  We report the observation of a transition in the dynamical properties of
water nano-menicus which dramatically change when probed at different time
scales. Using a AFM mode that we name Force Feedback Microscopy, we observe
this change in the simultaneous measurements, at different frequencies, of the
stiffness G'(N/m), the dissipative coefficient G''(kg/sec) together with the
static force. At low frequency we observe a negative stiffness as expected for
capillary forces. As the measuring time approaches the microsecond, the dynamic
response exhibits a transition toward a very large positive stiffness. When
evaporation and condensation gradually lose efficiency, the contact line
progressively becomes immobile. This transition is essentially controlled by
variations of Laplace pressure.
