UV Polymerization to Fabricate Different Shaped Structures

Armanj Hasanyan, Department of Engineering Science and Mechanics, Virginia TechDaniel Ahmed, Department of Engineering Science and Mechanics, Penn State University

Using nontraditional spherical shaped microstructures for acoustic streaming has a lot of potential benefits in the future of biology and drug delivery. We explore the fabrication and the acoustic streaming of structures with sharp edges, which is relatively unexplored. Using these results, the lab is eventually planning on performing sonoporation with an acoustic transducer.

During my stay, I have been working on the fabrication of these micro scale structures with UV polymerization. Using a specific liquid polymer solution and exposing it to UV radiation, the polymer was able to polymerize within just a few seconds. One of the challenges for this was being able to optimize the quality of these structures by experimenting with the amount of different chemicals to combine and the amount of time to expose the liquid to UV. Looking back at my time at the lab, one of the things that I have learned as a researcher has been about the application of science and engineering for medical purposes. After spending 2 months in the lab, I am also more inclined to go to graduate school in the future.

Germaniumfiberstransmi.ng3.39µminfraredlightforSurgicalandImagingApplica=ons 

AaronFoster,PhysicsDepartment,OklahomaBap=stUniversityIvanA.Temnykh,VenkatramanGopalan,MaterialsResearchLaboratory,PennStateUniversity

•  InfraredwaveguidesareofvitalimportancetolasersurgeryandNear‐fieldScanningOp;calMicroscopy(NSOM).Alowlossfiberwouldallowcustomizedpowerdeliverytothesurgicallasersresul;ngwithincreasedprecisionandmaneuverability.InfraredNSOMimagingcouldusetaperedfiberstoachievesub‐wavelengthresolu;on.CurrentSilicaandmetallicwaveguidescannotfulfillthesedemandsbecauseoftheirpoorefficiencyintheinfraredspectrum.Myfirstprojectwastodesignalow‐losshollowfibercoatedwithGermaniumandZincSelenidefilms,andop;mizedfor3.39µm,thewavelengthofaHelium‐Neonlaser.Concurrentlywiththatproject,Iassistedinthemanufactureoftaperedsolid‐coreGermaniumfibers.

•  Thissummerresearchhasshownmetheinven;onprocess,fromconcep;ontoimplementa;on,forop;caldevices.AsIworkedalongsidematerialscien;stsandengineers,Ihaveseenfirsthandtheadvantagesofcollabora;onandthenecessityofeffec;vecommunica;on.

• 

In the crusts of neutron stars, bare nuclei form a crystal lattice surrounded by a Fermi electron gas. Knowledge of the exact structure of this crystal would assist the search for gravity waves, as it would help to determine the possible size of mountains on neutron stars, which are efficient sources of gravity waves. In this study we calculate the free energy of different crystal structures to determine which would be favorable under the conditions present in a neutron star crust.

Free Energy Calculations for Binary Crystal Structures in the Crusts of Neutron Stars

Teresa Hamill, Department of Physics, University of PennsylvaniaTyler A. Engstrom, Dr. Vincent H. Crespi, Department of Physics, Penn State University

Over the summer, I have been writing and editing code to perform the calculations for binary crystal structures, running the calculations, and analyzing the results. Through this program, I have learned so much about the process of research, in addition to learning math and physics. Through attending group meetings and talking with my adviser and mentor I've learned the importance of dialog in scientific research.

Enzyme-Powered Nanomotors

Joshua I. Rosario Sepúlveda Department of Chemistry, University of Puerto Rico at Cayey

Samudra Sengupta, Dr. Debabrata Patra, Dr. Ayusman Sen Department of Chemistry, Pennsylvania State University

Motion at the micron and nanoscale can be achieved by utilizing chemical energy from the surrounding fuel and converting it into motive work. Due to their great diversity, the use of enzymes would vastly expand the methods available for powering artificial nanomotors. We hypothesize that by imposing a gradient in substrate concentration, enzyme-functionalized CdSe quantum dots (QDs) will chemotax towards areas of higher substrate concentration. Enzyme-powered motion will find applications in cargo delivery at specific locations, pattern formation, roving sensors, and more.

