Abstracts from the College of Engineering
Undergraduate Summer Research Symposium August 9, 2006

Ordered alphabetically by student's last name

Edwards Gallo Hanft Hazelwood Manzella Palladino Rosborough,1,2 Seagraves Velaquez
deMoss Esquivel Grammatikos Kell Levandowsky Nelson Pavia,1,2 Rosen Selekman Walck
Doshi Fry Guerriero Kenaley Mancini Newman  Reichart Schein Stottmann

Improved Virus Removal Efficiency of Commercial Pitcher Water Filters through Addition of Zero-Valent Iron

Shellie L. deMoss, Steve C. Blackburn, Pei Chiu, and Yan Jin1
Department of Civil and Environmental Engineering,
1Department of Plant and Soil Sciences

Viruses are responsible for a large portion of waterborne diseases because they are difficult to remove from drinking water due to their small size.  In a recent paper (You et al., 2005), zero-valent iron was found to be capable of adsorbing waterborne viruses.  In this study we tested the effectiveness of two commercial pitcher water filters (PUR and Brita) to remove two model viruses, MS2 and x174, with and without addition of zero-valent iron to these filters.  The test was then repeated to assess the performance of the filters and zero-valent iron over time.  Preliminary results of these tests will be presented and their implications will be discussed.  Funding for this project is by the Engineering and Science Undergraduate Research program and also the American Veterans association.  Sponsors: University of Delaware Undergraduate Research Program Department of Veteran Affairs, Delaware Water Resources Center.

Characterization of Amphiphilic Peptide & Tri-Block Copolymer Self-Assembly With Atomic Force Microscopy

Ankur B. Doshi1, Matthew S. Lamm2, and Darrin J. Pochan2
1Department of Chemical Engineering, 2Department of Materials Science & Engineering

The atomic force microscope is an excellent surface-imaging device and is one of the most popular techniques used for imaging nanoscale matter.  Through the technique of atomic force microscopy (AFM), the task of investigating and characterizing various self-assemblies of amphiphilic peptides and tri-block copolymers under various solution conditions is feasible.  Two amphiphilic peptides in particular, consisting of mostly alternating hydrophobic valine and hydrophilic lysine residues, were examined under conditions where they assemble into β-sheet fibrils of varying morphology.  These investigations provide insightful information in many different fields, such as scaffolds for tissue engineering and protein folding.  They can also serve as models for different organ-specific amyloidal and prion diseases, such as Alzheimer’s, Huntington’s, Parkinson’s, Creutzfeldt-Jakob, and type II Diabetes.  In addition, the unique torodial micelle morphology of an ABC tri-block copolymer was also characterized by AFM. Fundamentals of block copolymer physics in solution have potential applications in nanotechnology and drug delivery.  This research was funded by the Science and Engineers Scholars program.

Gelation Kinetics of β-Hairpin Oligopeptides Using Laser Tweezer Microrheology

Jonathan Edwards1, Indira Gopal1, Joel P. Schneider2, and Eric M. Furst1
Department of Chemical Engineering,2Department of Chemistry and Biochemistry

The gelation kinetics of the peptide MAX1 are studied using laser tweezer microrheology.  Unfolded, this peptide exists as an aqueous solution with the viscosity of water. Self-assembly is initiated by environmental changes such as pH, temperature or ionic strength.  This mechanism permits control of the kinetics of material formation for application such as cell encapsulation.  The experimental technique involves active manipulation of micron-scale particles in the gel solution with an optical trap. The trapped probe particle is forced in a sinusoidal motion, and simultaneously the response of the particle is measured with a quadrant photodiode and lock-in-amplifier.  The phase angle and amplitude of the particle are recorded and used to calculate the viscoelastic moduli as a function of time. The dependence of the moduli on concentration and ionic strength of the buffer are also examined.  The nominally defined gel point for various buffer strengths and peptide concentrations shows good agreement with multiple particle tracking, a passive micrheological technique.  We acknowledge work from the NIH (2 P20 RR016472-04) under the INBRE program of the NCRR and NIH R01 EB003172-01.

Evaluation of a Tool to Identify Concerns in Large Programs
Zak Fry and Lori Pollock
Department of Computer and Information Science

Maintenance tasks comprise a large portion of software development time.  Generally a maintenance task focuses on fixing a subset of code that relates to one idea or “concern” within<>the program.  A programmer’s ability to complete these tasks easily and in a timely fashion depends on effective and efficient methods of identifying these concerns in the program code. Unfortunately, identifying all of the program's methods involved in a particular concern is a difficultand tedious task.  In addition, the relationships between methods comprising a particular concern<>are not always obvious. We have developed a tool called FindConcept that, given a well formed query of verbs and nouns of a program, will graph the methods associated with a concern in the <>program based on the program's call hierarchy, implementation, and preconditions.  We are now focusing on proving our FindConcept tool’s worth against other state of the art tools.  We designed an experiment to compare our natural language processing tool against competitive lexical and information retrieval tools to determine which tool yields the highest precision and recall.  This study also attempts to objectively measure the ease of use and usability of all three tools to get a better understanding of overall performance. We are currently in the midst o
conducting the experiment and analyzing the data.

