Physics Summer Research Project Titles 2015/16

Physics Summer Research Project Titles 2015/16

Soft Matter Physics

1. All cellulose composites: woodn’t that be wonderful.

Dr. Mike Ries

Cellulose is the world’s most abundant naturally occurring organic polymer. It is an almost inexhaustible source of raw material for the ever increasing demand for biocompatible and renewable, environmentally friendly products. Cellulose is a polysaccharide forming a linear chain of linked glucose units and can be found in the cell walls of plants. The modulus of a cellulose crystal is 150 GPa (steel is 200 GPa) and yet is 1/5 the density of steel. A composite traditionally consists of at least two components, a matrix and a dispersed reinforcing phase, for example carbon fibre reinforced polymers. These materials are expensive to produce but give incredible strength to weight ratios and are used in, amongst others, the aerospace and automotive industry, such as a Boeing 787 or a BMW i3. Over many years research at Leeds has, in parallel with commercial development, led to the novel idea of using a process called ‘hot compaction’ to manufacture single polymer composites. In this process highly oriented polymer fibres are heated so that the surface of each individual fibre is ‘selectively’ melted while retaining the core. Upon cooling, this skin recrystallises to form the matrix of a self-reinforced fibre composite. Samsonite pioneered this, producing a new range of lightweight, impact resistant luggage. Now we want to make all cellulose composites using ionic liquids and in this project you will examine the effects an ionic liquid has on cellulose fibres and materials via a wide range of experimental techniques to quantify and understand the physics of cellulose dissolution and recrystallisation.

1. Ionic Liquids: Designer solvents without the designer price tag.

Dr. Mike Ries

Ionic liquids (ILs) are salts with low melting points, below 100 °C at atmospheric pressure, and so at ambient conditions are liquids comprised entirely of ions. Typically an IL consists of an organic cation and a smaller inorganic anion. Unlike conventional molecular liquids they have negligible vapour pressure, non-flammability, high ionic conductivity, and are thermally and electrically stable. Their low volatility, ease of handling and high dissolving power for a variety of inorganic and organic materials means that they are being utilized in the green industrial sector to replace conventional volatile organic solvents. But the lack of a fundamental understanding in the structure-property relationships in ILs is delaying their large scale industrial application. This project will use NMR to investigate the microscopic dynamics of ionic liquids and relate it to their macroscopic properties.

1. Solving solvation: the how and why of dissolving carbohydrates.

Dr. Mike Ries

Cellulose is the world’s most abundant naturally occurring organic polymer. Each year the amount of cellulose produced by Nature outweighs, by factors of thousands, all the combined man-made oil based polymers. It is an almost inexhaustible source of raw material for the ever-increasing need for biocompatible, biodegradable, environmentally friendly products and shows great promise for replacing conventional petroleum-based plastics. Using polysaccharides, such as the carbohydrate cellulose, brings valuable advantages: use of the largest “chemical reactor” Nature itself; decrease of fossil oil dependence; and reduction of CO2 emissions. This project will examine how an ionic liquid dissolves carbohydrates, the first step in processing them, using nuclear magnetic resonance. You will discover how you can determine the microscopic structure and dynamics of these solutions and how to connect this microscopic world to the macroscopic one.

4. The long tail of ionic liquids: ion architecture.

Dr. Mike Ries

Ionic liquids (ILs) are salts with low melting points, below the boiling point of water at atmospheric pressure, and therefore at ambient temperatures are molten liquids comprised entirely of ions. Typically ILs consist of an organic cation and a smaller inorganic anion. They represent an emerging class of versatile materials that are gaining a rapid increase in interest from both industry and academia. Their low volatility, ease of handling and high dissolving power for a variety of inorganic and organic materials means that they are being utilized in the green chemistry sector to replace conventional volatile organic solvents. ILs can in principle be tailored to a specific application due to an almost unlimited number of potential cation and anion combinations. Typically in the design of new ILs with specified required characteristics a trial and error approach is adopted. What is needed in this respect is therefore a better understanding of how the molecular architecture is related to the macroscopic properties. This project will use NMR to investigate the molecular dynamics of ionic liquids and relate it to the architecture; in particular you will examine the effect of adding a tail to the cation and / or anion.

