Director's discretionary fund report for fiscal year 1994

This technical memorandum contains brief technical papers describing research and technology development programs sponsored by the Ames Research Center Director's Discretionary Fund during fiscal year 1991 (October 1993 through September 1994). An appendix provides administrative information for each of the sponsored research programs

Temperature-Dependent Modeling of Thermoelectric Elements

Active thermal control is crucial in achieving the required accuracy and throughput in many industrial applications, e.g., in the medical industry, high-power lighting industry, and semiconductor industry. Thermoelectric Modules (TEMs) can be used to both heat and cool, alleviating some of the challenges associated with traditional electric heater based control. However, the dynamic behavior of these modules is non-affine in their inputs and state, complicating their implementation. To facilitate advanced control approaches a high fidelity model is required. In this work an approach is presented that increases the modeling accuracy by incorporating temperature dependent parameters. Using an experimental identification procedure, the parameters are estimated under different operating conditions. The resulting model achieves superior accuracy for a wide range of temperatures, demonstrated using experimental validation measurements.Comment: 6 pages, 21st IFAC World Congress 202

Computational Analysis and Design Optimization of Convective PCR Devices

Polymerase Chain Reaction (PCR) is a relatively novel technique to amplify a few copies of DNA to a detectable level. PCR has already become common in biomedical research, criminal forensics, molecular archaeology, and so on. Many have attempted to develop PCR devices in numerous types for the purpose of the lab-on-chip (LOC) or point-of-care (POC). To use PCR devices for POC lab testing, the price must be lower, and the performance should be comparable to the lab devices. For current practices with the existing methods, the price is pushed up higher partially due to too much dependence on numerous developmental experiments. Our proposition herein is that the computational methods can make it possible to design the device at lower cost and less time, and even improved performance. In the present dissertation, a convective PCR, that is the required flow circulation is driven by the buoyancy forces, is researched towards the use in POC testing. Computational Fluid Dynamics (CFD) is employed to solve the nonlinear equations for the conjugate momentum and heat transfer model and the species transport model. The first application of the models considers four reactors in contact with two separate heaters, but with different heights. Computational analyses are carried out to study the nature of buoyancy-driven flow for DNA amplification and the effect of the capillary heights on the performance. The reactor performance is quantified by the doubling time of DNA and the results are experimentally verified. The second application includes a novel design wherein a reactor is heated up by a single heater. A process is established for low-developmental cost and high-performance design. The best is searched for and found by evaluating the performance for all possible candidates. The third application focuses on the analysis of the performance of single-heater reactors affected by positions of a capillary tube: (1) horizontal, and (2) vertical. In the last application, numerous double-heater reactor designs are considered to find the one that assure the optimal performance. Artificial Neural Network (ANN) is employed to approximate the CFD results for optimization. In summary, through the four segments of our studies, the results show significant possibilities of increasing the performance and reducing the developmental cost and time. It is also demonstrated that the proposed methodology is advantageous for the development of cPCR reactors for the purpose of POC applications

Acousto-Pi: An Opto-Acoustofluidic System using Surface Acoustic Waves controlled with Open Source Electronics for Integrated In-Field Diagnostics

Surface acoustic wave (SAW) devices are increasingly applied in life science, biology, and point-of-care applications due to their combined acoustofluidic sensing and actuating properties. Despite the advances in this field, there remain significant gaps in interfacing hardware and control strategies to facilitate system integration with high performance and low cost. In this work, we present a versatile, and digitally controlled acoustofluidic platform by demonstrating key functions for biological assays such as droplet transportation and mixing using a closed-loop feedback control with image recognition. Moreover, we integrate optical detection by demonstrating in-situ fluorescence sensing capabilities with a standard camera and digital filters, bypassing the need for expensive and complex optical setups. The Acousto-Pi setup is based on open-source Raspberry Pi hardware and 3D printed housing, and the SAW devices are fabricated with piezoelectric thin film on a metallic substrate. The platform enables the control of droplet position and speed for sample processing (mixing and dilution of samples), as well as the control of temperature based on acousto-heating, offering embedded processing capability. It can be operated remotely while recording the measurements in cloud databases towards integrated in-field diagnostic applications such as disease outbreak control, mass healthcare screening and food safety

PDE Modeling of a Microfluidic Thermal Process for Genetic Analysis Application

This paper details the infinite dimensional dynamics of a prototype microfluidic thermal process that is used for genetic analysis purposes. Highly effective infinite dimensional dynamics, in addition to collocated sensor and actuator architecture, require the development of a precise control framework to meet the very tight performance requirements of this system, which are not fully attainable through conventional lumped modeling and controller design approaches. The general partial differential equations describing the dynamics of the system are separated into steady-state and transient parts which are derived for a carefully chosen three-dimensional axisymmetric model. These equations are solved analytically, and the results are verified using an experimentally verified precise finite element method (FEM) model. The final combined result is a framework for designing a precise tracking controller applicable to the selected lab-on-a-chip device

