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REU Past Students

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2019

  • Hayat Abdurahman - Engineering, Community College of Baltimore County

    Hayat AbdurahmanEducational Institution: Community College of Baltimore County
    List of Mentors: Dr. Sharon Weiss & Rabeb Layouni
    Program: NSF REU
    Research Project: Porous Silicon based Optical Sensing in Complex Media: Antifouling Coating
    Poster: NSF REU Hayat Abdurahman Poster.pdf
    Research Abstract: The development of optical biosensors for use in complex media, such as blood or serum, is essential to further advance medical diagnostics especially for point of care applications. However, the majority of studies on emerging biosensor materials, such as porous silicon (PSi), are done in purified solutions. This project investigates a new approach to design a more reliable PSi-based biosensing platform in serum. PSi offers many advantages due to its ease of fabrication, large surface area, and convenient surface chemistry. In order to reduce the non-specific binding of proteins and contaminants from complex media, an antifouling coating consisting of a polyethylene glycol silane (PEG-SL) monolayer was applied to the PSi surface. The antifouling coating helps prevent protein adsorption by creating a hydration layer and exhibiting a steric hindrance effect. Contact angle (CA) measurements for PSi, PEG-SL on PSi, and PEG-SL on oxidized porous silicon (OPSi) confirmed that the surface gained hydrophilicity after the addition of the PEG-SL layer, suggesting an ability to reduce biofouling (, , ). Corrosion tests in PBS buffer () showed that OPSi is a more stable substrate compared to PSi. When exposed to serum, PEG-SL on OPSi exhibited an 80% reduction in non-specific binding compared to uncoated OPSi. This demonstrates that the antifouling capability of the added PEG-SL monolayer improves the specificity of PSi-based biosensors. The next step is to test this surface with a biotin-streptavidin assay in serum to further validate the antifouling layer efficiency.

  • Matthew Castanon - Biochemistry, Kennesaw State University

    Matthew CastanonEducational Institution: Kennesaw State University
    List of Mentors: Dr. Craig Duvall & Ella Hoggenboezem
    Program: NSF REU
    Research Project: Optimizing Gene Silencing Using siRNA-Loaded Porous Silicon Nanoparticles
    Poster: NSF REU Matthew Castanon Poster.pdf
    Research Abstract: The main premise of the project is to measure the optimal loading efficiency of siRNA into porous silicon nanoparticles for the utilizing of siRNA-loaded, Luciferase gene-suppressed PSNPS. In addition, the PSNPs will be coated with PEGDB to disrupt acidic vesicles and trigger the release of siRNA into the cytoplasm once intracellularly. The PSNPs will also have a Calcium Silicate shell allowing the electrostatic linkage between the negative surface charge of the PSNPs, the divalent cationic nature of Calcium, and the negatively charged siRNA molecules. The results from the PSiNP-siRNA gene knockdown assay demonstrate that there does not appear to be significant differences in knockdown between targeted and scrambled siRNA delivered by the porous silicon nanoparticles. Gel electrophoresis of siRNA remaining in the supernatant demonstrates that the groups without salt show the same siRNA content as those with calcium, even though the brightness is dimmer and spread out over a vast area. Interestingly, the lowest content is demonstrated in the samples without PSiNPs, potentially signaling at calcium-siRNA sequestration. From our luciferase assay results, greater luminescence and lower knockdown was shown by siRNA loaded into porous silicon nanocomposites compared to PEG-DB. We theorize that too little porous silicon and too much salt is being utilized. On a nanoscale, porous silicon is encapsulating enough siRNA but the calcium concentration is too high, causing the calcium to more compete with the porous silicon to bind siRNA. Future work will include reevaluation of concentrations used in the protocol to achieve optimal loading.

