Single molecule adhesion and friction of complex molecules

• Applicant: Dr. Bizan Nicolas Balzer
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454622446

In the past molecular adhesion and friction have been studied using different biophysical techniques having high spatial and force resolution. Yet, the understanding of complex molecules still is a challenge. An example for a very complex type of molecules is mucin. Among many other functions, mucins provide extraordinary adhesion and lubrication properties on many different substrates. These properties make mucins very interesting for future biomimetic coatings and lubricants. However, it is still unknown how exactly the different mucin moieties promote adhesion and friction and how they affect the time dependence of these processes at the molecular scale. Here, Atomic Force Microscopy (AFM) based Single Molecule Force Spectroscopy (SMFS) and AFM based imaging, supported by Quartz Crystal Microbalance with dissipation monitoring (QCM-D) and tribology experiments, will be used to determine the interaction strength and dynamics of complex single molecules in different spatial directions, taking the example of mucin. This will deepen the understanding of the adhesion and friction properties of complex molecules such as mucins. First, the loading rate dependent desorption of single native and modified mucin molecules will be studied on different model substrates with varying roughness, hydrophobicity and softness. Second, loading rate dependent lateral pulling and waiting time experiments will be performed. Third, desorption and lateral pulling experiments of single mucin molecules on mucin films will be used to reveal how the behavior of single molecules is transferred to that of mucin layers. QCM-D and tribology experiments will be used to relate single molecule results to macroscopic findings. This combination of techniques will access a wide range of spatial and temporal scales, which are crucial to understand the role of the different mucin moieties for adhesion and friction properties. This paves the way for a better understanding of complex molecules comprising different functional groups, which will optimize the design of future synthetic multifunctional polymers.

• DFG Programme: Research Grants