In the process of metastasis, cancer cells may transmigrate through the endothelium barrier of the vascular walls and into the circulatory blood system. During this process, the cancer cells...Show moreIn the process of metastasis, cancer cells may transmigrate through the endothelium barrier of the vascular walls and into the circulatory blood system. During this process, the cancer cells interact with the endothelial cells, resulting in the alternation of their mechanical properties. Although this interaction has been broadly studied from the perspective of cancer cells, no thorough investigation of the endothelial mechanical properties has been performed. In this thesis, by using a micro-rheology AFM-based approach, we show that the properties of endothelial cells change when cultured in cancer cell conditioned medium, as well as when in contact with cancer cells. We found that the stiffness of endothelial cells increased when cultured in a low-dilution cancer cell medium, while it decreased in high-dilution medium. This change was also evident on the viscoelasticity of the cells, with the endothelial cells cultured in high dilution medium showing lower viscoelastic properties. Furthermore, endothelial cells in direct contact with a cancer cell showed an increased height, as a result of the cancer cell's transmigration through the monolayer. Our findings demonstrate that the properties of endothelial cells change indirectly due to cancer cell secreted substances, and directly during the cancer cells' physical transmigration. This indicates that the endothelium is actively responding to the presence of cancer cells, rather than being a passive barrier as once believed.Show less
Twisted bilayer graphene at a magic angle might be used to increase our understanding of high temperature superconductivity. Studying 2D-materials with an Atomic Force Microscope (AFM) yields...Show moreTwisted bilayer graphene at a magic angle might be used to increase our understanding of high temperature superconductivity. Studying 2D-materials with an Atomic Force Microscope (AFM) yields information on its surface properties, such as its topography or its conductivity. In this thesis, AFM work has been done on different samples, with the final goal of identifying moiré patterns. AFM tapping mode shows clear roughness decline of a silicon/silicon oxide wafer after annealing 500 degrees for 24 hours. AC mode on layered graphene placed on an identical substrate was able to identify different atomic layers clearly. Sputtered gold, graphite and evaporated gold have been analyzed with current sensing AFM. Finally, I/V-curves have been acquired with AFM contact mode on sputtered gold, corresponding to theoretical expectations. All initial work has been done to measure I/V curves and start conductive AFM measurements on twisted bilayer graphene, in hopes of identifying moiré patterns in the current map.Show less
In this thesis a new possible method to measure the Young’s Modulus (YM) of Red Blood Cells (RBCs) is presented: Bimodal AFM. Theoretical background for this method is given, and possible future...Show moreIn this thesis a new possible method to measure the Young’s Modulus (YM) of Red Blood Cells (RBCs) is presented: Bimodal AFM. Theoretical background for this method is given, and possible future implementation at LION is discussed. Furthermore it is explained how the available nanoindentation method and acccompanying set-up were improved upon. Most notable are the implementation of a PID feedback system for environmental control, the use of more rigid cantilevers, and the implementation of an automated cropping program for images taken with the Atomic Force Microscope (AFM). Results gathered with this improved set-up indicate a strong correlation between relative and the YM of RBCs, confirming findings from research previously done at LION.Show less
This report addresses the crucial question of bloodstain age determination for forensic investigations, with particular focus on the use of Atomic Force Microscopy, specifically Contact Resonance...Show moreThis report addresses the crucial question of bloodstain age determination for forensic investigations, with particular focus on the use of Atomic Force Microscopy, specifically Contact Resonance Force Microscopy. Because of the laboratory ban due to the covid-19 crisis, extra emphasis is laid on literature review of other known forensic methods that have been proposed to solve this question. Furthermore, some preliminary results obtained with the more ‘traditional‘ nano-indentation AFM technique are presented.Show less
The coexistence of the semi-conducting 2H and quasi-metallic 1T’ monolayer MoS2 phases has great potential in, for example, low-resistance contacts. In this research MoS2 on gold samples have been...Show moreThe coexistence of the semi-conducting 2H and quasi-metallic 1T’ monolayer MoS2 phases has great potential in, for example, low-resistance contacts. In this research MoS2 on gold samples have been fabricated. Several different fabrication procedures have been tested including stamping, gold-mediated exfoliation and hydrogen plasma cleaning. Measurements identifying the 2H phase have been made using Atomic Force Microscopy and Low Energy Electron Microscopy. Although 1T’ could not be observed, insights are gained into the various fabrication processes.Show less
