Microvalves are essential components of the miniaturization of the fluidic systems to control of fluid flow in a variety of applications as diverse as chemical analysis systems, micro-fuel cells, and integrated fluidic channel arrangements for electronic cooling. Using microvalves, these systems offer important advantages: they can operate using small sample volumes and provide rapid response time. This PhD dissertation presents the world first electromagnetically actuated microvalve fabricated on a single wafer with CMOS compatibility. In this dissertation, the design, fabrication, and testing results of two different types of electromagnetic microvalves are presented: the on/off microvalve and the bistable microvalve with latching mechanism. The microvalves operate with power consumption of less than 1.5 W and can control the volume flow rate of DI water, or a 50% diluted methanol solution in the range 1 - 50 µL in. The leaking rate of the on/off microvalve is the order of 30 nL/min. The microvalve demonstrated a response time for latching of 10 ms in water and 0.2 ms in air. This work has resulted in a US patent, application no. 10/699,210.Other inventions that have been developed as a result of this research are bidirectional, and bistable-bidirectional microactuators with latching mechanism, that can be utilized for optical switch, RF relay, micro mirror, nano indenter, or nano printings.

Computational fluid dynamics (CFD) modeling is possibly the best available technique in designing and predicting the performance of Stirling and pulse tube refrigerators (PTR). One of the limitations of CFD modeling of these systems, however, is that it requires closure relations for the micro porous materials housed within their regenerators and heat exchangers. Comprehensive prediction of fluid-solid interaction through this media can be obtained only by direct pore level simulation, a process which is time consuming and impractical for system level examination. Through the application of empirical correlations including the Darcy permeability and Forchheimer's inertial coefficient, the microscopic momentum equations governing fluid behavior within the porous structure can be recast as viable macroscopic governing equations. With these constitutive relationships, CFD can be an efficient and powerful tool for system modeling and optimization. The purpose of this study is to determine the hydrodynamic parameters of two mesh fillers relevant to miniature PTRs; stacked screens of 635 mesh stainless steel and 325 mesh phosphor-bronze wire cloth. Experimental setups were designed and fabricated to measure steady and oscillatory pressures and mass flow rates of the working fluid, research-grade helium. Hydrodynamic parameters for the two mesh fillers were determined for steady-state and steady periodic flow in both the axial and radial directions for a range of flow rates, operating frequencies and charge pressures. The effect of average pressure on the steady axial flow hydrodynamic parameters of other common PTR filler materials was also investigated. The determination of sample hydrodynamic parameters and their subsequent computational and experimental methodologies utilized are explained.

La tendance à la miniaturisation des produits n'est pas sans influence sur l'évolution de leurs moyens de production et d'assemblage. En effet, dû à la réduction d'échelle, l'assemblage de petits composants (appelé microassemblage) est perturbé par les forces de surface comme les forces de capillarité. Ces forces, exercées par le pont liquide reliant manipulateur et composant, sont habituellement négligeables (et négligées) dans l'assemblage conventionnel dominé par les forces de gravité. L'approche originale suivie dans ce travail consiste à tirer parti de ces effets et à les utiliser pour la manipulation de microcomposants, c'est-à-dire de composants dont la taille va de quelques dizaines de microns à quelques millimètres. Ce travail tente donc d'apporter quelques réponses aux problèmes de conception posés par un tel choix: quels sont les avantages d'une telle approche? Comment ces forces `fonctionnent-elles'? Sont-elles suffisamment grandes pour manipuler des microcomposants? Comment, dans ce cas, relâcher le composant? Quel rôle la tension de surface joue-t-elle? En quoi le choix des matériaux est-il important? Comment optimiser la conception du manipulateur? Tout au long de ce travail, le lecteur trouvera un inventaire des principes de manipulation existants, les éléments nécessaires à la modélisation des forces de capillarité, ainsi que la description de la simulation et du banc d'essai développés par l'auteur dans le but d'étudier ces paramètres de conception. Les résultats présentés dans cette thèse recouvrent essentiellement deux thèmes: quelles sont les règles de conception à suivre pour maximiser les forces de capillarité (problème de la préhension) et comment choisir une stratégie de relâche adéquate (problème de la relâche)? / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished