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Surface functionalization of silica microparticles for capillary electrochromatography (CEC)

Description: We derivatized small (0.5 -3 {mu}m) silica particles by silating their surfaces with long-chain alkyl substituted silanes. These functionalized particles were packed into 100 {mu}m capillaries and used as stationary phases for capillary electrochromatography. The particles supported electroosmotic flow in mixtures of acetonitrile and aqueous buffer (4 mM sodium tetraborate or 2mM TRIS). The columns were used to separate mixtures of organic analytes demonstrating the effectiveness of the functionalized stationary phase.
Date: January 1, 1997
Creator: Shepodd, T.J.; Anex, D.S. & Rognlien, J.
Partner: UNT Libraries Government Documents Department

Comparison of Ross` capillary barrier diversion formula with detailed numerical simulations

Description: Ross developed an analytical relationship to calculate the diversion length of a tilted fine-over-coarse capillary barrier. Oldenburg and Pruess compared simulation results using upstream and harmonic weighting to the diversion length predicted by Ross formula with mixed results; the qualitative agreement is reasonable but the quantitative comparison is poor, especially for upstream weighting. The proximity of the water table to the fine-coarse interface at breakthrough is a possible reason for the poor agreement. In the present study, the Oldenburg and Pruess problem is extended to address the water table issue. When the water table is sufficiently far away from the interface at breakthrough, good qualitative and quantitative agreement is obtained using upstream weighting.
Date: April 1, 1997
Creator: Webb, S.W.
Partner: UNT Libraries Government Documents Department

Rapid Screening of Complex Chemical Samples via Capillary Array Analysis

Description: This report is a summary of the results of a two-year Laboratory-Directed Research and Development (LDRD) project that developed instrumentation and methods for capillary array analysis. During the course of this project, a new capillary array electrochromatography instrument was developed to perform eight simultaneous separations and provide complementary chromatographic information from each column on a single sample.
Date: November 1, 1998
Creator: Anex, D. S. & Neyer, D. W.
Partner: UNT Libraries Government Documents Department

Inverse modeling of a multistep outflow experiment fordetermining hysteretic hydraulic properties

Description: A new, closed-form hysteretic model of the capillary pressure-saturation and relative permeability-saturation relationship has been implemented into ITOUGH2. The hysteretic capillary pressure function is based on the van Genuchten model, with a modified version of the dependent domain model of Mualem to describe the scanning curves. Hysteresis in the relative permeability relations is considered to be mainly a result of nonwetting fluid entrap- ment. The hysteresis model was used in combination with inverse modeling techniques to examine the potential of a simple drainage- imbibition experiment to determine hysteretic hydraulic properties.
Date: May 1, 1998
Creator: Faybishenko, B.; Finsterle, S. & Sonnenborg, T.O.
Partner: UNT Libraries Government Documents Department

Development of an electromagnetically actuated mercury microvalve

Description: The development of microscale fluid handling components has been recognized as a crucial element in the design of microscale chemical detection systems. Recently, work has been undertaken at Sandia National Laboratories to construct a valve that uses a small mercury droplet to control the flow of gas through capillary passages. Electromagnetic forces that are provided by small permanent magnets and a current supply are used to drive the mercury into position. Driving the mercury droplet into a tapered passage halts gas flow through a capillary, while surface tension forces prevent the mercury from passing through the passage. Models have been developed to describe the movement of the mercury droplet and the sealing of the gas passage, and millimeter-scale units have been tested to explore design options. Predictions from the model show that a valve with 10 micron sized features can seal against pressures up to 1.5 atmospheres. Experiments have highlighted the promise of mercury valves and demonstrated problems that can arise from contamination of the mercury.
Date: August 1, 1998
Creator: Adkins, D.R. & Wong, C.C.
Partner: UNT Libraries Government Documents Department

Microscale Zeta Potential Evaluation Using Streaming Current Measurements

Description: We present a method for determination of zeta potential in capillaries and microscale devices. The use of streaming current measurements under pressure eliminates the need for high voltage measurements while providing a relatively simple means of approximating the zeta potential. This technique finds application in evaluation of coatings as well as materials for separations media and electrokinetic pumping. We will discuss the theory, in which sample porosity and tortuosity information are not required, and we will present zeta potentials of some organic and inorganic media.
Date: May 1, 2001
Creator: Jr., E.R. Hasselbrink; Hunter, M.C.; Jr., W.R. Even & Irvin, J.A.
Partner: UNT Libraries Government Documents Department