1. Developing an automated system for fibre orientation measurement.

Dr. Peter Hine

This is a purely computer based project, which will require knowledge of C++

1. Quantum dots based photonic devices

Dr. Mamatha Nagaraj

1. Understanding chirality in non-chiral liquid crystals

Dr. Mamatha Nagaraj

1. Design and application of a laser-based system for the characterisation of gelation, phase behaviour and physical ageing in soft matter systems.

Dr. Johan Mattsson and Dr. Pete Hine

1. Fast but practical LCD: A novel way to bake a pi cell.

Prof. Cliff Jones

The LCD used in your TV set is limited in speed for more complex applications such as glasses-free 3D displays, frame-sequential colour (instead of colour filters) and high frame rates for gaming applications. One solution is to use what is called a pi-cell. Unfortunately, this type of device has never succeeded in practice due to the complex manufacturing issues and unreliability. Recently, a new type of liquid crystal phase has been discovered – the twist-bend nematic phase. This occurs in materials that have very unusual elastic properties. At the moment, no-one has thought of looking at these materials in devices. In this project we will try to solve the problems of the pi-cell using this exciting class of material. You will learn a lot about physical properties of soft matter materials, building devices in the clean-room, and how to conduct research.

1. Ultra-thin molecular films. Is there a liquid crystal equivalent to graphene?

Prof. Cliff Jones

The two most common forms of liquid crystals are the nematics found in your TV display, and the smectics, found in switchable privacy screens and . Smectics are like two dimensional liquid crystals, forming layer structures. These layers can form free-standing films, similar to how you form soap bubbles. Some of these films have been 2 – 3 layers thick. However, they are short lived, and not particularly useful. In this project, we will aim to create ultra-thin films and freeze in the structure using a photo-polymer that is matched to the liquid crystal. We will then aim to characterise those films and use them in novel electro-optic devices.

Theoretical Physics

11. Is water a quantum disentangled liquid? (1 or 2 students)

Dr. Zlatko Papic

12. Quantum control of many-body localized states (1 or 2 students)

Dr. Zlatko Papic

1. Localization from A(nderson) to Z(eno)(1 student)

Dr. Zlatko Papic

1. From geometry to topology of quantum systems (1 or 2 students)

Dr. Jiannis Pachos

1. Non-linear dynamics in quantum networks

Dr. Almut Beige

Astrophysics

1. Finding filaments in simulations

Dr. Sven Van Loo

Molecular clouds are often very filamentary structures. By identifying

these structures we can derive some essential properties of the clouds

and some clues of their formation process. We will test an identification

routine on some numerical models of molecular clouds.

1. The radiative overstability of dusty shocks

Dr. Julian Pittard
Project description: Dusty shocks are ubiquitous in astronomy. Radiative shocks are known to suffer from an over stability as the post-shock gas cools. However, it is not known how the presence of dust affects this behaviour. The student will make use of a state of the art computational fluid dynamics code to study this phenomena.

1. Be the PI of your own project using ALMA data

Katharine Johnston

This project will involve using data available in the archive of the radio telescope ALMA (the Atacama Large Millimeter/submillimeter Array). As the student, you will look through the archive and choose the data you would like to work on, exploring the possible science questions you may be able to answer with the data. Then you will reduce the ALMA data, with help, to answer these questions and to maybe discover some unexpected results in the process.

1. SplashLanding - Dropping Clouds onto Galactic Discs

Prof. Tom Hartquirt and Christina Burge

Supernovae inject energy into the interstellar medium, which drives some of the material into the halo of the Galaxy.A good fraction of this material cools and falls back to the disc. The encounter causes asplash,which may inducestar formation. The project concerns the nature ofthesplash.

