Design and Fabrication of Electrostatically Actuated Serpentine-Hinged Nickel-Phosphorous Micromirror Devices

A process for micromachining of micro-mirror devices from silicon-on-insulator wafers was proposed and implemented. Test methods and force applicators for these devices were developed. Following successful fabrication of these devices, a novel process for fabrication of devices out of the plane of the silicon wafer was proposed, so that the devices could be actuated electrostatically. In particular, the process makes use of thick photoresist layers as a sacrificial mold into which an amorphous nickel-phosphorous alloy may be deposited. Ideal design of the electrostatically actuated micro-mirrors was investigated, and a final design was selected and modeled using FEA software, which found that serpentine-hinged devices require approximately 33% of the actuation force of their straight-beamed counterparts. An aqueous electroless plating solution composed of nickel acetate, sodium hypophosphite, citric acid, ammonium acetate, and Triton X-100 in was developed for use with the process, and bath operating parameters of 85°C and 4.5 pH were determined. However, this electroless solution failed to deposit in the presence of the photoresist. Several mechanisms proposed for deposition failure included leaching of organic solvents from the photoresist, oxidation of the nickel-titanium seed layer on which the deposition was intended to occur, and nonlinear diffusion of dissolved oxygen in the solution

Study and development of a magnetic steering system for microrobots

In a close future micro-scaled untethered robots might be able to access small spaces inside the human body, currently reachable only by using invasive surgical methods, thus revolutionizing future medicine. The aim of this Master Thesis work is to study and develop a system that can exploit static magnetic fields and gradients to steer purpose-developed microrobots. A concept of the device for the generation of magnetic fields is first elaborated, moving from the state-of-art systems based on Helmholtz and Maxwell coils, which can generate, respectively, nearly uniform magnetic fields and gradients. A uniform magnetic field can be used to orient a magnetic or magnetisable object, aligning it with the direction of the field, while a uniform magnetic gradient can be used to shift such an object. The developed system is formed by two coils in the Maxwell geometrical configuration and independently powered in order to generate a uniform magnetic gradient, a quasi-uniform magnetic field or a superimposition of the two, reducing the overall complexity of the hardware with respect to the systems also employing Helmholtz coils. An analytical model of the on-axis magnetic field generated by the device and a finite element model of the field in the workspace are developed. Three microrobot prototypes are then considered: a millimetre-sized NdFeB cylindrical permanent magnet, which allows to test the maximum performances of the developed device, a polymeric microbead, which is more compatible with biomedical applications but less reactive to magnetic fields than a permanent magnet, and a polymeric nanofilm, which allows to test the steering of very anisotropic shapes, both containing iron oxide nanoparticles. Models of their interaction with magnetic fields are presented. Furthermore, a model of the motion of the three prototypes employing the developed magnetic device is presented. The experimental set up is described, including the two coils and their support backing, the monitoring and powering circuitry and a software kit containing four graphical user interfaces for the calibration and validation of the system. After a set of trials performed for the calibration of the magnetic-field-generating device, the system is tested in steering the microrobot prototypes. The extrapolated data are compared to the behaviours predicted by the magnetic motion models. The abilities of the magnetic steering system and its main limits are finally examined, suggesting possible improvements of both the magnetic device and the microrobots in order to enhance their control and manipulation. In particular indications for developing the next-generation of wireless magnetically-actuated microrobots and the relative steering systems are extrapolated

Bioinspired Control of Rudderless Morphing UAVs

Morphing to seamlessly alter aircraft geometry for either multi-mission or adaptive fly-by-feel flight has recently become an emerging field of research. With the added benefits of tailored aerodynamics, an aircraft no longer needs to be designed to suit a single cruise flight condition. This is particularly useful for small Unmanned Aerial Vehicles (UAVs) which, like birds and insects, tend to operate at lower altitudes and even in urban environments where the flow can frequently change drastically. The primary objective of this research is to investigate morphing applications for rudderless UAVs, which have seldom been studied prior to this point, through bioinspiration. As natural fliers undergo multi-scale low-altitude morphing to adapt to changes in either flight objective or aerodynamic conditions, they are prime subjects for investigation. This is accomplished through both analytical aerodynamic modeling, and experimental design and investigation of novel morphing actuators using Macro Fiber Composites (MFCs). Using these smart material actuators, complex shape change such as spanwise camber morphing and three-dimensional bending-twisting coupling is achieved. This dissertation presents three main contributions to the field of morphing aircraft. The first contribution is an analytical derivation that assesses the impact of scale and altitude on flight. This is aimed at justifying the need for morphing technologies particularly at the UAV scale by assessing the impact of winds on flight velocity and direction. More specifically, both a steady wind and a quasi-steady sharp-edge cross wind were assessed to characterize the response, and showed that low-altitude fliers are prone to drastic changes in flight path, acceleration, and sensitivity with respect to winds. A nonlinear Lifting Line Theory (LLT) model was also developed specifically for spanwise morphing aircraft. With this model, the spanwise geometry of a morphing wing can be tailored and optimized to achieve a desired aerodynamic outcome. As this model is capable of characterizing nonlinear aerodynamics, the spanwise wing geometry is tailored to recover from stall. A comprehensive analysis of possible adaptation scenarios is also conducted to characterize the limitations of the system and demonstrated excellent recovery capabilities of the spanwise morphing wing. Lastly, a novel bioinspired tail actuator is developed for multifunctional pitch and yaw control using MFCs. Two Finite Element Method (FEM) models are compared to determine both an appropriate method of modeling MFC actuators with custom non-rectangular geometries and fiber orientations, and the optimal fiber orientation to obtain adequate transverse and out-of-plane displacements. The optimized actuator was integrated into a bioinspired aircraft for wind tunnel testing. Experimental investigation was geared towards quantifying both pitch and yaw response of the actuator with respect to both changes in angle of attack and sideslip.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145843/1/llgamble_1.pd