  • Elyssa Ferguson - Mechanical Engineering, University of Maryland, Baltimore County

    Elyssa FergusonEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Cary Pint & Janna Eaves
    Program: NSF REU
    Research Project: Exploring New Cathode Materials to Enable High Energy Magnesium Batteries
    Poster: NSF REU Elyssa Ferguson Poster.pdf
    Research Abstract: Modern smartphones, electric vehicles, drones, and other evolving technologies demand improvement of Li-ion batteries into more energy-dense power sources. Magnesium (Mg) batteries are a promising alternative because the Mg2+ ion shuttles twice as many electrons as Li+, thereby doubling the theoretical volumetric energy density. Here, we investigate the storage capacity and Mg-ion hosting mechanisms of tungsten diselenide (WSe2) as a cathode material for these cutting-edge battery systems. Using a three-electrode electrochemical setup, we measured a high specific capacity of 120 mAh/g and subsequently characterized the material at 0%, 50%, 75%, and 100% discharge via X-ray diffraction and Raman. The results show that WSe2 stores Mg through a reversible intercalation mechanism, dispelling concerns that the layered material might undergo inefficient chemical conversion reactions, as it is known to experience in lithium- and sodium-ion batteries. This work opens a door to energy-dense multivalent ion batteries that surpass current lithium-ion technologies in cost, safety, and size.

    • Conference Presentation
      E. Ferguson, J. Eaves, and C. Pint, “Exploring New Cathode Materials to Enable High Energy Magnesium Batteries” Council on Undergraduate Research Research Symposium for Undergraduates, Alexandria, VA, October 2019.
  • Alyssa Livingood - Computer and Electrical Engineering, University of Kentucky

    Alyssa Livingood Educational Institution: University of Kentucky
    List of Mentors: Dr. Josh Caldwell & Ryan Nolen
    Program: NSF REU
    Research Project: Non-dispersive Infrared (NDIR) Sensing of CO2 Using CdO Films
    Poster: NSF REU Alyssa Livingood Poster.pdf
    Research Abstract: The potential for realizing portable, light-weight devices reliant on narrowband, mid-infrared light is hindered by the low wall-to-plug efficiencies and large footprints of gas-phase lasers and quantum cascade lasers.  There exists a demand for efficient, cost-effective, narrowband sources that could improve mid-infrared spectroscopy and sensing. Recent work has shown that narrowband thermal emission is feasible by using subwavelength films of n-doped cadmium oxide. These films are highly efficient thermal emitters due to the fact that cadmium oxide is a plasmonic material which supports epsilon-near-zero (ENZ) modes. ENZ modes are excited at the zero crossing of the real part of the permittivity and can couple to free space without any nanostructuring to create ENZ polaritons. Along with supporting ENZ polaritons, cadmium oxide exhibits low optical losses and has a highly tunable plasma frequency throughout the mid-infrared. While these films are a significant step towards practical, tunable narrowband mid-infrared sources, their peak emission occurs at an angle highly off normal, limiting their applicability. To increase the viability of these novel emission sources, it is necessary to achieve high narrowband emission at normal incidence. Here, we have shown that by growing n-doped cadmium oxide films on a patterned sapphire substrate, high emission is achievable at normal incidence. We conducted thermal emission measurements to confirm that our films were accurately tuned to emit at 2500 cm-1. Angle dependent thermal emission measurements were also performed and have shown that the n-doped cadmium oxide films on a patterned substrate emit omnidirectionally. It was also observed that at high angles Fano interference occurred between the ENZ mode and a propagating surface mode. This caused the bandwidth of the thermal emission to become extremely narrowed, reaching Q factors of 14. These results are promising and can guide further optimization of n-doped cadmium oxide films on patterned substrates for narrowband thermal emission. With the tunability and high emissivity at normal incidence, these films could be used for applications such as nondispersive infrared sensing of gas molecules.

