:00 PM - **GG7.5
Nanostructure and Mechanical Property of Organic-Inorganic Interface in Abalone Shell Nacre.
Nan Yao 1
1 PRISM, Princeton University, Princeton, New Jersey, United States
Show AbstractNacre, the crown jewel of natural materials, has been extensively studied because of its remarkable physical properties for over 160 years. Yet, the precise structural features governing its extraordinary strength and its growth mechanism remain elusive. In this paper, we present a series of discoveries pertaining to the red abalone shell’s organic-inorganic interface, organic interlayer morphology and properties, large-area crystal domain orientations, and nacre growth. In particular, we describe unique horizontal nanogrowths and paired screw dislocations in the aragonite layers, and demonstrate that the organic material sandwiched between aragonite platelets consists of multiple organic layers of varying nanomechanical resilience. Based on these novel observations, we propose a comprehensive spiral growth model that accounts for both horizontal growth of aragonite sheets and vertical propagation via helices that surround numerous screw dislocation cores. These new findings can provide a basis for creating novel organic-inorganic micro/nano composites through synthetic or biomineralization pathways.
4:30 PM - GG7.6
Wandering Spiders use Viscoelastic Properties of Cuticle for Mechanical Signal Filtering.
Michael McConney 1 2 , Clemens Schaber 3 , Michael Julian 4 , Friedrich Barth 3 , Vladimir Tsukruk 1 2
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 School of Polymer, Textile, and Fiber Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Department of Neurobiology and Cognition Research, Faculty of Life Sciences, University of Vienna, Vienna Austria, 4 Department of Chemistry, University of Arkansas Fort Smith, Fort Smith, Arkansas, United States
Show Abstract4:45 PM - GG7.7
New Strategies to Toughened Hydrogels using Living Polymerization.
James Hedrick 1 , Fredrick Nederberg 1 , Russell Pratt 1 , Robert Waymouth 2 , Curt Frank 2
1 , IBM Research, San Jose, California, United States, 2 , Stanford University, Stanford, California, United States
Show Abstract5:00 PM - **GG7.8
Microstructures In The Formation Of Chemical Gardens.
C. Ignacio Sainz Diaz 1 , Bruno Escribano 1 , Julyan Cartwright 1
1 Instituto Andaluz de Ciencias de la Tierra, University of Granada, Granada Spain
Show AbstractThursday, March 27New Abstract*GG7.8 @ 4:00 PMMicrostructures In The Formation Of Chemical Gardens.C. Ignacio Sainz Diaz, Bruno Escribano, Julyan Cartwright; Instituto Andaluz de Ciencias de la Tierra, University of Granada, Granada, Spain.