Time evolution of actual drop wicking on stainless steel structure B (middle structure). The bottom of the structure appears as white and the top is dark. Each structure is 24 mm long. Water is colored for better visibility. Times are in seconds. The first picture shows the pipette that places a water drop on structure B at time t₀. At time t₁ the drop has already begun to wick through the channels. At time t₂, the structure has been completely flooded in x directionwhile wicking is still progressing in the opposite direction. Transport in − x direction is completed at time t₃ only: slower wicking is observed in this direction.