Drainage kinetics of nanochannels fabricated in water films a few molecules thick on mica at room temperature.

Nanochannels of the order of 20 nm in diameter and forming arrangements that were a few micrometres wide were fabricated on nanometre-thick ice-like deposits on planar mica surfaces at room temperature. Because an atomic force microscopy tip can write lines on ice-like layers covering mica substrates in air that are stable under invariant conditions of humidity and temperature, the water films were modulated with nanochannels. By analysing the shape and morphology of the material removed after channel fabrication for various time intervals, the channel profile was shown to vary with a scale of a tenth of a second. In this configuration (hydrophobic tip and hydrophilic substrate, 65% RH), at the channel top region there were only aggregates of loose flakes formed after the film inscription but no liquid. Apparently, the Kelvin effect is responsible for the nanochannel profile variation with time, but the calculated and measured values of the drainage time constant are at variance by six orders of magnitude. This reduction of the mass transfer is associated with the small dimensions of the ∼ 10 nm-wide channels.