Design and Simulation of a MEMS Long Distance Traveling Micro-Actuator

This thesis is primarily concerned with the design, synthesis, modeling, and simulation of a linear micro-actuator that is able to travel relatively long distances upon the application of a bias voltage. The theoretical investigation addresses the functionality of this device in a certain setting given fixed and variable parameters. The objective of this investigation is to lay out a mathematical model, which explains the physics behind the workings of this device. It is not the objective of this investigation to study all the possible different scenarios that would result by changing certain or all the variable parameters, rather to prove that the concept of a traveling linear micro-actuator is sound. Furthermore, demonstrate that this device is functional to the specifications to which it was designed. The theoretical analysis was very critical in determining reasonable approximations for the parameters and dimensions of the device used to design the layout, and the process flow necessary for the fabrication process. The detailed explanation of each fabrication step is described in this thesis. The theoretical analysis shows that this linear micro-actuator, which has a relatively similar function to a parallel comb drive, can operate due to the electrostatic force generated upon the application of a bias voltage. This analysis, also, demonstrates that several other parameters have a direct effect on the performance of the device. Parameters, such as the thickness, the width, and the length of the electrodes are mathematically proven to change the magnitude of the electrostatic force responsible for the generation of the motion of the moving part of the micro-actuator. This device is comprised of two main components: a conductive fixed support, which works as a fixed electrode, and a moving electrode that would slide over this support and works as a shuttle. It is expected that the shuttle could be used in different applications as a transportation tool for other MEMS components or devices

Design, Fabrication, Processing, and Testing of Micro-Electro-Mechanical Chemical Sensors

Chemical microsensors are a new field integrating chemical thin film technology with solid-state fabrication techniques to make devices capable of detecting chemicals in the environment. This thesis evaluated commercially available fabrication processes and numerous sensor designs for working chemical sensors. The commercial processes used were MUMPS for surface micromachined devices and MOSIS for bulk micromachined devices. Overall, eight fabrication runs and 29 different designs were made. Of these designs, two were shown to work effectively. Other designs failed due to fabrication problems and design errors that caused release problems. One design that worked was a surface micromachined chemoresistor with interdigitated gold sensing fingers and a polysilicon heater. The other design was a bulk micromachined suspended bridge structure with bimorphic action drivers at each end. Thin films were also investigated to determine which would have the most affinity to specific chemicals and therefore provide measurable responses. Once selected, a technique was developed to apply the thin film in such a way as not to damage the devices. Several thin films were identified for application, but only two polymers, poly(isobutylene) and poly(vinyl tetrachloride), were successfully applied and tested. Because the sensing devices were released micro-electro-mechanical structures, they were extremely susceptible to forces and could be damaged easily. This thesis showed that released MEMS devices could be subjected to a complete photolithographic process including spin-coating, baking, exposure, and development without damage. A hybrid mask process was developed that used photoresist to expose sensing areas for thin film deposition, bond pads for packaging, and a physical mask to cover regions and bond pads during the actual film application

Control and Characterization of Line-Addressable Micromirror Arrays

This research involved the design and implementation of a complete line-addressable control system for a 32x32 electrostatic piston-actuated micromirror array device. Line addressing reduces the number of control lines from N2 to 2N making it possible to design larger arrays and arrays with smaller element sizes. The system utilizes the electromechanical bi-stability of individual elements to bold arbitrary bi-stable phase patterns. The control system applies pulse width modulated (PWM) signals to the rows and columns of the micromirror array. Three modes of operation were conceived and built into the system. The first was the traditional signal scheme which requires the array to be reset before a new pattern can be applied. The second is an original scheme that allows dynamic switching between bi-stable patterns. The third and final mode applies an effective voltage ramp across the device by operating above mechanical cutoff. Device characterization and control system testing were conducted on predesigned and prefabricated samples from two different foundry processes. Testing results showed that the control system was successfully integrated. However, bi-stable control of individual mirror elements was not successfully demonstrated on samples due to flaws in the device design. A more robust device design which corrects these flaws and increases operational yield is proposed

Modeling of magnetic field driven simultaneous assembly

The Magnetic Field Driven Simultaneous Assembly (MFDSA) is a method that offers a non-statistical and deterministic solution to the problem of assembly via batch processing; a hybrid of serial and parallel processing. The technique requires the use of electromagnets as well as soft and hard magnetic materials that are applied to devices and recesses respectively. The MFDSA approach offers the ability to check and correct errors in real-time and is capable of scalable, versatile, and high-yield integration. Devices, coated with a layer of soft magnetic material, are moved from initial to final positions along predetermined pathways through the action of an array of electromagnets. Various devices, of arbitrary geometries, with different physical and functional properties, are manipulated simultaneously toward specific desired locations and then dropped onto a template under the influence of gravity by weakening the local applied field. Locations on the template correspond to sites on a substrate that contain recesses. When a number of devices have been dropped onto the template, a substrate is pressed onto it and the soft magnetic layers on the devices adhere to the hard magnetic strips in the recesses, completing integration in a single step. The objectives of this dissertation are the following: to present the MFDSA method; comparing and contrasting it with other extant techniques employed by the semiconductor industry; to discuss key aspects of this solution with respect to the problem of assembly, and to model the calculations involved with determining both device pathways and field interactions that are required to implement the approach. The Fourier Series technique will be used to describe the force of attraction between the device\u27s soft magnetic layer and the recess\u27s hard magnetic strips. Methodology from finite element analysis will be employed to calculate the force exerted on a device by an array of electromagnets. The Swarm Algorithm, which was developed in this work to calculate device pathways, will be presented as a stable, well-defined solution. Other concepts, such as the magnetic retention factor and the collision crosssection area, will be presented and developed. The solution to the problem of assembly, via the Swarm Algorithm, will be compared and contrasted with other analogous problems found in the literature. The results of these models, including software implementation, will be presented

