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Absolute wavelength measurement and fine structure determination in /sup 7/Li II

Description: The energy levels of two-electron atoms continue to provide rigorous tests of relativistic quantum theory, and of correlation effects within a multi-particle system. These interactions are determined perturbatively, with several approximations, and theoretical results often differ. It is critical to provide precise measurements of absolute wavelengths connecting these atomic energy levels to obtain a resolution of the precision of the different parts of such complex calculations. In this work, we report a high precision optical measurements in the 1s2s /sup 3/S - 1s2p /sup 3/P multiplet of Li II using fast-beam laser spectroscopy. A collinear interaction using both parallel and antiparallel laser and ion beams allows both for precise elimination of large Doppler shifts, and for a strong kinematic narrowing of the observed resonances, as compared with thermal beam experiments. The wavelengths of the observed resonance fluorescence radiation are determined by comparing them with simultaneously recorded saturated absorption profiles of molecular iodine hyperfine components. In turn, the absolute wavelengths of the iodine lines are obtained from precisely calibrated Fabry-Perot etalon fringes in a separate experiment. The final precision of the Li II wavelengths is 5 parts in 10/sup 9/, which is at a level of precision of 80 ppM of the QED corrections in the transition. 3 refs., 1 figs., 1 tab.
Date: January 1, 1985
Creator: Riis, E.; Berry, H.G.; Poulsen, O.; Lee, S.A. & Tang, S.Y.
Partner: UNT Libraries Government Documents Department

Ambient-Temperature Passive Magnetic Bearings for Flywheel Energy Storage Systems

Description: Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag forces, or from mechanical-hysteritic losses that may occur in the rotor. Our design problem thus becomes one of calculating and/or measuring the relevant stiffnesses and drag coefficients of the various elements and comparing our results with the theory so as to assure that the cited stability criteria are satisfied.
Date: May 26, 2000
Creator: Bender, D. & Post, R.
Partner: UNT Libraries Government Documents Department

Analysis of Dyes Extracted from Millimeter-Size Nylon Fibers by Micellar Electrokinetic Chromatography

Description: The Learning Objective is to present to the forensic community a potential qualitative/quantitative method for trace-fiber color comparisons using micellar electrokinetic chromatography (MEKC). Developing a means of analyzing extracted dye constituents from millimeter-size nylon fiber samples was the objective of this research initiative. Aside from ascertaining fiber type, color evaluation and source comparison of trace-fiber evidence plays a critical role in forensic-fiber examinations. Literally thousands of dyes exist to date, including both natural and synthetic compounds. Typically a three-color-dye combination is employed to affect a given color on fiber material. The result of this practice leads to a significant number of potential dye combinations capable of producing a similar color and shade. Since a typical forensic fiber sample is 2 mm or less in length, an ideal forensic dye analysis would qualitatively and quantitatively identify the extracted dye constituents from a sample size of 1 mm or smaller. The goal of this research was to develop an analytical method for comparing individual dye constituents from trace-fiber evidence with dyes extracted from a suspected source, while preserving as much of the original evidence as possible.
Date: July 30, 2001
Creator: Lewis, L.A.
Partner: UNT Libraries Government Documents Department

APPLICATION OF THE LASAGNA{trademark} SOIL REMEDIATION TECHNOLOGY AT THE DOE PADUCAH GASEOUS DIFFUSION PLANT

Description: The Paducah Gaseous Diffusion Plant (PGDP), owned by the Department of Energy (DOE), has been enriching uranium since the early 1950s. The enrichment process involves electrical and mechanical components that require periodic cleaning. The primary cleaning agent was trichloroethene (TCE) until the late 1980s. Historical documentation indicates that a mixture of TCE and dry ice were used at PGDP for testing the integrity of steel cylinders, which stored depleted uranium. TCE and dry ice were contained in a below-ground pit and used during the integrity testing. TCE seeped from the pit and contaminated the surrounding soil. The Lasagna{trademark} technology was identified in the Record of Decision (ROD) as the selected alternative for remediation of the cylinder testing site. A public-private consortium formed in 1992 (including DOE, the U.S. Environmental Protection Agency, and the Kentucky Department for Environmental Protection, Monsanto, DuPont, and General Electric) developed the Lasagna{trademark} technology. This innovative technology employs electrokinetics to remediate soil contaminated with organics and is especially suited to sites with low permeability soils. This technology uses direct current to move water through the soil faster and more uniformly than hydraulic methods. Electrokinetics moves contaminants in soil pore water through treatment zones comprised of iron filings, where the contaminants are decomposed to basic chemical compounds such as ethane. After three years of development in the laboratory, the consortium field tested the Lasagna{trademark} process in several phases. CDM installed and operated Phase I, the trial installation and field test of a 150-square-foot area selected for a 120-day run in 1995. Approximately 98 percent of the TCE was removed. CDM then installed and operated the next phase (IIa), a year-long test on a 600-square-foot site. Completed in July 1997, this test removed 75 percent of the total volume of TCE down to a depth of 45 feet. TCE ...
Date: February 27, 2003
Creator: Swift, Barry D. & Tarantino, Joseph J., P. E.
Partner: UNT Libraries Government Documents Department

