Magnetic shape memory (MSM) materials are a new class of smart materials which exhibit shape deformation under the influence of an external magnetic field. They are interesting for various types of applications, including actuators, displacement/force sensors, and motion dampers. Due to the huge strain and the magnetic field-driven nature, MSM materials show definite advantages over other smart materials, e.g. conventional thermal shape memory materials, in terms of displacement and speed. The principle behind the magnetic field induced strain (MFIS) is the strong coupling between magnetization and lattice structure. The investigation of both static and dynamic magnetic domain structures in MSM materials is a key step in optimizing the properties for future possible devices. In this work, optical polarization microscopy is applied to investigate the twin boundary and magnetic domain wall motion in bulk NiMnGa single crystals. Surface magnetic domain patterns on adjacent sides of bulk crystals are revealed for the first time providing comprehensive information about the domain arrangement inside the bulk and at the twin boundary. The tilting of the easy axis with respect to the sample surface determines the preferable domain size and leads to spike domain formation on the surface. Out-of-plane surface domains extend into the bulk within a single variant, while a twin boundary mirrors the domain pattern from adjacent variants. Furthermore, magnetic domain evolution during twin boundary motion is observed. The partial absence of domain wall motion throughout the process contradicts currently proposed models. The magnetic state alternates along a moving twin boundary. With the abrupt nucleation of the second variant this leads to the formation of sections of magnetically highly charged head-on domain structures at the twin boundaries. On the other hand, a dynamic actuation experimental setup, which is capable to provide high magnetic fields in a wide range of frequency, was developed in the course of this study. The observation of reversible twin boundary motion up to 600 Hz exhibits the dependence of strain, hysteresis, and twin boundary velocity on the actuation speed. MFIS increases with frequency, while the onset field is similar in all observed cases. Twin boundary mobility enhancement by fast twin boundary motion is proposed to explain the increase in MFIS. The twin boundary velocity is shown to be inversely proportional to the twin boundary density. No limit of twin boundary velocity is observed in the investigated frequency range.

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Title from PDF of title page. / Document formatted into pages; contains 88 pages. / Thesis (M.S.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: In this work, a multi dimensional RF MEMS variable capacitor that utilizes electrostatic actuation is designed and fabricated on a 425um thick silicon substrate. Electrostatic actuation is preferred over other actuation mechanisms due to low power consumption. The RF MEMS variable capacitor is designed in a CPW topology, with multiple beams supported (1 - 7 beams) on a single pedestal. The varactors are fabricated using surface micromachining techniques. A 1um thick silicon monoxide (Er - 6) is used as a dielectric layer for the varactor. The movable membrane is suspended on a 2.5um thick electroplated gold pedestal. The capacitance between the membrane and the bottom electrode increases as the bias voltage between the membrane and the bottom electrode is increased, eventually causing the membrane to snap down at the actuation voltage. For the varactors designed herein, the actuation voltage is approximately 30 - 90V. / ABSTRACT: Full-wave electromagnetic simulations are performed from 1 - 25GHz to accurately predict the frequency response of the varactors. The EM simulations and the measurement results compare favorably. A series RLC equivalent circuit is used to model the varactor and used to extract the parasitics associated with the capacitor by optimizing the model with the measurement results. The measured capacitance ratio is approximately 12:1 with a tuning range from 0.5 - 6pF. Furthermore, the measured S-parameter data is used to extract the unloaded Q of the varactor (at 1GHz) and is found to be 234 in the up state and 27 in the down state. An improved anodic bonding technique to bond high resistivity Si substrate and low alkali borax glass substrate that finds potential application towards packaging of MEMS varactors is investigated. To facilitate the packaging of the varactors the temperature is maintained at 400°C. The bonding time is approximately 7min at an applied voltage of 1KV. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Electrowetting on dielectric (EWOD) is a technique for reducing the apparent contact angle of a fluid droplet, which has many promising applications in the fields of optics, digital displays, and lab-on-a-chip research. In this thesis, a design is presented for a novel single circuit device for achieving continuous droplet motion, by using the current-rectifying properties of valve metals to create diode-like behavior. This contrasts with existing designs, which require an array of individual electrodes to achieve motion in discrete steps. We are able to demonstrate continuous droplet motion across a 28mm-long test strip with an applied voltage of 303 V and a velocity of 5.59 mm/s (at 370 V) using an ionic-fluid electrolyte (BMIM-PF6), and have achieved actuation at as low as 185 V, with a maximum observed velocity (at 300 V) of 13.8 mm/s using a 1M sodium sulfate solution.