Optimisation of Microfluidic Flow Systems

This project investigates the fluid flow and heat transfer in microfluidic flow systems using Computational Fluid Dynamics (CFD) and experiments. The first part of this work focuses on developing a CFD - enabled optimisation methodology of the geometrical features of i) a microfluidic heatsink design and ii) a single-phase (SP) continuous-flow (CF) Polymerase Chain Reaction (PCR) Device. This is achieved using COMSOL Multiphysics 5.4 ®to simulate the fluid flow, heat transfer (and PCR kinetics for the case of the microfluidic PCR device). Optimisation problems are then formed, selecting objective functions related to the performance of the devices. Design of Experiments is then used together with COMSOL Multiphysics 5.4 ® to collect the values of the objective functions over the design domain. Matlab© is then used to generate the response surfaces of the objective functions, using different techniques, locate the optimum design solutions (genetic algorithm, multi-level coordinate search method) and obtain the Pareto front for the cases of multi-objective optimisation problems. Results of this work indicate the possibility of significantly enhancing the performance of SP-CF-PCR devices in terms of the DNA amplification, device volume, total operating time and total pressure drop by up to 16.4%, 43.2%, 17.8% and 80.5% respectively, after applying the appropriate design modifications for each objective. The increase in the DNA amplification is achieved by increasing the channel width and residence times while minimising the channel height. The reduction in the device volume, total operating time and total pressure drop are achieved when using the smallest residence times and higher channel width. According to this investigation, the DNA amplification appears to be linked to the temperature uniformity and to the residence time in the extension zone. The second part of this work focuses on i) obtaining a better understanding of the role that the concentration and presence of droplets play in conjugate heat transfer phenomena in droplet-laden flows, ii) creating and optimising a reusable, cheap and easy-to-fabricate device that can perform Melting Curve Analysis (MCA), in order to facilitate the work of a group of biologists at the University of Leeds. More specifically, this device aims to check for the presence of rare DNA species and possible contaminations in their collected samples in a fast, robust and cheap way, by testing if the DNA product has a unique melting temperature. The experimental setup is designed after performing a series of simulations using COMSOL Multiphysics 5.4 ®, considering different potential designs while at the same time simulating the energy requirements of the system. After finalising the design, a PID temperature controller is implemented on the Arduino Platform, achieving the required temperature difference between the two ends of the device. The results obtained during the experiments demonstrate a successful temperature control that is robust and does not require the adjustment of the PID parameters for the performance of similar experiments in the different temperature ranges tested

The 30/20 GHz flight experiment system, phase 2. Volume 2: Experiment system description

A detailed technical description of the 30/20 GHz flight experiment system is presented. The overall communication system is described with performance analyses, communication operations, and experiment plans. Hardware descriptions of the payload are given with the tradeoff studies that led to the final design. The spacecraft bus which carries the payload is discussed and its interface with the launch vehicle system is described. Finally, the hardwares and the operations of the terrestrial segment are presented

A multi-function, disposable, microfluidic module for mutation detection

Recognition of point mutations in a codon 12 of the K-ras gene, most frequently observed, is considered to be useful in the early diagnosis of several types of the human cancers. We have developed a multifunction, disposable, microfluidic module which detects low-abundant point mutations in human genomic DNA in modular architecture. Each functional component including a microfluidic PCR reactor, a passive diffusional micromixer reactor, and a microfluidic LDR reactor was separately designed and fabricated. Fluidic interconnects were also developed to make a fluidic passage between the functional components. Polycarbonate substrates were micro-molded, using hot embossing with micro-milled brass mold inserts to make all microfluidic components. Developed microassembly using passive alignment features, fabricated on all components, was used to assemble the functional components with the fluidic interconnects using an adhesive bonding technique. Thermal simulations were employed to ensure uniform thermal distributions in the microfluidic PCR and LDR reactors, to isolate the mixing junction in order to avoid heat–induced bubble formation in the passive micromixer reactor, and to have minimal thermal crosstalk due to the asymmetric thermal zones in the PCR and the LDR reactors. A control system was developed to control temperatures enabling thermal cycling in the microfluidic PCR and LDR reactor. LDR products were produced using the module within an hour with DNA sample, which had the ratio of 1:200. Total reaction time was about 67 minutes. By applying an enzyme as a purification of PCR products, a LDR analysis can be optimized and minimized to reduce the false positive signals and inconstant results generated by PCR products during the LDR. The purification system allowed us to successfully quantify the amount of mutant alleles in the genomic DNA. The high degree of accuracy in this module can also facilitate the detection of low-frequency point mutation occurred in other functional genes. This module, fabricated using replication technologies of polymers will be able to supply low cost, disposable detection tools for known disease-causing mutations and also expand to other PCR-based detection assays in diagnostic applications