My role in this project is to synthesize QDs made of CdSe cores and ZnS shells. They will be characterized by TEM, UV-Vis and fluorescence spectroscopy. My project also involves synthesizing an organic ligand that acts as a linker, binding enzymes to the QDs. This project aims at assisting in the continuous search for designing new nanomotors.

NISXW Study of Si adsorbed on an Al-Co-Ni QuasicrystalStephanie Y. Su, Department of Physics, Penn State University

Renee D. Diehl, Department of Physics, Penn State University

NISXW (Normal Incidence Standing X-ray Wavefield)

technique is well known and has been demonstrated as a

powerful technique to determine adsorption structures on

periodic crystals. However, it has never been applied to

study of adsorbates on quasicrystal surfaces. In principle,

the information of the location of adsorbed atoms relative

to these standing waves can be obtained. We did

experiments on Si atoms adsorbed on the Al-Co-Ni

quasicrystal to determine their adsorption structures.

Because of its complexity, we used simulations to compare

calculated spectra to the experimental results.

I used jmol and other programs to model the positions of

the Si atoms on top of the Al-Co-Ni quasicrytal. The

analysis also required that I calculate the structure factors

for this complex surface structure, which was used as input

into the simulations. I appreciated the research opportunity

that I had a chance to study structures that are not well

understood yet, and to discover more about their properties

as well as developing my research abilities.

Effects of Sequential Enzyme Colocalization in an Aqueous Two-Phase System:Activity of Alcohol Oxidase and Horseradish Peroxidase

Katelyn A. Cohen, Department of Chemistry, Dickinson CollegeWilliam M. Aumiller Jr., Bradley W. Davis, Dr. Christine D. Keating, Department of Chemistry,

Penn State University

Aqueous two-phase systems (ATPS) havebecome of increasing interest for the ability to mimicthe micro-compartments of organization within thecytoplasm of cells and for the ability to provide a muchsimpler model to study cellular phenomena than thecell itself. Using model systems to understand complexcellular processes can allow scientists to take a“bottom-up” approach and focus on a specific processwithin the cell in a more controlled and consistentenvironment.

The goal of this project was to use an aqueoustwo-phase system to colocalize two sequentialenzymes, alcohol oxidase (AOX) and horseradishperoxidase (HRP), in increasingly smaller phases of anATPS and determine the impact of colocalization uponenzymatic activity. Through the use of confocalmicroscopy, fluorescence spectroscopy, and UV-visspectroscopy, the partitioning of both enzymes in anATPS were successfully determined and preliminaryactivity studies show a six-fold increase in activity ofboth enzymes upon colocalization.

This project has been extremely beneficial tome as a junior in college as it provided me with greatexposure to a wide variety of techniques in researchand has also opened up the option of graduate schoolto me as the next step in my education. It has helpedme to understand the process of research infinitelybetter and also has helped me develop better researchskills and a sense of independence when working inthe lab.

AOX HRP

PEG-rich

phase

dextran-rich

phase

Enzymecolocalization

PZTPiezoelectricFilmsonGlassSubstratesforGen‐XImagingSystemso

MaryBurkey,DepartmentofPhysics,NorthCarolinaStateUniversityDr.RudegerH.T.Wilke,Dr.SusanTrolier‐McKinstry,MaterialsResearchInsMtute,PennStateUniversity

Inordertofurtherman’sunderstandingofthestructureandevolu5onoftheuniverse,thestrengthandresolu5onofspace‐basedtelescopesmustalsoprogress.Gen‐Xx‐raytelescopeproposesaresolu5onof0.1arcesecondscomparedtothecurrent1arcsecondsfromChandra.However,inordertomaintainthathighresolu5on,deformi5esinthefocusingmirrorsinducedbeforeandaDerlaunchwouldhavetobeeliminated.

Deposi5ngaPZTPiezoelectricfilmonthereversesideofthemirrorisapossiblewaytodothis.Overthesummer,myadvisorandIhavegrown2suchfilmson400μmthickglasswafersusingsol‐gelandspuPerdeposi5on.Weusedthesetotesttheplausibilityofusingpiezoelectricfilmsinadap5veop5csanddeterminetheinfluencefunc5onsofthestraincausedbythefilm.Thisprojecthasallowedmetogainmoreexperienceinexperimentalphysics,becometrainedinnumerouspiecesofequipmentandlearnmoreaboutmyselfasaresearcher.IthasalsohelpedmedeterminewhatresearchtopicsIwouldliketostudyinthefuture.

