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Instruments / Technical Area	Publication Details	Published
I13-2-Diamond Manchester Imaging	Effect of SR-microCT radiation on the mechanical integrity of trabecular bone using in situ mechanical testing and digital volume correlation Marta Peña Fernández , Silvia Cipiccia , Enrico Dall'ara , Andrew J. Bodey , Rachna Parwani , Martino Pani , Gordon W. Blunn , Asa H. Barber , Gianluca Tozzi Journal Of The Mechanical Behavior Of Biomedical Materials DOI: 10.1016/j.jmbbm.2018.08.012 Diamond Proposal Number(s): [14080] Show Abstract ▼ Abstract: The use of synchrotron radiation micro-computed tomography (SR-microCT) is becoming increasingly popular for studying the relationship between microstructure and bone mechanics subjected to in situ mechanical testing. However, it is well known that the effect of SR X-ray radiation can considerably alter the mechanical properties of bone tissue. Digital volume correlation (DVC) has been extensively used to compute full-field strain distributions in bone specimens subjected to step-wise mechanical loading, but tissue damage from sequential SR-microCT scans has not been previously addressed. Therefore, the aim of this study is to examine the influence of SR irradiation-induced microdamage on the apparent elastic properties of trabecular bone using DVC applied to in situ SR-microCT tomograms obtained with different exposure times. Results showed how DVC was able to identify high local strain levels (>10,000 µε) corresponding to visible microcracks at high irradiation doses (~230 kGy), despite the apparent elastic properties remained unaltered. Microcracks were not detected and bone plasticity was preserved for low irradiation doses (~33 kGy), although image quality and consequently, DVC performance were reduced. DVC results suggested some local deterioration of tissue that might have resulted from mechanical strain concentration further enhanced by some level of local irradiation even for low accumulated dose.	Aug 2018
I22-Small angle scattering & Diffraction	Probing multi-scale mechanics of peripheral nerve collagen and myelin by x-ray diffraction Fabio Bianchi , Felix Hofmann , Andrew J. Smith , Hua Ye , Mark S. Thompson Journal Of The Mechanical Behavior Of Biomedical Materials DOI: 10.1016/j.jmbbm.2018.07.030 Diamond Proposal Number(s): [12528] Show Abstract ▼ Abstract: Peripheral nerves are continuously subjected to mechanical forces, both during everyday movement and as a result of traumatic events. Current mechanical models focus on explaining the macroscopic behaviour of the tissue, but do not investigate how tissue strain translates to deformations at the microstructural level. Predicting the effect of macro-scale loading can help explain changes in nerve function and suggest new strategies for prevention and therapy. The aim of this study was to determine the relationship between macroscopic tensile loading and micro scale deformation in structures thought to be mechanically active in peripheral nerves: the myelin sheath enveloping axons, and axially aligned epineurial collagen fibrils. The microstructure was probed using x-ray diffraction during in situ tensile loading, measuring the micro-scale deformation in collagen and myelin, combined with high definition macroscopic video extensiometry. At a tissue level, tensile loading elongates nerves axially, whilst simultaneously compressing circumferentially. The non-linear behaviour observed in both directions is evidence, circumferentially, that the nerve core components have the ability to rearrange before bearing load and axially, of a recruitment process in epineurial collagen. At the molecular level, axially aligned epineurial collagen fibrils are strained, whilst the myelin sheath enveloping axons is compressed circumferentially. During induced compression, the myelin sheath shows high circumferential stiffness, indicating a possible role in mechanical protection of axons. The myelin sheath is deformed from low loads, despite the non-linearity of whole tissue compression, indicating more than one mechanism contributing to myelin compression. Epineurial collagen shows similar load-bearing characteristics to those of other collagenous connective tissues. This new microstructural knowledge is key to understand peripheral nerve mechanical behaviour, and will support new regenerative strategies for traumatic and repetitive injury.	Jul 2018
I02-Macromolecular Crystallography	Biomechanical model of the human cornea: Considering shear stiffness and regional variation of collagen anisotropy and density Charles Whitford , Harald Studer , Craig Boote , Keith Meek , Ahmed Elsheikh Journal Of The Mechanical Behavior Of Biomedical Materials 42, 76 - 87 DOI: 10.1016/j.jmbbm.2014.11.006 Diamond Proposal Number(s): [919] Open Access Show Abstract ▼ Abstract: A numerical model based on continuum mechanics theory has been developed which represents the 3D anisotropic behaviour of the corneal stroma. Experimental data has been gathered from a number of previous studies to provide the basis and calibration parameters for the numerical modelling. The resulting model introduces numerical representation of collagen fibril density and its related regional variation, interlamellar cohesion and age-related stiffening in an anisotropic model of the human cornea. Further, the model incorporates previous modelling developments including representation