Are there background fields that can induce QED phase transitions at weak coupling

Description: The existence of a new, non-perturbative phase of QED as indicated by studies of Schwinger-Dyson equations and lattice calculations. The crucial question is whether the phase transition point can be driven down to {alpha} {approximately} 1/137 presumably by appropriate background fields. It appears that magnetic fields potentially can induce such a phase transition. Our investigation is related to our original conjecture that the anomalous e{sup +}e{sup {minus}} events at GSI are due to the decay of a new positronium system formed in the new QED phase which is induced by the electromagnetic fields of the heavy-ions. 25 refs.
Date: September 1, 1990
Creator: Ng, Y.J. (North Carolina Univ., Chapel Hill, NC (USA). Dept. of Physics and Astronomy) & Kikuchi, Y. (McGill Univ., Montreal, PQ (Canada). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Atomic collisions with 33-TeV lead ions

Description: Recent availability of relativistic and ultrarelativistic beams of heavy ions has permitted the first controlled studies of atomic collisions at energies sufficient to measure effects of several new basic phenomena. These include measurements substantiating recently predicted finite nuclear size effects resulting in a reduction in the total electronic energy loss of heavy ions in matter, and measurements of Coulomb collisions in which electrons are excited from the Dirac negative energy continuum. Measurements of total energy loss, free electron-positron pair production, and electron capture from pair production have been recently performed using 33-TeV Pb{sup 82+} ions from the CERN SPS accelerator in Geneva. Results of these studies are presented, along with comparisons with relevant theory.
Date: October 1, 1996
Creator: Vane, C.R.; Datz, S. & Krause, H.F.
Partner: UNT Libraries Government Documents Department

Atomic Physics Aspects of a Relativistic Nuclear Collider

Description: Atomic collision cross sections involving bare uranium nuclei are large at relativistic energies and will affect the design and operation of a relativistic nuclear collider (RNC). The most significant may be production of electron-positron pairs and muon pairs ({approx} 10{sup 8} per sec. and 2000 per sec. respectively for a 100 GeV/nucleon collider with a luminosity of 10{sup 27} cm{sup 2} s{sup -1}). Although the pair production is a direct measure of the luminosity it is also a large source of background and capture of an electron from the pair by one of the nuclei will result in the loss of the ion. Another important loss mechanism is Coulomb excitation of the giant nuclear dipole and giant nuclear quadrupole resonances. Storing and colliding bare and highly-stripped uranium opens up new possibilities for novel atomic physics experiments and an alternate approach for present experiments. As examples, the use of a collider for experiments to study spontaneous decay of the super-critical state (both positron production and x-ray production) of quasi-atoms of atomic number Z > 172, and a storage-ring measurement of the ground state hyperfine structure of hydrogen like thallium as a test of quantum electrodynamics (QED) are discussed.
Date: November 1, 1984
Creator: Gould, R.
Partner: UNT Libraries Government Documents Department

