Interactive Surfaces

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 every 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. Ph.D. students and physics undergraduate students of Saarland University collaborate in most of our projects.

    Molecular Mechanics of Biomaterials (Dr. Johanna Blass)


    The research area Molecular Mechanics of Biomaterials studies the role of molecular forces in biomaterials to understand and control the mechanisms of bioadhesion and mechanotransduction. As model systems, we use synthetic biomaterials that mimic the natural environment of cells. In active materials, we employ light-activated molecular motors for the mechanical stimulation 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 tethered-particle motion in microfluidic devices.

    Recent publications:

    1. Blass, B. Bozna, M. Albrecht, G. Wenz, R. Bennewitz: Molecular kinetics and cooperative effects in friction and adhesion of fast reversible bonds, Phys.Chem.Chem.Phys. 2019, 21, 17170
    2. Çolak, Bin Li, J. Blass, K. Koynov, A. del Campo, R. Bennewitz: The mechanics of single cross-links which mediate cell attachment at a hydrogel surface, Nanoscale, 2019, 11, 11596
    3. Y. Zheng, M.K.L. Han, R. Zhao, J. Blass, et al., Optoregulated force application to cellular receptors using molecular motors, under review 2021


    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.

    Tactile Perception of Materials

    Nanotribology 9

    The fast development of digital technologies and networks has revolutionized our communication which is now dominated by the visual channel. However, touch and feel are central to our perception of the world and to our well-being. We develop surfaces with defined microstructure and interface energy to create materials with strong haptic appeal and potential for effective tactile signaling. Our psychophysical projects connect contact mechanics, skin friction versus materials, neurophysiology, and perception. We collaborate with dermatologists, neuroscientists, and psychologists.





    Recent publications:

    1. Sahli, A. Prot, A. Wang, M. H. Müser, M. Piovarči, P. Didyk, and R. Bennewitz: Tactile perception of randomly rough surfaces, Sci Rep 2020, 10, 15800
    2. Lyu, N. Özgün, D.J. Kondziela, and R. Bennewitz: Role of Hair Coverage and Sweating for Textile Friction on the Forearm, Tribol Lett 2020, 68, 100_1-9
    3. N. Özgün, D.J. Strauss, R. Bennewitz: Tribology of a Braille Display and EEG Correlates, Tribology Letters (2018) 66:16