The purpose of this project is to design and manufacture a high precision machine to directly measure the surface force of fluids. Knowing how to move droplets easier with less resistance can increase the potential of a wide range of applications and improve the performance of things such as self-assembly applications. This machine has the ability to measure forces of up to 100 N with a MEMS based sensor. The motion system on this machine moves a substrate underneath of a droplet for 100 mm and applies dragging force to the sensor. It moves with a controlled speed with high accuracy and repeatability. The machine also consists of three manual, three axis controls for positioning key components for observation, control of the air vacuum lifter, and adjustment of the sensor position. There is also an enclosure box that provides visibility to operate and protects the inside environment from dirt during process and also by applying positive air flow during setting up with open windows. The test components were designed to provide maximum flexibility to adjust the setup. A camera in the machine contributes to collect data during the test progress and has the ability to capture pictures and record videos.

The development of a Magneto-hydrodynamics (MHD) numerical tool to study high density thermal plasmas in plasma acceleration devices is presented. The MHD governing equations represent eight conservation equations for the evolution of density, momentum, energy and induced magnetic fields in a plasma. A matrix-free implicit method is developed to solve these conservation equations within the framework of an unstructured grid finite volume formulation. The analytic form of the convective flux Jacobian is derived for general unstructured grids. A Lower Upper Symmetric Gauss Seidel (LU-SGS) technique is developed as part of the implicit scheme. A coloring based algorithm for parallelization of this technique is also presented and its computational efficiency is compared with a global matrix solve technique that uses the GMRES (Generalized Minimum Residual) algorithm available in the PETSc (Portable Extensible Toolkit for Scientific computation) libraries. The verification cases used for this study are the MHD shock tube problem in one, two and three dimensions, the oblique shock and the Hartmann flow problem. It is seen that the matrix free method is comparatively faster and shows excellent scaling on multiple cores compared to the global matrix solve technique. The numerical model was thus verified against the above mentioned standard test cases and two application problems were studied. These include the simulation of plasma deflagration phenomenon in a coaxial plasma accelerator and a novel high speed flow control device called the Rail Plasma Actuator (RailPAc). Experimental studies on coaxial plasma accelerators have revealed two different modes of operation based on the delay between gas loading and discharge ignition. Longer delays lead to the detonation or the snowplow mode while shorter delays lead to the relatively efficient stationary or deflagration mode. One of the theories that explain the two different modes is based on plasma resistivity. A numerical modeling study is presented here in the context of a coaxial plasma accelerator and the effect of plasma resistivity is dealt with in detail. The simulated results pertaining to axial distribution of radial currents are compared with experimental measurements which show good agreement with each other. The simulations show that magnetic field diffusion is dominant at lower conductivities which tend to form a stationary region of high current density close to the inlet end of the device. Higher conductivities led to the formation of propagating current sheet like features due to greater convection of magnetic field. This study also validates the theory behind the two modes of operation based on plasma resistivity. The RailPAc (Rail Plasma Actuator) is a novel flow control device that uses the magnetic Lorentz forces for fluid flow actuation at atmospheric pressures. Experimental studies reveal actuation ~ 10-100 m/s can be achieved with this device which is much larger than conventional electro-hydrodynamic (EHD) force based plasma actuators. A magneto-hydrodynamics simulation study of this device is presented. The model is further developed to incorporate applied electric and magnetic fields seen in this device. The snowplow model which is typically used for studying pulsed plasma thrusters is used to predict the arc velocities which agrees well with experimental measurements. Two dimensional simulations were performed to study the effect of Lorentz forcing and heating effects on fluid flow actuation. Actuation on the order of 100 m/s is attained at the head of the current sheet due to the effect of Lorentz forcing alone. The inclusion of heating effects led to isotropic blast wave like actuation which is detrimental to the performance of RailPAc. This study also revealed the deficiencies of a single fluid model and a more accurate multi-fluid approach is proposed for future work. / text