Atoms in Flight: The Remarkable Connections between Atomic and Hadronic Physics

Description: Atomic physics and hadron physics are both based on Yang Mills gauge theory; in fact, quantum electrodynamics can be regarded as the zero-color limit of quantum chromodynamics. I review a number of areas where the techniques of atomic physics provide important insight into the theory of hadrons in QCD. For example, the Dirac-Coulomb equation, which predicts the spectroscopy and structure of hydrogenic atoms, has an analog in hadron physics in the form of light-front relativistic equations of motion which give a remarkable first approximation to the spectroscopy, dynamics, and structure of light hadrons. The renormalization scale for the running coupling, which is unambiguously set in QED, leads to a method for setting the renormalization scale in QCD. The production of atoms in flight provides a method for computing the formation of hadrons at the amplitude level. Conversely, many techniques which have been developed for hadron physics, such as scaling laws, evolution equations, and light-front quantization have equal utility for atomic physics, especially in the relativistic domain. I also present a new perspective for understanding the contributions to the cosmological constant from QED and QCD.
Date: February 16, 2012
Creator: Brodsky, Stanley J.
Partner: UNT Libraries Government Documents Department

Axial currents, supercurrents and anomalies in supersymmetric QED

Description: The currents associated with the superconformal symmetries are defined as moments of the supercurrent, V/sub ..mu... All of the current (non-) conservation equations are known once the generalized trace of the supercurrent, D/sup ..cap alpha../V/sub ..cap alpha cap alpha../, is found. The superconformal anomalies are shown to have coefficients given by ..beta.. of the Callan-Symanzik equation. In super QED there is an additional U(1) axial current whose anomaly has a coefficient with no radiative corrections. 5 references.
Date: January 1, 1979
Creator: Clark, T.E.
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D&D of R. Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Collaborating researchers at the University of South Carolina (USC), Clemson University (CU), and the Savannah River Site (SRS) are investigating the fundamentals of a combined extraction and destruction process for the decontamination and decommissioning (D&D) of PCB-contaminated materials as found at DOE sites. Currently, the volume of PCBs and PCB contaminated wastes at DOE sites nationwide is approximately 19,000 m3. While there are a number of existing and proposed processes for the recovery and/or destruction of these persistent pollutants, none has emerged as the preferred choice. Therefore, this research focuses on combining novel processes to solve the problem. The research objectives are to investigate benign dense- fluid extraction with either carbon dioxide (USC) or hot water (CU), followed by destruction of the extracted PCBs via either electrochemical (USC) or hydrothermal (CU) oxidation. Based on the results of these investigations, a combined extraction and destruction process that incorporates the most successful elements of the various processes will be recommended for application to contaminated DOE sites.
Date: June 1, 2000
Creator: Matthews, Michael A.
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D&D of R. Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Collaborating researchers at the University of South Carolina (USC), Clemson University (CU), and the Savannah River Site (SRS) are investigating the fundamentals of a combined extraction and destruction process for the decontamination and decommissioning (D&D) of PCB-contaminated materials as found at DOE sites. Currently, the volume of PCBs and PCB contaminated wastes at DOE sites nationwide is approximately 19,000 m3. While there are a number of existing and proposed processes for the recovery and/or destruction of these persistent 4 pollutants, none has emerged as the preferred choice. Therefore, this research focuses on combining novel processes to solve the problem. The research objectives are to investigate benign dense-fluid extraction with either carbon dioxide (USC) or hot water (CU), followed by destruction of the extracted PCBs via either electrochemical (USC) or hydrothermal (CU) oxidation. Based on the results of these investigations, a combined extraction and destruction process that incorporates the most successful elements of the various processes will be recommended for application to contaminated DOE sites.
Date: June 1, 1999
Creator: Hamilton, Edward A.; Bruce, David A.; Oji, Lawrence; White, Ralph E.; Matthews, Michael A. & Thies, Mark C.
Partner: UNT Libraries Government Documents Department

BASIC ENGINEERING RESEARCH FOR D&D OF R REACTOR STORAGE POND SLUDGE: ELECTROKINETICS, CARBON DIOXIDE EXTRACTION, AND SUPERCRITICAL WATER OXIDATION

