Background: Dynamic atomic force microscopy has become a powerful tool for the nanoscale imaging of biological samples.In solution

the cantilever oscillation parameters such as quality factor and frequency response are critical for stable imaging and precise measurements.The commonly driving cantilever method is acoustical-piezoelectrical approach.However

this indirect excitation mechanism will induce many spurious resonance peaks due to the hydrodynamic interaction between the fluid cell and the liquid in solution

which produce an unstable oscillation of the cantilever.Purpose: Drive the cantilever in a direct way to obtain a well controlled oscillation.Methods: Several direct driving techniques have been successfully developed such as magnetic

electrostatic

acoustical and photothermal excitations.Results: There is a single resonance peak in the cantilever oscillation spectrum under liquid environment with these direct driving methods.Conclusions: Several methods can directly drive the cantilever including magnetic

electrostatic

acoustical and photothermal excitations.The amplitude and frequency response with these different methods is compared.