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    Molecular Rotors and Switches between Thermal and Electronic Excitation
    Single molecule machines on a surface can convert external stimuli into motion. In the last years, several examples of rotations, translations, or conformational changes of molecules on a surface under the tip of a scanning tunneling microscope have been reported. However, the next step, i.e., developing mechanical molecular devices able to produce work or store energy, requires controlling the movement. For this, a detailed understanding of the underlying physical mechanisms is needed, which is still lacking. Thermal excitation can provide energy to the ground state of a molecule, yet according to the microscopic reversibility principle, unidirectional rotation is impossible in this case. On the other hand, tunneling electrons interact with the electronic excited states of the molecule on each electron transfer event and can allow directed, i.e., controlled motion. Both energy sources are available under the tip of a scanning tunneling microscope. In this project, we will combine molecular design and synthesis with scanning tunneling microscope experiments (imaging, spectroscopy, and manipulation) at variable temperatures to investigate molecular machines on a Au(111) surface and elucidate the physical mechanisms inducing controlled movements and conformational changes. Based on the established collaboration between the two participating groups, we will start with the synthesis of specifically designed vertical rotors and switches. These molecular machines contain two structural elements, i.e., an anchoring group for stable binding to the surface, and a switching or rotating part spatially decoupled from the surface. For the anchoring, we will employ N-heterocyclic carbenes, and combine them with molecular switches and rotors designed for having different energetic barrier heights for rotation. The vertically anchored molecular machines will then be tested using scanning tunneling microscopy. Specifically, we will combine surface thermal heating with tunneling electron excitation. The latter allows involving the electronic excited states of the molecule, a possibility which is absent in a classical case. The conformational changes of the switches, i.e., the toggeling between different states, will be induced by inelastic tunneling electrons and electric fields. The molecular rotors will be kept at a fixed temperature (varying from 5 K to RT) to investigate how thermal energy can be transferred to molecular mechanical degrees of freedom. Determining how the interplay between thermal energy and electron tunneling excitation contributes to movement will fundamentally advance the understanding of chemical reactions and mechanics on surfaces and provide unique information for the design of innovative molecular machines able to store thermal energy or produce work. In terms of quantum engineering, this opens fascinating perspectives in the direction of mono-thermal motors.
      21
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    Development of the interdependencies of agile methods for information flow design to increase flexibility and efficiency in the development of mechatronic systems
    In order to remain competitive, it is necessary for companies to transform creative ideas into innovative products in the shortest possible time. At the same time, they are increasingly confronted with the need to react quickly and flexibly to changing conditions in development and to utilise development resources as effectively as possible. Against this background, agile methods are also attracting more and more attention for the development of mechatronic systems, as they increase the ability to react in dynamic development environments and offer potential for exploring solution spaces for development. Studies show that the benefits of agile working lie primarily in the effects of self-organisation, the ability to learn and transparency in the development process. This technical management is particularly necessary due to the division of labour in the development of complex mechatronic systems in order to consolidate work results and provide the development teams with the relevant information to solve their specific tasks. Methods that support synthesis and analysis in terms of finding solutions are used in parallel, as they address technical-physical development. While development methodological relationships and the associated cause-and-effect relationships have been widely researched and are very well understood, the mechanisms of action for the successful use of agile methods to support technical management have not yet been sufficiently investigated or understood. The aim of this research project is therefore to develop explanatory approaches for the mechanisms of action of agile methods. This is based on the assumption that agile methods certainly provide benefits for development methodological considerations, but that additional approaches from project management and organisational sciences are necessary for a better understanding of the mode of action, as aspects of coordination and collaboration contribute significantly to the benefits of agile methods.
      15
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    Aerographite Solar Sails – Photon Pressure Thrust Measurements of Spacecrafts made from Ultra-Lightweight Materials
    In this project, the high-performance material aerographite is to be investigated in detail for use as a passive solar sail. Due to its unique light-matter interaction properties, aerographite has the potential to far surpass current solar sail technologies. Based on previous experiments, these and other properties will be experimentally investigated and comprehensively understood. The material will be exposed to extreme conditions in a space-like environment with laser and light sources in the solar spectrum and the resulting thrust force will be measured. In the project, a suitable test environment is first created and adjustments are made to the shear measuring balance used. In a large vacuum chamber, an ultra-precise shear measuring balance is used to detect sub-nanonewton shear forces. Laser and light sources are then used to exert a defined photon pressure on the aerographite on the balance in order to characterize its impulse response. For comparison, the generated photons are first captured in a beam trap in order to transfer the entire impulse to the balance without reflections. In this way, a variety of sample geometries with varying material parameters and geometries such as spherical or planar samples with density gradients will be tested to demonstrate the potential of aerographite. Previous experiments indicate another property of the material that would be of great advantage for a solar sail - the residual gases stored in the material can be released by targeted heating and thus generate additional thrust. To this end, the aerographite is to be heated to high temperatures on the thrust measuring scale using heaters in order to evaluate this effect. Taking all the results into account, the optimum solar sail will ultimately be developed.
      37