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Timonen, Jaakko

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Timonen

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Jaakko

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Timonen, Jaakko

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2016 - 20173

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Author's Publications: search.filters.isAuthorOfPublication.b42ed5ef-501c-445d-89e2-1317b81517c7

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Now showing 1 - 3 of 3
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    Bacterial Interactions with Immobilized Liquid Layers
    (Wiley, 2016) Kovalenko, Yevgen; Sotiri, Irini; Timonen, Jaakko; Overton, Jonathan C.; Holmes, Gareth; Aizenberg, Joanna; Howell, Caitlin
    Bacterial interactions with surfaces are at the heart of many infection-related problems in healthcare. In this work, the interactions of clinically-relevant bacteria with immobilized liquid (IL) layers on oil-infused polymers are investigated. Although oil-infused polymers reduce bacterial adhesion in all cases, complex interactions of the bacteria and liquid layer under orbital flow conditions are uncovered. The number of adherent Escherichia coli cells over multiple removal cycles increases in flow compared to static growth conditions, likely due to a disruption of the liquid layer continuity. Surprisingly, however, biofilm formation appears to remain low regardless of growth conditions. No incorporation of the bacteria into the layer is observed. Bacterial type is also found to affect the number of adherent cells, with more E. coli remaining attached under dynamic orbital flow than Staphylococcus aureus, Pseudomonas aeruginosa under identical conditions. Tests with mutant E. coli lacking flagella confirm that flagella play an important role in adhesion to these surfaces. The results presented here shed new light on the interaction of bacteria with IL layers, highlighting the fundamental differences between oil-infused and traditional solid interfaces, as well as providing important information for their eventual translation into materials that reduce bacterial adhesion in medical applications.
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    Photothermally triggered actuation of hybrid materials as a new platform for in vitro cell manipulation
    (Springer Nature, 2017) Sutton, Amy; Shirman, Tanya; Timonen, Jaakko; England, Grant Tyler; Kim, Philseok; Kolle, Mathias; Ferrante, Thomas; Zarzar, Lauren; Strong, Liz; Aizenberg, Joanna
    Mechanical forces in the cell’s natural environment have a crucial impact on growth, differentiation and behavior. Few areas of biology can be understood without taking into account how both individual cells and cell networks sense and transduce physical stresses. However, the field is currently held back by the limitations of the available methods to apply physiologically relevant stress profiles on cells, particularly with sub-cellular resolution, in controlled in vitro experiments. Here we report a new type of active cell culture material that allows highly localized, directional, and reversible deformation of the cell growth substrate, with control at scales ranging from the entire surface to the subcellular, and response times on the order of seconds. These capabilities are not matched by any other method, and this versatile material has the potential to bridge the performance gap between the existing single cell micro-manipulation and 2D cell sheet mechanical stimulation techniques.
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    Oleoplaning droplets on lubricated surfaces
    (Springer Nature, 2017) Daniel, Dan; Timonen, Jaakko; Li, Ruoping; Velling, Seneca J.; Aizenberg, Joanna
    Recently, there has been much interest in using lubricated flat and nano-/micro-structured surfaces to achieve extreme liquid-repellency: any foreign droplet immiscible with the underlying lubricant layer was shown to slide off at a small tilt angle < 5◦. This behavior was hypothesized to arise from a thin lubricant overlayer film sandwiched between the droplet and solid substrate, but this has not been observed experimentally. Here, using confocal optical interferometry, we are able to visualize the intercalated film under both static and dynamic conditions. We further demonstrate that the lubricant flow entrained by droplet motion can transform a partially dewetted film into a continuous layer, by generating a sufficient hydrodynamic force to lift the droplet over the solid substrate. The droplet is therefore oleoplaning—akin to tires hydroplaning on a wet road—with minimal dissipative force (down to 0.1 µN for 1 µl droplet when measured using a cantilever force sensor) and no contact line pinning. The techniques and insights presented in this study will inform future work on the fundamentals of wetting for lubricated surfaces and enable their rational design.