Optimisation of surface coverage paths used by a non-contact robot painting system

This thesis proposes an efficient path planning technique for a non-contact optical “painting” system that produces surface images by moving a robot mounted laser across objects covered in photographic emulsion. In comparison to traditional 3D planning approaches (e.g. laminar slicing) the proposed algorithm dramatically reduces the overall path length by optimizing (i.e. minimizing) the amounts of movement between robot configurations required to position and orientate the laser. To do this the pixels of the image (i.e. points on the surface of the object) are sequenced using configuration space rather than Cartesian space. This technique extracts data from a CAD model and then calculates the configuration that the five degrees of freedom system needs to assume to expose individual pixels on the surface. The system then uses a closest point analysis on all the major joints to sequence the points and create an efficient path plan for the component. The implementation and testing of the algorithm demonstrates that sequencing points using a configuration based method tends to produce significantly shorter paths than other approaches to the sequencing problem. The path planner was tested with components ranging from simple to complex and the paths generated demonstrated both the versatility and feasibility of the approach

Probing Magnetic Excitations and Correlations in Single and Coupled Spin Systems with Scanning Tunneling Spectroscopy

Spectroscopic measurements with low-temperature scanning tunneling microscopes have been used very successfully for studying not only individual atomic or molecular spins on surfaces but also complexly designed coupled systems. The symmetry breaking of the supporting surface induces magnetic anisotropy which lead to characteristic fingerprints in the spectrum of the differential conductance and can be well understood with simple model Hamiltonians. Furthermore, correlated many-particle states can emerge due to the interaction with itinerant electrons of the electrodes, making these systems ideal prototypical quantum systems. In this manuscript more complex bipartite and spin-chains will be discussed additionally. Their spectra enable to determine precisely the nature of the interactions between the spins which can lead to the formation of new quantum states which emerge by interatomic entanglement.Comment: 46 pages, 21 figure

Molecular Self-assembly of Functionalized Pentacenes and Fullerenes on Metal Surfaces by STM and DFT Investigations

Enormous efforts have been made in seeking alternative pathways to more effectively use solar energy. Organic solar cells, composed essentially of carbon-based organic molecular materials, have attracted considerable scientific and industrial attentions because of their economic and environmental benefits. It is advantageous to have the comprehension of the molecular structures and interfacial morphologies for these active molecular materials on substrates in the nanoscale regime. Controlling the heterostructures of the molecular donor and acceptor materials is essential to overcoming the efficiency bottleneck in organic photovoltaics. Molecular self-assembly on patterned substrates provides a bottom-up approach to create well-controlled molecular heterojunctions and a pathway to engineer the donor-acceptor interface at the molecular level. I present a study of the self-assembly of functionalized pentacenes (6,13-dichloropentacene) and fullerenes (C60) into a layer-by-layer heterojunction on a stepped gold vicinal surface Au(788) by scanning tunneling mi- croscopy (STM) characterizations and density functional theory (DFT) calculations. Au(788) is a vicinal surface of Au(111) and exhibits complex reconstruction patterns that provide a natural template for organic molecular self-assembly. The 6,13- dichloropentacene (DCP) molecules, optimized for photovoltaic applications, form a striking long-range ordered self-assembled monolayer (SAM) on a stepped Au(788) vicinal surface. The SAM resembles a perfect brick-wall pattern with the long-axis parallel to the step edges. This DCP SAM serves as the electron-donor layer. Subsequently deposited C60 molecules form long parallel chains with a rectangular arrangement atop the intact DCP SAM on Au(788). The C60 molecular chain is commensurate (3:2) with the DCP lattice along the long axis: three fullerenes line up with two DCP molecules. The C60 adlayer serves as the electron-acceptor layer. The novel organic-metal and organic donor-acceptor interfacial interactions, as well as the adsorption geometry, have been explored by DFT. The interaction between the C60 molecules and the gold substrate is well screened by the DCP monolayer. The perfectly ordered DCP SAM is unaffected by the C 60 chain formation. The charge transfer and dipole moment between the C60 and DCP monolayer interface have been calculated by DFT. Superior electronic transport properties are expected for these well-ordered bilayer heterojunctions for a potential improvement of the photovoltaic efficiency