Cancer Nanotechology: Size Dependent Magnetic Nanoparticle Hyperthermia

Debbie Gallo, Michael J. Bonder, Srini Balakrishnan, and George C. Hadjipanayis
Department of Physics and Astronomy

Fe nanoparticles coated with Polyethylene Glycol (PEG) are being considered as a localized Hyperthermia Treatment for Cancer.  Temperatures in the range of 43ºC and 50ºC are needed for an effective treatment.   In this study, samples being tested are synthesized using a borohydride reduction of metal salts in the presence of PEG.  In this way, Fe nanoparticles are coated with a biocompatible layer for protection against the body’s immune system.  For this experiment, through magnetic separation, the effect of particle size of an as-synthesized sample on temperature was investigated.  Particle sizes range in diameter from 5-50nm with a mean around 10-20nm as supported by the transmission electron microscopy (TEM).  The particles are separated using a magnetic capture device, resulting in smaller particles being filtered through the field gradient.  The as-synthesized sample has a broad particle size distribution with a mean of 20.4 + 7.4nm while the magnetically separated samples have increasingly narrow distributions ranging from 19.5+4.1 and 16.2+3.6nm respectively.  The magnetic properties of the separated particles were also considered.  Coercivities of the as-synthesized samples tend to be large, varying from 100-210Oe while the separated smaller particles have coercivities decreased between roughly 50-200Oe.  Upon application of an AC magnetic field, heating samples with different particle sizes occurred.  Data collected supports the hypothesis that the smaller particles give the greatest contribution to heating.  Hence, using smaller particles, hyperthermia treatments become feasible as equilibrium temperatures in excess of 43ºC were achieved.  Sponsored by the National Science Foundation of Research Experience for Undergraduates. 

Parallel Source Transformations via the WHIRL Intermediate Representation

Andrew Gearhart, Anthony Danalis, Magnus Jonsson, and Martin Swany
Department: Computer and Information Sciences

With the advent of low-cost commodity clusters, successful code parallelization techniques are required to obtain significant application speedup. Unfortunately, many scientific applications incur a large amount of overhead due to communication calls between processes. Significant synchronous communication undercuts scalability and efficiency, but often provides the fastest and most straightforward solution to a problem. Because hand-coded optimizations decrease code readability and maintainability, an automatic source optimization system is required. Such a system would detect specific communication patterns within MPI source, transform code into a pipelined format utilizing truly asynchronous communication ("prepushing"), and  thus decrease overall execution time. In addition, the solution should take into account inherent characteristics of the cluster to target optimizations for maximum effect. Toward this end, a source-to-source transformation module needs to detect and manipulate trends within code, and vary action based upon input parameters from upstream optimizer objects. In this study, one specific transmission scenario was considered for  automatic transformation: that of a loop-nested computation kernel followed by an MPI_SEND call to another process. As will be elaborated upon in detail, this code situation is problematic for a source optimizer, as an infinite number of code permutations could be used to accomplish the same compute and SEND objective. However, code manipulation is possible, within the confines of specific stipulations. Thanks are extended to the Science and Engineering Scholars program for providing the funding to pursue this project.

High-Speed Videography and Particle Tracking Velocimetry of Electrospinning Jets
Kristie Grammatikos
, Matthew Helgeson, Joseph Dietzel, and NormanWagner
Department of Chemical Engineering 

Electrospinning is a fiber production technique that requires the use of electric fields to generate continuous polymer nanofibers. In order to better understand the electrospinning process, various models have been proposed to predict the behavior of Electrospinning jets; yet, little has been done to experimentally validate model assumptions and predicted scaling of jet variables. In this work, we hope to bridge the gap between theoretical predictions and online experimental observations through the use of high speed photography and particle tracking using aqueous polyethylene oxide (PEO) seeded with tracer particles as a model system. Varying concentrations of these solutions were electrospun and the initial 2-3 mm of the resulting liquid jet was recorded at 2000 fps. Results indicate that the radius of the jet increases with applied voltage and decreases with increasing PEO concentration. The velocity profiles followed similar trends such that the velocity increased with voltage and decreasing PEO concentration. Theoretical velocity profiles calculated assuming plug-flow largely corresponded to the experimental data thereby validating model assumptions. When plotted as a function of voltage, the velocimetry data yielded effective extension rates that increase with applied voltage, but at a  decreasing rate with increasing polymer concentration, in agreement with expected trends in extensional rheology of the polymer solution. Research is supported by the National Science Foundation under NSF-NIRT.

