Capillary filling kinetics of deionized water in nanochannels with heights of 50–120 nm were studied.

The position of the moving meniscus was proportional to the square root of time, as predicted by the classical LW equation.

The extracted slopes were significantly smaller than the predictions based on the bulk properties.

This unusual behavior at nanoscale was found to be mainly caused by the electro-viscous effect and dynamic contact angle.