Pico-Newton Force Sensing at Liquid-Solid Interfaces by Prof. Dr. Hiroshi Onishi, Kobe University, Japan 10.09.2019, 09:00 h, Physics Department, Leibnizstr. 19, 24118 Kiel, Room 614 Abstract Frequency-modulation atomic force microscopy (FM-AFM) is a promising tool to observe solid topography and also liquid structure at liquid-solid interfaces. The cantilever with a tip is mechanically oscillated. The shift of the resonance frequency, delta-f, represents the force pushing or pulling the tip. Microscopes with a force sensitivity of 10 pN or better in water and organic solvents have been developed and commercialized to date. Using the advanced microscopes, we have examined structured liquids at a number of interfaces including water-CaCO3, Al2O3, SrTiO3, hydrophilic molecular monolayers, organic compounds. The observed delta-f distributions are interpreted with water density distribution through Gibbs free energy perturbed by the solid surface. The force sensitivity of 10 pN is the key for probing force on single liquid molecules. Possible application of Δf mapping to tribology research will also be mentioned.