Novel Actuation Mechanisms for MEMS Mirrors

Ph.DDOCTOR OF PHILOSOPH

Electropermanent magnetic connectors and actuators : devices and their application in programmable matter

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 199-206).Programmable matter is a digital material having computation, sensing, and actuation capabilities as continuous properties active over its whole extent. To make programmable matter economical to fabricate, we want to use electromagnetic direct drive, rather than clockwork, to actuate the particles. Previous attempts to fabricate small scale (below one centimeter) robotic systems with electromagnetic direct-drive have typically run into problems with insufficient force or torque, excessive power consumption and heat generation (for magnetic-drive systems), or high-voltage requirements, humidity sensitivity, and air breakdown. (for electrostatic-drive systems) The electropermanent magnet is a solid-state device whose external magnetic flux can be stably switched on and off by a discrete electrical pulse. Electropermanent magnets can provide low-power connection and actuation for programmable matter and other small-scale robotic systems. The first chapter covers the electropermanent magnet, its physics, scaling, fabrication, and our experimental device performance data. The second introduces the idea of electropermanent actuators, covers their fundamental limits and scaling, and shows prototype devices and performance measurements. The third chapter describes the smart pebbles system, which consists of 12-mm cubes that can form shapes by stochastic self-assembly and self-disassembly. The fourth chapter describes the millibot, a continuous chain of programmable matter which forms shapes by folding.by Ara Nerses Knaian.Ph.D

Fabrication and characterization of thin-film electromagnetic coils and heaters for microchannel applications

The focus of this thesis involves developing general fabrication processes relevant to the manufacture of two new devices for the Microscale technology Energy and Chemical Systems (MECS) program at Oregon State University. The two MECS devices developed, capture dots and transparent thin-film heaters (TTFHs), require unique process development for successful manufacture. Thick photolithography is required for the capture dots and its development is detailed. The capture dots also require copper electroplating. The copper electroplating system and process development are detailed. The TTFHs require a unique heater material, indium tin oxide (ITO). The heater deposition utilizes an ultrasonic lift-off method, also detailed. The complete manufacturing process steps of both the capture dots and the TTFHs are described. Both devices are successfully demonstrated and their electrical properties are discussed

Development and characterisation of traceable force measurement for nanotechnology

Traceable low force metrology should be an essential tool for nanotechnology. Traceable measurement of micro- and nanonewton forces would allow independent measurement and comparison on material properties, MEMS behaviour and nanodimensional measurement uncertainties. Yet the current traceability infrastructure in the UK is incomplete. This thesis describes the incremental development of the low force facility at the National Physical Laboratory (NPL). The novel contribution of this thesis has three components. First, specific modifications to the NPL Low Force Balance were undertaken. This involved developing novel or highly modified solutions to address key issues, as well as undertaking detailed comparions with external ans internal traceability references. Second, a triskelion force sensor flexure was proposed and mathematically modelled using both analytical and finite element techniques, and compared to experimentally measured spring constant estimates. The models compared satisfactorily, though fabrication defects in developed prototype artefacts limited the experimental confirmation of the models. Third, a piezoelectric sensor approach for quasistatic force measurement was proposed, experimentally evaluated and rejected. Finally, an improved design for a low force transfer artefact system is presented, harnessing the findings of the reported investigations. The proposed design combines proven strain-sensing technology with the advantageous triskelion flexure, incorporating an external stage and packaging aspects to achieve the requirements for a traceable low force transfer artefact

Designing a New Tactile Display Technology and its Disability Interactions

People with visual impairments have a strong desire for a refreshable tactile interface that can provide immediate access to full page of Braille and tactile graphics. Regrettably, existing devices come at a considerable expense and remain out of reach for many. The exorbitant costs associated with current tactile displays stem from their intricate design and the multitude of components needed for their construction. This underscores the pressing need for technological innovation that can enhance tactile displays, making them more accessible and available to individuals with visual impairments. This research thesis delves into the development of a novel tactile display technology known as Tacilia. This technology's necessity and prerequisites are informed by in-depth qualitative engagements with students who have visual impairments, alongside a systematic analysis of the prevailing architectures underpinning existing tactile display technologies. The evolution of Tacilia unfolds through iterative processes encompassing conceptualisation, prototyping, and evaluation. With Tacilia, three distinct products and interactive experiences are explored, empowering individuals to manually draw tactile graphics, generate digitally designed media through printing, and display these creations on a dynamic pin array display. This innovation underscores Tacilia's capability to streamline the creation of refreshable tactile displays, rendering them more fitting, usable, and economically viable for people with visual impairments