Precise motion control of a piezoelectric microgripper for microspectrometer assembly.

International audienceThe Fourier Transform (FTIR) microspectrometer discussed in this paper is an example of a complex Micro-Opto-Electro-Mechanical System (MOEMS) configured as an optical bench on a chip. It is an important benchmark application for microtechnology due to increased demands for the use of miniature wavelength detection instruments in bio, nano and material science. This device can be manufactured using automated microassembly and precision alignment of hybrid silicon and glass components, and in particular, of a micro-beamsplitter cube along 3 rotational degrees of freedom. In this paper, a piezoelectric microgripper with four degrees of freedom was attached to a precision robot in ordre to enhance its dexterity and align the beamsplitter to arcsecond angular tolerance. The modeling and control of the microgripper and the alignment algorithm utilizing a novel spot-Jacobian servoing technique are discussed. Experimental results obtained during joint on-going work in Texas and in France are presented demonstrating the advantage of using the microgripper for optical alignment of the microspectrometer

Analysis of CAD Model-based Visual Tracking for Microassembly using a New Block Set for MATLAB/Simulink.

International audienceMicroassembly is an innovative alternative to the microfabrication process of MOEMS which is quite complex. It usually implies the use of microrobots controlled by an operator. The reliability of this approach has been already confirmed for the micro-optical technologies. However, the characterization of assemblies has shown that the operator is the main source of inaccuracies in the teleoperated microassembly. Therefore, there is a great interest in automating the microassembly process. One of the constraints of automation in microscale is the lack of high precision sensors capable to provide the full information about the object position. Thus, the usage of visual-based feedback represents a very promising approach allowing to automate the microassembly process. The purpose of this paper is to characterize the techniques of object position estimation based on the visual data, i.e. visual tracking techniques from the ViSP library. These algorithms allows to get the 3D object pose using a single view of the scene and the CAD model of the object. The performance of three main types of model-based trackers is analyzed and quantified: edge-based, texture-based and hybrid tracker. The problems of visual tracking in microscale are discussed. The control of the micromanipulation station used in the framework of our project is performed using a new Simulink block set. Experimental results are shown and demonstrate thepossibility to obtain the repeatability below 1 micrometer

Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

NASA Tech Briefs, September 2011

Topics covered include: Fused Reality for Enhanced Flight Test Capabilities; Thermography to Inspect Insulation of Large Cryogenic Tanks; Crush Test Abuse Stand; Test Generator for MATLAB Simulations; Dynamic Monitoring of Cleanroom Fallout Using an Air Particle Counter; Enhancement to Non-Contacting Stress Measurement of Blade Vibration Frequency; Positively Verifying Mating of Previously Unverifiable Flight Connectors; Radiation-Tolerant Intelligent Memory Stack - RTIMS; Ultra-Low-Dropout Linear Regulator; Excitation of a Parallel Plate Waveguide by an Array of Rectangular Waveguides; FPGA for Power Control of MSL Avionics; UAVSAR Active Electronically Scanned Array; Lockout/Tagout (LOTO) Simulator; Silicon Carbide Mounts for Fabry-Perot Interferometers; Measuring the In-Process Figure, Final Prescription, and System Alignment of Large; Optics and Segmented Mirrors Using Lidar Metrology; Fiber-Reinforced Reactive Nano-Epoxy Composites; Polymerization Initiated at the Sidewalls of Carbon Nanotubes; Metal-Matrix/Hollow-Ceramic-Sphere Composites; Piezoelectrically Enhanced Photocathodes; Iridium-Doped Ruthenium Oxide Catalyst for Oxygen Evolution; Improved Mo-Re VPS Alloys for High-Temperature Uses; Data Service Provider Cost Estimation Tool; Hybrid Power Management-Based Vehicle Architecture; Force Limit System; Levitated Duct Fan (LDF) Aircraft Auxiliary Generator; Compact, Two-Sided Structural Cold Plate Configuration; AN Fitting Reconditioning Tool; Active Response Gravity Offload System; Method and Apparatus for Forming Nanodroplets; Rapid Detection of the Varicella Zoster Virus in Saliva; Improved Devices for Collecting Sweat for Chemical Analysis; Phase-Controlled Magnetic Mirror for Wavefront Correction; and Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics

Fabrication of high aspect ratio vibrating cylinder microgyroscope structures by use of the LIGA process

Inertial grade microgyroscopes are of great importance to improve and augment inertial navigation systems based on GPS for industrial, automotive, and military applications. The efforts by various research groups worldwide to develop inertial grade microgyroscopes have not been successful to date. In 1994, the Department of Mechanical Engineering at Louisiana State University and SatCon Technology Corporation (Boston, Massachusetts) proposed a series of shock tolerant micromachined vibrating cylinder rate gyroscopes with aspect ratios of up to 250:1 to meet the needs of inertial navigation systems based on existing conventional vibrating cylinder gyroscopes. Each microgyroscope consisted of a tall thin shell metallic cylinder attached to a substrate at one end and surrounded by four drive- and four sense-electrodes. The proposed drive- and sense-mechanisms were capacitive-force and capacitance-change, respectively. Since the high aspect ratio metallic microgyroscope structures could not be fabricated by using traditional silicon-based MEMS processes, a LIGA-based two layer fabrication process was developed. A wiring layer was constructed by using a combination of thick film photolithography and electroplating (nickel and gold) on a silicon substrate covered with silicon nitride and a tri-layer plating base; aligned X-ray lithography and nickel electroplating were used to build the high aspect ratio cylinders and electrodes. Deficiencies in the LIGA process were also addressed in this research. Three types of X-ray mask fabrication processes for multi-level LIGA were developed on graphite, borosilicate glass and silicon nitride substrates. Stable and reliable gold electroplating methods for X-ray masks were also established. The plating rate and internal stress of deposits were thoroughly characterized for two brands of commercially available sulfite-based gold electroplating solutions, Techni Gold 25E and NEUTRONEX 309. The gaps between the cylinders and electrodes, which are defined by thin PMMA walls during electroplating, were found to be smaller than designed and deformed in many of the microgyroscope structures. The lateral dimensional loss (LDL) and deformation were identified to be related to the overall thickness and lateral aspect ratio (LAR) of the thin PMMA walls

Design, evaluation, and control of nexus: a multiscale additive manufacturing platform with integrated 3D printing and robotic assembly.

Additive manufacturing (AM) technology is an emerging approach to creating three-dimensional (3D) objects and has seen numerous applications in medical implants, transportation, aerospace, energy, consumer products, etc. Compared with manufacturing by forming and machining, additive manufacturing techniques provide more rapid, economical, efficient, reliable, and complex manufacturing processes. However, additive manufacturing also has limitations on print strength and dimensional tolerance, while traditional additive manufacturing hardware platforms for 3D printing have limited flexibility. In particular, part geometry and materials are limited to most 3D printing hardware. In addition, for multiscale and complex products, samples must be printed, fabricated, and transferred among different additive manufacturing platforms in different locations, which leads to high cost, long process time, and low yield of products. This thesis investigates methods to design, evaluate, and control the NeXus, which is a novel custom robotic platform for multiscale additive manufacturing with integrated 3D printing and robotic assembly. NeXus can be used to prototype miniature devices and systems, such as wearable MEMS sensor fabrics, microrobots for wafer-scale microfactories, tactile robot skins, next generation energy storage (solar cells), nanostructure plasmonic devices, and biosensors. The NeXus has the flexibility to fixture, position, transport, and assemble components across a wide spectrum of length scales (Macro-Meso-Micro-Nano, 1m to 100nm) and provides unparalleled additive process capabilities such as 3D printing through both aerosol jetting and ultrasonic bonding and forming, thin-film photonic sintering, fiber loom weaving, and in-situ Micro-Electro-Mechanical System (MEMS) packaging and interconnect formation. The NeXus system has a footprint of around 4m x 3.5m x 2.4m (X-Y-Z) and includes two industrial robotic arms, precision positioners, multiple manipulation tools, and additive manufacturing processes and packaging capabilities. The design of the NeXus platform adopted the Lean Robotic Micromanufacturing (LRM) design principles and simulation tools to mitigate development risks. The NeXus has more than 50 degrees of freedom (DOF) from different instruments, precise evaluation of the custom robots and positioners is indispensable before employing them in complex and multiscale applications. The integration and control of multi-functional instruments is also a challenge in the NeXus system due to different communication protocols and compatibility. Thus, the NeXus system is controlled by National Instruments (NI) LabVIEW real-time operating system (RTOS) with NI PXI controller and a LabVIEW State Machine User Interface (SMUI) and was programmed considering the synchronization of various instruments and sequencing of additive manufacturing processes for different tasks. The operation sequences of each robot along with relevant tools must be organized in safe mode to avoid crashes and damage to tools during robots’ motions. This thesis also describes two demonstrators that are realized by the NeXus system in detail: skin tactile sensor arrays and electronic textiles. The fabrication process of the skin tactile sensor uses the automated manufacturing line in the NeXus with pattern design, precise calibration, synchronization of an Aerosol Jet printer, and a custom positioner. The fabrication process for electronic textiles is a combination of MEMS fabrication techniques in the cleanroom and the collaboration of multiple NeXus robots including two industrial robotic arms and a custom high-precision positioner for the deterministic alignment process