  • Catherine Ludolph - Chemical Engineering, University of Texas, Austin

    Catherine LudolphEducational Institution: University of Texas, Austin
    List of Mentors: Dr. Cynthia Reinhart-King & Jenna Mosier
    Program: NSF REU
    Research Project: Alternating confinement in collagen microtracks in vitro influences cancer cell migration
    Poster: NSF REU Catherine Ludolph Poster.pdf
    Research Abstract: Metastasis, or the spread of cancer, accounts for 90% of cancer related deaths. During metastasis, tumor cells migrate away from the primary tumor through a collagen rich environment known as the extracellular matrix (ECM). Previously, it has been shown that cells in confinement move significantly faster than cells that are unconfined. Because cells are able to sense these spatial restrictions as they migrate through the ECM, it is thought that they can be conditioned to more readily navigate more challenging environments such as repeated confinement and employ a “mechanical memory” to inform future migration decisions. To model this environment, collagen microtracks of width alternating between 7 and 15 μm were fabricated by etching a silicon wafer, making polydimethylsiloxane (PDMS) stamps from the wafer, and stamping the PDMS into collagen to mold the microtracks. Highly metastatic MDA-MB-231 breast cancer epithelial cells were seeded into the collagen microtracks and allowed to migrate freely while their positions were tracked for at least 12 hours. The narrow 7 μm width sections fully confined the cells, such that the cells touched all four surrounding walls, while the wide 15 μm sections partially confined the cells, such that the cells touched three or fewer walls. Microtracks of 7 μm and 15 μm uniform width were used as controls. Cells in alternating width tracks reached a higher final velocity than cells in either of the uniform width tracks. However, cells in the alternating width tracks did not travel as far as those in the narrow 7 μm tracks, suggesting that repeated confinement may not induce more efficient migration. Future work will focus on further examining cell behavior in challenging microenvironments to determine how alternating confinement influences cell migration.

  • Inaya Molina - Physics & Spanish, Hendrix College

    Inaya Molina Educational Institution: Hendrix College
    List of Mentors: Dr. Kane Jennings & Josh Passantino
    Program: NSF REU
    Research Project: Polymerization of Aniline by Photosystem I Proteins
    Poster: NSF REU Inaya Molina Poster.pdf
    Research Abstract: Photosynthesis is a process in plants which converts solar energy into chemical energy and has become a basis for biohybrid solar cells. Solar panels today are growing in demand yet their price and the energy waste they create in production are still prominent problems. Photosystem I (PSI) is a protein vital for photosynthesis in oxidizing and reducing native redox species to produce NADPH. The two sites responsible for oxidation and reduction are the P700 and FB sites, respectively. Polyaniline (pAni) is a conductive polymer that has been shown to work well in biohybrid solar cells. If PSI can electropolymerize aniline monomer to form polyaniline, a robust protein-polymer conjugate can be produced that may result in direct electrical wiring of the key active site of the protein.  pAni is formed though an oxidative polymerization, which we hypothesize is possible with PSI. By combining aniline and PSI in solution, we hypothesize that aniline can polymerize at the P700 site, forming pAni attached to the protein. We show through cyclic voltammetry and FTIR that the P700 site of PSI does polymerize pAni in solution. pAni formation was investigated at multiple pH’s with PSI to find the optimal pH for pAni growth without damaging the protein. pH 4 was determined to be the best pH for pAni growth with PSI. Our results suggest that we have produced the non-conductive leucoemeraldine form of polyaniline that can be doped in order to create more conductive forms.

  • Nicholas Riley - Mechanical Engineering Systems, Arizona State University

    Nicholas RileyEducational Institution: Arizona State University
    List of Mentors: Dr. Jason Valentine & Hanyu Zheng
    Program: NSF REU
    Research Project: Fabrication of Multilayered Metasurfaces
    Poster: NSF REU Nicholas Riley Poster.pdf
    Research Abstract: Metasurfaces are thin sheets of metamaterials, which are nanostructured surfaces that can manipulate the wave front of light. By engineering the nanostructures of a material, we can change the way that material interacts with light. Multiwavelength operation is achieved by using multiple layers of metasurfaces. Creating a multilayered metasurfaces involves fabricating separate layers with alignment marks, then using a transfer system to align and bond the layers. Previous systems utilized a transfer stage for alignment and PDMS for bonding. Our objective is to achieve a higher level of horizontal and vertical alignment of metasurfaces layers by developing more effective transfer methods to decrease fabrication errors and create better metasurfaces doublets. This project developed a transfer stage with precise translation, rotation, and tilt capabilities that allowed for testing of alignment methods. Cross and grating alignment marks were fabricated for horizontal alignment. A Fabry-Pérot cavity was used to characterize relative distance between layers as a function of beam intensity. In future work, we will explore the effectiveness of these methods on one sample, as well as optimizing the stability of the system.

