# REU Research Projects

Projects include experimental, computational, and theoretical work in a vareity of areas within or related to materials physics. Completion of a first-year physics or chemistry course sequence is a prerequisite for all projects. Additional prerequisites are noted in the project descriptions.

**Nanoscale devices** (Prof. Paola Barbara) Prof. Barbara’s research group studies transport properties of devices made with atomically thin materials. Current research projects mainly involve molybdenum disulphide, graphene, and other two-dimensional materials, which are of interest both for their basic properties (such as superconductivity) and for applications (such as chemical sensors, detectors of THz radiation, photovoltaic cells and sources of electromagnetic radiation). Students learn how to grow these materials via chemical vapor deposition and characterize their optical properties via Raman spectroscopy. They will also fabricate devices and learn how to test their electrical transport properties. Specific projects will be defined later in the spring and designed to complement ongoing research.

**Structure of soft matter** (Prof. Daniel Blair) The Blair group investigates the structure and function of soft and biological matter using a variety of tools and approaches. Systems of interest include colloidal glasses and gels, unsteady microfluidic flows in non-Newtonian fluids, non-linear rheology of biological polymers, and diffusion in model networks. The primary tools for this work are three dimensional laser scanning confocal microscopy, advanced image processing, bulk rheology, opto- and micro- rheology and laser light scattering. Students in the lab use high-resolution microscopy techniques to acquire time-resolved three-dimensional image data which is then processed using advanced image processing software developed for MATLAB and IDL. A summer REU student will contribute to on-going efforts to measure the microscopic profile of deformed bio-polymer matrices. The goal is to understand the microscopic origins of the non-linear rheology of these materials. By directly imaging a fluorescently labeled network of polymers during a macroscopically applied shear strain, the student will measure how the network deforms locally. This will reveal the length scale that the local shear becomes non-affine, a critical feature of current theories developed to understand biological polymers.

**Soft matter in construction: models and simulations of soft solids** (Prof. Emanuela Del Gado) The Del Gado group uses statistical mechanics and computational physics to investigate the structure, dynamics and emerging mechanics in soft solids. The materials of interest range from colloidal gels to jammed dense suspensions and tissues, to self-assembled nanocomposite interfaces, to the sticky gels formed during cement hydration and responsible for cement strength. The focus is in unraveling how nano-scale structure and effective interactions may interplay with deformation or other non-equilibrium conditions to change the material properties. The aim is devising new paradigms for material design, to obtain specific unusual rheological behavior or more sustainable formulations of smart compounds. Motivated by the need to reduce greenhouse gas emissions associated to cement production, the work on cement gels aims at a first-principles understanding of cement properties, a prerequisite to controlling processing and formulating alternatives. Student will perform computer simulations of model gels, jammed emulsions or nanoparticle adsorption at surfaces or interfaces, and use novel analytical tools to investigate spatial and temporal complexity. Project ideas this year will include theory of active matter, nanoparticles induced by phase separation of complex polymer mixtures during extrusion, the polymer physics that underlies the process of protein production (“from the nucleus to the ribosome and back”), and the non-Newtonian fluid mechanics of Additive Manufacturing (with applications for “bioprinting”). Preference will be given to students with simulations/modeling skills and with good grades in advanced courses such as statistical mechanics and mathematical methods.

**Simulations of spatiotemporal dynamics ** (Prof. David Egolf) The Egolf group employs large-scale computation and theory to study a variety of systems driven far-from-equilibrium. Typically, the systems investigated exhibit complicated spatiotemporal dynamics, and, in particular, spatiotemporal chaos. The group has recently studied the behavior of fluid systems, granular systems, cardiac tissue, and neural tissue, as well as simpler model systems. Students in this group will learn a wide variety of scientific techniques from statistical physics, nonlinear dynamics, mathematical modeling, and parallel computing. Preference will be given to students who can program in C or C++.

**Quantum computation with ion traps ** (Prof. Jim Freericks) The Freericks group is part of a National Science Foundation sponsored project on helping develop and benchmark current generations of quantum computers. Experiments take place in John Bollinger’s lab at NIST, Boulder, Colorado and in Wes Campbell’s lab at UCLA, with the theory work being done at Georgetown. The group is also involved in similar projects with the Department of Energy. Students will learn about quantum dynamics, ion-trap physics, and computation in a project that focuses on the theoretical aspects of the research. Recent projects include developing a new quantum computing algorithm to simulate fermionic Green’s functions and determining how to simulate driven dissipative quantum systems. Completion of at least one course in quantum mechanics is a requirement for this project. Preference will be given to students who also know at least one high-level programming language suitable for numerical work like FORTRAN, C, C++, python, or Matlab (Matlab or python preferred). A previous REU student on this project was named a finalist in the 2012 LeRoy Apker Award of the American Physical Society, awarded to the top undergraduate researchers in all fields of physics in the US. That student was a co-author on a *Nature* paper, a *Physical Review Letter* paper, and a *Physical Review A* article. Since 2013, nine students worked on this project, with eight publiations completed in a variety of different journals.

