Home Institution: Bethel University
Major/Minor: Biochemistry & Chemistry/Biology & Mathematics
MRSEC Mentor: Samira Azarin
Development of a Polymer Scaffold to Promote Cardiac Regeneration
Myocardial infarction (i.e. heart attack) occurs when blood is occluded to the heart, resulting in
cardiomyocyte death. Because of the lack of regenerative capabilities in the heart, the damaged
myocardium is replaced with non-contractile scar tissue. The aim of our lab is to induce endogenous
regeneration of the myocardium by the delivery of proliferation agents to the infarcted area via a polymer
scaffold. To be used in the heart, the scaffold must be biocompatible, biodegradable, and reflect the
mechanical and electrical properties of the native myocardium. Additionally, the scaffolds must be
fabricated in a controlled and reproducible manner. Our goal is to investigate polymers for different aspects
of cardiac regeneration. The first aspect of this project was to design polymers for identifying proliferation
agents in a neonatal mouse heart. The second aspect is to investigate 3D printing as a method to create
scaffolds and to control properties such as pore size, filament dimensions, and geometry. We found that the
polymer Pluronic F127 can be used to make a gel for studies of neonatal mouse proliferation and that 3D melt
extrusion of polycaprolactone (PCL) results in reproducible scaffolds, whose shape and geometry can be
altered.
Home Institution: Saint Augustine University
Major/Minor: Engineering mathematics
MRSEC Mentor: Cari Dutcher
Controlling the Polymeric-Anisotropic Particle Flocculation Mechanism
Water treatment facilities utilize various purification process to reproduce clean consumable water.
Flocculation is the process in water treatment that aggregates and sediments suspended particulates before
filtering, generally using. This process utilizes a cationic polyacrylamide, poly(1-carbamoylethylene),polymers
that complexes to the surface of anionic particles. Controlling the polymer behavior in flocculation is critical
for many applications including, composite material, paper manufacturing, andincluding composite
materials, paper manufacturing, and water treatment. Flocculation behavior is dependent on many
parameters including, particulate identity, zeta potential, solution pH, ionic strength, and local hydrodynamics
(Sshear ). Here, FfFlocculation performance (final turbidity)turbidity reduction ) was measured as a function of
solution added NaCl ionic strength and polymer charge percent , at a constant pH of 6.6 and ,
hydrodynamic profile, and bentonite concentration of 30 mg/L. The charge percent’spercents usedtested
arewere 1.5%, 10%, 20% and 60%. Increasing ionic strength reduced the optimum polymer dose for all
polymer charge percent tested, due to an increase in initial bentonite aggregate size and reduction in
electrostatic repulsion. Increasing the polymer charge percent initially from, decreased the optimalum
polymer dose., then increased it, possibly due to a change in flocculation mechanism. The charge percent’s
used are 1.5%, 20% and 60%. Atomic Force Microscopy (AFM) was used to visualize the surface structure of the
bentonite aggregates prior to flocculation and to measure the attractive force between the bentonite and
polymer for various surface structures and ionic strengths. The porous, edge-face surface structure resulted in
the strongest polymer-bentonite interaction. This work sheds light on the complexities of polymer flocculation
towards improving reagent polymer dosing and treatment optimization for important applications such as
water purification.
Home Institution: Binghamton University
Major/Minor: Mechanical Engineering/ Materials Chemistry and Mathematics
MRSEC Mentor: David Flannigan
Modeling Pulsed Laser Heating of Multi-Layered Solids
Ultrafast pulsed laser systems have enabled researchers to investigate processes which occur on femtosecond (fs) timescales. One such application is ultrafast electron microscopy (UEM) which relies on fs laser pulses to initiate reversible processes in defined specimen geometries. Photothermal accumulation and dissipation currently limit the frequency at which the reversible processes can be stimulated. A pulsed laser heating model was developed using the finite difference method to solve the heat transfer equation. The heat source, the incident laser beam, being Gaussian in distribution was simulated using the experimentally determined beam diameter and fluence. The absorption of this incident energy into the material was calculated using known optical and thermal properties of the material. Once the heating of the material was simulated, since the classical solution to the heat transfer equation only simulates conduction, a final term using the Stefan-Boltzman law was added to account for thermal radiation. Constant temperature boundary conditions were then added. Once the model was completed, it was calibrated by comparing the simulated temperature rises in a polycrystalline aluminum sample, to the actual temperature changes, calculated using selected area electron diffraction. Finally, the model was used to predict the temperature in ferrimagnetic terbium cobalt films at which all optical magnetic switching occurred. The model was then adapted to several specimen geometries including, wedge, flake, and thin film samples. Looking forward, we intend to extend this model to get depth dependence, which would allow for the determination of the steady state temperature in a certain layer of a multi-layer thin film and possibly for the determination of the practical limitations of all optical switching.