Condensed Matter

1. Spin current generation in InAs/GaSb quantum well heterostructures.

Prof. Chris Marrows and Chris Morrison

1. Magnetostrictive thin films with perpendicular anisotropy.

Dr. Tom Moore

1. Novel skyrmion materials for magnetic storage: characterization of thin magnetic multilayer systems

Katharina Zeissler

The world is facing an ever-growing demand for data storage. One approach towards achieving higher data density is to store the information in smaller and smaller areas. Conventional magnetic materials, used for data storage, struggles to go beyond the current limits due to thermal instability. Skyrmions, thus far the smallest spin textures discovered in magnetic thin films, could form part of the solution. Thin ferromagnetic films sandwiched by heavy metal layers have shown to stabilize Skyrmions via interfacial Dzyaloshinskii-Moriya interactions (DMI).

This project will measure the magnetic properties of the fabricated multilayers using different diagnostic techniques. The aim is to investigate the DMI strength and whether any Skyrmions are detectable.

1. Tailoring superconducting nanoplates/nanowires of topological crystalline insulator Sn1-xInxTe

Dr. Satoshi Sasaki

Growth of semiconductor nanowires has been of great interest because the restricted dimensionality of the system can provide a platform of novel quantum phenomena. Superconducting nanomaterials with strong spin-orbit interaction will provide us further exotic system. We will grow superconducting nanoplates/nanowires of Sn1-xInxTe with a vapour-transport technique and characterize them by optical and atomic force microscopy, and X-ray.

1. Single crystal growth and characterization of topological insulator Bi2Se3 and Bi2Te3

Dr. Satoshi Sasaki

Topological insulators (TI) are materials which have an insulating bulk state and gapless-metallic surface states with Dirac-like band structure where spin and momentum electrons are perpendicularly locked. Therefore pure spin currents (no-net charge current) are naturally induced at the surface of TIs. Recently topological insulators have attracted a lot of interest because of its novelty and potential that can be applied to future spintronic technologies. We will grow some of conventional TIs, Bi2Se3 and Bi2Te3 with a melt-growth method and characterize them by means of optical and atomic force microscopy, and X-ray,

1. Exploring novel superconducting topological materials

Dr. Satoshi Sasaki

Recently, proximity-induced superconductivity in semiconductor materials with strong spin-orbit interaction has attracted a lot of attention because it is theoretically predicted that it can harbour Majorana fermions (MF). MFs are very mysterious quasiparticles and theexistence has not been experimentally proven yet. If discovered, innovations in future quantum technologies, in particular topological quantum computing, will be fostered. We will try to explore MFs growing several superconducting semiconductor materials based on theoretical predictions.

1. Kondo physics in a magnetic free environment for quantum devices

Dr. Oscar Cespedes

The Kondo effect describes the electron scattering by magnetic impurities in metals or quantum dots. Potential applications include sensors and quantum information processing, as the effect allows for the transport of information in systems which are too small for conventional wiring. This is an experimental project in which the student will study the possibility of measuring tuneable Kondo physics in a system free of magnetic elements, which would allow its compatibility with superconducting qubits.

1. Carbon-based magnets: reducing our dependency on rare-earths

Dr. Oscar Cespedes

Permanent magnets have applications ranging from power generation (e.g. wind turbines) to actuators (e.g. hard disks). These magnets are manufactured from alloys of transition metals with rare earths. However, rare earths are scarce, hard to mine and harmful to the environment. New strategies to replace them with novel materials have been addressed by the US Congress and the EU Parliament. We have observed that certain carbon structures can improve the magnetic properties of 3d metals, which could lead to the substitution of rare earths by eco-friendly, carbon based molecules. This is an experimental project to explore the possibility of using these nanomaterials in designer magnets.