The Effect of Annealing Temperature on TiO2 Nanoparticles Photocatalysis

Hailey Guerriero
1, S. Buzby2, S. Ismat Shah1,2
1 Department of Physics and Astronomy, 2 Department of Material Science and Engineering,

Titanium dioxide, TiO2, is an effective and inexpensive photocatalyst for the removal of toxic organic compounds from water. TiO2 is also reusable and simple to produce. The objective of this project is to determine the effect of the annealing temperature on the photocatalytic activity of TiO2 nanoparticles. Studies have shown that a combination of anatase and rutile phases improves the efficiency of TiO2 due to the higher photocatalytic activity of anatase and the smaller band-gap of rutile. The goal is to determine the ratio of the two phases with the highest catalytic activity. There are multiple ways of producing titanium dioxide nanoparticles. A sol-gel method was used to synthesize the TiO2 nanoparticles. This method was selected because it creates amorphous nanoparticles, allowing us to control the crystallinity. Titanium tetrachloride was added drop-wise to ethanol then dried in an oven so that the precursor precipitates and forming amorphous TiO2 powder. The samples were then annealed at temperatures ranging from 300oC to 800oC for one hour. The phase composition was determined by X-ray diffraction (XRD). The photocatalytic activity was measured by the removal of methylene blue from water. A 5 ppm solution of methylene blue with 25 mg of TiO2 was exposed to a 100 watt UV lamp for five hours. Samples were removed at regular intervals and were analyzed by UV-VIS spectroscopy to determine the concentration of methylene blue removed as a function of time. Funding by the University of Delaware Undergraduate Research Program.

Nanocomposite Applications for Photovoltaic Cells

Jeffrey Hanft
1, Yashpal Bandari2, Mary Galvin2 Chengheui Ko2, S. Ismat Shah2,3,
 1Department of Chemical Engineering, 2Department of Material Science and Engineering, 3Department of Physics and Astronomy

The sun is our most abundant source of energy and harnessing just a fraction of its power could free us from the use of greenhouse gas emitting fossil fuels. Current solar cells use the semiconductor, silicon, and manufacturing processes are expensive and energy consuming. Nanostructured titanium dioxide, TiO2, is cheap, abundant and environmentally benign, as well as being photoactive. One application of nano-TiO2 is in an organic/ inorganic hybrid cell. Organic polymers are attractive because they are cheap and soluble, allowing for solution processing. Nano sized titanium dioxide is easily available commercially and easily synthesized via sol-gel methods. The hybrid cell involves a uniform thin film layer of TiO2 in its more photoactive crystal phase, the anatase phase, along with the polymer RC30. Atop this layer a thin film of LiF is evaporated. The titanium dioxide acts as the donor of the positively charged hole, which is identical to an electron, but opposite in charge The LiF layer donates the electron. The RC30 polymer is conductive and is the mode by which current is moved towards the anode/cathode of the cell. The anatase phase transition occurs at approximately 450°C and this transition point is critical to photoactivity, as amorphous TiO2 is not photoactive. Organic polymers degrade at temperatures well below the anatase transition temperature and thus the focus of cell fabrication has been the creation of the homogenous photoactive layer. This study is supported in part by the University of Delaware undergraduate research program.

WebVizOr: A Fault Detection Visualization Tool for Web Applications

Barbara Hazelwood, Holly Esquivel, Sara Sprenkle, Lori Pollock

Department of Computer and Information Sciences

Businesses, governments, and consumers increasingly rely on the stability, security, and usability of web applications. But the scale of such applications can make the verification process both time-consuming and laborious. To reduce the overhead of the testing process and to ensure proper application behavior, testers need automated, cost-effective test strategies to develop, execute, and analyze the success of test cases. We have designed an open-source tool, WebVizOr, which aids in the analysis of test case results. Our tool takes as input the test cases, which are a series of HTTP requests sent to a web application, and the HTML responses generated on executing those test cases. In its simplest usage, WebVizOr provides a means for organizing and viewing the responses. Beyond visualization, WebVizOr harnesses the power of various oracles to automatically analyze and filter the HTML response s to locate symptoms of possible faults. Our poster describes the functionality of our tool, as well as its potential uses in industry and academic research. This work was funded by the CRA-W Distributed Mentor Project.