Home Institution: Macalester College
Major/Minor: Physics
MRSEC Mentor: Chris Leighton
Controlling Resistivity in Barium Stannate
Recent research into Lanthanum doped Barium Stannate (BaSnO3), both single crystals and thin
films have shown the semiconductor to have very high carrier mobility, an essential trait for electronic
applications. I will be working with oxygen-vacancy-doped BaSnO3 thin films from beginning to end. After
making films with plasma deposition, I will use x-ray diffraction to evaluate the quality of the film and the
thickness of the films. Once characterized I will pattern the films into Van der Pauw geometry using ion-milling
to create devices ready for electrical transport measurements. The prepared devices will be used in ion gel
gating experiments to control and alter the carrier density in the film. By placing ion gel across the film and
the gates and applying a gating voltage the charge carrier density can be controlled. Ion gel gating has the
ability to induce a charge carrier density exceeding 10^14 cm^-2 in materials. Altering the gating voltage
should produce changes in the carrier density which cause changes in the resistance of the films. Applying a
positive gate voltage reduced the resistance and applying a negative gate voltage increased the resistance.
The resistance differs by two orders of magnitude between a negative gate voltage of 1.5 and a positive
gate voltage of 1.5 and a positive gate voltage of 3. When gate voltages of less than 2.5 were applied the average reversibility was a ratio of
1.07 ± .15.
Home Institution: Indian Insitute of Science
Major/Minor: Chemisty
MRSEC Mentor: Timothy P. Lodge
Polymer chain conformations in ionic liquids
Ionic liquids are salts that are liquid at room temperature. Upon mixing ionic liquids with polymers, materials can be designed that have the structural integrity of polymers and ionic conductivity of ionic liquids. Although polymer-ionic liquid mixtures have been studied for applications, little is known about the nature of polymer - ionic liquid interactions. The solvent quality and nature of interactions between a polymer chain and solvent molecules strongly affect the conformation the chain adopts in solution. A commonly used parameter that quantifies polymer chain conformations is the Flory exponent ‘v’, where the radius of gyration of the polymer coil (Rg) scales with the molecular weight (M) as Rg ∝ Mv. So far, no experiments have determined v directly for any polymer-ionic liquid system. However, a handful number of simulation studies have been done, but they predict contradictory values of v using different simulation techniques, for the polymer poly(ethylene oxide) in the ionic liquid [BMIM][BF4]. Thus, we aim to experimentally determine the Flory exponent, v, for PEO in [BMIM][BF4]. A relatively accessible technique to determine v is by conducting intrinsic viscosity measurements. The Mark-Houwink relation states that the intrinsic viscosity [η] scales with molecular weight (M) as [η] ∝ Ma, where the Mark-Houwink parameter a satisfies a ≈ 3v – 1. Using a parallel plate rheometer, we have determined the intrinsic viscosities for PEO-10 (M = 10 kg/mol) and PEO-20 (M= 20 kg/mol) to be 17.1 mL/g and 23.5 mL/g, respectively. By further measurements of [η] for additional M of PEO, we can determine a, and thus predict the Flory exponent.
