Single Substrate Electromagnetic Actuator

A microvalve which utilizes a low temperature ( <300° C.) fabrication process on a single substrate. The valve uses buckling and an electromagnetic actuator to provide a relatively large closing force and lower power consumption. A buckling technique of the membrane is used to provide two stable positions for the membrane, and to reduce the power consumption and the overall size of the microvalve. The use of a permanent magnet is an alternative to the buckled membrane, or it can be used in combination with the buckled membrane, or two sets of micro-coils can be used in order to open and close the valve, providing the capability for the valve to operate under normally opened or normally closed conditions. Magnetic analysis using ANSYS 5.7 shows that the addition of Orthonol between the coils increases the electromagnetic force by more than 1.5 times. At a flow rate of 1 mL/m, the pressure drop is < 100 Pa. The maximum pressure tested was 57 kPa and the time to open or close the valve in air is under 100 ms. This results in an estimated power consumption of 0.1 mW.Georgia Tech Research Corp

Additively manufacturable micro-mechanical logic gates.

Early examples of computers were almost exclusively based on mechanical devices. Although electronic computers became dominant in the past 60 years, recent advancements in three-dimensional micro-additive manufacturing technology provide new fabrication techniques for complex microstructures which have rekindled research interest in mechanical computations. Here we propose a new digital mechanical computation approach based on additively-manufacturable micro-mechanical logic gates. The proposed mechanical logic gates (i.e., NOT, AND, OR, NAND, and NOR gates) utilize multi-stable micro-flexures that buckle to perform Boolean computations based purely on mechanical forces and displacements with no electronic components. A key benefit of the proposed approach is that such systems can be additively fabricated as embedded parts of microarchitected metamaterials that are capable of interacting mechanically with their surrounding environment while processing and storing digital data internally without requiring electric power

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

Development of the technological process for the production of the electrostatic curved beam actuator for pneumatic microvalves

This work focuses on the development of an effective technological process for the production of the electrostatic curved beam actuator capable to be used as a driving element in different devices such as microswitches or microvalves. Main attention was drawn to the investigation of electroplating technique as a critical process in the microactuator fabrication as well as to the design of the actuator. In addition, usability of ceramic substrates for the microactuator and microvalve production was examined. The idea behind it was that ceramic substrates can be preprocessed and delivered already with necessary electrical connections on it. This would make the entire production process simpler and cheaper. Several types of polished alumina (Al2O3) substrates were used for this purpose. Electrostatic actuation principle was chosen for its good scaling properties to small dimensions, low power consumption, smaller size and higher switching speed. Curved shape of the actuator allows to reduce its pull-in voltage and thus to increase the amplitude of motion as compared to the parallel-plate structures. The material of the actuator is nickel. It was chosen for its good mechanical properties and relative simplicity of processing. Double layer nickel electroplating was used to produce the microactuator. The layers have different stress gradients controlled by current density during the electroplating process, making it possible to achieve the desired bending of the structure. Compared to bimetallic bending cantilever actuators, the curvature of the single-metal beam is less dependable on temperature and aging. Thus, more stable performance under changing working conditions was ensured. In order to avoid sticking of the microactuator to the isolation layer in the closed state, an array of stand-off bumps was added on the back-side of the beam. These bumps reduce the contact area and increase the distance between the actuator and the isolation layer. Fifteen design variants of the actuator differing in length and width were fabricated in order find the most effective solution for given system requirements. Based on the actuators technological process developed in this work, a simple electrostatic microvalve was designed and produced. Final variants of microvalve were fabricated on a standard 380 µm thick silicon wafer. Gas inlet channel as well as the electrodes and the actuator itself are all placed on the same substrate in order to reduce the size and cost of the system. During characterization, mechanical stability of the actuators and microvalves were studied by means of drop, temperature and shear tests in order to prove the reliability of the system. System performance tests proved stable pull-in voltages from 8,6 V to 11,6 V. Maximal gas flow through the valve was 110±5 ml/min at applied differential pressure of 2 bar

A study on buckled-beam actuators for RF MEMS applications

When combined with MEMS actuators, a mechanical lock is a useful device for various applications including memory cells, micro-relays, micro-valves, optical switches, and digital micro-mirrors. It allows removal of actuation force during idle periods without affecting an actuated state of a device, which makes standing power consumption completely unnecessary. In this thesis, a bistable buckled-beam actuator for RF MEMS switch applications has been examined. The buckled-beam geometry was designed based upon theoretical analysis. It was fabricated by SU-8 lithography and copper pulse electroplating. It was actuated by the Lorentz force using external magnet and current flow through the beam. Measured switching currents (10 to 200 mA) agree well with theoretical values. Required actuation voltage was less than 0.4 V for 20 to 60 μm displacement. The developed buckled-beams were incorporated into a RF MEMS switch design. The basic structure of the proposed switch is a combination of a coplanar waveguide and two buckled-beam actuators. The coplanar waveguide has a ground-signal-ground (GSG) configuration and its dimensions were designed for 50 ohm characteristic impedance over broad RF band. The proposed switch has several advantages compared to the conventional capacitive-type RF MEMS switches. First, since the electromagnetic actuation mechanism is adopted in the proposed switch, required actuation voltage is much lower than the electrostatic actuation mechanism. Second, all the structures can be made from the same layer so that only one mask is necessary for the entire process. Third, the trapped charge issue is dramatically diminished because the actuators are separated from the coplanar waveguide, very low voltage is applied to the actuators, and the polarity of voltage on the actuators is continuously toggled. The proposed RF MEMS switch finds a variety of usefulness in RF circuits and systems, including wireless communication devices – antenna switching, T/R (transmitter/receiver) switching, band selection, adjustable gain amplifiers; radar systems for military applications – phase shifters, phased array antennas; measurement equipments – impedance matching circuits, etc

