Fig. 1.

Cantilever calibration procedure. A: spring constant of reference cantilevers (k_r) was determined by hanging lengths of platinum wire from the end of the reference cantilever (F = force applied to the cantilever) and measuring cantilever deflection (d_r). Image is shown with an overlay of the original cantilever position. B: spring constant of the measurement cantilever was determined by displacing the reference cantilever relative to the measurement cantilever and measuring the displacement of the reference and measurement cantilevers (x_r and x_m, respectively). Measurement cantilever stiffness is calculated from the slope of the relative deflection plot and the known reference cantilever stiffness.