Finite element analysis was implemented in three stages to design a piezoresistive, micro-electro-mechanical systems sensor array consisting of four-terminal sensors placed on deformable silicon diaphragms. This sensor array was used to retrofit the Contrel-Dubousset instrumentation in order to capture forces and moments applied by surgeons in real time during scoliosis correction surgery. Outputs from the sensor array have been designed to be compatible with a low-power wireless data transmission system that is currently being developed with a collaborating team in the biomedical industry. The designed sensor array is capable of resolving forces of up to 1000 N and moments of up to 4000 N mm in three dimensions during surgery. A process flow to produce the first prototyped version of this micro sensor with known performance characteristics is presented and tested. Acceptable correlation was found between the performance of the manufactured prototypes, numerical simulation and similar documented devices.
In ACL reconstruction, stiffness and strength of a tendon graft complex are important features for knee stability and rehabilitation. The fixation between tendon and bone is known to be one of the weakest components of the graft complex. We examined the tensile loaddisplacement characteristics of looped semitendinosus tendons in a porcine femoral tunnel. Two groups of six cadaveric semitendinosus tendons and porcine femurs were tested, secured with either an aperture or nonaperture fixation method. Constructs were tested at 1 mm/s until failure in a materials testing machine, which allowed force and displacement data to be recorded. The nonaperture fixation group was significantly less stiff for the first 4 mm of displacement and had significantly higher ultimate failure loads. Provided that adequate ultimate strength can be achieved, stiffness properties of a tendon graft will be improved by using aperture fixation in femoral-site ACL reconstruction.Résumé Dans la reconstruction du LCA la rigidité et la résistance du complexe greffe-tendon sont des éléments importants pour la stabilité du genou et la récupération fonctionnelle. La fixation entre le tendon et l'os est connue pour être un des maillons faibles de l'ensemble. Nous avons examiné les caractéristiques de l'élasticité sous traction de tendons du demi-tendineux insérés en boucle dans un tunnel fémoral porcin. Deux groupes de six tendons cadavériques ont été testés, amarrés par une fixation avec ou sans ouverture. Les constructions ont été testées à 1 mm/s jusqu'à la rupture avec une machine á traction qui permet d'enregistrer la force et le déplace-ment. Le groupe avec la fixation sans ouverture était significativement moins rigide pour les premiers 4 mm de déplacement et avait une charge de rupture nettement plus haute. A condition que la tension de rupture puisse être atteinte, les propriétés de rigidité d'une greffe tendineuse seront améliorées en utilisant la fixation avec ouverture au niveau du site fémoral dans la reconstruction du LCA.
A three-axis load detector has been designed and manufactured utilizing four piezoresistive sensors on a flexible silicon membrane. The detector was prototyped using bulk microfabrication techniques on a single-crystal silicon wafer and was designed to detect normal and shear loadings applied to the membrane. Finite element analysis and experimental calibration methods have been used to determine the shear and normal sensitivity values. Device parameters were modified with emphasis on increasing the absolute shear to normal sensitivity ratio of the sensors without reducing their ultimate strength. It was determined that the shear to normal sensitivity ratio greater than 0.5 would allow detection of shear loads considering experimental error present. For devices with square membranes having 1000 µm edge lengths and 65 µm thicknesses, this amount of shear sensitivity was achievable using a mesa with a height of at least 150 µm.
Developments in micro and nanotechnology within the renewable energy industry have the potential to create significant advances for the renewable energy industry. A review of selected renewable energy sectors being influenced by micro and nanotechnology was performed, finding that the most promising areas involve electricity generation, biomass technologies, and hydrogen technologies. Such technologies include: surface microtexturization and nanocrystalline films in photovoltaic and photoelectrochemical cells; nanoscale catalysts and membranes in biomass or thermochemical hydrogen generation; surface utilization of carbon nanotubes in hydrogen storage and fuel cell applications. These advances may increase process yields and efficiencies, and also may lower overall costs.
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