Shape Memory Alloy for Adaptive Optics

Shape memory alloys (SMAs) are smart materials that, upon deformation, return to their original shape when heated above a temperature threshold. This special behaviour makes SMAs very attractive as effcient strain/force actuators with very large strains (up to 8%). For this reason, SMAs have been widely used in several applications, from surgery to space. In thesis work, we considered the use of SMAs to build a deformable lens, i.e. a lens with tunable focal length. Usually, optical systems are realized by using optical components such as lenses and mirrors that have fixed optical power (focal length) and that sometimes can be moved, as it occurs in zoom systems. In such cases the movements are achieved manually or by using motors that are slow and subjected to mechanical wear. More recently, optical elements with variable focal length, hence called "adaptive" have been developed, allowing for a great simplification in optical design. Among all the available materials used for actuation, SMAs possess a higher strain with respect to the common actuation materials used to build deformable lenses (such as the piezoelectric). Moreover, they don't need high actuation voltages and, by using SMA wires, allow to realize very small actuators, and consequently very compact devices. Herein, we demonstrate that SMA wires can be efficiently employed for developing lenses with variable focal length with small dimensions, easily embeddable in wearable optics

Design of three degrees-of-freedom motion stage for micro manipulation

A miniaturized translational motion stage has potentials to provide not only performances equivalent to conventional motion stages, but also additional features from its small form factor and low cost. These properties can be utilized in applications requiring a small space such as a vacuum chamber in a scanning electron microscopy (SEM), where hidden surface can decrease by manipulating objects to measure. However, existing miniaturized motion stages still have several cm3 level volumes and provide simple operations. In this dissertation, Micro-electro-mechanical systems (MEMS)-based motion stages are utilized to replace a miniaturized motion stage for micro-scale manipulation and possible applications. However, most MEMS fabrication methods remain in monolithic fabrication methods and a lot of MEMS based multiple degrees-of-freedom (DOFs) motion stage also remain for in-plane motions. In this dissertation, a nested structure based on a serial kinematic mechanism is implemented in order to overcome these constraints and implement out-of-plane motion, where one independent stage is embedded into the other individual stage with additional features for structurally and electrically isolations among the engaged stages. MEMS actuators and displacement amplifiers are also investigated for reasonable performance. 3-axis motions are divided into two in-plane motions and one out-of-plane motion; an in-plane 1 DOF motion stage (called an X-stage) and one out-of-plane 1 DOF motion stage (called a Z-stage) are designed and characterized experimentally. Based on the two stages, the XY-stage is designed by merging one X-stage into the motion platform of the other X-stage with a different orientation (called an XY-stage). With this nested approach, the fabricated XY-stage demonstrated in-plane motions larger than 50 µm with ignorable coupled motion errors. Based on this nested approach, the 3-axis motion stage is also implemented by utilizing the nested structure twice; integrating the Z-stage with the motion platform of the XY-stage (called an XYZ-stage). The XYZ-stage demonstrated out-of-plane motions about 23 µm as well as the in-plane motions. Two presented motion stages have been utilized in the manipulation of micro-scale object by the cooperation of the two XY-stages inside a SEM chamber. The large motion platform of the X-stage is also utilized in a parallel plate type rheometer to measure the material properties of viscoelastic materials

Space construction data base

Construction of large systems in space is a technology requiring the development of construction methods to deploy, assemble, and fabricate the elements comprising such systems. A construction method is comprised of all essential functions and operations and related support equipment necessary to accomplish a specific construction task in a particular way. The data base objective is to provide to the designers of large space systems a compendium of the various space construction methods which could have application to their projects