Home Institution: Wellesley College
Major/Minor: Chemistry/Mathematics
MRSEC Mentor: Daniel Frisbie
Investigating the magnitude and origins of a voltage drop across the electrode|electrolyte interface in thinfilm
transistors
Electrolyte-gated thin-film transistors (EG-TFT) present an extremely new promising new technology
in the field of printed electronics. They are both highly sensitive and able to operate at extremely low
voltages. Prior optimization of ion gel-gated EG-TFT devices revealed a persistent voltage drop that occurred
across the gold gate electrode|ion gel electrolyte interface, limiting the overall efficiency. Initially, it was
believed that this occurred due to a gold-specific interaction with the ion gel. Subsequent testing was done
by utilizing alternate materials for the gate electrode, including platinum and the organic conductor PEDOT,
in the hopes of both reducing the voltage drop and gaining insight into its origin. The devices were
fabricated by using photolithography instruments in the Minnesota Nano Center to pattern electrodes onto
silicon wafers. An aerosol jet printer was then used to print the semiconductor poly(3-hexylthiophene) and an
electrolytic ion gel onto the electrode/silicon substrate. Characterization of the devices through IV curves
revealed that the voltage drop was not unique to gold electrodes. Instead, those made with platinum
showed nearly identical results to the gold. PEDOT electrode EG-TFT devices did show an improvement in
efficiency, but further study is required to determine the underlying cause of the material-specific variation in
efficiency.
Home Institution: Purdue University
Major/Minor: Chemical Engineering/Management
MRSEC Mentor: Frank Bates
Adhesion Quality Comparison of Ziegler-Natta and Metallocene-Catalyzed Polyolefins
Polyolefins are polymers that are produced by the polymerization of alkenes with the general
formula CnH2n. In our research, we tested the adhesion strength of the laminate between two different
polyolefins: polyethylene (PE) and isotactic polypropylene (iPP). The overall goal of our project was to better
understand what is happening during the adhesion process of PE and iPP to find a model to maximize the
adhesion force between these two polyolefins. For our procedure a hot press was used to melt and form films
of PE and iPP and then used to laminate the two films together. In order to determine the adhesion strength of
the laminate, a solids analyzer rheometer performed a peel test by calculating the force required to delaminate
the two polyolefins. From our results we are able to compare the differences between two catalyst
methods used to produce polyolefins: a traditional method known as Ziegler-Natta and a more recently
developed process which uses a single-site catalyst called metallocene. We predicted that the metallocenecatalyzed
polyolefins would exhibit stronger adhesion than the Ziegler-Natta-catalyzed polyolefins due to
interfacial entanglements of the polymers in the molten state. In our results we found metallocene pairs
exhibited almost three-fold greater adhesion strength than the Ziegler-Natta pairs. Published literature states
that in Ziegler-Natta-catalyzed polyolefins an accumulation of an amorphous polymer at the interface inhibits
some interfacial entanglement. Interfacial differences, such as the crystallization of the metallocene laminate,
can be observed using transmission electron microscopy (TEM) imaging. These are the beginning phases of
research that could one day develop a method for blending these two immiscible polyolefins.
Home Institution: Universidad de Puerto Rico, Humacao Campus
Major/Minor: Industrial Chemistry
MRSEC Mentor: Valerie Pierre
Synthesis of Antibiotic Metal Ions Complexed with Tripodal 6,6 Linear Catecholate
Antibiotic resistance has become a major health threat around the world. In 2013, over two million illnesses and twenty-three thousand deaths were caused by antibiotic resistance. The overused, misused and unnecessary prescription of antibiotics leads to natural mutagenic resistance of the bacteria. The bacterial infection period requires a 10-6 M iron concentration, nevertheless the host exhibits a 10-24 M iron concentration. Therefore, to meet these condition bacteria produce siderophores. Siderophores are small molecular weight organic compounds which have high affinity for metal ions, especially iron. Enterobacteriacea like E. Coli produces two types of siderophores: aerobactin and enterobactin. Enterobactin, which is the one with the most affinity for iron (Fe+3), contains a trilactone backbone that connects three catechols. The trilactone is the structure that can be modified to obtain new analogues, since it is not recognized by the outer membrane receptor for ferric enterobactin (FepA). The three catechols allow metal coordination and are recognized by FepA. Previous research has shown uptake of some enterobactin analogues by the bacteria. Tricatecholamide analogs complexed to metal ions, such as gallium and indium, can function as radiopharmaceuticals showing an increment in the stability of the metal-binding. Also, antibiotic properties of metal ions, such as Fe+3, Ga+3, Cu+2, Zn+2, Sn+2, Co+2 and Ni+2, have been shown in porphyrins. Additionally, tests have shown antibiotic activity against Escherichia Coli from metal ions such as Cu+2, Ni+2 and Fe+3, in thioformin analogues. Inspired by enterobactin structure, we have synthesized a library of tripodal 6,6 linear catecholate metal ions complexes with Fe+3, Ga+3, Al+3, Cu+2, Zn+2, Sn+2, Co+2 and Ni+2.