Creating Flexible Colloidal Chains made from Flattened Spheres

Elias K. Pabón Vázquez, Department of Chemistry, University of Puerto Rico at Cayey Laura Mely Ramírez, Dr. Darrell Velegol, Department of Chemical Engineering, The Pennsylvania

State University

Synovial fluid is a lubricant found in joint cavities,

hypothesized to form chain-like structures of globular

proteins. Our research aims to assemble “colloidal

polymers” that serve as a model to study biological

systems such as synovial fluid. Interaction energies are

greatly enhanced when flat regions on spherical particles

bond. Polymer particles can be flattened by settling onto a

flat surface above their glass transition temperature. By

increasing the ionic strength of the solution to decrease

the electrostatic repulsion between the particles, we can

assemble colloidal polymers. In this summer, I am working

on flattening particles, finding the optimal salt

concentrations to obtain colloidal chains, and analyzing the

statistical results of the chain length and molecular weight

distribution.

My principal objective through this experience is to

improve my skills as a research scientist in an excellent

way by attending seminars, solving challenging research

problems, giving oral presentations, using technical

equipment, and learning from the day to day

educational opportunities in the laboratory.

Working on the optical microscope evaluating the formation of chains.

Localization of Energy States in Hydrographene Tyler W. Maunu, School of Physics and Astronomy, University of Minnesota

Alejandro M. Suarez, Jorge O. Sofo, Department of Physics and Materials Research Institute, Penn State University

Graphene is a semimetal that has excellent electrical properties when doped, which makes it an ideal candidate for current research in nano-circuitry. One possible route to creation of circuitry on graphene involves hydrogenation. Perfectly hydrogenated graphene forms an insulator called graphane, and so circuitry could be created with channels of graphene in graphane. Experimentally, pure graphane is very difficult to produce. Hydrogenation of graphene is a process where hydrogen atoms attach randomly to sites of the lattice and do not diffuse. Due to the random nature of attachment, we use percolation models to generate atomic structures of hydrographene (partially hydrogenated graphene) and study the localization of energy states in the system. We also include correlations in the hydrogenation probability of nearest neighbor sites and study its effect on the localization of energy states. The study of the localization of states at the Fermi energy (zero modes) in particular offers some insight into transport measurements of the hydrographene structure.

My work this summer entailed using the Java development environment Eclipse to simulate and analyze populated lattices. I implemented both uncorrelated and correlated models of population in the generation of these lattices. I then analyzed the energy states of the produced populated lattices. This work has helped me to learn how to approach problems in research and solve them independently. This program has helped me to gain an understanding of how computational research is conducted and has stimulated my interest in this field.

Characterization of the epitaxial growth on Bi2Se3 and Bi thin films on ZnSe Luis O. Pomales-Velázquez, Department of Physics Applied to Electronics, University of Puerto Rico at Humacao

Anthony R. Richardella, Nitin Samarth, Department of Physics, Penn State University

Topological insulators are the new state of quantum matter, with the unique property of a conductive spin polarized surface state protected by time-reversal symmetry. Our objective is to compare the physical properties of Bi and Bi2Se3, especially transport behaviour. Both materials have large spin orbit coupling, but only Bi2Se3 has a conducting surface state characteristic of a topological insulator.

My contribution to the project was to help characterize and compare both materials properties. This will allow us to confirm if Bi2Se3 transport properties are due to its surface protected states. This summer research experience has changed me as a researcher and it has changed the way I approach problem solving, not only in research but in my personal life too. Now I’m determined on moving forward to make my work useful to the scientific community. Step by step I will meet my goals.

Low Resistance Ohmic Contacts to p-type GaN Jenifer R. Hajzus, Physics, Rensselaer Polytechnic Institute

Dr. Suzanne E. Mohney, Department of Materials Science and Engineering, Penn State University

Gallium nitride is a wide bandgap semiconductor used in blue and white light emitting diodes, short wavelength laser diodes, optoelectronic devices, and high speed electronic devices. Low resistivity ohmic contacts are needed to increase the efficiency and functionality of these devices. The wide bandgap of GaN makes the creation of low resistance ohmic contacts to p-type GaN by thermionic emission difficult. The creation of ohmic contacts by field emission by heavily doping p-GaN is difficult as well due to the deep acceptor binding energy of Mg in p-GaN. However, a recent technique developed by Georgia Tech allows for a new, higher doping concentration.