Description: Large quantities of mixed low level waste (MLLW) that fall under the Toxic Substances Control Act (TSCA) exist and will continue to be generated during D&D operations at DOE sites across the country. Currently, the volume of these wastes is approximately 23,500 m3, and the majority of these wastes (i.e., almost 19,000 m3) consist of PCBs and PCB-contaminated materials. Further, additional PCB-contaminated waste will be generated during D&D operations in the future. The standard process for destruction of this waste is incineration, which generates secondary waste that must be disposed, and the TSCA incinerator at Oak Ridge has an uncertain future. Beyond incineration, no proposed process for the recovery and/or destruction of these persistent pollutants has emerged as the preferred choice for DOE cleanup. The main objective of the project was to investigate and develop a deeper understanding of the thermodynamic and kinetic reactions involved in the extraction and destruction of polychlorinated biphenyls (PCBs) from low-level mixed waste solid matrices in order to provide data that would permit the design of a combined-cycle extraction/destruction process. The specific research objectives were to investigate benign dense-fluid extraction with either carbon dioxide (USC) or hot water (CU), followed by destruction of the extracted PCBs via either electrochemical (USC) or hydrothermal (CU) oxidation. Two key advantages of the process are that it isolates and concentrates the PCBs from the solid matrices (thereby reducing waste volume greatly and removing the remaining low-level mixed waste from TSCA control), and little, if any, secondary solvent or solid wastes are generated. This project was a collaborative effort involving the University of South Carolina (USC), Clemson University (CU), and Westinghouse Savannah River Company (WSRC) (including the Savannah River Technology Center, Facilities Decommissioning Division and Regulatory Compliance). T he project was directed and coordinated by the South Carolina Universities Research ...
Date: December 31, 2001
Creator: Matthews, Michael A.; Bruce,David; Davis,Thomas; Thies, Mark; Weidner, John & White, Ralph
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D and D of R Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Large quantities of mixed low level waste (MLLW) that fall under the Toxic Substances Control Act (TSCA) exist and will continue to be generated during D and D operations at DOE sites across the country. The standard process for destruction of MLLW is incineration, which has an uncertain future. The extraction and destruction of PCBs from MLLW was the subject of this research Supercritical Fluid Extraction (SFE) with carbon dioxide with 5% ethanol as cosolvent and Supercritical Waster Oxidation (SCWO) were the processes studied in depth. The solid matrix for experimental extraction studies was Toxi-dry, a commonly used absorbent made from plant material. PCB surrogates were 1.2,4-trichlorobenzene (TCB) and 2-chlorobiphenyl (2CBP). Extraction pressures of 2,000 and 4,000 psi and temperatures of 40 and 80 C were studied. Higher extraction efficiencies were observed with cosolvent and at high temperature, but pressure little effect. SCWO treatment of the treatment of the PCB surrogates resulted in their destruction below detection limits.
Date: April 1, 2002
Creator: Matthews, Michael A.; David A. Bruce,; Davis, Thomas A.; Thies, Mark C.; Weidner, John W. & White, Ralph E.
Partner: UNT Libraries Government Documents Department

Basic Engineering Research for D&D of R Reactor Storage Pond Sludge: Electrokinetics, Carbon Dioxide Extraction, and Supercritical Water Oxidation

Description: Large quantities of mixed low level waste (MLLW) that fall under the Toxic Substances Control Act (TSCA) exist and will continue to be generated during D&D operations at DOE sites across the country. Currently, the volume of these wastes is 23,500 m3, and the majority of these wastes (i.e., almost 19,000 m3) consist of PCBs and PCB-contaminated materials. No proposed process for the recovery and/or destruction of these persistent pollutants has emerged as the preferred choice for DOE cleanup. Collaborating researchers at the University of South Carolina (USC), Clemson University (Clemson University), and the Savannah River Technology Center (SRTC), under the direction of the South Carolina Universities Research and Education Foundation (SCUREF), have performed initial research and development on a combined PCB extraction/destruction process for the PCB-contaminated solids that are generated during D&D activities. Extraction is performed using either supercritical carbon dioxide (CO2) or hot, pressurized water. Destruction is accomplished by oxidation in supercritical or near-critical water. Two key aspects of the proposed process are that it isolates and concentrates the PCBs from the solid matrices (thereby reducing waste volume greatly), and little if any secondary solvent or solid wastes are generated.
Date: June 1, 2001
Creator: Matthews, Michael A.
Partner: UNT Libraries Government Documents Department