  • Pamela Joy Tabaquin - Chemistry, Queensborough Community College

    Pamela Joy TabaquinEducational Institution: Queensborough Community College
    List of Mentors: Dr. David Cliffel & Chris Stachurski & Kody Wolfe
    Program: NSF REU
    Research Project: Entrapment of Photosystem I within a Polyaniline Matrix on Carbon Paper for Photocurrent Generation
    Poster: NSF REU Pamela Joy Tabaquin Poster.pdf
    Research Abstract: Photosystem I (PSI) is a membrane bound protein complex found in plants which helps drive photosynthesis. Due to its abundance in nature and high quantum efficiency, PSI is a prime candidate for use in biohybrid solar cells. To date, several PSI bioelectrodes have been successfully fabricated using a variety of different electrode materials and host matrices, such as conductive polymers like polyaniline (pAni). pAni has been polymerized on metallic electrodes in the past; however, carbon paper (CP) substrates have also been utilized for pAni polymerization. Electrochemically polymerizing aniline in the presence of PSI onto low cost, high surface area CP, enabled the production of PSI-pAni-CP electrodes which showed enhanced photocurrent generation. The hydrophobic CP was first pretreated then characterized using contact angle and cyclic voltammetry. Using the pretreated carbon electrodes, PSI-containing pAni composites were electrochemically produced and tested in photoelectrochemical cells. It was found that devices prepared in the presence of PSI enhanced the observed photocurrent by a factor of 2 over non-PSI containing devices. By investigating different mediator systems or optimizing deposition conditions, photocurrent generation can be further improved using carbon paper-based biohybrid electrodes.

  • Ellis Thompson - Physics, Vassar College

    Ellis ThompsonEducational Institution: Vassar College
    List of Mentors: Dr. Richard Haglund & Nathan Spear & Samuel White
    Program: NSF REU
    Research Project: Growth of VO2 Single Crystals
    Poster: NSF REU Ellis Thompson Poster.pdf
    Research Abstract: The phase-changing materials Vanadium dioxide (VO2) exhibits a metal-insulator transition coupled to a crystallographic transition (monoclinic to rutile) at ~68ºC, which can be harnessed in thermal, electrical, and optical devices. Large area, low-aspect-ratio VO2 microcrystals exhibit a single-domain, single-phase transition, and thus also serve as useful tools for investigations of the metal-insulator transition itself. VO2 nanowires are known to assume different morphologies based on the lattice structure and thermal expansion properties of the substrate used. However, larger single-domain and single-phase crystals are more difficult to grow, so they have not been extensively studies. Here we show how ~20-200 micron-sized VO2 crystals grown through vapor transport on different cuts of sapphire (Al2O3) and YSZ present unique morphologies and behavior. Images of the crystals show evidence of preferred orientations depending on the cut of the substrate. In addition, Raman spectroscopy indicates aluminum doping of crystals grown on sapphire and the formation of a YVO4 layer on YSZ substrates during growth. These results show that in addition to strain due to lattice mismatch, chemical reactions at the VO2-substrate interface play a more significant role in microcrystal growth than previous studies suggest. Our conclusions also shed light on the physics of crystal growth in the context of phase-change materials. Understanding how nanoscale properties of substrates affects VO2 crystals at the micro-scale will help facilitate future optical experiments and lead to novel technological applications.

  • Christina Trexler - Chemical Engineering & Math, University of Arkansas, Fayetteville

