Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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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 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.