Molecular Level Investigation of Staphylococci’s Resistance Mechanisms to Antibiotics

Polymerase chain reaction (PCR ) techniques development allows elaboration of many assays for identification of bacteria’s resistance mechanisms to antibiotics. Following this idea, the results of molecular level investigation of bacteria’s resistance mechanisms to antibiotics may give many opportunities to find more rapid methods for identifying the genes which are responsible for antibiotic resistance induction. The aim of this study was to investigate antibiotic resistance genes in Staphylococcus bacteria on molecular level. As classes of antibiotics it was used macrolides-lincosamides-streptogramin B (MLSB) and beta-lactams. In the proposed study the bacterial strains are represented by 50 isolates of Staphylococcus. The bacterial strains were analyzed using polymerase chain reaction to identify the nuc, tuf, tst, sea, pathogenic activity genes. After this, the bacteria were tested for ermA, ermB, ermC genes and for mecA, femA which are involved in resistance to macrolides, lincosamides, streptogramin B and to beta-lactams, respectively. The presence or the absence of these genes confirms that tested strains are resistant to specific antibiotic or not. Bacteria pathogenic activity was emphasized by genes as follows: sea (enterotoxin) which was found at all isolates, tst (toxic shock toxin) gene was not detected in any of isolates and tuf gene (elongation factor) was obtained with one pair of primers. Resistance to beta-lactams was evidenced by the presence of mecA in all isolates and femA in some strains. Each of ermC, ermA and ermB, macrolides-lincosamides-streptogramin B resistance genes, were detected

NASA Tech Briefs, May 2012

Topics covered include: An "Inefficient Fin" Non-Dimensional Parameter to Measure Gas Temperatures Efficiently; On-Wafer Measurement of a Multi-Stage MMIC Amplifier with 10 dB of Gain at 475 GHz; Software to Control and Monitor Gas Streams; Miniaturized Laser Heterodyne Radiometer (LHR) for Measurements of Greenhouse Gases in the Atmospheric Column; Anomaly Detection in Test Equipment via Sliding Mode Observers; Absolute Position of Targets Measured Through a Chamber Window Using Lidar Metrology Systems; Goldstone Solar System Radar Waveform Generator; Fast and Adaptive Lossless Onboard Hyperspectral Data Compression System; Iridium Interfacial Stack - IrIS; Downsampling Photodetector Array with Windowing; Optical Phase Recovery and Locking in a PPM Laser Communication Link; High-Speed Edge-Detecting Line Scan Smart Camera; Optical Communications Channel Combiner; Development of Thermal Infrared Sensor to Supplement Operational Land Imager; Amplitude-Stabilized Oscillator for a Capacitance-Probe Electrometer; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Histogrammatic Method for Determining Relative Abundance of Input Gas Pulse; Predictive Sea State Estimation for Automated Ride Control and Handling - PSSEARCH; LEGION: Lightweight Expandable Group of Independently Operating Nodes; Real-Time Projection to Verify Plan Success During Execution; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Web-Based Customizable Viewer for Mars Network Overflight Opportunities; Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations; Fabrication of an Absorber-Coupled MKID Detector; Graphene Transparent Conductive Electrodes for Next- Generation Microshutter Arrays; Method of Bonding Optical Elements with Near-Zero Displacement; Free-Mass and Interface Configurations of Hammering Mechanisms; Wavefront Compensation Segmented Mirror Sensing and Control; Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration; Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications; Electrochemical Ultracapacitors Using Graphitic Nanostacks; Improved Whole-Blood-Staining Device; Monitoring Location and Angular Orientation of a Pill; Molecular Technique to Reduce PCR Bias for Deeper Understanding of Microbial Diversity; Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars; High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle; PRTs and Their Bonding for Long-Duration, Extreme-Temperature Environments; Mid- and Long-IR Broadband Quantum Well Photodetector; 3D Display Using Conjugated Multiband Bandpass Filters; Real-Time, Non-Intrusive Detection of Liquid Nitrogen in Liquid Oxygen at High Pressure and High Flow; Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators; Dual-Compartment Inflatable Suitlock; Large-Strain Transparent Magnetoactive Polymer Nanocomposites; Thermodynamic Vent System for an On-Orbit Cryogenic Reaction Control Engine; Time Distribution Using SpaceWire in the SCaN Testbed on ISS; and Techniques for Solution- Assisted Optical Contacting