This PhD dissertation presents the exploration and development of two carbon materials, carbon nanotubes (CNTs) and carbon fiber (CF), as either key functional components or unconventional substrates for a variety of MEMS applications. Their performances in three different types of MEMS devices, namely, strain/stress sensors, vibration-powered generators and fiber solar cells, were evaluated and the working mechanisms of these two non-traditional materials in these systems were discussed. The work may potentially enable the development of new types of carbon-MEMS devices. Firstly, a MEMS-assisted electrophoretic deposition (EPD) technique was developed, aiming to achieve controlled integration of CNT into both conventional and flexible MEMS systems. Selective deposition of electrically charged CNTs onto desired locations was realized in the EPD process through patterning of electric field lines created by the microelectrodes fabricated using MEMS techniques. A variety of 2-D and 3-D micropatterns of CNTs with controllable thickness and morphology have been successfully achieved in both rigid and elastic systems at room temperature with relatively high throughput. Studies also showed that high surface hydrophobicity of the non-conductive regions in microstructures was critical to accomplish well-defined selective micropatterning of CNTs through this strategy. A patterned PDMS/CNT nanocomposite was then fabricated through the aforementioned approach, and was incorporated, investigated and validated in elastic force/strain microsensors. The gauge factor of the sensor exhibited a strong dependence on both the initial resistance of the device and the applied strain. Detailed analysis of the data suggests that the piezoresistive effect of this specially constructed bi-layer composite could be three folds, and the sensing mechanism may vary when physical properties of the CNT network embedded in the polymer matrix alter. The feasibility of the PDSM/CNT nanocomposite serving as an elastic electret was further explored. The nanocomposite composed of these two non-traditional electret materials exhibited electret characteristics with reasonable charge storage stability. The power generation capacity of the corona-charged nanocomposite has been characterized and successfully demonstrated in both a ball drop experiment and the cyclic mechanical load experiments. Lastly, in an effort to develop carbon-material-based substrates for MEMS applications, a carbon fiber-based poly-Si solar cell was designed, fabricated and investigated. This fiber-type photovoltaics (PV) takes advantage of the excellent thermal stability, electrical conductivity and spatial format of the CF, which allows CF to serve as both the building block and the electrode in the PV configuration. The photovoltaic effects of the fiber PV were demonstrated with an open-circuit voltage of 0.14 V, a short-circuit current density of 1.7 mA/cm2, and output power density of 0.059mW/cm2. The issues of this system were discussed as well.

Les fibres monocristallines d'oxyde de lutécium et aluminium (Lu3Al5O12 - LuAG), non dopées ou intentionnellement dopées au cérium, élaborées par la technique de micro-pulling down sont de sérieuses candidates pour le développement de nouvelles générations de calorimètres à scintillation. Cependant, cette technique de croissance est complexe et nécessite une étude approfondie pour améliorer les propriétés optiques de ces fibres. Après avoir ajusté la température de croissance, les paramètres principaux étudiés furent la concentration en Cerium, la vitesse de croissance et l'orientation du cristal (fixé par le germe). Les meilleurs résultats ont été obtenus en combinant une vitesse de croissance relativement lente (0,25 mm/min), une teneur en Ce assez faible (~0.01 at.%) et une orientation <111> du cristal de LuAG. Ces fibres optimisées, de diamètre 1 ou 2 mm et de longueur atteignant 22 cm, présentaient une surface plus lisse et une densité de défauts et/ou cracks réduite. Dans les meilleurs cas, les mesures d'atténuation lumineuse ont montré une longueur d'atténuation pouvant dépasser 30 cm. Ces fibres se sont montrées également plus résistantes aux radiations / Single crystalline Cerium doped and undoped lutetium aluminum garnet fibers (Lu3Al5O12 - LuAG) grown by the micro-pulling-down technique show promising results for the development of future calorimeters due to its high scintillation properties. But this growth technique is complex and requires deep investigation for improving further the light properties of the grown fiber. After adjusting the growth temperature, the three main parameters studied were the cerium concentration, the growth rate, and the crystal orientation (fixed by the see). Best results were obtained by a combination of relatively low pulling speed (0.25mm/min), diluted cerium content of ~0.01 at.% and <111> oriented LuAG seed. These optimized fibers, which could be of 1 or 2 mm diameter and up to 22 cm long, showed a much smoother surface and reduced cracks and/or defects. In the best cases, light attenuation measurements indicated enhanced attenuation length which could be higher than 30 cm. Moreover, these fibers were found to display improved radiation hardness

This diploma thesis will discuss possibilities of using inorganic fibers to improve the mechanical properties of the resulting physical body bricks. Assessment of the effect of fiber length, fiber thickness is in the order of micrometers. In this work we were used fibers which are commercially produced for the purpose of reinforcement, but also waste fibers, which mainly serves as an insulator.