Home Institution: University of Minnesota-Twin Cities
Major/Minor: Aerospace Engineering & Mechanics and Astrophysics
MRSEC Mentor: Richard James
Identification of New Shape Memory Alloys with Satisfaction of the Cofactor Conditions
Shape memory alloys exhibit many desirable characteristics. The defining characteristic is their
ability to withstand extreme deformation and then regain their original shape with the addition of heat. As a
shape memory alloy undergoes phase transformations, its properties and crystal structures change, but the
entire process is reversible up to a certain number of cycles. How many cycles it can undergo is known as its
fatigue life and is determined by its reversibility. For a material to be considered a shape memory alloy, it must
satisfy certain conditions called the cofactor conditions. If the cofactor conditions are satisfied, the alloy will
have an improved fatigue life compared to other materials. Since there are few materials that have been
proven to be shape memory alloys, we will identify potential new materials that satisfy the cofactor
conditions, and thus, new shape memory alloys. We will use an arc melt furnace to weld the metals together
and physically make the alloy. The alloy will then be placed in a furnace and quenched to give it shape
memory properties. Once the alloy is made, we will perform X-Ray diffraction on it to determine its lattice
parameters, which can be used to determine if the alloy satisfies the cofactor conditions. If it does not, its
metals’ compositions will be adjusted as need be, until the alloy satisfies the cofactor conditions.
Home Institution: The University of Texas-Rio Grande Valley
Major/Minor: Mechanical Engineering
MRSEC Mentor: Bharat Jalan
Carrier Density Control of 2DEGs NTO/STO Heterostructures
Extremely high carrier density (~10^15 cm^-2) has been achieved by NdTiO3/SrTiO3
heterostructures, grown via the hybrid molecular beam epitaxy approach. It has been shown that such
electronic transport behavior can be controlled by intentionally changing the valence states of NdTiO3, by
changing cation stoichiometry of NdTiO3. Preliminary experiments show that NdTiO3 is sensitive to air, and
oxygen atoms can fill in the interstitial sites and oxidize Ti^3+ in NdTiO3, resulting in a metal-to-insulator
transition. This project will focus on rapid thermal annealing (RTA) of NdTiO3/SrTiO3 heterostructures under O2
and forming gas, and characterize structure using High Resolution X-Ray Diffraction (HRXRD) and Atomic
Force Microscopy (AFM). We will also study the effects of RTA on the electronic transport properties using
Physical Properties Measurement System (PPMS). The correlation will be investigated between thermal
treatment, crystal structure and the electronic transport properties.
Home Institution: University of Massachusetts Amherst
Major/Minor: Mechanical Engineering
MRSEC Mentor: Chris Hogan
Flame Synthesis of Aluminum-Doped Zinc Oxide
Transparent conducting oxides are highly functional in electro-optical devices including thin film
solar cells, flat panel displays, LEDs, and sensors. Indium-doped tin oxide is commonly used as an electrode in
many of these applications due to its high conductivity and transparency. The main challenge with
transparent conducting oxides is cost; indium is expensive to harvest, and indium-doped tin oxide films are
typically synthesized on a large scale with magnetron sputtering. The properties of an alternative material,
aluminum-doped zinc oxide, were examined, as well as a more cost-effective synthesis method for creating
transparent conducting oxide films. An aerosol flame reactor was developed to produce aluminum-doped
zinc oxide nanoparticles. Flame synthesis is easily scalable for industrial applications, it can be carried out at
atmospheric pressure, and it produces homogeneous films. X-Ray Diffraction was used to confirm the lattice
structure, material composition, and size of the particles after flame synthesis. A new online instrumentation
technique using a Differential Mobility Analyzer coupled with an Aerosol Particle Mass Analyzer and a
Condensation Particle Counter was used as an alternative to Transmission Electron Microscopy for
characterizing particles. This research determined the effects of various precursor ratios of zinc and aluminum
on the properties of the final nanopowders.