In this study, I tested contacts to the newly developed GaN and compared them to contacts to GaN of a lower doping concentration from a previous study. I performed surface preparation on the GaN samples and aided with the metal deposition. I also annealed the samples and used four probes to measure the resistance of contacts separated by different gaps. I determined the effective specific contact resistance by measuring the gap spacings using scanning electron microscopy (SEM) and then finding an appropriate fit of contact resistance versus gap spacing. The reduction in specific contact resistance was found to be less than expected. I also worked on a side project concerning the dependence of nanowire diameter on the growth kinetics of nickel silicides on silicon nanowires. In this project, I aligned nanowires, observed the photolithography process, and measured silicide lengths and nanowire widths using field emission scanning electron microscopy (FESEM). These projects introduced me to various lab equipment and techniques. They allowed me to apply concepts of physics and materials science to actual hands-on problems and develop a better understanding of the research environment.

Tailoring  of  Light  Sca0ering  in  Composite  Microspheres  for  Spectrum-­‐Spli9ng  Solar  Cells    

Carlos  M  Báez  Co-o,  Chemistry  Department,  University  of  Puerto  Rico  at  Cayey    Anthony  Shoji  Hall,  Dr.  Greg  D.  Barber,  Professor  Thomas  E.  Mallouk  

Department  of  Chemistry  and  Materials  Research  InsHtute,  Penn  State  University  

  Because   solar   energy   is   a   ubiquitous   and   low-­‐energy   density   resource,   there   is   a   need   for   low-­‐cost  photovoltaic  systems  that  work  efficiently  under  a  range  of  irradiaHon  concentraHons.  Nanocrystalline  dye-­‐sensiHzed  solar  cells  (DSSCs)  are  low-­‐cost  solar  devices  that  absorb  light  in  the  visible  part  of  the  spectrum  (400  –  650  nm),  but  only  comprise  only  40%  of  the  energy  of  the  solar  spectrum.  In  order  to  improve  the  uHlizaHon  of  light  in  the  red  and  near-­‐infrared  parts  of  the  spectrum,  the  approach  of  this  project  is  design  a  spectrum-­‐spliWng  cell   in  which  near-­‐IR  light  is  concentrated  by  refracHve  opHcs  onto  a  small  area  silicon  cell,  and  visible  light  is  scaXered  by  the  same  opHcal  elements  onto  a  larger  area  DSSC  back  plane.  

  My   task   in   this   project   is   to   synthesize   spherical   mesoporous   SiO2   parHcles   of   controlled   diameter  (1.2-­‐1.3   µm)   and   fill   them  by   vapor   phase   deposiHon  with   TiO2.  Once   the   composite   spheres   are   synthesized   and  characterized,   we   will   cast   films   of   them   in   an   appropriate   polymer   matrix   in   order   to   determine   their   light  transmission  and  scaXering  properHes.    

Avalanche Behavior of Interacting Magnetic Nano-islands David Myers, Physics Department, Covenant College

Andy Balk, Nitin Samarth, Department of Physics, Penn State University

Magnetostatic interactions among neighboring ferromagnetic nanoparticles provide a rich area of theoretical and experimental investigation, especially in frustrated spin ice arrays and spin based logic devices. We used Magneto-optic Kerr effect (MOKE) imaging to observe the collective magnetization behavior of ordered nanomagnet arrays with lattice spacings from 360 nm to 1000 nm. What we observed was a motion and growth resembling domain walls with the smaller lattice spacings, and less spatial correlation with the larger spacings. There was also a tendency for the switching to begin at the edges of the arrays with all the spacings. We concluded that magnetostatic interactions moderate the switching process.

This project was part of a larger ongoing project studying arrays of magnetic nano-islands. My contribution this summer consisted of developing the MOKE setup, performing MOKE imaging, and the initial analysis and interpretation of the data we collected. The goal of this project was to study magnetostatic interactions, which was accomplished. I have also gained new skills in experimental design, data analysis, and data collection techniques along the way, as well as simply experiencing a graduate research environment.