A MEMS-based micro-electro-discharge machining technique that is enabled by the actuation of micromachined planar electrodes defined on the surfaces of the workpiece is developed that eliminates the need of numerical control machines. First, the planar electrodes actuated by hydrodynamic force is developed. The electrode structures are defined by patterning l8-µm-thick copper foil laminated on the stainless steel workpiece through an intermediate photoresist layer and released by sacrificial etching of the resist layer. The planer electrodes are constructed to be single layer structures without particular features underneath. All the patterning and sacrificial etching steps are performed using dry-film photoresists towards achieving high scalability of the machining technique to large-area applications. A DC voltage of 80-140 V is applied between the electrode and the workpiece through a resistance-capacitance circuit that controls the pulse energy and timing of spark discharges. The parasitic capacitance of the electrode structure is used to form a resistance capacitance circuit for the generation of pulsed spark discharge between the electrode and the workpiece. The suspended electrodes are actuated towards the workpiece using the downflow of dielectric machining fluid, initiating and sustaining the machining process. Micromachining of stainless steel is experimentally demonstrated with the machining voltage of 90V and continuous flow of the fluid at the velocity of 3.4-3.9 m/s, providing removal depth of 20 µm. The experimental results of the electrode actuation match well with the theoretical estimations. Second, the planar electrodes are electrostatically actuated towards workpiece for machining. In addition to the single-layer, this effort uses double-layer structures defined on the bottom surface of the electrode to create custom designed patterns on the workpiece material. The suspended electrode is electrostatically actuated towards the wafer based on the pull-in, resulting in a breakdown, or spark discharge. This instantly lowers the gap voltage, releasing the electrode, and the gap value recovers as the capacitor is charged up through the resistor. Sequential pulses are produced through the self-regulated discharging-charging cycle. Micromachining of the stainless-steel wafer is demonstrated using the electrodes with single-layer and double-layer structures. The experimental results of the dynamic built-capacitance and mechanical behavior of the electrode devices are also analyzed.

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This Ph.D. thesis presents the design, modeling, optimization, prototyping, and experimental methodologies for a novel actuation system for the synchronized segmentally interchanging pulley transmission system (SSIPTS). The SSIPTS is an improved transmission which offers the combined benefits of existing transmission systems for the automotive, the power generation, and the heating, ventilation, and air conditioning (HVAC) industries. As a major subsystem of the SSIPTS, the Pulley Segment Actuation System (PSAS) plays a critical role in the SSIPTS operation and success. However, the overall design of the SSIPTS and its operation principle introduce very challenging and conflicting design requirements for PSASs that the existing actuation technologies cannot meet. To address the lack of actuation technologies for the PSAS application, this research proposes a unique actuation system that meets all the challenging design requirements of the PSAS. This new actuation system is based on the electromagnetic moving coil actuator (MCA) technology. The proposed system is conceptualized and modeled. The key parameters of the actuation system are defined following the conceptual design and modeling. Further, the geometry mapping optimization and the FEM analysis are conducted to determine the optimized values for the key design parameters. From the simulation results, the optimized actuator is shaped. Moreover, a proper control strategy is proposed for the motion of the actuator. Experiments are performed to find the empirical parameters of the actuator, to validate the proposed design, and to test the performance of the actuator. Experimental results show that the prototype of the actuation system meets the design requirements and is feasible for implementation in the SSIPTS. The main contribution of this thesis is to develop a highly efficient and reliable ultra fast bi-stable actuation system for the PSAS for the SSIPTS. As an ultra fast bistable actuation system, the designed actuation system has many advantages over other types of actuation systems: higher load capacity, smaller dimensions, and good controllability. These performance characteristics make the designed actuation system an excellent candidate in applications requiring fast transient response, high precision, and high load capacity such as electromagnetic valve actuators for engines, high speed pick and place, and precise positioning.

This Ph.D. thesis presents the design, modeling, optimization, prototyping, and experimental methodologies for a novel actuation system for the synchronized segmentally interchanging pulley transmission system (SSIPTS). The SSIPTS is an improved transmission which offers the combined benefits of existing transmission systems for the automotive, the power generation, and the heating, ventilation, and air conditioning (HVAC) industries. As a major subsystem of the SSIPTS, the Pulley Segment Actuation System (PSAS) plays a critical role in the SSIPTS operation and success. However, the overall design of the SSIPTS and its operation principle introduce very challenging and conflicting design requirements for PSASs that the existing actuation technologies cannot meet. To address the lack of actuation technologies for the PSAS application, this research proposes a unique actuation system that meets all the challenging design requirements of the PSAS. This new actuation system is based on the electromagnetic moving coil actuator (MCA) technology. The proposed system is conceptualized and modeled. The key parameters of the actuation system are defined following the conceptual design and modeling. Further, the geometry mapping optimization and the FEM analysis are conducted to determine the optimized values for the key design parameters. From the simulation results, the optimized actuator is shaped. Moreover, a proper control strategy is proposed for the motion of the actuator. Experiments are performed to find the empirical parameters of the actuator, to validate the proposed design, and to test the performance of the actuator. Experimental results show that the prototype of the actuation system meets the design requirements and is feasible for implementation in the SSIPTS. The main contribution of this thesis is to develop a highly efficient and reliable ultra fast bi-stable actuation system for the PSAS for the SSIPTS. As an ultra fast bistable actuation system, the designed actuation system has many advantages over other types of actuation systems: higher load capacity, smaller dimensions, and good controllability. These performance characteristics make the designed actuation system an excellent candidate in applications requiring fast transient response, high precision, and high load capacity such as electromagnetic valve actuators for engines, high speed pick and place, and precise positioning.