Instability of nano liquid threads in a saturated or supersaturated vapour environment

Evaporation and condensation have been reported to be able to considerably alter the pinch-off profile of nano liquid threads. However, it is still not well understood how evaporation and condensation will impact the instability of nano liquid threads. In this article, we propose a modified stochastic lubrication equation (MSLE) that incorporates both thermal fluctuations and evaporation–condensation. We conduct stability analysis based on the MSLE and show that the curvature-dependent evaporation tends to enhance the growth of perturbations of small wavenumber but impede those with large wavenumber. For realistic fluids, the effect is actually very small. However, in a supersaturated vapour environment, condensation is dominant. Stability analysis and molecular dynamics simulations both show that the growth of the perturbations is considerably impeded by condensation. The spectrum curves of the perturbations shift to smaller wavenumber and lower magnitude. The effect of condensation becomes very significant on short nano liquid threads whose lengths are around the critical length in Rayleigh’s classic theory. Although condensation is usually a slow process, it can completely alter the stability of short liquid threads, rendering an originally unstable thread stable. Our results open up a new avenue to control the instability of nano liquid threads through environmental vapour pressure.