Biomimetic bilayer membranes made from polymers and lipids

Amphiphile Blockcopolymere sind in der Lage in Wasser Morphologien auszubilden, die analog sind zur hydrophil-hydrophob-hydrophil-Struktur von natürlichen Lipiddoppelschichten. In dieser Arbeit wird zum ersten Mal die Präparation und Charakterisierung von oberflächengestützten Polymerdoppelschichten aus Polybutadien-b-Polyethylenoxid (PB-PEO) beschrieben. Für die Herstellung dieser Strukturen wurden zwei unterschiedliche Präparationsstrategien verfolgt. Der erste Weg besteht aus einer zweistufigen Methode, bei der im ersten Schritt organisierte Monoschichten mittels Langmuir-Blodgett-Transfer auf Gold übertragen und kovalent angebunden werden. Im zweiten Schritt werden hydrophobe Wechselwirkungen ausgenutzt, um über Langmuir-Schaefer-Transfer eine weitere Schicht aufzubringen. Somit wurden homogene Architekturen erzeugt, die oberflächengestützten Lipiddoppelschichten gleichen. Als alternativer, einstufiger Ansatz zur Herstellung von Polymerdoppelschichten wurde das Spreiten von Polymervesikeln auf Gold verfolgt. Auch hierdurch ließen sich Doppelschichtstrukturen mit einer vollständigen Oberflächenbedeckung erzeugen. Die hergestellten Polymerdoppelschichten besitzen eine Dicke von 11-14 nm, die von der Präparationsmethode abhängt. Die Polymerstrukturen weisen bei Trocknung für 1.5 h eine Stabilität gegenüber Luft auf. Bei längeren Trocknungszeiten von ca. 12 h kommt es zu einer Reorganisation der Oberfläche. Dies deutet darauf hin, dass Wasser dazu notwendig ist die Strukturen auf lange Sicht zu stabilisieren. Um die Biokompatibilität der Polymerschichten nachzuweisen, wurden die Wechselwirkungen mit dem membranaktiven Peptid Polymyxin B und dem Transmembranprotein α-Haemolysin gezeigt. Mobilität ist ein wichtiger Faktor für die korrekte Funktion vieler Transmembranproteine. Um die laterale Diffusionsdynamik innerhalb der künstlichen Strukturen zu untersuchen, wurde die Mobilität eines integralen Modellpeptids und von fluoreszierenden Membransonden gemessen. Es konnte mit einzelmolekülempfindlichen Techniken gezeigt werden, dass das α-helikale Peptid und die kleinen Fluoreszenzfarbstoffe frei im hydrophoben Kern der Polymerdoppelschicht diffundieren können. Die Diffusion von beiden Spezies scheint stark von der Fluidität der Polymermatrix beeinflusst zu sein. Ein weiterer Teil dieser Arbeit widmet sich der Entwicklung eines angemessenen, lipidbasierten Referenzsystems für zukünftige Proteinuntersuchungen. Hierzu wurde eine neue Methode zu Herstellung von peptidgestützten Lipiddoppelschichtmembranen entwickelt. Dies wurde durch kovalente Befestigung eines Thiopeptids an einen Goldfilm und darauffolgende Anbindung eines Lipids erreicht. Zur Ausbildung der Lipiddoppelschicht auf dem Lipopeptidunterbau wurder der Rapid Solvent Exchange verwendet. Die Ausbildung der Lipiddoppelschicht wurde sowohl auf microskopischer als auch auf makroskopischer Ebene nachgewiesen. Im letzten Schritt wurde die Anwendbarkeit des Modelsystems für elektrochemische Messungen durch den funktionalen Einbau des Ionentransporters Valinomycin unter Beweis gestellt.Amphiphilic block copolymers form morphologies in water which are similar to the hydrophilic-hydrophobic-hydrophilic structure of natural lipid bilayers. In this thesis the preparation of solid supported polymer bilayers from poly (butadiene)-b-poly(ethylene oxide) (PB-PEO) and their physicochemical characterization is presented. Two different strategies for the preparation of polymeric bilayers were developed. The first route is a two step process utilizing an organized monolayer which was covalently attached to ultrasmooth gold upon Langmuir-Blodgett transfer. Hydrophobic interactions, on the other hand, were exploited to attach the second monolayer via Langmuir-Schaefer transfer. As a result, a homogeneous structure, similar to supported lipid bilayers was obtained. Alternatively vesicle spreading on gold is presented as an easy one step route to supported polymer bilayers. Again this produces bilayer coated surfaces with a high coverage. The prepared polymer bilayers possess a thickness of 11-14 nm depending on the preparation technique. The polymer structures resist drying for about 1.5 hours but disassemble after longer drying periods of 12 hours. This means that water is still necessary to stabilize these morphologies in the long term. To prove the biocompatibility it was shown that the membrane active peptide polymyxin B and the transmembrane protein α-haemolysin interact with the artificial membrane structure. rnMobility is an important factor for the correct function of many transmembrane proteins. To evaluate the lateral mobility of an integral model peptide and fluorescent membrane probes within the polymer bilayer plane 2D-diffusion was studied. It was proven by single molecule sensitive techniques that an α-helical peptide as well as small fluorescent probes can diffuse freely along the bilayer. The diffusion of either species seems to be strongly coupled to the fluidity of the membrane constituting matrix.rnA separate part of this thesis was dedicated to the search for an appropriate lipid based reference system for future protein studies. Therefore a new preparation route towards a peptide tethered lipid bilayer membrane was developed. This was achieved by covalent binding of a thiopeptide to a gold support and subsequent coupling of a lipid to that layer. The bilayer built-up on top of the produced lipopeptide support is completed through rapid solvent exchange. The lipid bilayer formation was proven microscopically as well as macroscopically. Finally the applicability of the model system for electrochemical measurements of transmembrane proteins was demonstrated with the functional incorporation of the ion carrier valinomycin.r