Integrated Magnetic MEMS Relays:Status of the Technology

The development and application of magnetic technologies employing microfabricated magnetic structures for the production of switching components has generated enormous interest in the scientific and industrial communities over the last decade. Magnetic actuation offers many benefits when compared to other schemes for microelectromechanical systems (MEMS), including the generation of forces that have higher magnitude and longer range. Magnetic actuation can be achieved using different excitation sources, which create challenges related to the integration with other technologies, such as CMOS (Complementary Metal Oxide Semiconductor), and the requirement to reduce power consumption. Novel designs and technologies are therefore sought to enable the use of magnetic switching architectures in integrated MEMS devices, without incurring excessive energy consumption. This article reviews the status of magnetic MEMS technology and presents devices recently developed by various research groups, with key focuses on integrability and effective power management, in addition to the ability to integrate the technology with other microelectronic fabrication processes

Magnetic torque obtained using finite element modelling of electromagnetic micro relay / Azahar Taib, Mohamad Adha Mohamad Idin and Nor Azlan Othman

Micro Electromechanical Systems (MEMS) is an area of research and applications that is becoming increasingly popular. One of MEMS device that is becoming increasingly important in a wide range of industries such as the computer industry, the medical industry and the automotive industry is micro relay. Generally, there are three types of micro relay based on actuation methods; electrostatic, electrothermal and electromagnetic. This research project focuses on electromagnetic micro relay. The need to study the magnetic behavior of electromagnetic micro relay is due to ongoing demand in area of micro relay design and fabrication. This study will focus on analyzing the magnetic behaviors of a specific electromagnetic micro relay. It involves the analytical and finite element modeling. The results from these two analyses are compared in order to verify the reliability of results obtained. Prior to the validation, a complete model of micro relay is developed using finite element modeling via ANSYS software. Investigations on magnetic behaviors of the electromagnetic micro relay are performed via Finite Element Analyses. By varying the current density on the EM planar coil on the micro relay structure, the operating principle of electromagnetic micro relay can be simulated and observed. In addition, it also includes the investigation of magnetic torque upon the armature of the micro relay when certain parameters are varied. The parameters are the thickness of the armature, air gap between the permanent magnet and EM planar coil, and the amount of current density applied to EM planar coils. The effect of the parameter's variation are presented and discussed. These results provide a good insight of the magnetic behavior of the investigated electromagnetic micro relay which will be very useful in designing an electromagnetic micro relay

DEVELOPMENT OF NANO/MICROELECTROMECHANICAL SYSTEM (N/MEMS) SWITCHES

Ph.DDOCTOR OF PHILOSOPH

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

MEMS micro-bridge actuator for potential application in optical switching

In this thesis, the development of a novel electro-thermally actuated bi-stable out-of-plane two way actuated buckled micro-bridge for a potential application in optical switching is presented. The actuator consists of a bridge supported by 'legs' and springs at its four corners. The springs and the bridge are made of a tri-layer structure comprising of 2.5µm thick low-stress PECVD oxide, 1µm thick high-stress PECVD oxide and 2µm thick heavily phosphorus doped silicon. The legs, on the other hand, are 2µm thick single layer heavily phosphorus doped silicon. Both legs and springs provide elastically constrained boundary conditions at the supporting ends, without of which important features of the micro-bridge actuator could not have been achieved. This microbridge actuator is designed, simulated using ANSYS, fabricated and tested. The results from the testing have shown a good agreement with analytical prediction and ANSYS simulation. The actuator demonstrated bi-stability, two-way actuation and 31µm out-of-plane movement between the two-states using low voltage drive. Buckled shape model, design method for bi-stability and thermo-mechanical model are developed and employed in the design of the micro-bridge. These models are compared with Finite Element (FE) based ANSYS simulation and measurements from the fabricated micro-bridge and have shown a good agreement. In order to demonstrate the potential application of this actuator to optical switching, ANSYS simulation studies have been performed on a micro-mirror integrated with the micro-bridge actuator. From these studies, the optimum micro-mirror size that is appropriate for the integration has been obtained. This optimal mirror size ensures the important features of the actuator. Mirror fabrication experiments in (110) wafer have been carried out to find out the appropriate compensation mask size for a given etch depth and the suitable wafer thickness that can be used to fabricate the integrated system