AFM Imaging via Nonlinear Control of Self-driven Cantilever Oscillations

The need for investigating the properties of new materials at nanoscale level continuously pushes the development of higher resolution measurement instruments. In this context, a promising dynamic atomic force microscopy setup, where the cantilever gets excited by a nonlinear feedback loop, has been recently introduced. In the first part of the paper the application of this working mode to imaging is experimentally investigated, showing the effectiveness of this novel approach. Furthermore, the presence of a variable saturation in the nonlinear loop is exploited to design a specific algorithm that dynamically adapts the cantilever free oscillation amplitude to sudden variations of the sample profile. In imaging applications this additional control action significantly reduces the tip-sample interaction force yet maintaining high image quality, thus resulting in a suitable setup for better preserving the state of soft and damageable samples such as biological specimens.