Directional Energy Transfer in a Coupled Symmetrical Multifrequency Atomic Force Microscope Cantilever

Precise analysis of substance through multifrequency atomic force microscope (MF-AFM) is a major challenge for fundamental research. In this article, a coupled symmetrical MF-AFM cantilever, comprising an imaging unit (IU) and a detecting one with a modal frequency ratio of 1:3, is proposed to achieve high imaging resolution with an imaging-detecting separation design. A consistency between experiment and theory reveals a directional energy transfer mechanism, from the first harmonic of the IU to the third harmonic of both imaging and detecting units (DUs), in the proposed cantilever. Amplitude-based quantitative characterization further indicates that an energy transfer efficiency of 4.4% partially contributes to amplitude increment multiplication by an order of magnitude with the third harmonic of the DU. Through directionally regulating the energy transfer among harmonics, imaging resolution of MF-AFM is expected to increase by about 300% with the increment of the third harmonic amplitude of the DU rising from one order to two orders of magnitude; meanwhile, both frequency-shift multiplication and noise suppression, brought by internal resonance, also help to uplift imaging resolution.

Automated summary

A coupled symmetrical MF-AFM cantilever is proposed to achieve high imaging resolution through regulating the energy transfer among harmonics, while frequency-shift multiplication and noise suppression brought by internal resonance also help to uplift imaging resolution.