  The viscoelastic dynamics of nano-confined water is studied by means of
atomic force microscopy (AFM). We observe a nonlinear viscoelastic behavior
remarkably similar to that widely observed in metastable complex fluids. We
show that the origin of the measured nonlinear viscoelasticity in nano-confined
water is a strain rate dependent relaxation time and slow dynamics. By
measuring the viscoelastic modulus at different frequencies and strains, we
find that the intrinsic relaxation time of nano-confined water is in the range
0.1-0.0001 s, orders of magnitude longer than that of bulk water, and
comparable to the dielectric relaxation time measured in supercooled water at
170-210 K.
