Putting force laws to the test

Abstract

Force Microscopy In frequency-modulated atomic force microscopy, force is not measured directly. The resonant frequency amplitude and phase of the vibrating cantilever are converted into force through mathematical inversion algorithms. The resolution of this approach now extends to measuring the force between individual atoms, but Sader et al. show that the underlying interatomic forces can also vary rapidly. These conditions can make the inversion of the frequency shifts mathematically ill-posed and lead to unphysical results. They formulate a simple inflection point test of the changes in force with distance of the tip from the surface that ensures that the inversion algorithm problem will yield an accurate force measurement. Nat. Nanotechnol. 13 , 1088 (2018).