Influence of wettability on constitutive relations and its role in upscaling

Description: The lattice Boltzmann (LB) method is applied to simulating multifluid flow in porous media at sub-pore resolution to determine constitutive behaviors. The authors address the importance of the LB technique for identifying process based constitutive relationships, and demonstrate its application through analysis of the influence of wettability on interfacial areas and constitutive relationships. Porous media surface wettability is varied from uniformly strongly wetted by the resident fluid through strongly wetted by the displacing fluid. Spatially variable wettability is also demonstrated. Primary imbibition and drainage displacements are run, and interfacial areas (IFA) as a function of time are determined and compared. Results indicate that wettability is an important factor in displacement behavior and resulting interfacial area. Primary imbibition in a strongly wet material under capillary dominated flows produces film flow, resulting in high IFAs that decrease with increasing saturation and viscous forces. Primary drainage produces initially high IFA that decreases slightly with increasing saturation or pressure drop. Surfaces with spatially variable wetting can have a strong influence on resulting fluid distributions and fluid flow.
Date: July 1, 1998
Creator: Soll, W. E.; Gray, W. G. & Tompson, A. F. B.
Partner: UNT Libraries Government Documents Department

Separation of ions in acidic solution by capillary electrophoresis

Description: Capillary electrophoresis (CE) is an effective method for separating ionic species according to differences in their electrophoretic mobilities. CE separations of amino acids by direct detection are difficult due to their similar electrophoretic mobilities and low absorbances. However, native amino acids can be separated by CE as cations at a low pH by adding an alkanesulfonic acid to the electrolyte carrier which imparts selectivity to the system. Derivatization is unnecessary when direct UV detection is used at 185 nm. Simultaneous speciation of metal cations such as vanadium (IV) and vanadium (V) can easily be performed without complexation prior to analysis. An indirect UV detection scheme for acidic conditions was also developed using guanidine as the background carrier electrolyte (BCE) for the indirect detection of metal cations. Three chapters have been removed for separate processing. This report contains introductory material, references, and general conclusions. 80 refs.
Date: October 8, 1997
Creator: Thornton, M.
Partner: UNT Libraries Government Documents Department

Proboscis container shapes for the USML-2 interface configuration experiment

Description: Small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. Such behavior suggests a means for managing fluids in microgravity and, as one specific possible application, for the accurate determination of contact angle. In connection with this application, the authors discuss certain containers designed for the forthcoming USML-2 Glovebox Interface Configuration Experiment (ICE) and depict their behavior in preliminary drop tower experiments. The containers are in the form of a circular cylinder with two diametrically opposed {open_quotes}proboscis{close_quotes} protrusions. These shapes are based on the canonical (single) proboscis containers introduced mathematically, which have the properties in the absence of gravity that (i) fluid rises arbitrarily high over the entire proboscis for contact angles less than or equal to a critical value and (ii) the size of the proboscis can be made relatively as large a portion of the container cross section as desired. These properties allow overcoming some of the practical limitations of wedge containers; for the latter too little fluid may participate in the shift at a critical contact angle to be easily observable. The authors include some background material, where computational results for the double proboscis containers are presented.
Date: May 1, 1995
Creator: Concus, P.; Finn, R. & Weislogel, M.
Partner: UNT Libraries Government Documents Department

Comparison of Residual Saturation and Capillary Pressure Model with UNSODA Data

Description: The capillary pressure model correlates drainage and imbibition data from the UNSODA database, provided that the data incorporate the entry head, a minimum displacement required for drainage to begin. According to the model, the imbibition pressure equals the drainage pressures at a critical minimum saturation of 0.301; below this critical saturation, no additional reversible drainage should occur. Some of the UNSODA data sets had a minimum saturation approximately half this value. The difference is attributed to the presence of fissures, which would lower the residual wetting and critical minimum saturations by reducing the fraction of the void volume controlled by capillary pores. If the UNSODA saturations are adjusted for this discrepancy, a probability distribution of minimum saturations for each data set peaks near the predicted critical minimum saturation. Maximum saturations for each data set have a peak near the predicted residual nonwetting saturation of 0.884.
Date: April 1, 2004
Creator: LAURINAT, JAMESE.
Partner: UNT Libraries Government Documents Department