Home Institution: University of Puget Sound
Major/Minor: Physics, Math / Computer Science
MRSEC Mentor: Russell Holmes
Replacing lead in organic-inorganic perovskite for a more sustainable solar cell
Perovskites are crystals of the formula αβX3 where α and β are large and small cations, respectively,
and X is an anion bound to both cations. Organic-inorganic perovskites have an organic α cation, typically
methylammonium (CH3NH3). Since 2006, perovskite photovoltaic cells have experienced an unprecedented
increase from 2.2% to 22.1% power conversion efficiency, now rivaling more established architectures such as
CIGS (cadmium indium gallium diselenide) and CdTe (NREL 2016). Despite their excellent optical absorption
and low rates of non-radiative recombination, perovskites have yet to see widespread commercial adoption
in photovoltaic devices. The presence of lead in the most efficient and well-studied organic-inorganic
perovskite (CH3NH3PbI3) is a major inhibitor of commercial feasibility. To address health and environmental
safety concerns surrounding the manufacture and disposal of devices containing lead, this investigation
attempts to find a less toxic alternative to lead for the β cation. Based on Goldschmidt’s tolerance factor,
density functional theory (DFT) simulations, and similar compounds synthesized in literature, barium was
selected as the β cation replacement candidate. We attempt to synthesize perovskites of the formula
CH3NH3BaI3 with a two-step vapor-assisted solution process and a single-step solution process. Neither
process produced an identifiable perovskite but the solution process yielded unknown and dynamic spectral
features when exposed to air. Further investigation is required to confidently identify the source of the spectral
features. While it is unlikely that the target perovskite was obtained in this study, significant progress was made
in finding and refining synthesis and characterization techniques.
Home Institution: Creighton University
Major/Minor: Physics and Energy Science
MRSEC Mentor: Uwe Kortshagen
Low Intensity UV Treatment of Zinc Oxide Nanocrystal Thin Films
Zinc Oxide nanocrystal thin films show great potential as a cheap, highly conductive, and
transparent semiconductor. A disordered nanocrystal structure allows for both hyper rapid film production
and tunable properties via nanocrystal size. However, hydroxyl electron traps are found on the surface of the
thin film. These electron traps decrease conductivity by trapping the free electrons found in the Zinc Oxide
film. These electrons result from oxygen vacancies in the nanocrystal. Previously, this problem was solved by
covering the film with ~7nm of Aluminum through atomic layer deposition. However, this solution does not
align with the hyper rapid film production scheme. We have seen that films exposed to low intensity UV light
(~365nm) showed a decrease in hydroxyl group signal in FTIR measurements in a glove-box environment. A
localized surface plasmon resonance (LSPR) corresponding to a free carrier density on the order of 1019 cm-3
is seen after only a few seconds of UV exposure. This indicates that electrons are freed as the hydroxyl traps
are removed. If a film is then exposed to air, the hydroxyl group signal shows again in FTIR measurements. We
see, with various UV exposure times, the mechanics of this phenomena. This UV exposure effect is juxtaposed
with how heat effects LSPR to better outline the differences. A hypothesis for this UV exposure mechanics
involving surface restructuring is proposed.
Home Institution: College of Saint Benedict
Major/Minor: Chemistry; Minor: Communication
MRSEC Mentor: Uwe Kortshagen
Absorption of colloidal silicon nanoparticles with sterically hindered ligand surfaces
Silicon nanocrystals have photoluminescent properties that make them useful tools for many
electronic and optical applications. These luminescent properties must be further researched to increase their
efficiency and adaptability. The specific aspect that will be investigated is finding the molar extinction
coefficient of specific silicon nanocrystals with attached ligands. I will achieve this by collecting absorbance
spectra of of colloidal silicon nanoparticles with 1-dodecene on the surface, a long sterically hindered carbon
chain. These nanoparticles are synthesized using a nonthermal plasma reactor, which passivates the silicon
completely with hydrogen. Keeping air-free conditions, the 1-dodecene is attached using a hydrosilylation
reaction. Taking absorbance spectra of these particles will allow for ample data to utilize the Beer-Lambert
law, and the molar extinction coefficient can then be calculated. The coefficient can then converted to
reflect the extinction coefficient and the concentration on the atomic level. Using this calculated coefficient,
it will be possible to calculate the concentration of the particles suspended in solution without having to
estimate concentration by weight. This is useful because often times the weight estimation is difficult due to
solubility/solvent obstacles. This technique will allow for a more precise means of measuring the concentration
of the colloidal silicon nanoparticles, as well as polymers with the silicon nanoparticles embedded inside of
them.