Beamstrahlung and QED backgrounds at future linear colliders

Description: This dissertation is a detailed study of several aspects of beamstrahlung and related phenomena. The problem is formulated as the relativistic scattering of an electron from a strong but slowly varying potential. The solution is readily interpreted in terms of a classical electron trajectory, and differs from the solution of the corresponding classical problem mainly in the effect of quantum recoil due to the emission of hard photons. When the general solution is expanded for the case of an almost-uniform field, the leading term is identical to the well-known formula for quantum synchrotron radiation. The first non-leading term is negligible in all cases of interest where the expansion is valid. In applying the standard synchrotron radiation formula to the beamstrahlung problem, the effects of radiation reaction on the emission of multiple photons can be significant for some machine designs. Another interesting feature is the helicity dependence of the radiation process, which is relevant to the case where the electron beam is polarized. The inverse process of coherent electron-positron pair production by a beamstrahlung photon is a potentially serious background source at future colliders, since low-energy pairs can exit the bunch at a large angle. Pairs can also be produced incoherently by the collision of the two photons, either real or virtual. The rates, spectra, and angular distributions for both the coherent and incoherent processes are estimated here. At a 1/2 TeV machine the incoherent process will be more common, resulting in roughly 10{sup 6} pairs per bunch crossing. One member of each pair is always pushed outward, at an angle determined by its energy, by the field of the oncoming bunch. In addition, a small number of pairs are initially produced with a comparable or larger angle.
Date: October 1, 1990
Creator: Schroeder, D.V.
Partner: UNT Libraries Government Documents Department

Binary electrokinetic separation of target DNA from background DNA primers.

Description: This report contains the summary of LDRD project 91312, titled ''Binary Electrokinetic Separation of Target DNA from Background DNA Primers''. This work is the first product of a collaboration with Columbia University and the Northeast BioDefense Center of Excellence. In conjunction with Ian Lipkin's lab, we are developing a technique to reduce false positive events, due to the detection of unhybridized reporter molecules, in a sensitive and multiplexed detection scheme for nucleic acids developed by the Lipkin lab. This is the most significant problem in the operation of their capability. As they are developing the tools for rapidly detecting the entire panel of hemorrhagic fevers this technology will immediately serve an important national need. The goal of this work was to attempt to separate nucleic acid from a preprocessed sample. We demonstrated the preconcentration of kilobase-pair length double-stranded DNA targets, and observed little preconcentration of 60 base-pair length single-stranded DNA probes. These objectives were accomplished in microdevice formats that are compatible with larger detection systems for sample pre-processing. Combined with Columbia's expertise, this technology would enable a unique, fast, and potentially compact method for detecting/identifying genetically-modified organisms and multiplexed rapid nucleic acid identification. Another competing approach is the DARPA funded IRIS Pharmaceutical TIGER platform which requires many hours for operation, and an 800k$ piece of equipment that fills a room. The Columbia/SNL system could provide a result in 30 minutes, at the cost of a few thousand dollars for the platform, and would be the size of a shoebox or smaller.
Date: October 1, 2005
Creator: James, Conrad D. & Derzon, Mark Steven
Partner: UNT Libraries Government Documents Department

Breakdown of QED vacuum and luminosity lifetime of a heavy ion collider

Description: During beam crossing at a Relativistic Heavy Ion Collider the peripheral electromagnetic field between the fully stripped ions in colliding bunches is sufficiently intense to induce copious particle production. In this manuscript the production of free pair e{sup +},e{sup {minus}} leptons and bound-electron plus free e{sup +} particles are addressed in detail. In particular, both perturbative and non-perturbative approaches to these reactions are addressed. Capturing a produced electron into a bound state of an atom is a charge changing reaction that may effect the useful machine luminosity lifetime. The analogies between strong field effects in heavy ion colliders and the next generation of linear colliders are also discussed. 12 refs., 2 figs.
Date: January 1, 1991
Creator: Rhoades-Brown, M.J.
Partner: UNT Libraries Government Documents Department

Can RHIC be used to test QED

Description: Three general subjects were addressed during the workshop. These subjects were: to understand the validity of the best available descriptions of e{sup +} e{sup {minus}} pair production in peripheral heavy ion collisions, especially for the domain where this process is known to be non-perturbative. To understand the prospects for using relativistic heavy ions to produce Higgs Bosons or Weak bosons (Z{sub 0}, W+, W{minus}). This production mechanism proceeds through the virtual two photon representation of the heavy ions, and is considered a reason for accelerating heavy ions in both the LHC and the SSC. To study the interference mechanisms between the two processes for hadron production in peripheral heavy ion collisions. These two processes are two photon exchange and two pomeron exchange.
Date: January 1, 1990
Creator: Fatyga, M.; Rhoades-Brown, M. & Tannenbaum, M.
Partner: UNT Libraries Government Documents Department