HIGH RESOLUTION PREDICTION OF GAS INJECTION PROCESS PERFORMANCE FOR HETEROGENEOUS RESERVOIRS

Description: This report outlines progress in the third 3 quarter of the first year of the DOE project ''High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs.'' A simple theoretical formulation of vertical flow with capillary/gravity equilibrium is described. Also reported are results of experimental measurements for the same systems. The results reported indicate that displacement behavior is strongly affected by the interfacial tension of phases that form on the tie line that extends through the initial oil composition.
Date: June 30, 2001
Creator: Franklin M. Orr, Jr.
Partner: UNT Libraries Government Documents Department

An AC magnetohydrodynamic micropump: towards a true integrated microfluidic system

Description: An AC Magnetohydrodynamic (MHD) micropump has been demonstrated in which the Lorentz force is used to propel an electrolytic solution along a microchannel etched in silicon. This micropump has no moving parts, produces a continuous (not pulsatile) flow, and is compatible with solutions containing biological specimens. micropump, using the Lorentz force as the pumping mechanism for biological analysis. The AC Magnetohydrodynamic (MHD) micropump investigated produces a continuous flow and allows for complex microchannel design.
Date: March 1, 1999
Creator: Lee, A P; Lemoff, A V; McConaghy, C F & Miles, R R
Partner: UNT Libraries Government Documents Department

Fundamentals of reservoir surface energy as related to surface properties, wettability, capillary action, and oil recovery from fractured reservoirs by spontaneous imbibition

Description: The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the nonwetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed-wet rocks. Imbibition measurements will include ...
Date: February 1, 2006
Creator: Morrow, Norman R.; Fischer, Herbert; Li, Yu; Mason, Geoffrey; Ruth, Douglas; Seth, Siddhartha et al.
Partner: UNT Libraries Government Documents Department

Resolving fundamental limits of adhesive bonding in microfabrication.

Description: As electronic and optical components reach the micro- and nanoscales, efficient assembly and packaging require the use of adhesive bonds. This work focuses on resolving several fundamental issues in the transition from macro- to micro- to nanobonding. A primary issue is that, as bondline thicknesses decrease, knowledge of the stability and dewetting dynamics of thin adhesive films is important to obtain robust, void-free adhesive bonds. While researchers have studied dewetting dynamics of thin films of model, non-polar polymers, little experimental work has been done regarding dewetting dynamics of thin adhesive films, which exhibit much more complex behaviors. In this work, the areas of dispensing small volumes of viscous materials, capillary fluid flow, surface energetics, and wetting have all been investigated. By resolving these adhesive-bonding issues, we are allowing significantly smaller devices to be designed and fabricated. Simultaneously, we are increasing the manufacturability and reliability of these devices.
Date: April 1, 2004
Creator: Hall, Jessica S.; Frischknecht, Amalie Lucile; Emerson, John Allen; Adkins, Douglas Ray; Kent, Michael Stuart; Read, Douglas H. et al.
Partner: UNT Libraries Government Documents Department

On Two-Phase Relative Permeability and Capillary Pressure ofRough-Walled Rock Fractures

Description: This paper presents a conceptual and numerical model of multiphase flow in fractures. The void space of real rough-walled rock fractures is conceptualized as a two-dimensional heterogeneous porous medium, characterized by aperture as a function of position in the fracture plane. Portions of a fracture are occupied by wetting and nonwetting phase, respectively, according to local capillary pressure and accessibility criteria. Phase occupancy and permeability are derived by assuming a parallel-plate approximation for suitably small subregions in the fracture plane. For log-normal aperture distributions, a simple approximation to fracture capillary pressure is obtained in closed form; it is found to resemble the typical shape of Leverett's j-function. Wetting and non-wetting phase relative permeabilities are calculated by numerically simulating single phase flows separately in the wetted and non-wetted pore spaces. Illustrative examples indicate that relative permeabilities depend sensitively on the nature and range of spatial correlation between apertures. It is also observed that interference between fluid phases flowing in a fracture tends to be strong, with the sum of wetting and nonwetting phase relative permeabilities being considerably less than 1 at intermediate saturations.
Date: September 1989
Creator: Pruess, K. & Tsang, Y. W.
Partner: UNT Libraries Government Documents Department

Fundamentals of Reservoir Surface Energy as Related to Surface Properties, Wettability, Capillary Action, and Oil Recovery from Fractured Reservoirs by Spontaneous Imbibition