A three dimensional kinetic Monte Carlo model for simulating the carbon/sulfur mesostructural evolutions of discharging lithium sulfur batteries

The carbon/sulfur composite cathodes of lithium sulfur batteries undergo mesostructural evolutions during discharge due to the dissolution/precipitation reactions of solid sulfur and Li2S. Furthermore, the cathode design and discharge parameters also impact the mesostructural evolutions of carbon/sulfur composites. In order to compare and study these mesostructural evolutions, we have developed a novel three dimensional kinetic Monte Carlo (kMC) model based on an algorithm called Variable Step Size Method (VSSM). Our model describes mechanisms such as dissolution of solid sulfur, reactions and diffusions of different polysulfides and electrodeposition of Li2S. The initial carbon/sulfur mesostructure used in our model is created based on its desired structural and geometric properties using an in silico method. In this paper, we present the theoretical development of our kMC model and demonstrate its capabilities using discharge simulations of a model carbon/sulfur mesostructure under two different rates (C-rates) namely C/2 and 2C. Furthermore, we also present the impact of initial loading on the 2C discharge simulation.Fil: Thangavel, Vigneshwaran. Université de Picardie Jules Verne. Laboratoire de Réactivité et Chimie des Solides; Francia. Centre National de la Recherche Scientifique; FranciaFil: Guerrero, Oscar Xavier. Instituto Politécnico Nacional. Centro de Investigación y de Estudios Avanzados. Departamento de Química; MéxicoFil: Quiroga, Matías Abel Oscar. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Centre National de la Recherche Scientifique; FranciaFil: Mikala, Adelphe Matsiegui. Centre National de la Recherche Scientifique; Francia. Université de Picardie Jules Verne. Laboratoire de Réactivité et Chimie des Solides; FranciaFil: Rucci, José Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centre National de la Recherche Scientifique; Francia. Université de Picardie Jules Verne. Laboratoire de Réactivité et Chimie des Solides; FranciaFil: Franco, Alejandro A.. Centre National de la Recherche Scientifique; Francia. Université de Picardie Jules Verne. Laboratoire de Réactivité et Chimie des Solides; Franci

On the transport of alkali ions through polymeric mold compounds and polyelectrolyte membranes.

