Research on A Novel Reliable MEMS Bistable Solid State Switch

As a result of the unpredictable nature of extreme environments (including temperature, humidity, impact, and other factors), micro-electro-mechanical systems (MEMS) solid-state fuze control modules have an urgent requirement for a MEMS solid-state switch (MEMS-S3). In particular, this switch must remain stable without any energy input after a state transition (i.e., it must be bistable). In this paper, a MEMS bistable solid-state switch (MEMS-bS3) is designed that is based on the concept of producing a micro-explosion. The reliable state switching of the MEMS-bS3 is studied via heat conduction theory and verified via both simulations and experimental methods. The experimental results show that these switches can produce micro-explosions driven by 33 V/47 μF pulse energy. However, the metal film bridge (MFB) structures used in this switch with smaller dimensions (80×20 μm2, 90×30 μm2, and 100×40 μm2) could not enable the switch to realize a reliable state transition, and the state transition rate was less than 40%. When the MFB dimensions reached 120×60 μm2 or 130×70 μm2, the state transition rate exceeded 80%, and the response time was on the μs-scale

낮은 임계 가속도를 가지는 실리콘 기반 MEMS 가속도 스위치에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 김용권.Abstract In this paper, MEMS acceleration switch with low threshold acceleration below 10 g and fine environmental characteristics are developed. Limits of the previously reported low-g MEMS switches were addressed in terms of environmental test issues and the solutions for them were suggested and integrated in the proposed low-g MEMS acceleration switch. Fabrication process consists of one silicon-on-insulator substrate and two glass substrates for base and package, respectively. Single-crystalline silicon was chosen as the structural material for high thermal stability and stress-free structure. After the fabrication, height profiles of the free-hanging proof masses were measured to show that the fabricated switches does not suffer from stress problems. The size of single switch was measured as 2150 x 4240 x 1180 µm3 and the average proof mass, initial gap, and the spring constant was 307.38 µg, 6.39 µm, and 3.29 N/m, respectively. The calculated threshold acceleration thus was 6.98 g. In the electrostatic operation test, the response time of the switch was measured to be shorter than 1.2 ms and the minimum contact resistance was 8.5 Ω at the contact force of 284 µN. Life cycle test was carried out to show that the developed switch could operate more than 10,000 cycles without failure. Rotation-table experiment was carried out in sequence to reveal that the switch operates at 6.61 g. The error analysis was carried out in the consideration of the off-axis force generated during the rotation-table experiment. From the experimental values, the off-axis force was calculated as 2.091 μN and the resulting reduction in the initial switching gap was simulated as 0.236 μm. The reduced threshold acceleration thus was estimated to be 6.512 g, which agrees well with the measured threshold acceleration value of 6.61 g. Rotation-table test using another switch was conducted to model the relation between the off-axis force and the operating acceleration of the developed switch. Least squares method was used in the analysis and the original threshold acceleration (a_th) of the switch was calculated as 6.16325 g. The error rate (ε) due to the off-axis force was calculated as -0.22693 g/µN. The modeled operating acceleration of the switch in terms of the off-axis force matched well with the measurements, showing the maximum error less than 1.6%. Heating, sealing, high-g, and impact tests were conducted in sequence to validate the environmental characteristics of the switch. Test condition of 80 °C for 6 hours were adopted for heating test and the tested switch operated more than 200 cycles normally after the test. For sealing test, gross leak test using penetrant dye (Rhodamine B) and fine leak test using tracer gas (helium) were conducted sequentially. 10 samples were put into both of the tests. In the gross leak test, no signs of dye penetration were observed after pressurizing the samples in the dye solution. The tested switches were then put into the fine leak test. In the fine leak test, helium leak rates were measured and all of the tested samples showed leak rate lower than 5.8x10-8 atm cc/s He, which is the reject limit provided by MIL-STD-883E. High-g test and drop impact test were also performed to validate the effectiveness of the displacement-restricting structure. As a result of the high-g test, the developed switch was able to operate without breaking after experiencing the acceleration of 300 g in the ±x ̂, ±y ̂, and ±z ̂ axes. In addition, the drop impact test has proved that the developed switch can withstand an impact as high as 1000 g. The MEMS acceleration switch developed throughout this study is the first to attain low threshold and good environmental characteristics at the same time. Therefore, the author believes that the switch developed in this study is the most suitable one for safety arm unit application among the low-g switches developed so far.1. Introduction 1 1.1. Sensing of acceleration 1 1.2. Safety arm unit and MEMS acceleration switches 8 1.3. Literature review 14 1.4. Motivation and purpose 19 1.5. Contribution 20 1.6. Composition of thesis 22 2. Theory and design of low-g MEMS acceleration switch 23 2.1. Basic theories on acceleration switch 23 2.1.1 Static threshold acceleration 23 2.1.2 Determining the initial gap 25 2.1.3 Serpentine spring 27 2.1.4 Parallel plate damper 31 2.2. Model description 34 2.2.1 Base glass substrate 36 2.2.2 SOI substrate 36 2.2.3 Packaging glass substrate 37 2.3. FEM simulation 38 2.3.1 Force, displacement, stress simulation 38 2.3.2 Modal analysis Resonant frequency 40 2.4. MATLAB code for MEMS switch 45 3. Fabrication of low-g MEMS acceleration switch 63 3.1. Overall fabrication process 63 3.2. Base glass substrate 65 3.3. SOI substrate 69 3.4. Bonded susbtrate & packaging 72 3.5. Fabrication results 79 4. Characterization of low-g MEMS acceleration switch 84 4.1. DC operation test & lifecycle test 84 4.2. Rotation-table experiments 93 4.3. Effect of the off-axis force on the operating acceleration 101 4.4. Heating test 111 4.5. Sealing test 112 4.6. High-g test & drop impact test 118 5. Conclusion 125 References 128 Abstract (Korean) 136Docto

