mechanical and fluid systems
Wafer Level Microchannel Fabrication Process for Lab-on-a-Chip Devices
The microchannel chip is created from a silicon bottom wafer and Pyrex top wafer anodically bonded. Specialized microbeads with specific structure and surface chemistry are placed along the channels. Different species of analyte molecules will interact more strongly with the column chemistry and will therefore take longer to traverse the column, i.e., have a longer retention time. In this way, the channels separate molecular species based on their chemistry. The specific shape and surface chemistry of these microchannels do more than just move analyte moleculesthe molecules are separated by how they are affected by the channels chemistry for expedited analysis. Paired with mass spectroscopy or ChemFET technology, this technology could enhance research and development in microchemistry, microfluidics, and lab-on-a-chip technology. Another embodiment of this invention includes microposts inside the microfluidic channel for particle separation, rather than using microbeads. The silicon microposts can be built inside of silicon microfluidic channel by MEMS technology. The size of microposts can vary depending on the application. The microposts function as an in-line filter to block unwanted big particles and protect the microfluidic chip. Furthermore, micropost chips with microvalves can physically select different size cells, molecules, viruses etc. It can also be used to select different particles in bioengineering and pharmaceutical testing.
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.
Interference Reduction Algorithm for Continuous Wave Lidar Return Data
The NASA algorithm was developed to support the ASCENDS mission Laser Absorption Spectrometer (LAS) for carbon dioxide measurements in the mid-to-lower troposphere. The LAS is a satellite-based continuous wave lidar system capable of monitoring global variability of carbon dioxide concentration in the troposphere from space, with a measurement range of up to ~500 km (low earth orbit). The modulation algorithm (a filtered pseudo-noise code algorithm) is capable of eliminating cross-channel noise and interference by modulating the lidar return signal using a time shifting approach. Figures 1 and 2 below demonstrate these capabilities. The technology builds on a strong remote sensing and lidar technology heritage at NASAs Langley Research Center. The algorithms are complete, have been verified as error-free by independent third parties, and flight tests aboard a Dassault HU-25C Guardian Falcon jet are scheduled for Fall of 2014. Lidar system specifications for the test bed include: -- Three 17.7 cm telescopes -- CW lidar system powered by three 10W erbium-doped fiber amplifiers to provide 30W average laser power -- A low noise, high gain HgCdTe detector and cryocooler The algorithms are mission ready and are available for licensure and implementation in a wide range of continuous wave lidar applications.
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.
Nanostructure Sensing and Transmission of Gas Data
At the center of the data acquisition system is a microcontroller that samples each sensor element through a set of four multiplexers. Each MUX reads signals from a group of eight chemical sensing elements. The LM234A constant current source is used to provide a constant current (100 uA) to each sensing element. The current level is dependent upon the base resistances of different nanostructure sensing materials. Four of these devices (or one device if the sensing materials have similar base resistances) are used to excite each group of eight chemical sensing elements. Conductivity or resistance is measured by supplying a constant current and measuring the corresponding voltage difference across the sensor. Also included in the data system is temperature measurement by using an AD22100K temperature sensor. The microcontroller reads all 32 chemical sensor and temperature values and generates a serial data output that can be connected directly to a wireless serial device server for wireless data transmission, or to an RS-232 serial data output to a PC for data logging. Each of the individual sensors has its own data reporting cycle, and it is assumed that these reporting cycles are numerically compatible. In the first approach, each of the reporting cycles has the same length delta t, and the four sensors report to the multiplexer in a consecutive interleave pattern. This innovation is self-contained and portable, and wirelessly transmits measurement data to a PC, using an IEEE802.11a, 802.11b, or 802.15 wireless LAN protocol. The footprint of the invention has a diameter as small as a few centimeters.