A control-based approach is provided for achieving accurate indentation quantification in broadband and in-liquid nanomechanical property measurements using atomic force microscope (AFM). Accurate indentation measurement is desirable for probe-based material property characterization because the force applied and the indentation generated are the fundamental physical variables that are measured in the characterization process. Large measurement errors, however, occur when the measurement frequency range becomes large (i.e., broadband), or the indentation is measured in liquid on soft materials. Such large measurement errors are generated due to the inability of the conventional method to account for the convolution of the instrument dynamics with the viscoelastic response of the soft sample when the measurement frequency becomes large, and the random-like thermal drift and the distributive hydrodynamic force effects when measuring the indentation in liquid.