Molecular Nanophysics

1. The effect of curvature on patterning in a biomembrane

Dr Simon Connell

The aim of this project is to investigate the influence of curvature on the phase behaviour of lipid membranes. These systems are 5 nm thick sheets that self-assemble from individual molecules in water. Although the membrane is stiff perpendicular to the plane, the individual molecules have high in-plane mobility, and can diffuse and segregate forming distinct phases. There is evidence that curvature (bending) influences the phase behaviour membranes, and a 2015 Summer student developed a simple rig for tuning the curvature of a surface by stretching a PDMS slab and exposing it to oxygen plama, forming sinusoidal wrinkles with controllable wavelength in the range of 100’s of nanometres. We will prepare curved surfaces using this apparatus and form membranes on the surface, and then observe the effect using Atomic Force Microscopy (AFM).

1. Experiments with hydrogel Nanospheres (with Dr J Mattsson, SMP)

Dr SD Connell MNP

In the past year we have been studying the material properties of hydrogel nanospheres made from a PNIPAM polymer. These are extremely soft (modulus of around 10 kPa, approximately 100x softer than a soft contact lens), about 300 nm in diameter, and thermo-responsive, swelling or collapsing at temperature of about 34 C, making them extremely useful for many industrial applications. We have many current avenues for investigation, andexperiments include creating close packed arrays on surfaces and studying the effect of introducing hard sphere (silica) defects of controlled size. This might allow us to measure the Poisson Ratio of the particles (a currently unknown value). Another possibility is using osmotic pressure to apply a force to the hydrogel, and hence measure the modulus through measure the shape change using Atomic Force Microscopy of collaped hydrogel hemispheres. This work is ongoing research, so the exact project will be determined nearer the time.

1. Modelling of diffusion and confinement

Dr. Hugo Christenson and James Cambell

We have been working to develop a simple, transparent, computationally efficient model for studying complex thermodynamic systems. In contrast to conventional molecular dynamics or Monte Carlo simulations, this offers the opportunity to illustrate the behaviour of many-component systems over relatively long timescales. Our particular interest lies in phase transitions associated with confined geometries, particularly capillary condensation and nucleation in narrow pores and acute wedges, and in the interplay of the kinetics of these processes with diffusion and adsorption. The project will involve performing careful studies of confinement phenomena which can be compared to theoretical predictions and to experimental results, and optionally helping to build upon the model itself. The project would suit a student comfortable with programming, preferably with experience of C/C++.

1. Cell capturing in a microfluidic device

Dr. Jung-uk Shim

The goal of this project is to develop a microfluidic device that is able to trap cells in the device in order to interrogate single cells with optical measurements. The device will include channels for transporting cells, valves for controlling flow,wells to store cells and potentially electrodes to apply an electric field. The important feature of the proposed microfluidic device is the ability of trapping cells in wells using the surface tensional force. Once cells are trapped in wells, they rarely move to other wells, which provide the physical address of cells determined by the trapping wells in the device. The cells will be transferred to the next region, in which various other properties of the cells can be interrogated. In order to transfer the cells the flow rate of medium will be enhanced to overcome the surface tensional force and to flush cells out of wells. The flow of cells will be controlled via embedded microfluidic valves in the device.

1. Multiplexed single molecule counting immunoassay

Dr. Jung-uk Shim

The single molecule counting immunoassay will be employed to detect multiple proteins in a single assay. The ability to simultaneously measure the abundance of multiple proteins is important because they constitutively function within networks, pathways, complexes and families. Also, there is an ongoing research trend towards developments of multiplexed biomarker assay in oncology. These multiplexed immunoassays can be realized by labelling beads with different fluorophores so that each conjugated antibody is represented by distinctively fluorescence encoded beads. A large number of beads can be encoded using various combinations of fluorescent dyes with different emission wavelengths and intensity levels usually by entrapping the fluorescent moieties in the interior of beads or by covalently attaching the dyes onto the surface of the beads. The co-existences of enzymatic amplifications and a specific bead represent the presence of a specific biomarker in sample.