This thesis deals with the use of conducting AFM to image the topography and conducting properties of graphene on SiO2. Specifically,the current image will be used to distinguish graphene from SiO2...Show moreThis thesis deals with the use of conducting AFM to image the topography and conducting properties of graphene on SiO2. Specifically,the current image will be used to distinguish graphene from SiO2 and the height image to identify the edge of the wafer. These together can show how far graphene reaches this edge. For testing the usability of the Conducting AFM module measurements were also made on gold and on graphite. Lastly, specific settings were tested and discussed for optimal current imaging results.Show less
When Van derWaals materials are reduced to two-dimensional atomic crystals, their physical properties start to change. For most materials these properties and phenomena are still unresearched. Van...Show moreWhen Van derWaals materials are reduced to two-dimensional atomic crystals, their physical properties start to change. For most materials these properties and phenomena are still unresearched. Van der Waals materials can be created to be atomically thin, to layers of a single atom thick. One class of these materials are transition metal dichalcogenide materials (TMDs). There exist different crystalline structures of TMDs, which are called polytypes. Here, TaS2 flakes are fabricated in order to study charge density waves (CDWs). A protocol to fabricate large thin flakes is developed along with a simple and quick method to determine the layer thickness with the use of an optical microscope. The calculated thicknesses are then verified with Atomic Force Microscopy (AFM) measurements. Low Energy Electron Microscopy (LEEM) measurements are performed on thick flakes in order to research CDWs. Although confirmation of CWDs is absent, different domains of reflective electron intensity and various structures are observed. These features are compared with AFM measurements. The flake existing of different polytypes could be the cause for the observed contrasts. The reflection of electrons is observed until an energy of 150 eV.Show less
In the search of small and functional molecular devices, we have created and investigated 20 different self-assembled multilayers (SAMTs) each consisting of two self-assembled monolayers (SAM) on...Show moreIn the search of small and functional molecular devices, we have created and investigated 20 different self-assembled multilayers (SAMTs) each consisting of two self-assembled monolayers (SAM) on top of each other. We compare the molecular combinations to their inverse combinations, investigate their length dependence on the conductance and look for interesting features. Each SAM consists of one type of molecule (there are five different ruthenium complex molecules in total) and each bilayer is grown on an indium tin oxide substrate. Then current-voltage (I-V) curves are taken using conductive atomic force microscopy (C-AFM) to characterize the samples after the relative humidity (RH) of the setup has been brought to ≈ 5% and ≈ 50% respectively and the rectification ratio (RR) for each molecular combination is calculated. Double layers consisting of the same Ru-complexes and combinations of different molecules are measured. We find that while the shape of the I-V curves and the conductance of the combinations are different compared to those of their inverse combination, the rectification ratio (RR) (and in particular the direction of rectification) is not. The highest RR found is RRhumid = 10^(-2.0±0.6) at 1.0 V for the combination with bottom layer 1-Ru-N and top layer 2-Ru-N (decoupled). Furthermore, we see that while most bilayers have current values that agree to a conductance that decreases exponentially with the length, some do not. Lastly, we observe hysteresis in three samples. Our findings in this exploratory experiment contribute to the knowledge of charge transport in junctions consisting of layers of complex molecules.Show less
The possibly crucial role of the presence of iron nanoparticles in the humain brain, in neuronal diseases such as Alzheimers’ disease makes them interesting subjects for research. In magnetic...Show moreThe possibly crucial role of the presence of iron nanoparticles in the humain brain, in neuronal diseases such as Alzheimers’ disease makes them interesting subjects for research. In magnetic resonance imaging, contrast arises due to the presence of such magnetic entities. In this report we address models that describe the mechanism behind this induced contrast, due to the presence of ferritin and magnetite nanoparticles. We have measured the transverse relaxation T2 and T 2 times using the MSME and MGE sequence. We found a linear decrease in both the relaxation times as a function of particle concentration. Concluded is that the relaxation of the magnetic nanoparticles is dominated by the diffusion of protons surrounding the magnetic nanoparticle, which is described by the motional averaging regime. We used Atomic Force Microscopy and Transmission Electron Microscopy to characterize the sample.Show less
