Miniaturized Laser Heterodyne Radiometer
This instrument uses a variation of laser heterodyne radiometer (LHR) to measure the concentration of trace gases in the atmosphere by measuring their absorption of sunlight in the infrared. Each absorption signal is mixed with laser light (the local oscillator) at a near-by frequency in a fast photoreceiver. The resulting beat signal is sensitive to changes in absorption, and located at an easier-to-process RF frequency. By separating the signal into a RF filter bank, trace gas concentrations can be found as a function of altitude.
Remote Sensing Based on Fluorescence LIDAR
As originally developed, BILI is a novel planetary Astrobiology instrument based on a real-time technique of remote detection and discrimination of bio-signatures dispersed in the ground-level planetary atmosphere, leveraging the fluorescence lidar technology. Capabilities of this first planetary atmospheric bio-indicator survey instrument will dramatically increase the probability of finding the signatures of extraterrestrial life by performing atmospheric volume scans of hundreds of meters in a radial direction around the rover or lander. The Bio-Indicator Lidar technology employs real-time aerosol particle detection and discrimination based on two physical variables: particle fluorescence and particle size in the bio-discrimination space.
Gas Composition Sensing Using Carbon Nanotube Arrays
An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multiwall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the current collecting plate, such as a gold plated silicon wafer or a stainless steel plate for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensors can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.
Detection Of Presence Of Chemical Precursors
These needs are met by this invention, which provide easy stem and associated method for detecting one or more chemical precursors (components) of a multi-component explosive compound. Different carbon nanotubes (CNTs) are loaded (by doping, impregnation, coating, or other functionalization process) for detecting of different chemical substances that are the chemical precursors, respectively, if these precursors are present in a gas to which the CNTs are exposed. After exposure to the gas, a measured electrical parameter (e.g. voltage or current that correlate to impedance, conductivity, capacitance, inductance, etc.) changes with time and concentration in a predictable manner if a selected chemical precursor is present, and will approach an asymptotic value promptly after exposure to the precursor. The measured voltage or current are compared with one or more sequence soft heir reference values for one or more known target precursor molecules, and a most probable concentration value is estimated for each one, two, or more target molecules. An error value is computed, based on differences of voltage or current for the measured and reference values, using the most probable concentration values. Where the error value is less than a threshold, the system concludes that the target molecule is likely. Presence of one, two, or more target molecules in the gas can be sensed from a single set of measurements.
Biomarker Sensor Arrays for Microfluidics Applications
This invention provides a method and system for fabricating a biomarker sensor array by dispensing one or more entities using a precisely positioned, electrically biased nanoprobe immersed in a buffered fluid over a transparent substrate. Fine patterning of the substrate can be achieved by positioning and selectively biasing the probe in a particular region, changing the pH in a sharp, localized volume of fluid less than 100 nm in diameter, resulting in a selective processing of that region. One example of the implementation of this technique is related to Dip-Pen Nanolithography (DPN), where an Atomic Force Microscope probe can be used as a pen to write protein and DNA Aptamer inks on a transparent substrate functionalized with silane-based self-assembled monolayers. But it would be recognized that the invention has a much broader range of applicability. For example, the invention can be applied to formation of patterns using biological materials, chemical materials, metals, polymers, semiconductors, small molecules, organic and inorganic thins films, or any combination of these.
Electrical Response Using Nanotubes on a Fibrous Substrate
A resistor-type sensor was fabricated which has a network of cross-linked SWCNTs with purity over 99%. An ordinary cellulose paper used for filtration was employed as the substrate. The filter paper exhibits medium porosity with a flow rate of 60 mL/min and particle retention of 5-10m. The roughness and porosity of the papers are attractive because they increase the contact area with the ambient air and promote the adhesion to carbon nanotubes. The SWCNTs were functionalized with carboxylic acid (COOH) to render them hydrophilic, thus increasing the adhesion with the substrate. The functionalized SWCNTs were dispersed in dimethylformamide solution. The film composed of networks of cross-linked CNTs was formed using drop-cast coating followed by evaporation of the solvent. Adhesive copper foil tape was used for contact electrodes. Our sensors outperformed the oxide nanowire-based humidity sensors in terms of sensitivity and response/recovery times.
