felixkoh

• Kohler, Felix; Pierre-Louis, Olivier & Dysthe, Dag Kristian (2022). Crystal growth in confinement. Nature Communications. 13(1), p. 1–8. doi: 10.1038/s41467-022-34330-5. Full text in Research Archive Show summary

  Abstract The growth of crystals confined in porous or cellular materials is ubiquitous in Nature and forms the basis of many industrial processes. Confinement affects the formation of biominerals in living organisms, of minerals in the Earth’s crust and of salt crystals damaging porous limestone monuments, and is also used to control the growth of artificial crystals. However, the mechanisms by which confinement alters crystal shapes and growth rates are still not elucidated. Based on novel in situ optical observations of (001) surfaces of NaClO 3 and CaCO 3 crystals at nanometric distances from a glass substrate, we demonstrate that new molecular layers can nucleate homogeneously and propagate without interruption even when in contact with other solids, raising the macroscopic crystal above them. Confined growth is governed by the peculiar dynamics of these molecular layers controlled by the two-dimensional transport of mass through the liquid film from the edges to the center of the contact, with distinctive features such as skewed dislocation spirals, kinetic localization of nucleation in the vicinity of the contact edge, and directed instabilities. Confined growth morphologies can be predicted from the values of three main dimensionless parameters.

• Li, Lei; Kohler, Felix; Dziadkowiec, Joanna; Røyne, Anja; Marzal, Rosa M. Espinosa & Bresme, Fernando [Show all 8 contributors for this article] (2022). Limits to Crystallization Pressure. Langmuir. ISSN 0743-7463. 38(37), p. 11265–11273. doi: 10.1021/acs.langmuir.2c01325. Full text in Research Archive Show summary

  Crystallization pressure drives deformation and damage in monuments, buildings, and the Earth’s crust. Even though the phenomenon has been known for 170 years, there is no agreement between theoretical calculations of the maximum attainable pressure and experimentally measured pressures. We have therefore developed a novel experimental technique to image the nanoconfined crystallization process while controlling the pressure and applied it to calcite. The results show that displacement by crystallization pressure is arrested at pressures well below the thermodynamic limit. We use existing molecular dynamics simulations and atomic force microscopy data to construct a robust model of the disjoining pressure in this system and thereby calculate the absolute distance between the surfaces. On the basis of the high-resolution experiments and modeling, we formulate a novel mechanism for the transition between damage and adhesion by crystallization that may find application in Earth and materials sciences and in conservation of cultural heritage.

• Vestre, Katharina; Kjos, Ingrid; Guadagno, Noemi Antonella; Distefano, Marita Borg; Kohler, Felix & Fenaroli, Federico [Show all 8 contributors for this article] (2019). Rab6 regulates cell migration and invasion by recruiting Cdc42 and modulating its activity. Cellular and Molecular Life Sciences (CMLS). ISSN 1420-682X. 76(13), p. 2593–2614. doi: 10.1007/s00018-019-03057-w. Full text in Research Archive Show summary

  Rab proteins are master regulators of intracellular membrane trafficking, but they also contribute to cell division, signaling, polarization, and migration. The majority of the works describing the mechanisms used by Rab proteins to regulate cell motility involve intracellular transport of key molecules important for migration. Interestingly, a few studies indicate that Rabs can modulate the activity of Rho GTPases, important regulators for the cytoskeleton rearrangements, but the mechanisms behind this crosstalk are still poorly understood. In this work, we identify Rab6 as a negative regulator of cell migration in vitro and in vivo. We show that the loss of Rab6 promotes formation of actin protrusions and influences actomyosin dynamics by upregulating Cdc42 activity and downregulating myosin II phosphorylation. We further provide the molecular mechanism behind this regulation demonstrating that Rab6 interacts with both Cdc42 and Trio, a GEF for Cdc42. In sum, our results uncover a mechanism used by Rab proteins to ensure spatial regulation of Rho GTPase activity for coordination of cytoskeleton rearrangements required in migrating cells.

• Li, Lei; Sanchez, Jesus Rodriguez; Kohler, Felix; Røyne, Anja & Dysthe, Dag Kristian (2018). Microfluidic control of nucleation and growth of CaCO3. Crystal Growth & Design. ISSN 1528-7483. 18(8), p. 4528–4535. doi: 10.1021/acs.cgd.8b00508. Full text in Research Archive Show summary

  A novel method for studying nucleation and growth of CaCO3 crystals in situ has been developed and tested rigorously. We demonstrate that precise flow control is essential and how this is achieved. The method has the advantage that one may study single crystals of polymorphs that are thermodynamically unstable in collections of many crystals and that one obtains precise and accurate growth rates without any extra assumptions. We also demonstrate that, at low supersaturations where 2D nucleation does not occur, we measure the growth rate constant of calcite to be 5 times larger than that reported by batch methods and 2 orders of magnitude larger than that measured by atomic force microscopy. Considering the large interest in calcite growth in, for example, geoscience, environmental science, and industry, it is important to explain the discrepancy of growth rate constants between different methods. The method presented here can easily be applied to many other minerals.

• Pluymakers, Anne Marie Henriette; Liu, J.; Kohler, Felix; Renard, Francois & Dysthe, Dag Kristian (2018). A high resolution interferometric method to measure local swelling due to CO2 exposure in coal and shale. International Journal of Coal Geology. ISSN 0166-5162. 187, p. 131–142. doi: 10.1016/j.coal.2018.01.007. Full text in Research Archive
• Kohler, Felix; Gagliardi, Luca; Pierre-Louis, Olivier & Dysthe, Dag Kristian (2018). Cavity Formation in Confined Growing Crystals. Physical Review Letters. ISSN 0031-9007. 121(9), p. 1–5. doi: 10.1103/PhysRevLett.121.096101. Full text in Research Archive Show summary

  Growing crystals form a cavity when placed against a wall. The birth of the cavity is observed both by optical microscopy of sodium chlorate crystals (NaClO3) growing in the vicinity of a glass surface, and in simulations with a thin film model. The cavity appears when growth cannot be maintained in the center of the contact region due to an insufficient supply of growth units through the liquid film between the crystal and the wall. We obtain a nonequilibrium morphology diagram characterizing the conditions under which a cavity appears. Cavity formation is a generic phenomenon at the origin of the formation of growth rims observed in many experiments, and is a source of complexity for the morphology of growing crystals in natural environments. Our results also provide restrictions for the conditions under which compact crystals can grow in confinement.

• Li, Lei; Kohler, Felix; Røyne, Anja & Dysthe, Dag Kristian (2017). Growth of calcite in confinement. Crystals. 7(12). doi: 10.3390/cryst7120361. Full text in Research Archive

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• Høgberget, Jørgen; Kohler, Felix; Røyne, Anja; Jettestuen, Espen & Dysthe, Dag Kristian (2016). Combining in situ Interferometry and Kinetic Monte Carlo to Study Mechanisms of Nanoconfined Crystallization. Full text in Research Archive
• Kohler, Felix & Dysthe, Dag Kristian (2015). Nanoconfined Crystal Growth investigated by Reflection Interference Contrast Microscopy. Full text in Research Archive
• Dysthe, Dag Kristian; Neuville, Amélie; Luu, Thi Thuy; Kohler, Felix & Li, Lei (2015). Microfluidic Tools for Reactive Transport In Porous Media. Full text in Research Archive

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