Wicking in Cross-Connected Buried Nanochannels

In this work, wicking is studied in ∼728 nm height cross-connected nanochannels buried under a SiO₂ surface. Pores of diameter ∼2 μm, present at each intersect of nanochannels, allow a water droplet placed on the surface to wick into the channels. Experiments are conducted for two different channel widths/spacings and five different water droplet volumes. Wicking characteristics show the occurrence of wicking-dominant and evaporation-dominant regimes, with each further divided into two subregimes. All experimental data in wicking-dominant regime are in good agreement with two analytical models which can be used to predict the wicking distance evolution in such nanochannels. The analysis shows that wicking is initially governed by surface tension and viscous forces as there is unhindered supply of liquid from the droplet. After this initial phase, hydrodynamic dissipation within the droplet sitting on the top surface dictates wicking inside the channels.