Reconstruction Surface Potential from Atomic Friction Measurements

Liron Agmon, Chemical Engineering, BGU Unviersity, Beer Sheva, Israel
Danny Yosufov, Chemical Engineering, Bgu Unviersity, Beer Sheva, Israel
Juergen Jopp, The Ilze Katz Institute For Nanoscience And Technology, Bgu Unviersity, Beer Sheva, Israel
Ronen Berkovich, Chemical Engineering, Bgu Unviersity, Beer Sheva, Israel

Friction is a phenomenon encountered in everyday life, ranging from the macro- (earthquakes, violin playing, machinery, etc.) to the nano-scales (electronic devices, biological machinery etc.), where two surfaces come into contact and move with respect to each other, resulting with an irreversibly energy dissipation. One of the key features that characterize friction is the underlying interfacial interaction potential. Understanding the role of dissipation energy and surface potential in frictional mechanisms is essential for tribology, nanoscale fabrication, catalysis, adhesion and so on. To get an adequate estimation of the free energy landscape of an experimental system, high quality data is required. This necessity is met in measurements performed with Atomic Force Microscope (AFM). The AFM enables probing nanoscale frictional forces due to its ability to approach the 'single-asperity' level, and measure the dynamical interaction between a cantilever tip and the surface of interest, resulting with atomic stick-slip force pattern. In such experiments, estimation of the surface energy corrugation is typically carried out within the phenomenological framework of the Prandtl-Tomlinson model, which does not provide comprehensive information on the surface potential. Here we face such inverse problem and reconstruct physically meaningful potential maps out of the recorded friction signals by applying a different approach to calculate the surface potential. Through the application of the nonequilibrium work relation, or more specifically, the Jarzynski equality, we can directly reconstruct the underlying interaction potential of the surface combining simulations and AFM measurements. Unlike the previous methodology, the latter is model-free, and enables the calculation of the surface interaction potential directly from the measured force and position time series. Such implementation is beneficial to technological applications as molecular optimization of catalysts, and additionally to micro- and nano-electro-mechanical systems (MEMS and NEMS), where high surface-to-volume ratio amplifies damages and energetic inefficiency caused friction.