Figure 3.

Visualization of wetout in strips with dyed dry sugar showing rapid dissolution and formation of viscous fingers. Sugar solution (ϕ=10%) with added dye was applied to strips and dried, and buffer with no dye was wicked into the strips. A) The dried sugar was rapidly dissolved by the advancing fluid, leading to sugar-rich leading region and a relatively sugar-free trailing region. B) and C) images at different time points showing propagation of viscous fingers. An obvious feature of the fingers is that they coalesce over time.