Single Polymer Friction at Interfaces
Biophysics
Final Report Abstract
Understanding the processes underlying nanoscale friction is essential to design optimized nanoscopic components and to understand the kinetics of biological processes. In the framework of this proposal we developed protocols for AFM-based single polymer pulling experiments that include horizontal pulling and vertical waitingtime experiments. First we found and characterized a single polymer friction mechanism that is largely independent of normal force, polymer length, and velocity. This mechanism contrasts friction models based on Amontons’ law and the Rouse model. We term this mechanism desorption stick. Then we characterized the succession of desorption stick - slip events and find a velocity dependence that resembles macroscopic stick-slip. This opens new horizons for the molecular interpretation of macroscopic stick-slip, which usually is explained by asperities that come in and out of contact. Such an interpretation definitely does not explain desorption stick-slip. In collaboration with Prof. Roland Netz (FU Berlin) we investigated the forced desorption of polytyrosine and polylysine homopeptides from solid substrates. A simultaneous fit of constant-velocity and waiting-time AFM-measurements allowed us to disentangle and determine the model parameters describing this non-equilibrium process. The surprisingly low value for the intrinsic monomeric desorption rate of around 10^5 Hz points to significant cooperativity in the desorption process of single polymers. Friction and lubrication are inherently non-equilibrium processes and often dominated by the periods of stick in between slip events. Therefore, we anticipate that our characterization of single polymer friction and non-equilibrium adhesion will guide the bottom-up development of durable, low-friction surface coatings in polymer-based nanotechnology.
Publications
- Nanoscale Friction Mechanisms at Solid–Liquid Interfaces. Reibungsmechanismen auf der Nanoskala an Fest-flüssig-Grenzflächen. Angew. Chem. Int. Ed. 52,25, 6541 (2013); Angew. Chem. 2013, 125, 6670 (2013)
B. N. Balzer, M. Gallei, M. Hauf, M. Stallhofer, L. Wiegleb, A. Holleitner, M. Rehahn, T. Hugel
- Effect of Molecular Architecture on Single Polymer Adhesion. Langmuir, 30 (15), 4351–4357 (2014)
S. Kienle, M. Gallei, H. Yu, B. Zhang, S. Krysiak, B. N. Balzer, M. Rehahn, A. D. Schlüter, and T. Hugel
(See online at https://doi.org/10.1021/la500783n) - Peptide Desorption Kinetics from Single Molecule Force Spectroscopy Studies. JACS, 136, 688 (2014)
S. Krysiak, S. Liese, R. R. Netz and T. Hugel
(See online at https://doi.org/10.1021/ja410278r) - Investigating Single Molecule Adhesion by Atomic Force Spectroscopy. JoVE, 96, e52456 (2015)
F. Stetter, S. Kienle, S. Krysiak, T. Hugel
(See online at https://doi.org/10.3791/52456)
