A fabrication process for electrostatic microactuators with integrated gear linkages

A surface micromachining process is presented which has been used to fabricate electrostatic microactuators. These microactuators are interconnected with each other and linked to other movable microstructures by integrated gear linkages. The gear linkages consist of rotational and linear gear structures, and the electrostatic microactuators include curved electrode actuators, comb-drive actuators, and axial-gap wobble motors. The micromechanical structures are constructed from polysilicon. Silicon dioxide was used as a sacrificial layer, and silicon nitride was used for electrical insulation. A cyclohexane freeze drying technique was used to prevent problems with stiction. The actuators, loaded with various mechanisms, were successfully driven by electrostatic actuation. The work is a first step toward mechanical power transmission in micromechanical system

Microsystems technology: objectives

This contribution focuses on the objectives of microsystems technology (MST). The reason for this is two fold. First of all, it should explain what MST actually is. This question is often posed and a simple answer is lacking, as a consequence of the diversity of subjects that are perceived as MST. The second reason is that a map of the somewhat chaotic field of MST is needed to identify sub-territories, for which standardization in terms of system modules an interconnections is feasible. To define the objectives a pragmatic approach has been followed. From the literature a selection of topics has been chosen and collected that are perceived as belonging to the field of MST by a large community of workers in the field (more than 250 references). In this way an overview has been created with `applications¿ and `generic issues¿ as the main characteristics

Development of an axial flux MEMS BLDC micromotor with increased efficiency and power density

This paper presents a rigorous design and optimization of an axial flux microelectromechanical systems (MEMS) brushless dc (BLDC) micromotor with dual rotor improving both efficiency and power density with an external diameter of only around 10 mm. The stator is made of two layers of windings by MEMS technology. The rotor is developed by film permanent magnets assembled over the rotor yoke. The characteristics of the MEMS micromotor are analyzed and modeled through a 3-D magnetic equivalent circuit (MEC) taking the leakage flux and fringing effect into account. Such a model yields a relatively accurate prediction of the flux in the air gap, back electromotive force (EMF) and electromagnetic torque, whilst being computationally efficient. Based on 3-D MEC model the multi-objective firefly algorithm (MOFA) is developed for the optimal design of this special machine. Both 3-D finite element (FE) simulation and experiments are employed to validate the MEC model and MOFA optimization design

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

Microlamination Based Lumped And Distributed Magnetic Mems Systems Enabled By Through-Mold Sequential Multilayer Electrodeposition Technology

Microfabricated magnetic MEMS components such as permanent micromagnets and soft magnetic structures are key enablers in various lumped and distributed systems such as energy harvesters, magnetometers, biomagnetic filters, and electromagnetic micromotors. The unique functionalities of such systems often require designers to controllably scale the relevant dimensions of a device relative to the characteristic length of a targeted application. We demonstrate in this dissertation that the developed Microlamination Technology could create two-dimensional uniform- or dual- height monolithic metallic structures with additional deterministic structural and compositional complexities along thickness direction, suitable to facilely and flexibly fabricate both lumped and distributed magnetic MEMS systems at a designer\u27s will. The utility of the Microlamination Technology is further validated through the realization of two exemplary systems based on this technology: (i) A lumped system of laminated permanent micromagnets. Microfabricated permanent magnets possessing a multilayer structure enabled by the Microlamination Technology that preserves the high energy density of thinner magnetic films, while simultaneously reducing average residual stress of the films and achieving a significant thickness are presented. The key to retain the superior magnetic properties of thin films in thick laminations is the low interface roughness between the layers, which in turn improves the coercivity of the micromagnets. (ii) A distributed system of a bi-stable vertical magnetic actuator with non-contact latching. The utilization of the Microlamination Technology translates the structural periodicity (multilayer) into magnetic-field-pattern periodicity, which in turn enables the bi-stability of the microsystem and leads to the defined latching behavior. The latching mechanism is solely based on the magneto-static interaction without the need of a mechanical stop. No external energy is needed in the latching positions. This vertical bi-stable actuator could have potential applications as valves in micro-fluidic controls, and as integral parts of micro-mirrors in optical applications

Engineering microrobots for targeted cancer therapies from a medical perspective

Systemic chemotherapy remains the backbone of many cancer treatments. Due to its untargeted nature and the severe side effects it can cause, numerous nanomedicine approaches have been developed to overcome these issues. However, targeted delivery of therapeutics remains challenging. Engineering microrobots is increasingly receiving attention in this regard. Their functionalities, particularly their motility, allow microrobots to penetrate tissues and reach cancers more efficiently. Here, we highlight how different microrobots, ranging from tailor-made motile bacteria and tiny bubble-propelled microengines to hybrid spermbots, can be engineered to integrate sophisticated features optimised for precision-targeting of a wide range of cancers. Towards this, we highlight the importance of integrating clinicians, the public and cancer patients early on in the development of these novel technologies

