Atomic Force Microscopy (AFM): imaging, friction, KPFM, force spectroscopy
Single Molecule Force Spectroscopy: adhesion and friction mechanisms between single polymers and solid substrates or thin polymer films in solution
Functionalization of solid surfaces and AFM probes
Tribology: friction properties of single molecules, polymer films and biomolecules
SINGLE MOLECULE ADHESION AND FRICTION
A combination of vertical and lateral pulling allows us to determine both the normal force (the adhesion force) and the friction force at the solid-liquid interface for a single polymer. lateral pulling reveals three different friction motifs: slip, desorption stick and cooperative stick.
1. B.N. Balzer, M. Gallei, M. Hauf, M. Stallhofer, L. Wiegleb, A. Holleitner, M. Rehahn & T. Hugel
Nanoscale Friction Mechanisms at Solid–Liquid Interfaces
Angew. Chem. Int. Ed., 52 (25), 6541 (2013). https://doi.org/10.1002/anie.2013012552.
2. B.N. Balzer, S. Kienle, M. Gallei, R. v. Klitzing, M. Rehahn & T. Hugel
Stick-Slip Mechanisms at the Nanoscale
Soft Materials, 12 (1), 106 (2014). https://doi.org/10.1080/1539445X.2014.945039
3. S. Kienle, M. Gallei, H. Yu, B. Zhang, S. Krysiak, B.N. Balzer, M. Rehahn, A.D. Schlüter & T. Hugel
Effect of Molecular Architecture on Single Polymer Adhesion
Langmuir, 30 (15), 4351 (2014). https://doi.org/10.1021/la500783n
Mucins lubricate a large number of different substrates while preventing wear, which makes them good candidates for future substrate coatings and lubricants. Two molecular mechanisms provide this
kind of separation of opposing surfaces: sacrificial layer formation and hydration lubrication. We use the AFM to understand the role of the different mucin moieties for
adhesion and friction properties.
1. M. Marczynski, B.N. Balzer, K. Jiang, T. M. Lutz, T. Crouzier & O. Lieleg
Charged Glycan Residues Critically Contribute to the Adsorption and Lubricity of Mucins
Colloids and Surfaces B: Biointerfaces, 187, 110614 (2020). https://doi.org/10.1016/j.colsurfb.2019.110614
2. B. Winkeljann, K. Boettcher, B.N. Balzer & O. Lieleg
Mucin Coatings Prevent Tissue Damage at the Cornea–Contact Lens Interface
Adv. Mater. Interfaces, 4 (19), 1700186 (2017). https://doi.org/10.1002/admi.201700186
Mechanical energy can be harvested from the environment and converted into electric energy via the triboelectric effect. AFM imaging and Kelvin Probe Force Microscopy are to used to understand the molecular origin of the triboelectric effect.
FUNCTIONALIZATION OF CANTILEVER TIPS
For a true single molecule experiment, covalent attachment of the probe molecule is essential because only then can hundreds of force-extension traces with one and the same single molecule be obtained. We develope functionalization protocols that can easily be applied to a variety of polymers.
A. Kolberg, C. Wenzel, T. Hugel, M. Gallei & B.N. Balzer
Covalent Attachment of Single Molecules for AFM-based Force Spectroscopy
J. Vis. Exp., 157, e60934 (2020). https://doi.org/10.3791/60934
ELASTICITY OF POLYMER FILMS AND BIOLOGICAL TISSUES
We use a combined AFM and fluorescence microscopy approach to correlate the stiffness of cartilage tissues determined by indentation experiments with spatial chondrocyte patterns using flouerescence microscopy exhibiting the earliest identifiable osteoarthritis.
1. M. Tschaikowsky, M. Selig, S. Brander, B.N. Balzer, T. Hugel & B. Rolauffs
Proof-of-concept for the detection of early osteoarthritis pathology by clinically applicable endomicroscopy and quantitative AI-supported optical biopsy
Osteoarthritis and Cartilage, S1063-4584, 20, 31167-5 (2020); https://doi.org/10.1016/j.joca.2020.10.003
2. H. Schafer, A. Kolberg, M. Gockeln, R. Kun, B.N. Balzer & K. Koschek
Influence of free PCL in PCL/PBA-a copolymers and blends on morphology, thermo-mechanical and shape memory properties
Polymer Testing, 77, 105888 (2019). https://doi.org/10.1016/j.polymertesting.2019.05.004
FORCE RESPONSE OF MATERIALS SYSTEMS
We use AFM capbilities to anaylyze the force response of ultraelastic and stimulus responsive protein-based materials systems (structure-function relations). These protein based structures are formed by photocrosslinking using Two Photon Laser Writing obtaining auxetic 3D structures at the scale of a few micrometers.