NASA Tech Briefs, November 2004

Topics include: Multifunction Imaging and Spectroscopic Instrument; Position-Finding Instrument Built Around a Magnetometer; Improved Measurement of Dispersion in an Optical Fiber; Probe for Sampling of Interstitial Fluid From Bone; Neuropsychological Testing of Astronauts; Method of Calibration for a Large Cathetometer System; Four-Channel PC/104 MIL-STD-1553 Circuit Board; Improved Method of Locating Defects in Wiring Insulation; Strobe Traffic Lights Warn of Approaching Emergency Vehicles; Improved Timing Scheme for Spaceborne Precipitation Radar; Concept for Multiple-Access Free-Space Laser Communications; Variable Shadow Screens for Imaging Optical Devices; Verifying Diagnostic Software; Initial Processing of Infrared Spectral Data; Activity-Centric Approach to Distributed Programming; Controlling Distributed Planning; New Material for Surface-Enhanced Raman Spectroscopy; Treated Carbon Nanofibers for Storing Energy in Aqueous KOH; Advanced Infant Car Seat Would Increase Highway Safety; Development of Biomorphic Flyers; Second-Generation Six-Limbed Experimental Robot; Miniature Linear Actuator for Small Spacecraft; Process for Making Single-Domain Magnetite Crystals; A New Process for Fabricating Random Silicon Nanotips; Resin-Transfer-Molding of a Tool Face; Improved Phase-Mask Fabrication of Fiber Bragg Gratings; Tool for Insertion of a Fiber-Optic Terminus in a Connector; Nanofluidic Size-Exclusion Chromatograph; Lightweight, Low-CTE Tubes Made From Biaxially Oriented LCPs; Using Redundancy To Reduce Errors in Magnetometer Readings; Compact Instrument for Measuring Profile of a Light Beam; Multilayer Dielectric Transmissive Optical Phase Modulator; Second-Generation Multi-Angle Imaging Spectroradiometer; Real-Time Adaptive Color Segmentation by Neural Networks; Research and Development in Optical Communications; Tests of Multibeam Scintillation Mitigation on Laser Uplinks; and Spaceborne Infrared Atmospheric Sounder