    Christina TrexlerEducational Institution: University of Arkansas, Fayetteville
    List of Mentors: Dr. Piran Kidambi & Nicole Moehring
    Program: NSF REU
    Research Project: Synthesis and Clean Transfer of Atomically Thin Materials
    Poster: NSF REU Christina Trexler Poster.pdf
    Research Abstract: When using a membrane to separate materials, the efficiency of the separation is limited by how quickly molecules pass through the membrane and by how selective the membrane is. Single atom thick 2D materials, such as graphene, hexagonal boron-nitride, and others, present new horizons for the development of novel separation processes. While pristine 2D materials realize the thinnest possible physical barrier for membrane applications, enabling ultra-high permeance, precise perforations in the material lattice can offer strict selectivity. The viability for such nanoporous atomically thin membranes (NATMs) depends on the advancement of synthesis and transfer techniques. Graphene--offering great mechanical strength, flexibility, and inherent impermeability--has been frequently synthesized using the process of chemical vapor deposition (CVD) and subsequently transferred using polymethyl methacrylate (PMMA). When growing monolayer graphene via CVD it is essentially important to create a continuous film while minimizing defects and multilayer growth. Furthermore, the large polymer particle residue generated by PMMA during the graphene transfer process is a fundamental issue that can lead to a myriad of issues during practical applications. Herein, we propose a two-step method of CVD growth in order to achieve a continuous graphene layer with minimal defects and a method of short-term liquid copper annealing that will minimize the appearance of graphene adlayers. We also demonstrate two alternative methods of transferring CVD graphene using polyvinyl alcohol and rosin. In the short term, rosin has demonstrated its superiority to PMMA for the defect free, clean transfer of graphene, whereas polyvinyl alcohol shows promise in integration with roll-to-roll graphene production. These methods also provide helpful information for the controlled growth and clean transfer of uniform monolayers of other 2D materials such as h-BN.

  • Quinton Victor - Mechanical Engineering, University of Miami

    Quinton VictorEducational Institution: University of Miami
    List of Mentors: Dr. Rizia Bardhan & Xiaona Wen
    Program: NSF REU
    Research Project: Portable Reusable Accurate Diagnostics with nanoAntennas (PRADA) for Multiplexed Biomarker Screening
    Poster: NSF REU Quinton Victor Poster.pdf
    Research Abstract: Precise detection of specific biomarkers in human fluids is compulsory for disease diagnosis, risk stratification, and treatment planning.  In this work we introduce an innovative biodiagnostic sensor to circumvent the limitations of those commercially available. PRADA: portable reusable accurate diagnostics with nanoantennas, enables multiplexed biomarker detection in small volumes (~50 µL) when performed in a microfluidic platform.  In this PRADA platform, magnetic microbeads capture cardiac troponin I (cTnI), a well-accepted biomarker of cardiac disorders, and neuropeptide Y (NPY), a biomarker of anxiety and stress. Gold nanostar “antennas” labeled with peptide recognition elements and Raman reporters detect the biomarkers via surface-enhanced Raman spectroscopy (SERS) in both buffer and de-identified human serum samples. The narrow characteristic peaks of SERS leveraged with the nanostar/peptide conjugates enabled multiplexed detection in both buffer and human serum with high sensitivity and specificity, with a limit of detection of 30 pg/mL of cTnI. Moreover, the magnetic beads enabled regeneration and reuse of PRADA for over 15 cycles with the same microfluidic device. In the future, PRADA will ultimately enable rapid and inexpensive assessment of multiple biomarkers in clinical samples amenable to resource-limited settings.

  • Carlos Zuna Largo - Mechanical Engineering, New York Institute of Technology

    Carlos Zuna LargoEducational Institution: New York Institute of Technology
    List of Mentors: Dr. Kelsey Hatzell & Nicholas Hortance
    Program: NSF REU
    Research Project: Electrochemical Ammonia Synthesis Using BZCYYb4411 Electrolyte and Ag Electrocatalyst
    Poster: NSF REU Carlos Zuna Largo Poster.pdf
    Research Abstract: Electrochemical ammonia synthesis is a sustainable alternative to the energy-intensive Haber Bosch process used in the commercial production of ammonia. Electrochemical production of ammonia uses a solid electrolyte and operates under ambient pressure and at intermediate temperatures of 300-600°C. This work investigates the electrochemical performance of the perovskite proton conductor [] to produce ammonia electrochemically from  and . Electrolyte pellets are fabricated and sintered at 1600°C for 24hr. Pellets with a relative density of >95% are coated with a silver [Ag] catalyst to produce the finished sample. The setup of this project includes an alumina single chamber reactor in a tube furnace with  gas and water steam. Current density and ionic conductivity values are measured using electrical impedance spectroscopy. Ammonia gas formed in the reaction is collected in sulfuric acid [] and is measured using UV-spectroscopy. Maximum absorption is observed at 655nm to which the highest formation rate is.