Capillary electrokinetic separations with optical detection. Technical progress report, February 1, 1994--January 31, 1995

Description: This multifarious research program is dedicated to the development of capillary electrokinetic separation techniques and associated optical methods of detection. Currently, research is directed at three general objectives. First, fundamental studies of pertinent separation and band broadening mechanisms are being conducted, with the emphasis on achieving rapid separations and understanding separation systems that include highly-ordered assemblies as running buffer additives. Second, instrumentation and methodologies associated with these capillary separation techniques are being advanced. Third, applications of these separation and detection systems should fill current voids in the capabilities of capillary separation techniques. In particular, it should be possible to perform rapid, highly efficient, and selective separations of hydrophobic compounds (e.g., higher MW polycyclic aromatic hydrocarbons (PAHs) and fullerenes), certain optical isomers, DNA fragments, and various pollutants including certain heavy metals.
Date: May 1, 1995
Creator: Sepaniak, M. J.
Partner: UNT Libraries Government Documents Department

Capillary Electrophoresis - Optical Detection Systems

Description: Molecular recognition systems are developed via molecular modeling and synthesis to enhance separation performance in capillary electrophoresis and optical detection methods for capillary electrophoresis. The underpinning theme of our work is the rational design and development of molecular recognition systems in chemical separations and analysis. There have been, however, some subtle and exciting shifts in our research paradigm during this period. Specifically, we have moved from mostly separations research to a good balance between separations and spectroscopic detection for separations. This shift is based on our perception that the pressing research challenges and needs in capillary electrophoresis and electrokinetic chromatography relate to the persistent detection and flow rate reproducibility limitations of these techniques (see page 1 of the accompanying Renewal Application for further discussion). In most of our work molecular recognition reagents are employed to provide selectivity and enhance performance. Also, an emerging trend is the use of these reagents with specially-prepared nano-scale materials. Although not part of our DOE BES-supported work, the modeling and synthesis of new receptors has indirectly supported the development of novel microcantilevers-based MEMS for the sensing of vapor and liquid phase analytes. This fortuitous overlap is briefly covered in this report. Several of the more significant publications that have resulted from our work are appended. To facilitate brevity we refer to these publications liberally in this progress report. Reference is also made to very recent work in the Background and Preliminary Studies Section of the Renewal Application.
Date: August 6, 2001
Creator: Sepaniak, M. J.
Partner: UNT Libraries Government Documents Department

A capillary valve for microfluidic systems.

Description: Microfluidic systems are becoming increasingly complicated as the number of applications grows. The use of microfluidic systems for chemical and biological agent detection, for example, requires that a given sample be subjected to many process steps, which requires microvalves to control the position and transport of the sample. Each microfluidic application has its own specific valve requirements and this has precipitated the wide variety of valve designs reported in the literature. Each of these valve designs has its strengths and weaknesses. The strength of the valve design proposed here is its simplicity, which makes it easy to fabricate, easy to actuate, and easy to integrate with a microfluidic system. It can be applied to either gas phase or liquid phase systems. This novel design uses a secondary fluid to stop the flow of the primary fluid in the system. The secondary fluid must be chosen based on the type of flow that it must stop. A dielectric fluid must be used for a liquid phase flow driven by electroosmosis, and a liquid with a large surface tension should be used to stop a gas phase flow driven by a weak pressure differential. Experiments were carried out investigating certain critical functions of the design. These experiments verified that the secondary fluid can be reversibly moved between its 'valve opened' and 'valve closed' positions, where the secondary fluid remained as one contiguous piece during this transport process. The experiments also verified that when Fluorinert is used as the secondary fluid, the valve can break an electric circuit. It was found necessary to apply a hydrophobic coating to the microchannels to stop the primary fluid, an aqueous electrolyte, from wicking past the Fluorinert and short-circuiting the valve. A simple model was used to develop valve designs that could be closed using an electrokinetic ...
Date: October 1, 2004
Creator: Cummings, Eric B.; Kanouff, Michael P. & Rush, Brian M.
Partner: UNT Libraries Government Documents Department