Home Institution:
Major/Minor:
MRSEC Mentor: Jeff Derby
no abstract available
Home Institution: University of Texas Rio Grande Valley
Major/Minor: Biology; Minor: Art
MRSEC Mentor: Theresa Reineke
Cell attachment and proliferation on Cellulose nanocrystal composite nanofibers
Cellulose nanocrystal (CNC) is a kind of nanoparticle that could be obtained easily from cellulose
by acid hydrolysis. Due to its high elastic modulus, large surface area, high aspect ratio, and good
biocompatibility, it is attracting wide research interest. In this work, cellulose nanocrystal with surface tethered
dopamine will be utilized to generate cellulose nanocrystal reinforced composite nanofibers that could also
be functionalized through dopamine based reactions. The combination of cellulose nanocrystals and
biomolecules suggest potential applications to enhance cell attachment and proliferation properties on
nanofibers spun through forcespinning method. Human dermal fibroblasts neonatal (HDFn) cells were cultured
and seeded onto nanofibers to test cell attachment. An MTT-essay and hemocytometer was conducted for a
quantitative cell proliferation analysis. Fluorescence microscopy was conducted using Mito-Tracker Red (MTR)
for mitochondrial and DAPI for nucleus morphology. Both MTT-essay, hemocytometer, and fluorescence
microscopy showed low cell attachment and viability. With the consideration of cellulose nanocrystal
affecting the surface properties of nanofibers. A new nanofiber matrix material was used through different dip
coating cellulose nanocrystal concentrations, in order to test the cellular behavior of fibroblasts cells on
modified nanofibers and unmodified ones.
Home Institution: University of Texas Rio Grande Valley
Major/Minor: Mechanical Engineering
MRSEC Mentor: Marc Hillmyer
Synthesis and characterization of sugar based surfactants
Surfactants have a variety of uses including applications in the petroleum industry, membranes,
biological systems, detergents and formation of nanostructures. These derivatives are amphipathic, meaning
they are composed of both hydrophilic and hydrophobic groups. In this work, surfactants composed of
sugars and longer alkyl chains will be used to study the ability of these derivatives to produce nanostructures
by induced macrophase separation in the system. The synthesis of this type of surfactant derivate was
achieved first by reacting allyl bromide with 1-octene using Grubbs [G2] as a catalyst to produce 1-bromo-2-
nonene. The second step involves the reactions of D-Glucose with 1-bromo-2-nonene using Sn to produce an
unsaturated derivative. In the next step this derivative will be hydrogenated using Pt/C catalyst to achieve the
final surfactant derivative. Characterization of the products is obtained by 1H NMR, 13C NMR, infrared
spectroscopy (IR), and mass spectrometry (MS). The self-assembly properties of this surfactant and the
formation of nanostructures will be studied using thin films.
Home Institution: University of Puerto Rico at Mayagüez
Major/Minor: Chemical Engineering
MRSEC Mentor: Andre Mkhoyan
Utilizing the Transmission Electron Microscope (TEM) beam broadening to identify elements in materials
The TEM beam broadening occurs due to the interaction of the electrons and the atoms of the
specimen. This effect has always been present in TEM analyses and has been a concern for many researchers
in the areas of materials science and engineering. This beam broadening depends on the material’s
composition and structure, the thickness of the specimen and the energy of the electron beam. The TEM
beam broadening was modeled and observed through both nanocrystals and amorphous solids of different
elements to ultimately define a general relationship between the radius of broadening and the atomic
number of the elements. These calculations were conducted by computer simulations, specifically with the
Multislice method. This method simulates how the electron probe propagates through the sample in a number
of slices. With the computational work, the preliminary results showed that with increasing atomic number the
radius of broadening increases; the beam will broaden more in heavier elements. Further simulations with
more elements should be conducted, considering thermal vibrations and the position and energy of the
beam. Hence correlating the beam spreading with the atomic number in order to introduce an alternative
way of identifying elements in materials with the TEM.
