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Item Validation of high strain rate, multiaxial loads using an in-plane loader, digital image correlation, and FEA(Montana State University - Bozeman, College of Engineering, 2018) Stroili, Christopher; Chairperson, Graduate Committee: David A. MillerMontana State University's In-Plane Loader (IPL) is a machine designed to test for mechanical properties at multi-axial states of stress and strain by in-plane translation and rotation. Historically the machine has been used to characterize composite lay-ups, where applying multi-axial loads can better describe anisotropic materials. The IPL testing machine uses Digital Image Correlation (DIC) software and a stereoscopic camera system to measure strains on the surface of the test coupon by tracking a stochastic pattern applied to the gage section. The focus of this work was to test the capabilities beyond quasi-static composites testing, specifically looking to explore the feasibility of testing plastics and metals at strain rates from 10 0 to 10 3 s -1. This work explored the speed and loading capabilities of the IPL and determined a suitable coupon geometry which balances gage section area with material strength. 304 Stainless Steel was tested both on the IPL and in uniaxial tension. Experimental tensile test data was fit to a Johnson Cook strain rate sensitive constitutive model. This constitutive equation was then used with an implicit dynamic finite element analysis (FEA) model. To study the validity of high rate testing of steel in the IPL, strain from the DIC experimental data was compared with the FEA results. While the strains predicted by the FEA model varied from experimental results, a better understanding of the IPL capabilities has been achieved. Moving forward, a series of recommendations have been made so that high strain rate multi-axial testing of metals can be implemented with more robust constitutive models.Item In vitro and in vivo systems mechanobiology of osteoarthritic chondrocytes(Montana State University - Bozeman, College of Engineering, 2015) Zignego, Donald Lee; Chairperson, Graduate Committee: Ronald K. June II; Aaron A. Jutila, Martin K. Gelbke and Daniel M. Gannon were co-authors, and Ronald K. June was a corresponding author of the article, 'The mechanical microenviroment of high concentration agarose for applying deformation to primary chondrocytes' in the journal 'Journal of biomechanics' which is contained within this thesis.; Aaron A. Jutila was a main author, Bradley K. Hwang, Jonathan K. Hilmer, Timothy Hamerly, Cody A. Minor and Seth T. Walk were co-authors, and Ronald K. June was a corresponding author of the article, 'Candidate mediators of chondrocyte mechanotransduction via targeted and untargeted metabolomic measurements' in the journal 'Archives of biochemistry and biophysics' which is contained within this thesis.; Carley N. McCutchen, Jonathan K. Hilmer were co-authors, and Ronald K. June was a corresponding author of the article, 'Mechanotransduction in primary human osteoarthritic chondrocytes is mediated by metabolism of energy, lipids, and amino acids' submitted to the journal 'Arthritis and rheumatology' which is contained within this thesis.; Jonathan K. Hilmer was a co-author, and Ronald K. June was a corresponding author of the article, 'Shotgun phosphoproteomics identifies activation of vimentin, ankyrin, vam6/vpS39-like protein in primary human osteoarthritic chondrocytes after mechanical stimulation' submitted to the journal 'eLife' which is contained within this thesis.; Sarah E. Mailhiot, Timothy Hamerly, Edward E. Schmidt were co-authors, and Ronald K. June was a corresponding author of the article, 'Alterations in joint metabolomics following surgical destabilization and exercise in a novel cartilage reporter mouse model' submitted to the journal 'Annals of biomedical engineering' which is contained within this thesis.All cells are subjected to and respond to mechanical forces, but the underlying processes linking the mechanical stimuli to biological responses are poorly understood. In the joints of the body (e.g. the knee, hip, etc...) articular cartilage serves as a low friction, load bearing material and is subjected to near-constant mechanical loading. Through excessive loading of the joint, usually caused by obesity or injury, the protective articular cartilage begins to diminish, leading to the progression of osteoarthritis (OA). Osteoarthritis is the most common joint disorder in the world and is characterized by the deterioration of articular cartilage. Determining the link between cartilage deterioration and mechanical loading is one motivation that drove this research. Articular cartilage is composed of a dense extracellular matrix (ECM), a less-stiff pericelluar matrix (PCM), and highly specialized cells called chondrocytes. As the sole cell type in cartilage, chondrocytes are responsible for the healthy turnover of the ECM by creating, maintaining, and repairing the matrix. Multiple lines of evidence suggest chondrocytes can transduce mechanical stimuli into biological signals. The hypothesis for this research is that physiologically pertinent loading of chondrocytes results in a specific set of bio-signals resulting in matrix synthesis. To test this hypothesis, two unbiased, large-scale metabolomic and phosphoproteomic datasets were generated by modeling physiological compressive loading on 3D-embedded chondrocytes. To assess loading-induced changes in metabolites (e.g. small molecules representing the functional state of the cell) and proteome-wide patterns of post-translational modifications (i.e. phosphorylation), chondrocytes were encapsulated in physiologically stiff agarose, compressively loaded in tissue culture, and analyzed via liquid chromatography -- mass spectrometry (LC-MS). The results helped identify global and local biological patterns in the chondrocytes which are a direct result from mechanical loading. In addition, a novel mouse model that expresses cartilage specific bioluminescence was used to assess loading induced changes in vivo. The results from the mouse model allowed for in vivo validation and integration of the in vitro results from the metabolomic and phosphoproteomic results. To my knowledge, such research has never been done, and considerably expands the scientific knowledge of chondrocyte mechanotransduction.Item Design and comparative material analysis of a capacitive type pressure sensor for measurement of knee