Alumina Nanofibers Generated Through Anodization

Copeland D. Kell, Anup Pancholi, and Valeria Gabriela Stoleru
Department of Materials Science and Engineering

Aluminum (Al) anodized under optimized parameters generates highly organized porous alumina (Al2O3) membranes.  The membranes form hexagonally patterned pores that vary in size depending upon the electrolyte, anodization time, and the voltage employed in the anodization process.  Through the alteration of these parameters a novel approach to nanofiber growth has been observed.  Nanofibers have many potential applications, attributed to the characteristic strengths of alumina such as toughness, resistance to corrosion, good electrical insulation, and low thermal conductivity.  For example, nanofibers may be imbedded into ceramic and metal composites to create high temperature insulating materials.  Samples of high purity Al (99.999 %), 0.5 mm thick were used as the substrate.  The Al samples were processed through three steps consisting of anodization, etching in a mixture of phosphoric (6 % w/w) and chromic acid (1.8 % w/w) at 60 °C, and a second anodization.  Samples were anodized using one of two electrolyte solutions.  For anodization with phosphoric acid (10 % w/w) electrolyte the applied voltage was varied between 80 – 140 V in increments of  ~ 20 V, with anodization and etching steps of 0.5 hours, 1 hour, or 2 hours.  For anodization with oxalic acid (0.3 M) electrolyte the voltage was varied between 40-80 V in increments of ~ 20 V with anodization steps of 3 hours and etching for 4 hours.  The resulting samples were imaged using scanning electron microscopy (SEM) to observe the size, shape, and density of nanofibers.  The Al2O3 composition was confirmed using energy dispersive analysis of X-ray (EDAX).  From the information obtained through these experiments a theoretical mechanism has been formulated. Supported by NSF EPSCoR Grant No. EPS-0447610.

Microreactor Systems for Portable Power Generation

Ryan Kenaley,
Justin A. Federici, and Dion Vlachos
Department of Chemical Engineering

Recently, there has been an increase in demand for portable power devices in laptops, cell phones, and other electronic devices.  This study focused on the use of small reactors that burn hydrocarbon fuel to generate heat and produce electricity through the Seebeck effect. These reactors have great potential because hydrocarbon fuel, such as propane, is around 40 times more energy dense than lithium ion batteries. The microreactor consists of 3 plates sandwiched together, forming a gap about 5cm long, .7cm wide, and 500 microns deep. A catalyst consisting of porous anodized aluminum foil deposited with platinum is inserted in this gap and is utilized for heterogeneous combustion of different fuel and air mixtures.  The device was shown to be robust, easy to startup, and safe because of radical quenching at the walls inhibiting homogeneous flames.  A portable system was realized using a portable propane cylinder and a venturi mixer that injects atmospheric air into the fuel stream. The reactor was integrated with a BiTe thermoelectric module and the generated power was measured via multimeters.  Temperature contours were measured along the copper insert of the integrated device and it is apparent that lack of thermal uniformity reduces the power output. Funding from the Army Research Laboratories is greatly appreciated.

Chemical Vapor Deposition of Tungsten Chloride

Michael Levandusky,
Brian Willis, and Kendra Beadle
Department of Chemical Engineering

The growing concerns over energy and environmental impacts have stimulated interest in new energy sources.  One proposed energy source is an electrochemical fuel cell called a Direct Methanol Fuel Cell (DMFC).  A catalyst is needed at the cathode to create protons, once such catalyst is WC. Thin films of WC are deposited via chemical vapor deposition in a tube furnace reactor. FEMLAB is used to create a computer model of the reactor. The advantage of using computer models in FEMLAB is that they serve as predictive tools in order to optimize the highest film growth rate and film composition by varying parameters such as temperature, inlet flow rates, and substrate position along the tube furnace. The model will be compared with experimental results to confirm its validity and to improve the FEMLAB model. This project was funded by Summer Engineering Scholars.

Testing the Effect of DTT on the Unfolded Protein Response Mechanism in Saccharomyces cerevisiae

J. Dominic Mancini
, David Raden, and Anne S. Robinson
Department of Chemical Engineering

When the folding capacity of the endoplasmic reticulum is exceeded in S. cerevisiae the unfolded protein response (UPR) pathway is triggered.  The UPR can also be triggered by using dithiothreitol (DTT) to hydrolyze disulfide bonds within the cell.  The cell line BJ5464 (ATCC #208288) was used to monitor the UPR by inserting the UPR element – GFP stress sensor on the cetrimeric plasmid pRS314. When DTT is added to these cells the bulk input of unfolded proteins signals the UPR and green fluorescent protein (GFP) is expressed.  GFP is a protein that fluoresces when illuminated with light at 489 nm and is easily detected using a fluorimeter.  The rate at which the UPR is turned on and off can be measured by testing the fluorescence of BJ5464 + UPRE-GFP cells with respect to time. DTT treatments were varied in concentration from 2mM to 10 mM and in time from 20 minutes to 8 hours. The BJ5464 + UPRE-GFP cells recovered after 4.5 hours of continuous treatment with 5mM DTT.  Cells treated similarly for 20 minutes to an hour recovered 30 – 40 minutes after DTT was removed from the supernatant.  To remove DTT, cells were spun down and re-suspended in fresh media. Further testing of DTT treatment, removal, and subsequent re-treatment to capture the dynamics of the system will lead to a better understanding of how the UPR pathway is regulated. The National Institutes of Health IDeA Networks of Biomedical Research Excellence and the Delaware Biotechnology Institute provided funding for this project.

