Figure 3.
(a and b) Magnitude (a) and phase (b) of the dynamic indentation modulus of cartilage measured with increasing indentation depths, δ0, and, as a result, increasing contact distances, d, for indentation at a single typical location. (c) The peak frequency, fpeak, decreased with increasing contact distance, d. fpeak is plotted as a function of the inverse square of the contact distance, 1/d2, for five sequential increases in d performed at three different locations (each line corresponding to one of the locations). The best-fit linear regression lines between fpeak and 1/d2 (the minimum value of the goodness of fit, R2, was 0.949 for all 16 locations) confirming this relation between fpeak and 1/d2 suggest that poroelasticity is the dominant mechanism in the observed dynamic response at the nanoscale.