Earth Observatory Satellite system definition study. Report 5: System design and specifications. Volume 3: General purpose spacecraft segment and module specifications

The specifications for the Earth Observatory Satellite (EOS) general purpose aircraft segment are presented. The satellite is designed to provide attitude stabilization, electrical power, and a communications data handling subsystem which can support various mission peculiar subsystems. The various specifications considered include the following: (1) structures subsystem, (2) thermal control subsystem, (3) communications and data handling subsystem module, (4) attitude control subsystem module, (5) power subsystem module, and (6) electrical integration subsystem

Earth Observatory Satellite system definition study. Report no. 6: Space shuttle interfaces/utilization

The impacts of achieving compatibility of the Earth Observatory Satellite (EOS) with the space shuttle and the potential benefits of space shuttle utilization are discussed. Mission requirements and mission suitability, including the effects of multiple spacecraft missions, are addressed for the full spectrum of the missions. Design impact is assessed primarily against Mission B, but unique requirements reflected by Mission A, B, and C are addressed. The preliminary results indicated that the resupply mission had the most pronounced impact on spacecraft design and cost. Program costs are developed for the design changes necessary to achieve EOS-B compatibility with Space Shuttle operations. Non-recurring and recurring unit costs are determined, including development, test, ground support and logistics, and integration efforts. Mission suitability is addressed in terms of performance, volume, and center of gravity compatibility with both space shuttle and conventional launch vehicle capabilities

41st Aerospace Mechanisms Symposium

The proceedings of the 41st Aerospace Mechanisms Symposium are reported. JPL hosted the conference, which was held in Pasadena Hilton, Pasadena, California on May 16-18, 2012. Lockheed Martin Space Systems cosponsored the symposium. Technology areas covered include gimbals and positioning mechanisms, components such as hinges and motors, CubeSats, tribology, and Mars Science Laboratory mechanisms

Unmanned Aircraft Systems in the Cyber Domain

Unmanned Aircraft Systems are an integral part of the US national critical infrastructure. The authors have endeavored to bring a breadth and quality of information to the reader that is unparalleled in the unclassified sphere. This textbook will fully immerse and engage the reader / student in the cyber-security considerations of this rapidly emerging technology that we know as unmanned aircraft systems (UAS). The first edition topics covered National Airspace (NAS) policy issues, information security (INFOSEC), UAS vulnerabilities in key systems (Sense and Avoid / SCADA), navigation and collision avoidance systems, stealth design, intelligence, surveillance and reconnaissance (ISR) platforms; weapons systems security; electronic warfare considerations; data-links, jamming, operational vulnerabilities and still-emerging political scenarios that affect US military / commercial decisions. This second edition discusses state-of-the-art technology issues facing US UAS designers. It focuses on counter unmanned aircraft systems (C-UAS) – especially research designed to mitigate and terminate threats by SWARMS. Topics include high-altitude platforms (HAPS) for wireless communications; C-UAS and large scale threats; acoustic countermeasures against SWARMS and building an Identify Friend or Foe (IFF) acoustic library; updates to the legal / regulatory landscape; UAS proliferation along the Chinese New Silk Road Sea / Land routes; and ethics in this new age of autonomous systems and artificial intelligence (AI).https://newprairiepress.org/ebooks/1027/thumbnail.jp

