A microfabricated sensor for thin dielectric layers

We describe a sensor for the measurement of thin dielectric layers capable of operation in a variety of environments. The sensor is obtained by microfabricating a capacitor with interleaved aluminum fingers, exposed to the dielectric to be measured. In particular, the device can measure thin layers of solid frozen from a liquid or gaseous medium. Sensitivity to single atomic layers is achievable in many configurations and, by utilizing fast, high sensitivity capacitance read out in a feedback system onto environmental parameters, coatings of few layers can be dynamically maintained. We discuss the design, read out and calibration of several versions of the device optimized in different ways. We specifically dwell on the case in which atomically thin solid xenon layers are grown and stabilized, in cryogenic conditions, from a liquid xenon bath

High Efficiency Crumpled CNT Thin Film Heater For Hydrogen Sensing

다중 벽 탄소나노튜브 (MWCNTs), 박막 히터 (Thin Film Heater), 줄 발열 (Joule Heating), 기판 수축 (Substrate Shrinkage), 수소 가스 센싱 (Hydrogen Gas Sensing)This paper presents the fabrication of crumpled carbon nanotube (C-CNT) thin film heaters and its application towards high sensitivity and low drift hydrogen gas sensing. By utilizing a simple spray coating of pristine multi-walled carbon nanotubes (MWCNTs) and thermal substrate shrinkage method, we have fabricated a C-CNT film with closely packed junctions. Joule heating of C-CNTs results higher temperature at a given input voltage compared to as-deposited CNTs. Specifically, the temperature of C-CNT heaters increase as high as 200 % than as-deposited CNT heaters due to higher junction densities in a given area. In addition, the temperature coefficient of resistance (TCR) of both C-CNT and as-deposited CNT heaters are analyzed for an accurate temperature control and measurement of the CNT heaters. All of the fabricated heaters exhibit linear TCR, and thus allowing a stable thermal operation. The higher heating efficiency of the C-CNT heaters can contribute to gas sensing with improved adsorption and desorption characteristics. Our results show that the C-CNT heaters are capable of hydrogen gas sensing while demonstrating higher measurement sensitivities along with lower drift compared to as-deposited CNT devices. Additionally, the self-heating mechanism of proposed heaters help rapid desorption of hydrogen, and thus allowing repetitive and stable sensor operation. Our findings reveal that both CNT morphologies and heating temperature affect the hydrogen sensing performances. The proposed C-CNT devices are suited for low power or voltage sensing platforms. For future