Microlenses for optical microsystems

Tese de doutoramento (Programa Doutoral em Líderes para as Indústrias Tecnológicas)Lenses have been used by mankind for thousands of years for innumerous different reasons and applications. More recently, lenses in the micro scale dimension, so called microlenses (MLs), have been designed and fabricated using semiconductor technology. These new lenses are used for collimation, focusing or imaging and are an appealing alternative for applications where miniaturization and alignment simplicity are important requirements. Moreover, they also opened a large number of new applications for optical structures and, at the same time, reducing the mechanical and electrical complexity of the existing systems. In this context, the presented thesis has as main purposes, the design and development of a process that allows the fabrication of different sized plano-convex MLs with minor intervention on the process parameters. The MLs were fabricated using a photoresist, the AZ4562, through classical photolithography and the thermal reflow process. Another achievement was the fabrication of MLs directly on the surface of a silicon die containing complementary metal–oxide–semiconductor (CMOS) photodiodes (PDs) for quantifying the differences in their photocurrents generation capacity. The MLs’ optimum fabrication process was achieved when a 128k dots per inch (dpi) super high-resolution chrome on soda lime glass 3×3-0.060” photomask was employed. This photomask allows the design pattern to be transferred into the photoresist with very high precision. Nevertheless, for actually obtaining the desired lens profile, it is necessary to apply a thermal treatment to the fabricated microstructures. When the photoresist is submitted to a temperature higher than its glass transition temperature, it softens allowing the shape change to occur. For MLs, the major external force acting during this process is the surface tension. The fabricated MLs were structurally characterized using a profilometer and scanning electron microscope (SEM) images. For measuring the focal length, an optomechanical alignment system was assembled and a difference of just 4% was found between the measured and the theoretical values. An additional improvement was achieved by introducing a rehydration step in the fabrication process. The prebake stage used during the fabrication serves for evaporating the solvent off the photoresist but also, all of its water content. As a result, it was demonstrated that the AZ4562 needs rehydration in order to obtain excellent results by preventing structural damages in the MLs which are crucial for achieving efficient optical properties. The main advantage of this new optimized process is the further improvement of well-established standard microfabrication processes, i.e., photolithography combined with photoresist thermal reflow. Then, three approaches for integrating the MLs with the photodetecting substrate were tested. The first was using a polydimethylsiloxane (PDMS) intermediate layer for controlling the thickness between the MLs and the photodetecting substrate for allowing different focal lengths to be used depending on the application. The second one is setting the MLs’ focal length within the photodetectors’ depletion region using a 150 μm thin glass substrate for demonstrating that the current generation is enhanced for the same active area. Finally, the third approach consists on a setup composed by a MLs array fabricated directly on top of the PDs and in this approach, two solutions are presented. One is the fabrication of a ML on a square PD with the side measuring 24 μm. This setup enables the capture of light that would otherwise fall outside the photodiodes’ active area resulting in an overall photocurrent generation gain. The other is the fabrication of a MLs array using the same photomask but on a square PD with the side measuring 240 μm for determining the level of photocurrent generation. Moreover, two light sources (red and white lights) were used for evaluating the light acquisition enhancement capacity. From the results that were obtained under different integration solutions, the direct fabrication of MLs on PDs was the one with the better results concerning photocurrent generation by improving it by more than 14% and 2% for red and white lights, respectively. The red light has the ideal penetration depth in silicon for achieving the most prominent enhancement in photocurrent generation presented in this thesis. The MLs that were designed and fabricated, as well as their integration solutions with a photosensitive substrate, show interesting potential in applying them on industry standard fabrication processes for optical