Home Institution: New York University
Major/Minor: Chemical Engineering
MRSEC Mentor: Kevin D. Dorfman
Entropic Filter for Recovering Long DNA
Long DNA molecules are crucial for genome technologies such as whole-genome mapping and
cell engineering. However, samples of long DNA are often contaminated by small DNA from shearing and
other small biomolecules that present obstacles in sequencing. Using photolithography and reactive ion
etching, we have fabricated an entropic trap-based-electrophoretic device in glass to filter out precious DNA
molecules longer than a desired length from an impure mixture. After fine-tuning the device by altering the
strength of the electric fields, the design of the channels, and the heights of the well and slit regions in an
entropic trapping configuration, long DNA is trapped in the device at the nanoslit-microchannel interfaces,
while short DNA passes through. In the future, performance of the new filtration method will be quantified by
running the filtered and impure sample through pulsed-field gel electrophoresis (PFGE). Ideally, the sample of
long DNA produced from the device should not have bands smaller than a certain length. The PFGE system is
new for the lab. We have performed numerous PFGE control experiments to determine optimal parameters
and DNA concentration for distinct separation and to understand the system’s limitations. The tunable
entropic filter offers an efficient method for sample preparation of long DNA that can be used in subsequent
genome applications.
Home Institution: University of Puerto Rico at Humacao
Major/Minor: Chemical Engineering
MRSEC Mentor: Eray Aydil
Synthesis Optimization and Characterization of Tin Sulfide (SnS) NanoSheets
Thin nanosheets of tin (II) sulfide (SnS) have substantial applications in electronic devices and
energy storage technology such as lithium ion batteries. In addition, tin (II) sulfide has low toxicity and a
reasonable natural abundance. When tin (II) sulfide is exfoliated into thin nanosheets, it exhibits a wide optical
band gap of 1.3 eV, making it useful as a semiconductor in photovoltaic cells. To synthesize tin (II) sulfide
nanosheets, conventional-hydrothermal syntheses were made using tin (II) chloride and thiourea (sulfide
source) in a Parr reactor, producing Tin (II) sulfide. Synthesized tin (II) sulfide was exfoliated using sonication
and was centrifuged at different speeds to separate the nanosheets from the bulk tin (II) sulfide. The
identification and characterization of the resulting tin (II) sulfide involved the use of the Scanning Electron
Microscope (SEM), Raman Spectroscopy, UV-visible spectrophotometry and X-Ray diffraction. Atomic Force
Microscopy (AFM) was used to detect the exfoliated tin (II) sulfide nanosheets.
Home Institution: New Mexico State University
MRSEC Mentor: Timothy P. Lodge
High modulus and Conductivity Polymer Electrolyte Membranes
Solid polymer electrolyte membranes offer many advantages over traditionally used liquid
electrolytes, such as the capability of storing higher energy densities while addressing hazard concerns
associated with liquid electrolytes. So far, lithium ion batteries have allowed us to store more energy, yielding
smaller, more powerful and reliable devices, but still, fail to reach their full potential due to problems
associated with the use of a liquid electrolyte. Liquid electrolytes allow the unobstructed formation of
dendrites capable of spanning the electrolyte reducing performance and ultimately causing failure of the
batteries. The liquid is composed of volatile and flammable species which raise hazard concerns especially
during short-circuiting of the battery. A solid state electrolyte exhibiting orthogonal mechanical robustness
and high ionic conductivity allows the possibility of achieving higher energy density storage devices without
compromising reliability and safety in rechargeable electronics. We propose using a solid polymer electrolyte
exhibiting simultaneous high modulus, high ionic conductivity achieved via polymerization induced
microphase separation (PIMS) to suppress dendrite formation on the electrolyte. To improve on previous work
is done we proposed the addition of succinonitrile into the PIMS system, which has allowed a remarkable
increase in the orthogonal properties of similar prior systems.
