TEM observation of liquid-gas interfacial instability*

Nanofluidics has drawn significant interest over the past decade due to its unique dynamics. So far, there has been little understanding as to how nanoscale interactions affect fluid behavior. Here, we used transmission electron microscopy to observe water behavior inside a one-dimensional graphene nanochannel with high spatial and temporal resolutions. An ultrathin water film, a residue in the channel after the recession of the meniscus caused by the electron beam irradiation, became unstable and consequently formed ripples along the length of the channel. We explained the results by a theoretical analysis considering the effect of the van der Waals interaction between thin water film and graphene layers. It was found that the interactions could considerably reduce the fastest-growing wavelength as the film became thinner than a few nanometers.