Friction and wear minimizing coatings are crucial for applications in combustion engines and medical implants. Their performance is typically limited by mechanical failure especially due to local overload. In this work, the contact damage creation, evolution, and final morphology of hydrogenated diamond-like carbon (DLC)coated titanium (Ti) substrates are investigated. The influence of the DLC film thickness and the elastic-plastic deformation of the Ti on the contact damage are studied by microindentation and static finite-element analysis. Film thickness, indenter radius, and applied load as well as the elastic-plastic deformation of the Ti are shown to significantly affect contact damage. A failure plot is presented with the location of first failure in the DLC and compared to the experimental observation. In addition, a case study with variable fracture toughness of the DLC and its influence on the failure plot is shown. The stress distribution in the DLC follows a transition from a membrane-like to a plate-like deformation behavior upon increasing the DLC film thickness. Thin DLC films reveal increased cracking in the inner zone of the indent, while thicker DLC films reveal pronounced edge cracking. These edge cracks were correlated to pop-ins in force-displacement curves upon microindentation. Finally, a film thickness optimization process is presented for hard and brittle films on soft and ductile metallic substrates. D. Bernoulli and A. Wyss have contributed equally to the work and are therefore shared first-authors.

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Label-free biosensors based on in situ formed and functionalized TTF-Au wires were developed using an integrated microfluidic system. By applying different modification protocols, TTF-Au wires were successfully used for sensitive label-free detection of catecholamines and human IgG by Raman spectroscopy.

In this work the calibration of the directional Raman strain shift coefficient for tensile strained Ge microstructures is reported. The strain shift coefficient is retrieved from micro-Raman spectroscopy measurements in combination with absolute strain measurements from x-ray diffraction using focused synchrotron radiation. The results are used to fit the phonon deformation potentials. A linear dependence of the phonon deformation potentials p and q is revealed. The method can be extended to provide strain calibration of Raman experiments also in other material system.