Increasing the Q factor in the constant-excitation mode of frequency-modulation atomic force microscopy in liquid

By adding a Q-control electronics to the setup of the constant-excitation mode of the frequency-modulation atomic force microscope, the authors are able to increase the effective Q factor of a self-oscillated cantilever in liquid to values comparable to ambient conditions. During imaging of soft biological samples adsorbed on a mica substrate, the authors observed an increased corrugation of the topography with increased Q factors. This effect is caused by the reduction of tip-sample indentation forces as demonstrated by numerical simulations and an analytical approach.