In the last three decades, surface nanoscale properties have been intensely investigated by use of atomic force microscopy (AFM). In particular, non-contact atomic force microscopy (nc-AFM) has exhibited remarkable performance in high-resolution surface imaging of various exotic materials in vacuum, air, and water with no or less damage to their surfaces1. Therein, the shift (∆f) of cantilever resonant frequency (f) induced by the interaction between a tip and the sample, deviated from f0 at free, is measured and used as a feedback signal to control the tip–sample distance;the topography along with various static and dynamic properties of the surfaces can be depicted. The interaction forces are categorized into conservative and nonconservative forces. The nonconservative forces cause energy dissipation, which is neither fully understood nor utilized, but still attracts much interest as a fascinating measurable physical quantity.
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