School: White Bear Lake High School
Mentor: Christy Haynes
Using Dystopian Literature to Enhance Student Engagement of Chemistry
It has been suggested that student engagement increases with the use of cross-curricular academic lessons that are designed to relate to students’ interests and are perceived as challenging, yet also match their skill level. Dystopian literature is popular in teen leisure reading and as a natural connection to current teens can be used as a platform for cross-curricular lessons that allows students to relate general chemistry concepts. Lessons developed for the 2015-2016 academic year for general chemistry students integrated dystopian literature to cover key general chemistry concepts. These lessons were intended to promote critical thinking, reading comprehension, and application of chemistry concepts to dystopian literature while providing students an experience that initiated critical thinking of the world in terms of chemistry and connection of their high school academic subjects to each other and to the world around them. Pre- and post-assessments were used to evaluate the effectiveness of this interdisciplinary approach to chemistry. This project focuses on using data from the 2015-2016 academic year to make changes to improve student engagement with this method for the 2016-2017 academic year. In addition, with the assistance of a high school language arts teacher, appropriate level texts are being selected that meet the Minnesota language arts curriculum standards. One of these new texts is a technology dystopia and will be used in conjunction with microfluidics and acid-base chemistry.
School: White Bear Lake High School
Mentor: Jane Wissinger
Polymeric Medical Sutures: An Exploration of Polymers and Green Chemistry
Green chemistry involves the creative design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. There is a need to teach and train future chemists to apply the principles of green chemistry to develop sustainable solutions that address the needs of our society and economy. A lab experiment was further developed that utilizes medical sutures as a platform to explore polymers, intermolecular forces, and the twelve green chemistry principles. In the first part of the experiment students mimic the creation of medical sutures by drawing the polymer polycaprolactone of varying molecular mass into threads. In the second part students test the tie-ability and tensile strength of their sutures while comparing them to actual medical sutures. The students explore green chemistry principle ten, Design for Degradation, as they test the degradability of the polycaprolactone and actual sutures in part three. In part four the students design an experiment to explore green chemistry principle seven, Use of Renewable Feedstocks, as they melt-blend additions of renewable polylactic acid and assess changes to the draw-ability, tie-ability, tensile strength, and degradability of the sutures. In addition to developing the medical suture experiment this project included learning about green chemistry and its applications in the classroom through a course offered by Beyond Benign. The contents from this course will be transferred to a three-day workshop that will be offered to teachers during the summers of 2017 and 2018.
School: Shakopee High School
Mentor: Ben Hackel
Investigating Genetically Modified Foods in a High School Classroom
DNA extraction experiments are common in high school biology classrooms. However once the extraction has been performed students do not get the opportunity to perform laboratory techniques such as PCR or gel electrophoresis due to the lack of resources in the high school classroom. Biotechnology and genetic engineering are concepts covered in the high school classroom. This experiment was developed so students will get the opportunity to learn about genetic engineering through the extraction of DNA from a variety of foods that they consume on a daily basis. After the extraction students are given the opportunity to carry out a PCR reaction to identify if the food they choose contains food products that have been genetically modified. Students will compare the DNA sequences that were amplified by their PCR to the DNA sequence of a plant that does not contain genetically modified genes through the observation of a gel electrophoresis. This experiment is done to show students lab techniques that scientists use on a daily basis in order to analyze DNA. They are also learning how genetically modified foods are made and which foods contain genetically modified genes.
School: Math and Science Academy
Mentor: Ben Hackel
Characterization and Classification of Breast Cancer Cell Lines using PCR
In this lab designed for high school students grades 11-12, students are exposed to the idea of cancer cell classification by the presence or lack thereof of marker protein expression. In particular, the lab investigates the expression of the estrogen receptor, the progesterone receptor and the human epidermal growth factor receptor in three cancer cell lines. The cell lines chosen have known molecular profiles with regard to the expression of the aforementioned protein markers, but are given as “unknowns” to students.
Funded by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013
UMN MRSEC
435 Amundson Hall, 421 Washington Ave. SE, Minneapolis, MN, 55455
P: 612-626-0713 | F: 612-626-7805