Complex Systems Models as Tools for Asset Management

Anthony Manzella
and Sue McNeil
Department of Civil and Environmental Engineering 

In an era of constrained budgets, Asset Management, a systematic process to support strategic decisions related to physical assets, has become important to transportation agencies across the country.  At the same time, the emerging field of complex systems has provided important modeling tools for a diverse range of studies.  We hypothesize that a pavement system can be modeled as a complex system, which can be used to examine the effect of agency, politician, and user actions on the response of the system as a means of understanding Asset Management practices.  More specifically, this project examines the effects various agents’ behaviors, different analysis techniques, variability, and random failures have on the condition of a pavement system.  A sample pavement system was modeled in MATLAB code using known agency, politician, and user interactions as well as models drawn from the Highway Economic Requirements System.  We observe that a Benefit-Cost method of project selection generates better system conditions than a Worst-First method.  However, an increased rate of catastrophic failure has a greater effect on the system when a Benefit-Cost analysis is used.  These results suggest that Benefit-Cost analyses are more efficient for project selection, but require a stable pavement system for optimum performance.  This conclusion lends support to the push for transportation agencies to employ Benefit-Cost analyses in their project selection processes.  In addition, the results support the need to account for the impacts of unexpected large scale catastrophes on a pavement system.  This project is funded through the University of Delaware Science and Engineering Scholars Program.

Assembly of Two- and Three-Dimensional Nanostructures Composed of Biological Materials
James Nelson
, Erinc Sahin, and Kristi Kiick
Department of Materials Science & Engineering

The biomolecular assembly of three-dimensional nanostructures has so far been underrepresented in the literature, confined to the assembly of two-dimensional structures composed of peptides, proteins, and nucleic acids. Our goal is the assembly of a modular and precisely ordered three-dimensional nanostructure comprised of both a coiled-coil leucine zipper and peptidyl-nucleic acids, or PNAs, design elements.  Two of the four requisite peptides which will comprise the leucine zippers have been expressed and purified.  This work was supported by a grant from NSF EPSCoR.

Applications of Shear Thickening Fluid-Impregnated Materials

Marielle Alexis Newman, C. Nam, and N. J. Wagner
Department of Chemical Engineering

American soldiers in Iraq face life-threatening dangers everyday. Although they currently wear standard Kevlar® bulletproof vests, these devices are inadequate against shrapnel, needle, and stabbing attacks. As well, current Kevlar armor is too thick, heavy and inflexible to be worn on the body’s extremities, leaving these parts vulnerable to injury. However, materials which have been impregnated with shear thickening fluid (STF), a joint development between the University of Delaware’s Center for Composite Materials and United States Army Research Laboratory, have been shown to be almost completely stab proof, as well as provide ballistic protection using much fewer layers of fabric than would be required in conventional body armor. This project has focused on studying the potential to exploit the shear thickening technology in other applications, specifically parts of the body which are currently unprotected by standard body armor. As well, various types of foams impregnated with STF were studied with the goal of developing a knee pad which would protect the wearer from both malicious attacks as well as impacts from tactical activities. Various impregnation methods for the foams were studied and comparatively tested, mainly through use of the Instron Mini44 compression testing modulus. This experimentation has clearly indicated that foams impregnated with STF can withstand nearly ten times the load as compared to neat foams or foams impregnated with other materials. Furthermore, it was found that the various methods of impregnation can provide different loading capacities which must be considered for any potential application of this technology. To further develop and test prototype protective materials, research is being performed with the University of Delaware’s Human Performance Laboratory. I would like to thank the Army Research Lab in Aberdeen, Maryland for their very generous support of this project.

Crystallization and Aggregation of Soybean Trypsin Inhibitor at Low Salt Concentration:
A Phase Behavior Study of Protein Salting In

Gina Palladino
, André C. Dumetz, Eric W. Kaler, Abraham M. Lenhoff
Department of Chemical Engineering

 Simple theoretical models in statistical mechanics permit the calculations of the phase diagram of proteins. Those theoretical approaches predict the existence of different phases: Crystals, liquid-liquid phase separations and gels. At high salt concentration, when proteins are salted out, few experimental works have confirmed those views of the phase diagram. However, experimental studies dealing with the phase behavior of protein salting in are almost non-existent. In this work, Soybean Trypsin Inhibitor (STI), a protein that shows a salting in behavior, is characterized. The solubility close to its isoelectric point is measured, and the physical aspect of the aggregates or crystals that form is reported. Low salt concentrations are particularly relevant for the purification and the processing of protein solutions, and the fundamental understanding of protein salting in should find many applications in the development of rational procedures to optimize those processes. Funding for this project was provided by the National Institutes of Health IDeA Networks of Biomedical Research Excellence and the Delaware Biotechnology Institute.