Miniaturized Optical Probes for Near Infrared Spectroscopy

RÉSUMÉ L’étude de la propagation de la lumière dans des milieux hautement diffus tels que les tissus biologiques (imagerie optique diffuse) est très attrayante, car elle offre la possibilité d’explorer de manière non invasive le milieu se trouvant profondément sous la surface, et de retrouver des informations sur l’absorption (liée à la composition chimique) et sur la diffusion (liée à la microstructure). Dans la gamme spectrale 600-1000 nm, également appelée gamme proche infrarouge (NIR en anglais), l'atténuation de la lumière par le tissu biologique (eau, lipides et hémoglobine) est relativement faible, ce qui permet une pénétration de plusieurs centimètres dans le tissu. En spectroscopie proche infrarouge (NIRS en anglais), de photons sont injectés dans les tissus et le signal émis portant des informations sur les constituants tissulaires est mesuré. La mesure de très faibles signaux dans la plage de longueurs d'ondes visibles et proche infrarouge avec une résolution temporelle de l'ordre de la picoseconde s'est révélée une technique efficace pour étudier des tissus biologiques en imagerie cérébrale fonctionnelle, en mammographie optique et en imagerie moléculaire, sans parler de l'imagerie de la durée de vie de fluorescence, la spectroscopie de corrélation de fluorescence, informations quantiques et bien d’autres. NIRS dans le domaine temporel (TD en anglais) utilise une source de lumière pulsée, généralement un laser fournissant des impulsions lumineuses d'une durée de quelques dizaines de picosecondes, ainsi qu'un appareil de détection avec une résolution temporelle inférieure à la nanoseconde. Le point essentiel de ces mesures est la nécessité d’augmenter la sensibilité pour de plus grandes profondeurs d’investigation, en particulier pour l’imagerie cérébrale fonctionnelle, où la peau, le crâne et le liquide céphalo-rachidien (LCR) masquent fortement le signal cérébral. À ce jour, l'adoption plus large de ces techniques optique non invasives de surveillance est surtout entravée par les composants traditionnels volumineux, coûteux, complexes et fragiles qui ont un impact significatif sur le coût et la dimension de l’ensemble du système. Notre objectif est de développer une sonde NIRS compacte et miniaturisée, qui peut être directement mise en contact avec l'échantillon testé pour obtenir une haute efficacité de détection des photons diffusés, sans avoir recours à des fibres et des lentilles encombrantes pour l'injection et la collection de la lumière. Le système proposé est composé de deux parties: i) une unité d’émission de lumière pulsée et ii) un module de détection à photon unique qui peut être activé et désactivé rapidement. L'unité d'émission de lumière utilisera une source laser pulsée à plus de 80 MHz avec une largeur d'impulsion de picoseconde.----------ABSTRACT The study of light propagation into highly diffusive media like biological tissues (Diffuse Optical Imaging) is highly appealing due to the possibility to explore the medium non-invasively, deep beneath the surface and to recover information both on absorption (related to chemical composition) and on scattering (related to microstructure). In the 600–1000 nm spectral range also known as near-infrared (NIR) range, light attenuation by the biological tissue constituents (i.e. water, lipid, and hemoglobin) is relatively low and allows for penetration through several centimeters of tissue. In near-infrared spectroscopy (NIRS), a light signal is injected into the tissues and the emitted signal carrying information on tissue constituents is measured. The measurement of very faint light signals in the visible and near-infrared wavelength range with picosecond timing resolution has proven to be an effective technique to study biological tissues in functional brain imaging, optical mammography and molecular imaging, not to mention fluorescence lifetime imaging, fluorescence correlation spectroscopy, quantum information and many others. Time Domain (TD) NIRS employs a pulsed light source, typically a laser providing light pulses with duration of a few tens of picoseconds, and a detection circuit with temporal resolution in the sub-nanosecond scale. The key point of these measurements is the need to increase the sensitivity to higher penetration depths of investigation, in particular for functional brain imaging, where skin, skull, and cerebrospinal fluid (CSF) heavily mask the brain signal. To date, the widespread adoption of the non-invasive optical monitoring techniques is mainly hampered by the traditional bulky, expensive, complex and fragile components which significantly impact the overall cost and dimension of the system. Our goal is the development of a miniaturized compact NIRS probe, that can be directly put in contact with the sample under test to obtain high diffused photon harvesting efficiency without the need for cumbersome optical fibers and lenses for light injection and collection. The proposed system is composed of two parts namely; i) pulsed light emission unit and ii) gated single-photon detection module. The light emission unit will employ a laser source pulsed at over 80MHz with picosecond pulse width generator embedded into the probe along with the light detection unit which comprises single-photon detectors integrated with other peripheral control circuitry. Short distance source and detector pairing, most preferably on a single chip has the potential to greatly expedites the traditional method of portable brain imaging