pressure distribution of rodents(Montana State University - Bozeman, College of Engineering, 2013) Rashid, Al Maqsudur; Chairperson, Graduate Committee: Ronald K. June IIRodents are commonly used in biomedical and biomechanical research because of their genetic and biological characteristics closely resemble those of humans. Rodents have similar knee joint structures to human beings, and are commonly used as models for human osteoarthritis. Biomechanical factors influencing the patterns of pressure distribution within the joint are very important in the pathogenesis of osteoarthritis at the knee joints. The pattern of pressure distribution of the femoral condyles of weight bearing knee joints is therefore of great interest. A flexible and biocompatible Polymer based Micro-Electromechanical (MEMS) pressure sensor was designed for this purpose with capacitive sensor array embedded inside the structure. The sensor structure comprises of a 4x16 arrays of sensors embedded inside the Polymer structure with air gaps and insulation layers to provide a suitable dielectric medium to achieve better capacitive sensitivity. A three dimensional model of the sensor was created using ANSYS Workbench Design Modeler and analyzed with two different types of polymers and metals as potential structural materials of the sensor. A suitable clean-room fabrication process was proposed and analyzed for the sensor and corresponding mask designs were created with a CAD (Computer Aided Design) program. Residual stresses due to mismatch of thermal coefficient of expansion were calculated along with proposing a schematic readout circuitry for high gain and signal to noise ratio and failure analysis of the sensor.Item Development and validation of a system for studying chondrocyte mechanotransduction with preliminary metabolomic results(Montana State University - Bozeman, College of Engineering, 2013) Jutila, Aaron Arthur; Chairperson, Graduate Committee: Ronald K. June IIOsteoarthritis (OA) is a degenerative disease currently affecting over 46 million Americans. OA is most commonly characterized by breakdown of articular cartilage within the joint resulting in abnormal loading, loss of motion, and pain. Articular cartilage is the tough, flexible, load-bearing material that allows for joints to articulate smoothly i.e. running with relative ease. Currently there is no cure for this disease and the exact causes remain relatively unknown. Chondrocytes are the only cell type found in cartilage and are responsible for all biological maintenance and repair. Previous studies have shown that chondrocytes respond to mechanical load by cellular mechanotransduction, the process by which cells convert mechanical stimuli into biochemical activity. The aim of this thesis is to study the effects that mechanical loads have on human chondrocyte metabolism to better understand OA. To study chondrocyte mechanotransduction it was vital to develop a machine that could simulate in vivo loading of chondrocytes within the human knee joint. A bioreactor was designed, built, and validated that can simulate physiological loading in a tissue culture environment. This bioreactor was then used to characterize the mechanical properties of a viscoelastic material (agarose) capable of maintaining viable 3-Dimensional cell cultures. Inside the body chondrocytes are surrounded by a pericellular matrix (PCM), which provides a unique stiffness much less than the stiffness of cartilage. The mechanical property tests performed on agarose allowed for an accurate representation of this cellular microenvironment. Agarose gel concentrations were found that can model both healthy PCM and OA PCM stiffness. Methods were then developed to encapsulate living chondrocytes within these physiologically stiff gels. Utilizing these newly developed gel constructs and custom built bioreactor, 3-Dimensional chondrocyte suspensions were subjected to dynamic compression simulating normal physiological loading i.e. walking. It was hypothesized that moderate dynamic loading would promote changing in the central metabolism pathways, such as glycolysis. To study this hypothesis, mass-spectrometry techniques were utilized to identify metabolites present in each sample, and if the amount of each metabolite changed due to dynamic compression. These results provide a robust foundation for understanding cellular mechanotransduction.Item Mouse/rat knee static loading test apparatus(Montana State University - Bozeman, College of Engineering, 2013) Rose, Thomas Joseph; Chairperson, Graduate Committee: Ronald K. June IIOsteoarthritis (OA) involves mechanically-related cartilage deterioration and affects millions worldwide. To date no effective treatments for OA exist and to expedite the solution process rodent models that mimic human disease are used before attempting to apply to human models. Rodent models of osteoarthritis involve mechanical destabilization of the knee joint which likely changes the contact pressure distribution. However, no methods currently exist for measuring the contact pressure distribution in mouse or rat knees. Therefore, the objective was to develop a method to measure the contact pressure distribution within a mouse knee. This research designed and tested an apparatus to apply loads to mouse knees based on measurements of young mouse knees and mature rat knees. Applied loads were used to explore measureable pressure zone shifts within the knee for varying flexion angles. Measurements of the tibia plateau were used to estimate contact area for an expected pressure range. Based on this preliminary information, a machine was designed to incorporate 6 degrees of freedom that allows the application of compressive loading while allowing the knee as natural of movement as possible. To apply the load a mechanical system was devised to both measure and apply joint loading. Several iterations of both of these systems were considered and the final product was created for testing. Several hurdles were overcome during testing, which included creating a method to interface the biological knee to the mechanical system, developing a technique to measure the pressure distribution of extremely small areas, and the requirement for accurate calibration of both the load application and measurement. It is assumed that the results will be the first pressure distribution measurements in the murine knee. Extension of these results may yield valuable insight into the mechanical environment of rodent osteoarthritis models.