work, sub-mm scaled shadow masks would allow C-CNT devices to be scaled down to µm-scale from macro-scaled devices. Hence, we envision the batch fabrication of C-CNT device arrays. In addition, C-CNT structures will be onto thermally resistant substrates, such as Silicon wafer, Glass or PET, so that we can compare C-CNT devices with as-deposited CNT on same substrate. Utilizing SEM micrographs and Raman analysis, the proposed transfer printing process will be optimized as well.open1. INTRODUCTION 1 1.1. CNT Based Sensors & Electronic Device 2 1.2. Specific Aims of Theses 3 2. Background/Review of Relevant Previous Work 5 2.1. Operating Principles & Outstanding Advantages of CNT Heaters 5 2.2. Improving the Performance of CNT Thin Film Heaters 6 2.2.1.Chemical Treatment and Nanoparticle Deposition 6 2.2.2.Doctor-blade Method Deposition and Increase in Power Efficiency 7 2.3. Densified Structure by Substrate Shrinkage Method 8 2.4. CNT based Gas Sensors 11 3. Materials and Methods 14 3.1. Fabrication of Crumpled CNT Device 14 3.2. Device Characterization and Hydrogen Sensing Setup 16 4. Results 19 4.1. Device Characterization 19 4.2.Hydrogen Gas Sensing 22 5. Discussion 28 6. Future work 31 7. Conclusion 32 8. References 34 Appendix 40이 논문은 구겨진 탄소 나노 튜브 (C-CNT) 박막 히터 (Thin Film Heater)의 제조 및 고감도의 낮은 드리프트 (Drift) 수소 가스 센싱에 대한 응용을 제시한다. 다중 벽 탄소 나노 튜브 (MWCNT)의 용액을 간단한 스프레이 코팅 및 열 기판 수축 (Substrate Shrinkage) 방법을 이용하여, 밀접하게 접합 된 C-CNT 히터를 제조했습니다. C-CNT의 줄 발열(Joule heating)은 기판 수축하지 않은 CNT 히터 (As-coated CNT)에 비해 같은 전압에서 더 높은 온도를 발생 시킵니다. 구체적으로는, C-CNT 히터의 온도는 주어진 영역에서 더 높은 접합 밀도로 인해 As-coated CNT 히터보다 200%만큼 증가합니다. 또한, C-CNT 및 As-coated CNT 히터의 온도 저항 계수 (Temperature Coefficient of Resistance, TCR)는 CNT 히터의 정확한 온도 제어 및 측정을 위해 분석됩니다. 다음과 같이 제작 된 모든 히터들은 높은 선형성의 TCR을 보입니다. C-CNT 히터의 고효율 가열 성능은 높은 흡착 및 탈착 특성을 가지고 있고, 이를 이용하여 수소 가스 센싱 (Hydrogen Gas Sensing)에 기여할 수 있습니다. C-CNT 히터는 수소 가스 감지가 가능하지만 As-coated CNT 히터에 비해 전기적 저항의 Drift 현상이 적고 측정 감도가 더 높습니다. 또한 제안 된 히터의 자체 가열 메커니즘은 수소의 빠른 탈착을 도와 반복적이고 안정적인 센서 작동을 가능하게 합니다. 이러한 연구 결과에서C-CNT 형태와 가열 온도가 모두 수소 감지 성능에 영향을 미치는 것으로 밝혀졌습니다. 제안 된 C-CNT 장치는 저전력 또는 저전압 감지 플랫폼에서 활용 될 수 있습니다. 향후 작업에서는 1 mm이하 사이즈의 쉐도우 마스크를 사용하게 되면, C-CNT 디바이스를 µm 스케일로 축소 할 수 있습니다. 따라서, 2 내지 6인치 범위의 다양한 웨이퍼 크기에서 정렬된 C-CNT 디바이스를 일괄적으로 공정이 가능할 수 있을 것으로 예상합니다. C-CNT구조층을 실리콘 웨이퍼, 유리, 또는 PET와 같은 내열성 기판으로 전사 작업을 하게 되면 200 ℃ 이상의 고온에 따른 수소 가스 검출을 확인 할 수 있습니다. 또한, C-CNT 구조 층을 PET에 전사 작업을 하게 되면 동일한 기판 상에 증착된 CNT와 직접적으로 비교할 수 있을 것으로 기대합니다. 전자작업중에 발생 할 화학적 또는 물리적인 영향을 검사하기 위해 주사전자현미경 사진과 라만 분광 분석을 활용하여 분석을 수행 할 수 있습니다. 마지막으로, 적절한 화학적 또는 물리적인 금속 기능화 (Metal Functionalization)와 개선된 디바이스 디자인을 통해 수소 가스 검출 이외의 다른 화학 감지 적용 분야에 C-CNT 센서를 적용 할 수 있을 것으로 기대합니다.MasterdCollectio