Description: The objective of this project is to increase oil recovery from fractured reservoirs through improved fundamental understanding of the process of spontaneous imbibition by which oil is displaced from the rock matrix into the fractures. Spontaneous imbibition is fundamentally dependent on the reservoir surface free energy but this has never been investigated for rocks. In this project, the surface free energy of rocks will be determined by using liquids that can be solidified within the rock pore space at selected saturations. Thin sections of the rock then provide a two-dimensional view of the rock minerals and the occupant phases. Saturations and oil/rock, water/rock, and oil/water surface areas will be determined by advanced petrographic analysis and the surface free energy which drives spontaneous imbibition will be determined as a function of increase in wetting phase saturation. The inherent loss in surface free energy resulting from capillary instabilities at the microscopic (pore level) scale will be distinguished from the decrease in surface free energy that drives spontaneous imbibition. A mathematical network/numerical model will be developed and tested against experimental results of recovery versus time over broad variation of key factors such as rock properties, fluid phase viscosities, sample size, shape and boundary conditions. Two fundamentally important, but not previously considered, parameters of spontaneous imbibition, the capillary pressure acting to oppose production of oil at the outflow face and the pressure in the non-wetting phase at the no-flow boundary versus time, will also be measured and modeled. Simulation and network models will also be tested against special case solutions provided by analytic models. In the second stage of the project, application of the fundamental concepts developed in the first stage of the project will be demonstrated. The fundamental ideas, measurements, and analytic/numerical modeling will be applied to mixed-wet rocks. Imbibition measurements will include ...
Date: June 30, 2008
Creator: Morrow, Norman; Fischer, Herbert; Li, Yu; Mason, Geoffrey; Ruth, Douglas; Seth, Siddhartha et al.
Partner: UNT Libraries Government Documents Department

Experimental Investigation of Relative Permeability Upscaling from the Micro-Scale to the Macro-Scale

Description: During this reporting period, achieved the milestone of using Optical Coherence Imaging (OCI) to image to the back of the first layer of grains in a sandstone sample. This was the first time that OCI was used to image through sandstone. Information on grain geometry was obtained as deep as 400 microns into the sample. This report also describes the work performed to achieve the milestone on the measurement of interfacial area per volume, capillary pressure and saturation in two dimensional micromodels structures that are statistically similar to real porous media. This report contains the first quantitative experimental measurements of interfacial area per volume in any system.
Date: March 1, 2001
Creator: Yu, Ping; Giodao, Nicholas; Cheng, JiangTao; Mustata, Mirela; Headley, William; Chen, Diaquan et al.
Partner: UNT Libraries Government Documents Department

Band spreading in two-dimensional microchannel turns for electrophoretic or electroosmotic species transport

Description: Analytical and numerical methods are employed to investigate species transport by electrophoretic or electroosmotic motion in the curved geometry of a two-dimensional turn. Closed-form analytical solutions describing the turn-induced diffusive and dispersive spreading of a species band are presented for both the low and high Peclet number limits. The authors find that the spreading due to dispersion is proportional to the product of the turn included angle and the Peclet number at low Peclet numbers. It is proportional to the square of the included angle and independent of the Peclet number when the Peclet number is large. A composite solution applicable to all Peclet numbers is constructed from these limiting behaviors. Numerical solutions for species transport in a turn are also presented over a wide range of the included angle and the mean turn radius. Based on comparisons between the analytical and numerical results, the authors find that the analytical solutions provide very good estimates of both dispersive and diffusive spreading provided that the mean turn radius exceeds the channel width. These new solutions also agree well with data from a previous study. Optimum conditions minimizing total spreading in a turn are presented and discussed.
Date: March 1, 2000
Creator: Griffiths, S. K. & Nilson, R. H.
Partner: UNT Libraries Government Documents Department

Microfluidic Engineering

Description: The ability to generate high pressures using electrokinetic pumping of liquid through porous media is reported. Pressures in excess of 8000 psi have been achieved using capillaries (< 100 {micro}m i.d.) packed with micron-size silica beads. A model is presented which accurately predicts absolute pressures, flowrates and power conversion efficiencies as well as the experimentally observed dependencies on pore size, applied electric field and electrical properties of the fluid. This phenomenon offers the possibility of creating a new class of microscale fluid devices, electrokinetic pumps and valves, where the performance improves with scale-down by taking advantage of microscale processes.
Date: December 1, 1998
Creator: Paul, Phillip H.
Partner: UNT Libraries Government Documents Department