Non-Linear Microrheology of Wormlike Micellar Solutions of Cetylpyridinium Chloride

Thomas Pavia
, Matthew Rosborough, Alex Meyer, and Eric M. Furst
Department of Chemical Engineering

Rheology is the study of the deformation of a fluid under an applied stress.  Typically, rheology is used to study the response of fluid, macroscopically.  With the emerging techniques of microrheology it is possible to study the local response in fluids to stresses caused by the presence of probe particles.  In this study, a solution of cetylpyridinium chloride and sodium salicylate was used.  These solutions are known to form wormlike micelles, and dilute wormlike micelles act like polymer chains that break and reform.  Probe particles were held using laser tweezers, while the surrounding fluid was moved by translating the microscope stage.  The drag force on the probe particles was measured by monitoring the displacement in the optical trap.  Drag experiments were run to investigate whether shear thinning could be measured using microrheology. In addition, different configurations of multiple particles were set up to quantify normal forces on particles using the laser tweezers, which is impossible with single particles.  The results showed some shear thinning but did not show the degree that was expected from bulk rheology.  Other data showed that the configurations of multiple particles aligned as the solution flowed past. The results show that laser tweezers can measure shear thinning.  In addition, there must be a normal force perpendicular to the flow causing the particles to align.  This research was funded by the Science and Engineering Scholars Research.  We also acknowledge funding from the National Science Foundation (CTS-0238589).

Microstructure of Self-Assembled Surfactant Solutions by Rheo-Small Angle Light Scattering

Matthew Reichert
, Florian Nettesheim, Norman J. Wagner
Department of Chemical Engineering

Surfactants can self-assemble into worm-like micelles when in aqueous solutions. At an increased concentration of surfactant, these wormlike micelles can entangle, leading to very viscous solutions. The properties of wormlike micellar solutions can be studied with rheology and also small angle light scattering.  Thus, there is a commercial interest in creating a device with which to accurately measure both light scattering and rheology simultaneously.  Such a device must fit within the dimensions of the rheometer, and be easy to use.  Critical to this setup is the collecting apparatus that records scattering information.  The overall shape of the device is that of a bent pipe.  An adjustable two-lens system at the base sends parallel light up to a mirror positioned at 45 degrees, which then reflects the light onto a lens-pinhole-lens setup.  Parallel light is then projected onto a CCD chip.  These images are saved on a computer, and are analyzed with a Matlab program (to be written).  The device is calibrated using 3 micron standard latex spheres. Another crucial aspect of this device is that it be fully adjustable, both in general location over the scattering beam, as well as within the part itself.  The device was designed to allow for an adjustable pinhole, and a track was constructed to allow for three dimensional motion of the optical train.  Once operational, this device can be used for studying shear-induced structural changes in wormlike micellar solutions, as well as the possible influence of the addition of particles. I would like to thank and acknowledge TA Instruments for their funding and support.

Laser Tweezer Measurements of Normal Stress Differences in Cetylpyridinium Chloride

Matthew Rosborough
, Thomas Pavia, Alex Meyer, and Eric M. Furst
Department of Chemical Engineering

<>Viscoelastic fluids, which exhibit both viscous and elastic behavior during deformation, are known to cause the formation of linear aggregations of dispersed colloidal particles when the fluid is sheared.  Normal stress differences, which are forces perpendicular to the fluid flow, were hypothesized to be the basis of the linear aggregation.  The purpose of this work was to directly test this hypothesis by measuring particle interactions in a flowing viscoelastic fluid.  The materials included 3mM aqueous cetylpyridinium chloride (CpCl) and an equimolar amount of sodium salicylate (NaSal).  CpCl is a surfactant that forms wormlike micelles in solution, and was chosen for its unique viscoelastic behavior.  NaSal was added to electrostatically stabilize the formation of the wormlike micelles.  The methods in which the non-Newtonian fluid dynamics were investigated included drag experiments using laser tweezers combined with video microscopy and particle tracking.  Specifically, a zigzag array of laser-trapped polystyrene (PS) probe particles (diameter 2a=2.799m) were arranged to measure the normal stress differences.  The results showed that the normal force on a particle is linear with respect to the shear rate.  Future work will examine whether the normal stress differences are attributed to the viscoelastic or simply viscous nature of these fluids.  This research was funded through the Howard Hughes Medical Institute.  We also acknowledge support from the National Science Foundation (CTS-0238589).