of lamellae anisotropy and stiffness of the underlying matrix. Wide angle X-ray scattering has provided measured data which quantifies relative fibril anisotropy in the 2D domain. Accurate numerical description of material response to deformation is essential to providing representative simulations of corneal behaviour. Representing experimentally obtained 2D anisotropy and regional density variation in the 3D domain is an essential component of this accuracy. The constitutive model was incorporated into finite element analysis. Combining with inverse analysis, the model was calibrated to an extensive experimental database of ex vivo corneal inflation tests and ex vivo corneal shear tests. This model represents stiffness of the underlying matrix which is 23 orders of magnitude than the mechanical response representing the collagen fibrils in the lamellae. The presented model, along with its age dependent material coefficients, allows finite element modelling for an individual patient with material stiffness approximated based on their age. This has great potential to be used in both daily clinical practice for the planning and optimisation of corrective procedures and in pre-clinical optimisation of diagnostic procedures.	Feb 2015
I22-Small angle scattering & Diffraction	Strain-rate sensitivity of the lateral collateral ligament of the knee Timothy J. Bonner , Nicolas Newell , Angelo Karunaratne , Andy D. Pullen , Andrew A. Amis , Anthony M J Bull , Spyros D. Masouros , Malintha Karunaratne Journal Of The Mechanical Behavior Of Biomedical Materials 41, 261 - 270 DOI: 10.1016/j.jmbbm.2014.07.004 Diamond Proposal Number(s): [8555] Show Abstract ▼ Abstract: The material properties of ligaments are not well characterized at rates of deformation that occur during high-speed injuries. The aim of this study was to measure the material properties of lateral collateral ligament of the porcine stifle joint in a uniaxial tension model through strain rates in the range from 0.01 to 100/s. Failure strain, tensile modulus and failure stress were calculated. Across the range of strain rates, tensile modulus increased from 288 to 905 MPa and failure stress increased from 39.9 to 77.3 MPa. The strain-rate sensitivity of the material properties decreased as deformation rates increased, and reached a limit at approximately 1/s, beyond which there was no further significant change. In addition, time resolved microfocus small angle X-ray scattering was used to measure the effective fibril modulus (stress/fibril strain) and fibril to tissue strain ratio. The nanoscale data suggest that the contribution of the collagen fibrils towards the observed tissue-level deformation of ligaments diminishes as the loading rate increases. These findings help to predict the patterns of limb injuries that occur at different speeds and improve computational models used to assess and develop mitigation technology.	Jan 2015
I22-Small angle scattering & Diffraction	Structure-mechanical function relations at nano-scale in heat-affected human dental tissue Tan Sui , Michael Sandholzer , Eric Le Bourhis , Nikolaos Baimpas , Gabriel Landini , Alexander Korsunsky Journal Of The Mechanical Behavior Of Biomedical Materials DOI: 10.1016/j.jmbbm.2013.12.014 Open Access Show Abstract ▼ Abstract: The knowledge of the mechanical properties of dental materials related to their hierarchical structure is essential for understanding and predicting the effect of microstructural alterations on the performance of dental tissues in the context of forensic and archaeological investigation as well as laser irradiation treatment of caries. So far, few studies have focused on the nano-scale structure-mechanical function relations of human teeth altered by chemical or thermal treatment. The response of dental tissues to thermal treatment is thought to be strongly affected by the mineral crystallite size, their spatial arrangement and preferred orientation. In this study, synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) techniques were used to investigate the micro-structural alterations (mean crystalline thickness, crystal perfection and degree of alignment) of heat-affected dentine and enamel in human dental teeth. Additionally, nanoindentation mapping was applied to detect the spatial and temperature-dependent nano-mechanical properties variation. The SAXS/WAXS results revealed that the mean crystalline thickness distribution in dentine was more uniform compared with that in enamel. Although in general the mean crystalline thickness increased both in dentine and enamel as the temperature increased, the local structural variations gradually reduced. Meanwhile, the hardness and reduced modulus in enamel decreased as the temperature increased, while for dentine, the tendency reversed at high temperature. The analysis of the correlation between the ultrastructure and mechanical properties coupled with the effect of temperature demonstrates the effect of mean thickness and orientation on the local variation of mechanical property. This structural–mechanical property alteration is likely to be due to changes of HAp crystallites, thus dentine and enamel exhibit different responses at different temperatures. Our results enable an improved understanding of the mechanical properties correlation in hierarchical biological materials, and human dental tissue in particular.	Dec 2013

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