The aim of this work is the attempt in understanding ion transport properties across structured materials such as polyelectrolyte multilayers (PEMs) and highly filled epoxy resins used as an encapsulant, i.e. mold compounds. The ion transport properties are studied by means of the technique of charge attachment induced transport (CAIT), which was recently developed and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The mold compounds studied in this work are of four types (MCP1, MCP2, MCP3, MCP4) with a composition of 80% - 88% of silica filler and the rest of raw materials such as epoxy resin, hardener and flame retardant. The samples are analyzed by means of the CAIT technique, leading to the evaluation of values of ionic conductivity and activation energy related to the process of transport of potassium ions. The ionic conductivity of the mold compounds is on the order of 10-12/10-13 S/cm, while activation energy values are in a range of 1.3 eV - 2.7 eV. For a better understanding of the potassium diffusion process into the mold compounds, the diffusion of potassium through MCP3 sample is investigated via a combination of CAIT method and an ex-situ ToF-SIMS analysis. The ToF-SIMS analysis reveals a depth diffusion profile of the potassium into the material. A mathematical theory is established in order to evaluate the diffusion coefficients for the transport of potassium. According to the numerical procedure, a good fit between experimental and theoretical data is achieved assuming the presence of two different transport pathways operative inside the material: diffusion along the boundaries of grains, i.e. zones of accumulation of the inorganic component of the mold compound and diffusion through the bulk. Diffusion coefficients of DB = 1.8 x 10-21 cm2s-1 and DBG = 5.4 x 10-20 cm2s-1 are found for bulk and grain boundary diffusion, respectively. The PEM films studied in this work are prepared from the layer-by-layer assembly of ionic p-sulfonato-calix[8]arene (calix8) and cationic poly(allylamine hydrochloride) (PAH) onto functionalized gold substrates. Samples with n = 1, 3, 6, 9, 12, 15, 20, 30 bilayers are analyzed by means of the CAIT technique. The data lend support to the conclusion that conductivity, as well as activation energy measurements for (PAH/calix8)n, cannot be acquired under the conditions of the CAIT method, due to the low resistivity shown from the specific PEMs analyzed. Studies on the transport of Li+, K+ and Rb+ through (PAH/calix8)30 are performed by means of CAIT and ToF-SIMS. For each ion beam (Li+, K+, Rb+) two kind of experiments are performed: (PAH/calix8)30 samples are bombarded with the three different alkali ions varying the time for the bombardment, i.e. 5 seconds in one case and 100 seconds in the other. The evaluation of the concentration profiles gives qualitative information regarding the transport properties, whereas numerical analysis of the lithium and rubidium concentration profiles for 5 seconds long bombardment provides quantitative information on the diffusion process. The numerical calculation reveals that the lithium and rubidium transport across the membrane results in a combination of two diffusion pathways accounting for diffusion of slow ions and fast ions. For the lithium case, a good fit is achieved using diffusion coefficients of Dslow,Li+ = 0.4 x 10-16 cm2/s and Dfast,Li+ = 1.2 x 10-15 cm2/s and assuming that 40% of the incoming ions enter the slow pathway, whereas the rest of the ions is transported via a fast pathway. For the rubidium case, the numerical calculation reveals that the fast diffusion pathway is predominant: only the 0.01% of the rubidium ions enter the slow pathway, whereas the rest is dominated from the faster one, with a Dfast,Rb+ = 7 x 10-15 (± 1.5 x 10-15) cm2/s. The study of ion transport of alkali ions Li+ and Rb+ across calixarenes-based PEMs leads thus to the conclusion that the presence of the calixarenes units may influence the type of transport. Lastly, studies of voltage offset measured on current-voltage curves in a typical CAIT experiment are presented. This study aims to give a better understanding of the process beyond the measured voltage offset. In order to do that, a basic CAIT experiment is performed, where a metal plate is bombarded with an ion beam from a potassium emitter of the composition KAlSi2O6 : Mo (1:9). The registered current–voltage curves show finite offsets in the order of 0.5 eV. In order to investigate the detection process of the specific KAlSi2O6 : Mo (1:9) emitter, values of ionic and electronic work function are evaluated. By means of a theoretical model, the recombination of K+ ions from Leucite KAlSi2O6 : Mo (1:9) onto the metal detector is traced to a combination of the ionic work function of the emitter material, the electronic work function of the emitter material and the recombination energy of the elemental potassium I.E.K