Characterization of Shear-Thickening Kaolin Suspensions for use in STF Body Armor

Brian Rosen
, C. Nam, Dennis Kalman, and N. J. Wagner
Department of Chemical Engineering          

Modern body armor is bulky, heavy, and restrictive in terms of a soldier’s flexibility and motion. Consequently, most body armor only covers just the torso and head, whereas many injuries are suffered at the extremities such as the arms, legs, and neck. The goal of this research is to investigate the shear-thickening of highly loaded kaolin clay suspensions for use in STF body armor. The flat 500nm Kaolin particles may have the ability to absorb and disperse energy more efficiently than the spherical silica particles used in previous STF formulas. Rheological measurements show that kaolin particles suspended in glycerol (0.62 wt %) continuously shear thickens between shear stresses of 12 and 1000 pascals. Upon forming a composite with 706 Kevlar®, the composite showed a markedly increased stab resistance as well as minimized pullout of the Kevlar fibers. Quasistatic stab tests on 4 layers of Kevlar impregnated with the kaolin STF using an NIJ standard spike show that the sample can handle a load over 200N and prevent the spike from penetrating. The results of this research can aid in the development of a broad range of protective materials for both consumer and military applications.Funded in part by University of Delaware Department of Chemical Engineering, Army Research Laboratory, Aberdeen Proving Grounds, and the Center for Composite Materials at the University of Delaware.

Soft Particle Shear Thickening Fluid

Josh Schein,
Dennis Kalman, and N. J. Wagner
Department of Chemical Engineering 

Research has shown that body armor impregnated with shear thickening fluid (STF) exhibits increased resistance to ballistic and puncture type attacks.  Recently, however, SEM images of impregnated Kevlar have shown damage caused by the particles in the STF to the individual Kevlarâ fibers.  This damage, seen in the form of pitting, has the effect of decreasing the overall strength of the Kevlarâ.  Since a decrease in strength contradicts the goal of creating better body armor, this is not wanted.  The goal of this research is to create a soft particle shear thickening fluid that will strengthen the Kevlar and cause no extra damage to it upon impact.  Soft particles were synthesized following a published synthesis for Poly(methyl methacrylate) (PMMA) in a methanol-water mixture.  Particles of nominally 550 nm and 900 nm were successfully synthesized and characterized.  These dispersions are to be transferred to a non-volatile solvent and their rheology characterized.  As a final step, the soft particle STF will be intercalated into ballistic fabrics and testing using quasistatic needle testing to determine if particle softness affects STF composite performance.  I would like to thank Aberdeen Research Lab and Armor Holdings Inc for funding.

A Homogenization Approach for Electrode Design Optimization

Andrew Seagraves
and R. V. Roy
Department of Mechanical Engineering 

Current fabrication practices for polymer electrolyte membrane (PEM) fuel cell electrodes allow little or no control over the resulting microstructure.  A technique is being developed to fabricate electrodes with bimodal porous networks allowing control of the pore geometry and size distribution.  This dual porosity will include micro-pores for bulk diffusion and nano-pores serving as pathways for reaction to occur.  Reiterated homogenization will be used to study the macro-scale diffusion-reaction characteristics taking into account the nano and micro-scale structural heterogeneities.  A two-scale problem with simple unit cell geometry has been homogenized with the effective properties and leading order solution obtained numerically using an efficient Alternating Direction Implicit (ADI) difference scheme.  ADI will be used to solve the three-scale reiterated problem.  Electrodes possessing the optimum bimodal pore structure will be fabricated after it has been determined through homogenization and numerical optimization.  Funding provided by the University of Delaware.

Catalysis of Propane Ammoxidation Using Synthesized Crystals
of Niobium-Doped Bismuth Molybdates

Josh A. Selekman
and Douglas J. Buttrey
Department of Chemical Engineering

Acrylonitrile, prepared by the ammoxidation of propylene, is a product used in thousands of materials worldwide.  Because billions of kilograms of acrylonitrile are produced per year, there is, as for any major process, a desire for a more cost effective approach.  An alternative method of acrylonitrile preparation is to substitute propane for propylene, which would result saving hundreds of millions of dollars per year.  However, the difficulty of this substitution is the requirement of a new catalyst for propane ammoxidation.  For propylene ammoxidation, a well-developed bismuth molybdate catalyst is used.  The approach to discover a new catalyst for propane ammoxidation begins with using the propylene catalyst as a template and varying its different properties including pH at which synthesis takes place, stoichiometric ratio, calcination temperature and time, and overall composition of the catalyst.  In terms of composition, niobium has shown potential in catalytic research and is added, in small quantities, to the bismuth molybdate parent structures to possibly increase catalytic ability.  High pH syntheses are done with small ratios of niobium including 5%, 10%, and 15% in different parent structures of bismuth-molybdates including the Beta phase and the Gamma phase. Once these niobium-doped bismuth molybdates are synthesized, their structures are determined using X-ray diffraction.  From XRD data, crystal structures are determined and give rise to certain properties potential for catalysis. Specifically, oxygen transport within crystal structure is a key property of good catalysts. Once structure is determined and potential is shown, these doped bismuth molybdates will be tested catalytically in propane ammoxidation.