The NASA SBIR product catalog

The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

New insight in biomedical measurements

L'abstract è presente nell'allegato / the abstract is in the attachmen

A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer

In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm−1), a low detection limit (0.2 ppm) and a rapid response time (35 s)

Design and realization of a sputter deposition system for the \textit{in situ-} and \textit{in operando-}use in polarized neutron reflectometry experiments

We report on the realization of a sputter deposition system for the in situ- and in operando-use in polarized neutron reflectometry experiments. Starting with the scientific requirements, which define the general design considerations, the external limitations and boundaries imposed by the available space at a neutron beamline and by the neutron and vacuum compatibility of the used materials, are assessed. The relevant aspects are then accounted for in the realization of our highly mobile deposition system, which was designed with a focus on a quick and simple installation and removability at the beamline. Apart from the general design, the in-vacuum components, the auxiliary equipment and the remote control via a computer, as well as relevant safety aspects are presented in detail.Comment: Submitted for publication in Nuclear Inst. and Methods in Physics Research, A. (1st revised version

Long Duration Hot Hydrogen Exposure of Nuclear Thermal Rocket Materials

An arc-heater driven hyper-thermal convective environments simulator was recently developed and commissioned for long duration hot hydrogen exposure of nuclear thermal rocket materials. This newly established non-nuclear testing capability uses a high-power, multi-gas, wall-stabilized constricted arc-heater to .produce high-temperature pressurized hydrogen flows representative of nuclear reactor core environments, excepting radiation effects, and is intended to serve as a low cost test facility for the purpose of investigating and characterizing candidate fuel/structural materials and improving associated processing/fabrication techniques. Design and engineering development efforts are fully summarized, and facility operating characteristics are reported as determined from a series of baseline performance mapping runs and long duration capability demonstration tests

Alkaline static feed electrolyzer based oxygen generation system

In preparation for the future deployment of the Space Station, an R and D program was established to demonstrate integrated operation of an alkaline Water Electrolysis System and a fuel cell as an energy storage device. The program's scope was revised when the Space Station Control Board changed the energy storage baseline for the Space Station. The new scope was aimed at the development of an alkaline Static Feed Electrolyzer for use in an Environmental Control/Life Support System as an oxygen generation system. As a result, the program was divided into two phases. The phase 1 effort was directed at the development of the Static Feed Electrolyzer for application in a Regenerative Fuel Cell System. During this phase, the program emphasized incorporation of the Regenerative Fuel Cell System design requirements into the Static Feed Electrolyzer electrochemical module design and the mechanical components design. The mechanical components included a Pressure Control Assembly, a Water Supply Assembly and a Thermal Control Assembly. These designs were completed through manufacturing drawing during Phase 1. The Phase 2 effort was directed at advancing the Alkaline Static Feed Electrolyzer database for an oxygen generation system. This development was aimed at extending the Static Feed Electrolyzer database in areas which may be encountered from initial fabrication through transportation, storage, launch and eventual Space Station startup. During this Phase, the Program emphasized three major areas: materials evaluation, electrochemical module scaling and performance repeatability and Static Feed Electrolyzer operational definition and characterization

Modular integration and on-chip sensing approaches for tunable fluid control polymer microdevices

228 p.Doktore tesi honetan mikroemariak kontrolatzeko elementuak diseinatu eta garatuko dira, mikrobalbula eta mikrosentsore bat zehazki. Ondoren, gailu horiek batera integratuko dira likido emari kontrolatzaile bat sortzeko asmotan. Helburu nagusia gailuen fabrikazio arkitektura modular bat frogatzea da, non Lab-on-a-Chip prototipoak garatzeko beharrezko fase guztiak harmonizatuz, Cyclic-Olefin-Polymer termoplastikozko mikrogailu merkeak pausu gutxi batzuetan garatuko diren, hauen kalitate industriala bermatuz. Ildo horretan, mikrogailuak prototipotik produkturako trantsizio azkar, erraz, errentagarri eta arriskurik gabeen bidez lortu daitezkeenetz frogatuko da

A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme

This study develops a MEMS-based low-cost sensing platform for sensing gas flow rate and flow direction comprising four silicon nitride cantilever beams arranged in a cross-form configuration, a circular hot-wire flow meter suspended on a silicon nitride membrane, and an integrated resistive temperature detector (RTD). In the proposed device, the flow rate is inversely derived from the change in the resistance signal of the flow meter when exposed to the sensed air stream. To compensate for the effects of the ambient temperature on the accuracy of the flow rate measurements, the output signal from the flow meter is compensated using the resistance signal generated by the RTD. As air travels over the surface of the cross-form cantilever structure, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The deflection of the cantilever beams causes a corresponding change in the resistive signals of the piezoresistors patterned on their upper surfaces. The amount by which each beam deflects depends on both the flow rate and the orientation of the beam relative to the direction of the gas flow. Thus, following an appropriate compensation by the temperature-corrected flow rate, the gas flow direction can be determined through a suitable manipulation of the output signals of the four piezoresistors. The experimental results have confirmed that the resulting variation in the output signals of the integrated sensors can be used to determine not only the ambient temperature and the velocity of the air flow, but also its direction relative to the sensor with an accuracy of ± 7.5° error