known as the “tapping” mode. Images of 10 mm 10 mm were
recorded after various durations of exposure in the SEPAP device.
The RMS (root mean square) was determined on zoomed regions of
5 mm 5 mm. The RMS or roughness represents the standard deviation
of the values of the Z-axes for a given surface. The RMS was
obtained via a computer-aided calculation of the entire studied
surface using the following mathematical equation (2):