microsystems, from light-acquisition enhancement applications to image sensors.Desde há milhares de anos que a Humanidade tem usado lentes por inúmeras razões e para diferentes aplicações. Mais recentemente, têm sido desenvolvidas e fabricadas lentes de microdimensões, também designadas de microlentes (MLs), utilizando a tecnologia dos semicondutores. Este novo tipo de lentes é normalmente utilizado para colimar, focar ou criar imagens, e é uma alternativa apelativa para aplicações onde a miniaturização e simplicidade de alinhamento são requisitos importantes. Além disso, elas também deram origem a um conjunto de novas aplicações para estruturas óticas reduzindo, ao mesmo tempo, as complexidades mecânicas e elétricas dos sistemas existentes. Nesta perspetiva, a presente tese tem como principais objetivos o desenho e desenvolvimento de um processo que permita o fabrico de MLs plano-convexas de diferentes tamanhos com intervenção mínima nos parâmetros do processo. As MLs foram fabricadas utilizando um polímero fotosensível (PF), o AZ4562, através de fotolitografia e refluxo térmico. Outro objetivo foi o fabrico de MLs diretamente na superfície de um die de silício, que contém fotodíodos (FDs) em tecnologia complementary metal–oxide semiconductor (CMOS), para quantificar as diferenças na sua capacidade de gerar fotocorrente (FC). O processo de fabrico ótimo de MLs foi alcançado quando uma fotomáscara (FM) de crómio de super alta-resolução de 128k dots per inch (dpi) foi usada. Esta FM permite que o desenho-padrão seja transferido para o PF com elevada precisão. No entanto, para se obter o perfil de lente, é necessário aplicar um tratamento térmico à microestrutura fabricada. Quando o PF é submetido a uma temperatura mais alta do que a sua temperatura de transição vítrea, este amolece permitindo assim que a sua forma se altere. No caso das MLs, a principal força responsável para que essa mudança ocorra durante este processo térmico é a tensão superficial. As MLs fabricadas, foram estruturalmente caracterizadas usando um perfilómetro e imagens de scanning electron microscope (SEM). Para medir a distância focal (f), foi concebido um sistema de alinhamento opto-mecânico e verificou-se que existe uma pequena diferença de 4% entre o valor medido e o calculado. Foi conseguida ainda uma melhoria adicional com a introdução de uma fase de reidratação no processo de fabrico. A fase de prebake utilizada no fabrico serve para evaporar os solventes do PF mas, todavia, retira também todo o seu conteúdo de água. Por isso, foi demonstrado que o AZ4562 necessita de ser reidratado para se conseguir excelentes resultados prevenindo danos estruturais nas MLs que é fundamental para a obtenção de propriedades óticas eficientes. A maior vantagem neste novo processo otimizado é a melhoria conseguida nos processos de microfabricação standard estabelecidos, i.e., fotolitografia combinada com o refluxo térmico do PF. Em seguida, foram testadas três formas para integrar as MLs num substrato fotossensível. A primeira consistiu em utilizar uma camada intermédia de polidimetilssiloxano (PDMS) para controlar a espessura entre as MLs e o substrato fotodetetor e assim, permitir a utilização de diferentes f dependendo da aplicação. A segunda foi colocar f dentro da região de depleção do FD usando um substrato de vidro com 150 μm de espessura demonstrando que a geração de FC é aumentada para a área ativa. Por último, a terceira abordagem foi o desenvolvimento de um setup composto por um array de MLs fabricado diretamente sobre os FDs e duas soluções são apresentadas. Uma delas é o fabrico de uma ML num FD quadrado com 24 μm de lado. Este setup permite a captura de luz que não iria incidir na área ativa do FD resultando num aumento de geração de FC. O outro é o fabrico de um array de MLs usando a mesma FM, mas num FD quadrado com 240 μm de lado, para determinar o nível de geração de FC. Nestes testes, recorreu-se a duas fontes de luz (vermelha e branca) para avaliar a capacidade de aumentar a aquisição de luz. Relativamente à geração de FC, o melhor dos resultados obtidos nas várias soluções de integração propostas, foi conseguido com o fabrico direto de MLs nos FDs com aumentos superiores a 14% e 2% para as luzes vermelha e branca, respetivamente. A luz vermelha tem a penetração ideal no silício para atingir os resultados mais proeminentes no que concerne aos ganhos obtidos na geração de FC apresentado nesta tese. As MLs que foram desenhadas e fabricadas, bem como as soluções propostas de integração num substrato fotossensível, demonstram um potencial interesse de aplicação em processos industriais de fabrico standard para microsistemas óticos, desde aplicações de aumento de aquisição de luz, até sensores de imagens