Optical MEMS Switches: Theory, Design, and Fabrication of a New Architecture

The scalability and cost of microelectromechanical systems (MEMS) optical switches are now the important factors driving the development of MEMS optical switches technology. The employment of MEMS in the design and fabrication of optical switches through the use of micromachining fabricated micromirrors expands the capability and integrity of optical backbone networks. The focus of this dissertation is on the design, fabrication, and implementation of a new type of MEMS optical switch that combines the advantages of both 2-D and 3-D MEMS switch architectures. This research presents a new digital MEMS switch architecture for 1×N and N×N optical switches. The architecture is based on a new microassembled smart 3-D rotating inclined micromirror (3DRIM). The 3DRIM is the key device in the new switch architectures. The 3DRIM was constructed through a microassembly process using a passive microgripper, key, and inter-lock (PMKIL) assembly system. An electrostatic micromotor was chosen as the actuator for the 3DRIM since it offers continuous rotation as well as small, precise step motions with excellent repeatability that can achieve repeatable alignment with minimum optical insertion loss between the input and output ports of the switch. In the first 3DRIM prototype, a 200×280 microns micromirror was assembled on the top of the electrostatic micromotor and was supported through two vertical support posts. The assembly technique was then modified so that the second prototype can support micromirrors with dimensions up to 400×400 microns. Both prototypes of the 3DRIM are rigid and stable during operation. Also, rotor pole shaping (RPS) design technique was introduced to optimally reshape the physical dimensions of the rotor pole in order to maximize the generated motive torque of the micromotor and minimize the required driving voltage signal. The targeted performance of the 3DRIM was achieved after several PolyMUMPs fabrication runs. The new switch architecture is neither 2-D nor 3-D. Since it is composed of two layers, it can be considered 2.5-D. The new switch overcomes many of the limitations of current traditional 2-D MEMS switches, such as limited scalability and large variations in the insertion loss across output ports. The 1×N MEMS switch fabric has the advantage of being digitally operated. It uses only one 3DRIM to switch the light signal from the input port to any output port. The symmetry employed in the switch design gives it the ability to incorporate a large number of output ports with uniform insertion losses over all output channels, which is not possible with any available 2-D or 3-D MEMS switch architectures. The second switch that employs the 3DRIM is an N×N optical cross-connect (OXC) switch. The design of an N×N OXC uses only 2N of the 3DRIM, which is significantly smaller than the N×N switching micromirrors used in 2-D MEMS architecture. The new N×N architecture is useful for a medium-sized OXC and is simpler than 3-D architecture. A natural extension of the 3DRIM will be to extend its application into more complex optical signal processing, i.e., wavelength-selective switch. A grating structures have been selected to explore the selectivity of the switch. For this reason, we proposed that the surface of the micromirror being replaced by a suitable gratings instead of the flat reflective surface. Thus, this research has developed a rigorous formulation of the electromagnetic scattered near-field from a general-shaped finite gratings in a perfect conducting plane. The formulation utilizes a Fourier-transform representation of the scattered field for the rapid convergence in the upper half-space and the staircase approximation to represent the field in the general-shaped groove. This method provides a solution for the scattered near-field from the groove and hence is considered an essential design tool for near-field manipulation in optical devices. Furthermore, it is applicable for multiple grooves with different profiles and different spacings. Each groove can be filled with an arbitrary material and can take any cross-sectional profile, yet the solution is rigorous because of the rigorous formulations of the fields in the upper-half space and the groove reigns. The efficient formulation of the coefficient matrix results in a banded-matrix form for an efficient and time-saving solution

Gnat Robots (And How They Will Change Robotics)

A new concept in mobile robots is proposed, namely that of a gnat-sized autonomous robot with on-board sensors, brains, actuators and power supplies, all fabricated on a single piece of silicon. Recent breakthroughs in computer architectures for intelligent robots, sensor integration algorithms and micromachining techniques for building on-chip micromotors, combined with the ever decreasing size of integrated logic, sensors and power circuitry have led to the possibility of a new generation of mobile robots which will vastly change the way we think about robotics. Forget about today's first generation robots: costly, bulky machines with parts acquired from many different vendors. What will appear will be cheap, mass produced, slimmed down, integrated robots that need no maintenance, no spare parts, and no special care. The cost advantages of these robots will create new worlds of applications. Gnat robots will offer a new approach in using automation technology. We will begin to think in terms of massive parallelism: using millions of simple, cheap, gnat robots in place of one large complicated robot. Furthermore, disposable robots will even become realistic. This paper outlines how to build gnat robots. It discusses the technology thrusts that will be required for developing such machines and sets forth some strategies for design. A close look is taken at the tradeoffs involved in choosing components of the system: locomotion options, power sources, types of sensors and architectures for intelligence.MIT Artificial Intelligence Laborator