Gas Sensors Based on Coated and Doped Carbon Nanotubes
A typical sensor device includes a set of interdigitated microelectrodes fabricated by photolithography on silicon wafer or an electrically insulating substrate. In preparation for fabricating the SWCNT portion of such a sensor, a batch of treated (coated or doped) SWCNTs is dispersed in a solvent. The resulting suspension of SWCNTs is drop-deposited or injected onto the area containing the interdigitated electrodes. As the solvent evaporates, the SWCNTs form a mesh that connects the electrodes. The density of the SWCNTs in the mesh can be changed by varying the concentration of SWCNTs in the suspension and/or the amount of suspension dropped on the electrode area. To enable acquisition of measurements for comparison and to gain orthogonality in the sensor array, undoped SWCNTs can be similarly formed on another, identical set of interdigitated electrodes. Coating materials tested so far include chlorosulfonated polyethylene. Dopants that have been tested include Pd, Pt, Au, Cu and Rh nanoparticle clusters. To date, the sensor has been tested for NO2, NH3, CH4, Cl2, HCl, toluene, benzene, acetone, formaldehyde and nitrotoulene.
Compact Sensor for In-Situ Gas Species Determination and Measurement
NASA's gas sensor was originally developed for the storage of volatile liquids and high-pressure gases in outer space in order to facilitate space travel. The innovation has a diverse array of applications beyond aerospace, including cryogenic environments, pressurized or vacuum conditions, and hazardous locations. The sensor system is composed of 1) a fiber-coupled laser light source, 2) a fiber-coupled photodiode detector, and 3) an optical interferometer. The non-intrusive sensor employs a number of optical techniques to measure gas density, temperature, type of species present, and concentration of various species. When the sensor is placed in the area where a gas leak may be present, gas density is detected and recorded as a result of changes in light transmission through the fiber. Changes in the density of gas in the test region cause corresponding changes in the intensity output onto a photodiode detector. This process provides a real-time, temporal history of a leak. Gas temperature is determined by placing an optical fiber along the length of a structure for in-situ measurements. The type of gas species present can be determined by using optical line emission spectrometry. The light-based sensor uses these interferometric and spectroscopic techniques to obtain real-time, in-situ measurements that have been successfully tested in environments with a pressure range of 20 mtorr to 760 mtorr. Commercially available gas detection methods are limited in several ways. Vacuum gauges can detect only certain gases, and they have a limited operational range. Mass spectrometer systems are able to perform well, but their size, bulk, and use of high voltage, which can potentially cause arcing and ignition of combustible propellants, severely limit their usefulness. NASA's compact gas detection sensor has numerous advantages over other state-of-the-art detection techniques. Because the sensor is rugged, compact, and lightweight, it can be used in small, remote areas where other devices will not fit. It has no electronic ignition device, making the system suitable for use in explosive or hazardous environments. The system measures gas density, temperature, type, and concentration in real time, providing critical information on both the severity and location of the leak, all while consuming minimal power at very low cost.
Real Time Radiation Monitoring Using Nanotechnology
Carbon nanotube chemical sensors are suitable for sensing different analytes. Such sensors can be configured in the form of an array to comprehensively and cost-effectively monitor multiple analytes. A 32-sensor array on a silicon chip was tested under the proton exposure at two energy levels, with three different fluences. The result of the proton irradiation experiment indicates that this SWCNT device is sensitive to the proton exposure at different levels and it recovers upon turning off the incident radiation. Carbon nanotube-based sensors are particularly suitable and promising for chemical and radiation detection, because the technology can be used to fabricate gas or liquid chemical sensors that have extremely low power requirements and are versatile and ultra-miniature in size, with added cost benefits. Low-power carbon nanotube sensors facilitate distributed or wireless gas sensing, leading to efficient multi-point measurements, and to greater convenience and flexibility in performing measurements in space as well as on Earth.
materials and coatings
Sequential/Simultaneous Multi-Metalized Nanocomposites (S2M2N)
Well-dispersed metal decorated nanotube or nanowire polymer composites have rarely been reported because of the excessive weight contrast between the decorated tubes and the polymer matrix. However, various properties, such as high electrical conductivity, permittivity, permeability, wear resistance, anti-penetrant, radiation shielding and high toughness are desirable and can be achieved with SeM2N metalized nanocomposites. Further, it is desirable to have nanocomposites that exhibit improvement in more than one of these properties and thus be capable of performing multiple functions. This invention provides a method to decorate pre-resided nanotube (CNT, BNNT, GPs) or nanowire surfaces in a polymer matrix with metal nanoparticles via supercritical fluid (SCF) deposition.