I worked as a postdoc in Prof. Martin Frenz’ Group Biomedical Photonics at the Institute of Applied Physics at the University of Bern. I was heading two femtosecond laser labs, each equipped with several microscopes to investigate samples from a wide range of origins. We constructed a custom built multiphoton microscope for geological research and additionally modified a commercially available combined laser scanning confocal and multiphoton microscope for use in biological and biomedical research. The software for the custom built microscope was developed by me using LabView, and is licensed under the GPL. It can be downloaded from Bitbucket. On the commercially aquired microscope, I also instructed external partners in its use, and we had several collaborations implementing this state-of-the-art setup. As part of my postdoc work, I supervised PhD and master students and tought courses.

Nanoparticles in the Body: As part of the NRP 64, we investigated the influence of nanoparticles on healthy tissue. Nanoparticles are ubiquitous in today’s world, making part of sun screen and other cosmetics, being used as surface enhancements in materials and as ingredients of drugs and food. However, the influence of the particles on health is barely investigated. The NRP 64 aims to narrow the gap in the current knowledge. In our part of the program, we investigated how neurons react to nanoparticles and whether these are toxic to the cells.

Phyllotaxis: A second project we conducted is the investigation of leaf patterning in plants. The leafs in plants grow in fixed patterns. How these patterns emerge still remains unclear; it is commonly believed that the hormone Auxin and its distribution in the meristem is key to the process. Using tomato saplings, we investigated this claim: by blocking specific pathways inside the meristem using the femtosecond pulse laser, we blocked the auxin flow from or to specific regions to assess the part these regions play in the big picture [Deb et al., 2015].

Climate Data from Stalagmites: Furthermore, we investigated aqueous inclusions in stalagmites; the water entrapped in stalagmites upon their formation keeps a record of the temperature present at the time of the formation. If this temperature can be measured, a local climate proxy for long gone eras can be established. We used ultrashort laser pulses to create a vapour bubble in cooled, metastable water inclusions. The measurement of the bubble radius then leads to the calculation of the formation temperature of the inclusion and hence the stalagmite [Krüger et al., 2011]. To assess the state variables of any fluid inclusion, I wrote a Matlab-class, based on IAPWS95 [Marti et al., 2012], that can calculate these at any given temperature. The Routine is licensed under the GPL and can be downloaded from GitHub.

Intrecellular Parasites: We also showed that it is possible to use femtosecond laser pulses to open a pathway for the transfection of the intracellular parasite Theileria Annulata. This opens the possibility of genetically altering the parasite and thus researching the ways it interacts with its host cell [Stoller et al., 2008]. This can lead to a better understand of both Theileria Annulata and Theileria Parva, its close relative, that is responsible for a great yearly economic loss of cattle valued more than 168 million US-dollars in Africa.