Large-scale Recovery of Human Adenosine A2a G-Protein Coupled Receptor from High-pressure Homogenization
Joshua L. Stottmann, Michelle A. O’Malley, and Anne S. Robinson
Department of Chemical Engineering            

Recent efforts have focused on expression and purification of G-protein coupled receptors in order to better characterize their detailed structure.  In these studies, the yeast Saccharomyces cerevisiae was used to express milligram amounts per liter of culture of the human adenosine A2a receptor with a green fluorescent protein fusion and a 10-histidine tag for purification.  The bead-vortexing procedure previously used to lyse the yeast cells and extract A2a resulted in high protein yields; however, these samples sometimes contained impurities and the process itself was time-consuming and difficult to scale up. The goal of this research was to develop an alternative, scaleable lysis procedure which makes use of high pressures to rupture yeast cells and recover A2a.  After lysis through an Aviston EmulciFlex® homogenizer, cell membranes were fractionated by ultracentrifugation.  These protein-containing membranes were combined with a surfactant solution which removed and solubilized the protein.  The histidine-tagged A2a was purified from other cellular proteins through the use of immobilized metal affinity chromatography.  Protein concentration throughout the process was monitored by fluorescence spectroscopy, and purity was assessed by SDS-PAGE.  The fluorescence of the purified protein indicated that about 1.25mg A2a per liter of culture was purified, which is comparable to the previous values.  In addition, SDS-PAGE revealed lower levels of impurities than were reported using the previous lysis method.  A 500mL culture was also successfully run through this process to prove that it can be scaled up.  In the future, ligand binding assays will be used to test the activity of this purified protein and to compare it to the activity of prior samples.  Funding for this project was provided by HHMI.

Optimization of Human Neurokinase 2 Receptor Expression in Escherichia coli

Javier Velasquez, Steven Bane, and Anne S. Robinson
Department of Chemical Engineering

G-Protein Coupled Receptors (GPCRs) make up a family of seven helical transmembrane proteins that transmit extracellular signals into the cell via association with heterotrimeric G proteins. As key players in cell signal transduction, GPCRs are involved in diseases such as cancer, HIV infection, and heart disease. These receptors are targeted by approximately 50% of today’s pharmaceuticals. Greater knowledge of their structure would therefore be beneficial to the advancement of drug treatments. However, detailed structure studies require milligram amounts of the protein, and current overexpression systems produce only a low abundance. It was the goal of this project to optimize current E. Coli expression protocols to produce the human Neurokinase 2 receptor (hNK2) in sufficient quantities to allow purification and characterization of the target protein. To this end, the variables of cell line, temperature, and duration were studied as a means of maximizing hNK2 expression. Expression levels were measured by gel electrophoresis and Western Blot assay. The target protein was purified by means of Ni-NTA nickel chelating resin, employing a 6 histidine C terminal tag. At this time, insufficient quantities of hNK2 have been purified to allow further study to take place. Funded in part by HHMI.

Phase Behavior of Amphiphilic Block Copolymers in Water

Brian Walck
, Jennifer O’Donnell, and Eric Kaler
Department of Chemical Engineering

Amphiphilic block copolymers self-assemble in aqueous solutions to form highly tunable aggregate structures.  These aggregates are useful for solubilizing organic compounds and stabilizing emulsion polymerizations, but the self-assembly of these block copolymers is much more complex than that of typical surfactants.  The nature of these structures can be tuned by varying the temperature, pH, and concentration of the block copolymer.  The purpose of this research was to quantitatively investigate how these factors affect the size and microstructure of the block copolymer aggregates.  Poly(acrylic acid)-polystyrene was chosen as the amphiphilic block copolymer for this research. The precursor poly(butyl acrylate)-polystyrene was prepared by a sequential controlled radical polymerization of poly(butyl acrylate) and polystyrene.  A method was then developed for hydrolysis of the poly(butyl acrylate)-polystyrene to poly(acrylic acid)-polystyrene and its subsequent dissolution in aqueous solutions.  Calorimetry and surface tension measurements were used to determine the critical micelle concentration, visual observation was used to observe phase behavior of varying concentrations of copolymer at different temperatures, and quasielectric light scattering and electron microscopy were used to obtain measurements of the size and shape of the aggregates.  The aggregates were found to have formed spherical polydisperse microstructures with diameters of less than 50 nm. Future work will include observing the effect of varying other factors including the pH of the solutions as well as the ratio of the polystyrene block to the poly(acrylic acid) block.  This research is funded by the Science and Engineering Scholars Research Program.

Links: Summer 2006 Undergraduate Research Symposium, Symposium Abstracts from other Colleges and Departments,
Undergraduate Research Summer Enrichment ProgramUnversity of Delaware Undergraduate Research Program, Howard Hughes Undergraduate Program.
Created 1 August 2006. Last up dated 16 August 2006 by Hal White
Copyright 2006, University of Delaware