Our research group studies the nanomechanical properties of materials. In particular, we aim to understand microscopic mechanisms of friction and wear through dedicated experiments and to contribute to the design of new tribological materials. High-resolution force microscopy (AFM) is our most important method. In AFM, an extremely fine tip is scanned over the material surface. The microscope is sensitive enough to detect the friction force of each single molecular bond broken. Furthermore, we develop novel experimental methods in order to contribute to the understanding of the complex world of friction. Materials under investigation include metals and metallic glasses, micro-structured and fiber reinforced polymers, macromolecular surface functionalization, and novel lubricants. PhD students and physics undergraduate students of Saarland University collaborate in most of our projects.
The nanotribology group investigates the molecular mechanisms of friction, lubrication, and wear. We build on our expertise in high-resolution friction force microscopy and in the preparation of novel surface materials.
Two-dimensional materials such as graphene or MoS2 are spectacular lubricants. We study atomic friction processes on these materials under vacuum conditions and explore the limits of their mechanical stability. The project is supported by the DFG within the priority program “2D Materials – Physics of van der Waals [hetero]structures (2DMP)” (SPP 2244).
The chemical structure of surfaces is a key parameter in friction. It can be controlled by electrochemical methods. We investigate the switching of friction and wear in experiments with scanning force microscopy in an electrochemical cell. Our materials focus is currently on metallic glasses.
The efficiency of liquid lubricants depends critically on their properties under high pressure in the gap of a sliding contact. We study the molecular structure of the confined lubricants, in particular ionic liquids, and determine the shear viscosity of the nanometer-thick films.
Our research group studies the role of mechanical forces in biomaterials to understand and control the molecular mechanisms of bioadhesion and mechanotransduction. As a model system, we use synthetic biomaterials that mimic the natural environment of cells. We study the mechanical properties of biomimetic hydrogels on the molecular scale by pulling on the molecular network with the sharp tip of an atomic force microscope. Moreover, we use DNA-origami constructs as a powerful platform to design new biomaterials with force-sensing functions. For rapid force measurements on the single-molecular level, we develop novel high-throughput techniques based on microfluidic devices.
The haptic perception of materials is an emerging interdisciplinary field of research with many applications in robotics, human-machine interfaces, or textile design. Starting from materials with well-defined surface structure we explore the materials parameters which are relevant for haptic perception in psychophysical experiments. We are particularly interested in the role of skin friction in contact with, for example, microfibrils or 3D-printed surfaces with random roughness. EEG recordings report neural correlates to fingertip friction.