**Computational studies of 2D materials ** (Prof. Amy Liu) This research group uses computational methods to understand and predict structural, electronic, and vibrational properties of materials, including superconductors, clusters, and nanostructures. One area of interest is in the properties of layered materials that can be exfoliated into atomically thin samples, similar to graphene. The electronic and optical properties of molybdenum disulfide, for example, have been shown to change dramatically as the number of layers is reduced. In the 2D limit, these materials tend to be very sensitive to the environment and the choice of substrate. An REU student might perform simulations to determine how structural and electronic properties of the 2D material varies with the substrate or the type of defects present. The goal is to understand the physics behind these effects and to understand how to optimize these materials for nanoscale devices. Preference will be given to students who have completed a sophomore-level modern physics course.

**Nanostructured materials** (Prof. Kai Liu) Prof. Kai Liu’s research focuses on synthesis and experimental investigation of nanostructured materials, particularly in nanomagnetism and spintronics, which have potentially important technological applications in magnetic recording, low dissipation information storage and nanoelectronics. Current research topics include: 1) Magneto-ionic materials, whose properties may be manipulated by the application of an electric field through controlled motion of ions. These materials are promising towards energy-efficient nanoelectronics and neuromorphics. This project is part of a newly funded major research center by the Semiconductor Research Corporation (SRC) & National Institute of Standards and Technology (NIST), named Center for Spintronic Materials in Advanced Information Technologies (SMART); 2). Low density metallic foams that are extremely light-weight, with enormous surface areas while maintaining mechanical stability. Such foams are being studied for hydrogen storage, filtering, catalysts, photovoltaics, etc. Student(s) working on the project will be involved with all aspects of the research, including sample synthesis, characterization, data analysis, manuscript preparation and research presentation.

**Theory and simulation of soft matter** (Prof. Peter Olmsted) Professor Olmsted studies a wide range of systems, including liquid crystals, surfactant solutions, membranes, polymer gels and networks, polymer melts and blends. He has strong interests in biological problems and materials, including proteins, membranes, and cell biophysics (the figure shows a predicted free energy landscape for lipid bilayers). General themes are (1) the role of complex microstructure and fluctuations on equilibrium phase behavior and kinetics, and (2) strongly non-equilibrium effects, such as the effect of shear flow on the rich degrees of freedom in complex fluids. Theoretical tools for Professor Olmsted’s research include statistical mechanics, hydrodynamics, and computer modeling. Students with programming skills will be able to write programs to perform calculations of increasing complexity; alternatively, Mathematica or MatLab or more sophisticated molecular dynamics packages may be used for some problems. Some projects will be appropriate for students with very strong mathematical skills in linear algebra, differential equations, and vector calculus/differential geometry. Project ideas this year will include the mechanics and dynamics of helical and straight fibrils, phase transitions and dynamics in lipid bilayers, nanoparticles induced by phase separation of complex polymer mixtures, the physics that underlies the process of protein production (“from the nucleus to the ribosome and back”), and the non-Newtonian fluid mechanics of Additive Manufacturing. Preference will be given to students with computation and/or modeling skills, and good grades in advanced courses such as quantum mechanics, Lagrangian mechanics, mathematical methods, and statistical mechanics.

**Nano and micro technology ** (Prof. Mak Paranjape) The Paranjape group works on the design, fabrication, and characterization of biochemical and biomedical sensors, microfluidic devices, and polymers for drug delivery and tissue scaffolding applications. Students are trained in general laboratory safety and cleanroom etiquette, followed by training on state-of-the-art processing equipment such as mask aligners for photolithography, reactive ion etcher for dry plasma surface treatments, magnetron sputterer and electron beam evaporator for metal deposition, furnaces for carbon nanotube and oxide growth, and scanning electron microscopy for image capture and nanolithography direct-write applications. Examples of some of the past summer projects include: i) silk and polymer electrodeposited nanoparticles for drug delivery, ii) biodegradable polymer nanofibers for tissue scaffolding, iii) conducting sub-micron polymer nanofibers for mimicking nerve myelination, iv) a nanofiber piezoelectric energy harvesting device, v) nebulized polymer nanoparticles for drug delivery, and vi) investigating 2D materials (MoS2 and MoTe2) in FET transistor configurations for sensing applications.

**Cellular biophysics and biomechanics ** (Prof. Jeff Urbach) The Urbach group investigates complex dynamical systems including biopolymer networks and motile cells. They employ tools from statistical physics and nonlinear dynamics, together with advanced imaging techniques, image processing, and computer simulations, to understand how cells move and interact with their surroundings. Current projects involve forces and rigidity sensing in different cell types, the fluid dynamics of the undulating flagella of the parasite Giardia, and the mechanical properties of fibrous collagen networks. Students in the group typically learn to use high-resolution microscopy, analysis software, and a variety of sample preparation and cell culture techniques to quantify biophysical dynamics in cells and the mechanical properties of biomaterials.

**Synthesis and characterization of multicomponent nanoparticles ** (Prof. Ed Van Keuren) The main research in the Van Keuren group is the study of organic nanoparticles and involves both investigations of their formation in solution and their use in novel applications. A variety of optical methods are used to characterize the nucleation and growth of the particles. Applications include development of polymer blend nanoparticles, nanoparticle drug formulations and charge transfer nanocrystals for organic electronics. This project would be well suited to a student with interest and background in optics and/or chemistry, and does not require advanced coursework in physics. One additional project involves the application of high speed imaging to study mixing processes during the self-assembly of nanoparticles. This project would be ideal for a student with an interest in electronics and image processing.